CINXE.COM

<!DOCTYPE html> <html class="client-nojs vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-sticky-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-toc-available" lang="en" dir="ltr"> <head> <meta charset="UTF-8"> <title>Planetary habitability - Wikipedia</title> <script>(function(){var className="client-js vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-sticky-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-toc-available";var cookie=document.cookie.match(/(?:^|; )enwikimwclientpreferences=([^;]+)/);if(cookie){cookie[1].split('%2C').forEach(function(pref){className=className.replace(new RegExp('(^| )'+pref.replace(/-clientpref-\w+$|[^\w-]+/g,'')+'-clientpref-\\w+( |$)'),'$1'+pref+'$2');});}document.documentElement.className=className;}());RLCONF={"wgBreakFrames":false,"wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy", "wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgRequestId":"78e6a1bd-7a09-45ab-81b2-e5803476e0e3","wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"Planetary_habitability","wgTitle":"Planetary habitability","wgCurRevisionId":1259831068,"wgRevisionId":1259831068,"wgArticleId":2592906,"wgIsArticle":true,"wgIsRedirect":false,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":["CS1 maint: multiple names: authors list","CS1 maint: unfit URL","Articles with short description","Short description is different from Wikidata","Use dmy dates from May 2022","All articles needing additional references","Articles needing additional references from December 2020","All articles with specifically marked weasel-worded phrases","Articles with specifically marked weasel-worded phrases from April 2024", "Pages displaying short descriptions of redirect targets via Module:Annotated link","Articles with hAudio microformats","Spoken articles","Planetary habitability","Astrobiology","Space colonization","Exoplanetology","Prebiotic chemistry"],"wgPageViewLanguage":"en","wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgRelevantPageName":"Planetary_habitability","wgRelevantArticleId":2592906,"wgIsProbablyEditable":true,"wgRelevantPageIsProbablyEditable":true,"wgRestrictionEdit":[],"wgRestrictionMove":["sysop"],"wgNoticeProject":"wikipedia","wgCiteReferencePreviewsActive":false,"wgFlaggedRevsParams":{"tags":{"status":{"levels":1}}},"wgMediaViewerOnClick":true,"wgMediaViewerEnabledByDefault":true,"wgPopupsFlags":0,"wgVisualEditor":{"pageLanguageCode":"en","pageLanguageDir":"ltr","pageVariantFallbacks":"en"},"wgMFDisplayWikibaseDescriptions":{"search":true,"watchlist":true,"tagline":false,"nearby":true},"wgWMESchemaEditAttemptStepOversample":false,"wgWMEPageLength":100000, "wgRelatedArticlesCompat":[],"wgCentralAuthMobileDomain":false,"wgEditSubmitButtonLabelPublish":true,"wgULSPosition":"interlanguage","wgULSisCompactLinksEnabled":false,"wgVector2022LanguageInHeader":true,"wgULSisLanguageSelectorEmpty":false,"wgWikibaseItemId":"Q846030","wgCheckUserClientHintsHeadersJsApi":["brands","architecture","bitness","fullVersionList","mobile","model","platform","platformVersion"],"GEHomepageSuggestedEditsEnableTopics":true,"wgGETopicsMatchModeEnabled":false,"wgGEStructuredTaskRejectionReasonTextInputEnabled":false,"wgGELevelingUpEnabledForUser":false};RLSTATE={"ext.globalCssJs.user.styles":"ready","site.styles":"ready","user.styles":"ready","ext.globalCssJs.user":"ready","user":"ready","user.options":"loading","ext.cite.styles":"ready","ext.tmh.player.styles":"ready","skins.vector.search.codex.styles":"ready","skins.vector.styles":"ready","skins.vector.icons":"ready","jquery.makeCollapsible.styles":"ready","ext.wikimediamessages.styles":"ready", "ext.visualEditor.desktopArticleTarget.noscript":"ready","ext.uls.interlanguage":"ready","wikibase.client.init":"ready","ext.wikimediaBadges":"ready"};RLPAGEMODULES=["ext.cite.ux-enhancements","mediawiki.page.media","ext.tmh.player","site","mediawiki.page.ready","jquery.makeCollapsible","mediawiki.toc","skins.vector.js","ext.centralNotice.geoIP","ext.centralNotice.startUp","ext.gadget.ReferenceTooltips","ext.gadget.switcher","ext.urlShortener.toolbar","ext.centralauth.centralautologin","mmv.bootstrap","ext.popups","ext.visualEditor.desktopArticleTarget.init","ext.visualEditor.targetLoader","ext.echo.centralauth","ext.eventLogging","ext.wikimediaEvents","ext.navigationTiming","ext.uls.interface","ext.cx.eventlogging.campaigns","ext.cx.uls.quick.actions","wikibase.client.vector-2022","ext.checkUser.clientHints","ext.quicksurveys.init","ext.growthExperiments.SuggestedEditSession","wikibase.sidebar.tracking"];</script> <script>(RLQ=window.RLQ||[]).push(function(){mw.loader.impl(function(){return["user.options@12s5i",function($,jQuery,require,module){mw.user.tokens.set({"patrolToken":"+\\","watchToken":"+\\","csrfToken":"+\\"}); }];});});</script> <link rel="stylesheet" href="/w/load.php?lang=en&modules=ext.cite.styles%7Cext.tmh.player.styles%7Cext.uls.interlanguage%7Cext.visualEditor.desktopArticleTarget.noscript%7Cext.wikimediaBadges%7Cext.wikimediamessages.styles%7Cjquery.makeCollapsible.styles%7Cskins.vector.icons%2Cstyles%7Cskins.vector.search.codex.styles%7Cwikibase.client.init&only=styles&skin=vector-2022"> <script async="" src="/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector-2022"></script> <meta name="ResourceLoaderDynamicStyles" content=""> <link rel="stylesheet" href="/w/load.php?lang=en&modules=site.styles&only=styles&skin=vector-2022"> <meta name="generator" content="MediaWiki 1.44.0-wmf.4"> <meta name="referrer" content="origin"> <meta name="referrer" content="origin-when-cross-origin"> <meta name="robots" content="max-image-preview:standard"> <meta name="format-detection" content="telephone=no"> <meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/The_Blue_Marble_%28remastered%29.jpg/1200px-The_Blue_Marble_%28remastered%29.jpg"> <meta property="og:image:width" content="1200"> <meta property="og:image:height" content="1200"> <meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/The_Blue_Marble_%28remastered%29.jpg/800px-The_Blue_Marble_%28remastered%29.jpg"> <meta property="og:image:width" content="800"> <meta property="og:image:height" content="800"> <meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/The_Blue_Marble_%28remastered%29.jpg/640px-The_Blue_Marble_%28remastered%29.jpg"> <meta property="og:image:width" content="640"> <meta property="og:image:height" content="640"> <meta name="viewport" content="width=1120"> <meta property="og:title" content="Planetary habitability - Wikipedia"> <meta property="og:type" content="website"> <link rel="preconnect" href="//upload.wikimedia.org"> <link rel="alternate" media="only screen and (max-width: 640px)" href="//en.m.wikipedia.org/wiki/Planetary_habitability"> <link rel="alternate" type="application/x-wiki" title="Edit this page" href="/w/index.php?title=Planetary_habitability&action=edit"> <link rel="apple-touch-icon" href="/static/apple-touch/wikipedia.png"> <link rel="icon" href="/static/favicon/wikipedia.ico"> <link rel="search" type="application/opensearchdescription+xml" href="/w/rest.php/v1/search" title="Wikipedia (en)"> <link rel="EditURI" type="application/rsd+xml" href="//en.wikipedia.org/w/api.php?action=rsd"> <link rel="canonical" href="https://en.wikipedia.org/wiki/Planetary_habitability"> <link rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en"> <link rel="alternate" type="application/atom+xml" title="Wikipedia Atom feed" href="/w/index.php?title=Special:RecentChanges&feed=atom"> <link rel="dns-prefetch" href="//meta.wikimedia.org" /> <link rel="dns-prefetch" href="//login.wikimedia.org"> </head> <body class="skin--responsive skin-vector skin-vector-search-vue mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject mw-editable page-Planetary_habitability rootpage-Planetary_habitability skin-vector-2022 action-view"><a class="mw-jump-link" href="#bodyContent">Jump to content</a> <div class="vector-header-container"> <header class="vector-header mw-header"> <div class="vector-header-start"> <nav class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-dropdown" class="vector-dropdown vector-main-menu-dropdown vector-button-flush-left vector-button-flush-right" > <input type="checkbox" id="vector-main-menu-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-main-menu-dropdown" class="vector-dropdown-checkbox " aria-label="Main menu" > <label id="vector-main-menu-dropdown-label" for="vector-main-menu-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-menu mw-ui-icon-wikimedia-menu"></span> <span class="vector-dropdown-label-text">Main menu</span> </label> <div class="vector-dropdown-content"> <div id="vector-main-menu-unpinned-container" class="vector-unpinned-container"> <div id="vector-main-menu" class="vector-main-menu vector-pinnable-element"> <div class="vector-pinnable-header vector-main-menu-pinnable-header vector-pinnable-header-unpinned" data-feature-name="main-menu-pinned" data-pinnable-element-id="vector-main-menu" data-pinned-container-id="vector-main-menu-pinned-container" data-unpinned-container-id="vector-main-menu-unpinned-container" > <div class="vector-pinnable-header-label">Main menu</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-main-menu.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-main-menu.unpin">hide</button> </div> <div id="p-navigation" class="vector-menu mw-portlet mw-portlet-navigation" > <div class="vector-menu-heading"> Navigation </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-mainpage-description" class="mw-list-item"><a href="/wiki/Main_Page" title="Visit the main page [z]" accesskey="z"><span>Main page</span></a></li><li id="n-contents" class="mw-list-item"><a href="/wiki/Wikipedia:Contents" title="Guides to browsing Wikipedia"><span>Contents</span></a></li><li id="n-currentevents" class="mw-list-item"><a href="/wiki/Portal:Current_events" title="Articles related to current events"><span>Current events</span></a></li><li id="n-randompage" class="mw-list-item"><a href="/wiki/Special:Random" title="Visit a randomly selected article [x]" accesskey="x"><span>Random article</span></a></li><li id="n-aboutsite" class="mw-list-item"><a href="/wiki/Wikipedia:About" title="Learn about Wikipedia and how it works"><span>About Wikipedia</span></a></li><li id="n-contactpage" class="mw-list-item"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us" title="How to contact Wikipedia"><span>Contact us</span></a></li> </ul> </div> </div> <div id="p-interaction" class="vector-menu mw-portlet mw-portlet-interaction" > <div class="vector-menu-heading"> Contribute </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-help" class="mw-list-item"><a href="/wiki/Help:Contents" title="Guidance on how to use and edit Wikipedia"><span>Help</span></a></li><li id="n-introduction" class="mw-list-item"><a href="/wiki/Help:Introduction" title="Learn how to edit Wikipedia"><span>Learn to edit</span></a></li><li id="n-portal" class="mw-list-item"><a href="/wiki/Wikipedia:Community_portal" title="The hub for editors"><span>Community portal</span></a></li><li id="n-recentchanges" class="mw-list-item"><a href="/wiki/Special:RecentChanges" title="A list of recent changes to Wikipedia [r]" accesskey="r"><span>Recent changes</span></a></li><li id="n-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_upload_wizard" title="Add images or other media for use on Wikipedia"><span>Upload file</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> <a href="/wiki/Main_Page" class="mw-logo"> <img class="mw-logo-icon" src="/static/images/icons/wikipedia.png" alt="" aria-hidden="true" height="50" width="50"> <span class="mw-logo-container skin-invert"> <img class="mw-logo-wordmark" alt="Wikipedia" src="/static/images/mobile/copyright/wikipedia-wordmark-en.svg" style="width: 7.5em; height: 1.125em;"> <img class="mw-logo-tagline" alt="The Free Encyclopedia" src="/static/images/mobile/copyright/wikipedia-tagline-en.svg" width="117" height="13" style="width: 7.3125em; height: 0.8125em;"> </span> </a> </div> <div class="vector-header-end"> <div id="p-search" role="search" class="vector-search-box-vue vector-search-box-collapses vector-search-box-show-thumbnail vector-search-box-auto-expand-width vector-search-box"> <a href="/wiki/Special:Search" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only search-toggle" title="Search Wikipedia [f]" accesskey="f"><span class="vector-icon mw-ui-icon-search mw-ui-icon-wikimedia-search"></span> <span>Search</span> </a> <div class="vector-typeahead-search-container"> <div class="cdx-typeahead-search cdx-typeahead-search--show-thumbnail cdx-typeahead-search--auto-expand-width"> <form action="/w/index.php" id="searchform" class="cdx-search-input cdx-search-input--has-end-button"> <div id="simpleSearch" class="cdx-search-input__input-wrapper" data-search-loc="header-moved"> <div class="cdx-text-input cdx-text-input--has-start-icon"> <input class="cdx-text-input__input" type="search" name="search" placeholder="Search Wikipedia" aria-label="Search Wikipedia" autocapitalize="sentences" title="Search Wikipedia [f]" accesskey="f" id="searchInput" > <span class="cdx-text-input__icon cdx-text-input__start-icon"></span> </div> <input type="hidden" name="title" value="Special:Search"> </div> <button class="cdx-button cdx-search-input__end-button">Search</button> </form> </div> </div> </div> <nav class="vector-user-links vector-user-links-wide" aria-label="Personal tools"> <div class="vector-user-links-main"> <div id="p-vector-user-menu-preferences" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-userpage" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-dropdown" class="vector-dropdown " title="Change the appearance of the page's font size, width, and color" > <input type="checkbox" id="vector-appearance-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-appearance-dropdown" class="vector-dropdown-checkbox " aria-label="Appearance" > <label id="vector-appearance-dropdown-label" for="vector-appearance-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-appearance mw-ui-icon-wikimedia-appearance"></span> <span class="vector-dropdown-label-text">Appearance</span> </label> <div class="vector-dropdown-content"> <div id="vector-appearance-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div id="p-vector-user-menu-notifications" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-overflow" class="vector-menu mw-portlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en" class=""><span>Donate</span></a> </li> <li id="pt-createaccount-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:CreateAccount&returnto=Planetary+habitability" title="You are encouraged to create an account and log in; however, it is not mandatory" class=""><span>Create account</span></a> </li> <li id="pt-login-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:UserLogin&returnto=Planetary+habitability" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o" class=""><span>Log in</span></a> </li> </ul> </div> </div> </div> <div id="vector-user-links-dropdown" class="vector-dropdown vector-user-menu vector-button-flush-right vector-user-menu-logged-out" title="Log in and more options" > <input type="checkbox" id="vector-user-links-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-user-links-dropdown" class="vector-dropdown-checkbox " aria-label="Personal tools" > <label id="vector-user-links-dropdown-label" for="vector-user-links-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-ellipsis mw-ui-icon-wikimedia-ellipsis"></span> <span class="vector-dropdown-label-text">Personal tools</span> </label> <div class="vector-dropdown-content"> <div id="p-personal" class="vector-menu mw-portlet mw-portlet-personal user-links-collapsible-item" title="User menu" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport" class="user-links-collapsible-item mw-list-item"><a href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en"><span>Donate</span></a></li><li id="pt-createaccount" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:CreateAccount&returnto=Planetary+habitability" title="You are encouraged to create an account and log in; however, it is not mandatory"><span class="vector-icon mw-ui-icon-userAdd mw-ui-icon-wikimedia-userAdd"></span> <span>Create account</span></a></li><li id="pt-login" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:UserLogin&returnto=Planetary+habitability" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o"><span class="vector-icon mw-ui-icon-logIn mw-ui-icon-wikimedia-logIn"></span> <span>Log in</span></a></li> </ul> </div> </div> <div id="p-user-menu-anon-editor" class="vector-menu mw-portlet mw-portlet-user-menu-anon-editor" > <div class="vector-menu-heading"> Pages for logged out editors <a href="/wiki/Help:Introduction" aria-label="Learn more about editing"><span>learn more</span></a> </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-anoncontribs" class="mw-list-item"><a href="/wiki/Special:MyContributions" title="A list of edits made from this IP address [y]" accesskey="y"><span>Contributions</span></a></li><li id="pt-anontalk" class="mw-list-item"><a href="/wiki/Special:MyTalk" title="Discussion about edits from this IP address [n]" accesskey="n"><span>Talk</span></a></li> </ul> </div> </div> </div> </div> </nav> </div> </header> </div> <div class="mw-page-container"> <div class="mw-page-container-inner"> <div class="vector-sitenotice-container"> <div id="siteNotice"></div> </div> <div class="vector-column-start"> <div class="vector-main-menu-container"> <div id="mw-navigation"> <nav id="mw-panel" class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-pinned-container" class="vector-pinned-container"> </div> </nav> </div> </div> <div class="vector-sticky-pinned-container"> <nav id="mw-panel-toc" aria-label="Contents" data-event-name="ui.sidebar-toc" class="mw-table-of-contents-container vector-toc-landmark"> <div id="vector-toc-pinned-container" class="vector-pinned-container"> <div id="vector-toc" class="vector-toc vector-pinnable-element"> <div class="vector-pinnable-header vector-toc-pinnable-header vector-pinnable-header-pinned" data-feature-name="toc-pinned" data-pinnable-element-id="vector-toc" > <h2 class="vector-pinnable-header-label">Contents</h2> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-Background" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Background"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Background</span> </div> </a> <ul id="toc-Background-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Stellar_characteristics" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Stellar_characteristics"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Stellar characteristics</span> </div> </a> <button aria-controls="toc-Stellar_characteristics-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Stellar characteristics subsection</span> </button> <ul id="toc-Stellar_characteristics-sublist" class="vector-toc-list"> <li id="toc-Spectral_class" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Spectral_class"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Spectral class</span> </div> </a> <ul id="toc-Spectral_class-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Stable_habitable_zone" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Stable_habitable_zone"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>Stable habitable zone</span> </div> </a> <ul id="toc-Stable_habitable_zone-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Low_stellar_variation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Low_stellar_variation"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.3</span> <span>Low stellar variation</span> </div> </a> <ul id="toc-Low_stellar_variation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-High_metallicity" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#High_metallicity"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4</span> <span>High metallicity</span> </div> </a> <ul id="toc-High_metallicity-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Planetary_characteristics" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Planetary_characteristics"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Planetary characteristics</span> </div> </a> <button aria-controls="toc-Planetary_characteristics-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Planetary characteristics subsection</span> </button> <ul id="toc-Planetary_characteristics-sublist" class="vector-toc-list"> <li id="toc-Mass_and_size" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Mass_and_size"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Mass and size</span> </div> </a> <ul id="toc-Mass_and_size-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Orbit_and_rotation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Orbit_and_rotation"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Orbit and rotation</span> </div> </a> <ul id="toc-Orbit_and_rotation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Geology" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Geology"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Geology</span> </div> </a> <ul id="toc-Geology-sublist" class="vector-toc-list"> <li id="toc-Geochemistry" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Geochemistry"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3.1</span> <span>Geochemistry</span> </div> </a> <ul id="toc-Geochemistry-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Microenvironments_and_extremophiles" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Microenvironments_and_extremophiles"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.4</span> <span>Microenvironments and extremophiles</span> </div> </a> <ul id="toc-Microenvironments_and_extremophiles-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Ecological_factors" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Ecological_factors"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.5</span> <span>Ecological factors</span> </div> </a> <ul id="toc-Ecological_factors-sublist" class="vector-toc-list"> <li id="toc-Classification_terminology" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Classification_terminology"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.5.1</span> <span>Classification terminology</span> </div> </a> <ul id="toc-Classification_terminology-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> </ul> </li> <li id="toc-Alternative_star_systems" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Alternative_star_systems"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Alternative star systems</span> </div> </a> <button aria-controls="toc-Alternative_star_systems-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Alternative star systems subsection</span> </button> <ul id="toc-Alternative_star_systems-sublist" class="vector-toc-list"> <li id="toc-Binary_systems" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Binary_systems"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Binary systems</span> </div> </a> <ul id="toc-Binary_systems-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Red_dwarf_systems" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Red_dwarf_systems"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.2</span> <span>Red dwarf systems</span> </div> </a> <ul id="toc-Red_dwarf_systems-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Size" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Size"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.3</span> <span>Size</span> </div> </a> <ul id="toc-Size-sublist" class="vector-toc-list"> <li id="toc-Other_factors_limiting_habitability" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Other_factors_limiting_habitability"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.3.1</span> <span>Other factors limiting habitability</span> </div> </a> <ul id="toc-Other_factors_limiting_habitability-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Longevity_and_ubiquity" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Longevity_and_ubiquity"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.3.2</span> <span>Longevity and ubiquity</span> </div> </a> <ul id="toc-Longevity_and_ubiquity-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Massive_stars" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Massive_stars"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.4</span> <span>Massive stars</span> </div> </a> <ul id="toc-Massive_stars-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Neutron_stars" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Neutron_stars"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.5</span> <span>Neutron stars</span> </div> </a> <ul id="toc-Neutron_stars-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Post-main_sequence_stars" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Post-main_sequence_stars"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.6</span> <span>Post-main sequence stars</span> </div> </a> <ul id="toc-Post-main_sequence_stars-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Four_classes_of_habitable_planets_based_on_water" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Four_classes_of_habitable_planets_based_on_water"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Four classes of habitable planets based on water</span> </div> </a> <ul id="toc-Four_classes_of_habitable_planets_based_on_water-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-The_galactic_neighborhood" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#The_galactic_neighborhood"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>The galactic neighborhood</span> </div> </a> <ul id="toc-The_galactic_neighborhood-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Other_considerations" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Other_considerations"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Other considerations</span> </div> </a> <button aria-controls="toc-Other_considerations-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Other considerations subsection</span> </button> <ul id="toc-Other_considerations-sublist" class="vector-toc-list"> <li id="toc-Alternative_biochemistries" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Alternative_biochemistries"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.1</span> <span>Alternative biochemistries</span> </div> </a> <ul id="toc-Alternative_biochemistries-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-"Good_Jupiters"" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#"Good_Jupiters""> <div class="vector-toc-text"> <span class="vector-toc-numb">7.2</span> <span>"Good Jupiters"</span> </div> </a> <ul id="toc-"Good_Jupiters"-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Life's_impact_on_habitability" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Life's_impact_on_habitability"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.3</span> <span>Life's impact on habitability</span> </div> </a> <ul id="toc-Life's_impact_on_habitability-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-The_role_of_chance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#The_role_of_chance"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.4</span> <span>The role of chance</span> </div> </a> <ul id="toc-The_role_of_chance-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Notes" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Notes"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>Notes</span> </div> </a> <ul id="toc-Notes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Bibliography" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Bibliography"> <div class="vector-toc-text"> <span class="vector-toc-numb">11</span> <span>Bibliography</span> </div> </a> <ul id="toc-Bibliography-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> <span class="vector-toc-numb">12</span> <span>Further reading</span> </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">13</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Planetary habitability</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 35 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-35" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">35 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Planet%C3%AAre_bewoonbaarheid" title="Planetêre bewoonbaarheid – Afrikaans" lang="af" hreflang="af" data-title="Planetêre bewoonbaarheid" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%82%D8%A7%D8%A8%D9%84%D9%8A%D8%A9_%D8%B3%D9%83%D9%86_%D8%A7%D9%84%D9%83%D9%88%D8%A7%D9%83%D8%A8" title="قابلية سكن الكواكب – Arabic" lang="ar" hreflang="ar" data-title="قابلية سكن الكواكب" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Habitabilitat_planet%C3%A0ria" title="Habitabilitat planetària – Catalan" lang="ca" hreflang="ca" data-title="Habitabilitat planetària" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Planet%C3%A1rn%C3%AD_habitabilita" title="Planetární habitabilita – Czech" lang="cs" hreflang="cs" data-title="Planetární habitabilita" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Habitable_Zone" title="Habitable Zone – German" lang="de" hreflang="de" data-title="Habitable Zone" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-el badge-Q17437796 badge-featuredarticle mw-list-item" title="featured article badge"><a href="https://el.wikipedia.org/wiki/%CE%A0%CE%BB%CE%B1%CE%BD%CE%B7%CF%84%CE%B9%CE%BA%CE%AE_%CE%BA%CE%B1%CF%84%CE%BF%CE%B9%CE%BA%CE%B7%CF%83%CE%B9%CE%BC%CF%8C%CF%84%CE%B7%CF%84%CE%B1" title="Πλανητική κατοικησιμότητα – Greek" lang="el" hreflang="el" data-title="Πλανητική κατοικησιμότητα" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es badge-Q17437796 badge-featuredarticle mw-list-item" title="featured article badge"><a href="https://es.wikipedia.org/wiki/Habitabilidad_planetaria" title="Habitabilidad planetaria – Spanish" lang="es" hreflang="es" data-title="Habitabilidad planetaria" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Planeda_lo%C4%9Debleco" title="Planeda loĝebleco – Esperanto" lang="eo" hreflang="eo" data-title="Planeda loĝebleco" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu badge-Q17437796 badge-featuredarticle mw-list-item" title="featured article badge"><a href="https://eu.wikipedia.org/wiki/Bizigarritasun_planetario" title="Bizigarritasun planetario – Basque" lang="eu" hreflang="eu" data-title="Bizigarritasun planetario" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%B2%DB%8C%D8%B3%D8%AA%E2%80%8C%D9%BE%D8%B0%DB%8C%D8%B1%DB%8C_%D8%B3%DB%8C%D8%A7%D8%B1%D9%87%E2%80%8C%D8%A7%DB%8C" title="زیست‌پذیری سیاره‌ای – Persian" lang="fa" hreflang="fa" data-title="زیست‌پذیری سیاره‌ای" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Habitabilit%C3%A9_d%27une_plan%C3%A8te" title="Habitabilité d'une planète – French" lang="fr" hreflang="fr" data-title="Habitabilité d'une planète" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Habitabilidade_planetaria" title="Habitabilidade planetaria – Galician" lang="gl" hreflang="gl" data-title="Habitabilidade planetaria" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%ED%96%89%EC%84%B1_%EA%B1%B0%EC%A3%BC%EA%B0%80%EB%8A%A5%EC%84%B1" title="행성 거주가능성 – Korean" lang="ko" hreflang="ko" data-title="행성 거주가능성" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Kelayakhunian_planet" title="Kelayakhunian planet – Indonesian" lang="id" hreflang="id" data-title="Kelayakhunian planet" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Abitabilit%C3%A0_planetaria" title="Abitabilità planetaria – Italian" lang="it" hreflang="it" data-title="Abitabilità planetaria" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%9E%E1%83%9A%E1%83%90%E1%83%9C%E1%83%94%E1%83%A2%E1%83%98%E1%83%A1_%E1%83%A1%E1%83%98%E1%83%AA%E1%83%9D%E1%83%AA%E1%83%AE%E1%83%9A%E1%83%98%E1%83%A1%E1%83%A3%E1%83%9C%E1%83%90%E1%83%A0%E1%83%98%E1%83%90%E1%83%9C%E1%83%9D%E1%83%91%E1%83%90" title="პლანეტის სიცოცხლისუნარიანობა – Georgian" lang="ka" hreflang="ka" data-title="პლანეტის სიცოცხლისუნარიანობა" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Plan%C4%93tu_apdz%C4%ABvojam%C4%ABba" title="Planētu apdzīvojamība – Latvian" lang="lv" hreflang="lv" data-title="Planētu apdzīvojamība" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Kebolehdiaman_planet" title="Kebolehdiaman planet – Malay" lang="ms" hreflang="ms" data-title="Kebolehdiaman planet" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-mn mw-list-item"><a href="https://mn.wikipedia.org/wiki/%D0%93%D0%B0%D1%80%D0%B8%D0%B3%D0%B8%D0%B9%D0%BD_%D0%B0%D0%BC%D1%8C%D0%B4%D1%80%D0%B0%D1%85_%D1%87%D0%B0%D0%B4%D0%B2%D0%B0%D1%80" title="Гаригийн амьдрах чадвар – Mongolian" lang="mn" hreflang="mn" data-title="Гаригийн амьдрах чадвар" data-language-autonym="Монгол" data-language-local-name="Mongolian" class="interlanguage-link-target"><span>Монгол</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E6%83%91%E6%98%9F%E3%81%AE%E5%B1%85%E4%BD%8F%E5%8F%AF%E8%83%BD%E6%80%A7" title="惑星の居住可能性 – Japanese" lang="ja" hreflang="ja" data-title="惑星の居住可能性" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Planeters_evne_til_%C3%A5_opprettholde_liv" title="Planeters evne til å opprettholde liv – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Planeters evne til å opprettholde liv" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Habitabilidade_planet%C3%A1ria" title="Habitabilidade planetária – Portuguese" lang="pt" hreflang="pt" data-title="Habitabilidade planetária" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%96%D0%B8%D0%B7%D0%BD%D0%B5%D0%BF%D1%80%D0%B8%D0%B3%D0%BE%D0%B4%D0%BD%D0%BE%D1%81%D1%82%D1%8C_%D0%BF%D0%BB%D0%B0%D0%BD%D0%B5%D1%82%D1%8B" title="Жизнепригодность планеты – Russian" lang="ru" hreflang="ru" data-title="Жизнепригодность планеты" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Planetary_habitability" title="Planetary habitability – Simple English" lang="en-simple" hreflang="en-simple" data-title="Planetary habitability" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Ob%C3%BDvate%C4%BEnos%C5%A5_plan%C3%A9ty" title="Obývateľnosť planéty – Slovak" lang="sk" hreflang="sk" data-title="Obývateľnosť planéty" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl badge-Q17437796 badge-featuredarticle mw-list-item" title="featured article badge"><a href="https://sl.wikipedia.org/wiki/Naseljivi_planet" title="Naseljivi planet – Slovenian" lang="sl" hreflang="sl" data-title="Naseljivi planet" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%9F%D0%BB%D0%B0%D0%BD%D0%B5%D1%82%D0%B0%D1%80%D0%BD%D0%B0_%D1%85%D0%B0%D0%B1%D0%B8%D1%82%D0%B0%D0%BB%D0%BD%D0%BE%D1%81%D1%82" title="Планетарна хабиталност – Serbian" lang="sr" hreflang="sr" data-title="Планетарна хабиталност" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Elinkelpoinen_planeetta" title="Elinkelpoinen planeetta – Finnish" lang="fi" hreflang="fi" data-title="Elinkelpoinen planeetta" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv badge-Q17437798 badge-goodarticle mw-list-item" title="good article badge"><a href="https://sv.wikipedia.org/wiki/Himlakroppars_f%C3%B6rm%C3%A5ga_att_hysa_liv" title="Himlakroppars förmåga att hysa liv – Swedish" lang="sv" hreflang="sv" data-title="Himlakroppars förmåga att hysa liv" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%84%E0%B8%A7%E0%B8%B2%E0%B8%A1%E0%B8%AA%E0%B8%B2%E0%B8%A1%E0%B8%B2%E0%B8%A3%E0%B8%96%E0%B8%AD%E0%B8%A2%E0%B8%B9%E0%B9%88%E0%B8%AD%E0%B8%B2%E0%B8%A8%E0%B8%B1%E0%B8%A2%E0%B9%84%E0%B8%94%E0%B9%89%E0%B8%82%E0%B8%AD%E0%B8%87%E0%B8%94%E0%B8%B2%E0%B8%A7%E0%B9%80%E0%B8%84%E0%B8%A3%E0%B8%B2%E0%B8%B0%E0%B8%AB%E0%B9%8C" title="ความสามารถอยู่อาศัยได้ของดาวเคราะห์ – Thai" lang="th" hreflang="th" data-title="ความสามารถอยู่อาศัยได้ของดาวเคราะห์" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Gezegensel_ya%C5%9Fanabilirlik" title="Gezegensel yaşanabilirlik – Turkish" lang="tr" hreflang="tr" data-title="Gezegensel yaşanabilirlik" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%96%D0%B8%D1%82%D1%82%D1%94%D0%BF%D1%80%D0%B8%D0%B4%D0%B0%D1%82%D0%BD%D1%96%D1%81%D1%82%D1%8C_%D0%BF%D0%BB%D0%B0%D0%BD%D0%B5%D1%82%D0%B8" title="Життєпридатність планети – Ukrainian" lang="uk" hreflang="uk" data-title="Життєпридатність планети" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-ur mw-list-item"><a href="https://ur.wikipedia.org/wiki/%D8%B3%DB%8C%D8%A7%D8%B1%D9%88%DB%8C_%D8%B3%DA%A9%D9%88%D9%86%D8%AA_%D9%BE%D8%B0%DB%8C%D8%B1%DB%8C%D8%AA" title="سیاروی سکونت پذیریت – Urdu" lang="ur" hreflang="ur" data-title="سیاروی سکونت پذیریت" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Kh%E1%BA%A3_n%C4%83ng_sinh_s%E1%BB%91ng_tr%C3%AAn_h%C3%A0nh_tinh" title="Khả năng sinh sống trên hành tinh – Vietnamese" lang="vi" hreflang="vi" data-title="Khả năng sinh sống trên hành tinh" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E8%A1%8C%E6%98%9F%E9%81%A9%E5%B1%85%E6%80%A7" title="行星適居性 – Chinese" lang="zh" hreflang="zh" data-title="行星適居性" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q846030#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Planetary_habitability" title="View the content page [c]" accesskey="c"><span>Article</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a href="/wiki/Talk:Planetary_habitability" rel="discussion" title="Discuss improvements to the content page [t]" accesskey="t"><span>Talk</span></a></li> </ul> </div> </div> <div id="vector-variants-dropdown" class="vector-dropdown emptyPortlet" > <input type="checkbox" id="vector-variants-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-variants-dropdown" class="vector-dropdown-checkbox " aria-label="Change language variant" > <label id="vector-variants-dropdown-label" for="vector-variants-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">English</span> </label> <div class="vector-dropdown-content"> <div id="p-variants" class="vector-menu mw-portlet mw-portlet-variants emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> </div> </div> </nav> </div> <div id="right-navigation" class="vector-collapsible"> <nav aria-label="Views"> <div id="p-views" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-views" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-view" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Planetary_habitability"><span>Read</span></a></li><li id="ca-edit" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Planetary_habitability&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-history" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Planetary_habitability&action=history" title="Past revisions of this page [h]" accesskey="h"><span>View history</span></a></li> </ul> </div> </div> </nav> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-dropdown" class="vector-dropdown vector-page-tools-dropdown" > <input type="checkbox" id="vector-page-tools-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-tools-dropdown" class="vector-dropdown-checkbox " aria-label="Tools" > <label id="vector-page-tools-dropdown-label" for="vector-page-tools-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">Tools</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-tools-unpinned-container" class="vector-unpinned-container"> <div id="vector-page-tools" class="vector-page-tools vector-pinnable-element"> <div class="vector-pinnable-header vector-page-tools-pinnable-header vector-pinnable-header-unpinned" data-feature-name="page-tools-pinned" data-pinnable-element-id="vector-page-tools" data-pinned-container-id="vector-page-tools-pinned-container" data-unpinned-container-id="vector-page-tools-unpinned-container" > <div class="vector-pinnable-header-label">Tools</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-page-tools.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-page-tools.unpin">hide</button> </div> <div id="p-cactions" class="vector-menu mw-portlet mw-portlet-cactions emptyPortlet vector-has-collapsible-items" title="More options" > <div class="vector-menu-heading"> Actions </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-more-view" class="selected vector-more-collapsible-item mw-list-item"><a href="/wiki/Planetary_habitability"><span>Read</span></a></li><li id="ca-more-edit" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Planetary_habitability&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-more-history" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Planetary_habitability&action=history"><span>View history</span></a></li> </ul> </div> </div> <div id="p-tb" class="vector-menu mw-portlet mw-portlet-tb" > <div class="vector-menu-heading"> General </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-whatlinkshere" class="mw-list-item"><a href="/wiki/Special:WhatLinksHere/Planetary_habitability" title="List of all English Wikipedia pages containing links to this page [j]" accesskey="j"><span>What links here</span></a></li><li id="t-recentchangeslinked" class="mw-list-item"><a href="/wiki/Special:RecentChangesLinked/Planetary_habitability" rel="nofollow" title="Recent changes in pages linked from this page [k]" accesskey="k"><span>Related changes</span></a></li><li id="t-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_Upload_Wizard" title="Upload files [u]" accesskey="u"><span>Upload file</span></a></li><li id="t-specialpages" class="mw-list-item"><a href="/wiki/Special:SpecialPages" title="A list of all special pages [q]" accesskey="q"><span>Special pages</span></a></li><li id="t-permalink" class="mw-list-item"><a href="/w/index.php?title=Planetary_habitability&oldid=1259831068" title="Permanent link to this revision of this page"><span>Permanent link</span></a></li><li id="t-info" class="mw-list-item"><a href="/w/index.php?title=Planetary_habitability&action=info" title="More information about this page"><span>Page information</span></a></li><li id="t-cite" class="mw-list-item"><a href="/w/index.php?title=Special:CiteThisPage&page=Planetary_habitability&id=1259831068&wpFormIdentifier=titleform" title="Information on how to cite this page"><span>Cite this page</span></a></li><li id="t-urlshortener" class="mw-list-item"><a href="/w/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FPlanetary_habitability"><span>Get shortened URL</span></a></li><li id="t-urlshortener-qrcode" class="mw-list-item"><a href="/w/index.php?title=Special:QrCode&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FPlanetary_habitability"><span>Download QR code</span></a></li> </ul> </div> </div> <div id="p-coll-print_export" class="vector-menu mw-portlet mw-portlet-coll-print_export" > <div class="vector-menu-heading"> Print/export </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="coll-download-as-rl" class="mw-list-item"><a href="/w/index.php?title=Special:DownloadAsPdf&page=Planetary_habitability&action=show-download-screen" title="Download this page as a PDF file"><span>Download as PDF</span></a></li><li id="t-print" class="mw-list-item"><a href="/w/index.php?title=Planetary_habitability&printable=yes" title="Printable version of this page [p]" accesskey="p"><span>Printable version</span></a></li> </ul> </div> </div> <div id="p-wikibase-otherprojects" class="vector-menu mw-portlet mw-portlet-wikibase-otherprojects" > <div class="vector-menu-heading"> In other projects </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-wikibase" class="wb-otherproject-link wb-otherproject-wikibase-dataitem mw-list-item"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q846030" title="Structured data on this page hosted by Wikidata [g]" accesskey="g"><span>Wikidata item</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> <div id="mw-indicator-spoken-icon" class="mw-indicator"><div class="mw-parser-output"><span typeof="mw:File"><a href="/wiki/File:PlanetaryHabitability.ogg" title="Listen to this article"><img alt="Listen to this article" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/47/Sound-icon.svg/20px-Sound-icon.svg.png" decoding="async" width="20" height="15" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/47/Sound-icon.svg/30px-Sound-icon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/47/Sound-icon.svg/40px-Sound-icon.svg.png 2x" data-file-width="128" data-file-height="96" /></a></span></div></div> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Known extent to which a planet is suitable for life</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">"Habitable planet" redirects here. For a list of potentially habitable planets found to date, see <a href="/wiki/List_of_potentially_habitable_exoplanets" title="List of potentially habitable exoplanets">List of potentially habitable exoplanets</a>.</div> <p class="mw-empty-elt"> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:The_Blue_Marble_(remastered).jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/cb/The_Blue_Marble_%28remastered%29.jpg/220px-The_Blue_Marble_%28remastered%29.jpg" decoding="async" width="220" height="220" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/cb/The_Blue_Marble_%28remastered%29.jpg/330px-The_Blue_Marble_%28remastered%29.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/cb/The_Blue_Marble_%28remastered%29.jpg/440px-The_Blue_Marble_%28remastered%29.jpg 2x" data-file-width="3000" data-file-height="3000" /></a><figcaption>Understanding planetary habitability is partly an extrapolation of the conditions on <a href="/wiki/Earth" title="Earth">Earth</a>, as this is the only <a href="/wiki/Planet" title="Planet">planet</a> known to support <a href="/wiki/Life" title="Life">life</a>.</figcaption></figure> <p><b>Planetary habitability</b> is the measure of a <a href="/wiki/Planet" title="Planet">planet</a>'s or a <a href="/wiki/Natural_satellite" title="Natural satellite">natural satellite</a>'s potential to <a href="/wiki/Abiogenesis" title="Abiogenesis">develop</a> and maintain an environment hospitable to <a href="/wiki/Life" title="Life">life</a>.<sup id="cite_ref-NASA-20150407_1-0" class="reference"><a href="#cite_note-NASA-20150407-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Life may be <a href="/wiki/Abiogenesis" title="Abiogenesis">generated directly</a> on a planet or satellite endogenously. Research suggests that life may also be transferred from one body to another, through a hypothetical process known as <a href="/wiki/Panspermia" title="Panspermia">panspermia</a>.<sup id="cite_ref-NASA_strategy_2015_2-0" class="reference"><a href="#cite_note-NASA_strategy_2015-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Environments do not need to contain life to be considered habitable nor are accepted <a href="/wiki/Habitable_zone" title="Habitable zone">habitable zones</a> (HZ) the only areas in which life might arise.