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href="https://bn.wikipedia.org/wiki/%E0%A6%95%E0%A7%8D%E0%A6%B7%E0%A7%81%E0%A6%A6%E0%A7%8D%E0%A6%B0_%E0%A6%89%E0%A6%B2%E0%A7%8D%E0%A6%95%E0%A6%BE%E0%A6%AA%E0%A6%BF%E0%A6%A3%E0%A7%8D%E0%A6%A1" title="ক্ষুদ্র উল্কাপিণ্ড – Bangla" lang="bn" hreflang="bn" data-title="ক্ষুদ্র উল্কাপিণ্ড" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Micrometeoroide" title="Micrometeoroide – Spanish" lang="es" hreflang="es" data-title="Micrometeoroide" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%B1%DB%8C%D8%B2%D8%B4%D9%87%D8%A7%D8%A8%E2%80%8C%D9%88%D8%A7%D8%B1%D9%87" title="ریزشهاب‌واره – Persian" lang="fa" hreflang="fa" data-title="ریزشهاب‌واره" 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/Microm%C3%A9t%C3%A9oro%C3%AFde" title="Micrométéoroïde – French" lang="fr" hreflang="fr" data-title="Micrométéoroïde" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EC%9C%A0%EC%84%B1%EC%A7%84" title="유성진 – Korean" lang="ko" hreflang="ko" data-title="유성진" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Mikrometeorid" title="Mikrometeorid – Croatian" lang="hr" hreflang="hr" data-title="Mikrometeorid" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Mikrometeoroid" title="Mikrometeoroid – Indonesian" lang="id" hreflang="id" data-title="Mikrometeoroid" 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-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Mikrometeoroid" title="Mikrometeoroid – Malay" lang="ms" hreflang="ms" data-title="Mikrometeoroid" 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-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E5%BE%AE%E5%B0%8F%E9%9A%95%E7%9F%B3" title="微小隕石 – Japanese" lang="ja" hreflang="ja" data-title="微小隕石" 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/Mikrometeoroide" title="Mikrometeoroide – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Mikrometeoroide" 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-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Mikrometeoroid" title="Mikrometeoroid – Slovak" lang="sk" hreflang="sk" data-title="Mikrometeoroid" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Mikrometeoroid" title="Mikrometeoroid – Slovenian" lang="sl" hreflang="sl" data-title="Mikrometeoroid" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Mikrometeoroidi" title="Mikrometeoroidi – Finnish" lang="fi" hreflang="fi" data-title="Mikrometeoroidi" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Mikrometeor" title="Mikrometeor – Turkish" lang="tr" hreflang="tr" data-title="Mikrometeor" 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%9C%D1%96%D0%BA%D1%80%D0%BE%D0%BC%D0%B5%D1%82%D0%B5%D0%BE%D1%80%D0%BE%D1%97%D0%B4" title="Мікрометеороїд – Ukrainian" lang="uk" hreflang="uk" data-title="Мікрометеороїд" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/%E5%BE%AE%E6%B5%81%E6%98%9F%E4%BD%93" title="微流星体 – Wu" lang="wuu" hreflang="wuu" data-title="微流星体" data-language-autonym="吴语" data-language-local-name="Wu" class="interlanguage-link-target"><span>吴语</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E5%BE%AE%E6%B5%81%E6%98%9F%E9%AB%94" title="微流星體 – Chinese" lang="zh" hreflang="zh" data-title="微流星體" 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 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href="/wiki/File:Micrometeorite.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Micrometeorite.jpg/250px-Micrometeorite.jpg" decoding="async" width="250" height="148" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/f/fc/Micrometeorite.jpg 1.5x" data-file-width="300" data-file-height="178" /></a><figcaption>Micrometeorite, collected from the Antarctic snow, was a micrometeoroid before it entered the Earth's atmosphere</figcaption></figure> <p>A <b>micrometeoroid</b> is a tiny <a href="/wiki/Meteoroid" title="Meteoroid">meteoroid</a>: a small particle of rock in space, usually weighing less than a <a href="/wiki/Gram" title="Gram">gram</a>. A <a href="/wiki/Micrometeorite" title="Micrometeorite">micrometeorite</a> is such a particle that survives passage through <a href="/wiki/Atmosphere_of_Earth" title="Atmosphere of Earth">Earth's atmosphere</a> and reaches Earth's surface. </p><p>The term "micrometeoroid" was officially deprecated by the <a href="/wiki/International_Astronomical_Union" title="International Astronomical Union">IAU</a> in 2017, as redundant to meteoroid.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Origins_and_orbits">Origins and orbits</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Micrometeoroid&action=edit&section=1" title="Edit section: Origins and orbits"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></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">See also: <a href="/wiki/Cosmic_dust" title="Cosmic dust">Cosmic dust</a></div> <p>Micrometeoroids are very small pieces of rock or metal broken off from larger chunks of rock and debris often dating back to the birth of the <a href="/wiki/Solar_System" title="Solar System">Solar System</a>. Micrometeoroids are extremely common in space. Tiny particles are a major contributor to <a href="/wiki/Space_weathering" title="Space weathering">space weathering</a> processes. When they hit the surface of the <a href="/wiki/Moon" title="Moon">Moon</a>, or any airless body (<a