<sup id="cite_ref-Seager_2013_3-0" class="reference"><a href="#cite_note-Seager_2013-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>As the existence of <a href="/wiki/Life_beyond_Earth" class="mw-redirect" title="Life beyond Earth">life beyond Earth</a> is unknown, planetary habitability is largely an <a href="/wiki/Extrapolation" title="Extrapolation">extrapolation</a> of conditions on Earth and the characteristics of the <a href="/wiki/Sun" title="Sun">Sun</a> and <a href="/wiki/Solar_System" title="Solar System">Solar System</a> which appear favorable to life's flourishing.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Of particular interest are those factors that have sustained complex, <a href="/wiki/Multicellular" class="mw-redirect" title="Multicellular">multicellular</a> organisms on Earth and not just simpler, <a href="/wiki/Unicellular" class="mw-redirect" title="Unicellular">unicellular</a> creatures. Research and theory in this regard is a component of a number of natural sciences, such as <a href="/wiki/Astronomy" title="Astronomy">astronomy</a>, <a href="/wiki/Planetary_science" title="Planetary science">planetary science</a> and the emerging discipline of <a href="/wiki/Astrobiology" title="Astrobiology">astrobiology</a>. </p><p>An absolute requirement for life is an <a href="/wiki/Energy" title="Energy">energy</a> source, and the notion of planetary habitability implies that many other <a href="/wiki/Geophysics" title="Geophysics">geophysical</a>, <a href="/wiki/Geochemical" class="mw-redirect" title="Geochemical">geochemical</a>, and <a href="/wiki/Astrophysical" class="mw-redirect" title="Astrophysical">astrophysical</a> criteria must be met before an astronomical body can support life. In its astrobiology roadmap, <a href="/wiki/NASA" title="NASA">NASA</a> has defined the principal habitability criteria as "extended regions of liquid water,<sup id="cite_ref-NASA-20150407_1-1" class="reference"><a href="#cite_note-NASA-20150407-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> conditions favorable for the assembly of complex <a href="/wiki/Organic_molecules" class="mw-redirect" title="Organic molecules">organic molecules</a>, and energy sources to sustain <a href="/wiki/Metabolism" title="Metabolism">metabolism</a>".<sup id="cite_ref-NASA1_5-0" class="reference"><a href="#cite_note-NASA1-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> In August 2018, researchers reported that <a href="/wiki/Ocean_planet" class="mw-redirect" title="Ocean planet">water worlds</a> could support life.<sup id="cite_ref-EA-2018901_6-0" class="reference"><a href="#cite_note-EA-2018901-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-APJ-20180831_7-0" class="reference"><a href="#cite_note-APJ-20180831-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>Habitability indicators and <a href="/wiki/Biosignature" title="Biosignature">biosignatures</a> must be interpreted within a planetary and environmental context.<sup id="cite_ref-NASA_strategy_2015_2-1" class="reference"><a href="#cite_note-NASA_strategy_2015-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> In determining the habitability potential of a body, studies focus on its bulk composition, <a href="/wiki/Orbit" title="Orbit">orbital</a> properties, <a href="/wiki/Atmosphere" title="Atmosphere">atmosphere</a>, and potential chemical interactions. Stellar characteristics of importance include <a href="/wiki/Solar_mass" title="Solar mass">mass</a> and <a href="/wiki/Luminosity" title="Luminosity">luminosity</a>, stable <a href="/wiki/Stellar_variation" class="mw-redirect" title="Stellar variation">variability</a>, and high <a href="/wiki/Metallicity" title="Metallicity">metallicity</a>. Rocky, wet <a href="/wiki/Terrestrial_planet" title="Terrestrial planet">terrestrial</a>-type planets and moons with the potential for <a href="/wiki/Biochemistry" title="Biochemistry">Earth-like chemistry</a> are a primary focus of astrobiological research, although more speculative habitability theories occasionally examine <a href="/wiki/Alternative_biochemistries" class="mw-redirect" title="Alternative biochemistries">alternative biochemistries</a> and other <a href="/wiki/Astronomical_object" title="Astronomical object">types of astronomical bodies</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Background">Background</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=1" title="Edit section: Background"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The idea that planets beyond Earth might host life is an ancient one, though historically it was framed by <a href="/wiki/Philosophy" title="Philosophy">philosophy</a> as much as <a href="/wiki/Physical_science" class="mw-redirect" title="Physical science">physical science</a>.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>a<span class="cite-bracket">]</span></a></sup> The late 20th century saw two breakthroughs in the field. The observation and <a href="/wiki/Robotic_spacecraft" class="mw-redirect" title="Robotic spacecraft">robotic spacecraft</a> <a href="/wiki/Space_exploration" title="Space exploration">exploration</a> of other planets and moons within the Solar System has provided critical information on defining habitability criteria and allowed for substantial geophysical comparisons between the Earth and other bodies. The discovery of <a href="/wiki/Exoplanet" title="Exoplanet">exoplanets</a>, beginning in the early 1990s<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> and accelerating thereafter, has provided further information for the study of possible extraterrestrial life. These findings confirm that the Sun is not unique among <a href="/wiki/Star" title="Star">stars</a> in hosting planets and expands the habitability research horizon beyond the Solar System. </p><p>While Earth is the only place in the Universe known to harbor life,<sup id="cite_ref-NASA-1990_11-0" class="reference"><a href="#cite_note-NASA-1990-11"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Astrobiology-2008_12-0" class="reference"><a href="#cite_note-Astrobiology-2008-12"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> estimates of <a href="/wiki/Habitable_zone" title="Habitable zone">habitable zones</a> around other stars,<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-NYT-20131118_14-0" class="reference"><a href="#cite_note-NYT-20131118-14"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> along with the discovery of thousands of <a href="/wiki/Exoplanet" title="Exoplanet">exoplanets</a> and new insights into the extreme habitats on Earth where organisms known as <a href="/wiki/Extremophile" title="Extremophile">extremophiles</a> live, suggest that there may be many more habitable places in the Universe than considered possible until very recently.<sup id="cite_ref-NYT-20150106-DB_15-0" class="reference"><a href="#cite_note-NYT-20150106-DB-15"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> On 4 November 2013, astronomers reported, based on <a href="/wiki/Kepler_space_telescope" title="Kepler space telescope"><i>Kepler</i> space mission</a> data, that there could be as many as 40 billion <a href="/wiki/Terrestrial_planet" title="Terrestrial planet">Earth-sized</a> <a href="/wiki/Extrasolar_planets" class="mw-redirect" title="Extrasolar planets">planets</a> orbiting in the <a href="/wiki/Habitable_zone" title="Habitable zone">habitable zones</a> of <a href="/wiki/Solar_analog" title="Solar analog">Sun-like stars</a> and <a href="/wiki/Red_dwarf" title="Red dwarf">red dwarfs</a> within the <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a>.<sup id="cite_ref-NYT-20131104_16-0" class="reference"><a href="#cite_note-NYT-20131104-16"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-PNAS-20131031_17-0" class="reference"><a href="#cite_note-PNAS-20131031-17"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> 11 billion of these estimated planets may be orbiting Sun-like stars.<sup id="cite_ref-LATimes-20131104_18-0" class="reference"><a href="#cite_note-LATimes-20131104-18"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> The nearest such planet may be 12 <a href="/wiki/Light-year" title="Light-year">light-years</a> away, according to the scientists.<sup id="cite_ref-NYT-20131104_16-1" class="reference"><a href="#cite_note-NYT-20131104-16"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-PNAS-20131031_17-1" class="reference"><a href="#cite_note-PNAS-20131031-17"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> As of June 2021, a total of 59 potentially habitable exoplanets have been found.<sup id="cite_ref-phl.upr.edu_19-0" class="reference"><a href="#cite_note-phl.upr.edu-19"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Stellar_characteristics">Stellar characteristics</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=2" title="Edit section: Stellar characteristics"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>An understanding of planetary habitability begins with the <a href="/wiki/Stellar_influences_on_an_origin_of_life_setting" title="Stellar influences on an origin of life setting">host star</a>.<sup id="cite_ref-Review_2009_20-0" class="reference"><a href="#cite_note-Review_2009-20"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> The classical habitable zone (HZ) is defined for surface conditions only; but a metabolism that does not depend on the stellar light can still exist outside the HZ, thriving in the interior of the planet where liquid water is available.<sup id="cite_ref-Review_2009_20-1" class="reference"><a href="#cite_note-Review_2009-20"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p><p>Under the auspices of <a href="/wiki/Search_for_extraterrestrial_intelligence" title="Search for extraterrestrial intelligence">SETI</a>'s <a href="/wiki/Project_Phoenix_(SETI)" title="Project Phoenix (SETI)">Project Phoenix</a>, scientists <a href="/wiki/Margaret_Turnbull" title="Margaret Turnbull">Margaret Turnbull</a> and <a href="/wiki/Jill_Tarter" title="Jill Tarter">Jill Tarter</a> developed the "<a href="/wiki/HabCat" class="mw-redirect" title="HabCat">HabCat</a>" (or Catalogue of Habitable Stellar Systems) in 2002. The catalogue was formed by winnowing the nearly 120,000 stars of the larger <a href="/wiki/Hipparcos_Catalogue" class="mw-redirect" title="Hipparcos Catalogue">Hipparcos Catalogue</a> into a core group of 17,000 potentially habitable stars, and the selection criteria that were used provide a good starting point for understanding which astrophysical factors are necessary for habitable planets.<sup id="cite_ref-ajs.145_21-0" class="reference"><a href="#cite_note-ajs.145-21"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> According to research published in August 2015, very large galaxies may be more favorable to the formation and development of habitable planets than smaller galaxies, like the <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a> galaxy.<sup id="cite_ref-SP-20150821_22-0" class="reference"><a href="#cite_note-SP-20150821-22"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p><p>However, what makes a planet habitable is a much more complex question than having a planet located at the right distance from its host star so that water can be liquid on its surface: various <a href="/wiki/Geophysics" title="Geophysics">geophysical</a> and <a href="/wiki/Geodynamics" title="Geodynamics">geodynamical</a> aspects, the radiation, and the host star's <a href="/wiki/Plasma_(physics)" title="Plasma (physics)">plasma</a> environment can influence the evolution of planets and life, if it originated.<sup id="cite_ref-Review_2009_20-2" class="reference"><a href="#cite_note-Review_2009-20"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> Liquid water is a necessary<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> but not sufficient condition for life as we know it, as habitability is a function of a multitude of environmental parameters.<sup id="cite_ref-NASA_strategy_2015_2-2" class="reference"><a href="#cite_note-NASA_strategy_2015-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Spectral_class">Spectral class</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=3" title="Edit section: Spectral class"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Stellar_classification" title="Stellar classification">spectral class</a> of a star indicates its <a href="/wiki/Photosphere" title="Photosphere">photospheric temperature</a>, which (for <a href="/wiki/Main_sequence" title="Main sequence">main-sequence stars</a>) correlates to overall mass. The appropriate spectral range for habitable stars is considered to be "late F" or "G", to "mid-K". This corresponds to temperatures of a little more than 7,000 <a href="/wiki/Kelvin" title="Kelvin">K</a> down to a little less than 4,000 K (6,700 °C to 3,700 °C); the Sun, a G2 star at 5,777 K, is well within these bounds. This spectral range probably accounts for between 5% and 10% of stars in the local <a href="/wiki/Milky_Way_galaxy" class="mw-redirect" title="Milky Way galaxy">Milky Way galaxy</a>. "Middle-class" stars of this sort have a number of characteristics considered important to planetary habitability: </p> <ul><li>They live at least a few hundred million years, allowing life a chance to evolve. More <a href="/wiki/Luminosity" title="Luminosity">luminous</a> main-sequence stars of the "O" classes and many members of the "B" classes usually live less than 500 million years and in exceptional cases less than 10 million.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>b<span class="cite-bracket">]</span></a></sup></li> <li>They emit enough high-frequency <a href="/wiki/Ultraviolet_radiation" class="mw-redirect" title="Ultraviolet radiation">ultraviolet radiation</a> to trigger important atmospheric dynamics such as <a href="/wiki/Ozone" title="Ozone">ozone</a> formation, but not so much that <a href="/wiki/Ionisation" class="mw-redirect" title="Ionisation">ionisation</a> destroys incipient life.<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup></li> <li>They emit sufficient radiation at wavelengths conducive to photosynthesis.<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup></li> <li>Liquid water may exist on the surface of planets orbiting them at a distance that does not induce <a href="/wiki/Tidal_locking" title="Tidal locking">tidal locking</a>.</li></ul> <p><a href="/wiki/K-type_main-sequence_star" title="K-type main-sequence star">K-type stars</a> may be able to support life far longer than the <a href="/wiki/Sun" title="Sun">Sun</a>.<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> </p><p>Whether fainter late K and M class <a href="/wiki/Red_dwarf" title="Red dwarf">red dwarf</a> stars are also suitable hosts for habitable planets is perhaps the most important open question in the entire field of planetary habitability given their prevalence (<a href="/wiki/Habitability_of_red_dwarf_systems" title="Habitability of red dwarf systems">habitability of red dwarf systems</a>). <a href="/wiki/Gliese_581_c" class="mw-redirect" title="Gliese 581 c">Gliese 581 c</a>, a "<a href="/wiki/Super-Earth" title="Super-Earth">super-Earth</a>", has been found orbiting in the "<a href="/wiki/Habitable_zone" title="Habitable zone">habitable zone</a>" (HZ) of a <a href="/wiki/Red_dwarf" title="Red dwarf">red dwarf</a> and may possess liquid water. However it is also possible that a greenhouse effect may render it too hot to support life, while its neighbor, <a href="/wiki/Gliese_581_d" class="mw-redirect" title="Gliese 581 d">Gliese 581 d</a>, may be a more likely candidate for habitability.<sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> In September 2010, the discovery was announced of another planet, <a href="/wiki/Gliese_581_g" class="mw-redirect" title="Gliese 581 g">Gliese 581 g</a>, in an orbit between these two planets. However, reviews of the discovery have placed the existence of this planet in doubt, and it is listed as "unconfirmed". In September 2012, the discovery of two planets orbiting <a href="/wiki/Gliese_163" title="Gliese 163">Gliese 163</a><sup id="cite_ref-Simbad-20120920_30-0" class="reference"><a href="#cite_note-Simbad-20120920-30"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> was announced.<sup id="cite_ref-PHL-20120829_31-0" class="reference"><a href="#cite_note-PHL-20120829-31"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Space-20120920_32-0" class="reference"><a href="#cite_note-Space-20120920-32"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> One of the planets, <a href="/wiki/Gliese_163_c" title="Gliese 163 c">Gliese 163 c</a>, about 6.9 times the mass of Earth and somewhat hotter, was considered to be within the habitable zone.<sup id="cite_ref-PHL-20120829_31-1" class="reference"><a href="#cite_note-PHL-20120829-31"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Space-20120920_32-1" class="reference"><a href="#cite_note-Space-20120920-32"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> </p><p>A recent study suggests that cooler stars that emit more light in the infrared and near infrared may actually host warmer planets with less ice and incidence of snowball states. These wavelengths are absorbed by their planets' ice and greenhouse gases and remain warmer.<sup id="cite_ref-red.1112902301_33-0" class="reference"><a href="#cite_note-red.1112902301-33"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> </p><p>A 2020 study found that about half of Sun-like stars could host rocky, potentially habitable planets. Specifically, they estimated with that, on average, the nearest habitable zone planet around G and K-type stars is about 6 parsecs away, and there are about 4 rocky planets around G and K-type stars within 10 parsecs (32.6 light years) of the Sun.<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Stable_habitable_zone">Stable habitable zone</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=4" title="Edit section: Stable habitable zone"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Habitable_zone" title="Habitable zone">Habitable zone</a></div> <p>The habitable zone (HZ) is a <a href="/wiki/Spherical_shell" title="Spherical shell">shell</a>-shaped region of space surrounding a star in which a planet could maintain liquid water on its surface.<sup id="cite_ref-Review_2009_20-3" class="reference"><a href="#cite_note-Review_2009-20"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> The concept was first proposed by astrophysicist <a href="/wiki/Su-Shu_Huang" title="Su-Shu Huang">Su-Shu Huang</a> in 1959, based on climatic constraints imposed by the host star.<sup id="cite_ref-Review_2009_20-4" class="reference"><a href="#cite_note-Review_2009-20"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> After an energy source, liquid water is widely considered the most important ingredient for life, considering how integral it is to all life systems on Earth. However, if life is discovered in the absence of water, the definition of an HZ may have to be greatly expanded. </p><p>The inner edge of the HZ is the distance where <a href="/wiki/Runaway_greenhouse_effect" title="Runaway greenhouse effect">runaway greenhouse effect</a> vaporize the whole water reservoir and, as a second effect, induce the photodissociation of water vapor and the loss of hydrogen to space. The outer edge of the HZ is the distance from the star where a maximum greenhouse effect fails to keep the surface of the planet above the freezing point, and by <span class="chemf nowrap">CO<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">2</sub></span></span></span>(carbon dioxide) condensation.<sup id="cite_ref-Review_2009_20-5" class="reference"><a href="#cite_note-Review_2009-20"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Seager_2013_3-1" class="reference"><a href="#cite_note-Seager_2013-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>A "stable" HZ implies two factors. First, the range of an HZ should not vary greatly over time. All stars increase in luminosity as they age, and a given HZ thus migrates outwards, but if this happens too quickly (for example, with a super-massive star) planets may only have a brief window inside the HZ and a correspondingly smaller chance of developing life. Calculating an HZ range and its long-term movement is never straightforward, as negative <a href="/wiki/Feedback" title="Feedback">feedback loops</a> such as the <a href="/wiki/CNO_cycle" title="CNO cycle">CNO cycle</a> will tend to offset the increases in luminosity. Assumptions made about atmospheric conditions and geology thus have as great an impact on a putative HZ range as does stellar evolution: the proposed parameters of the Sun's HZ, for example, have fluctuated greatly.<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p><p>Second, no large-mass body such as a <a href="/wiki/Gas_giant" title="Gas giant">gas giant</a> should be present in or relatively close to the HZ, thus disrupting the formation of Earth-size bodies. The matter in the asteroid belt, for example, appears to have been unable to accrete into a planet due to orbital resonances with Jupiter; if the giant had appeared in the region that is now between the orbits of <a href="/wiki/Venus" title="Venus">Venus</a> and <a href="/wiki/Mars" title="Mars">Mars</a>, Earth would almost certainly not have developed in its present form. However a gas giant inside the HZ might have <a href="/wiki/Habitable_moon" class="mw-redirect" title="Habitable moon">habitable moons</a> under the right conditions.<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Low_stellar_variation">Low stellar variation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=5" title="Edit section: Low stellar variation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Variable_star" title="Variable star">Variable star</a></div> <p>Changes in <a href="/wiki/Luminosity" title="Luminosity">luminosity</a> are common to all stars, but the severity of such fluctuations covers a broad range. Most stars are relatively stable, but a significant minority of variable stars often undergo sudden and intense increases in luminosity and consequently in the amount of energy radiated toward bodies in orbit. These stars are considered poor candidates for hosting life-bearing planets, as their unpredictability and energy output changes would negatively impact <a href="/wiki/Organism" title="Organism">organisms</a>: living things adapted to a specific temperature range could not survive too great a temperature variation. Further, upswings in luminosity are generally accompanied by massive doses of <a href="/wiki/Gamma_ray" title="Gamma ray">gamma ray</a> and <a href="/wiki/X-ray" title="X-ray">X-ray</a> radiation which might prove lethal. <a href="/wiki/Celestial_body_atmosphere" class="mw-redirect" title="Celestial body atmosphere">Atmospheres</a> do mitigate such effects, but their atmosphere might not be retained by planets orbiting variables, because the high-frequency energy buffeting these planets would continually strip them of their protective covering. </p><p>The Sun, in this respect as in many others, is relatively benign: the variation between its maximum and minimum energy output is roughly 0.1% over its 11-year <a href="/wiki/Solar_cycle" title="Solar cycle">solar cycle</a>. There is strong (though not undisputed) <a href="/wiki/Solar_variation" class="mw-redirect" title="Solar variation">evidence</a> that even minor changes in the Sun's luminosity have had significant effects on the Earth's climate well within the historical era: the <a href="/wiki/Little_Ice_Age" title="Little Ice Age">Little Ice Age</a> of the mid-second millennium, for instance, may have been caused by a relatively long-term decline in the Sun's luminosity.<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> Thus, a star does not have to be a true variable for differences in luminosity to affect habitability. Of known <a href="/wiki/Solar_analog" title="Solar analog">solar analogs</a>, one that closely resembles the Sun is considered to be <a href="/wiki/18_Scorpii" title="18 Scorpii">18 Scorpii</a>; unfortunately for the prospects of life existing in its proximity, the only significant difference between the two bodies is the amplitude of the solar cycle, which appears to be much greater for 18 Scorpii.<sup id="cite_ref-39" class="reference"><a href="#cite_note-39"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="High_metallicity">High metallicity</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=6" title="Edit section: High metallicity"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Metallicity" title="Metallicity">Metallicity</a></div> <p>While the bulk of material in any star is <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a> and <a href="/wiki/Helium" title="Helium">helium</a>, there is a significant variation in the amount of heavier elements (<a href="/wiki/Metal-rich" class="mw-redirect" title="Metal-rich">metals</a>). A high proportion of metals in a star correlates to the amount of heavy material initially available in the <a href="/wiki/Protoplanetary_disk" title="Protoplanetary disk">protoplanetary disk</a>. A smaller amount of metal makes the formation of planets much less likely, under the <a href="/wiki/Solar_nebula" class="mw-redirect" title="Solar nebula">solar nebula</a> theory of <a href="/wiki/Planetary_system" title="Planetary system">planetary system</a> formation. Any planets that did form around a metal-poor star would probably be low in mass, and thus unfavorable for life. <a href="/wiki/Spectroscopy" title="Spectroscopy">Spectroscopic</a> studies of systems where <a href="/wiki/Exoplanet" title="Exoplanet">exoplanets</a> have been found to date confirm the relationship between high metal content and planet formation: "Stars with planets, or at least with planets similar to the ones we are finding today, are clearly more metal rich than stars without planetary companions."<sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup> This relationship between high metallicity and planet formation also means that habitable systems are more likely to be found around stars of younger generations, since stars that formed early in the <a href="/wiki/Universe" title="Universe">universe</a>'s history have low metal content. </p> <div class="mw-heading mw-heading2"><h2 id="Planetary_characteristics">Planetary characteristics</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=7" title="Edit section: Planetary characteristics"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Earthlike_moon_extrasolar_gas_giant.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/71/Earthlike_moon_extrasolar_gas_giant.jpg/220px-Earthlike_moon_extrasolar_gas_giant.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/71/Earthlike_moon_extrasolar_gas_giant.jpg/330px-Earthlike_moon_extrasolar_gas_giant.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/71/Earthlike_moon_extrasolar_gas_giant.jpg/440px-Earthlike_moon_extrasolar_gas_giant.jpg 2x" data-file-width="800" data-file-height="600" /></a><figcaption>The moons of some gas giants could potentially be habitable.<sup id="cite_ref-moonlife_41-0" class="reference"><a href="#cite_note-moonlife-41"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup></figcaption></figure> <p>Habitability indicators and <a href="/wiki/Biosignature" title="Biosignature">biosignatures</a> must be interpreted within a planetary and environmental context.<sup id="cite_ref-NASA_strategy_2015_2-3" class="reference"><a href="#cite_note-NASA_strategy_2015-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Whether a planet will emerge as habitable depends on the sequence of events that led to its formation, which could include the production of organic molecules in <a href="/wiki/Molecular_cloud" title="Molecular cloud">molecular clouds</a> and <a href="/wiki/Protoplanetary_disk" title="Protoplanetary disk">protoplanetary disks</a>, delivery of materials during and after planetary <a href="/wiki/Accretion_(astrophysics)" title="Accretion (astrophysics)">accretion</a>, and the orbital location in the planetary system.<sup id="cite_ref-NASA_strategy_2015_2-4" class="reference"><a href="#cite_note-NASA_strategy_2015-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> The chief assumption about habitable planets is that they are <a href="/wiki/Terrestrial_planet" title="Terrestrial planet">terrestrial</a>. Such planets, roughly within one <a href="/wiki/Order_of_magnitude" title="Order of magnitude">order of magnitude</a> of <a href="/wiki/Earth_mass" title="Earth mass">Earth mass</a>, are primarily composed of <a href="/wiki/Silicate" title="Silicate">silicate</a> rocks, and have not accreted the gaseous outer layers of <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a> and <a href="/wiki/Helium" title="Helium">helium</a> found on <a href="/wiki/Gas_giant" title="Gas giant">gas giants</a>. The possibility that life could evolve in the cloud tops of giant planets has not been decisively ruled out,<sup id="cite_ref-44" class="reference"><a href="#cite_note-44"><span class="cite-bracket">[</span>c<span class="cite-bracket">]</span></a></sup> though it is considered unlikely, as they have no surface and their gravity is enormous.<sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> The natural satellites of giant planets, meanwhile, <a href="/wiki/Habitability_of_natural_satellites" title="Habitability of natural satellites">remain valid candidates for hosting life</a>.<sup id="cite_ref-moonlife_41-1" class="reference"><a href="#cite_note-moonlife-41"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> </p><p>In February 2011 the <a href="/wiki/Kepler_space_telescope" title="Kepler space telescope">Kepler Space Observatory Mission team</a> released a <a href="/wiki/List_of_exoplanets_discovered_using_the_Kepler_space_telescope" class="mw-redirect" title="List of exoplanets discovered using the Kepler space telescope">list of 1235 extrasolar planet candidates</a>, including 54 that may be in the habitable zone.<sup id="cite_ref-borucki_46-0" class="reference"><a href="#cite_note-borucki-46"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-47" class="reference"><a href="#cite_note-47"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup> Six of the candidates in this zone are smaller than twice the size of Earth.<sup id="cite_ref-borucki_46-1" class="reference"><a href="#cite_note-borucki-46"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> A more recent study found that one of these candidates (KOI 326.01) is much larger and hotter than first reported.<sup id="cite_ref-Grant_48-0" class="reference"><a href="#cite_note-Grant-48"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> Based on the findings, the Kepler team estimated there to be "at least 50 billion planets in the Milky Way" of which "at least 500 million" are in the habitable zone.<sup id="cite_ref-BorensteinS_49-0" class="reference"><a href="#cite_note-BorensteinS-49"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> </p><p>In analyzing which environments are likely to support life, a distinction is usually made between simple, unicellular organisms such as <a href="/wiki/Bacteria" title="Bacteria">bacteria</a> and <a href="/wiki/Archaea" title="Archaea">archaea</a> and complex metazoans (animals). Unicellularity necessarily precedes multicellularity in any hypothetical tree of life, and where single-celled organisms do emerge there is no assurance that greater complexity will then develop.<sup id="cite_ref-50" class="reference"><a href="#cite_note-50"><span class="cite-bracket">[</span>d<span class="cite-bracket">]</span></a></sup> The planetary characteristics listed below are considered crucial for life generally, but in every case multicellular organisms are more picky than unicellular life. </p><p>In August 2021, a new class of habitable planets, named <a href="/wiki/Ocean_planet" class="mw-redirect" title="Ocean planet">ocean planets</a>, which involves "hot, ocean-covered planets with hydrogen-rich atmospheres", has been reported.<sup id="cite_ref-<"PHY-20210825"_51-0" class="reference"><a href="#cite_note-<"PHY-20210825"-51"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Hycean_planet" title="Hycean planet">Hycean planets</a> may soon be studied for <a href="/wiki/Biosignature" title="Biosignature">biosignatures</a> by <a href="/wiki/Telescope" title="Telescope">terrestrial telescopes</a> as well as <a href="/wiki/Space_telescope" title="Space telescope">space telescopes</a>, such as the <a href="/wiki/James_Webb_Space_Telescope" title="James Webb Space Telescope">James Webb Space Telescope</a> (JWST), which was launched on 25 December 2021.<sup id="cite_ref-BBC-20210827_52-0" class="reference"><a href="#cite_note-BBC-20210827-52"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Mass_and_size">Mass and size</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=8" title="Edit section: Mass and size"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Mars_sunset_PIA00920.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/50/Mars_sunset_PIA00920.jpg/220px-Mars_sunset_PIA00920.jpg" decoding="async" width="220" height="213" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/5/50/Mars_sunset_PIA00920.jpg 1.5x" data-file-width="248" data-file-height="240" /></a><figcaption><a href="/wiki/Mars" title="Mars">Mars</a>, with its <a href="/wiki/Rarefaction" title="Rarefaction">rarefied</a> atmosphere, is colder than the Earth would be if it were at a similar distance from the Sun.</figcaption></figure> <p>Low-mass planets are poor candidates for life for two reasons. First, their lesser <a href="/wiki/Gravity" title="Gravity">gravity</a> makes <a href="/wiki/Celestial_body_atmosphere" class="mw-redirect" title="Celestial body atmosphere">atmosphere</a> retention difficult. Constituent <a href="/wiki/Molecule" title="Molecule">molecules</a> are more likely to reach <a href="/wiki/Escape_velocity" title="Escape velocity">escape velocity</a> and be lost to space when buffeted by <a href="/wiki/Solar_wind" title="Solar wind">solar wind</a> or stirred by collision. Planets without a thick atmosphere lack the matter necessary for primal <a href="/wiki/Biochemistry" title="Biochemistry">biochemistry</a>, have little insulation and poor <a href="/wiki/Heat_transfer" title="Heat transfer">heat transfer</a> across their surfaces (for example, <a href="/wiki/Mars" title="Mars">Mars</a>, with its thin atmosphere, is colder than the Earth would be if it were at a similar distance from the Sun), and provide less protection against <a href="/wiki/Meteoroid" title="Meteoroid">meteoroids</a> and high-frequency <a href="/wiki/Radiation" title="Radiation">radiation</a>. Further, where an atmosphere is less dense than 0.006 Earth atmospheres, water cannot exist in liquid form as the required <a href="/wiki/Atmospheric_pressure" title="Atmospheric pressure">atmospheric pressure</a>, 4.56 <a href="/wiki/Torr" title="Torr">mm Hg</a> (608 Pa) (0.18 <a href="/wiki/Inch_of_mercury" title="Inch of mercury">inch Hg</a>), does not occur. In addition, a lessened pressure reduces the range of temperatures at which water is liquid. </p><p>Secondly, smaller planets have smaller <a href="/wiki/Diameter" title="Diameter">diameters</a> and thus higher surface-to-volume ratios than their larger cousins. Such bodies tend to lose the energy left over from their formation quickly and end up <a href="/wiki/Geology" title="Geology">geologically</a> dead, lacking the <a href="/wiki/Volcano" title="Volcano">volcanoes</a>, <a href="/wiki/Earthquake" title="Earthquake">earthquakes</a> and <a href="/wiki/Plate_tectonics" title="Plate tectonics">tectonic activity</a> which supply the surface with life-sustaining material and the atmosphere with temperature moderators like <a href="/wiki/Carbon_dioxide" title="Carbon dioxide">carbon dioxide</a>. Plate tectonics appear particularly crucial, at least on Earth: not only does the process recycle important chemicals and minerals, it also fosters <a href="/wiki/Bio-diversity" class="mw-redirect" title="Bio-diversity">bio-diversity</a> through continent creation and increased environmental complexity and helps create the convective cells necessary to generate <a href="/wiki/Earth%27s_magnetic_field" title="Earth's magnetic field">Earth's magnetic field</a>.<sup id="cite_ref-53" class="reference"><a href="#cite_note-53"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> </p><p>"Low mass" is partly a relative label: the Earth is low mass when compared to the Solar System's <a href="/wiki/Gas_giant" title="Gas giant">gas giants</a>, but it is the largest, by diameter and mass, and the densest of all terrestrial bodies.<sup id="cite_ref-54" class="reference"><a href="#cite_note-54"><span class="cite-bracket">[</span>e<span class="cite-bracket">]</span></a></sup> It is large enough to retain an atmosphere through gravity alone and large enough that its molten core remains a heat engine, driving the diverse geology of the surface (the decay of <a href="/wiki/Radioactive" class="mw-redirect" title="Radioactive">radioactive</a> elements within a planet's core is the other significant component of planetary heating). Mars, by contrast, is nearly (or perhaps totally) geologically dead and has lost much of its atmosphere.<sup id="cite_ref-55" class="reference"><a href="#cite_note-55"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup> Thus it would be fair to infer that the lower mass limit for habitability lies somewhere between that of Mars and that of Earth or Venus: 0.3 Earth masses has been offered as a rough dividing line for habitable planets.<sup id="cite_ref-56" class="reference"><a href="#cite_note-56"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup> However, a 2008 study by the Harvard-Smithsonian Center for Astrophysics suggests that the dividing line may be higher. Earth may in fact lie on the lower boundary of habitability: if it were any smaller, plate tectonics would be impossible. Venus, which has 85% of Earth's mass, shows no signs of tectonic activity. Conversely, "<a href="/wiki/Super-Earth" title="Super-Earth">super-Earths</a>", terrestrial planets with higher masses than Earth, would have higher levels of plate tectonics and thus be firmly placed in the habitable range.<sup id="cite_ref-57" class="reference"><a href="#cite_note-57"><span class="cite-bracket">[</span>52<span class="cite-bracket">]</span></a></sup> </p><p>Exceptional circumstances do offer exceptional cases: <a href="/wiki/Jupiter" title="Jupiter">Jupiter</a>'s moon <a href="/wiki/Io_(moon)" title="Io (moon)">Io</a> (which is smaller than any of the terrestrial planets) is volcanically dynamic because of the gravitational stresses induced by its orbit, and its neighbor <a href="/wiki/Europa_(moon)" title="Europa (moon)">Europa</a> may have a liquid ocean or icy slush underneath a frozen shell also due to power generated from orbiting a gas giant. </p><p><a href="/wiki/Saturn" title="Saturn">Saturn</a>'s <a href="/wiki/Titan_(moon)" title="Titan (moon)">Titan</a>, meanwhile, has an outside chance of harbouring life, as it has retained a thick atmosphere and has liquid <a href="/wiki/Methane" title="Methane">methane</a> seas on its surface. Organic-chemical reactions that only require minimum energy are possible in these seas, but whether any living system can be based on such minimal reactions is unclear, and would seem unlikely.<sup id="cite_ref-58" class="reference"><a href="#cite_note-58"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-59" class="reference"><a href="#cite_note-59"><span class="cite-bracket">[</span>54<span class="cite-bracket">]</span></a></sup> These satellites are exceptions, but they prove that mass, as a criterion for habitability, cannot necessarily be considered definitive at this stage of our understanding.<sup id="cite_ref-60" class="reference"><a href="#cite_note-60"><span class="cite-bracket">[</span>55<span class="cite-bracket">]</span></a></sup> </p><p>A larger planet is likely to have a more massive atmosphere. A combination of higher escape velocity to retain lighter atoms, and extensive outgassing from enhanced plate tectonics may greatly increase the atmospheric pressure and temperature at the surface compared to Earth. The enhanced greenhouse effect of such a heavy atmosphere would tend to suggest that the habitable zone should be further out from the central star for such massive planets. </p><p>Finally, a larger planet is likely to have a large iron core. This allows for a <a href="/wiki/Magnetic_field" title="Magnetic field">magnetic field</a> to <a href="/wiki/Magnetosphere" title="Magnetosphere">protect</a> the planet from <a href="/wiki/Stellar_wind" title="Stellar wind">stellar wind</a> and <a href="/wiki/Cosmic_radiation" class="mw-redirect" title="Cosmic radiation">cosmic radiation</a>, which otherwise would tend to strip away planetary atmosphere and to bombard living things with ionized particles. Mass is not the only criterion for producing a magnetic field—as the planet must also rotate fast enough to produce a <a href="/wiki/Dynamo_Theory" class="mw-redirect" title="Dynamo Theory">dynamo effect</a> within its core<sup id="cite_ref-61" class="reference"><a href="#cite_note-61"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup>—but it is a significant component of the process. </p><p>The mass of a potentially habitable exoplanet is between 0.1 and 5.0 Earth masses.<sup id="cite_ref-phl.upr.edu_19-1" class="reference"><a href="#cite_note-phl.upr.edu-19"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> However it is possible for a habitable world to have a mass as low as 0.0268 Earth Masses.<sup id="cite_ref-62" class="reference"><a href="#cite_note-62"><span class="cite-bracket">[</span>57<span class="cite-bracket">]</span></a></sup> The radius of a potentially habitable exoplanet would range between 0.5 and 1.5 Earth radii.<sup id="cite_ref-phl.upr.edu_19-2" class="reference"><a href="#cite_note-phl.upr.edu-19"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Orbit_and_rotation">Orbit and rotation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=9" title="Edit section: Orbit and rotation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>As with other criteria, stability is the critical consideration in evaluating the effect of orbital and rotational characteristics on planetary habitability. <a href="/wiki/Orbital_eccentricity" title="Orbital eccentricity">Orbital eccentricity</a> is the difference between a planet's farthest and closest approach to its parent star divided by the sum of said distances. It is a ratio describing the shape of the elliptical orbit. The greater the eccentricity the greater the temperature fluctuation on a planet's surface. Although they are adaptive, living organisms can stand only so much variation, particularly if the fluctuations overlap both the <a href="/wiki/Freezing_point" class="mw-redirect" title="Freezing point">freezing point</a> and <a href="/wiki/Boiling_point" title="Boiling point">boiling point</a> of the planet's main biotic solvent (e.g., water on Earth). If, for example, Earth's oceans were alternately boiling and freezing solid, it is difficult to imagine life as we know it having evolved. The more complex the organism, the greater the temperature sensitivity.<sup id="cite_ref-63" class="reference"><a href="#cite_note-63"><span class="cite-bracket">[</span>58<span class="cite-bracket">]</span></a></sup> The Earth's orbit is almost perfectly circular, with an eccentricity of less than 0.02; other planets in the Solar System (with the exception of <a href="/wiki/Mercury_(planet)" title="Mercury (planet)">Mercury</a>) have eccentricities that are similarly benign. </p><p>Habitability is also influenced by the architecture of the planetary system around a star. The evolution and stability of these systems are determined by gravitational dynamics, which drive the orbital evolution of terrestrial planets. Data collected on the orbital eccentricities of extrasolar planets has surprised most researchers: 90% have an orbital eccentricity greater than that found within the Solar System, and the average is fully 0.25.<sup id="cite_ref-64" class="reference"><a href="#cite_note-64"><span class="cite-bracket">[</span>59<span class="cite-bracket">]</span></a></sup> This means that the vast majority of planets have highly eccentric orbits and of these, even if their average distance from their star is deemed to be within the HZ, they nonetheless would be spending only a small portion of their time within the zone. </p><p>A planet's movement around its <a href="/wiki/Rotation" title="Rotation">rotational axis</a> must also meet certain criteria if life is to have the opportunity to evolve. A first assumption is that the planet should have moderate <a href="/wiki/Season" title="Season">seasons</a>. If there is little or no <a href="/wiki/Axial_tilt" title="Axial tilt">axial tilt</a> (or obliquity) relative to the perpendicular of the <a href="/wiki/Ecliptic" title="Ecliptic">ecliptic</a>, seasons will not occur and a main stimulant to biospheric dynamism will disappear. The planet would also be colder than it would be with a significant tilt: when the greatest intensity of radiation is always within a few degrees of the equator, warm weather cannot move poleward and a planet's climate becomes dominated by colder polar weather systems. </p><p>If a planet is radically tilted, seasons will be extreme and make it more difficult for a <a href="/wiki/Biosphere" title="Biosphere">biosphere</a> to achieve <a href="/wiki/Homeostasis" title="Homeostasis">homeostasis</a>. The axial tilt of the Earth is higher now (in the <a href="/wiki/Quaternary" title="Quaternary">Quaternary</a>) than it has been in the past, coinciding with reduced polar <a href="/wiki/Glacier" title="Glacier">ice</a>, warmer temperatures and <i>less</i> seasonal variation. Scientists do not know whether this trend will continue indefinitely with further increases in axial tilt (see <a href="/wiki/Snowball_Earth" title="Snowball Earth">Snowball Earth</a>). </p><p>The exact effects of these changes can only be computer modelled at present, and studies have shown that even extreme tilts of up to 85 degrees do not absolutely preclude life "provided it does not occupy continental surfaces plagued seasonally by the highest temperature."<sup id="cite_ref-65" class="reference"><a href="#cite_note-65"><span class="cite-bracket">[</span>60<span class="cite-bracket">]</span></a></sup> Not only the mean axial tilt, but also its variation over time must be considered. The Earth's tilt varies between 21.5 and 24.5 degrees over 41,000 years. A more drastic variation, or a much shorter periodicity, would induce climatic effects such as variations in seasonal severity. </p><p>Other orbital considerations include: </p> <ul><li>The planet should rotate relatively quickly so that the day-night cycle is not overlong. If a day takes years, the temperature differential between the day and night side will be pronounced, and problems similar to those noted with extreme orbital eccentricity will come to the fore.</li> <li>The planet also should rotate quickly enough so that a magnetic dynamo may be started in its iron core to produce a magnetic field.</li> <li>Change in the direction of the axis rotation (<a href="/wiki/Precession" title="Precession">precession</a>) should not be pronounced. In itself, precession need not affect habitability as it changes the direction of the tilt, not its degree. However, precession tends to accentuate variations caused by other orbital deviations; see <a href="/wiki/Milankovitch_cycles" title="Milankovitch cycles">Milankovitch cycles</a>. Precession on Earth occurs over a 26,000-year cycle.</li></ul> <p>The Earth's <a href="/wiki/Moon" title="Moon">Moon</a> appears to play a <a href="/wiki/Earth#Moon" title="Earth">crucial role</a> in moderating the Earth's climate by stabilising the axial tilt. It has been suggested that a chaotic tilt may be a "deal-breaker" in terms of habitability—i.e. a satellite the size of the Moon is not only helpful but required to produce stability.<sup id="cite_ref-66" class="reference"><a href="#cite_note-66"><span class="cite-bracket">[</span>61<span class="cite-bracket">]</span></a></sup> This position remains controversial.<sup id="cite_ref-67" class="reference"><a href="#cite_note-67"><span class="cite-bracket">[</span>f<span class="cite-bracket">]</span></a></sup> </p><p>In the case of the Earth, the sole Moon is sufficiently massive and orbits so as to significantly contribute to <a href="/wiki/Ocean_tides" class="mw-redirect" title="Ocean tides">ocean tides</a>, which in turn aids the dynamic churning of Earth's large liquid water oceans. These lunar forces not only help ensure that the oceans do not stagnate, but also play a critical role in Earth's dynamic climate.<sup id="cite_ref-68" class="reference"><a href="#cite_note-68"><span class="cite-bracket">[</span>62<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-69" class="reference"><a href="#cite_note-69"><span class="cite-bracket">[</span>63<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Geology">Geology</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=10" title="Edit section: Geology"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Earth_poster.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/07/Earth_poster.svg/220px-Earth_poster.svg.png" decoding="async" width="220" height="136" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/07/Earth_poster.svg/330px-Earth_poster.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/07/Earth_poster.svg/440px-Earth_poster.svg.png 2x" data-file-width="512" data-file-height="317" /></a><figcaption>Geological cross section of Earth</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><span><video id="mwe_player_0" poster="//upload.wikimedia.org/wikipedia/commons/thumb/2/2a/Simple_model_of_the_Earth%27s_magnetic_field.ogv/220px--Simple_model_of_the_Earth%27s_magnetic_field.ogv.jpg" controls="" preload="none" data-mw-tmh="" class="mw-file-element" width="220" height="124" data-durationhint="76" data-mwtitle="Simple_model_of_the_Earth's_magnetic_field.ogv" data-mwprovider="wikimediacommons" resource="/wiki/File:Simple_model_of_the_Earth%27s_magnetic_field.ogv"><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2a/Simple_model_of_the_Earth%27s_magnetic_field.ogv/Simple_model_of_the_Earth%27s_magnetic_field.ogv.480p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="480p.vp9.webm" data-width="854" data-height="480" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2a/Simple_model_of_the_Earth%27s_magnetic_field.ogv/Simple_model_of_the_Earth%27s_magnetic_field.ogv.720p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="720p.vp9.webm" data-width="1280" data-height="720" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2a/Simple_model_of_the_Earth%27s_magnetic_field.ogv/Simple_model_of_the_Earth%27s_magnetic_field.ogv.1080p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="1080p.vp9.webm" data-width="1920" data-height="1080" /><source src="//upload.wikimedia.org/wikipedia/commons/2/2a/Simple_model_of_the_Earth%27s_magnetic_field.ogv" type="video/ogg; codecs="theora"" data-width="1920" data-height="1080" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2a/Simple_model_of_the_Earth%27s_magnetic_field.ogv/Simple_model_of_the_Earth%27s_magnetic_field.ogv.240p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="240p.vp9.webm" data-width="426" data-height="240" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2a/Simple_model_of_the_Earth%27s_magnetic_field.ogv/Simple_model_of_the_Earth%27s_magnetic_field.ogv.360p.webm" type="video/webm; codecs="vp8, vorbis"" data-transcodekey="360p.webm" data-width="640" data-height="360" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2a/Simple_model_of_the_Earth%27s_magnetic_field.ogv/Simple_model_of_the_Earth%27s_magnetic_field.ogv.360p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="360p.vp9.webm" data-width="640" data-height="360" /></video></span><figcaption>A visualization showing a simple model of <a href="/wiki/Earth%27s_magnetic_field" title="Earth's magnetic field">Earth's magnetic field</a></figcaption></figure> <p>Concentrations of <a href="/wiki/Radionuclide" title="Radionuclide">radionuclides</a> in rocky planet mantles may be critical for the habitability of Earth-like planets. Such planets with higher abundances likely lack <a href="/wiki/Dynamo_theory" title="Dynamo theory">a persistent dynamo</a> for a significant fraction of their lifetimes, and those with lower concentrations <a href="/wiki/Earth%27s_internal_heat_budget#Radiogenic_heat" title="Earth's internal heat budget">may often be geologically inert</a>. Planetary dynamos create strong <a href="/wiki/Magnetic_field" title="Magnetic field">magnetic fields</a> which may often be necessary for life to develop or persist as they shield planets from <a href="/wiki/Solar_wind" title="Solar wind">solar winds</a> and <a href="/wiki/Cosmic_radiation" class="mw-redirect" title="Cosmic radiation">cosmic radiation</a>. The electromagnetic <a href="/wiki/Emission_spectra" class="mw-redirect" title="Emission spectra">emission spectra</a> of stars could be used to identify those which are more likely to host habitable Earth-like planets. As of 2020, radionuclides are thought to be produced by rare stellar processes such as <a href="/wiki/Neutron_star_merger" title="Neutron star merger">neutron star mergers</a>.<sup id="cite_ref-70" class="reference"><a href="#cite_note-70"><span class="cite-bracket">[</span>64<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-71" class="reference"><a href="#cite_note-71"><span class="cite-bracket">[</span>65<span class="cite-bracket">]</span></a></sup> </p><p>Additional geological characteristics may be essential or major factors in the habitability of natural celestial bodies – including some that may shape the body's heat and magnetic field. Some of these are unknown or not well understood and being investigated by <a href="/wiki/Planetary_scientist" class="mw-redirect" title="Planetary scientist">planetary scientists</a>, geochemists and others.<sup id="cite_ref-72" class="reference"><a href="#cite_note-72"><span class="cite-bracket">[</span>66<span class="cite-bracket">]</span></a></sup><sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs additional references to reliable sources. (December 2020)">additional citation(s) needed</span></a></i>]</sup> </p> <div class="mw-heading mw-heading4"><h4 id="Geochemistry">Geochemistry</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=11" title="Edit section: Geochemistry"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Geochemistry" title="Geochemistry">Geochemistry</a></div> <p>It is generally assumed that any extraterrestrial life that might exist will be based on the same fundamental <a href="/wiki/Biochemistry" title="Biochemistry">biochemistry</a> as found on Earth, as the four elements most vital for life, <a href="/wiki/Carbon" title="Carbon">carbon</a>, <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a>, <a href="/wiki/Oxygen" title="Oxygen">oxygen</a>, and <a href="/wiki/Nitrogen" title="Nitrogen">nitrogen</a>, are also the most common chemically reactive elements in the universe. Indeed, simple biogenic compounds, such as very simple <a href="/wiki/Amino_acid" title="Amino acid">amino acids</a> such as <a href="/wiki/Glycine" title="Glycine">glycine</a>, have been found in <a href="/wiki/Meteorite" title="Meteorite">meteorites</a> and in the <a href="/wiki/Interstellar_medium" title="Interstellar medium">interstellar medium</a>.<sup id="cite_ref-73" class="reference"><a href="#cite_note-73"><span class="cite-bracket">[</span>67<span class="cite-bracket">]</span></a></sup> These four elements together comprise over 96% of Earth's collective <a href="/wiki/Biomass" title="Biomass">biomass</a>. Carbon has an unparalleled ability to bond with itself and to form a massive array of intricate and varied structures, making it an ideal material for the complex mechanisms that form living <a href="/wiki/Cell_(biology)" title="Cell (biology)">cells</a>. Hydrogen and oxygen, in the form of water, compose the solvent in which biological processes take place and in which the first reactions occurred that led to <a href="/wiki/Abiogenesis" title="Abiogenesis">life's emergence</a>. The energy released in the formation of powerful <a href="/wiki/Covalent_bond" title="Covalent bond">covalent bonds</a> between carbon and oxygen, available by oxidizing organic compounds, is the fuel of all complex life-forms. These four elements together make up <a href="/wiki/Amino_acids" class="mw-redirect" title="Amino acids">amino acids</a>, which in turn are the building blocks of <a href="/wiki/Protein" title="Protein">proteins</a>, the substance of living tissue. In addition, neither <a href="/wiki/Sulfur" title="Sulfur">sulfur</a> (required for the building of proteins) nor <a href="/wiki/Phosphorus" title="Phosphorus">phosphorus</a> (needed for the formation of <a href="/wiki/DNA" title="DNA">DNA</a>, <a href="/wiki/RNA" title="RNA">RNA</a>, and the adenosine phosphates essential to <a href="/wiki/Metabolism" title="Metabolism">metabolism</a>) are rare. </p><p>Relative abundance in space does not always mirror differentiated abundance within planets; of the four life elements, for instance, only <a href="/wiki/Oxygen" title="Oxygen">oxygen</a> is present in any abundance in the Earth's <a href="/wiki/Crust_(geology)" title="Crust (geology)">crust</a>.<sup id="cite_ref-74" class="reference"><a href="#cite_note-74"><span class="cite-bracket">[</span>68<span class="cite-bracket">]</span></a></sup> This can be partly explained by the fact that many of these elements, such as <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a> and <a href="/wiki/Nitrogen" title="Nitrogen">nitrogen</a>, along with their simplest and most common compounds, such as <a href="/wiki/Carbon_dioxide" title="Carbon dioxide">carbon dioxide</a>, <a href="/wiki/Carbon_monoxide" title="Carbon monoxide">carbon monoxide</a>, <a href="/wiki/Methane" title="Methane">methane</a>, <a href="/wiki/Ammonia" title="Ammonia">ammonia</a>, and water, are gaseous at warm temperatures. In the hot region close to the Sun, these volatile compounds could not have played a significant role in the planets' geological formation. Instead, they were trapped as gases underneath the newly formed crusts, which were largely made of rocky, involatile compounds such as <a href="/wiki/Silica" class="mw-redirect" title="Silica">silica</a> (a compound of <a href="/wiki/Silicon" title="Silicon">silicon</a> and oxygen, accounting for oxygen's relative abundance). <a href="/wiki/Outgassing" title="Outgassing">Outgassing</a> of volatile compounds through the first volcanoes would have contributed to the formation of the planets' <a href="/wiki/Celestial_body_atmosphere" class="mw-redirect" title="Celestial body atmosphere">atmospheres</a>. The <a href="/wiki/Miller%E2%80%93Urey_experiment" title="Miller–Urey experiment">Miller–Urey experiment</a> showed that, with the application of energy, simple inorganic compounds exposed to a primordial atmosphere can react to synthesize <a href="/wiki/Amino_acid" title="Amino acid">amino acids</a>.<sup id="cite_ref-75" class="reference"><a href="#cite_note-75"><span class="cite-bracket">[</span>69<span class="cite-bracket">]</span></a></sup> </p><p>Even so, <a href="/wiki/Volcanism" title="Volcanism">volcanic</a> outgassing could not have accounted for the amount of water in Earth's oceans.<sup id="cite_ref-76" class="reference"><a href="#cite_note-76"><span class="cite-bracket">[</span>70<span class="cite-bracket">]</span></a></sup> The vast majority of the water—and arguably carbon—necessary for life must have come from the outer Solar System, away from the Sun's heat, where it could remain solid. <a href="/wiki/Comet" title="Comet">Comets</a> impacting with the Earth in the Solar System's early years would have deposited vast amounts of water, along with the other volatile compounds life requires, onto the early Earth, providing a kick-start to the <a href="/wiki/Origin_of_life" class="mw-redirect" title="Origin of life">origin of life</a>. </p><p>Thus, while there is reason to suspect that the four "life elements" ought to be readily available elsewhere, a habitable system probably also requires a supply of long-term orbiting bodies to seed inner planets. Without comets there is a possibility that life as we know it would not exist on Earth. </p> <div class="mw-heading mw-heading3"><h3 id="Microenvironments_and_extremophiles">Microenvironments and extremophiles</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=12" title="Edit section: Microenvironments and extremophiles"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Atacama.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Atacama.png/220px-Atacama.png" decoding="async" width="220" height="325" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Atacama.png/330px-Atacama.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Atacama.png/440px-Atacama.png 2x" data-file-width="493" data-file-height="728" /></a><figcaption>The <a href="/wiki/Atacama_Desert" title="Atacama Desert">Atacama Desert</a> in <a href="/wiki/South_America" title="South America">South America</a> provides an analog to <a href="/wiki/Mars" title="Mars">Mars</a> and an ideal environment to study the boundary between sterility and habitability.</figcaption></figure> <p>One important qualification to habitability criteria is that only a tiny portion of a planet is required to support life, a so-called Goldilocks Edge or Great Prebiotic Spot. Astrobiologists often concern themselves with "micro-environments", noting that "we lack a fundamental understanding of how evolutionary forces, such as <a href="/wiki/Genetic_mutation" class="mw-redirect" title="Genetic mutation">mutation</a>, <a href="/wiki/Natural_selection" title="Natural selection">selection</a>, and <a href="/wiki/Genetic_drift" title="Genetic drift">genetic drift</a>, operate in micro-organisms that act on and respond to changing micro-environments."<sup id="cite_ref-77" class="reference"><a href="#cite_note-77"><span class="cite-bracket">[</span>71<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Extremophile" title="Extremophile">Extremophiles</a> are Earth organisms that live in niche environments under severe conditions generally considered <a href="https://en.wiktionary.org/wiki/inimical#Adjective" class="extiw" title="wikt:inimical">inimical</a> to life. Usually (although not always) unicellular, extremophiles include acutely <a href="/wiki/Alkaliphile" title="Alkaliphile">alkaliphilic</a> and <a href="/wiki/Acidophile_(organisms)" class="mw-redirect" title="Acidophile (organisms)">acidophilic</a> organisms and others that can survive water temperatures above 100 °C in <a href="/wiki/Hydrothermal_vents" class="mw-redirect" title="Hydrothermal vents">hydrothermal vents</a>. </p><p>The discovery of life in extreme conditions has complicated definitions of habitability, but also generated much excitement amongst researchers in greatly broadening the known range of conditions under which life can persist. For example, a planet that might otherwise be unable to support an atmosphere given the solar conditions in its vicinity, might be able to do so within a deep shadowed rift or volcanic cave.<sup id="cite_ref-78" class="reference"><a href="#cite_note-78"><span class="cite-bracket">[</span>72<span class="cite-bracket">]</span></a></sup> Similarly, craterous terrain might offer a refuge for primitive life. The <a href="/wiki/Lawn_Hill_crater" title="Lawn Hill crater">Lawn Hill crater</a> has been studied as an astrobiological analog, with researchers suggesting rapid sediment infill created a protected microenvironment for microbial organisms; similar conditions may have occurred over the geological history of <a href="/wiki/Mars" title="Mars">Mars</a>.<sup id="cite_ref-79" class="reference"><a href="#cite_note-79"><span class="cite-bracket">[</span>73<span class="cite-bracket">]</span></a></sup> </p><p>Earth environments that <i>cannot</i> support life are still instructive to astrobiologists in defining the limits of what organisms can endure. The heart of the <a href="/wiki/Atacama_Desert" title="Atacama Desert">Atacama Desert</a>, generally considered the driest place on Earth, appears unable to support life, and it has been subject to study by NASA and <a href="/wiki/European_Space_Agency" title="European Space Agency">ESA</a> for that reason: it provides a Mars analog and the moisture gradients along its edges are ideal for studying the boundary between sterility and habitability.<sup id="cite_ref-80" class="reference"><a href="#cite_note-80"><span class="cite-bracket">[</span>74<span class="cite-bracket">]</span></a></sup> The Atacama was the subject of study in 2003 that partly replicated experiments from the <a href="/wiki/Viking_(spacecraft)" class="mw-redirect" title="Viking (spacecraft)">Viking</a> landings on Mars in the 1970s; no <a href="/wiki/DNA" title="DNA">DNA</a> could be recovered from two soil samples, and incubation experiments were also negative for <a href="/wiki/Biosignature" title="Biosignature">biosignatures</a>.<sup id="cite_ref-81" class="reference"><a href="#cite_note-81"><span class="cite-bracket">[</span>75<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Ecological_factors">Ecological factors</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=13" title="Edit section: Ecological factors"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The two current ecological approaches for predicting the potential habitability use 19 or 20 environmental factors, with emphasis on water availability, temperature, presence of nutrients, an energy source, and protection from solar ultraviolet and <a href="/wiki/Cosmic_ray" title="Cosmic ray">galactic cosmic radiation</a>.<sup id="cite_ref-D.C.Golden_82-0" class="reference"><a href="#cite_note-D.C.Golden-82"><span class="cite-bracket">[</span>76<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Beaty_83-0" class="reference"><a href="#cite_note-Beaty-83"><span class="cite-bracket">[</span>77<span class="cite-bracket">]</span></a></sup> </p> <table class="wikitable"> <tbody><tr> <th style="align: center; background: lavender;" colspan="2"><b>Some habitability factors</b><sup id="cite_ref-Beaty_83-1" class="reference"><a href="#cite_note-Beaty-83"><span class="cite-bracket">[</span>77<span class="cite-bracket">]</span></a></sup> </th></tr> <tr> <td><a href="/wiki/Water_on_Mars" title="Water on Mars">Water</a></td> <td> <b>·</b>  Activity of liquid water <br />  <b>·</b>  Past or future liquid (ice) inventories <br />  <b>·</b>  <a href="/wiki/Salinity" title="Salinity">Salinity</a>, <a href="/wiki/PH" title="PH">pH</a>, and <a href="/wiki/Reduction_potential" title="Reduction potential">Eh</a> of available water </td></tr> <tr> <td>Chemical environment</td> <td><b>Nutrients:</b> <br />  <b>·</b>  C, H, N, O, P, S, essential metals, essential micronutrients <br />  <b>·</b> <a href="/wiki/Nitrogen_fixation" title="Nitrogen fixation">Fixed nitrogen</a> <br />  <b>·</b> Availability/mineralogy <br /> <b>Toxin abundances and lethality:</b> <br />  <b>·</b>  <a href="/wiki/Heavy_metal_(chemistry)" class="mw-redirect" title="Heavy metal (chemistry)">Heavy metals</a> (e.g. Zn, Ni, Cu, Cr, As, Cd, etc.; some are essential, but toxic at high levels) <br />  <b>·</b>  Globally distributed oxidizing soils </td></tr> <tr> <td>Energy for <a href="/wiki/Metabolism" title="Metabolism">metabolism</a></td> <td><b>Solar</b> (surface and near-surface only) <br /> <b>Geochemical</b> (subsurface) <br />  <b>·</b>  <a href="/wiki/Oxidizing_agent" title="Oxidizing agent">Oxidants</a> <br />  <b>·</b>  <a href="/wiki/Reducing_agent" title="Reducing agent">Reductants</a> <br />  <b>·</b>  <a href="/wiki/Redox_gradient" title="Redox gradient">Redox gradients</a> </td></tr> <tr> <td>Conducive <br /> physical conditions</td> <td> <b>·</b> Temperature <br />  <b>·</b> Extreme diurnal temperature fluctuations <br />  <b>·</b> Low pressure (is there a low-pressure threshold for terrestrial <a href="/wiki/Anaerobic_organism" title="Anaerobic organism">anaerobes</a>?) <br />  <b>·</b> Strong <a href="/wiki/Ultraviolet_germicidal_irradiation" title="Ultraviolet germicidal irradiation">ultraviolet germicidal irradiation</a> <br />  <b>·</b> <a href="/wiki/Cosmic_ray" title="Cosmic ray">Galactic cosmic radiation</a> and <a href="/wiki/Solar_proton_event" class="mw-redirect" title="Solar proton event">solar particle events</a> (long-term accumulated effects) <br />  <b>·</b>  Solar UV-induced volatile oxidants, e.g. <a href="/wiki/Superoxide" title="Superoxide">O <sub>2</sub><sup>−</sup></a>, O<sup>−</sup>, <a href="/wiki/Hydrogen_peroxide" title="Hydrogen peroxide">H<sub>2</sub>O<sub>2</sub></a>, O<sub>3</sub> <br />  <b>·</b> Climate and its variability (geography, seasons, diurnal, and eventually, obliquity variations) <br />  <b>·</b> Substrate (soil processes, rock microenvironments, dust composition, shielding) <br />  <b>·</b> High <a href="/wiki/Carbon_dioxide" title="Carbon dioxide">CO<sub>2</sub></a> concentrations in the global atmosphere <br />  <b>·</b> Transport (<a href="/wiki/Aeolian_processes" title="Aeolian processes">aeolian</a>, ground water flow, surface water, glacial) </td></tr></tbody></table> <div class="mw-heading mw-heading4"><h4 id="Classification_terminology">Classification terminology</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=14" title="Edit section: Classification terminology"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The Habitable Exoplanets Catalog<sup id="cite_ref-PHL_84-0" class="reference"><a href="#cite_note-PHL-84"><span class="cite-bracket">[</span>78<span class="cite-bracket">]</span></a></sup> uses estimated surface temperature range to classify exoplanets: </p> <ul><li><b>hypopsychroplanets</b> - very cold (<−50 °C)</li> <li><b>psychroplanets</b> - cold (<−50 to 0 °C)</li> <li><b>mesoplanets</b> - medium temperature (0–50 °C; not to be confused with the other definition of <a href="/wiki/Mesoplanet" title="Mesoplanet">mesoplanets</a>)</li> <li><b>thermoplanets</b> - hot (50–100 °C)</li> <li><b>hyperthermoplanets</b> - (> 100 °C)</li></ul> <p>Mesoplanets would be ideal for complex life, whereas hypopsychroplanets and hyperthermoplanets might only support <a href="/wiki/Extremophile" title="Extremophile">extremophilic</a> life. </p><p>The HEC uses the following terms to classify exoplanets in terms of mass, from least to greatest: asteroidan, mercurian, subterran, terran, superterran, neptunian, and jovian. </p> <div class="mw-heading mw-heading2"><h2 id="Alternative_star_systems">Alternative star systems</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=15" title="Edit section: Alternative star systems"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In determining the feasibility of extraterrestrial life, astronomers had long focused their attention on stars like the Sun. However, since planetary systems that resemble the Solar System are proving to be rare, they have begun to explore the possibility that life might form in systems very unlike the Sun's.<sup id="cite_ref-85" class="reference"><a href="#cite_note-85"><span class="cite-bracket">[</span>79<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-86" class="reference"><a href="#cite_note-86"><span class="cite-bracket">[</span>80<span class="cite-bracket">]</span></a></sup> </p><p>It is believed that <a href="/wiki/F-type_main-sequence_star" title="F-type main-sequence star">F</a>, <a href="/wiki/G-type_main-sequence_star" title="G-type main-sequence star">G</a>, <a href="/wiki/K-type_main-sequence_star" title="K-type main-sequence star">K</a> and <a href="/wiki/M-type_star" class="mw-redirect" title="M-type star">M</a>-type stars could host habitable exoplanets.<sup id="cite_ref-87" class="reference"><a href="#cite_note-87"><span class="cite-bracket">[</span>81<span class="cite-bracket">]</span></a></sup> About half of the stars similar in temperature to the Sun could have a rocky planet able to support liquid water on its surface, according to research using data from NASA's <a href="/wiki/Kepler_Space_Telescope" class="mw-redirect" title="Kepler Space Telescope">Kepler Space Telescope</a>.<sup id="cite_ref-88" class="reference"><a href="#cite_note-88"><span class="cite-bracket">[</span>82<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Binary_systems">Binary systems</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=16" title="Edit section: Binary systems"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Habitability_of_binary_star_systems" title="Habitability of binary star systems">Habitability of binary star systems</a></div> <p>Typical estimates often suggest that 50% or more of all stellar systems are <a href="/wiki/Binary_star" title="Binary star">binary systems</a>. This may be partly sample bias, as massive and bright stars tend to be in binaries and these are most easily observed and catalogued; a more precise analysis has suggested that the more common fainter stars are usually singular, and that up to two thirds of all stellar systems are therefore solitary.<sup id="cite_ref-89" class="reference"><a href="#cite_note-89"><span class="cite-bracket">[</span>83<span class="cite-bracket">]</span></a></sup> </p><p>The separation between stars in a binary may range from less than one <a href="/wiki/Astronomical_unit" title="Astronomical unit">astronomical unit</a> (AU, the average Earth–Sun distance) to several hundred. In latter instances, the gravitational effects will be negligible on a planet orbiting an otherwise suitable star and habitability potential will not be disrupted unless the orbit is highly eccentric (see <a href="/wiki/Nemesis_(hypothetical_star)" title="Nemesis (hypothetical star)">Nemesis</a>, for example). However, where the separation is significantly less, a stable orbit may be impossible. If a planet's distance to its primary exceeds about one fifth of the closest approach of the other star, orbital stability is not guaranteed.<sup id="cite_ref-90" class="reference"><a href="#cite_note-90"><span class="cite-bracket">[</span>84<span class="cite-bracket">]</span></a></sup> Whether planets might form in binaries at all had long been unclear, given that gravitational forces might interfere with planet formation. Theoretical work by <a href="/wiki/Alan_Boss" title="Alan Boss">Alan Boss</a> at the <a href="/wiki/Carnegie_Institution" class="mw-redirect" title="Carnegie Institution">Carnegie Institution</a> has shown that gas giants can form around stars in binary systems much as they do around solitary stars.<sup id="cite_ref-91" class="reference"><a href="#cite_note-91"><span class="cite-bracket">[</span>85<span class="cite-bracket">]</span></a></sup> </p><p>One study of <a href="/wiki/Alpha_Centauri" title="Alpha Centauri">Alpha Centauri</a>, the nearest star system to the Sun, suggested that binaries need not be discounted in the search for habitable planets. Centauri A and B have an 11 AU distance at closest approach (23 AU mean), and both should have stable habitable zones. A study of long-term orbital stability for simulated planets within the system shows that planets within approximately three AU of either star may remain rather stable (i.e. the <a href="/wiki/Semi-major_axis" class="mw-redirect" title="Semi-major axis">semi-major axis</a> deviating by less than 5% during 32 000 binary periods). The continuous habitable zone (CHZ for 4.5 billion years) for <a href="/wiki/Alpha_Centauri" title="Alpha Centauri">Centauri A</a> is conservatively estimated at 1.2 to 1.3 AU and Centauri B at 0.73 to 0.74—well within the stable region in both cases.<sup id="cite_ref-92" class="reference"><a href="#cite_note-92"><span class="cite-bracket">[</span>86<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Red_dwarf_systems">Red dwarf systems</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=17" title="Edit section: Red dwarf systems"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Habitability_of_red_dwarf_systems" title="Habitability of red dwarf systems">Habitability of red dwarf systems</a></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:BrownDwarfs_Comparison_01.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/23/BrownDwarfs_Comparison_01.png/300px-BrownDwarfs_Comparison_01.png" decoding="async" width="300" height="225" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/23/BrownDwarfs_Comparison_01.png/450px-BrownDwarfs_Comparison_01.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/23/BrownDwarfs_Comparison_01.png/600px-BrownDwarfs_Comparison_01.png 2x" data-file-width="3000" data-file-height="2250" /></a><figcaption>Relative star sizes and <a href="/wiki/Photosphere" title="Photosphere">photospheric temperatures</a>. Any planet around a red dwarf such as the one shown here (<a href="/wiki/Gliese_229A" class="mw-redirect" title="Gliese 229A">Gliese 229A</a>) would have to huddle close to achieve Earth-like temperatures, probably inducing tidal locking. See <a href="/wiki/Aurelia_and_Blue_Moon" class="mw-redirect" title="Aurelia and Blue Moon">Aurelia</a>. Credit: MPIA/V. Joergens.</figcaption></figure><p>M-type stars also considered possible hosts of habitable exoplanets, even those with flares such as Proxima b. Determining the habitability of <a href="/wiki/Red_dwarf" title="Red dwarf">red dwarf</a> stars could help determine how common life in the universe might be, as red dwarfs make up between 70 and 90% of all the stars in the galaxy. However, it is important to bear in mind that flare stars could greatly reduce the habitability of exoplanets by eroding their atmosphere.<sup id="cite_ref-93" class="reference"><a href="#cite_note-93"><span class="cite-bracket">[</span>87<span class="cite-bracket">]</span></a></sup> </p><div class="mw-heading mw-heading3"><h3 id="Size">Size</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=18" title="Edit section: Size"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Astronomers for many years ruled out red dwarfs as potential abodes for life. Their small size (from 0.08 to 0.45 solar masses) means that their <a href="/wiki/Nuclear_reaction" title="Nuclear reaction">nuclear reactions</a> proceed exceptionally slowly, and they emit very little light (from 3% of that produced by the Sun to as little as 0.01%). Any planet in orbit around a red dwarf would have to huddle very close to its parent star to attain Earth-like surface temperatures; from 0.3 AU (just inside the orbit of <a href="/wiki/Mercury_(planet)" title="Mercury (planet)">Mercury</a>) for a star like <a href="/wiki/Lacaille_8760" title="Lacaille 8760">Lacaille 8760</a>, to as little as 0.032 AU for a star like <a href="/wiki/Proxima_Centauri" title="Proxima Centauri">Proxima Centauri</a><sup id="cite_ref-94" class="reference"><a href="#cite_note-94"><span class="cite-bracket">[</span>88<span class="cite-bracket">]</span></a></sup> (such a world would have a year lasting just 6.3 days). At those distances, the star's gravity would cause tidal locking. One side of the planet would eternally face the star, while the other would always face away from it. The only ways in which potential life could avoid either an inferno or a deep freeze would be if the planet had an atmosphere thick enough to transfer the star's heat from the day side to the night side, or if there was a gas giant in the habitable zone, with a <a href="/wiki/Habitable_moon" class="mw-redirect" title="Habitable moon">habitable moon</a>, which would be locked to the planet instead of the star, allowing a more even distribution of radiation over the moon. It was long assumed that such a thick atmosphere would prevent sunlight from reaching the surface in the first place, preventing <a href="/wiki/Photosynthesis" title="Photosynthesis">photosynthesis</a>. </p> <figure class="mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Gliese_667_Cc_sunset.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/Gliese_667_Cc_sunset.jpg/300px-Gliese_667_Cc_sunset.jpg" decoding="async" width="300" height="200" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/Gliese_667_Cc_sunset.jpg/450px-Gliese_667_Cc_sunset.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5f/Gliese_667_Cc_sunset.jpg/600px-Gliese_667_Cc_sunset.jpg 2x" data-file-width="3000" data-file-height="2000" /></a><figcaption>An artist's impression of <a href="/wiki/GJ_667_Cc" class="mw-redirect" title="GJ 667 Cc">GJ 667 Cc</a>, a potentially habitable planet orbiting a red dwarf constituent in a <a href="/wiki/Star_system" title="Star system">trinary star system</a></figcaption></figure><p>This pessimism has been tempered by research. Studies by Robert Haberle and Manoj Joshi of <a href="/wiki/NASA" title="NASA">NASA</a>'s <a href="/wiki/Ames_Research_Center" title="Ames Research Center">Ames Research Center</a> in California have shown that a planet's atmosphere (assuming it included greenhouse gases <a href="/wiki/Carbon_dioxide" title="Carbon dioxide">CO<sub>2</sub></a> and <a href="/wiki/Water_(molecule)" class="mw-redirect" title="Water (molecule)">H<sub>2</sub>O</a>) need only be 100 millibars (0.10 atm), for the star's heat to be effectively carried to the night side.<sup id="cite_ref-95" class="reference"><a href="#cite_note-95"><span class="cite-bracket">[</span>89<span class="cite-bracket">]</span></a></sup> This is well within the levels required for photosynthesis, though water would still remain frozen on the dark side in some of their models. Martin Heath of <a href="/wiki/Greenwich_Community_College" class="mw-redirect" title="Greenwich Community College">Greenwich Community College</a>, has shown that seawater, too, could be effectively circulated without freezing solid if the ocean basins were deep enough to allow free flow beneath the night side's ice cap. Further research—including a consideration of the amount of photosynthetically active radiation—suggested that tidally locked planets in red dwarf systems might at least be habitable for higher plants.<sup id="cite_ref-96" class="reference"><a href="#cite_note-96"><span class="cite-bracket">[</span>90<span class="cite-bracket">]</span></a></sup> </p><div class="mw-heading mw-heading4"><h4 id="Other_factors_limiting_habitability">Other factors limiting habitability</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=19" title="Edit section: Other factors limiting habitability"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Size is not the only factor in making red dwarfs potentially unsuitable for life, however. On a red dwarf planet, photosynthesis on the night side would be impossible, since it would never see the sun. On the day side, because the sun does not rise or set, areas in the shadows of mountains would remain so forever. <a href="/wiki/Photosynthesis" title="Photosynthesis">Photosynthesis</a> as we understand it would be complicated by the fact that a red dwarf produces most of its radiation in the <a href="/wiki/Infrared" title="Infrared">infrared</a>, and on the Earth the process depends on visible light. There are potential positives to this scenario. Numerous terrestrial ecosystems rely on <a href="/wiki/Chemosynthesis" title="Chemosynthesis">chemosynthesis</a> rather than photosynthesis, for instance, which would be possible in a red dwarf system. A static primary star position removes the need for plants to steer leaves toward the sun, deal with changing shade/sun patterns, or change from photosynthesis to stored energy during night. Because of the lack of a day-night cycle, including the weak light of morning and evening, far more energy would be available at a given radiation level. </p><p>Red dwarfs are far more variable and violent than their more stable, larger cousins. Often they are covered in <a href="/wiki/Starspot" title="Starspot">starspots</a> that can dim their emitted light by up to 40% for months at a time, while at other times they emit gigantic flares that can double their brightness in a matter of minutes.<sup id="cite_ref-97" class="reference"><a href="#cite_note-97"><span class="cite-bracket">[</span>91<span class="cite-bracket">]</span></a></sup> Such variation would be very damaging for life, as it would not only destroy any complex organic molecules that could possibly form biological precursors, but also because it would blow off sizeable portions of the planet's atmosphere. </p><p>For a planet around a red dwarf star to support life, it would require a rapidly rotating magnetic field to protect it from the flares. A tidally locked planet rotates only very slowly, and so cannot produce a geodynamo at its core. The violent flaring period of a red dwarf's life cycle is estimated to only last roughly the first 1.2 billion years of its existence. If a planet forms far away from a red dwarf so as to avoid tidal locking, and then migrates into the star's habitable zone after this turbulent initial period, it is possible that life may have a chance to develop.<sup id="cite_ref-98" class="reference"><a href="#cite_note-98"><span class="cite-bracket">[</span>92<span class="cite-bracket">]</span></a></sup> However, observations of the 7 to 12-billion year old <a href="/wiki/Barnard%27s_Star" title="Barnard's Star">Barnard's Star</a> showcase that even old red dwarfs can have significant flare activity. Barnard's Star was long assumed to have little activity, but in 1998 astronomers observed an intense <a href="/wiki/Stellar_flare" class="mw-redirect" title="Stellar flare">stellar flare</a>, showing that it is a <a href="/wiki/Flare_star" title="Flare star">flare star</a>.<sup id="cite_ref-Flare_99-0" class="reference"><a href="#cite_note-Flare-99"><span class="cite-bracket">[</span>93<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Longevity_and_ubiquity">Longevity and ubiquity</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=20" title="Edit section: Longevity and ubiquity"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Red dwarfs have one advantage over other stars as abodes for life: far greater longevity. It took 4.5 billion years before humanity appeared on Earth, and life as we know it will see suitable conditions for 1<sup id="cite_ref-100" class="reference"><a href="#cite_note-100"><span class="cite-bracket">[</span>94<span class="cite-bracket">]</span></a></sup> to 2.3<sup id="cite_ref-pnas1_24_9576_101-0" class="reference"><a href="#cite_note-pnas1_24_9576-101"><span class="cite-bracket">[</span>95<span class="cite-bracket">]</span></a></sup> <span class="nowrap">billion years</span> more. Red dwarfs, by contrast, could live for trillions of years because their nuclear reactions are far slower than those of larger stars, meaning that life would have longer to evolve and survive. </p><p>While the likelihood of finding a planet in the habitable zone around any specific red dwarf is slight, the total amount of habitable zone around all red dwarfs combined is equal to the total amount around Sun-like stars given their ubiquity.<sup id="cite_ref-102" class="reference"><a href="#cite_note-102"><span class="cite-bracket">[</span>96<span class="cite-bracket">]</span></a></sup> Furthermore, this total amount of habitable zone will last longer, because red dwarf stars live for hundreds of billions of years or even longer on the main sequence.<sup id="cite_ref-Red_Dwarfs_Universe_Today_103-0" class="reference"><a href="#cite_note-Red_Dwarfs_Universe_Today-103"><span class="cite-bracket">[</span>97<span class="cite-bracket">]</span></a></sup> However, combined with the above disadvantages, it is more likely that red dwarf stars would remain habitable longer to microbes, while the shorter-lived yellow dwarf stars, like the Sun, would remain habitable longer to animals. </p> <div class="mw-heading mw-heading3"><h3 id="Massive_stars">Massive stars</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=21" title="Edit section: Massive stars"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Recent research suggests that very large stars, greater than ~100 solar masses, could have planetary systems consisting of hundreds of Mercury-sized planets within the habitable zone. Such systems could also contain <a href="/wiki/Brown_dwarfs" class="mw-redirect" title="Brown dwarfs">brown dwarfs</a> and low-mass stars (~0.1–0.3 solar masses).<sup id="cite_ref-104" class="reference"><a href="#cite_note-104"><span class="cite-bracket">[</span>98<span class="cite-bracket">]</span></a></sup> However the very short lifespans of stars of more than a few solar masses would scarcely allow time for a planet to cool, let alone the time needed for a stable biosphere to develop. Massive stars are thus eliminated as possible abodes for life.<sup id="cite_ref-105" class="reference"><a href="#cite_note-105"><span class="cite-bracket">[</span>99<span class="cite-bracket">]</span></a></sup> </p><p>However, a massive-star system could be a progenitor of life in another way – the <a href="/wiki/Supernova" title="Supernova">supernova</a> explosion of the massive star in the central part of the system. This supernova will disperse heavier elements throughout its vicinity, created during the phase when the massive star has moved off of the main sequence, and the systems of the potential low-mass stars (which are still on the main sequence) within the former massive-star system may be enriched with the relatively large supply of the heavy elements so close to a supernova explosion. However, this states nothing about what types of planets would form as a result of the supernova material, or what their habitability potential would be. </p> <div class="mw-heading mw-heading3"><h3 id="Neutron_stars">Neutron stars</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=22" title="Edit section: Neutron stars"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Habitability_of_neutron_star_systems" title="Habitability of neutron star systems">Habitability of neutron star systems</a></div> <div class="mw-heading mw-heading3"><h3 id="Post-main_sequence_stars">Post-main sequence stars</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=23" title="Edit section: Post-main sequence stars"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Red_giant#Prospects_for_habitability" title="Red giant">Red giant § Prospects for habitability</a></div> <div class="mw-heading mw-heading2"><h2 id="Four_classes_of_habitable_planets_based_on_water">Four classes of habitable planets based on water</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=24" title="Edit section: Four classes of habitable planets based on water"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In a review of the factors which are important for the evolution of habitable Earth-sized planets, Lammer et al. proposed a classification of four water-dependent habitat types:<sup id="cite_ref-Review_2009_20-6" class="reference"><a href="#cite_note-Review_2009-20"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Forget_2013_106-0" class="reference"><a href="#cite_note-Forget_2013-106"><span class="cite-bracket">[</span>100<span class="cite-bracket">]</span></a></sup> </p><p><b>Class I</b> habitats are planetary bodies on which stellar and geophysical conditions allow liquid water to be available at the surface, along with sunlight, so that complex <a href="/wiki/Multicellular_organism" title="Multicellular organism">multicellular organisms</a> may originate. </p><p><b>Class II</b> habitats include bodies which initially enjoy Earth-like conditions, but do not keep their ability to sustain liquid water on their surface due to stellar or geophysical conditions. Mars, and possibly Venus are examples of this class where complex life forms may not develop. </p><p><b>Class III</b> habitats are planetary bodies where liquid water oceans exist below the surface, where they can interact directly with a silicate-rich <a href="/wiki/Planetary_core" title="Planetary core">core</a>. </p> <dl><dd>Such a situation can be expected on water-rich planets located too far from their star to allow surface liquid water, but on which subsurface water is in liquid form because of the <a href="/wiki/Geothermal_heat" class="mw-redirect" title="Geothermal heat">geothermal heat</a>. Two examples of such an environment are <a href="/wiki/Europa_(moon)" title="Europa (moon)">Europa</a> and <a href="/wiki/Enceladus_(moon)" class="mw-redirect" title="Enceladus (moon)">Enceladus</a>. In such worlds, not only is light not available as an energy source, but the organic material brought by meteorites (thought to have been necessary to start life in some scenarios) may not easily reach the liquid water. If a planet can only harbor life below its surface, the <a href="/wiki/Biosphere" title="Biosphere">biosphere</a> would not likely modify the whole planetary environment in an observable way, thus, detecting its presence on an exoplanet would be extremely difficult.</dd></dl> <p><b>Class IV</b> habitats have liquid water layers between two ice layers, or liquids above ice. </p> <dl><dd>If the water layer is thick enough, water at its base will be in solid phase (ice polymorphs) because of the high pressure. <a href="/wiki/Ganymede_(moon)" title="Ganymede (moon)">Ganymede</a> and <a href="/wiki/Callisto_(moon)" title="Callisto (moon)">Callisto</a> are likely examples of this class. Their oceans are thought to be enclosed between thick ice layers. In such conditions, the emergence of even simple life forms may be very difficult because the necessary ingredients for life will likely be completely diluted.