href="/wiki/Mercury_(planet)" title="Mercury (planet)">Mercury</a>, the <a href="/wiki/Asteroid" title="Asteroid">asteroids</a>, etc.), the resulting melting and vaporization causes darkening and other optical changes in the <a href="/wiki/Regolith" title="Regolith">regolith</a>. </p><p>Micrometeoroids have less stable <a href="/wiki/Orbit" title="Orbit">orbits</a> than meteoroids, due to their greater <a href="/wiki/Surface_area" title="Surface area">surface area</a> to <a href="/wiki/Mass" title="Mass">mass</a> ratio. Micrometeoroids that fall to Earth can provide information on millimeter scale heating events in the <a href="/wiki/Solar_nebula" class="mw-redirect" title="Solar nebula">solar nebula</a>. <a href="/wiki/Meteorites" class="mw-redirect" title="Meteorites">Meteorites</a> and <a href="/wiki/Micrometeorites" class="mw-redirect" title="Micrometeorites">micrometeorites</a> (as they are known upon arrival at the Earth's surface) can only be collected in areas where there is no terrestrial <a href="/wiki/Sedimentation" title="Sedimentation">sedimentation</a>, typically polar regions. Ice is collected and then melted and filtered so the micrometeorites can be extracted under a microscope. </p><p>Sufficiently small micrometeoroids avoid significant heating on entry into <a href="/wiki/Earth" title="Earth">Earth</a>'s atmosphere.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Collection of such particles by high-flying aircraft began in the 1970s,<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> since which time these samples of stratosphere-collected <a href="/wiki/Interplanetary_dust_cloud#Collecting_interplanetary_dust_on_earth" title="Interplanetary dust cloud">interplanetary dust</a> (called <i>Brownlee particles</i> before their extraterrestrial origin was confirmed) have become an important component of the <a href="/wiki/Extraterrestrial_materials" title="Extraterrestrial materials">extraterrestrial materials</a> available for study in laboratories on Earth. </p> <div class="mw-heading mw-heading2"><h2 id="Historical_studies">Historical studies</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Micrometeoroid&action=edit&section=2" title="Edit section: Historical studies"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In 1946 during the <a href="/wiki/Draconids" title="Draconids">Giacobinid</a> <a href="/wiki/Meteor_shower" title="Meteor shower">meteor shower</a>, <a href="/wiki/Helmut_Landsberg" title="Helmut Landsberg">Helmut Landsberg</a> collected several small magnetic particles that were apparently associated with the shower.<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> <a href="/wiki/Fred_Whipple" class="mw-redirect" title="Fred Whipple">Fred Whipple</a> was intrigued by this and wrote a paper that demonstrated that particles of this size were too small to maintain their velocity when they encountered the <a href="/wiki/Upper_atmosphere" title="Upper atmosphere">upper atmosphere</a>. Instead, they quickly decelerated and then fell to Earth unmelted. In order to classify these sorts of objects, he coined the term "<a href="/wiki/Micrometeorite" title="Micrometeorite">micro-meteorite</a>".<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Velocities">Velocities</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Micrometeoroid&action=edit&section=3" title="Edit section: Velocities"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Whipple, in collaboration with <a href="/wiki/Fletcher_Watson" title="Fletcher Watson">Fletcher Watson</a> of the <a href="/wiki/Harvard_Observatory" class="mw-redirect" title="Harvard Observatory">Harvard Observatory</a>, led an effort to build an observatory to directly measure the velocity of the meteors that could be seen. At the time the source of the micro-meteorites was not known. Direct measurements at the new observatory were used to locate the source of the meteors, demonstrating that the bulk of material was left over from <a href="/wiki/Comet" title="Comet">comet</a> tails, and that none of it could be shown to have an extra-solar origin.<sup id="cite_ref-whipple1951_6-0" class="reference"><a href="#cite_note-whipple1951-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Today it is understood that meteoroids of all sorts are leftover material from the formation of the Solar System, consisting of particles from the <a href="/wiki/Interplanetary_dust_cloud" title="Interplanetary dust cloud">interplanetary dust cloud</a> or other objects made up from this material, like comets.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Flux">Flux</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Micrometeoroid&action=edit&section=4" title="Edit section: Flux"><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:Lunar_sample_61195_S72-37972.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/29/Lunar_sample_61195_S72-37972.jpg/220px-Lunar_sample_61195_S72-37972.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/29/Lunar_sample_61195_S72-37972.jpg/330px-Lunar_sample_61195_S72-37972.