</dd></dl> <div class="mw-heading mw-heading2"><h2 id="The_galactic_neighborhood">The galactic neighborhood</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=25" title="Edit section: The galactic neighborhood"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Along with the characteristics of planets and their star systems, the wider galactic environment may also impact habitability. Scientists considered the possibility that particular areas of galaxies (<a href="/wiki/Galactic_habitable_zone" title="Galactic habitable zone">galactic habitable zones</a>) are better suited to life than others; the Solar System, in the <a href="/wiki/Orion_Arm" title="Orion Arm">Orion Arm</a>, on the Milky Way galaxy's edge is considered to be in a life-favorable spot:<sup id="cite_ref-107" class="reference"><a href="#cite_note-107"><span class="cite-bracket">[</span>101<span class="cite-bracket">]</span></a></sup> </p> <ul><li>It is not in a <a href="/wiki/Globular_cluster" title="Globular cluster">globular cluster</a> where immense star densities are inimical to life, given excessive radiation and gravitational disturbance. Globular clusters are also primarily composed of older, probably metal-poor, stars. Furthermore, in globular clusters, the great ages of the stars would mean a large amount of <a href="/wiki/Stellar_evolution" title="Stellar evolution">stellar evolution</a> by the host or other nearby stars, which due to their proximity may cause extreme harm to life on any planets, provided that they can form.</li> <li>It is not near an active <a href="/wiki/Gamma_ray" title="Gamma ray">gamma ray</a> source.</li> <li>It is not near the galactic center where once again star densities increase the likelihood of ionizing radiation (e.g., from <a href="/wiki/Magnetar" title="Magnetar">magnetars</a> and <a href="/wiki/Supernovae" class="mw-redirect" title="Supernovae">supernovae</a>). The <a href="/wiki/Supermassive_black_hole" title="Supermassive black hole">supermassive black holes</a> at the centers of galaxies may also prove a danger to any nearby bodies.</li> <li>The circular orbit of the Sun around the galactic center keeps it out of the way of the galaxy's spiral arms where intense radiation and gravitation may again lead to disruption.<sup id="cite_ref-108" class="reference"><a href="#cite_note-108"><span class="cite-bracket">[</span>102<span class="cite-bracket">]</span></a></sup></li></ul> <p>Thus, relative isolation is ultimately what a life-bearing system needs. If the Sun were crowded amongst other systems, the chance of being fatally close to dangerous radiation sources would increase significantly. Further, close neighbors might disrupt the stability of various orbiting bodies such as <a href="/wiki/Oort_cloud" title="Oort cloud">Oort cloud</a> and <a href="/wiki/Kuiper_belt" title="Kuiper belt">Kuiper belt</a> objects, which can bring catastrophe if knocked into the inner Solar System. </p><p>While stellar crowding proves disadvantageous to habitability, so too does extreme isolation. A star as metal-rich as the Sun would probably not have formed in the very outermost regions of the Milky Way given a decline in the relative abundance of metals and a general lack of star formation. Thus, a "suburban" location, such as the Solar System enjoys, is preferable to a Galaxy's center or farthest reaches.<sup id="cite_ref-109" class="reference"><a href="#cite_note-109"><span class="cite-bracket">[</span>103<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Other_considerations">Other considerations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=26" title="Edit section: Other considerations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Alternative_biochemistries">Alternative biochemistries</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=27" title="Edit section: Alternative biochemistries"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Hypothetical_types_of_biochemistry" title="Hypothetical types of biochemistry">Hypothetical types of biochemistry</a></div> <p>While most investigations of extraterrestrial life start with the assumption that advanced life-forms must have similar requirements for life as on Earth, the hypothesis of <a href="/wiki/Hypothetical_types_of_biochemistry" title="Hypothetical types of biochemistry">other types of biochemistry</a> suggests the possibility of lifeforms evolving around a different metabolic mechanism. In <i><a href="/wiki/Evolving_the_Alien" title="Evolving the Alien">Evolving the Alien</a></i>, <a href="/wiki/Biologist" title="Biologist">biologist</a> <a href="/wiki/Jack_Cohen_(scientist)" class="mw-redirect" title="Jack Cohen (scientist)">Jack Cohen</a> and <a href="/wiki/Mathematician" title="Mathematician">mathematician</a> <a href="/wiki/Ian_Stewart_(mathematician)" title="Ian Stewart (mathematician)">Ian Stewart</a> argue <a href="/wiki/Astrobiology" title="Astrobiology">astrobiology</a>, based on the <a href="/wiki/Rare_Earth_hypothesis" title="Rare Earth hypothesis">Rare Earth hypothesis</a>, is restrictive and unimaginative. They suggest that <a href="/wiki/Earth_analog" title="Earth analog">Earth-like planets</a> may be very rare, but non-carbon-based complex life could possibly emerge in other environments. The most frequently mentioned alternative to carbon is <a href="/wiki/Silicon-based_life" class="mw-redirect" title="Silicon-based life">silicon-based life</a>, while <a href="/wiki/Ammonia-based_life#Ammonia" class="mw-redirect" title="Ammonia-based life">ammonia</a> and <a href="/wiki/Hydrocarbons" class="mw-redirect" title="Hydrocarbons">hydrocarbons</a> are sometimes suggested as <a href="/wiki/Hypothetical_types_of_biochemistry#Non-water_solvents" title="Hypothetical types of biochemistry">alternative solvents</a> to water. The astrobiologist <a href="/wiki/Dirk_Schulze-Makuch" title="Dirk Schulze-Makuch">Dirk Schulze-Makuch</a> and other scientists have proposed a Planet Habitability Index whose criteria include "potential for holding a liquid solvent" that is not necessarily restricted to water.<sup id="cite_ref-110" class="reference"><a href="#cite_note-110"><span class="cite-bracket">[</span>104<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-111" class="reference"><a href="#cite_note-111"><span class="cite-bracket">[</span>105<span class="cite-bracket">]</span></a></sup> </p><p>More speculative ideas have focused on bodies altogether different from Earth-like planets. Astronomer <a href="/wiki/Frank_Drake" title="Frank Drake">Frank Drake</a>, a well-known proponent of the search for <a href="/wiki/Extraterrestrial_life" title="Extraterrestrial life">extraterrestrial life</a>, imagined life on a <a href="/wiki/Neutron_star" title="Neutron star">neutron star</a>: submicroscopic "nuclear molecules" combining to form creatures with a life cycle millions of times quicker than Earth life.<sup id="cite_ref-112" class="reference"><a href="#cite_note-112"><span class="cite-bracket">[</span>106<span class="cite-bracket">]</span></a></sup> Called "imaginative and tongue-in-cheek", the idea gave rise to science fiction depictions.<sup id="cite_ref-113" class="reference"><a href="#cite_note-113"><span class="cite-bracket">[</span>107<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Carl_Sagan" title="Carl Sagan">Carl Sagan</a>, another optimist with regards to extraterrestrial life, considered the possibility of organisms that are always airborne within the high atmosphere of Jupiter in a 1976 paper.<sup id="cite_ref-Sagan,_C._1976_42-1" class="reference"><a href="#cite_note-Sagan,_C._1976-42"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Darling_43-1" class="reference"><a href="#cite_note-Darling-43"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> Cohen and Stewart also envisioned life in both a solar environment and in the atmosphere of a gas giant. </p> <div class="mw-heading mw-heading3"><h3 id=""Good_Jupiters""><span id=".22Good_Jupiters.22"></span>"Good Jupiters"</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=28" title="Edit section: "Good Jupiters""><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>"Good Jupiters" are gas giants, like the Solar System's <a href="/wiki/Jupiter" title="Jupiter">Jupiter</a>, that orbit their stars in circular orbits far enough away from the habitable zone not to disturb it but close enough to "protect" terrestrial planets in closer orbit in two critical ways. First, they help to stabilize the orbits, and thereby the climates of the inner planets. Second, they keep the inner stellar system relatively free of comets and asteroids that could cause devastating impacts.<sup id="cite_ref-114" class="reference"><a href="#cite_note-114"><span class="cite-bracket">[</span>108<span class="cite-bracket">]</span></a></sup> Jupiter orbits the Sun at about five times the distance between the Earth and the Sun. This is the rough distance we should expect to find good Jupiters elsewhere. Jupiter's "caretaker" role was dramatically illustrated in 1994 when <a href="/wiki/Comet_Shoemaker%E2%80%93Levy_9" title="Comet Shoemaker–Levy 9">Comet Shoemaker–Levy 9</a> impacted the giant.<sup class="noprint Inline-Template" style="margin-left:0.1em; white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Manual_of_Style/Words_to_watch#Unsupported_attributions" title="Wikipedia:Manual of Style/Words to watch"><span title="The material near this tag may use weasel words or too-vague attribution. (April 2024)">according to whom?</span></a></i>]</sup> </p><p>However, the evidence is not quite so clear. Research has shown that Jupiter's role in determining the rate at which objects hit Earth is significantly more complicated than once thought.<sup id="cite_ref-115" class="reference"><a href="#cite_note-115"><span class="cite-bracket">[</span>109<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-116" class="reference"><a href="#cite_note-116"><span class="cite-bracket">[</span>110<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-117" class="reference"><a href="#cite_note-117"><span class="cite-bracket">[</span>111<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-118" class="reference"><a href="#cite_note-118"><span class="cite-bracket">[</span>112<span class="cite-bracket">]</span></a></sup> </p><p>The role of Jupiter in the early history of the Solar System is somewhat better established, and the source of significantly less debate.<sup id="cite_ref-119" class="reference"><a href="#cite_note-119"><span class="cite-bracket">[</span>113<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-120" class="reference"><a href="#cite_note-120"><span class="cite-bracket">[</span>114<span class="cite-bracket">]</span></a></sup> Early in the Solar System's history, Jupiter is accepted as having played an important role in the hydration of our planet: it increased the eccentricity of <a href="/wiki/Asteroid_belt" title="Asteroid belt">asteroid belt</a> orbits and enabled many to cross Earth's orbit and supply the planet with important volatiles such as water and carbon dioxide. Before Earth reached half its present mass, icy bodies from the Jupiter–Saturn region and small bodies from the primordial asteroid belt supplied water to the Earth due to the gravitational scattering of Jupiter and, to a lesser extent, <a href="/wiki/Saturn" title="Saturn">Saturn</a>.<sup id="cite_ref-121" class="reference"><a href="#cite_note-121"><span class="cite-bracket">[</span>115<span class="cite-bracket">]</span></a></sup> Thus, while the gas giants are now helpful protectors, they were once suppliers of critical habitability material. </p><p>In contrast, Jupiter-sized bodies that orbit too close to the habitable zone but not in it (as in <a href="/wiki/47_Ursae_Majoris" title="47 Ursae Majoris">47 Ursae Majoris</a>), or have a highly elliptical orbit that crosses the habitable zone (like <a href="/wiki/16_Cygni" title="16 Cygni">16 Cygni B</a>) make it very difficult for an independent Earth-like planet to exist in the system. See the discussion of a <a href="#A_stable_habitable_zone">stable habitable zone</a> above. However, during the process of migrating into a habitable zone, a Jupiter-size planet may capture a terrestrial planet as a moon. Even if such a planet is initially loosely bound and following a strongly inclined orbit, gravitational interactions with the star can stabilize the new moon into a close, circular orbit that is coplanar with the planet's orbit around the star.<sup id="cite_ref-122" class="reference"><a href="#cite_note-122"><span class="cite-bracket">[</span>116<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Life's_impact_on_habitability"><span id="Life.27s_impact_on_habitability"></span>Life's impact on habitability</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=29" title="Edit section: Life's impact on habitability"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A supplement to the factors that support life's emergence is the notion that life itself, once formed, becomes a habitability factor in its own right. An important Earth example was the production of molecular oxygen gas (<span class="chemf nowrap">O<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">2</sub></span></span></span>) by ancient <a href="/wiki/Cyanobacteria" title="Cyanobacteria">cyanobacteria</a>, and eventually photosynthesizing plants, leading to a radical change in the composition of Earth's atmosphere. This environmental change is called the <a href="/wiki/Great_Oxidation_Event" title="Great Oxidation Event">Great Oxidation Event</a>. This oxygen proved fundamental to the <a href="/wiki/Respiration_(physiology)" title="Respiration (physiology)">respiration</a> of later animal species. The <a href="/wiki/Gaia_hypothesis" title="Gaia hypothesis">Gaia hypothesis</a>, a scientific model of the geo-biosphere pioneered by <a href="/wiki/James_Lovelock" title="James Lovelock">James Lovelock</a> in 1975, argues that life as a whole fosters and maintains suitable conditions for itself by helping to create a planetary environment suitable for its continuity. Similarly, <a href="/wiki/David_Grinspoon" title="David Grinspoon">David Grinspoon</a> has suggested a "living worlds hypothesis" in which our understanding of what constitutes habitability cannot be separated from life already extant on a planet. Planets that are geologically and meteorologically alive are much more likely to be biologically alive as well and "a planet and its life will co-evolve."<sup id="cite_ref-123" class="reference"><a href="#cite_note-123"><span class="cite-bracket">[</span>117<span class="cite-bracket">]</span></a></sup> This is the basis of <a href="/wiki/Earth_system_science" title="Earth system science">Earth system science</a>. </p> <div class="mw-heading mw-heading3"><h3 id="The_role_of_chance">The role of chance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=30" title="Edit section: The role of chance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In 2020, a computer simulation of the evolution of planetary climates over 3 billion years suggested that feedback is a necessary but insufficient condition for preventing planets from ever becoming too hot or cold for life. Chance also plays a crucial role.<sup id="cite_ref-124" class="reference"><a href="#cite_note-124"><span class="cite-bracket">[</span>118<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-10.1038/s43247-020-00057-8_125-0" class="reference"><a href="#cite_note-10.1038/s43247-020-00057-8-125"><span class="cite-bracket">[</span>119<span class="cite-bracket">]</span></a></sup> Related considerations include yet unknown factors influencing the thermal habitability of planets such as "feedback mechanism (or mechanisms) that prevents the climate ever wandering to fatal temperatures".<sup id="cite_ref-126" class="reference"><a href="#cite_note-126"><span class="cite-bracket">[</span>120<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=31" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 30em;"> <ul><li><a href="/wiki/Astrobotany" title="Astrobotany">Astrobotany</a> – Study of plants grown in spacecraft</li> <li><a href="/wiki/Habitable_zone" title="Habitable zone">Habitable zone</a> – Orbits where planets may have liquid surface water</li> <li><a href="/wiki/Darwin_(spacecraft)" title="Darwin (spacecraft)">Darwin (spacecraft)</a> – 2007 European study concept of an array of space observatories</li> <li><a href="/wiki/Earth_analog" title="Earth analog">Earth analog</a> – Planet with environment similar to Earth's</li> <li><a href="/wiki/Exoplanet" title="Exoplanet">Exoplanet</a> – Planet outside the Solar System</li> <li><a href="/wiki/Exoplanet_orbital_and_physical_parameters" title="Exoplanet orbital and physical parameters">Exoplanetology</a></li> <li><a href="/wiki/Extraterrestrial_liquid_water" title="Extraterrestrial liquid water">Extraterrestrial liquid water</a> – Liquid water naturally occurring outside Earth</li> <li><a href="/wiki/Habitability_of_natural_satellites" title="Habitability of natural satellites">Habitability of natural satellites</a> – Measure of the potential of natural satellites to have environments hospitable to life</li> <li><a href="/wiki/Habitability_of_red_dwarf_systems" title="Habitability of red dwarf systems">Habitability of red dwarf systems</a> – Possible factors for life around red dwarf stars</li> <li><i><a href="/wiki/Habitable_Planets_for_Man" title="Habitable Planets for Man">Habitable Planets for Man</a></i></li> <li><a href="/wiki/List_of_potentially_habitable_exoplanets" title="List of potentially habitable exoplanets">List of potentially habitable exoplanets</a></li> <li><a href="/wiki/Neocatastrophism" title="Neocatastrophism">Neocatastrophism</a> – Hypothesis for lack of detected aliens</li> <li><a href="/wiki/Rare_Earth_hypothesis" title="Rare Earth hypothesis">Rare Earth hypothesis</a> – Hypothesis that complex extraterrestrial life is improbable and extremely rare</li> <li><a href="/wiki/Space_colonization" title="Space colonization">Space colonization</a> – Concept of permanent human habitation outside of Earth</li> <li><a href="/wiki/Superhabitable_planet" class="mw-redirect" title="Superhabitable planet">Superhabitable planet</a> – Hypothetical type of planet or moon that may be better-suited for life than Earth<span style="display:none" class="category-annotation-with-redirected-description">Pages displaying short descriptions of redirect targets</span></li> <li><a href="/wiki/Terraforming" title="Terraforming">Terraforming</a> – Hypothetical planetary engineering process</li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=32" title="Edit section: Notes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-lower-alpha"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text">This article is an analysis of planetary habitability from the perspective of contemporary physical science. A historical viewpoint on the possibility of habitable planets can be found at <a href="/wiki/Beliefs_in_extraterrestrial_life" class="mw-redirect" title="Beliefs in extraterrestrial life">Beliefs in extraterrestrial life</a> and <a href="/wiki/Cosmic_pluralism" title="Cosmic pluralism">Cosmic pluralism</a>. For a discussion of the probability of alien life see the <a href="/wiki/Drake_equation" title="Drake equation">Drake equation</a> and <a href="/wiki/Fermi_paradox" title="Fermi paradox">Fermi paradox</a>. Habitable planets are also a staple of fiction; see <a href="/wiki/Planets_in_science_fiction" class="mw-redirect" title="Planets in science fiction">Planets in science fiction</a>.</span> </li> <li id="cite_note-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-25">^</a></b></span> <span class="reference-text">Life appears to <a href="/wiki/Timeline_of_evolution" class="mw-redirect" title="Timeline of evolution">have emerged</a> on Earth approximately 500 million years after the planet's formation. "A" class stars (which shine for between 600 million and 1.2 billion years) and the very latest of the "B" class stars (which shine 10+ million to 600 million) fall within this window. At least theoretically life could emerge in such systems but it would almost certainly not reach a sophisticated level given these time-frames and the fact that increases in luminosity would occur quite rapidly. Life around "O" class stars is exceptionally unlikely, as they shine for less than ten million years.</span> </li> <li id="cite_note-44"><span class="mw-cite-backlink"><b><a href="#cite_ref-44">^</a></b></span> <span class="reference-text">In <i><a href="/wiki/Evolving_the_Alien" title="Evolving the Alien">Evolving the Alien</a></i>, <a href="/wiki/Jack_Cohen_(scientist)" class="mw-redirect" title="Jack Cohen (scientist)">Jack Cohen</a> and <a href="/wiki/Ian_Stewart_(mathematician)" title="Ian Stewart (mathematician)">Ian Stewart</a> evaluate plausible scenarios in which life might form in the cloud-tops of Jovian planets. Similarly, <a href="/wiki/Carl_Sagan" title="Carl Sagan">Carl Sagan</a> suggested that the clouds of <a href="/wiki/Jupiter" title="Jupiter">Jupiter</a> might host life.<sup id="cite_ref-Sagan,_C._1976_42-0" class="reference"><a href="#cite_note-Sagan,_C._1976-42"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Darling_43-0" class="reference"><a href="#cite_note-Darling-43"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup></span> </li> <li id="cite_note-50"><span class="mw-cite-backlink"><b><a href="#cite_ref-50">^</a></b></span> <span class="reference-text">There is an emerging consensus that single-celled micro-organisms may in fact be common in the universe, especially since Earth's <a href="/wiki/Extremophile" title="Extremophile">extremophiles</a> flourish in environments that were once considered hostile to life. The potential occurrence of complex multi-celled life remains much more controversial. In their work <i><a href="/wiki/Rare_Earth_hypothesis" title="Rare Earth hypothesis">Rare Earth: Why Complex Life Is Uncommon in the Universe</a></i>, <a href="/wiki/Peter_Ward_(paleontologist)" title="Peter Ward (paleontologist)">Peter Ward</a> and <a href="/wiki/Donald_E._Brownlee" title="Donald E. Brownlee">Donald Brownlee</a> argue that microbial life is probably widespread while complex life is very rare and perhaps even unique to Earth. Current knowledge of Earth's history partly buttresses this theory: multi-celled organisms are believed to have emerged at the time of the <a href="/wiki/Cambrian_explosion" title="Cambrian explosion">Cambrian explosion</a> close to 600 million years ago, but more than 3 billion years after life first appeared. That Earth life remained unicellular for so long underscores that the decisive step toward complex organisms need not necessarily occur.</span> </li> <li id="cite_note-54"><span class="mw-cite-backlink"><b><a href="#cite_ref-54">^</a></b></span> <span class="reference-text">There is a "mass-gap" in the Solar System between Earth and the two smallest gas giants, <a href="/wiki/Uranus" title="Uranus">Uranus</a> and <a href="/wiki/Neptune" title="Neptune">Neptune</a>, which are 13 and 17 Earth masses. This is probably just chance, as there is no geophysical barrier to the formation of intermediate bodies (see for instance <a href="/wiki/OGLE-2005-BLG-390Lb" title="OGLE-2005-BLG-390Lb">OGLE-2005-BLG-390Lb</a> and <a href="/wiki/Super-Earth" title="Super-Earth">Super-Earth</a>) and we should expect to find planets throughout the galaxy between two and twelve Earth masses. If the star system is otherwise favorable, such planets would be good candidates for life as they would be large enough to remain internally dynamic and to retain an atmosphere for billions of years but not so large as to accrete a gaseous shell which limits the possibility of life formation.</span> </li> <li id="cite_note-67"><span class="mw-cite-backlink"><b><a href="#cite_ref-67">^</a></b></span> <span class="reference-text">According to prevailing theory, the formation of the Moon commenced when a Mars-sized body struck the Earth in a glancing collision late in its formation, and the ejected material coalesced and fell into orbit (see <a href="/wiki/Giant_impact_hypothesis" class="mw-redirect" title="Giant impact hypothesis">giant impact hypothesis</a>). In <i>Rare Earth</i> Ward and Brownlee emphasize that such impacts ought to be rare, reducing the probability of other Earth-Moon type systems and hence the probability of other habitable planets. Other moon formation processes are possible, however, and the proposition that a planet may be habitable in the absence of a moon has not been disproven.</span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=33" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-NASA-20150407-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-NASA-20150407_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-NASA-20150407_1-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFDychesChou2015" class="citation web cs1">Dyches, Preston; Chou, Felcia (7 April 2015). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150410113514/http://www.nasa.gov/jpl/the-solar-system-and-beyond-is-awash-in-water/">"The Solar System and Beyond is Awash in Water"</a>. <i><a href="/wiki/NASA" title="NASA">NASA</a></i>. Archived from <a rel="nofollow" class="external text" href="https://www.nasa.gov/jpl/the-solar-system-and-beyond-is-awash-in-water/">the original</a> on 10 April 2015<span class="reference-accessdate">. Retrieved <span class="nowrap">8 April</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=NASA&rft.atitle=The+Solar+System+and+Beyond+is+Awash+in+Water&rft.date=2015-04-07&rft.aulast=Dyches&rft.aufirst=Preston&rft.au=Chou%2C+Felcia&rft_id=http%3A%2F%2Fwww.nasa.gov%2Fjpl%2Fthe-solar-system-and-beyond-is-awash-in-water%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-NASA_strategy_2015-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-NASA_strategy_2015_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-NASA_strategy_2015_2-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-NASA_strategy_2015_2-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-NASA_strategy_2015_2-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-NASA_strategy_2015_2-4"><sup><i><b>e</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNASA2015" class="citation cs2">NASA (October 2015), <a rel="nofollow" class="external text" href="https://web.archive.org/web/20161118105817/https://nai.nasa.gov/media/medialibrary/2016/04/NASA_Astrobiology_Strategy_2015_FINAL_041216.pdf"><i>NASA Astrobiology Strategy</i></a> <span class="cs1-format">(PDF)</span>, archived from <a rel="nofollow" class="external text" href="https://nai.nasa.gov/media/medialibrary/2016/04/NASA_Astrobiology_Strategy_2015_FINAL_041216.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 18 November 2016</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=NASA+Astrobiology+Strategy&rft.date=2015-10&rft.au=NASA&rft_id=https%3A%2F%2Fnai.nasa.gov%2Fmedia%2Fmedialibrary%2F2016%2F04%2FNASA_Astrobiology_Strategy_2015_FINAL_041216.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-Seager_2013-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-Seager_2013_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Seager_2013_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSeager2013" class="citation journal cs1">Seager, Sara (2013). "Exoplanet Habitability". <i>Science</i>. <b>340</b> (577): 577–581. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2013Sci...340..577S">2013Sci...340..577S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.1232226">10.1126/science.1232226</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/23641111">23641111</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:206546351">206546351</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science&rft.atitle=Exoplanet+Habitability&rft.volume=340&rft.issue=577&rft.pages=577-581&rft.date=2013&rft_id=info%3Adoi%2F10.1126%2Fscience.1232226&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A206546351%23id-name%3DS2CID&rft_id=info%3Apmid%2F23641111&rft_id=info%3Abibcode%2F2013Sci...340..577S&rft.aulast=Seager&rft.aufirst=Sara&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCostanzaBernard1995" class="citation journal cs1">Costanza, Robert; Bernard, C. Patten (December 1995). "Defining and predicting sustainability". <i>Ecological Economics</i>. <b>15</b> (3): 193–196. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1995EcoEc..15..193C">1995EcoEc..15..193C</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2F0921-8009%2895%2900048-8">10.1016/0921-8009(95)00048-8</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Ecological+Economics&rft.atitle=Defining+and+predicting+sustainability&rft.volume=15&rft.issue=3&rft.pages=193-196&rft.date=1995-12&rft_id=info%3Adoi%2F10.1016%2F0921-8009%2895%2900048-8&rft_id=info%3Abibcode%2F1995EcoEc..15..193C&rft.aulast=Costanza&rft.aufirst=Robert&rft.au=Bernard%2C+C.+Patten&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-NASA1-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-NASA1_5-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20110117011137/http://astrobiology.arc.nasa.gov/roadmap/g1.html">"Goal 1: Understand the nature and distribution of habitable environments in the Universe"</a>. <i>Astrobiology: Roadmap</i>. <a href="/wiki/NASA" title="NASA">NASA</a>. Archived from <a rel="nofollow" class="external text" href="https://astrobiology.arc.nasa.gov/roadmap/g1.html">the original</a> on 17 January 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">11 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Astrobiology%3A+Roadmap&rft.atitle=Goal+1%3A+Understand+the+nature+and+distribution+of+habitable+environments+in+the+Universe&rft_id=http%3A%2F%2Fastrobiology.arc.nasa.gov%2Froadmap%2Fg1.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-EA-2018901-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-EA-2018901_6-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFStaff2018" class="citation web cs1">Staff (1 September 2018). <a rel="nofollow" class="external text" href="https://www.eurekalert.org/pub_releases/2018-08/uoc-wwc083018.php">"Water worlds could support life, study says – Analysis by UChicago, Penn State scientists challenges idea that life requires 'Earth clone'<span class="cs1-kern-right"></span>"</a>. <i><a href="/wiki/EurekAlert" class="mw-redirect" title="EurekAlert">EurekAlert</a></i><span class="reference-accessdate">. Retrieved <span class="nowrap">1 September</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=EurekAlert&rft.atitle=Water+worlds+could+support+life%2C+study+says+%E2%80%93+Analysis+by+UChicago%2C+Penn+State+scientists+challenges+idea+that+life+requires+%27Earth+clone%27&rft.date=2018-09-01&rft.au=Staff&rft_id=https%3A%2F%2Fwww.eurekalert.org%2Fpub_releases%2F2018-08%2Fuoc-wwc083018.php&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-APJ-20180831-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-APJ-20180831_7-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKiteFord2018" class="citation journal cs1">Kite, Edwin S.; Ford, Eric B. (31 August 2018). <a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F1538-4357%2Faad6e0">"Habitability of Exoplanet Waterworlds"</a>. <i><a href="/wiki/The_Astrophysical_Journal" title="The Astrophysical Journal">The Astrophysical Journal</a></i>. <b>864</b> (1): 75. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1801.00748">1801.00748</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2018ApJ...864...75K">2018ApJ...864...75K</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F1538-4357%2Faad6e0">10.3847/1538-4357/aad6e0</a></span>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:46991835">46991835</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=Habitability+of+Exoplanet+Waterworlds&rft.volume=864&rft.issue=1&rft.pages=75&rft.date=2018-08-31&rft_id=info%3Aarxiv%2F1801.00748&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A46991835%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.3847%2F1538-4357%2Faad6e0&rft_id=info%3Abibcode%2F2018ApJ...864...75K&rft.aulast=Kite&rft.aufirst=Edwin+S.&rft.au=Ford%2C+Eric+B.&rft_id=https%3A%2F%2Fdoi.org%2F10.3847%252F1538-4357%252Faad6e0&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWolszczanFrail1992" class="citation journal cs1">Wolszczan, A.; Frail, D. A. (9 January 1992). "A planetary system around the millisecond pulsar PSR1257 + 12". <i>Nature</i>. <b>355</b> (6356): 145–147. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1992Natur.355..145W">1992Natur.355..145W</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2F355145a0">10.1038/355145a0</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:4260368">4260368</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=A+planetary+system+around+the+millisecond+pulsar+PSR1257+%2B+12&rft.volume=355&rft.issue=6356&rft.pages=145-147&rft.date=1992-01-09&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A4260368%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1038%2F355145a0&rft_id=info%3Abibcode%2F1992Natur.355..145W&rft.aulast=Wolszczan&rft.aufirst=A.&rft.au=Frail%2C+D.+A.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWolszczan1994" class="citation journal cs1">Wolszczan, A (1994). "Confirmation of Earth Mass Planets Orbiting the Millisecond Pulsar PSR:B1257+12". <i>Science</i>. <b>264</b> (5158): 538–42. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1994Sci...264..538W">1994Sci...264..538W</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.264.5158.538">10.1126/science.264.5158.538</a>. <a href="/wiki/JSTOR_(identifier)" class="mw-redirect" title="JSTOR (identifier)">JSTOR</a> <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/2883699">2883699</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/17732735">17732735</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:19621191">19621191</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science&rft.atitle=Confirmation+of+Earth+Mass+Planets+Orbiting+the+Millisecond+Pulsar+PSR%3AB1257%2B12&rft.volume=264&rft.issue=5158&rft.pages=538-42&rft.date=1994&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A19621191%23id-name%3DS2CID&rft_id=info%3Abibcode%2F1994Sci...264..538W&rft_id=info%3Apmid%2F17732735&rft_id=info%3Adoi%2F10.1126%2Fscience.264.5158.538&rft_id=https%3A%2F%2Fwww.jstor.org%2Fstable%2F2883699%23id-name%3DJSTOR&rft.aulast=Wolszczan&rft.aufirst=A&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-NASA-1990-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-NASA-1990_11-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGraham1990" class="citation journal cs1">Graham, Robert W. (February 1990). <a rel="nofollow" class="external text" href="https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900013148_1990013148.pdf">"NASA Technical Memorandum 102363 – Extraterrestrial Life in the Universe"</a> <span class="cs1-format">(PDF)</span>. <i><a href="/wiki/NASA" title="NASA">NASA</a></i>. Lewis Research Center, Ohio<span class="reference-accessdate">. Retrieved <span class="nowrap">7 July</span> 2014</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=NASA&rft.atitle=NASA+Technical+Memorandum+102363+%E2%80%93+Extraterrestrial+Life+in+the+Universe&rft.date=1990-02&rft.aulast=Graham&rft.aufirst=Robert+W.&rft_id=https%3A%2F%2Fntrs.nasa.gov%2Farchive%2Fnasa%2Fcasi.ntrs.nasa.gov%2F19900013148_1990013148.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-Astrobiology-2008-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-Astrobiology-2008_12-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAltermann2008" class="citation book cs1">Altermann, Wladyslaw (2008). "From Fossils to Astrobiology – A Roadmap to Fata Morgana?". In Seckbach, Joseph; Walsh, Maud (eds.). <i>From Fossils to Astrobiology: Records of Life on Earth and the Search for Extraterrestrial Biosignatures</i>. Vol. 12. Springer. p. xvii. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-4020-8836-0" title="Special:BookSources/978-1-4020-8836-0"><bdi>978-1-4020-8836-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=From+Fossils+to+Astrobiology+%E2%80%93+A+Roadmap+to+Fata+Morgana%3F&rft.btitle=From+Fossils+to+Astrobiology%3A+Records+of+Life+on+Earth+and+the+Search+for+Extraterrestrial+Biosignatures&rft.pages=xvii&rft.pub=Springer&rft.date=2008&rft.isbn=978-1-4020-8836-0&rft.aulast=Altermann&rft.aufirst=Wladyslaw&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHorneckPetra_Rettberg2007" class="citation book cs1">Horneck, Gerda; Petra Rettberg (2007). <i>Complete Course in Astrobiology</i>. Wiley-VCH. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-3-527-40660-9" title="Special:BookSources/978-3-527-40660-9"><bdi>978-3-527-40660-9</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Complete+Course+in+Astrobiology&rft.pub=Wiley-VCH&rft.date=2007&rft.isbn=978-3-527-40660-9&rft.aulast=Horneck&rft.aufirst=Gerda&rft.au=Petra+Rettberg&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-NYT-20131118-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-NYT-20131118_14-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDavies2013" class="citation news cs1"><a href="/wiki/Paul_Davies" title="Paul Davies">Davies, Paul</a> (18 November 2013). <a rel="nofollow" class="external text" href="https://www.nytimes.com/2013/11/19/opinion/are-we-alone-in-the-universe.html">"Are We Alone in the Universe?"</a>. <i><a href="/wiki/The_New_York_Times" title="The New York Times">The New York Times</a></i><span class="reference-accessdate">. Retrieved <span class="nowrap">20 November</span> 2013</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+New+York+Times&rft.atitle=Are+We+Alone+in+the+Universe%3F&rft.date=2013-11-18&rft.aulast=Davies&rft.aufirst=Paul&rft_id=https%3A%2F%2Fwww.nytimes.com%2F2013%2F11%2F19%2Fopinion%2Fare-we-alone-in-the-universe.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-NYT-20150106-DB-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-NYT-20150106-DB_15-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFOverbye2015" class="citation news cs1"><a href="/wiki/Dennis_Overbye" title="Dennis Overbye">Overbye, Dennis</a> (6 January 2015). <a rel="nofollow" class="external text" href="https://www.nytimes.com/2015/01/07/science/space/as-ranks-of-goldilocks-planets-grow-astronomers-consider-whats-next.html">"As Ranks of Goldilocks Planets Grow, Astronomers Consider What's Next"</a>. <i><a href="/wiki/The_New_York_Times" title="The New York Times">The New York Times</a></i><span class="reference-accessdate">. Retrieved <span class="nowrap">6 January</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+New+York+Times&rft.atitle=As+Ranks+of+Goldilocks+Planets+Grow%2C+Astronomers+Consider+What%27s+Next&rft.date=2015-01-06&rft.aulast=Overbye&rft.aufirst=Dennis&rft_id=https%3A%2F%2Fwww.nytimes.com%2F2015%2F01%2F07%2Fscience%2Fspace%2Fas-ranks-of-goldilocks-planets-grow-astronomers-consider-whats-next.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-NYT-20131104-16"><span class="mw-cite-backlink">^ <a href="#cite_ref-NYT-20131104_16-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-NYT-20131104_16-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFOverbye2013" class="citation news cs1">Overbye, Dennis (4 November 2013). <a rel="nofollow" class="external text" href="https://www.nytimes.com/2013/11/05/science/cosmic-census-finds-billions-of-planets-that-could-be-like-earth.html">"Far-Off Planets Like the Earth Dot the Galaxy"</a>. <i><a href="/wiki/The_New_York_Times" title="The New York Times">The New York Times</a></i><span class="reference-accessdate">. Retrieved <span class="nowrap">5 November</span> 2013</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+New+York+Times&rft.atitle=Far-Off+Planets+Like+the+Earth+Dot+the+Galaxy&rft.date=2013-11-04&rft.aulast=Overbye&rft.aufirst=Dennis&rft_id=https%3A%2F%2Fwww.nytimes.com%2F2013%2F11%2F05%2Fscience%2Fcosmic-census-finds-billions-of-planets-that-could-be-like-earth.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-PNAS-20131031-17"><span class="mw-cite-backlink">^ <a href="#cite_ref-PNAS-20131031_17-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-PNAS-20131031_17-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFPetiguraHowardMarcy2013" class="citation journal cs1">Petigura, Eric A.; Howard, Andrew W.; Marcy, Geoffrey W. (31 October 2013). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845182">"Prevalence of Earth-size planets orbiting Sun-like stars"</a>. <i><a href="/wiki/Proceedings_of_the_National_Academy_of_Sciences_of_the_United_States_of_America" title="Proceedings of the National Academy of Sciences of the United States of America">Proceedings of the National Academy of Sciences of the United States of America</a></i>. <b>110</b> (48): 19273–19278. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1311.6806">1311.6806</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2013PNAS..11019273P">2013PNAS..11019273P</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1073%2Fpnas.1319909110">10.1073/pnas.1319909110</a></span>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845182">3845182</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/24191033">24191033</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Proceedings+of+the+National+Academy+of+Sciences+of+the+United+States+of+America&rft.atitle=Prevalence+of+Earth-size+planets+orbiting+Sun-like+stars&rft.volume=110&rft.issue=48&rft.pages=19273-19278&rft.date=2013-10-31&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3845182%23id-name%3DPMC&rft_id=info%3Abibcode%2F2013PNAS..11019273P&rft_id=info%3Aarxiv%2F1311.6806&rft_id=info%3Apmid%2F24191033&rft_id=info%3Adoi%2F10.1073%2Fpnas.1319909110&rft.aulast=Petigura&rft.aufirst=Eric+A.&rft.au=Howard%2C+Andrew+W.&rft.au=Marcy%2C+Geoffrey+W.&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3845182&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-LATimes-20131104-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-LATimes-20131104_18-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKhan2013" class="citation news cs1">Khan, Amina (4 November 2013). <a rel="nofollow" class="external text" href="http://www.latimes.com/science/la-sci-earth-like-planets-20131105,0,2673237.story">"Milky Way may host billions of Earth-size planets"</a>. <i><a href="/wiki/Los_Angeles_Times" title="Los Angeles Times">Los Angeles Times</a></i><span class="reference-accessdate">. Retrieved <span class="nowrap">5 November</span> 2013</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Los+Angeles+Times&rft.atitle=Milky+Way+may+host+billions+of+Earth-size+planets&rft.date=2013-11-04&rft.aulast=Khan&rft.aufirst=Amina&rft_id=http%3A%2F%2Fwww.latimes.com%2Fscience%2Fla-sci-earth-like-planets-20131105%2C0%2C2673237.story&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-phl.upr.edu-19"><span class="mw-cite-backlink">^ <a href="#cite_ref-phl.upr.edu_19-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-phl.upr.edu_19-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-phl.upr.edu_19-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://phl.upr.edu/projects/habitable-exoplanets-catalog">"The Habitable Exoplanets Catalog – Planetary Habitability Laboratory @ UPR Arecibo"</a>. <i>phl.upr.edu</i><span class="reference-accessdate">. Retrieved <span class="nowrap">19 August</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=phl.upr.edu&rft.atitle=The+Habitable+Exoplanets+Catalog+%E2%80%93+Planetary+Habitability+Laboratory+%40+UPR+Arecibo&rft_id=http%3A%2F%2Fphl.upr.edu%2Fprojects%2Fhabitable-exoplanets-catalog&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-Review_2009-20"><span class="mw-cite-backlink">^ <a href="#cite_ref-Review_2009_20-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Review_2009_20-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Review_2009_20-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Review_2009_20-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Review_2009_20-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-Review_2009_20-5"><sup><i><b>f</b></i></sup></a> <a href="#cite_ref-Review_2009_20-6"><sup><i><b>g</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLammerBredehöftCoustenisKhodachenko2009" class="citation journal cs1">Lammer, H.; Bredehöft, J. H.; Coustenis, A.; Khodachenko, M. L.; et al. (2009). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20160602235333/http://veilnebula.jorgejohnson.me/uploads/3/5/8/7/3587678/lammer_et_al_2009_astron_astro_rev-4.pdf">"What makes a planet habitable?"</a> <span class="cs1-format">(PDF)</span>. <i>The Astronomy and Astrophysics Review</i>. <b>17</b> (2): 181–249. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2009A&ARv..17..181L">2009A&ARv..17..181L</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs00159-009-0019-z">10.1007/s00159-009-0019-z</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:123220355">123220355</a>. Archived from <a rel="nofollow" class="external text" href="http://veilnebula.jorgejohnson.me/uploads/3/5/8/7/3587678/lammer_et_al_2009_astron_astro_rev-4.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 2 June 2016<span class="reference-accessdate">. Retrieved <span class="nowrap">3 May</span> 2016</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astronomy+and+Astrophysics+Review&rft.atitle=What+makes+a+planet+habitable%3F&rft.volume=17&rft.issue=2&rft.pages=181-249&rft.date=2009&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A123220355%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1007%2Fs00159-009-0019-z&rft_id=info%3Abibcode%2F2009A%26ARv..17..181L&rft.aulast=Lammer&rft.aufirst=H.&rft.au=Bredeh%C3%B6ft%2C+J.+H.&rft.au=Coustenis%2C+A.&rft.au=Khodachenko%2C+M.+L.&rft_id=http%3A%2F%2Fveilnebula.jorgejohnson.me%2Fuploads%2F3%2F5%2F8%2F7%2F3587678%2Flammer_et_al_2009_astron_astro_rev-4.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-ajs.145-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-ajs.145_21-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTurnbullTarter2003" class="citation journal cs1">Turnbull, Margaret C.; Tarter, Jill C. (March 2003). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20060222123523/http://skye.as.arizona.edu/~turnbull/HabCat.pdf">"Target selection for SETI: A catalog of nearby habitable stellar systems"</a> <span class="cs1-format">(PDF)</span>. <i>The Astrophysical Journal Supplement Series</i>. <b>145</b> (1): 181–198. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0210675">astro-ph/0210675</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2003ApJS..145..181T">2003ApJS..145..181T</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F345779">10.1086/345779</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:14734094">14734094</a>. Archived from <a rel="nofollow" class="external text" href="http://skye.as.arizona.edu/~turnbull/HabCat.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 22 February 2006.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal+Supplement+Series&rft.atitle=Target+selection+for+SETI%3A+A+catalog+of+nearby+habitable+stellar+systems&rft.volume=145&rft.issue=1&rft.pages=181-198&rft.date=2003-03&rft_id=info%3Aarxiv%2Fastro-ph%2F0210675&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A14734094%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1086%2F345779&rft_id=info%3Abibcode%2F2003ApJS..145..181T&rft.aulast=Turnbull&rft.aufirst=Margaret+C.&rft.au=Tarter%2C+Jill+C.&rft_id=http%3A%2F%2Fskye.as.arizona.edu%2F~turnbull%2FHabCat.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span> Habitability criteria defined—the foundational source for this article.</span> </li> <li id="cite_note-SP-20150821-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-SP-20150821_22-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFChoi2015" class="citation web cs1">Choi, Charles Q. (21 August 2015). <a rel="nofollow" class="external text" href="http://www.space.com/30335-giant-galaxies-habitable-planets.html">"Giant Galaxies May Be Better Cradles for Habitable Planets"</a>. <i><a href="/wiki/Space.com" title="Space.com">Space.com</a></i><span class="reference-accessdate">. Retrieved <span class="nowrap">24 August</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Space.com&rft.atitle=Giant+Galaxies+May+Be+Better+Cradles+for+Habitable+Planets&rft.date=2015-08-21&rft.aulast=Choi&rft.aufirst=Charles+Q.&rft_id=http%3A%2F%2Fwww.space.com%2F30335-giant-galaxies-habitable-planets.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGiovanni2021" class="citation book cs1">Giovanni, Modirrousta-Galian, Darius Maddalena (4 April 2021). <a rel="nofollow" class="external text" href="http://worldcat.org/oclc/1247136170"><i>Of Aliens and Exoplanets: Why the search for life, probably, requires the search for water</i></a>. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/1247136170">1247136170</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Of+Aliens+and+Exoplanets%3A+Why+the+search+for+life%2C+probably%2C+requires+the+search+for+water&rft.date=2021-04-04&rft_id=info%3Aoclcnum%2F1247136170&rft.aulast=Giovanni&rft.aufirst=Modirrousta-Galian%2C+Darius+Maddalena&rft_id=http%3A%2F%2Fworldcat.org%2Foclc%2F1247136170&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_book" title="Template:Cite book">cite book</a>}}</code>: CS1 maint: multiple names: authors list (<a href="/wiki/Category:CS1_maint:_multiple_names:_authors_list" title="Category:CS1 maint: multiple names: authors list">link</a>)</span></span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.world-builders.org/lessons/less/les1/StarTables.html">"Star tables"</a>. <a href="/wiki/California_State_University" title="California State University">California State University</a>, Los Angeles. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20080614211818/http://www.world-builders.org/lessons/less/les1/StarTables.html">Archived</a> from the original on 14 June 2008<span class="reference-accessdate">. Retrieved <span class="nowrap">12 August</span> 2010</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Star+tables&rft.pub=California+State+University%2C+Los+Angeles&rft_id=http%3A%2F%2Fwww.world-builders.org%2Flessons%2Fless%2Fles1%2FStarTables.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKastingWhittetSheldon1997" class="citation journal cs1"><a href="/wiki/James_Kasting" title="James Kasting">Kasting, James F.</a>; Whittet, DC; Sheldon, WR (August 1997). "Ultraviolet radiation from F and K stars and implications for planetary habitability". <i>Origins of Life and Evolution of Biospheres</i>. <b>27</b> (4): 413–420. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1997OLEB...27..413K">1997OLEB...27..413K</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1023%2FA%3A1006596806012">10.1023/A:1006596806012</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/11536831">11536831</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:9685420">9685420</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Origins+of+Life+and+Evolution+of+Biospheres&rft.atitle=Ultraviolet+radiation+from+F+and+K+stars+and+implications+for+planetary+habitability&rft.volume=27&rft.issue=4&rft.pages=413-420&rft.date=1997-08&rft_id=info%3Adoi%2F10.1023%2FA%3A1006596806012&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A9685420%23id-name%3DS2CID&rft_id=info%3Apmid%2F11536831&rft_id=info%3Abibcode%2F1997OLEB...27..413K&rft.aulast=Kasting&rft.aufirst=James+F.&rft.au=Whittet%2C+DC&rft.au=Sheldon%2C+WR&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-27">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://hyperphysics.phy-astr.gsu.edu/hbase/Biology/ligabs.html">"Light Absorption for Photosynthesis"</a> <span class="cs1-format">(Graphic with references)</span>. <i>phy-astr.gus.edu</i>. Georgia State University<span class="reference-accessdate">. Retrieved <span class="nowrap">1 May</span> 2018</span>. <q>It is evident from these absorption and output plots that only the red and blue ends of the visible part of the electromagnetic spectrum are used by plants in photosynthesis. The reflection and transmission of the middle of the spectrum gives the leaves their green visual color.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=phy-astr.gus.edu&rft.atitle=Light+Absorption+for+Photosynthesis&rft_id=http%3A%2F%2Fhyperphysics.phy-astr.gsu.edu%2Fhbase%2FBiology%2Fligabs.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGuinanCuntz2009" class="citation web cs1">Guinan, Edward; Cuntz, Manfred (10 August 2009). <a rel="nofollow" class="external text" href="http://www.iau.org/public_press/news/detail/iau0916/">"The violent youth of solar proxies steer course of genesis of life"</a>. International Astronomical Union<span class="reference-accessdate">. Retrieved <span class="nowrap">27 August</span> 2009</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+violent+youth+of+solar+proxies+steer+course+of+genesis+of+life&rft.pub=International+Astronomical+Union&rft.date=2009-08-10&rft.aulast=Guinan&rft.aufirst=Edward&rft.au=Cuntz%2C+Manfred&rft_id=http%3A%2F%2Fwww.iau.org%2Fpublic_press%2Fnews%2Fdetail%2Fiau0916%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-29">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation pressrelease cs1"><a rel="nofollow" class="external text" href="http://www.aanda.org/content/view/275/42/lang,en/">"Gliese 581: one planet might indeed be habitable"</a> (Press release). Astronomy & Astrophysics. 13 December 2007<span class="reference-accessdate">. Retrieved <span class="nowrap">7 April</span> 2008</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Gliese+581%3A+one+planet+might+indeed+be+habitable&rft.pub=Astronomy+%26+Astrophysics&rft.date=2007-12-13&rft_id=http%3A%2F%2Fwww.aanda.org%2Fcontent%2Fview%2F275%2F42%2Flang%2Cen%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-Simbad-20120920-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-Simbad-20120920_30-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFStaff2012" class="citation web cs1">Staff (20 September 2012). <a rel="nofollow" class="external text" href="http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HIP+19394">"LHS 188 – High proper-motion Star"</a>. <a href="/wiki/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg" title="Centre de données astronomiques de Strasbourg">Centre de données astronomiques de Strasbourg</a> (Strasbourg astronomical Data Center)<span class="reference-accessdate">. Retrieved <span class="nowrap">20 September</span> 2012</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=LHS+188+%E2%80%93+High+proper-motion+Star&rft.pub=Centre+de+donn%C3%A9es+astronomiques+de+Strasbourg+%28Strasbourg+astronomical+Data+Center%29&rft.date=2012-09-20&rft.au=Staff&rft_id=http%3A%2F%2Fsimbad.u-strasbg.fr%2Fsimbad%2Fsim-id%3FIdent%3DHIP%2B19394&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-PHL-20120829-31"><span class="mw-cite-backlink">^ <a href="#cite_ref-PHL-20120829_31-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-PHL-20120829_31-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMéndez2012" class="citation web cs1">Méndez, Abel (29 August 2012). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20191021202448/http://phl.upr.edu/press-releases/ahotpotentialhabitableexoplanetaroundgliese163">"A Hot Potential Habitable Exoplanet around Gliese 163"</a>. <a href="/wiki/University_of_Puerto_Rico_at_Arecibo" title="University of Puerto Rico at Arecibo">University of Puerto Rico at Arecibo</a> (Planetary Habitability Laboratory). Archived from <a rel="nofollow" class="external text" href="https://phl.upr.edu/press-releases/ahotpotentialhabitableexoplanetaroundgliese163">the original</a> on 21 October 2019<span class="reference-accessdate">. Retrieved <span class="nowrap">20 September</span> 2012</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=A+Hot+Potential+Habitable+Exoplanet+around+Gliese+163&rft.pub=University+of+Puerto+Rico+at+Arecibo+%28Planetary+Habitability+Laboratory%29&rft.date=2012-08-29&rft.aulast=M%C3%A9ndez&rft.aufirst=Abel&rft_id=http%3A%2F%2Fphl.upr.edu%2Fpress-releases%2Fahotpotentialhabitableexoplanetaroundgliese163&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-Space-20120920-32"><span class="mw-cite-backlink">^ <a href="#cite_ref-Space-20120920_32-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Space-20120920_32-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRedd2012" class="citation web cs1">Redd, Nola Taylor (20 September 2012). <a rel="nofollow" class="external text" href="http://www.space.com/17684-alien-planet-gliese-163c-extraterrestrial-life.html">"Newfound Alien Planet a Top Contender to Host Life"</a>. <a href="/wiki/Space.com" title="Space.com">Space.com</a><span class="reference-accessdate">. Retrieved <span class="nowrap">20 September</span> 2012</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Newfound+Alien+Planet+a+Top+Contender+to+Host+Life&rft.pub=Space.com&rft.date=2012-09-20&rft.aulast=Redd&rft.aufirst=Nola+Taylor&rft_id=http%3A%2F%2Fwww.space.com%2F17684-alien-planet-gliese-163c-extraterrestrial-life.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-red.1112902301-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-red.1112902301_33-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.redorbit.com/news/space/1112902301/cooler-stars-host-warmer-planets-071913">"Planets May Keep Warmer in a Cool Star System"</a>. Redorbit. 19 July 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Planets+May+Keep+Warmer+in+a+Cool+Star+System&rft.pub=Redorbit&rft.date=2013-07-19&rft_id=http%3A%2F%2Fwww.redorbit.com%2Fnews%2Fspace%2F1112902301%2Fcooler-stars-host-warmer-planets-071913&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-34"><span class="mw-cite-backlink"><b><a href="#cite_ref-34">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFShieldsMeadowsBitzPierrehumbert2013" class="citation journal cs1">Shields, A. L.; Meadows, V. S.; <a href="/wiki/Cecilia_Bitz" title="Cecilia Bitz">Bitz, C. M.</a>; Pierrehumbert, R. T.; Joshi, M. M.; Robinson, T. D. (2013). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3746291">"The Effect of Host Star Spectral Energy Distribution and Ice-Albedo Feedback on the Climate of Extrasolar Planets"</a>. <i>Astrobiology</i>. <b>13</b> (8): 715–39. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1305.6926">1305.6926</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2013AsBio..13..715S">2013AsBio..13..715S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1089%2Fast.2012.0961">10.1089/ast.2012.0961</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3746291">3746291</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/23855332">23855332</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astrobiology&rft.atitle=The+Effect+of+Host+Star+Spectral+Energy+Distribution+and+Ice-Albedo+Feedback+on+the+Climate+of+Extrasolar+Planets&rft.volume=13&rft.issue=8&rft.pages=715-39&rft.date=2013&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3746291%23id-name%3DPMC&rft_id=info%3Abibcode%2F2013AsBio..13..715S&rft_id=info%3Aarxiv%2F1305.6926&rft_id=info%3Apmid%2F23855332&rft_id=info%3Adoi%2F10.1089%2Fast.2012.0961&rft.aulast=Shields&rft.aufirst=A.+L.&rft.au=Meadows%2C+V.+S.&rft.au=Bitz%2C+C.+M.&rft.au=Pierrehumbert%2C+R.+T.&rft.au=Joshi%2C+M.+M.&rft.au=Robinson%2C+T.+D.&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3746291&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-35">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCenter" class="citation web cs1">Center, By Frank Tavares NASA's Ames Research. <a rel="nofollow" class="external text" href="https://exoplanets.nasa.gov/news/1664/about-half-of-sun-like-stars-could-host-rocky-potentially-habitable-planets/">"About Half of Sun-Like Stars Could Host Rocky, Potentially Habitable Planets"</a>. <i>Exoplanet Exploration: Planets Beyond our Solar System</i><span class="reference-accessdate">. Retrieved <span class="nowrap">14 December</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Exoplanet+Exploration%3A+Planets+Beyond+our+Solar+System&rft.atitle=About+Half+of+Sun-Like+Stars+Could+Host+Rocky%2C+Potentially+Habitable+Planets&rft.aulast=Center&rft.aufirst=By+Frank+Tavares+NASA%27s+Ames+Research&rft_id=https%3A%2F%2Fexoplanets.nasa.gov%2Fnews%2F1664%2Fabout-half-of-sun-like-stars-could-host-rocky-potentially-habitable-planets%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-36"><span class="mw-cite-backlink"><b><a href="#cite_ref-36">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKastingWhitmoreReynolds1993" class="citation journal cs1"><a href="/wiki/James_Kasting" title="James Kasting">Kasting, James F.</a>; Whitmore, Daniel P.; Reynolds, Ray T. (1993). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20090318115319/http://www.geosc.psu.edu/~kasting/PersonalPage/Pdf/Icarus_93.pdf">"Habitable Zones Around Main Sequence Stars"</a> <span class="cs1-format">(PDF)</span>. <i>Icarus</i>. <b>101</b> (1): 108–128. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1993Icar..101..108K">1993Icar..101..108K</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1006%2Ficar.1993.1010">10.1006/icar.1993.1010</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/11536936">11536936</a>. Archived from <a rel="nofollow" class="external text" href="http://www.geosc.psu.edu/~kasting/PersonalPage/Pdf/Icarus_93.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 18 March 2009<span class="reference-accessdate">. Retrieved <span class="nowrap">6 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Icarus&rft.atitle=Habitable+Zones+Around+Main+Sequence+Stars&rft.volume=101&rft.issue=1&rft.pages=108-128&rft.date=1993&rft_id=info%3Apmid%2F11536936&rft_id=info%3Adoi%2F10.1006%2Ficar.1993.1010&rft_id=info%3Abibcode%2F1993Icar..101..108K&rft.aulast=Kasting&rft.aufirst=James+F.&rft.au=Whitmore%2C+Daniel+P.&rft.au=Reynolds%2C+Ray+T.&rft_id=http%3A%2F%2Fwww.geosc.psu.edu%2F~kasting%2FPersonalPage%2FPdf%2FIcarus_93.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-37"><span class="mw-cite-backlink"><b><a href="#cite_ref-37">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWilliamsKastingWade1997" class="citation journal cs1">Williams, Darren M.; Kasting, James F.; Wade, Richard A. (January 1997). "Habitable moons around extrasolar giant planets". <i>Nature</i>. <b>385</b> (6613): 234–236. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1996DPS....28.1221W">1996DPS....28.1221W</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2F385234a0">10.1038/385234a0</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/9000072">9000072</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:4233894">4233894</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=Habitable+moons+around+extrasolar+giant+planets&rft.volume=385&rft.issue=6613&rft.pages=234-236&rft.date=1997-01&rft_id=info%3Adoi%2F10.1038%2F385234a0&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A4233894%23id-name%3DS2CID&rft_id=info%3Apmid%2F9000072&rft_id=info%3Abibcode%2F1996DPS....28.1221W&rft.aulast=Williams&rft.aufirst=Darren+M.&rft.au=Kasting%2C+James+F.&rft.au=Wade%2C+Richard+A.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-38"><span class="mw-cite-backlink"><b><a href="#cite_ref-38">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20120209233434/http://www.atmos.washington.edu/1998Q4/211/project2/group4.htm">"The Little Ice Age"</a>. <i>Department of Atmospheric Science</i>. <a href="/wiki/University_of_Washington" title="University of Washington">University of Washington</a>. Archived from <a rel="nofollow" class="external text" href="http://www.atmos.washington.edu/1998Q4/211/project2/group4.htm">the original</a> on 9 February 2012<span class="reference-accessdate">. Retrieved <span class="nowrap">11 May</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Department+of+Atmospheric+Science&rft.atitle=The+Little+Ice+Age&rft_id=http%3A%2F%2Fwww.atmos.washington.edu%2F1998Q4%2F211%2Fproject2%2Fgroup4.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-39"><span class="mw-cite-backlink"><b><a href="#cite_ref-39">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.solstation.com/stars2/18sco.htm">"18 Scorpii"</a>. <i>solstation.com</i>. Sol Company<span class="reference-accessdate">. Retrieved <span class="nowrap">11 May</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=solstation.com&rft.atitle=18+Scorpii&rft_id=http%3A%2F%2Fwww.solstation.com%2Fstars2%2F18sco.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-40"><span class="mw-cite-backlink"><b><a href="#cite_ref-40">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSantosIsraelianMayor2003" class="citation web cs1">Santos, Nuno C.; Israelian, Garik; Mayor, Michael (2003). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20120415095118/http://cs12.colorado.edu/proceedings/oral/tuesday/santosxx.pdf">"Confirming the Metal-Rich Nature of Stars with Giant Planets"</a> <span class="cs1-format">(PDF)</span>. <i>Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems, and The Sun</i>. <a href="/wiki/University_of_Colorado_at_Boulder" class="mw-redirect" title="University of Colorado at Boulder">University of Colorado</a>. Archived from <a rel="nofollow" class="external text" href="http://origins.colorado.edu/cs12/proceedings/oral/tuesday/santosxx.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 15 April 2012<span class="reference-accessdate">. Retrieved <span class="nowrap">11 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Proceedings+of+12th+Cambridge+Workshop+on+Cool+Stars%2C+Stellar+Systems%2C+and+The+Sun&rft.atitle=Confirming+the+Metal-Rich+Nature+of+Stars+with+Giant+Planets&rft.date=2003&rft.aulast=Santos&rft.aufirst=Nuno+C.&rft.au=Israelian%2C+Garik&rft.au=Mayor%2C+Michael&rft_id=http%3A%2F%2Forigins.colorado.edu%2Fcs12%2Fproceedings%2Foral%2Ftuesday%2Fsantosxx.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-moonlife-41"><span class="mw-cite-backlink">^ <a href="#cite_ref-moonlife_41-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-moonlife_41-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20070828084412/http://library.thinkquest.org/C003763/index.php?page=interview13">"An interview with Dr. Darren Williams"</a>. <i>Astrobiology: The Living Universe</i>. 2000. Archived from <a rel="nofollow" class="external text" href="http://library.thinkquest.org/C003763/index.php?page=interview13">the original</a> on 28 August 2007<span class="reference-accessdate">. Retrieved <span class="nowrap">5 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Astrobiology%3A+The+Living+Universe&rft.atitle=An+interview+with+Dr.+Darren+Williams&rft.date=2000&rft_id=http%3A%2F%2Flibrary.thinkquest.org%2FC003763%2Findex.php%3Fpage%3Dinterview13&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-Sagan,_C._1976-42"><span class="mw-cite-backlink">^ <a href="#cite_ref-Sagan,_C._1976_42-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Sagan,_C._1976_42-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSaganSalpeter1976" class="citation journal cs1">Sagan, C.; Salpeter, E. E. (1976). "Particles, environments, and possible ecologies in the Jovian atmosphere". <i>The Astrophysical Journal Supplement Series</i>. <b>32</b>: 737. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1976ApJS...32..737S">1976ApJS...32..737S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F190414">10.1086/190414</a>. <a href="/wiki/Hdl_(identifier)" class="mw-redirect" title="Hdl (identifier)">hdl</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://hdl.handle.net/2060%2F19760019038">2060/19760019038</a></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal+Supplement+Series&rft.atitle=Particles%2C+environments%2C+and+possible+ecologies+in+the+Jovian+atmosphere&rft.volume=32&rft.pages=737&rft.date=1976&rft_id=info%3Ahdl%2F2060%2F19760019038&rft_id=info%3Adoi%2F10.1086%2F190414&rft_id=info%3Abibcode%2F1976ApJS...32..737S&rft.aulast=Sagan&rft.aufirst=C.&rft.au=Salpeter%2C+E.+E.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-Darling-43"><span class="mw-cite-backlink">^ <a href="#cite_ref-Darling_43-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Darling_43-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDarling" class="citation web cs1"><a href="/wiki/David_Darling_(astronomer)" class="mw-redirect" title="David Darling (astronomer)">Darling, David</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20120210170824/http://www.daviddarling.info/encyclopedia/J/Jupiterlife.html">"Jupiter, life on"</a>. The Encyclopedia of Astrobiology, Astronomy, and Spaceflight. Archived from <a rel="nofollow" class="external text" href="http://www.daviddarling.info/encyclopedia/J/Jupiterlife.html">the original</a> on 10 February 2012<span class="reference-accessdate">. Retrieved <span class="nowrap">6 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Jupiter%2C+life+on&rft.pub=The+Encyclopedia+of+Astrobiology%2C+Astronomy%2C+and+Spaceflight&rft.aulast=Darling&rft.aufirst=David&rft_id=http%3A%2F%2Fwww.daviddarling.info%2Fencyclopedia%2FJ%2FJupiterlife.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-45"><span class="mw-cite-backlink"><b><a href="#cite_ref-45">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://motivate.maths.org/conferences/conf58/c58_talk4.shtml">"Could there be life in the outer solar system?"</a>. <i>Millennium Mathematics Project, Videoconferences for Schools</i>. <a href="/wiki/University_of_Cambridge" title="University of Cambridge">University of Cambridge</a>. 2002<span class="reference-accessdate">. Retrieved <span class="nowrap">5 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Millennium+Mathematics+Project%2C+Videoconferences+for+Schools&rft.atitle=Could+there+be+life+in+the+outer+solar+system%3F&rft.date=2002&rft_id=http%3A%2F%2Fmotivate.maths.org%2Fconferences%2Fconf58%2Fc58_talk4.shtml&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-borucki-46"><span class="mw-cite-backlink">^ <a href="#cite_ref-borucki_46-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-borucki_46-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBoruckiKochBasriBatalha2011" class="citation journal cs1">Borucki, William J.; Koch, David G.; Basri, Gibor; Batalha, Natalie; Brown, Timothy M.; Bryson, Stephen T.; Caldwell, Douglas; Christensen-Dalsgaard, Jørgen; Cochran, William D.; Devore, Edna; Dunham, Edward W.; Gautier, Thomas N.; Geary, John C.; Gilliland, Ronald; Gould, Alan; Howell, Steve B.; Jenkins, Jon M.; Latham, David W.; Lissauer, Jack J.; Marcy, Geoffrey W.; Rowe, Jason; Sasselov, Dimitar; Boss, Alan; Charbonneau, David; Ciardi, David; Doyle, Laurance; Dupree, Andrea K.; Ford, Eric B.; Fortney, Jonathan; et al. (2011). "Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data". <i><a href="/wiki/The_Astrophysical_Journal" title="The Astrophysical Journal">The Astrophysical Journal</a></i>. <b>736</b> (1): 19. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1102.0541">1102.0541</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2011ApJ...736...19B">2011ApJ...736...19B</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1088%2F0004-637X%2F736%2F1%2F19">10.1088/0004-637X/736/1/19</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:15233153">15233153</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=Characteristics+of+planetary+candidates+observed+by+Kepler%2C+II%3A+Analysis+of+the+first+four+months+of+data&rft.volume=736&rft.issue=1&rft.pages=19&rft.date=2011&rft_id=info%3Aarxiv%2F1102.0541&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A15233153%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1088%2F0004-637X%2F736%2F1%2F19&rft_id=info%3Abibcode%2F2011ApJ...736...19B&rft.aulast=Borucki&rft.aufirst=William+J.&rft.au=Koch%2C+David+G.&rft.au=Basri%2C+Gibor&rft.au=Batalha%2C+Natalie&rft.au=Brown%2C+Timothy+M.&rft.au=Bryson%2C+Stephen+T.&rft.au=Caldwell%2C+Douglas&rft.au=Christensen-Dalsgaard%2C+J%C3%B8rgen&rft.au=Cochran%2C+William+D.&rft.au=Devore%2C+Edna&rft.au=Dunham%2C+Edward+W.&rft.au=Gautier%2C+Thomas+N.&rft.au=Geary%2C+John+C.&rft.au=Gilliland%2C+Ronald&rft.au=Gould%2C+Alan&rft.au=Howell%2C+Steve+B.&rft.au=Jenkins%2C+Jon+M.&rft.au=Latham%2C+David+W.&rft.au=Lissauer%2C+Jack+J.&rft.au=Marcy%2C+Geoffrey+W.&rft.au=Rowe%2C+Jason&rft.au=Sasselov%2C+Dimitar&rft.au=Boss%2C+Alan&rft.au=Charbonneau%2C+David&rft.au=Ciardi%2C+David&rft.au=Doyle%2C+Laurance&rft.au=Dupree%2C+Andrea+K.&rft.au=Ford%2C+Eric+B.&rft.au=Fortney%2C+Jonathan&rft.au=Holman%2C+Matthew+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-47"><span class="mw-cite-backlink"><b><a href="#cite_ref-47">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20110429012133/http://kepler.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=98">"NASA Finds Earth-size Planet Candidates in Habitable Zone, Six Planet System"</a>. <a href="/wiki/NASA" title="NASA">NASA</a>. 2 February 2011. Archived from <a rel="nofollow" class="external text" href="https://kepler.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=98">the original</a> on 29 April 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">2 February</span> 2011</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=NASA+Finds+Earth-size+Planet+Candidates+in+Habitable+Zone%2C+Six+Planet+System&rft.pub=NASA&rft.date=2011-02-02&rft_id=http%3A%2F%2Fkepler.nasa.gov%2Fnews%2Fnasakeplernews%2Findex.cfm%3FFuseAction%3DShowNews%26NewsID%3D98&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-Grant-48"><span class="mw-cite-backlink"><b><a href="#cite_ref-Grant_48-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGrant2011" class="citation web cs1">Grant, Andrew (8 March 2011). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20140315043746/http://blogs.discovermagazine.com/80beats/2011/03/08/exclusive-most-earth-like-exoplanet-gets-major-demotion-it-isnt-habitable/">"Exclusive: "Most Earth-Like" Exoplanet Gets Major Demotion—It Isn't Habitable"</a>. <a href="/wiki/Discover_Magazine" class="mw-redirect" title="Discover Magazine">Discover Magazine</a>. Archived from <a rel="nofollow" class="external text" href="http://blogs.discovermagazine.com/80beats/2011/03/08/exclusive-most-earth-like-exoplanet-gets-major-demotion-it-isnt-habitable/">the original</a> on 15 March 2014<span class="reference-accessdate">. Retrieved <span class="nowrap">9 March</span> 2011</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Exclusive%3A+%22Most+Earth-Like%22+Exoplanet+Gets+Major+Demotion%E2%80%94It+Isn%27t+Habitable&rft.pub=Discover+Magazine&rft.date=2011-03-08&rft.aulast=Grant&rft.aufirst=Andrew&rft_id=http%3A%2F%2Fblogs.discovermagazine.com%2F80beats%2F2011%2F03%2F08%2Fexclusive-most-earth-like-exoplanet-gets-major-demotion-it-isnt-habitable%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-BorensteinS-49"><span class="mw-cite-backlink"><b><a href="#cite_ref-BorensteinS_49-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBorenstein2011" class="citation news cs1">Borenstein, Seth (19 February 2011). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20240115031655/https://www.nbcnews.com/id/wbna41686017">"Cosmic census finds crowd of planets in our galaxy"</a>. Associated Press. Archived from <a rel="nofollow" class="external text" href="https://www.nbcnews.com/id/wbna41686017">the original</a> on 15 January 2024<span class="reference-accessdate">. Retrieved <span class="nowrap">14 January</span> 2024</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Cosmic+census+finds+crowd+of+planets+in+our+galaxy&rft.date=2011-02-19&rft.aulast=Borenstein&rft.aufirst=Seth&rft_id=https%3A%2F%2Fwww.nbcnews.com%2Fid%2Fwbna41686017&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-<"PHY-20210825"-51"><span class="mw-cite-backlink"><b><a href="#cite_ref-<"PHY-20210825"_51-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFUniversity_of_Cambridge2021" class="citation web cs1"><a href="/wiki/University_of_Cambridge" title="University of Cambridge">University of Cambridge</a> (25 August 2021). <a rel="nofollow" class="external text" href="https://phys.org/news/2021-08-class-habitable-exoplanets-big-life.html">"New class of habitable exoplanets represent a big step forward in the search for life"</a>. <i><a href="/wiki/Phys.org" title="Phys.org">Phys.org</a></i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 August</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Phys.org&rft.atitle=New+class+of+habitable+exoplanets+represent+a+big+step+forward+in+the+search+for+life&rft.date=2021-08-25&rft.au=University+of+Cambridge&rft_id=https%3A%2F%2Fphys.org%2Fnews%2F2021-08-class-habitable-exoplanets-big-life.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-BBC-20210827-52"><span class="mw-cite-backlink"><b><a href="#cite_ref-BBC-20210827_52-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFStaff2021" class="citation news cs1">Staff (27 August 2021). <a rel="nofollow" class="external text" href="https://www.bbc.co.uk/newsround/58308604">"Alien life could be living on big 'Hycean' exoplanets"</a>. <a href="/wiki/BBC_News" title="BBC News">BBC News</a><span class="reference-accessdate">. Retrieved <span class="nowrap">27 August</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Alien+life+could+be+living+on+big+%27Hycean%27+exoplanets&rft.date=2021-08-27&rft.au=Staff&rft_id=https%3A%2F%2Fwww.bbc.co.uk%2Fnewsround%2F58308604&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-53"><span class="mw-cite-backlink"><b><a href="#cite_ref-53">^</a></b></span> <span class="reference-text"><a href="#Ward">Ward</a>, pp. 191–220</span> </li> <li id="cite_note-55"><span class="mw-cite-backlink"><b><a href="#cite_ref-55">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://csmres.jmu.edu/geollab/Fichter/PlateTect/heathistory.html">"The Heat History of the Earth"</a>. <i>Geolab</i>. <a href="/wiki/James_Madison_University" title="James Madison University">James Madison University</a><span class="reference-accessdate">. Retrieved <span class="nowrap">11 May</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Geolab&rft.atitle=The+Heat+History+of+the+Earth&rft_id=http%3A%2F%2Fcsmres.jmu.edu%2Fgeollab%2FFichter%2FPlateTect%2Fheathistory.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-56"><span class="mw-cite-backlink"><b><a href="#cite_ref-56">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRaymondQuinnLunine2007" class="citation journal cs1">Raymond, Sean N.; Quinn, Thomas; Lunine, Jonathan I. (January 2007). <a rel="nofollow" class="external text" href="https://cds.cern.ch/record/895337">"High-resolution simulations of the final assembly of Earth-like planets 2: water delivery and planetary habitability"</a>. <i>Astrobiology</i> (Submitted manuscript). <b>7</b> (1): 66–84. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0510285">astro-ph/0510285</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2007AsBio...7...66R">2007AsBio...7...66R</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1089%2Fast.2006.06-0126">10.1089/ast.2006.06-0126</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/17407404">17407404</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:10257401">10257401</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astrobiology&rft.atitle=High-resolution+simulations+of+the+final+assembly+of+Earth-like+planets+2%3A+water+delivery+and+planetary+habitability&rft.volume=7&rft.issue=1&rft.pages=66-84&rft.date=2007-01&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A10257401%23id-name%3DS2CID&rft_id=info%3Abibcode%2F2007AsBio...7...66R&rft_id=info%3Aarxiv%2Fastro-ph%2F0510285&rft_id=info%3Apmid%2F17407404&rft_id=info%3Adoi%2F10.1089%2Fast.2006.06-0126&rft.aulast=Raymond&rft.aufirst=Sean+N.&rft.au=Quinn%2C+Thomas&rft.au=Lunine%2C+Jonathan+I.&rft_id=https%3A%2F%2Fcds.cern.ch%2Frecord%2F895337&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-57"><span class="mw-cite-backlink"><b><a href="#cite_ref-57">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.cfa.harvard.edu/press/2008/pr200802.html">"Earth: A Borderline Planet for Life?"</a>. <i>Harvard-Smithsonian Center for Astrophysics</i>. 2008<span class="reference-accessdate">. Retrieved <span class="nowrap">4 June</span> 2008</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Harvard-Smithsonian+Center+for+Astrophysics&rft.atitle=Earth%3A+A+Borderline+Planet+for+Life%3F&rft.date=2008&rft_id=http%3A%2F%2Fwww.cfa.harvard.edu%2Fpress%2F2008%2Fpr200802.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-58"><span class="mw-cite-backlink"><b><a href="#cite_ref-58">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.sci.news/space/non-habitable-titan-12703.html">"Titan Most Likely Non-Habitable, Astrobiologists Say | Sci.News"</a>. <i>Sci.News: Breaking Science News</i>. 20 February 2024<span class="reference-accessdate">. Retrieved <span class="nowrap">19 April</span> 2024</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Sci.News%3A+Breaking+Science+News&rft.atitle=Titan+Most+Likely+Non-Habitable%2C+Astrobiologists+Say+%7C+Sci.News&rft.date=2024-02-20&rft_id=https%3A%2F%2Fwww.sci.news%2Fspace%2Fnon-habitable-titan-12703.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-59"><span class="mw-cite-backlink"><b><a href="#cite_ref-59">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNeishMalaskaSotinLopes2024" class="citation journal cs1">Neish, Catherine; Malaska, Michael J.; Sotin, Christophe; <a href="/wiki/Rosaly_Lopes" title="Rosaly Lopes">Lopes, Rosaly M.C.</a>; Nixon, Conor A.; Affholder, Antonin; Chatain, Audrey; Cockell, Charles; Farnsworth, Kendra K.; Higgins, Peter M.; Miller, Kelly E.; Soderlund, Krista M. (1 February 2024). <a rel="nofollow" class="external text" href="https://www.liebertpub.com/doi/10.1089/ast.2023.0055">"Organic Input to Titan's Subsurface Ocean Through Impact Cratering"</a>. <i>Astrobiology</i>. <b>24</b> (2): 177–189. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2024AsBio..24..177N">2024AsBio..24..177N</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1089%2Fast.2023.0055">10.1089/ast.2023.0055</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1531-1074">1531-1074</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/38306187">38306187</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astrobiology&rft.atitle=Organic+Input+to+Titan%27s+Subsurface+Ocean+Through+Impact+Cratering&rft.volume=24&rft.issue=2&rft.pages=177-189&rft.date=2024-02-01&rft_id=info%3Adoi%2F10.1089%2Fast.2023.0055&rft.issn=1531-1074&rft_id=info%3Apmid%2F38306187&rft_id=info%3Abibcode%2F2024AsBio..24..177N&rft.aulast=Neish&rft.aufirst=Catherine&rft.au=Malaska%2C+Michael+J.&rft.au=Sotin%2C+Christophe&rft.au=Lopes%2C+Rosaly+M.C.&rft.au=Nixon%2C+Conor+A.&rft.au=Affholder%2C+Antonin&rft.au=Chatain%2C+Audrey&rft.au=Cockell%2C+Charles&rft.au=Farnsworth%2C+Kendra+K.&rft.au=Higgins%2C+Peter+M.&rft.au=Miller%2C+Kelly+E.&rft.au=Soderlund%2C+Krista+M.&rft_id=https%3A%2F%2Fwww.liebertpub.com%2Fdoi%2F10.1089%2Fast.2023.0055&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-60"><span class="mw-cite-backlink"><b><a href="#cite_ref-60">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation news cs1"><a rel="nofollow" class="external text" href="https://www.bbc.co.uk/news/science-environment-15863549">"Most liveable alien worlds ranked"</a>. Science & Environment. BBC News. 23 November 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">16 August</span> 2017</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Most+liveable+alien+worlds+ranked&rft.date=2011-11-23&rft_id=https%3A%2F%2Fwww.bbc.co.uk%2Fnews%2Fscience-environment-15863549&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-61"><span class="mw-cite-backlink"><b><a href="#cite_ref-61">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNave" class="citation web cs1">Nave, C. R. <a rel="nofollow" class="external text" href="http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magearth.html">"Magnetic Field of the Earth"</a>. <i><a href="/wiki/HyperPhysics" title="HyperPhysics">HyperPhysics</a></i>. <a href="/wiki/Georgia_State_University" title="Georgia State University">Georgia State University</a><span class="reference-accessdate">. Retrieved <span class="nowrap">11 May</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=HyperPhysics&rft.atitle=Magnetic+Field+of+the+Earth&rft.aulast=Nave&rft.aufirst=C.+R.&rft_id=http%3A%2F%2Fhyperphysics.phy-astr.gsu.edu%2Fhbase%2Fmagnetic%2Fmagearth.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-62"><span class="mw-cite-backlink"><b><a href="#cite_ref-62">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFConstantin_W._ArnscheidtRobin_D._WordsworthFeng_Ding2019" class="citation journal cs1">Constantin W. Arnscheidt; Robin D. Wordsworth; Feng Ding (13 August 2019). <a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F1538-4357%2Fab2bf2">"Atmospheric Evolution on Low-gravity Waterworlds"</a>. <i>The Astrophysical Journal</i>. <b>881</b> (1): 60. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1906.10561">1906.10561</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2019ApJ...881...60A">2019ApJ...881...60A</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F1538-4357%2Fab2bf2">10.3847/1538-4357/ab2bf2</a></span>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:195584241">195584241</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=Atmospheric+Evolution+on+Low-gravity+Waterworlds&rft.volume=881&rft.issue=1&rft.pages=60&rft.date=2019-08-13&rft_id=info%3Aarxiv%2F1906.10561&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A195584241%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.3847%2F1538-4357%2Fab2bf2&rft_id=info%3Abibcode%2F2019ApJ...881...60A&rft.au=Constantin+W.+Arnscheidt&rft.au=Robin+D.+Wordsworth&rft.au=Feng+Ding&rft_id=https%3A%2F%2Fdoi.org%2F10.3847%252F1538-4357%252Fab2bf2&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-63"><span class="mw-cite-backlink"><b><a href="#cite_ref-63">^</a></b></span> <span class="reference-text"><a href="#Ward">Ward</a>, pp. 122–123.</span> </li> <li id="cite_note-64"><span class="mw-cite-backlink"><b><a href="#cite_ref-64">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBortman2005" class="citation web cs1">Bortman, Henry (22 June 2005). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20210619031238/https://www.astrobio.net/meteoritescomets-and-asteroids/elusive-earths/">"Elusive Earths"</a>. Astrobiology Magazine. Archived from the original on 19 June 2021<span class="reference-accessdate">. Retrieved <span class="nowrap">8 June</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Elusive+Earths&rft.pub=Astrobiology+Magazine&rft.date=2005-06-22&rft.aulast=Bortman&rft.aufirst=Henry&rft_id=https%3A%2F%2Fwww.astrobio.net%2Fmeteoritescomets-and-asteroids%2Felusive-earths%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: unfit URL (<a href="/wiki/Category:CS1_maint:_unfit_URL" title="Category:CS1 maint: unfit URL">link</a>)</span></span> </li> <li id="cite_note-65"><span class="mw-cite-backlink"><b><a href="#cite_ref-65">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation pressrelease cs1"><a rel="nofollow" class="external text" href="http://www.psu.edu/ur/2003/planetarytilt.html">"Planetary Tilt Not A Spoiler For Habitation"</a> (Press release). <a href="/wiki/Penn_State_University" class="mw-redirect" title="Penn State University">Penn State University</a>. 25 August 2003<span class="reference-accessdate">. Retrieved <span class="nowrap">11 May</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Planetary+Tilt+Not+A+Spoiler+For+Habitation&rft.pub=Penn+State+University&rft.date=2003-08-25&rft_id=http%3A%2F%2Fwww.psu.edu%2Fur%2F2003%2Fplanetarytilt.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-66"><span class="mw-cite-backlink"><b><a href="#cite_ref-66">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLaskerJoutelRobutel1993" class="citation journal cs1">Lasker, J.; Joutel, F.; Robutel, P. (July 1993). "Stabilization of the earth's obliquity by the moon". <i><a href="/wiki/Nature_(journal)" title="Nature (journal)">Nature</a></i>. <b>361</b> (6413): 615–617. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1993Natur.361..615L">1993Natur.361..615L</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2F361615a0">10.1038/361615a0</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:4233758">4233758</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=Stabilization+of+the+earth%27s+obliquity+by+the+moon&rft.volume=361&rft.issue=6413&rft.pages=615-617&rft.date=1993-07&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A4233758%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1038%2F361615a0&rft_id=info%3Abibcode%2F1993Natur.361..615L&rft.aulast=Lasker&rft.aufirst=J.&rft.au=Joutel%2C+F.&rft.au=Robutel%2C+P.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-68"><span class="mw-cite-backlink"><b><a href="#cite_ref-68">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDorminey2009" class="citation web cs1">Dorminey, Bruce (29 April 2009). <a rel="nofollow" class="external text" href="https://www.scientificamerican.com/article/moon-life-tides/">"Without the Moon, Would There Be Life on Earth?"</a>. <i>scientificamerican.com</i>. Scientific American<span class="reference-accessdate">. Retrieved <span class="nowrap">1 May</span> 2018</span>. <q>Europa must have big tides, so it's my favorite for microbial life," says Max Bernstein, an astrochemist and program scientist at NASA Headquarters in Washington, D.C. "Europa is considered by many as the best place to find life in the solar system.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=scientificamerican.com&rft.atitle=Without+the+Moon%2C+Would+There+Be+Life+on+Earth%3F&rft.date=2009-04-29&rft.aulast=Dorminey&rft.aufirst=Bruce&rft_id=https%3A%2F%2Fwww.scientificamerican.com%2Farticle%2Fmoon-life-tides%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-69"><span class="mw-cite-backlink"><b><a href="#cite_ref-69">^</a></b></span> <span class="reference-text">File:Tidalwaves1.gif</span> </li> <li id="cite_note-70"><span class="mw-cite-backlink"><b><a href="#cite_ref-70">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWoo" class="citation news cs1">Woo, Marcus. <a rel="nofollow" class="external text" href="https://www.scientificamerican.com/article/stellar-smashups-may-fuel-planetary-habitability-study-suggests/">"Stellar Smashups May Fuel Planetary Habitability, Study Suggests"</a>. <i>Scientific American</i><span class="reference-accessdate">. Retrieved <span class="nowrap">9 December</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Scientific+American&rft.atitle=Stellar+Smashups+May+Fuel+Planetary+Habitability%2C+Study+Suggests&rft.aulast=Woo&rft.aufirst=Marcus&rft_id=https%3A%2F%2Fwww.scientificamerican.com%2Farticle%2Fstellar-smashups-may-fuel-planetary-habitability-study-suggests%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-71"><span class="mw-cite-backlink"><b><a href="#cite_ref-71">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNimmoPrimackFaberRamirez-Ruiz2020" class="citation journal cs1">Nimmo, Francis; Primack, Joel; Faber, S. M.; Ramirez-Ruiz, Enrico; Safarzadeh, Mohammadtaher (10 November 2020). <a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F2041-8213%2Fabc251">"Radiogenic Heating and Its Influence on Rocky Planet Dynamos and Habitability"</a>. <i>The Astrophysical Journal</i>. <b>903</b> (2): L37. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/2011.04791">2011.04791</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2020ApJ...903L..37N">2020ApJ...903L..37N</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F2041-8213%2Fabc251">10.3847/2041-8213/abc251</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/2041-8213">2041-8213</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:226289878">226289878</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=Radiogenic+Heating+and+Its+Influence+on+Rocky+Planet+Dynamos+and+Habitability&rft.volume=903&rft.issue=2&rft.pages=L37&rft.date=2020-11-10&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A226289878%23id-name%3DS2CID&rft_id=info%3Abibcode%2F2020ApJ...903L..37N&rft_id=info%3Aarxiv%2F2011.04791&rft.issn=2041-8213&rft_id=info%3Adoi%2F10.3847%2F2041-8213%2Fabc251&rft.aulast=Nimmo&rft.aufirst=Francis&rft.au=Primack%2C+Joel&rft.au=Faber%2C+S.+M.&rft.au=Ramirez-Ruiz%2C+Enrico&rft.au=Safarzadeh%2C+Mohammadtaher&rft_id=https%3A%2F%2Fdoi.org%2F10.3847%252F2041-8213%252Fabc251&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-72"><span class="mw-cite-backlink"><b><a href="#cite_ref-72">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation news cs1"><a rel="nofollow" class="external text" href="https://phys.org/news/2020-04-magnetic-field-billion-years-debate.html">"The existence of a magnetic field beyond 3.5 billion years ago is still up for debate"</a>. <i>phys.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">28 December</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=phys.org&rft.atitle=The+existence+of+a+magnetic+field+beyond+3.5+billion+years+ago+is+still+up+for+debate&rft_id=https%3A%2F%2Fphys.org%2Fnews%2F2020-04-magnetic-field-billion-years-debate.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-73"><span class="mw-cite-backlink"><b><a href="#cite_ref-73">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.sciencedaily.com/releases/2008/03/080326161658.htm">"Organic Molecule, Amino Acid-Like, Found in Constellation Sagittarius"</a>. ScienceDaily. 2008<span class="reference-accessdate">. Retrieved <span class="nowrap">20 December</span> 2008</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Organic+Molecule%2C+Amino+Acid-Like%2C+Found+in+Constellation+Sagittarius&rft.pub=ScienceDaily&rft.date=2008&rft_id=https%3A%2F%2Fwww.sciencedaily.com%2Freleases%2F2008%2F03%2F080326161658.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-74"><span class="mw-cite-backlink"><b><a href="#cite_ref-74">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDarling" class="citation web cs1"><a href="/wiki/David_Darling_(astronomer)" class="mw-redirect" title="David Darling (astronomer)">Darling, David</a>. <a rel="nofollow" class="external text" href="http://www.daviddarling.info/encyclopedia/E/elbio.html">"Elements, biological abundance"</a>. The Encyclopedia of Astrobiology, Astronomy, and Spaceflight<span class="reference-accessdate">. Retrieved <span class="nowrap">11 May</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Elements%2C+biological+abundance&rft.pub=The+Encyclopedia+of+Astrobiology%2C+Astronomy%2C+and+Spaceflight&rft.aulast=Darling&rft.aufirst=David&rft_id=http%3A%2F%2Fwww.daviddarling.info%2Fencyclopedia%2FE%2Felbio.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-75"><span class="mw-cite-backlink"><b><a href="#cite_ref-75">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://zebu.uoregon.edu/internet/l3.html">"How did chemistry and oceans produce this?"</a>. <i>The Electronic Universe Project</i>. <a href="/wiki/University_of_Oregon" title="University of Oregon">University of Oregon</a><span class="reference-accessdate">. Retrieved <span class="nowrap">11 May</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+Electronic+Universe+Project&rft.atitle=How+did+chemistry+and+oceans+produce+this%3F&rft_id=http%3A%2F%2Fzebu.uoregon.edu%2Finternet%2Fl3.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-76"><span class="mw-cite-backlink"><b><a href="#cite_ref-76">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://zebu.uoregon.edu/internet/l2.html">"How did the Earth Get to Look Like This?"</a>. <i>The Electronic Universe Project</i>. <a href="/wiki/University_of_Oregon" title="University of Oregon">University of Oregon</a><span class="reference-accessdate">. Retrieved <span class="nowrap">11 May</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+Electronic+Universe+Project&rft.atitle=How+did+the+Earth+Get+to+Look+Like+This%3F&rft_id=http%3A%2F%2Fzebu.uoregon.edu%2Finternet%2Fl2.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-77"><span class="mw-cite-backlink"><b><a href="#cite_ref-77">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20110126083203/http://astrobiology.arc.nasa.gov/roadmap/g5.html">"Understand the evolutionary mechanisms and environmental limits of life"</a>. <i>Astrobiology: Roadmap</i>. <a href="/wiki/NASA" title="NASA">NASA</a>. September 2003. Archived from <a rel="nofollow" class="external text" href="https://astrobiology.arc.nasa.gov/roadmap/g5.html">the original</a> on 26 January 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">6 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Astrobiology%3A+Roadmap&rft.atitle=Understand+the+evolutionary+mechanisms+and+environmental+limits+of+life&rft.date=2003-09&rft_id=http%3A%2F%2Fastrobiology.arc.nasa.gov%2Froadmap%2Fg5.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-78"><span class="mw-cite-backlink"><b><a href="#cite_ref-78">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHart2003" class="citation web cs1">Hart, Stephen (17 June 2003). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20030620142504/http://www.space.com/scienceastronomy/astrobio_caves_030617-1.html">"Cave Dwellers: ET Might Lurk in Dark Places"</a>. <a href="/wiki/Space.com" title="Space.com">Space.com</a>. Archived from <a rel="nofollow" class="external text" href="http://www.space.com/scienceastronomy/astrobio_caves_030617-1.html">the original</a> on 20 June 2003<span class="reference-accessdate">. Retrieved <span class="nowrap">6 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Cave+Dwellers%3A+ET+Might+Lurk+in+Dark+Places&rft.pub=Space.com&rft.date=2003-06-17&rft.aulast=Hart&rft.aufirst=Stephen&rft_id=http%3A%2F%2Fwww.space.com%2Fscienceastronomy%2Fastrobio_caves_030617-1.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-79"><span class="mw-cite-backlink"><b><a href="#cite_ref-79">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLindsayBrasier2006" class="citation journal cs1">Lindsay, J; Brasier, M (2006). <a rel="nofollow" class="external text" href="https://ora.ox.ac.uk/objects/uuid:c9796531-6943-4302-9733-8e8616adf78a">"Impact Craters as biospheric microenvironments, Lawn Hill Structure, Northern Australia"</a>. <i>Astrobiology</i>. <b>6</b> (2): 348–363. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2006AsBio...6..348L">2006AsBio...6..348L</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1089%2Fast.2006.6.348">10.1089/ast.2006.6.348</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/16689651">16689651</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:20466013">20466013</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astrobiology&rft.atitle=Impact+Craters+as+biospheric+microenvironments%2C+Lawn+Hill+Structure%2C+Northern+Australia&rft.volume=6&rft.issue=2&rft.pages=348-363&rft.date=2006&rft_id=info%3Adoi%2F10.1089%2Fast.2006.6.348&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A20466013%23id-name%3DS2CID&rft_id=info%3Apmid%2F16689651&rft_id=info%3Abibcode%2F2006AsBio...6..348L&rft.aulast=Lindsay&rft.aufirst=J&rft.au=Brasier%2C+M&rft_id=https%3A%2F%2Fora.ox.ac.uk%2Fobjects%2Fuuid%3Ac9796531-6943-4302-9733-8e8616adf78a&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-80"><span class="mw-cite-backlink"><b><a href="#cite_ref-80">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMcKay2002" class="citation web cs1">McKay, Christopher (June 2002). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20090826151945/http://quest.nasa.gov/challenges/marsanalog/egypt/AtacamaAdAstra.pdf">"Too Dry for Life: The Atacama Desert and Mars"</a> <span class="cs1-format">(PDF)</span>. <i>Ames Research Center</i>. <a href="/wiki/NASA" title="NASA">NASA</a>. Archived from <a rel="nofollow" class="external text" href="https://quest.nasa.gov/challenges/marsanalog/egypt/AtacamaAdAstra.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 26 August 2009<span class="reference-accessdate">. Retrieved <span class="nowrap">26 August</span> 2009</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Ames+Research+Center&rft.atitle=Too+Dry+for+Life%3A+The+Atacama+Desert+and+Mars&rft.date=2002-06&rft.aulast=McKay&rft.aufirst=Christopher&rft_id=http%3A%2F%2Fquest.nasa.gov%2Fchallenges%2Fmarsanalog%2Fegypt%2FAtacamaAdAstra.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-81"><span class="mw-cite-backlink"><b><a href="#cite_ref-81">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNavarro-GonzálezMcKay2003" class="citation journal cs1">Navarro-González, Rafael; McKay, Christopher P. (7 November 2003). "Mars-Like Soils in the Atacama Desert, Chile, and the Dry Limit of Microbial Life". <i>Science</i>. <b>302</b> (5647): 1018–1021. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2003Sci...302.1018N">2003Sci...302.1018N</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.1089143">10.1126/science.1089143</a>. <a href="/wiki/JSTOR_(identifier)" class="mw-redirect" title="JSTOR (identifier)">JSTOR</a> <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/3835659">3835659</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/14605363">14605363</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:18220447">18220447</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science&rft.atitle=Mars-Like+Soils+in+the+Atacama+Desert%2C+Chile%2C+and+the+Dry+Limit+of+Microbial+Life&rft.volume=302&rft.issue=5647&rft.pages=1018-1021&rft.date=2003-11-07&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A18220447%23id-name%3DS2CID&rft_id=info%3Abibcode%2F2003Sci...302.1018N&rft_id=info%3Apmid%2F14605363&rft_id=info%3Adoi%2F10.1126%2Fscience.1089143&rft_id=https%3A%2F%2Fwww.jstor.org%2Fstable%2F3835659%23id-name%3DJSTOR&rft.aulast=Navarro-Gonz%C3%A1lez&rft.aufirst=Rafael&rft.au=McKay%2C+Christopher+P.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-D.C.Golden-82"><span class="mw-cite-backlink"><b><a href="#cite_ref-D.C.Golden_82-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSchuergerGoldenMing2012" class="citation journal cs1">Schuerger, Andrew C.; Golden, D.C.; Ming, Doug W. (November 2012). "Biotoxicity of Mars soils: 1. Dry deposition of analog soils on microbial colonies and survival under Martian conditions". <i>Planetary and Space Science</i>. <b>72</b> (1): 91–101. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2012P&SS...72...91S">2012P&SS...72...91S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.pss.2012.07.026">10.1016/j.pss.2012.07.026</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Planetary+and+Space+Science&rft.atitle=Biotoxicity+of+Mars+soils%3A+1.+Dry+deposition+of+analog+soils+on+microbial+colonies+and+survival+under+Martian+conditions&rft.volume=72&rft.issue=1&rft.pages=91-101&rft.date=2012-11&rft_id=info%3Adoi%2F10.1016%2Fj.pss.2012.07.026&rft_id=info%3Abibcode%2F2012P%26SS...72...91S&rft.aulast=Schuerger&rft.aufirst=Andrew+C.&rft.au=Golden%2C+D.C.&rft.au=Ming%2C+Doug+W.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-Beaty-83"><span class="mw-cite-backlink">^ <a href="#cite_ref-Beaty_83-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Beaty_83-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBeaty2006" class="citation cs2">Beaty, David W.; et al. (14 July 2006), the Mars Exploration Program Analysis Group (MEPAG) (ed.), <a rel="nofollow" class="external text" href="https://mepag.jpl.nasa.gov/reports/MEPAG_SR-SAG_final1.pdf">"Findings of the Mars Special Regions Science Analysis Group"</a> <span class="cs1-format">(PDF)</span>, <i>Astrobiology</i>, <b>6</b> (5): 677–732, <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2006AsBio...6..677M">2006AsBio...6..677M</a>, <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1089%2Fast.2006.6.677">10.1089/ast.2006.6.677</a>, <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/17067257">17067257</a><span class="reference-accessdate">, retrieved <span class="nowrap">6 June</span> 2013</span></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astrobiology&rft.atitle=Findings+of+the+Mars+Special+Regions+Science+Analysis+Group&rft.volume=6&rft.issue=5&rft.pages=677-732&rft.date=2006-07-14&rft_id=info%3Apmid%2F17067257&rft_id=info%3Adoi%2F10.1089%2Fast.2006.6.677&rft_id=info%3Abibcode%2F2006AsBio...6..677M&rft.aulast=Beaty&rft.aufirst=David+W.&rft_id=http%3A%2F%2Fmepag.jpl.nasa.gov%2Freports%2FMEPAG_SR-SAG_final1.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-PHL-84"><span class="mw-cite-backlink"><b><a href="#cite_ref-PHL_84-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20190521010035/http://phl.upr.edu/projects/habitable-exoplanets-catalog/data/database">"PHL's Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo"</a>. Archived from <a rel="nofollow" class="external text" href="https://phl.upr.edu/projects/habitable-exoplanets-catalog/data/database">the original</a> on 21 May 2019<span class="reference-accessdate">. Retrieved <span class="nowrap">1 December</span> 2022</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=PHL%27s+Exoplanets+Catalog+-+Planetary+Habitability+Laboratory+%40+UPR+Arecibo&rft_id=http%3A%2F%2Fphl.upr.edu%2Fprojects%2Fhabitable-exoplanets-catalog%2Fdata%2Fdatabase&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-85"><span class="mw-cite-backlink"><b><a href="#cite_ref-85">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.cfa.harvard.edu/big-questions/does-life-exist-outside-solar-system">"Does life exist outside of the solar system? | Center for Astrophysics | Harvard & Smithsonian"</a>. <i>www.cfa.harvard.edu</i><span class="reference-accessdate">. Retrieved <span class="nowrap">19 April</span> 2024</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.cfa.harvard.edu&rft.atitle=Does+life+exist+outside+of+the+solar+system%3F+%7C+Center+for+Astrophysics+%7C+Harvard+%26+Smithsonian&rft_id=https%3A%2F%2Fwww.cfa.harvard.edu%2Fbig-questions%2Fdoes-life-exist-outside-solar-system&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-86"><span class="mw-cite-backlink"><b><a href="#cite_ref-86">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBillings2023" class="citation web cs1">Billings, Lee (1 June 2023). <a rel="nofollow" class="external text" href="https://www.scientificamerican.com/article/we-live-in-the-rarest-type-of-planetary-system1/">"We Live in the Rarest Type of Planetary System"</a>. <i>Scientific American</i><span class="reference-accessdate">. Retrieved <span class="nowrap">19 April</span> 2024</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Scientific+American&rft.atitle=We+Live+in+the+Rarest+Type+of+Planetary+System&rft.date=2023-06-01&rft.aulast=Billings&rft.aufirst=Lee&rft_id=https%3A%2F%2Fwww.scientificamerican.com%2Farticle%2Fwe-live-in-the-rarest-type-of-planetary-system1%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-87"><span class="mw-cite-backlink"><b><a href="#cite_ref-87">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.jpl.nasa.gov/habex/">"Habitable Exoplanet Observatory (HabEx)"</a>. <i>www.jpl.nasa.gov</i><span class="reference-accessdate">. Retrieved <span class="nowrap">31 March</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.jpl.nasa.gov&rft.atitle=Habitable+Exoplanet+Observatory+%28HabEx%29&rft_id=https%3A%2F%2Fwww.jpl.nasa.gov%2Fhabex%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-88"><span class="mw-cite-backlink"><b><a href="#cite_ref-88">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCenter" class="citation web cs1">Center, By Frank Tavares NASA's Ames Research. <a rel="nofollow" class="external text" href="https://exoplanets.nasa.gov/news/1664/about-half-of-sun-like-stars-could-host-rocky-potentially-habitable-planets/">"About Half of Sun-Like Stars Could Host Rocky, Potentially Habitable Planets"</a>. <i>Exoplanet Exploration: Planets Beyond our Solar System</i><span class="reference-accessdate">. Retrieved <span class="nowrap">19 November</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Exoplanet+Exploration%3A+Planets+Beyond+our+Solar+System&rft.atitle=About+Half+of+Sun-Like+Stars+Could+Host+Rocky%2C+Potentially+Habitable+Planets&rft.aulast=Center&rft.aufirst=By+Frank+Tavares+NASA%27s+Ames+Research&rft_id=https%3A%2F%2Fexoplanets.nasa.gov%2Fnews%2F1664%2Fabout-half-of-sun-like-stars-could-host-rocky-potentially-habitable-planets%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-89"><span class="mw-cite-backlink"><b><a href="#cite_ref-89">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation pressrelease cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20070813062958/http://cfa-www.harvard.edu/press/2006/pr200611.html">"Most Milky Way Stars Are Single"</a> (Press release). <a href="/wiki/Harvard-Smithsonian_Center_for_Astrophysics" class="mw-redirect" title="Harvard-Smithsonian Center for Astrophysics">Harvard-Smithsonian Center for Astrophysics</a>. 30 January 2006. Archived from <a rel="nofollow" class="external text" href="http://cfa-www.harvard.edu/press/2006/pr200611.html">the original</a> on 13 August 2007<span class="reference-accessdate">. Retrieved <span class="nowrap">5 June</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Most+Milky+Way+Stars+Are+Single&rft.pub=Harvard-Smithsonian+Center+for+Astrophysics&rft.date=2006-01-30&rft_id=http%3A%2F%2Fcfa-www.harvard.edu%2Fpress%2F2006%2Fpr200611.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-90"><span class="mw-cite-backlink"><b><a href="#cite_ref-90">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20110628175616/http://www.solstation.com/habitable.htm">"Stars and Habitable Planets"</a>. <i>solstation.com</i>. Sol Company. Archived from <a rel="nofollow" class="external text" href="http://www.solstation.com/habitable.htm">the original</a> on 28 June 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">5 June</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=solstation.com&rft.atitle=Stars+and+Habitable+Planets&rft_id=http%3A%2F%2Fwww.solstation.com%2Fhabitable.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-91"><span class="mw-cite-backlink"><b><a href="#cite_ref-91">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBoss,_Alan2006" class="citation pressrelease cs1">Boss, Alan (January 2006). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110515225714/http://carnegieinstitution.org/news_releases/news_0601_10.html">"Planetary Systems can from around Binary Stars"</a> (Press release). <a href="/wiki/Carnegie_Institution" class="mw-redirect" title="Carnegie Institution">Carnegie Institution</a>. Archived from <a rel="nofollow" class="external text" href="http://carnegieinstitution.org/news_releases/news_0601_10.html">the original</a> on 15 May 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">5 June</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Planetary+Systems+can+from+around+Binary+Stars&rft.pub=Carnegie+Institution&rft.date=2006-01&rft.au=Boss%2C+Alan&rft_id=http%3A%2F%2Fcarnegieinstitution.org%2Fnews_releases%2Fnews_0601_10.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-92"><span class="mw-cite-backlink"><b><a href="#cite_ref-92">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWiegertHolman1997" class="citation journal cs1">Wiegert, Paul A.; Holman, Matt J. (April 1997). "The stability of planets in the Alpha Centauri system". <i>The Astronomical Journal</i>. <b>113</b> (4): 1445–1450. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/9609106">astro-ph/9609106</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1997AJ....113.1445W">1997AJ....113.1445W</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F118360">10.1086/118360</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:18969130">18969130</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astronomical+Journal&rft.atitle=The+stability+of+planets+in+the+Alpha+Centauri+system&rft.volume=113&rft.issue=4&rft.pages=1445-1450&rft.date=1997-04&rft_id=info%3Aarxiv%2Fastro-ph%2F9609106&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A18969130%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1086%2F118360&rft_id=info%3Abibcode%2F1997AJ....113.1445W&rft.aulast=Wiegert&rft.aufirst=Paul+A.&rft.au=Holman%2C+Matt+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-93"><span class="mw-cite-backlink"><b><a href="#cite_ref-93">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.jpl.nasa.gov/habex/">"Habitable Exoplanet Observatory (HabEx)"</a>. <i>www.jpl.nasa.gov</i><span class="reference-accessdate">. Retrieved <span class="nowrap">31 March</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.jpl.nasa.gov&rft.atitle=Habitable+Exoplanet+Observatory+%28HabEx%29&rft_id=https%3A%2F%2Fwww.jpl.nasa.gov%2Fhabex%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-94"><span class="mw-cite-backlink"><b><a href="#cite_ref-94">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20001121121500/http://exobio.ucsd.edu/Space_Sciences/zones.htm">"Habitable zones of stars"</a>. <i>NASA Specialized Center of Research and Training in Exobiology</i>. <a href="/wiki/University_of_Southern_California" title="University of Southern California">University of Southern California</a>, San Diego. Archived from <a rel="nofollow" class="external text" href="http://exobio.ucsd.edu/Space_Sciences/zones.htm">the original</a> on 21 November 2000<span class="reference-accessdate">. Retrieved <span class="nowrap">11 May</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=NASA+Specialized+Center+of+Research+and+Training+in+Exobiology&rft.atitle=Habitable+zones+of+stars&rft_id=http%3A%2F%2Fexobio.ucsd.edu%2FSpace_Sciences%2Fzones.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-95"><span class="mw-cite-backlink"><b><a href="#cite_ref-95">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJoshiHaberleReynolds1997" class="citation journal cs1">Joshi, M. M.; Haberle, R. M.; Reynolds, R. T. (October 1997). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110814012947/http://crack.seismo.unr.edu/ftp/pub/gillett/joshi.pdf">"Simulations of the Atmospheres of Synchronously Rotating Terrestrial Planets Orbiting M Dwarfs: Conditions for Atmospheric Collapse and the Implications for Habitability"</a> <span class="cs1-format">(PDF)</span>. <i>Icarus</i>. <b>129</b> (2): 450–465. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1997Icar..129..450J">1997Icar..129..450J</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1006%2Ficar.1997.5793">10.1006/icar.1997.5793</a>. Archived from <a rel="nofollow" class="external text" href="http://crack.seismo.unr.edu/ftp/pub/gillett/joshi.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 14 August 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">4 April</span> 2011</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Icarus&rft.atitle=Simulations+of+the+Atmospheres+of+Synchronously+Rotating+Terrestrial+Planets+Orbiting+M+Dwarfs%3A+Conditions+for+Atmospheric+Collapse+and+the+Implications+for+Habitability&rft.volume=129&rft.issue=2&rft.pages=450-465&rft.date=1997-10&rft_id=info%3Adoi%2F10.1006%2Ficar.1997.5793&rft_id=info%3Abibcode%2F1997Icar..129..450J&rft.aulast=Joshi&rft.aufirst=M.+M.&rft.au=Haberle%2C+R.+M.&rft.au=Reynolds%2C+R.+T.&rft_id=http%3A%2F%2Fcrack.seismo.unr.edu%2Fftp%2Fpub%2Fgillett%2Fjoshi.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-96"><span class="mw-cite-backlink"><b><a href="#cite_ref-96">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHeathDoyleJoshiHaberle,_Robert_M.1999" class="citation journal cs1">Heath, Martin J.; Doyle, Laurance R.; Joshi, Manoj M.; Haberle, Robert M. (1999). <a rel="nofollow" class="external text" href="http://www.as.utexas.edu/astronomy/education/spring02/scalo/heath.pdf">"Habitability of Planets Around Red Dwarf Stars"</a> <span class="cs1-format">(PDF)</span>. <i>Origins of Life and Evolution of the Biosphere</i>. <b>29</b> (4): 405–424. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1999OLEB...29..405H">1999OLEB...29..405H</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1023%2FA%3A1006596718708">10.1023/A:1006596718708</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/10472629">10472629</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:12329736">12329736</a><span class="reference-accessdate">. Retrieved <span class="nowrap">11 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Origins+of+Life+and+Evolution+of+the+Biosphere&rft.atitle=Habitability+of+Planets+Around+Red+Dwarf+Stars&rft.volume=29&rft.issue=4&rft.pages=405-424&rft.date=1999&rft_id=info%3Adoi%2F10.1023%2FA%3A1006596718708&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A12329736%23id-name%3DS2CID&rft_id=info%3Apmid%2F10472629&rft_id=info%3Abibcode%2F1999OLEB...29..405H&rft.aulast=Heath&rft.aufirst=Martin+J.&rft.au=Doyle%2C+Laurance+R.&rft.au=Joshi%2C+Manoj+M.&rft.au=Haberle%2C+Robert+M.&rft_id=http%3A%2F%2Fwww.as.utexas.edu%2Fastronomy%2Feducation%2Fspring02%2Fscalo%2Fheath.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-97"><span class="mw-cite-backlink"><b><a href="#cite_ref-97">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCroswell2001" class="citation web cs1">Croswell, Ken (27 January 2001). <a rel="nofollow" class="external text" href="https://www.newscientist.com/article/mg16922754.200-red-willing-and-able.html">"Red, willing and able"</a> (www.kencroswell.com/reddwarflife.html Full reprint). <a href="/wiki/New_Scientist" title="New Scientist">New Scientist</a><span class="reference-accessdate">. Retrieved <span class="nowrap">5 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Red%2C+willing+and+able&rft.pub=New+Scientist&rft.date=2001-01-27&rft.aulast=Croswell&rft.aufirst=Ken&rft_id=https%3A%2F%2Fwww.newscientist.com%2Farticle%2Fmg16922754.200-red-willing-and-able.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-98"><span class="mw-cite-backlink"><b><a href="#cite_ref-98">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCainGay2007" class="citation web cs1">Cain, Fraser; <a href="/wiki/Pamela_L._Gay" title="Pamela L. Gay">Gay, Pamela</a> (2007). <a rel="nofollow" class="external text" href="http://www.astronomycast.com/2007/06/episode-40-american-astronomical-society-meeting-may-2007/">"AstronomyCast episode 40: American Astronomical Society Meeting, May 2007"</a>. <i>Universe Today</i><span class="reference-accessdate">. Retrieved <span class="nowrap">17 June</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Universe+Today&rft.atitle=AstronomyCast+episode+40%3A+American+Astronomical+Society+Meeting%2C+May+2007&rft.date=2007&rft.aulast=Cain&rft.aufirst=Fraser&rft.au=Gay%2C+Pamela&rft_id=http%3A%2F%2Fwww.astronomycast.com%2F2007%2F06%2Fepisode-40-american-astronomical-society-meeting-may-2007%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-Flare-99"><span class="mw-cite-backlink"><b><a href="#cite_ref-Flare_99-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCroswell2005" class="citation web cs1">Croswell, Ken (November 2005). <a rel="nofollow" class="external text" href="http://www.astronomy.com/news/2005/11/a-flare-for-barnards-star">"A Flare for Barnard's Star"</a>. <i>Astronomy Magazine</i>. Kalmbach Publishing Co<span class="reference-accessdate">. Retrieved <span class="nowrap">10 August</span> 2006</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Astronomy+Magazine&rft.atitle=A+Flare+for+Barnard%27s+Star&rft.date=2005-11&rft.aulast=Croswell&rft.aufirst=Ken&rft_id=http%3A%2F%2Fwww.astronomy.com%2Fnews%2F2005%2F11%2Fa-flare-for-barnards-star&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-100"><span class="mw-cite-backlink"><b><a href="#cite_ref-100">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHines,_Sandra2003" class="citation pressrelease cs1">Hines, Sandra (13 January 2003). <a rel="nofollow" class="external text" href="http://www.washington.edu/news/2003/01/13/the-end-of-the-world-has-already-begun-uw-scientists-say/">"<span class="cs1-kern-left"></span>'The end of the world' has already begun, UW scientists say"</a> (Press release). <a href="/wiki/University_of_Washington" title="University of Washington">University of Washington</a><span class="reference-accessdate">. Retrieved <span class="nowrap">5 June</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=%27The+end+of+the+world%27+has+already+begun%2C+UW+scientists+say&rft.pub=University+of+Washington&rft.date=2003-01-13&rft.au=Hines%2C+Sandra&rft_id=http%3A%2F%2Fwww.washington.edu%2Fnews%2F2003%2F01%2F13%2Fthe-end-of-the-world-has-already-begun-uw-scientists-say%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-pnas1_24_9576-101"><span class="mw-cite-backlink"><b><a href="#cite_ref-pnas1_24_9576_101-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLiPahlevanKirschvinkYung2009" class="citation journal cs1">Li, King-Fai; Pahlevan, Kaveh; Kirschvink, Joseph L.; Yung, Yuk L. (2009). <a rel="nofollow" class="external text" href="http://www.gps.caltech.edu/~kfl/paper/Li_PNAS2009.pdf">"Atmospheric pressure as a natural climate regulator for a terrestrial planet with a biosphere"</a> <span class="cs1-format">(PDF)</span>. <i>Proceedings of the National Academy of Sciences</i>. <b>106</b> (24): 9576–9579. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2009PNAS..106.9576L">2009PNAS..106.9576L</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1073%2Fpnas.0809436106">10.1073/pnas.0809436106</a></span>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2701016">2701016</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/19487662">19487662</a><span class="reference-accessdate">. Retrieved <span class="nowrap">19 July</span> 2009</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Proceedings+of+the+National+Academy+of+Sciences&rft.atitle=Atmospheric+pressure+as+a+natural+climate+regulator+for+a+terrestrial+planet+with+a+biosphere&rft.volume=106&rft.issue=24&rft.pages=9576-9579&rft.date=2009&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC2701016%23id-name%3DPMC&rft_id=info%3Apmid%2F19487662&rft_id=info%3Adoi%2F10.1073%2Fpnas.0809436106&rft_id=info%3Abibcode%2F2009PNAS..106.9576L&rft.aulast=Li&rft.aufirst=King-Fai&rft.au=Pahlevan%2C+Kaveh&rft.au=Kirschvink%2C+Joseph+L.&rft.au=Yung%2C+Yuk+L.&rft_id=http%3A%2F%2Fwww.gps.caltech.edu%2F~kfl%2Fpaper%2FLi_PNAS2009.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-102"><span class="mw-cite-backlink"><b><a href="#cite_ref-102">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20110603230636/http://www.astrobio.net/interview/1694/m-dwarfs-the-search-for-life-is-on">"M Dwarfs: The Search for Life is On, Interview with Todd Henry"</a>. Astrobiology Magazine. 29 August 2005. Archived from the original on 3 June 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">5 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=M+Dwarfs%3A+The+Search+for+Life+is+On%2C+Interview+with+Todd+Henry&rft.pub=Astrobiology+Magazine&rft.date=2005-08-29&rft_id=http%3A%2F%2Fwww.astrobio.net%2Fnews%2Fmodules.php%3Fop%3Dmodload%26name%3DNews%26file%3Darticle%26sid%3D1694&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: unfit URL (<a href="/wiki/Category:CS1_maint:_unfit_URL" title="Category:CS1 maint: unfit URL">link</a>)</span></span> </li> <li id="cite_note-Red_Dwarfs_Universe_Today-103"><span class="mw-cite-backlink"><b><a href="#cite_ref-Red_Dwarfs_Universe_Today_103-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCain2009" class="citation web cs1">Cain, Fraser (4 February 2009). <a rel="nofollow" class="external text" href="http://www.universetoday.com/24670/red-dwarf-stars/">"Red Dwarf Stars"</a>. Universe Today.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Red+Dwarf+Stars&rft.pub=Universe+Today&rft.date=2009-02-04&rft.aulast=Cain&rft.aufirst=Fraser&rft_id=http%3A%2F%2Fwww.universetoday.com%2F24670%2Fred-dwarf-stars%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-104"><span class="mw-cite-backlink"><b><a href="#cite_ref-104">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKashiSoker2011" class="citation journal cs1">Kashi, Amit; Soker, Noam (2011). "The outcome of the protoplanetary disk of very massive stars, January 2011". <i>New Astronomy</i>. <b>16</b> (1): 27–32. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1002.4693">1002.4693</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2011NewA...16...27K">2011NewA...16...27K</a>. <a href="/wiki/CiteSeerX_(identifier)" class="mw-redirect" title="CiteSeerX (identifier)">CiteSeerX</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.770.1250">10.1.1.770.1250</a></span>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.newast.2010.06.003">10.1016/j.newast.2010.06.003</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:119255193">119255193</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=New+Astronomy&rft.atitle=The+outcome+of+the+protoplanetary+disk+of+very+massive+stars%2C+January+2011&rft.volume=16&rft.issue=1&rft.pages=27-32&rft.date=2011&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A119255193%23id-name%3DS2CID&rft_id=info%3Abibcode%2F2011NewA...16...27K&rft_id=https%3A%2F%2Fciteseerx.ist.psu.edu%2Fviewdoc%2Fsummary%3Fdoi%3D10.1.1.770.1250%23id-name%3DCiteSeerX&rft_id=info%3Adoi%2F10.1016%2Fj.newast.2010.06.003&rft_id=info%3Aarxiv%2F1002.4693&rft.aulast=Kashi&rft.aufirst=Amit&rft.au=Soker%2C+Noam&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-105"><span class="mw-cite-backlink"><b><a href="#cite_ref-105">^</a></b></span> <span class="reference-text"><a href="/wiki/Stellar_mass#Age" title="Stellar mass">Stellar mass#Age</a></span> </li> <li id="cite_note-Forget_2013-106"><span class="mw-cite-backlink"><b><a href="#cite_ref-Forget_2013_106-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFForget2013" class="citation journal cs1">Forget, François (July 2013). "On the probability of habitable planets". <i>International Journal of Astrobiology</i>. <b>12</b> (3): 177–185. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1212.0113">1212.0113</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2013IJAsB..12..177F">2013IJAsB..12..177F</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2FS1473550413000128">10.1017/S1473550413000128</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:118534798">118534798</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=International+Journal+of+Astrobiology&rft.atitle=On+the+probability+of+habitable+planets&rft.volume=12&rft.issue=3&rft.pages=177-185&rft.date=2013-07&rft_id=info%3Aarxiv%2F1212.0113&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A118534798%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1017%2FS1473550413000128&rft_id=info%3Abibcode%2F2013IJAsB..12..177F&rft.aulast=Forget&rft.aufirst=Fran%C3%A7ois&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-107"><span class="mw-cite-backlink"><b><a href="#cite_ref-107">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMullen2001" class="citation web cs1">Mullen, Leslie (18 May 2001). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110603230653/http://www.astrobio.net/exclusive/139/galactic-habitable-zones">"Galactic Habitable Zones"</a>. Astrobiology Magazine. Archived from the original on 3 June 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">5 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Galactic+Habitable+Zones&rft.pub=Astrobiology+Magazine&rft.date=2001-05-18&rft.aulast=Mullen&rft.aufirst=Leslie&rft_id=http%3A%2F%2Fwww.astrobio.net%2Fnews%2Fmodules.php%3Fop%3Dmodload%26name%3DNews%26file%3Darticle%26sid%3D139&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: unfit URL (<a href="/wiki/Category:CS1_maint:_unfit_URL" title="Category:CS1 maint: unfit URL">link</a>)</span></span> </li> <li id="cite_note-108"><span class="mw-cite-backlink"><b><a href="#cite_ref-108">^</a></b></span> <span class="reference-text"><a href="#Ward">Ward</a>, pp. 26–29.</span> </li> <li id="cite_note-109"><span class="mw-cite-backlink"><b><a href="#cite_ref-109">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDorminey2005" class="citation journal cs1">Dorminey, Bruce (July 2005). "Dark Threat". <i><a href="/wiki/Astronomy_Magazine" class="mw-redirect" title="Astronomy Magazine">Astronomy</a></i>. <b>33</b> (7): 40–45. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2005Ast....33g..40D">2005Ast....33g..40D</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astronomy&rft.atitle=Dark+Threat&rft.volume=33&rft.issue=7&rft.pages=40-45&rft.date=2005-07&rft_id=info%3Abibcode%2F2005Ast....33g..40D&rft.aulast=Dorminey&rft.aufirst=Bruce&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-110"><span class="mw-cite-backlink"><b><a href="#cite_ref-110">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAlan_Boyle2011" class="citation news cs1">Alan Boyle (22 November 2011). <a rel="nofollow" class="external text" href="http://cosmiclog.nbcnews.com/_news/2011/11/22/8956644-which-alien-worlds-are-most-livable">"Which alien worlds are most livable?"</a>. <i>NBC News</i><span class="reference-accessdate">. Retrieved <span class="nowrap">20 March</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=NBC+News&rft.atitle=Which+alien+worlds+are+most+livable%3F&rft.date=2011-11-22&rft.au=Alan+Boyle&rft_id=http%3A%2F%2Fcosmiclog.nbcnews.com%2F_news%2F2011%2F11%2F22%2F8956644-which-alien-worlds-are-most-livable&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-111"><span class="mw-cite-backlink"><b><a href="#cite_ref-111">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDirk_Schulze-Makuch2011" class="citation journal cs1">Dirk Schulze-Makuch; et al. (December 2011). "A Two-Tiered Approach to Assessing the Habitability of Exoplanets". <i><a href="/wiki/Astrobiology_(journal)" title="Astrobiology (journal)">Astrobiology</a></i>. <b>11</b> (10): 1041–1052. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2011AsBio..11.1041S">2011AsBio..11.1041S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1089%2Fast.2010.0592">10.1089/ast.2010.0592</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/22017274">22017274</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astrobiology&rft.atitle=A+Two-Tiered+Approach+to+Assessing+the+Habitability+of+Exoplanets&rft.volume=11&rft.issue=10&rft.pages=1041-1052&rft.date=2011-12&rft_id=info%3Apmid%2F22017274&rft_id=info%3Adoi%2F10.1089%2Fast.2010.0592&rft_id=info%3Abibcode%2F2011AsBio..11.1041S&rft.au=Dirk+Schulze-Makuch&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-112"><span class="mw-cite-backlink"><b><a href="#cite_ref-112">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDrake1973" class="citation journal cs1">Drake, Frank (1973). "Life on a Neutron Star". <i>Astronomy</i>. <b>1</b> (5): 5.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astronomy&rft.atitle=Life+on+a+Neutron+Star&rft.volume=1&rft.issue=5&rft.pages=5&rft.date=1973&rft.aulast=Drake&rft.aufirst=Frank&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-113"><span class="mw-cite-backlink"><b><a href="#cite_ref-113">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDarling" class="citation web cs1"><a href="/wiki/David_Darling_(astronomer)" class="mw-redirect" title="David Darling (astronomer)">Darling, David</a>. <a rel="nofollow" class="external text" href="http://www.daviddarling.info/encyclopedia/N/neutronstarlife.html">"Neutron star, life on"</a>. The Encyclopedia of Astrobiology, Astronomy, and Spaceflight<span class="reference-accessdate">. Retrieved <span class="nowrap">5 September</span> 2009</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Neutron+star%2C+life+on&rft.pub=The+Encyclopedia+of+Astrobiology%2C+Astronomy%2C+and+Spaceflight&rft.aulast=Darling&rft.aufirst=David&rft_id=http%3A%2F%2Fwww.daviddarling.info%2Fencyclopedia%2FN%2Fneutronstarlife.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-114"><span class="mw-cite-backlink"><b><a href="#cite_ref-114">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBortman2004" class="citation web cs1">Bortman, Henry (29 September 2004). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20120208071539/http://astrobio.net/exclusive/1222/coming-soon-good-jupiters">"Coming Soon: "Good" Jupiters"</a>. Astrobiology Magazine. Archived from the original on 8 February 2012<span class="reference-accessdate">. Retrieved <span class="nowrap">5 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Coming+Soon%3A+%22Good%22+Jupiters&rft.pub=Astrobiology+Magazine&rft.date=2004-09-29&rft.aulast=Bortman&rft.aufirst=Henry&rft_id=http%3A%2F%2Fwww.astrobio.net%2Fnews%2Fmodules.php%3Fop%3Dmodload%26name%3DNews%26file%3Darticle%26sid%3D1222&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: unfit URL (<a href="/wiki/Category:CS1_maint:_unfit_URL" title="Category:CS1 maint: unfit URL">link</a>)</span></span> </li> <li id="cite_note-115"><span class="mw-cite-backlink"><b><a href="#cite_ref-115">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHornerJones2010" class="citation journal cs1">Horner, Jonathan; Jones, Barrie (December 2010). <a rel="nofollow" class="external text" href="https://doi.org/10.1111%2Fj.1468-4004.2010.51616.x">"Jupiter – Friend or Foe? An answer"</a>. <i>Astronomy and Geophysics</i>. <b>51</b> (6): 16–22. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2010A&G....51f..16H">2010A&G....51f..16H</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1111%2Fj.1468-4004.2010.51616.x">10.1111/j.1468-4004.2010.51616.x</a></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astronomy+and+Geophysics&rft.atitle=Jupiter+%E2%80%93+Friend+or+Foe%3F+An+answer&rft.volume=51&rft.issue=6&rft.pages=16-22&rft.date=2010-12&rft_id=info%3Adoi%2F10.1111%2Fj.1468-4004.2010.51616.x&rft_id=info%3Abibcode%2F2010A%26G....51f..16H&rft.aulast=Horner&rft.aufirst=Jonathan&rft.au=Jones%2C+Barrie&rft_id=https%3A%2F%2Fdoi.org%2F10.1111%252Fj.1468-4004.2010.51616.x&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-116"><span class="mw-cite-backlink"><b><a href="#cite_ref-116">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHornerJones2008" class="citation journal cs1">Horner, Jonathan; Jones, B. W. (October 2008). "Jupiter – Friend or Foe? I: The Asteroids". <i>International Journal of Astrobiology</i>. <b>7</b> (3–4): 251–261. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/0806.2795">0806.2795</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2008IJAsB...7..251H">2008IJAsB...7..251H</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2FS1473550408004187">10.1017/S1473550408004187</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:8870726">8870726</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=International+Journal+of+Astrobiology&rft.atitle=Jupiter+%E2%80%93+Friend+or+Foe%3F+I%3A+The+Asteroids&rft.volume=7&rft.issue=3%E2%80%934&rft.pages=251-261&rft.date=2008-10&rft_id=info%3Aarxiv%2F0806.2795&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A8870726%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1017%2FS1473550408004187&rft_id=info%3Abibcode%2F2008IJAsB...7..251H&rft.aulast=Horner&rft.aufirst=Jonathan&rft.au=Jones%2C+B.+W.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-117"><span class="mw-cite-backlink"><b><a href="#cite_ref-117">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHornerJones2009" class="citation journal cs1">Horner, Jonathan; Jones, B. W. (April 2009). "Jupiter – friend or foe? II: the Centaurs". <i>International Journal of Astrobiology</i>. <b>8</b> (2): 75–80. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/0903.3305">0903.3305</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2009IJAsB...8...75H">2009IJAsB...8...75H</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2FS1473550408004357">10.1017/S1473550408004357</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:8032181">8032181</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=International+Journal+of+Astrobiology&rft.atitle=Jupiter+%E2%80%93+friend+or+foe%3F+II%3A+the+Centaurs&rft.volume=8&rft.issue=2&rft.pages=75-80&rft.date=2009-04&rft_id=info%3Aarxiv%2F0903.3305&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A8032181%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1017%2FS1473550408004357&rft_id=info%3Abibcode%2F2009IJAsB...8...75H&rft.aulast=Horner&rft.aufirst=Jonathan&rft.au=Jones%2C+B.+W.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-118"><span class="mw-cite-backlink"><b><a href="#cite_ref-118">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHornerJonesChambers2010" class="citation journal cs1">Horner, Jonathan; Jones, B. W.; Chambers, J. (January 2010). "Jupiter – friend or foe? III: the Oort cloud comets". <i>International Journal of Astrobiology</i>. <b>9</b> (1): 1–10. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/0911.4381">0911.4381</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2010IJAsB...9....1H">2010IJAsB...9....1H</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2FS1473550409990346">10.1017/S1473550409990346</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:1103987">1103987</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=International+Journal+of+Astrobiology&rft.atitle=Jupiter+%E2%80%93+friend+or+foe%3F+III%3A+the+Oort+cloud+comets&rft.volume=9&rft.issue=1&rft.pages=1-10&rft.date=2010-01&rft_id=info%3Aarxiv%2F0911.4381&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A1103987%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1017%2FS1473550409990346&rft_id=info%3Abibcode%2F2010IJAsB...9....1H&rft.aulast=Horner&rft.aufirst=Jonathan&rft.au=Jones%2C+B.+W.&rft.au=Chambers%2C+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-119"><span class="mw-cite-backlink"><b><a href="#cite_ref-119">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBatyginLaughlin2015" class="citation journal cs1">Batygin, Konstantin; Laughlin, Greg (7 April 2015). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4394287">"Jupiter's decisive role in the inner Solar System's early evolution"</a>. <i>Proceedings of the National Academy of Sciences</i>. <b>112</b> (14): 4214–4217. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1503.06945">1503.06945</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2015PNAS..112.4214B">2015PNAS..112.4214B</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1073%2Fpnas.1423252112">10.1073/pnas.1423252112</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0027-8424">0027-8424</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4394287">4394287</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/25831540">25831540</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Proceedings+of+the+National+Academy+of+Sciences&rft.atitle=Jupiter%27s+decisive+role+in+the+inner+Solar+System%27s+early+evolution&rft.volume=112&rft.issue=14&rft.pages=4214-4217&rft.date=2015-04-07&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC4394287%23id-name%3DPMC&rft_id=info%3Abibcode%2F2015PNAS..112.4214B&rft_id=info%3Aarxiv%2F1503.06945&rft.issn=0027-8424&rft_id=info%3Adoi%2F10.1073%2Fpnas.1423252112&rft_id=info%3Apmid%2F25831540&rft.aulast=Batygin&rft.aufirst=Konstantin&rft.au=Laughlin%2C+Greg&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC4394287&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-120"><span class="mw-cite-backlink"><b><a href="#cite_ref-120">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNaoz2015" class="citation journal cs1">Naoz, Smadar (7 April 2015). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4394300">"Jupiter's role in sculpting the early Solar System"</a>. <i>Proceedings of the National Academy of Sciences</i>. <b>112</b> (14): 4189–4190. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2015PNAS..112.4189N">2015PNAS..112.4189N</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1073%2Fpnas.1503865112">10.1073/pnas.1503865112</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0027-8424">0027-8424</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4394300">4394300</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/25825762">25825762</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Proceedings+of+the+National+Academy+of+Sciences&rft.atitle=Jupiter%27s+role+in+sculpting+the+early+Solar+System&rft.volume=112&rft.issue=14&rft.pages=4189-4190&rft.date=2015-04-07&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC4394300%23id-name%3DPMC&rft_id=info%3Abibcode%2F2015PNAS..112.4189N&rft_id=info%3Apmid%2F25825762&rft_id=info%3Adoi%2F10.1073%2Fpnas.1503865112&rft.issn=0027-8424&rft.aulast=Naoz&rft.aufirst=Smadar&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC4394300&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-121"><span class="mw-cite-backlink"><b><a href="#cite_ref-121">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLunine2001" class="citation journal cs1">Lunine, Jonathan I. (30 January 2001). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC14664">"The occurrence of Jovian planets and the habitability of planetary systems"</a>. <i>Proceedings of the National Academy of Sciences</i>. <b>98</b> (3): 809–814. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2001PNAS...98..809L">2001PNAS...98..809L</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1073%2Fpnas.98.3.809">10.1073/pnas.98.3.809</a></span>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC14664">14664</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/11158551">11158551</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Proceedings+of+the+National+Academy+of+Sciences&rft.atitle=The+occurrence+of+Jovian+planets+and+the+habitability+of+planetary+systems&rft.volume=98&rft.issue=3&rft.pages=809-814&rft.date=2001-01-30&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC14664%23id-name%3DPMC&rft_id=info%3Apmid%2F11158551&rft_id=info%3Adoi%2F10.1073%2Fpnas.98.3.809&rft_id=info%3Abibcode%2F2001PNAS...98..809L&rft.aulast=Lunine&rft.aufirst=Jonathan+I.&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC14664&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-122"><span class="mw-cite-backlink"><b><a href="#cite_ref-122">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFPorterGrundy2011" class="citation cs2">Porter, Simon B.; Grundy, William M. (July 2011), "Post-capture Evolution of Potentially Habitable Exomoons", <i>The Astrophysical Journal Letters</i>, <b>736</b> (1): L14, <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1106.2800">1106.2800</a></span>, <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2011ApJ...736L..14P">2011ApJ...736L..14P</a>, <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1088%2F2041-8205%2F736%2F1%2FL14">10.1088/2041-8205/736/1/L14</a>, <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:118574839">118574839</a></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal+Letters&rft.atitle=Post-capture+Evolution+of+Potentially+Habitable+Exomoons&rft.volume=736&rft.issue=1&rft.pages=L14&rft.date=2011-07&rft_id=info%3Aarxiv%2F1106.2800&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A118574839%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1088%2F2041-8205%2F736%2F1%2FL14&rft_id=info%3Abibcode%2F2011ApJ...736L..14P&rft.aulast=Porter&rft.aufirst=Simon+B.&rft.au=Grundy%2C+William+M.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-123"><span class="mw-cite-backlink"><b><a href="#cite_ref-123">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20110603230659/http://www.astrobio.net/interview/1720/the-living-worlds-hypothesis">"The Living Worlds Hypothesis"</a>. Astrobiology Magazine. 22 September 2005. Archived from the original on 3 June 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">6 August</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+Living+Worlds+Hypothesis&rft.pub=Astrobiology+Magazine&rft.date=2005-09-22&rft_id=http%3A%2F%2Fwww.astrobio.net%2Fnews%2Fmodules.php%3Fop%3Dmodload%26name%3DNews%26file%3Darticle%26sid%3D1720&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: unfit URL (<a href="/wiki/Category:CS1_maint:_unfit_URL" title="Category:CS1 maint: unfit URL">link</a>)</span></span> </li> <li id="cite_note-124"><span class="mw-cite-backlink"><b><a href="#cite_ref-124">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation news cs1"><a rel="nofollow" class="external text" href="https://phys.org/news/2020-12-chance-major-role-earth-life.html">"Chance played a major role in keeping Earth fit for life"</a>. <i>phys.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">17 January</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=phys.org&rft.atitle=Chance+played+a+major+role+in+keeping+Earth+fit+for+life&rft_id=https%3A%2F%2Fphys.org%2Fnews%2F2020-12-chance-major-role-earth-life.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> <li id="cite_note-10.1038/s43247-020-00057-8-125"><span class="mw-cite-backlink"><b><a href="#cite_ref-10.1038/s43247-020-00057-8_125-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTyrrell2020" class="citation journal cs1">Tyrrell, Toby (11 December 2020). <a rel="nofollow" class="external text" href="https://doi.org/10.1038%2Fs43247-020-00057-8">"Chance played a role in determining whether Earth stayed habitable"</a>. <i>Communications Earth & Environment</i>. <b>1</b> (1): 61. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2020ComEE...1...61T">2020ComEE...1...61T</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1038%2Fs43247-020-00057-8">10.1038/s43247-020-00057-8</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/2662-4435">2662-4435</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:228086341">228086341</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Communications+Earth+%26+Environment&rft.atitle=Chance+played+a+role+in+determining+whether+Earth+stayed+habitable&rft.volume=1&rft.issue=1&rft.pages=61&rft.date=2020-12-11&rft_id=info%3Adoi%2F10.1038%2Fs43247-020-00057-8&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A228086341%23id-name%3DS2CID&rft.issn=2662-4435&rft_id=info%3Abibcode%2F2020ComEE...1...61T&rft.aulast=Tyrrell&rft.aufirst=Toby&rft_id=https%3A%2F%2Fdoi.org%2F10.1038%252Fs43247-020-00057-8&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span> <span typeof="mw:File"><a href="/wiki/File:CC_BY_icon.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e1/CC_BY_icon.svg/50px-CC_BY_icon.svg.png" decoding="async" width="50" height="18" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e1/CC_BY_icon.svg/75px-CC_BY_icon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e1/CC_BY_icon.svg/100px-CC_BY_icon.svg.png 2x" data-file-width="88" data-file-height="31" /></a></span> Available under <a rel="nofollow" class="external text" href="https://creativecommons.org/licenses/by/4.0/">CC BY 4.0</a>.</span> </li> <li id="cite_note-126"><span class="mw-cite-backlink"><b><a href="#cite_ref-126">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTyrrell2021" class="citation web cs1">Tyrrell, Toby (19 January 2021). <a rel="nofollow" class="external text" href="https://theconversation.com/earth-has-stayed-habitable-for-billions-of-years-exactly-how-lucky-did-we-get-153416">"Earth has stayed habitable for billions of years – exactly how lucky did we get?"</a>. <i>The Conversation</i><span class="reference-accessdate">. Retrieved <span class="nowrap">30 January</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+Conversation&rft.atitle=Earth+has+stayed+habitable+for+billions+of+years+%E2%80%93+exactly+how+lucky+did+we+get%3F&rft.date=2021-01-19&rft.aulast=Tyrrell&rft.aufirst=Toby&rft_id=https%3A%2F%2Ftheconversation.com%2Fearth-has-stayed-habitable-for-billions-of-years-exactly-how-lucky-did-we-get-153416&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="Bibliography">Bibliography</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=34" title="Edit section: Bibliography"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="Ward" class="citation book cs1">Ward, Peter; Brownlee, Donald (2000). <i>Rare Earth: Why Complex Life is Uncommon in the Universe</i>. Springer. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-387-98701-9" title="Special:BookSources/978-0-387-98701-9"><bdi>978-0-387-98701-9</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Rare+Earth%3A+Why+Complex+Life+is+Uncommon+in+the+Universe&rft.pub=Springer&rft.date=2000&rft.isbn=978-0-387-98701-9&rft.au=Ward%2C+Peter&rft.au=Brownlee%2C+Donald&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></li></ul> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=35" title="Edit section: Further reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Cohen, Jack and Ian Stewart. <i>Evolving the Alien: The Science of Extraterrestrial Life</i>, Ebury Press, 2002. <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-09-187927-2" title="Special:BookSources/0-09-187927-2">0-09-187927-2</a></li> <li>(2021-01-26) Kepler-22b, the Oceanic Exoplanet - "Finding a New Earth", <i>NASA</i>.<sup id="cite_ref-127" class="reference"><a href="#cite_note-127"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDole1965" class="citation book cs1">Dole, Stephen H. (1965). <a rel="nofollow" class="external text" href="http://www.rand.org/pubs/reports/R414/"><i>Habitable Planets for Man</i></a> (1st ed.). Rand Corporation. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-444-00092-7" title="Special:BookSources/978-0-444-00092-7"><bdi>978-0-444-00092-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Habitable+Planets+for+Man&rft.edition=1st&rft.pub=Rand+Corporation&rft.date=1965&rft.isbn=978-0-444-00092-7&rft.aulast=Dole&rft.aufirst=Stephen+H.&rft_id=http%3A%2F%2Fwww.rand.org%2Fpubs%2Freports%2FR414%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></li> <li>Fogg, Martyn J., ed. "Terraforming" (entire special issue) <i><a href="/wiki/Journal_of_the_British_Interplanetary_Society" title="Journal of the British Interplanetary Society">Journal of the British Interplanetary Society</a></i>, April 1991</li> <li>Fogg, Martyn J. <i>Terraforming: Engineering Planetary Environments</i>, SAE International, 1995. <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1-56091-609-5" title="Special:BookSources/1-56091-609-5">1-56091-609-5</a></li> <li>Gonzalez, Guillermo and Richards, Jay W. <i>The Privileged Planet</i>, Regnery, 2004. <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-89526-065-4" title="Special:BookSources/0-89526-065-4">0-89526-065-4</a></li> <li>Grinspoon, David. <i>Lonely Planets: The Natural Philosophy of Alien Life</i>, HarperCollins, 2004.</li> <li>Lovelock, James. <i>Gaia: A New Look at Life on Earth.</i> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-19-286218-9" title="Special:BookSources/0-19-286218-9">0-19-286218-9</a></li> <li>Schmidt, Stanley and Robert Zubrin, eds. <i>Islands in the Sky</i>, Wiley, 1996. <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-471-13561-5" title="Special:BookSources/0-471-13561-5">0-471-13561-5</a></li> <li>Webb, Stephen <i>If The Universe Is Teeming With Aliens ... Where Is Everybody? Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life</i> New York: January 2002 Springer-Verlag <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-387-95501-8" title="Special:BookSources/978-0-387-95501-8">978-0-387-95501-8</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Planetary_habitability&action=edit&section=36" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235611614">.mw-parser-output .spoken-wikipedia{border:1px solid #a2a9b1;background-color:var(--background-color-interactive-subtle,#f8f9fa);margin:0.5em 0;padding:0.2em;line-height:1.5em;font-size:90%}.mw-parser-output .spoken-wikipedia-header{text-align:center}.mw-parser-output .spoken-wikipedia-listen-to{font-weight:bold}.mw-parser-output .spoken-wikipedia-files{text-align:center;margin-top:10px;margin-bottom:0.4em}.mw-parser-output .spoken-wikipedia-icon{float:left;margin-left:5px;margin-top:10px}.mw-parser-output .spoken-wikipedia-disclaimer{margin-left:60px;margin-top:10px;font-size:95%;line-height:1.4em}.mw-parser-output .spoken-wikipedia-footer{margin-top:10px;text-align:center}@media(min-width:720px){.mw-parser-output .spoken-wikipedia{width:20em;float:right;clear:right;margin-left:1em}}</style><div class="spoken-wikipedia noprint haudio"><div class="spoken-wikipedia-header"><span class="spoken-wikipedia-listen-to">Listen to this article</span> (<span class="duration"><span class="min">32</span> minutes</span>)</div><div class="spoken-wikipedia-files"><figure class="mw-halign-center" typeof="mw:File"><span><audio id="mwe_player_1" controls="" preload="none" data-mw-tmh="" class="mw-file-element" width="200" style="width:200px;" data-durationhint="1925" data-mwtitle="PlanetaryHabitability.ogg" data-mwprovider="wikimediacommons"><source src="//upload.wikimedia.org/wikipedia/commons/8/82/PlanetaryHabitability.ogg" type="audio/ogg; codecs="vorbis"" data-width="0" data-height="0" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/8/82/PlanetaryHabitability.ogg/PlanetaryHabitability.ogg.mp3" type="audio/mpeg" data-transcodekey="mp3" data-width="0" data-height="0" /></audio></span><figcaption></figcaption></figure> </div><div class="spoken-wikipedia-icon"><span typeof="mw:File"><span title="Spoken Wikipedia"><img alt="Spoken Wikipedia icon" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/47/Sound-icon.svg/45px-Sound-icon.svg.png" decoding="async" width="45" height="34" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/47/Sound-icon.svg/68px-Sound-icon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/47/Sound-icon.svg/90px-Sound-icon.svg.png 2x" data-file-width="128" data-file-height="96" /></span></span></div><div class="spoken-wikipedia-disclaimer"><a href="/wiki/File:PlanetaryHabitability.ogg" title="File:PlanetaryHabitability.ogg">This audio file</a> was created from a revision of this article dated 22 January 2006<span style="display:none"> (<span class="bday dtstart published updated itvstart">2006-01-22</span>)</span>, and does not reflect subsequent edits.</div><div class="spoken-wikipedia-footer">(<a href="/wiki/Wikipedia:Media_help" class="mw-redirect" title="Wikipedia:Media help">Audio help</a> · <a href="/wiki/Wikipedia:Spoken_articles" title="Wikipedia:Spoken articles">More spoken articles</a>)</div></div> <ul><li><a rel="nofollow" class="external text" href="http://www.planetarysci.com">Planetary Sciences and Habitability Group, Spanish Research Council</a></li> <li><a rel="nofollow" class="external text" href="http://www.hzgallery.org">The Habitable Zone Gallery</a></li> <li><a rel="nofollow" class="external text" href="https://phl.upr.edu/">Planetary Habitability Laboratory</a> (PHL/<a href="/wiki/University_of_Puerto_Rico_at_Arecibo" title="University of Puerto Rico at Arecibo">UPR Arecibo</a>)</li> <li><a rel="nofollow" class="external text" href="https://phl.upr.edu/projects/habitable-exoplanets-catalog">The Habitable Exoplanets Catalog</a> (PHL/<a href="/wiki/University_of_Puerto_Rico_at_Arecibo" title="University of Puerto Rico at Arecibo">UPR Arecibo</a>)</li> <li><a rel="nofollow" class="external text" href="http://www.daviddarling.info/encyclopedia/ETEmain.html">David Darling encyclopedia</a></li> <li><a rel="nofollow" class="external text" href="http://www.astrobio.net">General interest astrobiology</a></li> <li><a rel="nofollow" class="external text" href="http://www.solstation.com">Sol Station</a></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · ";font-weight:bold}.mw-parser-output .hlist dd:last-child::after,.mw-parser-output .hlist dt:last-child::after,.mw-parser-output .hlist li:last-child::after{content:none}.mw-parser-output .hlist dd dd:first-child::before,.mw-parser-output .hlist dd dt:first-child::before,.mw-parser-output .hlist dd li:first-child::before,.mw-parser-output .hlist dt dd:first-child::before,.mw-parser-output .hlist dt dt:first-child::before,.mw-parser-output .hlist dt li:first-child::before,.mw-parser-output .hlist li dd:first-child::before,.mw-parser-output .hlist li dt:first-child::before,.mw-parser-output .hlist li li:first-child::before{content:" (";font-weight:normal}.mw-parser-output .hlist dd dd:last-child::after,.mw-parser-output .hlist dd dt:last-child::after,.mw-parser-output .hlist dd li:last-child::after,.mw-parser-output .hlist dt dd:last-child::after,.mw-parser-output .hlist dt dt:last-child::after,.mw-parser-output .hlist dt li:last-child::after,.mw-parser-output .hlist li dd:last-child::after,.mw-parser-output .hlist li dt:last-child::after,.mw-parser-output .hlist li li:last-child::after{content:")";font-weight:normal}.mw-parser-output .hlist ol{counter-reset:listitem}.mw-parser-output .hlist ol>li{counter-increment:listitem}.mw-parser-output .hlist ol>li::before{content:" "counter(listitem)"\a0 "}.mw-parser-output .hlist dd ol>li:first-child::before,.mw-parser-output .hlist dt ol>li:first-child::before,.mw-parser-output .hlist li ol>li:first-child::before{content:" ("counter(listitem)"\a0 "}</style><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output .navbox-title,.mw-parser-output .navbox-abovebelow{padding:0.25em 1em;line-height:1.5em;text-align:center}.mw-parser-output .navbox-group{white-space:nowrap;text-align:right}.mw-parser-output .navbox,.mw-parser-output .navbox-subgroup{background-color:#fdfdfd}.mw-parser-output .navbox-list{line-height:1.5em;border-color:#fdfdfd}.mw-parser-output .navbox-list-with-group{text-align:left;border-left-width:2px;border-left-style:solid}.mw-parser-output tr+tr>.navbox-abovebelow,.mw-parser-output tr+tr>.navbox-group,.mw-parser-output tr+tr>.navbox-image,.mw-parser-output tr+tr>.navbox-list{border-top:2px solid #fdfdfd}.mw-parser-output .navbox-title{background-color:#ccf}.mw-parser-output .navbox-abovebelow,.mw-parser-output .navbox-group,.mw-parser-output .navbox-subgroup .navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Astrobiology" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2" style="text-align: center;"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Astrobiology" title="Template:Astrobiology"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Astrobiology" title="Template talk:Astrobiology"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Astrobiology" title="Special:EditPage/Template:Astrobiology"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Astrobiology" style="font-size:114%;margin:0 4em"><a href="/wiki/Astrobiology" title="Astrobiology">Astrobiology</a></div></th></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Disciplines</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astrochemistry" title="Astrochemistry">Astrochemistry</a></li> <li><a href="/wiki/Astrophysics" title="Astrophysics">Astrophysics</a></li> <li><a href="/wiki/Atmospheric_sciences" class="mw-redirect" title="Atmospheric sciences">Atmospheric sciences</a></li> <li><a href="/wiki/Biochemistry" title="Biochemistry">Biochemistry</a></li> <li><a href="/wiki/Evolutionary_biology" title="Evolutionary biology">Evolutionary biology</a></li> <li><a href="/wiki/Exoplanetology" class="mw-redirect" title="Exoplanetology">Exoplanetology</a></li> <li><a href="/wiki/Geomicrobiology" title="Geomicrobiology">Geomicrobiology</a></li> <li><a href="/wiki/Microbiology" title="Microbiology">Microbiology</a></li> <li><a href="/wiki/Paleontology" title="Paleontology">Paleontology</a></li> <li><a href="/wiki/Planetary_oceanography" title="Planetary oceanography">Planetary oceanography</a></li> <li><a href="/wiki/Planetary_science" title="Planetary science">Planetary science</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Main topics</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Abiogenesis" title="Abiogenesis">Abiogenesis</a></li> <li><a href="/wiki/Allan_Hills_84001" title="Allan Hills 84001">Allan Hills 84001</a></li> <li><a href="/wiki/Biomolecule" title="Biomolecule">Biomolecule</a></li> <li><a href="/wiki/Biosignature" title="Biosignature">Biosignature</a></li> <li><a href="/wiki/Drake_equation" title="Drake equation">Drake equation</a></li> <li><a href="/wiki/Earliest_known_life_forms" title="Earliest known life forms">Earliest known life forms</a></li> <li><a href="/wiki/Earth_analog" title="Earth analog">Earth analog</a></li> <li><a href="/wiki/Extraterrestrial_life" title="Extraterrestrial life">Extraterrestrial life</a></li> <li><a href="/wiki/Extraterrestrial_sample_curation" title="Extraterrestrial sample curation">Extraterrestrial sample curation</a></li> <li><a href="/wiki/Extremophile" title="Extremophile">Extremophiles</a></li> <li><a href="/wiki/Hypothetical_types_of_biochemistry" title="Hypothetical types of biochemistry">Hypothetical types of biochemistry</a></li> <li><a href="/wiki/List_of_microorganisms_tested_in_outer_space" title="List of microorganisms tested in outer space">List of microorganisms tested in outer space</a></li> <li><a href="/wiki/Ocean_planet" class="mw-redirect" title="Ocean planet">Ocean planet</a></li> <li><a href="/wiki/Panspermia" title="Panspermia">Panspermia</a></li> <li><a href="/wiki/Planetary_protection" title="Planetary protection">Planetary protection</a></li> <li><a href="/wiki/Search_for_extraterrestrial_intelligence" title="Search for extraterrestrial intelligence">Search for extraterrestrial intelligence (SETI)</a></li> <li><a href="/wiki/Yamato_000593" title="Yamato 000593">Yamato meteorite</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a class="mw-selflink selflink">Planetary<br />habitability</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Circumstellar_habitable_zone" class="mw-redirect" title="Circumstellar habitable zone">Circumstellar habitable zone</a></li> <li><a href="/wiki/Earth_analog" title="Earth analog">Earth analog</a></li> <li><a href="/wiki/Extraterrestrial_liquid_water" title="Extraterrestrial liquid water">Extraterrestrial liquid water</a></li> <li><a href="/wiki/Galactic_habitable_zone" title="Galactic habitable zone">Galactic habitable zone</a></li> <li><a href="/wiki/Habitability_of_binary_star_systems" title="Habitability of binary star systems">Habitability of binary star systems</a></li> <li><a href="/wiki/Habitability_of_natural_satellites" title="Habitability of natural satellites">Habitability of natural satellites</a></li> <li><a href="/wiki/Habitability_of_neutron_star_systems" title="Habitability of neutron star systems">Habitability of neutron star systems</a></li> <li><a href="/wiki/Habitability_of_red_dwarf_systems" title="Habitability of red dwarf systems">Habitability of red dwarf systems</a></li> <li><a href="/wiki/Habitability_of_K-type_main-sequence_star_systems" title="Habitability of K-type main-sequence star systems">Habitability of K-type main-sequence star systems</a></li> <li><a href="/wiki/Habitability_of_yellow_dwarf_systems" title="Habitability of yellow dwarf systems">Habitability of yellow dwarf systems</a></li> <li><a href="/wiki/Habitability_of_F-type_main-sequence_star_systems" title="Habitability of F-type main-sequence star systems">Habitability of F-type main-sequence star systems</a></li> <li><a href="/wiki/Habitable_zone_for_complex_life" title="Habitable zone for complex life">Habitable zone for complex life</a></li> <li><a href="/wiki/List_of_potentially_habitable_exoplanets" title="List of potentially habitable exoplanets">List of potentially habitable exoplanets</a></li> <li><a href="/wiki/Tholin" title="Tholin">Tholin</a></li> <li><a href="/wiki/Superhabitable_planet" class="mw-redirect" title="Superhabitable planet">Superhabitable planet</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Space<br /> missions</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Earth orbit</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Space_Flyer_Unit#Experimentation_data" title="Space Flyer Unit">BIO</a></li> <li><a href="/wiki/Apollo_17#Biological_cosmic_ray_experiment" title="Apollo 17">BIOCORE</a></li> <li><a href="/wiki/Biolab" title="Biolab">Biolab</a></li> <li><a href="/wiki/Bion_(satellite)" title="Bion (satellite)">Bion</a></li> <li><a href="/wiki/BIOPAN" title="BIOPAN">BIOPAN</a></li> <li><a href="/wiki/Biosatellite_program" title="Biosatellite program">Biosatellite program</a></li> <li><a href="/wiki/Exposing_Microorganisms_in_the_Stratosphere" title="Exposing Microorganisms in the Stratosphere">E-MIST</a></li> <li><a href="/wiki/Exobiology_Radiation_Assembly" title="Exobiology Radiation Assembly">ERA</a></li> <li><a href="/wiki/EuCROPIS" title="EuCROPIS">Eu:CROPIS</a></li> <li><a href="/wiki/Long_Duration_Exposure_Facility#EXOSTACK" title="Long Duration Exposure Facility">EXOSTACK</a></li> <li><a href="/wiki/EXPOSE" title="EXPOSE">EXPOSE</a></li> <li><a href="/wiki/Chang%27e_4#Lunar_lander" title="Chang'e 4">Lunar Micro Ecosystem</a></li> <li><a href="/wiki/O/OREOS" title="O/OREOS">O/OREOS</a></li> <li><a href="/wiki/OREOcube" title="OREOcube">OREOcube</a></li> <li><a href="/wiki/Tanpopo_(mission)" class="mw-redirect" title="Tanpopo (mission)">Tanpopo</a></li> <li><a href="/wiki/Vegetable_Production_System" title="Vegetable Production System">VEGGIE</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Mars</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Beagle_2" title="Beagle 2">Beagle 2</a></li> <li><a href="/wiki/Fobos-Grunt" title="Fobos-Grunt">Fobos-Grunt</a></li> <li><a href="/wiki/Mars_Science_Laboratory" title="Mars Science Laboratory">Mars Science Laboratory</a> <ul><li><a href="/wiki/Curiosity_(rover)" title="Curiosity (rover)"><i>Curiosity</i> rover</a></li></ul></li> <li><a href="/wiki/Mars_2020" title="Mars 2020">Mars 2020</a> <ul><li><a href="/wiki/Perseverance_(rover)" title="Perseverance (rover)"><i>Perseverance</i> rover</a></li></ul></li> <li><i><a href="/wiki/Phoenix_(spacecraft)" title="Phoenix (spacecraft)">Phoenix</a></i></li> <li><a href="/wiki/Tianwen-1" title="Tianwen-1">Tianwen-1</a> <ul><li><a href="/wiki/Zhurong_(rover)" title="Zhurong (rover)"><i>Zhurong</i> rover</a></li></ul></li> <li><a href="/wiki/Trace_Gas_Orbiter" title="Trace Gas Orbiter">Trace Gas Orbiter</a></li> <li><a href="/wiki/Viking_lander_biological_experiments" title="Viking lander biological experiments">Viking</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Comets and<br />asteroids</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><i><a href="/wiki/Hayabusa2" title="Hayabusa2">Hayabusa2</a></i></li> <li><a href="/wiki/OSIRIS-REx" title="OSIRIS-REx">OSIRIS-REx</a></li> <li><i><a href="/wiki/Rosetta_(spacecraft)" title="Rosetta (spacecraft)">Rosetta</a></i></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Heliocentric</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/BioSentinel" title="BioSentinel">BioSentinel</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Planned</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><i><a href="/wiki/Dragonfly_(Titan_space_probe)" title="Dragonfly (Titan space probe)">Dragonfly</a></i></li> <li><a href="/wiki/Europa_Clipper" title="Europa Clipper">Europa Clipper</a></li> <li><a href="/wiki/ExoMars" title="ExoMars">ExoMars</a> <ul><li><a href="/wiki/Rosalind_Franklin_(rover)" title="Rosalind Franklin (rover)"><i>Rosalind Franklin</i> rover</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Proposed</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Breakthrough_Enceladus_mission" title="Breakthrough Enceladus mission">Breakthrough Enceladus</a></li> <li><a href="/wiki/BRUIE" title="BRUIE">BRUIE</a></li> <li><a href="/wiki/CAESAR_(spacecraft)" title="CAESAR (spacecraft)">CAESAR</a></li> <li><a href="/wiki/Enceladus_Explorer" title="Enceladus Explorer">Enceladus Explorer</a></li> <li><a href="/wiki/Enceladus_Life_Finder" title="Enceladus Life Finder">Enceladus Life Finder‎</a></li> <li><a href="/wiki/Enceladus_Life_Signatures_and_Habitability" title="Enceladus Life Signatures and Habitability">Enceladus Life Signatures and Habitability</a></li> <li><a href="/wiki/Enceladus_Orbilander" title="Enceladus Orbilander">Enceladus Orbilander</a></li> <li><a href="/wiki/Europa_Lander_(NASA)" class="mw-redirect" title="Europa Lander (NASA)">Europa Lander</a></li> <li><a href="/wiki/ExoLance" title="ExoLance">ExoLance</a></li> <li><a href="/wiki/Explorer_of_Enceladus_and_Titan" title="Explorer of Enceladus and Titan">Explorer of Enceladus and Titan</a></li> <li><a href="/wiki/Icebreaker_Life" title="Icebreaker Life">Icebreaker Life</a></li> <li><a href="/wiki/Journey_to_Enceladus_and_Titan" title="Journey to Enceladus and Titan">Journey to Enceladus and Titan</a></li> <li><a href="/wiki/Laplace-P" title="Laplace-P">Laplace-P</a></li> <li><a href="/wiki/Life_Investigation_For_Enceladus" title="Life Investigation For Enceladus">Life Investigation For Enceladus</a></li> <li><a href="/wiki/Mars_sample_return_mission" class="mw-redirect" title="Mars sample return mission">Mars sample return mission</a></li> <li><a href="/wiki/Oceanus_(Titan_orbiter)" title="Oceanus (Titan orbiter)">Oceanus</a></li> <li><a href="/wiki/THEO" title="THEO">THEO</a></li> <li><a href="/wiki/Trident_(spacecraft)" title="Trident (spacecraft)">Trident</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Cancelled and <br />undeveloped</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astrobiology_Field_Laboratory" title="Astrobiology Field Laboratory">Astrobiology Field Laboratory</a></li> <li><a href="/wiki/Beagle_3" title="Beagle 3">Beagle 3</a></li> <li><a href="/wiki/Biological_Oxidant_and_Life_Detection" title="Biological Oxidant and Life Detection">Biological Oxidant and Life Detection</a></li> <li><a href="/wiki/Kazachok" title="Kazachok">Kazachok</a></li> <li><a href="/wiki/Living_Interplanetary_Flight_Experiment" title="Living Interplanetary Flight Experiment">Living Interplanetary Flight Experiment</a></li> <li><a href="/wiki/Mars_Astrobiology_Explorer-Cacher" title="Mars Astrobiology Explorer-Cacher">Mars Astrobiology Explorer-Cacher</a></li> <li><a href="/wiki/MELOS" title="MELOS">MELOS</a></li> <li><a href="/wiki/Northern_Light_(spacecraft)" title="Northern Light (spacecraft)">Northern Light</a></li> <li><a href="/wiki/SpaceX_Red_Dragon" title="SpaceX Red Dragon">Red Dragon</a></li> <li><a href="/wiki/Terrestrial_Planet_Finder" title="Terrestrial Planet Finder">Terrestrial Planet Finder</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Institutions<br />and programs</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astrobiology_Society_of_Britain" title="Astrobiology Society of Britain">Astrobiology Society of Britain</a></li> <li><a href="/wiki/Astrobiology_Science_and_Technology_for_Exploring_Planets" title="Astrobiology Science and Technology for Exploring Planets">Astrobiology Science and Technology for Exploring Planets</a></li> <li><a href="/wiki/Breakthrough_Initiatives" title="Breakthrough Initiatives">Breakthrough Initiatives</a> <ul><li><a href="/wiki/Breakthrough_Listen" title="Breakthrough Listen">Breakthrough Listen</a></li> <li><a href="/wiki/Breakthrough_Message" class="mw-redirect" title="Breakthrough Message">Breakthrough Message</a></li> <li><a href="/wiki/Breakthrough_Starshot" title="Breakthrough Starshot">Breakthrough Starshot</a></li></ul></li> <li><a href="/wiki/Carl_Sagan_Institute" title="Carl Sagan Institute">Carl Sagan Institute</a></li> <li><a href="/wiki/Center_for_Life_Detection_Science" class="mw-redirect" title="Center for Life Detection Science">Center for Life Detection Science</a></li> <li><a href="/wiki/European_Astrobiology_Network_Association" title="European Astrobiology Network Association">European Astrobiology Network Association</a></li> <li><a href="/wiki/MERMOZ" title="MERMOZ">MERMOZ</a></li> <li><a href="/wiki/NASA_Astrobiology_Institute" title="NASA Astrobiology Institute">NASA Astrobiology Institute</a></li> <li><a href="/wiki/Nexus_for_Exoplanet_System_Science" title="Nexus for Exoplanet System Science">Nexus for Exoplanet System Science</a></li> <li><a href="/wiki/Ocean_Worlds_Exploration_Program" title="Ocean Worlds Exploration Program">Ocean Worlds Exploration Program</a></li> <li><a href="/wiki/Spanish_Astrobiology_Center" title="Spanish Astrobiology Center">Spanish Astrobiology Center‎</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2" style="text-align: center;"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <b><a href="/wiki/Category:Astrobiology" title="Category:Astrobiology">Category</a></b></li> <li><span class="noviewer" typeof="mw:File"><span title="Commons page"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/12px-Commons-logo.svg.png" decoding="async" width="12" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/18px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/24px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></span></span> <b><a href="https://commons.wikimedia.org/wiki/Category:Astrobiology" class="extiw" title="commons:Category:Astrobiology">Commons</a></b></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Extraterrestrial_life" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2" style="text-align: center;"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Extraterrestrial_life" title="Template:Extraterrestrial life"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Extraterrestrial_life" title="Template talk:Extraterrestrial life"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Extraterrestrial_life" title="Special:EditPage/Template:Extraterrestrial life"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Extraterrestrial_life" style="font-size:114%;margin:0 4em"><a href="/wiki/Extraterrestrial_life" title="Extraterrestrial life">Extraterrestrial life</a></div></th></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Events and objects</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Shergotty_meteorite" title="Shergotty meteorite">Shergotty meteorite</a> (1865)</li> <li><a href="/wiki/Nakhla_meteorite" title="Nakhla meteorite">Nakhla meteorite</a> (1911)</li> <li><a href="/wiki/Murchison_meteorite" title="Murchison meteorite">Murchison meteorite</a> (1969)</li> <li><a href="/wiki/Viking_lander_biological_experiments" title="Viking lander biological experiments">Viking lander biological experiments</a> (1976)</li> <li><a href="/wiki/Allan_Hills_77005" title="Allan Hills 77005">Allan Hills 77005</a> (1977)</li> <li><a href="/wiki/Allan_Hills_84001" title="Allan Hills 84001">Allan Hills 84001</a> (1984)</li> <li><a href="/wiki/Yamato_000593" title="Yamato 000593">Yamato 000593</a> (2000)</li> <li><a href="/wiki/CI1_fossils" title="CI1 fossils">CI1 fossils</a> (2011)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Signals of interest</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Misidentified</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/PSR_B1919%2B21" title="PSR B1919+21">CP 1919</a> <span style="font-size:85%;">(misidentified pulsar)</span></li> <li><a href="/wiki/CTA-102" title="CTA-102">CTA-102</a> <span style="font-size:85%;">(misidentified quasar)</span></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Stars</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Tabby%27s_Star" title="Tabby's Star">KIC 8462852</a> <span style="font-size:85%;">(unusual light fluctuations)</span></li> <li><a href="/wiki/EPIC_204278916" title="EPIC 204278916">EPIC 204278916</a> <span style="font-size:85%;">(unusual light fluctuations)</span></li> <li><a href="/wiki/VVV-WIT-07" title="VVV-WIT-07">VVV-WIT-07</a> <span style="font-size:85%;">(unusual light fluctuations)</span></li> <li><a href="/wiki/HD_164595" title="HD 164595">HD 164595 signal</a> <span style="font-size:85%;">(unknown origin)</span></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Other</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/SHGb02%2B14a" title="SHGb02+14a">SHGb02+14a</a> <span style="font-size:85%;">(radio source)</span></li> <li><a href="/wiki/Wow!_signal" title="Wow! signal">Wow! signal</a> <span style="font-size:85%;">(inconclusive)</span></li> <li><a href="/wiki/Fast_radio_burst" title="Fast radio burst">Fast radio burst</a> <span style="font-size:85%;">(unknown origin)</span></li> <li><a href="/wiki/BLC1" title="BLC1">BLC1</a> <span style="font-size:85%;">(radio signal)</span></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Life in the Universe</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Earliest_known_life_forms" title="Earliest known life forms">Earliest known life forms</a></li> <li><a href="/wiki/Planetary_habitability_in_the_Solar_System" title="Planetary habitability in the Solar System">Planetary habitability in the Solar System</a></li> <li><a href="/wiki/Life_on_Venus" title="Life on Venus">Life on Venus</a></li> <li><a href="/wiki/Life_on_Mars" title="Life on Mars">Life on Mars</a></li> <li><a href="/wiki/Life_on_Titan" title="Life on Titan">Life on Titan</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a class="mw-selflink selflink">Planetary<br />habitability</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Catalog_of_Nearby_Habitable_Systems" title="Catalog of Nearby Habitable Systems">Catalog of Nearby Habitable Systems</a></li> <li><a href="/wiki/Circumstellar_habitable_zone" class="mw-redirect" title="Circumstellar habitable zone">Circumstellar habitable zone</a></li> <li><a href="/wiki/Earth_analog" title="Earth analog">Earth analog</a></li> <li><a href="/wiki/Extraterrestrial_liquid_water" title="Extraterrestrial liquid water">Extraterrestrial liquid water</a></li> <li><a href="/wiki/Galactic_habitable_zone" title="Galactic habitable zone">Galactic habitable zone</a></li> <li><a href="/wiki/Habitability_of_binary_star_systems" title="Habitability of binary star systems">Habitability of binary star systems</a></li> <li><a href="/wiki/Habitability_of_natural_satellites" title="Habitability of natural satellites">Habitability of natural satellites</a></li> <li><a href="/wiki/Habitability_of_neutron_star_systems" title="Habitability of neutron star systems">Habitability of neutron star systems</a></li> <li><a href="/wiki/Habitability_of_red_dwarf_systems" title="Habitability of red dwarf systems">Habitability of red dwarf systems</a></li> <li><a href="/wiki/Habitability_of_K-type_main-sequence_star_systems" title="Habitability of K-type main-sequence star systems">Habitability of K-type main-sequence star systems</a></li> <li><a href="/wiki/Habitability_of_yellow_dwarf_systems" title="Habitability of yellow dwarf systems">Habitability of yellow dwarf systems</a></li> <li><a href="/wiki/Habitability_of_F-type_main-sequence_star_systems" title="Habitability of F-type main-sequence star systems">Habitability of F-type main-sequence star systems</a></li> <li><a href="/wiki/List_of_potentially_habitable_exoplanets" title="List of potentially habitable exoplanets">List of potentially habitable exoplanets</a></li> <li><a class="mw-selflink selflink">Planetary habitability</a></li> <li><a href="/wiki/Superhabitable_planet" class="mw-redirect" title="Superhabitable planet">Superhabitable planet</a></li> <li><a href="/wiki/Tholin" title="Tholin">Tholin</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/Astrobiology#Missions" title="Astrobiology">Space missions</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Beagle_2" title="Beagle 2">Beagle 2</a></li> <li><a href="/wiki/Biological_Oxidant_and_Life_Detection" title="Biological Oxidant and Life Detection">Biological Oxidant and Life Detection</a></li> <li><a href="/wiki/BioSentinel" title="BioSentinel">BioSentinel</a></li> <li><a href="/wiki/Curiosity_(rover)" title="Curiosity (rover)"><i>Curiosity</i> rover</a></li> <li><i><a href="/wiki/Darwin_(spacecraft)" title="Darwin (spacecraft)">Darwin</a></i></li> <li><i><a href="/wiki/Dragonfly_(Titan_space_probe)" title="Dragonfly (Titan space probe)">Dragonfly</a></i></li> <li><a href="/wiki/Enceladus_Explorer" title="Enceladus Explorer">Enceladus Explorer</a></li> <li><a href="/wiki/Enceladus_Life_Finder" title="Enceladus Life Finder">Enceladus Life Finder</a></li> <li><i><a href="/wiki/Europa_Clipper" title="Europa Clipper">Europa Clipper</a></i></li> <li><a href="/wiki/ExoMars" title="ExoMars">ExoMars</a> <ul><li><a href="/wiki/Rosalind_Franklin_(rover)" title="Rosalind Franklin (rover)"><i>Rosalind Franklin</i> rover</a></li></ul></li> <li><a href="/wiki/ExoLance" title="ExoLance">ExoLance</a></li> <li><a href="/wiki/EXPOSE" title="EXPOSE">EXPOSE</a></li> <li><a href="/wiki/Foton-M" class="mw-redirect" title="Foton-M">Foton-M3</a></li> <li><a href="/wiki/Icebreaker_Life" title="Icebreaker Life">Icebreaker Life</a></li> <li><a href="/wiki/Journey_to_Enceladus_and_Titan" title="Journey to Enceladus and Titan">Journey to Enceladus and Titan</a></li> <li><a href="/wiki/Laplace-P" title="Laplace-P">Laplace-P</a></li> <li><a href="/wiki/Life_Investigation_For_Enceladus" title="Life Investigation For Enceladus">Life Investigation For Enceladus</a></li> <li><a href="/wiki/Living_Interplanetary_Flight_Experiment" title="Living Interplanetary Flight Experiment">Living Interplanetary Flight Experiment</a></li> <li><a href="/wiki/Mars_Geyser_Hopper" title="Mars Geyser Hopper">Mars Geyser Hopper</a></li> <li><a href="/wiki/Mars_sample-return_mission" title="Mars sample-return mission">Mars sample-return mission</a></li> <li><a href="/wiki/Mars_2020" title="Mars 2020">Mars 2020</a></li> <li><a href="/wiki/Northern_Light_(spacecraft)" title="Northern Light (spacecraft)">Northern Light</a></li> <li><a href="/wiki/Opportunity_(rover)" title="Opportunity (rover)"><i>Opportunity</i> rover</a></li> <li><a href="/wiki/Perseverance_(rover)" title="Perseverance (rover)"><i>Perseverance</i> rover</a></li> <li><a href="/wiki/SpaceX_Red_Dragon" title="SpaceX Red Dragon">SpaceX Red Dragon</a></li> <li><a href="/wiki/Spirit_(rover)" title="Spirit (rover)"><i>Spirit</i> rover</a></li> <li><a href="/wiki/Tanpopo_mission" title="Tanpopo mission">Tanpopo</a></li> <li><a href="/wiki/Titan_Mare_Explorer" title="Titan Mare Explorer">Titan Mare Explorer</a></li> <li><a href="/wiki/Venus_In_Situ_Explorer" title="Venus In Situ Explorer">Venus In Situ Explorer</a></li> <li><i><a href="/wiki/Viking_1" title="Viking 1">Viking 1</a></i></li> <li><i><a href="/wiki/Viking_2" title="Viking 2">Viking 2</a></i></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/Interstellar_communication" title="Interstellar communication">Interstellar<br />communication</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Active_SETI" title="Active SETI">Active SETI</a></li> <li><a href="/wiki/Allen_Telescope_Array" title="Allen Telescope Array">Allen Telescope Array</a></li> <li><a href="/wiki/Arecibo_message" title="Arecibo message">Arecibo message</a></li> <li><a href="/wiki/Arecibo_Observatory" title="Arecibo Observatory">Arecibo Observatory</a></li> <li><a href="/wiki/Berkeley_SETI_Research_Center" title="Berkeley SETI Research Center">Berkeley SETI Research Center</a></li> <li><a href="/wiki/Bracewell_probe" title="Bracewell probe">Bracewell probe</a></li> <li><a href="/wiki/Breakthrough_Initiatives" title="Breakthrough Initiatives">Breakthrough Initiatives</a> <ul><li><a href="/wiki/Breakthrough_Listen" title="Breakthrough Listen">Breakthrough Listen</a></li> <li><a href="/wiki/Breakthrough_Message" class="mw-redirect" title="Breakthrough Message">Breakthrough Message</a></li></ul></li> <li><a href="/wiki/Communication_with_extraterrestrial_intelligence" title="Communication with extraterrestrial intelligence">Communication with extraterrestrial intelligence</a></li> <li><a href="/wiki/Gauss%27s_Pythagorean_right_triangle_proposal" title="Gauss's Pythagorean right triangle proposal">Gauss's Pythagorean right triangle proposal</a></li> <li><a href="/wiki/Astrolinguistics" title="Astrolinguistics">Astrolinguistics</a></li> <li><a href="/wiki/Lincos_language" title="Lincos language">Lincos language</a></li> <li><a href="/wiki/NIROSETI" title="NIROSETI">NIROSETI</a></li> <li><a href="/wiki/Pioneer_plaque" title="Pioneer plaque">Pioneer plaque</a></li> <li><a href="/wiki/Project_Cyclops" title="Project Cyclops">Project Cyclops</a></li> <li><a href="/wiki/Project_Ozma" title="Project Ozma">Project Ozma</a></li> <li><a href="/wiki/Project_Phoenix_(SETI)" title="Project Phoenix (SETI)">Project Phoenix</a></li> <li><a href="/wiki/SERENDIP" title="SERENDIP">SERENDIP</a></li> <li><a href="/wiki/Search_for_extraterrestrial_intelligence" title="Search for extraterrestrial intelligence">Search for extraterrestrial intelligence</a></li> <li><a href="/wiki/SETI@home" title="SETI@home">SETI@home</a></li> <li><a href="/wiki/SetiQuest" title="SetiQuest">setiQuest</a></li> <li><a href="/wiki/Voyager_Golden_Record" title="Voyager Golden Record">Voyager Golden Record</a></li> <li><a href="/wiki/Water_hole_(radio)" title="Water hole (radio)">Water hole</a></li> <li><a href="/wiki/Alien_language" title="Alien language">Xenolinguistics</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/List_of_alleged_extraterrestrial_beings" title="List of alleged extraterrestrial beings">Types of alleged<br /> extraterrestrial beings</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Energy_being" title="Energy being">Energy beings</a></li> <li><a href="/wiki/Grey_alien" title="Grey alien">Grey aliens</a></li> <li><a href="/wiki/Insectoids_in_science_fiction" class="mw-redirect" title="Insectoids in science fiction">Insectoids</a></li> <li><a href="/wiki/Little_green_men" title="Little green men">Little green men</a></li> <li><a href="/wiki/Nordic_aliens" title="Nordic aliens">Nordic aliens</a></li> <li><a href="/wiki/Reptilian_humanoid" title="Reptilian humanoid">Reptilian humanoids</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Hypotheses</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cosmic_pluralism" title="Cosmic pluralism">Cosmic pluralism</a></li> <li><a href="/wiki/Directed_panspermia" title="Directed panspermia">Directed panspermia</a></li> <li><a href="/wiki/Drake_equation" title="Drake equation">Drake equation</a></li> <li><a href="/wiki/Extraterrestrial_hypothesis" class="mw-redirect" title="Extraterrestrial hypothesis">Extraterrestrial hypothesis</a></li> <li><a href="/wiki/Fermi_paradox" title="Fermi paradox">Fermi paradox</a></li> <li><a href="/wiki/Hypothetical_types_of_biochemistry" title="Hypothetical types of biochemistry">Hypothetical types of biochemistry</a></li> <li><a href="/wiki/Interplanetary_contamination" title="Interplanetary contamination">Interplanetary contamination</a></li> <li><a href="/wiki/Kardashev_scale" title="Kardashev scale">Kardashev scale</a></li> <li><a href="/wiki/Mediocrity_principle" title="Mediocrity principle">Mediocrity principle</a></li> <li><a href="/wiki/Panspermia" title="Panspermia">Panspermia</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/Fermi_paradox" title="Fermi paradox">Fermi paradox</a> solutions</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Aestivation_hypothesis" title="Aestivation hypothesis">Aestivation hypothesis</a></li> <li><a href="/wiki/Berserker_hypothesis" title="Berserker hypothesis">Berserker hypothesis</a></li> <li><a href="/wiki/Dark_forest_hypothesis" title="Dark forest hypothesis">Dark forest hypothesis</a></li> <li><a href="/wiki/Firstborn_hypothesis" title="Firstborn hypothesis">Firstborn hypothesis</a></li> <li><a href="/wiki/Great_Filter" title="Great Filter">Great Filter</a></li> <li><a href="/wiki/Hart%E2%80%93Tipler_conjecture" title="Hart–Tipler conjecture">Hart–Tipler conjecture</a></li> <li><a href="/wiki/Neocatastrophism" title="Neocatastrophism">Neocatastrophism</a></li> <li><a href="/wiki/Planetarium_hypothesis" title="Planetarium hypothesis">Planetarium hypothesis</a></li> <li><a href="/wiki/Rare_Earth_hypothesis" title="Rare Earth hypothesis">Rare Earth hypothesis</a></li> <li><a href="/wiki/Zoo_hypothesis" title="Zoo hypothesis">Zoo hypothesis</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/Outline_of_extraterrestrial_life" title="Outline of extraterrestrial life">Related topics</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ancient_astronauts" title="Ancient astronauts">Ancient astronauts</a></li> <li><a href="/wiki/Astrobiology" title="Astrobiology">Astrobiology</a></li> <li><a href="/wiki/Astroecology" title="Astroecology">Astroecology</a></li> <li><a href="/wiki/Biosignature" title="Biosignature">Biosignature</a></li> <li><a href="/wiki/Brookings_Report" title="Brookings Report">Brookings Report</a></li> <li><a href="/wiki/Exotheology" title="Exotheology">Exotheology</a></li> <li><a href="/wiki/Extraterrestrials_in_fiction" title="Extraterrestrials in fiction">Extraterrestrials in fiction</a></li> <li><a href="/wiki/Extremophile" title="Extremophile">Extremophile</a></li> <li><a href="/wiki/Hemolithin" title="Hemolithin">Hemolithin</a></li> <li><a href="/wiki/History_of_the_extraterrestrial_life_debate" title="History of the extraterrestrial life debate">History of the extraterrestrial life debate</a></li> <li><a href="/wiki/MERMOZ" title="MERMOZ">MERMOZ</a></li> <li><a href="/wiki/Nexus_for_Exoplanet_System_Science" title="Nexus for Exoplanet System Science">Nexus for Exoplanet System Science</a></li> <li><a href="/wiki/Noosphere" title="Noosphere">Noogenesis</a></li> <li><a href="/wiki/Planetary_protection" title="Planetary protection">Planetary protection</a></li> <li><a href="/wiki/Potential_cultural_impact_of_extraterrestrial_contact" title="Potential cultural impact of extraterrestrial contact">Potential cultural impact of extraterrestrial contact</a></li> <li><a href="/wiki/Post-detection_policy" title="Post-detection policy">Post-detection policy</a></li> <li><a href="/wiki/San_Marino_Scale" title="San Marino Scale">San Marino Scale</a></li> <li><a href="/wiki/Technosignature" title="Technosignature">Technosignature</a></li> <li><a href="/wiki/UFO_religion" title="UFO religion">UFO religion</a></li> <li><a href="/wiki/Xenoarchaeology" title="Xenoarchaeology">Xenoarchaeology</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Exoplanets" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="3"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Exoplanet" title="Template:Exoplanet"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Exoplanet" title="Template talk:Exoplanet"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Exoplanet" title="Special:EditPage/Template:Exoplanet"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Exoplanets" style="font-size:114%;margin:0 4em">Exoplanets</div></th></tr><tr><td class="navbox-abovebelow" colspan="3"><div> <ul><li><a href="/wiki/Planet" title="Planet">Planet</a> <ul><li><a href="/wiki/Definition_of_planet" title="Definition of planet">Definition</a> <ul><li><a href="/wiki/IAU_definition_of_planet" title="IAU definition of planet">IAU</a></li></ul></li></ul></li> <li><a href="/wiki/Planetary_science" title="Planetary science">Planetary science</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:right;">Main topics</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Exoplanet" title="Exoplanet">Exoplanet</a></li> <li><a href="/wiki/Exoplanet_orbital_and_physical_parameters" title="Exoplanet orbital and physical parameters">Exoplanet orbital and physical parameters</a></li> <li><a href="/wiki/Methods_of_detecting_exoplanets" title="Methods of detecting exoplanets">Methods of detecting exoplanets</a></li> <li><a href="/wiki/Planetary_system" title="Planetary system">Planetary system</a></li> <li><a href="/wiki/Planet-hosting_star" title="Planet-hosting star">Planet-hosting stars</a></li></ul> </div></td><td class="noviewer navbox-image" rowspan="10" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"><a href="/wiki/PDS_70" title="PDS 70"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/PDS_70.jpg/100px-PDS_70.jpg" decoding="async" width="100" height="85" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/PDS_70.jpg/150px-PDS_70.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1c/PDS_70.jpg/200px-PDS_70.jpg 2x" data-file-width="2000" data-file-height="1692" /></a></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:right;">Sizes<br />and <br /><a href="/wiki/List_of_planet_types" title="List of planet types">types</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%;text-align:center;"><a href="/wiki/Terrestrial_planet" title="Terrestrial planet">Terrestrial</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Carbon_planet" title="Carbon planet">Carbon planet</a></li> <li><a href="/wiki/Coreless_planet" title="Coreless planet">Coreless planet</a></li> <li><a href="/wiki/Desert_planet" title="Desert planet">Desert planet</a></li> <li><a href="/wiki/Dwarf_planet" title="Dwarf planet">Dwarf planet</a></li> <li><a href="/wiki/Hycean_planet" title="Hycean planet">Hycean planet</a></li> <li><a href="/wiki/Ice_planet" title="Ice planet">Ice planet</a></li> <li><a href="/wiki/Iron_planet" title="Iron planet">Iron planet</a> (Super-Mercury)</li> <li><a href="/wiki/Lava_planet" title="Lava planet">Lava planet</a></li> <li><a href="/wiki/Ocean_world" title="Ocean world">Ocean world</a></li> <li><a href="/wiki/Mega-Earth" title="Mega-Earth">Mega-Earth</a></li> <li><a href="/wiki/Sub-Earth" title="Sub-Earth">Sub-Earth</a></li> <li><a href="/wiki/Super-Earth" title="Super-Earth">Super-Earth</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:center;"><a href="/wiki/Gas_giant" title="Gas giant">Gaseous</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Eccentric_Jupiter" title="Eccentric Jupiter">Eccentric Jupiter</a></li> <li><a href="/wiki/Mini-Neptune" title="Mini-Neptune">Mini-Neptune</a> (Gas dwarf)</li> <li><a href="/wiki/Helium_planet" title="Helium planet">Helium planet</a></li> <li><a href="/wiki/Hot_Jupiter" title="Hot Jupiter">Hot Jupiter</a></li> <li><a href="/wiki/Hot_Neptune" title="Hot Neptune">Hot Neptune</a></li> <li><a href="/wiki/Gas_giant" title="Gas giant">Gas giant</a></li> <li><a href="/wiki/Ice_giant" title="Ice giant">Ice giant</a></li> <li><a href="/wiki/Super-Jupiter" title="Super-Jupiter">Super-Jupiter</a></li> <li><a href="/wiki/Super-Neptune" title="Super-Neptune">Super-Neptune</a></li> <li><a href="/wiki/Super-puff" title="Super-puff">Super-puff</a></li> <li><a href="/wiki/Ultra-hot_Jupiter" class="mw-redirect" title="Ultra-hot Jupiter">Ultra-hot Jupiter</a></li> <li><a href="/wiki/Ultra-hot_Neptune" class="mw-redirect" title="Ultra-hot Neptune">Ultra-hot Neptune</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:center;">Other types</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Blanet" title="Blanet">Blanet</a></li> <li><a href="/wiki/Brown_dwarf" title="Brown dwarf">Brown dwarf</a></li> <li><a href="/wiki/Chthonian_planet" title="Chthonian planet">Chthonian planet</a></li> <li><a href="/wiki/Circumbinary_planet" title="Circumbinary planet">Circumbinary planet</a></li> <li><a href="/wiki/Circumtriple_planet" title="Circumtriple planet">Circumtriple planet</a></li> <li><a href="/wiki/Disrupted_planet" title="Disrupted planet">Disrupted planet</a></li> <li><a href="/wiki/Double_planet" title="Double planet">Double planet</a></li> <li><a href="/wiki/Ecumenopolis" title="Ecumenopolis">Ecumenopolis</a></li> <li><a href="/wiki/Eyeball_planet" title="Eyeball planet">Eyeball planet</a></li> <li><a href="/wiki/Giant_planet" title="Giant planet">Giant planet</a></li> <li><a href="/wiki/Mesoplanet" title="Mesoplanet">Mesoplanet</a></li> <li><a href="/wiki/Planetary-mass_object" title="Planetary-mass object">Planemo</a></li> <li><a href="/wiki/Brown_dwarf#Low-mass_brown_dwarfs_versus_high-mass_planets" title="Brown dwarf">Planet/Brown dwarf boundary</a></li> <li><a href="/wiki/Planetesimal" title="Planetesimal">Planetesimal</a></li> <li><a href="/wiki/Protoplanet" title="Protoplanet">Protoplanet</a></li> <li><a href="/wiki/Pulsar_planet" title="Pulsar planet">Pulsar planet</a></li> <li><a href="/wiki/Sub-brown_dwarf" title="Sub-brown dwarf">Sub-brown dwarf</a></li> <li><a href="/wiki/Sub-Neptune" title="Sub-Neptune">Sub-Neptune</a></li> <li><a href="/wiki/Toroidal_planet" title="Toroidal planet">Toroidal planet</a></li> <li><a href="/wiki/Ultra-cool_dwarf" title="Ultra-cool dwarf">Ultra-cool dwarf</a></li> <li><a href="/wiki/Ultra-short_period_planet" title="Ultra-short period planet">Ultra-short period planet (USP)</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:right;"><a href="/wiki/Formation_and_evolution_of_the_Solar_System" title="Formation and evolution of the Solar System">Formation <br />and <br />evolution</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Accretion_(astrophysics)" title="Accretion (astrophysics)">Accretion</a></li> <li><a href="/wiki/Accretion_disk" title="Accretion disk">Accretion disk</a></li> <li><a href="/wiki/Asteroid_belt" title="Asteroid belt">Asteroid belt</a></li> <li><a href="/wiki/Circumplanetary_disk" title="Circumplanetary disk">Circumplanetary disk</a></li> <li><a href="/wiki/Circumstellar_disc" title="Circumstellar disc">Circumstellar disc</a></li> <li><a href="/wiki/Circumstellar_envelope" title="Circumstellar envelope">Circumstellar envelope</a></li> <li><a href="/wiki/Cosmic_dust" title="Cosmic dust">Cosmic dust</a></li> <li><a href="/wiki/Debris_disk" title="Debris disk">Debris disk</a></li> <li><a href="/wiki/Detached_object" title="Detached object">Detached object</a></li> <li><a href="/wiki/Disrupted_planet" title="Disrupted planet">Disrupted planet</a></li> <li><a href="/wiki/Accretion_disk#Excretion_disk" title="Accretion disk">Excretion disk</a></li> <li><a href="/wiki/Exozodiacal_dust" title="Exozodiacal dust">Exozodiacal dust</a></li> <li><a href="/wiki/Extraterrestrial_materials" title="Extraterrestrial materials">Extraterrestrial materials</a></li> <li><a href="/wiki/Extraterrestrial_sample_curation" title="Extraterrestrial sample curation">Extraterrestrial sample curation</a></li> <li><a href="/wiki/Giant-impact_hypothesis" title="Giant-impact hypothesis">Giant-impact hypothesis</a></li> <li><a href="/wiki/Gravitational_collapse" title="Gravitational collapse">Gravitational collapse</a></li> <li><a href="/wiki/Hills_cloud" title="Hills cloud">Hills cloud</a></li> <li><a href="/wiki/Exoplanet_interiors" title="Exoplanet interiors">Internal structure</a></li> <li><a href="/wiki/Interplanetary_dust_cloud" title="Interplanetary dust cloud">Interplanetary dust cloud</a></li> <li><a href="/wiki/Interplanetary_medium" title="Interplanetary medium">Interplanetary medium</a></li> <li><a href="/wiki/Interplanetary_space" class="mw-redirect" title="Interplanetary space">Interplanetary space</a></li> <li><a href="/wiki/Interstellar_cloud" title="Interstellar cloud">Interstellar cloud</a></li> <li><a href="/wiki/Interstellar_dust" class="mw-redirect" title="Interstellar dust">Interstellar dust</a></li> <li><a href="/wiki/Interstellar_medium" title="Interstellar medium">Interstellar medium</a></li> <li><a href="/wiki/Outer_space#Interstellar_space" title="Outer space">Interstellar space</a></li> <li><a href="/wiki/Kuiper_belt" title="Kuiper belt">Kuiper belt</a></li> <li><a href="/wiki/List_of_interstellar_and_circumstellar_molecules" title="List of interstellar and circumstellar molecules">List of interstellar and circumstellar molecules</a></li> <li><a href="/wiki/Stellar_collision#Formation_of_planets" title="Stellar collision">Merging stars</a></li> <li><a href="/wiki/Molecular_cloud" title="Molecular cloud">Molecular cloud</a></li> <li><a href="/wiki/Nebular_hypothesis" title="Nebular hypothesis">Nebular hypothesis</a></li> <li><a href="/wiki/Oort_cloud" title="Oort cloud">Oort cloud</a></li> <li><a href="/wiki/Outer_space" title="Outer space">Outer space</a></li> <li><a href="/wiki/Planetary_migration" title="Planetary migration">Planetary migration</a></li> <li><a href="/wiki/Planetary_system" title="Planetary system">Planetary system</a></li> <li><a href="/wiki/Planetesimal" title="Planetesimal">Planetesimal</a></li> <li><a href="/wiki/Nebular_hypothesis#Formation_of_planets" title="Nebular hypothesis">Planet formation</a></li> <li><a href="/wiki/Protoplanetary_disk" title="Protoplanetary disk">Protoplanetary disk</a></li> <li><a href="/wiki/Ring_system" title="Ring system">Ring system</a></li> <li><a href="/wiki/Rubble_pile" title="Rubble pile">Rubble pile</a></li> <li><a href="/wiki/Sample-return_mission" title="Sample-return mission">Sample-return mission</a></li> <li><a href="/wiki/Scattered_disc" title="Scattered disc">Scattered disc</a></li> <li><a href="/wiki/Star_formation" title="Star formation">Star formation</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:right;"><a href="/wiki/Planetary_system" title="Planetary system">Systems</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Exocomet" title="Exocomet">Exocomet</a> <ul><li><a href="/wiki/Interstellar_comet" class="mw-redirect" title="Interstellar comet">Interstellar</a></li></ul></li> <li><a href="/wiki/Exomoon" title="Exomoon">Exomoon</a> <ul><li><a href="/wiki/Tidally_detached_exomoon" title="Tidally detached exomoon">Tidally detached</a></li></ul></li> <li><a href="/wiki/Rogue_planet" title="Rogue planet">Rogue planet</a></li> <li>Orbits <ul><li><a href="/wiki/Retrograde_and_prograde_motion#Exoplanets" title="Retrograde and prograde motion">Retrograde</a></li> <li><a href="/wiki/Co-orbital_configuration#Trojans" title="Co-orbital configuration">Trojan</a></li> <li><a href="/wiki/Orbital_resonance#Mean-motion_resonances_among_extrasolar_planets" title="Orbital resonance">Mean-motion resonances</a></li> <li><a href="/wiki/Titius%E2%80%93Bode_law#Lunar_systems_and_other_planetary_systems" title="Titius–Bode law">Titius–Bode law</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:right;"><a href="/wiki/Planetary_system#Planet-hosting_stars" title="Planetary system">Host stars</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/A-type_main-sequence_star#Planets" title="A-type main-sequence star">A</a></li> <li><a href="/wiki/B-type_main-sequence_star#Planets" title="B-type main-sequence star">B</a></li> <li><a href="/wiki/Binary_star#Planets" title="Binary star">Binary star</a></li> <li><a href="/wiki/Brown_dwarf#Planets_around_brown_dwarfs" title="Brown dwarf">Brown dwarfs</a></li> <li><a href="/wiki/F-type_main-sequence_star#Planets" title="F-type main-sequence star">F/Yellow-white dwarfs</a></li> <li><a href="/wiki/G-type_main-sequence_star#Planets" title="G-type main-sequence star">G/Yellow dwarfs</a></li> <li><a href="/wiki/Herbig_Ae/Be_star#Planets" title="Herbig Ae/Be star">Herbig Ae/Be</a></li> <li><a href="/wiki/K-type_main-sequence_star#Planets" title="K-type main-sequence star">K/Orange dwarfs</a></li> <li><a href="/wiki/Red_dwarf#Planets" title="Red dwarf">M/Red dwarfs</a></li> <li><a href="/wiki/Pulsar_planet" title="Pulsar planet">Pulsar</a></li> <li><a href="/wiki/Red_giant#Planets" title="Red giant">Red giant</a></li> <li><a href="/wiki/Subdwarf_B_star#Planetary_systems" title="Subdwarf B star">Subdwarf B</a></li> <li><a href="/wiki/Subgiant#Planets" title="Subgiant">Subgiant</a></li> <li><a href="/wiki/T_Tauri_star#Planets" title="T Tauri star">T Tauri</a></li> <li><a href="/wiki/White_dwarf#Debris_disks_and_planets" title="White dwarf">White dwarfs</a></li> <li><a href="/wiki/Yellow_giant#Planets" class="mw-redirect" title="Yellow giant">Yellow giants</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:right;"><a href="/wiki/Methods_of_detecting_exoplanets" title="Methods of detecting exoplanets">Detection</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astrometry" title="Astrometry">Astrometry</a></li> <li><a href="/wiki/Methods_of_detecting_exoplanets#Direct_imaging" title="Methods of detecting exoplanets">Direct imaging</a> <ul><li><a href="/wiki/List_of_directly_imaged_exoplanets" title="List of directly imaged exoplanets">list</a></li></ul></li> <li><a href="/wiki/Gravitational_microlensing" title="Gravitational microlensing">Microlensing</a> <ul><li><a href="/wiki/List_of_exoplanets_detected_by_microlensing" title="List of exoplanets detected by microlensing">list</a></li></ul></li> <li><a href="/wiki/Polarimetry" title="Polarimetry">Polarimetry</a></li> <li><a href="/wiki/Methods_of_detecting_exoplanets#Pulsar_timing" title="Methods of detecting exoplanets">Timing</a> <ul><li><a href="/wiki/List_of_exoplanets_detected_by_timing" title="List of exoplanets detected by timing">list</a></li></ul></li> <li><a href="/wiki/Doppler_spectroscopy" title="Doppler spectroscopy">Radial velocity</a> <ul><li><a href="/wiki/List_of_exoplanets_detected_by_radial_velocity" title="List of exoplanets detected by radial velocity">list</a></li></ul></li> <li><a href="/wiki/Methods_of_detecting_exoplanets#Transit_photometry" title="Methods of detecting exoplanets">Transit method</a> <ul><li><a href="/wiki/List_of_transiting_exoplanets" title="List of transiting exoplanets">list</a></li></ul></li> <li><a href="/wiki/Transit-timing_variation" title="Transit-timing variation">Transit-timing variation</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:right;"><a class="mw-selflink selflink">Habitability</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astrobiology" title="Astrobiology">Astrobiology</a></li> <li><a href="/wiki/Astrooceanography" class="mw-redirect" title="Astrooceanography">Astrooceanography</a></li> <li><a href="/wiki/Circumstellar_habitable_zone" class="mw-redirect" title="Circumstellar habitable zone">Circumstellar habitable zone</a></li> <li><a href="/wiki/Earth_analog" title="Earth analog">Earth analog</a></li> <li><a href="/wiki/Extraterrestrial_liquid_water" title="Extraterrestrial liquid water">Extraterrestrial liquid water</a></li> <li><a href="/wiki/Galactic_habitable_zone" title="Galactic habitable zone">Galactic habitable zone</a></li> <li><a href="/wiki/Habitability_of_binary_star_systems" title="Habitability of binary star systems">Habitability of binary star systems</a></li> <li><a href="/wiki/Habitability_of_F-type_main-sequence_star_systems" title="Habitability of F-type main-sequence star systems">Habitability of F-type main-sequence star systems</a></li> <li><a href="/wiki/Habitability_of_K-type_main-sequence_star_systems" title="Habitability of K-type main-sequence star systems">Habitability of K-type main-sequence star systems</a></li> <li><a href="/wiki/Habitability_of_natural_satellites" title="Habitability of natural satellites">Habitability of natural satellites</a></li> <li><a href="/wiki/Habitability_of_neutron_star_systems" title="Habitability of neutron star systems">Habitability of neutron star systems</a></li> <li><a href="/wiki/Habitability_of_red_dwarf_systems" title="Habitability of red dwarf systems">Habitability of red dwarf systems</a></li> <li><a href="/wiki/Habitability_of_yellow_dwarf_systems" title="Habitability of yellow dwarf systems">Habitability of yellow dwarf systems</a></li> <li><a href="/wiki/Habitable_zone_for_complex_life" title="Habitable zone for complex life">Habitable zone for complex life</a></li> <li><a href="/wiki/List_of_potentially_habitable_exoplanets" title="List of potentially habitable exoplanets">List of potentially habitable exoplanets</a></li> <li><a href="/wiki/Tholin" title="Tholin">Tholin</a></li> <li><a href="/wiki/Superhabitable_planet" class="mw-redirect" title="Superhabitable planet">Superhabitable planet</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:right;">Catalogues</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Catalog_of_Nearby_Habitable_Systems" title="Catalog of Nearby Habitable Systems">Nearby Habitable Systems</a></li> <li><a href="/wiki/Exoplanet_Data_Explorer" title="Exoplanet Data Explorer">Exoplanet Data Explorer</a></li> <li><a href="/wiki/Extrasolar_Planets_Encyclopaedia" title="Extrasolar Planets Encyclopaedia">Extrasolar Planets Encyclopaedia</a></li> <li><a href="/wiki/NASA_Exoplanet_Archive" title="NASA Exoplanet Archive">NASA Exoplanet Archive</a></li> <li><a href="/wiki/NASA_Star_and_Exoplanet_Database" title="NASA Star and Exoplanet Database">NASA Star and Exoplanet Database</a></li> <li><a href="/wiki/Open_Exoplanet_Catalogue" title="Open Exoplanet Catalogue">Open Exoplanet Catalogue</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:right;"><a href="/wiki/Lists_of_planets" title="Lists of planets">Lists</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>Exoplanetary systems <ul><li><a href="/wiki/List_of_exoplanetary_host_stars" class="mw-redirect" title="List of exoplanetary host stars">Host stars</a></li> <li><a href="/wiki/List_of_multiplanetary_systems" title="List of multiplanetary systems">Multiplanetary systems</a></li> <li><a href="/wiki/List_of_stars_with_proplyds" title="List of stars with proplyds">Stars with proto-planetary discs</a></li></ul></li></ul> <ul><li><a href="/wiki/Lists_of_exoplanets" class="mw-redirect" title="Lists of exoplanets">Exoplanets</a> <ul><li><a href="/wiki/Discoveries_of_exoplanets" title="Discoveries of exoplanets">Discoveries</a></li> <li><a href="/wiki/List_of_exoplanet_extremes" title="List of exoplanet extremes">Extremes</a></li> <li><a href="/wiki/List_of_exoplanet_firsts" title="List of exoplanet firsts">Firsts</a></li> <li><a href="/wiki/List_of_nearest_exoplanets" title="List of nearest exoplanets">Nearest</a></li> <li><a href="/wiki/List_of_largest_exoplanets" title="List of largest exoplanets">Largest</a></li> <li><a href="/wiki/List_of_most_massive_exoplanets" class="mw-redirect" title="List of most massive exoplanets">Heaviest</a></li> <li><a href="/wiki/List_of_nearest_terrestrial_exoplanet_candidates" title="List of nearest terrestrial exoplanet candidates">Terrestrial candidates</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_by_the_Kepler_space_telescope" title="List of exoplanets discovered by the Kepler space telescope">Kepler</a> <ul><li><a href="/wiki/List_of_exoplanets_discovered_by_the_Kepler_space_telescope:_1%E2%80%93500" title="List of exoplanets discovered by the Kepler space telescope: 1–500">1–500</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_by_the_Kepler_space_telescope:_501%E2%80%931000" title="List of exoplanets discovered by the Kepler space telescope: 501–1000">501–1000</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_by_the_Kepler_space_telescope:_1001%E2%80%931500" title="List of exoplanets discovered by the Kepler space telescope: 1001–1500">1001–1500</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_by_the_Kepler_space_telescope:_1501%E2%80%932000" title="List of exoplanets discovered by the Kepler space telescope: 1501–2000">1501–2000</a></li></ul></li> <li><a href="/wiki/List_of_exoplanets_observed_during_Kepler%27s_K2_mission" title="List of exoplanets observed during Kepler's K2 mission">K2</a></li> <li><a href="/wiki/List_of_potentially_habitable_exoplanets" title="List of potentially habitable exoplanets">Potentially habitable</a></li> <li><a href="/wiki/List_of_proper_names_of_exoplanets" title="List of proper names of exoplanets">Proper names</a></li></ul></li></ul> <ul><li>Discovered exoplanets by year <ul><li><a href="/wiki/List_of_exoplanets_discovered_before_2000" title="List of exoplanets discovered before 2000">before 2000</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_between_2000%E2%80%932009" title="List of exoplanets discovered between 2000–2009">2000–2009</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2010" title="List of exoplanets discovered in 2010">2010</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2011" title="List of exoplanets discovered in 2011">2011</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2012" title="List of exoplanets discovered in 2012">2012</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2013" title="List of exoplanets discovered in 2013">2013</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2014" title="List of exoplanets discovered in 2014">2014</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2015" title="List of exoplanets discovered in 2015">2015</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2016" title="List of exoplanets discovered in 2016">2016</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2017" title="List of exoplanets discovered in 2017">2017</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2018" title="List of exoplanets discovered in 2018">2018</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2019" title="List of exoplanets discovered in 2019">2019</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2020" title="List of exoplanets discovered in 2020">2020</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2021" title="List of exoplanets discovered in 2021">2021</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2022" title="List of exoplanets discovered in 2022">2022</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2023" title="List of exoplanets discovered in 2023">2023</a></li> <li><a href="/wiki/List_of_exoplanets_discovered_in_2024" title="List of exoplanets discovered in 2024">2024</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:right;">Other</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Carl_Sagan_Institute" title="Carl Sagan Institute">Carl Sagan Institute</a></li> <li><a href="/wiki/Exoplanet_naming_convention" title="Exoplanet naming convention">Exoplanet naming convention</a></li> <li><a href="/wiki/Phase_curve_(astronomy)#Exoplanets" title="Phase curve (astronomy)">Exoplanet phase curves</a></li> <li><a href="/wiki/Exoplanetary_Circumstellar_Environments_and_Disk_Explorer" title="Exoplanetary Circumstellar Environments and Disk Explorer">Exoplanetary Circumstellar Environments and Disk Explorer</a></li> <li><a href="/wiki/Extragalactic_planet" title="Extragalactic planet">Extragalactic planet</a></li> <li><a href="/wiki/Extrasolar_planets_in_fiction" title="Extrasolar planets in fiction">Extrasolar planets in fiction</a></li> <li><a href="/wiki/Geodynamics_of_terrestrial_exoplanets" title="Geodynamics of terrestrial exoplanets">Geodynamics of terrestrial exoplanets</a></li> <li><a href="/wiki/Neptunian_desert" title="Neptunian desert">Neptunian desert</a></li> <li><a href="/wiki/Nexus_for_Exoplanet_System_Science" title="Nexus for Exoplanet System Science">Nexus for Exoplanet System Science</a></li> <li><a href="/wiki/Globular_cluster#Planets" title="Globular cluster">Planets in globular clusters</a></li> <li><a href="/wiki/Small_planet_radius_gap" title="Small planet radius gap">Small planet radius gap</a></li> <li><a href="/wiki/Sudarsky%27s_gas_giant_classification" title="Sudarsky's gas giant classification">Sudarsky's gas giant classification</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="3"><div> <ul><li><a href="/wiki/Discoveries_of_exoplanets" title="Discoveries of exoplanets">Discoveries of exoplanets</a></li> <li><a href="/wiki/List_of_exoplanet_search_projects" title="List of exoplanet search projects">Search projects</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Space_colonization" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Space_colonization" title="Template:Space colonization"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Space_colonization" title="Template talk:Space colonization"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Space_colonization" title="Special:EditPage/Template:Space colonization"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Space_colonization" style="font-size:114%;margin:0 4em"><a href="/wiki/Space_colonization" title="Space colonization">Space colonization</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Core concepts</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Interplanetary_spaceflight" title="Interplanetary spaceflight">Interplanetary spaceflight</a></li> <li><a href="/wiki/Interstellar_travel" title="Interstellar travel">Interstellar travel</a></li> <li><a href="/wiki/Intergalactic_travel" title="Intergalactic travel">Intergalactic travel</a></li> <li><a class="mw-selflink selflink">Planetary habitability</a></li> <li><a href="/wiki/Space_and_survival" title="Space and survival">Space and survival</a></li> <li><a href="/wiki/Space_settlement" title="Space settlement">Space settlement</a></li> <li><a href="/wiki/Terraforming" title="Terraforming">Terraforming</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Space habitats</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Bishop_Ring_(habitat)" title="Bishop Ring (habitat)">Bishop Ring</a></li> <li><a href="/wiki/McKendree_cylinder" title="McKendree cylinder">McKendree cylinder</a></li> <li><a href="/wiki/O%27Neill_cylinder" title="O'Neill cylinder">O'Neill cylinder</a></li> <li><a href="/wiki/Stanford_torus" title="Stanford torus">Stanford torus</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Colonization targets</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Lagrange_point_colonization" title="Lagrange point colonization">Lagrange points</a></li> <li><a href="/wiki/Colonization_of_the_Solar_System" class="mw-redirect" title="Colonization of the Solar System">Solar System</a> <ul><li><a href="/wiki/Colonization_of_Mercury" class="mw-redirect" title="Colonization of Mercury">Mercury</a></li> <li><a href="/wiki/Colonization_of_Venus" title="Colonization of Venus">Venus</a></li> <li><a href="/wiki/Colonization_of_Mars" title="Colonization of Mars">Mars</a></li> <li><a href="/wiki/Colonization_of_the_asteroids" class="mw-redirect" title="Colonization of the asteroids">Asteroids</a> <ul><li><a href="/wiki/Asteroid_mining" title="Asteroid mining">mining</a></li></ul></li> <li><a href="/wiki/Colonization_of_the_Moon" title="Colonization of the Moon">Moon</a></li> <li><a href="/wiki/Colonization_of_Titan" title="Colonization of Titan">Titan</a></li> <li><a href="/wiki/Colonization_of_trans-Neptunian_objects" title="Colonization of trans-Neptunian objects">Trans-Neptunian objects</a></li></ul></li> <li><a href="/wiki/Space_settlement" title="Space settlement">Free space</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Terraforming targets</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Terraforming_of_Mars" title="Terraforming of Mars">Mars</a></li> <li><a href="/wiki/Terraforming_of_Venus" title="Terraforming of Venus">Venus</a></li> <li><a href="/w/index.php?title=Terraforming_of_Europa&action=edit&redlink=1" class="new" title="Terraforming of Europa (page does not exist)">Europa</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Organizations</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Mars_Society" title="Mars Society">Mars Society</a></li> <li><a href="/wiki/NASA" title="NASA">NASA</a></li> <li><a href="/wiki/National_Space_Society" title="National Space Society">National Space Society</a></li> <li><a href="/wiki/SpaceX" title="SpaceX">SpaceX</a></li> <li><a href="/wiki/The_Planetary_Society" title="The Planetary Society">The Planetary Society</a></li></ul> </div></td></tr></tbody></table></div> <style data-mw-deduplicate="TemplateStyles:r1130092004">.mw-parser-output .portal-bar{font-size:88%;font-weight:bold;display:flex;justify-content:center;align-items:baseline}.mw-parser-output .portal-bar-bordered{padding:0 2em;background-color:#fdfdfd;border:1px solid #a2a9b1;clear:both;margin:1em auto 0}.mw-parser-output .portal-bar-related{font-size:100%;justify-content:flex-start}.mw-parser-output .portal-bar-unbordered{padding:0 1.7em;margin-left:0}.mw-parser-output .portal-bar-header{margin:0 1em 0 0.5em;flex:0 0 auto;min-height:24px}.mw-parser-output .portal-bar-content{display:flex;flex-flow:row wrap;flex:0 1 auto;padding:0.15em 0;column-gap:1em;align-items:baseline;margin:0;list-style:none}.mw-parser-output .portal-bar-content-related{margin:0;list-style:none}.mw-parser-output .portal-bar-item{display:inline-block;margin:0.15em 0.2em;min-height:24px;line-height:24px}@media screen and (max-width:768px){.mw-parser-output .portal-bar{font-size:88%;font-weight:bold;display:flex;flex-flow:column wrap;align-items:baseline}.mw-parser-output .portal-bar-header{text-align:center;flex:0;padding-left:0.5em;margin:0 auto}.mw-parser-output .portal-bar-related{font-size:100%;align-items:flex-start}.mw-parser-output .portal-bar-content{display:flex;flex-flow:row wrap;align-items:center;flex:0;column-gap:1em;border-top:1px solid #a2a9b1;margin:0 auto;list-style:none}.mw-parser-output .portal-bar-content-related{border-top:none;margin:0;list-style:none}}.mw-parser-output .navbox+link+.portal-bar,.mw-parser-output .navbox+style+.portal-bar,.mw-parser-output .navbox+link+.portal-bar-bordered,.mw-parser-output .navbox+style+.portal-bar-bordered,.mw-parser-output .sister-bar+link+.portal-bar,.mw-parser-output .sister-bar+style+.portal-bar,.mw-parser-output .portal-bar+.navbox-styles+.navbox,.mw-parser-output .portal-bar+.navbox-styles+.sister-bar{margin-top:-1px}</style><div class="portal-bar noprint metadata noviewer portal-bar-bordered" role="navigation" aria-label="Portals"><span class="portal-bar-header"><a href="/wiki/Wikipedia:Contents/Portals" title="Wikipedia:Contents/Portals">Portals</a>:</span><ul class="portal-bar-content"><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><a href="/wiki/File:Issoria_lathonia.jpg" class="mw-file-description"><img alt="icon" src="//upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Issoria_lathonia.jpg/21px-Issoria_lathonia.jpg" decoding="async" width="21" height="15" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Issoria_lathonia.jpg/32px-Issoria_lathonia.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Issoria_lathonia.jpg/42px-Issoria_lathonia.jpg 2x" data-file-width="629" data-file-height="445" /></a></span> </span><a href="/wiki/Portal:Biology" title="Portal:Biology">Biology</a></li><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/19px-Crab_Nebula.jpg" decoding="async" width="19" height="19" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/29px-Crab_Nebula.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/38px-Crab_Nebula.jpg 2x" data-file-width="3864" data-file-height="3864" /></span></span> </span><a href="/wiki/Portal:Astronomy" title="Portal:Astronomy">Astronomy</a></li><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><a href="/wiki/File:He1523a.jpg" class="mw-file-description"><img alt="icon" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/He1523a.jpg/16px-He1523a.jpg" decoding="async" width="16" height="19" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/He1523a.jpg/25px-He1523a.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5f/He1523a.jpg/33px-He1523a.jpg 2x" data-file-width="180" data-file-height="207" /></a></span> </span><a href="/wiki/Portal:Stars" title="Portal:Stars">Stars</a></li><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/RocketSunIcon.svg/19px-RocketSunIcon.svg.png" decoding="async" width="19" height="19" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/RocketSunIcon.svg/29px-RocketSunIcon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/d6/RocketSunIcon.svg/38px-RocketSunIcon.svg.png 2x" data-file-width="128" data-file-height="128" /></span></span> </span><a href="/wiki/Portal:Spaceflight" title="Portal:Spaceflight">Spaceflight</a></li><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Earth-moon.jpg/21px-Earth-moon.jpg" decoding="async" width="21" height="17" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Earth-moon.jpg/32px-Earth-moon.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Earth-moon.jpg/42px-Earth-moon.jpg 2x" data-file-width="3000" data-file-height="2400" /></span></span> </span><a href="/wiki/Portal:Outer_space" title="Portal:Outer space">Outer space</a></li><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Solar_system.jpg/15px-Solar_system.jpg" decoding="async" width="15" height="19" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Solar_system.jpg/23px-Solar_system.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Solar_system.jpg/30px-Solar_system.jpg 2x" data-file-width="4500" data-file-height="5600" /></span></span> </span><a href="/wiki/Portal:Solar_System" title="Portal:Solar System">Solar System</a></li><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><a href="/wiki/File:Nuvola_apps_kalzium.svg" class="mw-file-description"><img alt="icon" src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8b/Nuvola_apps_kalzium.svg/19px-Nuvola_apps_kalzium.svg.png" decoding="async" width="19" height="19" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8b/Nuvola_apps_kalzium.svg/29px-Nuvola_apps_kalzium.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8b/Nuvola_apps_kalzium.svg/38px-Nuvola_apps_kalzium.svg.png 2x" data-file-width="128" data-file-height="128" /></a></span> </span><a href="/wiki/Portal:Science" title="Portal:Science">Science</a></li></ul></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox authority-control" aria-label="Navbox" style="padding:3px"><table class="nowraplinks hlist navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Help:Authority_control" title="Help:Authority control">Authority control databases</a>: National <span class="mw-valign-text-top noprint" typeof="mw:File/Frameless"><a href="https://www.wikidata.org/wiki/Q846030#identifiers" title="Edit this at Wikidata"><img alt="Edit this at Wikidata" src="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/10px-OOjs_UI_icon_edit-ltr-progressive.svg.png" decoding="async" width="10" height="10" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/15px-OOjs_UI_icon_edit-ltr-progressive.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/20px-OOjs_UI_icon_edit-ltr-progressive.svg.png 2x" data-file-width="20" data-file-height="20" /></a></span></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"><ul><li><span class="uid"><a rel="nofollow" class="external text" href="https://id.loc.gov/authorities/sh2005004576">United States</a></span></li><li><span class="uid"><a rel="nofollow" class="external text" href="http://olduli.nli.org.il/F/?func=find-b&local_base=NLX10&find_code=UID&request=987007554325205171">Israel</a></span></li></ul></div></td></tr></tbody></table></div> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-127"><span class="mw-cite-backlink"><b><a href="#cite_ref-127">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSmith2021" class="citation web cs1">Smith, Yvette (26 January 2021). <a rel="nofollow" class="external text" href="https://www.nasa.gov/image-feature/finding-a-new-earth">"Finding a New Earth"</a>. <i>NASA</i><span class="reference-accessdate">. Retrieved <span class="nowrap">13 April</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=NASA&rft.atitle=Finding+a+New+Earth&rft.date=2021-01-26&rft.aulast=Smith&rft.aufirst=Yvette&rft_id=http%3A%2F%2Fwww.nasa.gov%2Fimage-feature%2Ffinding-a-new-earth&rfr_id=info%3Asid%2Fen.wikipedia.org%3APlanetary+habitability" class="Z3988"></span></span> </li> </ol></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Planetary_habitability&oldid=1259831068">https://en.wikipedia.org/w/index.php?title=Planetary_habitability&oldid=1259831068</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Planetary_habitability" title="Category:Planetary habitability">Planetary habitability</a></li><li><a href="/wiki/Category:Astrobiology" title="Category:Astrobiology">Astrobiology</a></li><li><a href="/wiki/Category:Space_colonization" title="Category:Space colonization">Space colonization</a></li><li><a href="/wiki/Category:Exoplanetology" title="Category:Exoplanetology">Exoplanetology</a></li><li><a href="/wiki/Category:Prebiotic_chemistry" title="Category:Prebiotic chemistry">Prebiotic chemistry</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:CS1_maint:_multiple_names:_authors_list" title="Category:CS1 maint: multiple names: authors list">CS1 maint: multiple names: authors list</a></li><li><a href="/wiki/Category:CS1_maint:_unfit_URL" title="Category:CS1 maint: unfit URL">CS1 maint: unfit URL</a></li><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_is_different_from_Wikidata" title="Category:Short description is different from Wikidata">Short description is different from Wikidata</a></li><li><a href="/wiki/Category:Use_dmy_dates_from_May_2022" title="Category:Use dmy dates from May 2022">Use dmy dates from May 2022</a></li><li><a href="/wiki/Category:All_articles_needing_additional_references" title="Category:All articles needing additional references">All articles needing additional references</a></li><li><a href="/wiki/Category:Articles_needing_additional_references_from_December_2020" title="Category:Articles needing additional references from December 2020">Articles needing additional references from December 2020</a></li><li><a href="/wiki/Category:All_articles_with_specifically_marked_weasel-worded_phrases" title="Category:All articles with specifically marked weasel-worded phrases">All articles with specifically marked weasel-worded phrases</a></li><li><a href="/wiki/Category:Articles_with_specifically_marked_weasel-worded_phrases_from_April_2024" title="Category:Articles with specifically marked weasel-worded phrases from April 2024">Articles with specifically marked weasel-worded phrases from April 2024</a></li><li><a href="/wiki/Category:Pages_displaying_short_descriptions_of_redirect_targets_via_Module:Annotated_link" title="Category:Pages displaying short descriptions of redirect targets via Module:Annotated link">Pages displaying short descriptions of redirect targets via Module:Annotated link</a></li><li><a href="/wiki/Category:Articles_with_hAudio_microformats" title="Category:Articles with hAudio microformats">Articles with hAudio microformats</a></li><li><a href="/wiki/Category:Spoken_articles" title="Category:Spoken articles">Spoken articles</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 27 November 2024, at 08:34<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. By using this site, you agree to the <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Terms_of_Use" class="extiw" title="foundation:Special:MyLanguage/Policy:Terms of Use">Terms of Use</a> and <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy" class="extiw" title="foundation:Special:MyLanguage/Policy:Privacy policy">Privacy Policy</a>. Wikipedia® is a registered trademark of the <a rel="nofollow" class="external text" href="https://wikimediafoundation.org/">Wikimedia Foundation, Inc.</a>, a non-profit organization.</li> </ul> <ul id="footer-places"> <li id="footer-places-privacy"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy">Privacy policy</a></li> <li id="footer-places-about"><a href="/wiki/Wikipedia:About">About Wikipedia</a></li> <li id="footer-places-disclaimers"><a href="/wiki/Wikipedia:General_disclaimer">Disclaimers</a></li> <li id="footer-places-contact"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us">Contact Wikipedia</a></li> <li id="footer-places-wm-codeofconduct"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Universal_Code_of_Conduct">Code of Conduct</a></li> <li id="footer-places-developers"><a href="https://developer.wikimedia.org">Developers</a></li> <li id="footer-places-statslink"><a href="https://stats.wikimedia.org/#/en.wikipedia.org">Statistics</a></li> <li id="footer-places-cookiestatement"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Cookie_statement">Cookie statement</a></li> <li id="footer-places-mobileview"><a href="//en.m.wikipedia.org/w/index.php?title=Planetary_habitability&mobileaction=toggle_view_mobile" class="noprint stopMobileRedirectToggle">Mobile view</a></li> </ul> <ul id="footer-icons" class="noprint"> <li id="footer-copyrightico"><a href="https://wikimediafoundation.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/static/images/footer/wikimedia-button.svg" width="84" height="29" alt="Wikimedia Foundation" loading="lazy"></a></li> <li id="footer-poweredbyico"><a href="https://www.mediawiki.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/w/resources/assets/poweredby_mediawiki.svg" alt="Powered by MediaWiki" width="88" height="31" loading="lazy"></a></li> </ul> </footer> </div> </div> </div> <div class="vector-settings" id="p-dock-bottom"> <ul></ul> </div><script>(RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgHostname":"mw-web.codfw.main-57488d5c7d-zq89r","wgBackendResponseTime":192,"wgPageParseReport":{"limitreport":{"cputime":"1.544","walltime":"1.857","ppvisitednodes":{"value":11955,"limit":1000000},"postexpandincludesize":{"value":383686,"limit":2097152},"templateargumentsize":{"value":5197,"limit":2097152},"expansiondepth":{"value":16,"limit":100},"expensivefunctioncount":{"value":23,"limit":500},"unstrip-depth":{"value":1,"limit":20},"unstrip-size":{"value":509514,"limit":5000000},"entityaccesscount":{"value":1,"limit":400},"timingprofile":["100.00% 1610.347 1 -total"," 42.61% 686.181 2 Template:Reflist"," 17.48% 281.456 54 Template:Cite_web"," 13.90% 223.780 40 Template:Cite_journal"," 12.88% 207.428 15 Template:Annotated_link"," 6.80% 109.550 5 Template:Navbox"," 5.79% 93.270 1 Template:Short_description"," 5.79% 93.207 1 Template:Astrobiology"," 3.71% 59.775 2 Template:Pagetype"," 2.94% 47.277 1 Template:Additional_citation_needed"]},"scribunto":{"limitreport-timeusage":{"value":"0.918","limit":"10.000"},"limitreport-memusage":{"value":18491011,"limit":52428800}},"cachereport":{"origin":"mw-web.codfw.main-57488d5c7d-cnhg5","timestamp":"20241128030706","ttl":2592000,"transientcontent":false}}});});</script> <script type="application/ld+json">{"@context":"https:\/\/schema.org","@type":"Article","name":"Planetary habitability","url":"https:\/\/en.wikipedia.org\/wiki\/Planetary_habitability","sameAs":"http:\/\/www.wikidata.org\/entity\/Q846030","mainEntity":"http:\/\/www.wikidata.org\/entity\/Q846030","author":{"@type":"Organization","name":"Contributors to Wikimedia projects"},"publisher":{"@type":"Organization","name":"Wikimedia Foundation, Inc.","logo":{"@type":"ImageObject","url":"https:\/\/www.wikimedia.org\/static\/images\/wmf-hor-googpub.png"}},"datePublished":"2005-09-01T18:50:13Z","dateModified":"2024-11-27T08:34:08Z","image":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/c\/cb\/The_Blue_Marble_%28remastered%29.jpg","headline":"degree to which a planet is suitable for life, or study of planets which may be so suited"}</script> </body> </html>