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/29/Lunar_sample_61195_S72-37972.jpg/440px-Lunar_sample_61195_S72-37972.jpg 2x" data-file-width="2096" data-file-height="1572" /></a><figcaption>Lunar sample 61195 from <a href="/wiki/Apollo_16" title="Apollo 16">Apollo 16</a> textured with "zap pits" from micrometeorite impacts</figcaption></figure> <p>The early studies were based exclusively on optical measurements. In 1957, <a href="/wiki/Hans_Pettersson" title="Hans Pettersson">Hans Pettersson</a> conducted one of the first direct measurements of the fall of space dust on Earth, estimating it to be 14,300,000 tons per year.<sup id="cite_ref-pettersson1960_8-0" class="reference"><a href="#cite_note-pettersson1960-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> This suggested that the meteoroid flux in space was much higher than the number based on telescope observations. Such a high flux presented a very serious risk to the high-orbiting <a href="/wiki/Project_Apollo" class="mw-redirect" title="Project Apollo">Apollo</a> capsules and for missions to the Moon. To determine whether the direct measurement was accurate, a number of additional studies followed, including the <a href="/wiki/Pegasus_(satellite)" title="Pegasus (satellite)">Pegasus satellite program</a>, <a href="/wiki/Lunar_Orbiter_1" title="Lunar Orbiter 1">Lunar Orbiter 1</a>, <a href="/wiki/Luna_3" title="Luna 3">Luna 3</a>, <a href="/wiki/Mars_1" title="Mars 1">Mars 1</a> and <a href="/wiki/Pioneer_5" title="Pioneer 5">Pioneer 5</a>. These showed that the rate of meteors passing into the atmosphere, or flux, was in line with the optical measurements, at around 10,000 to 20,000 tons per year.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> The <a href="/wiki/Surveyor_Program" class="mw-redirect" title="Surveyor Program">Surveyor Program</a> determined that the surface of the Moon is relatively rocky.<sup id="cite_ref-:1_10-0" class="reference"><a href="#cite_note-:1-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> Most lunar samples returned during the <a href="/wiki/Apollo_Program" class="mw-redirect" title="Apollo Program">Apollo Program</a> have micrometeorite impacts marks, typically called "zap pits", on their upper surfaces.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Effect_on_spacecraft_operations">Effect on spacecraft operations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Micrometeoroid&action=edit&section=5" title="Edit section: Effect on spacecraft operations"><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/Space_debris" title="Space debris">Space debris</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:SMM_panel_hole.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e1/SMM_panel_hole.jpg/220px-SMM_panel_hole.jpg" decoding="async" width="220" height="169" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e1/SMM_panel_hole.jpg/330px-SMM_panel_hole.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e1/SMM_panel_hole.jpg/440px-SMM_panel_hole.jpg 2x" data-file-width="2835" data-file-height="2175" /></a><figcaption>Electron micrograph image of an orbital debris hole made in the panel of the <a href="/wiki/Solar_Maximum_Mission" title="Solar Maximum Mission">Solar Max</a> satellite</figcaption></figure> <p>Micrometeoroids pose a significant threat to <a href="/wiki/Space_exploration" title="Space exploration">space exploration</a>. The average velocity of micrometeoroids relative to a <a href="/wiki/Spacecraft" title="Spacecraft">spacecraft</a> in orbit is 10 kilometers per second (22,500 mph). Resistance to micrometeoroid impact is a significant design challenge for spacecraft and <a href="/wiki/Space_suit" title="Space suit">space suit</a> designers (<i>See <a href="/wiki/Thermal_Micrometeoroid_Garment" title="Thermal Micrometeoroid Garment">Thermal Micrometeoroid Garment</a></i>). While the tiny sizes of most micrometeoroids limits the damage incurred, the high velocity impacts will constantly degrade the outer casing of spacecraft in a manner analogous to <a href="/wiki/Sandblasting" title="Sandblasting">sandblasting</a>. Long term exposure can threaten the functionality of spacecraft systems.<sup id="cite_ref-:0_12-0" class="reference"><a href="#cite_note-:0-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p><p>Impacts by small objects with extremely high velocity (10 kilometers per second) are a current area of research in <a href="/wiki/Terminal_ballistics" title="Terminal ballistics">terminal ballistics</a> (although accelerating objects up to such velocities is difficult; current techniques include <a href="/wiki/Linear_motor" title="Linear motor">linear motors</a> and <a href="/wiki/Shaped_charge" title="Shaped charge">shaped charges</a>). The risk is especially high for objects in space for long periods of time, such as <a href="/wiki/Satellite" title="Satellite">satellites</a>.<sup id="cite_ref-:0_12-1" class="reference"><a href="#cite_note-:0-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> They also pose major engineering challenges in theoretical low-cost lift systems such as <a href="/wiki/Momentum_exchange_tether#Rotovator" title="Momentum exchange tether">rotovators</a>, <a href="/wiki/Space_elevator" title="Space elevator">space elevators</a>, and orbital airships.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Spacecraft_micrometeoroid_shielding">Spacecraft micrometeoroid shielding</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Micrometeoroid&action=edit&section=6" title="Edit section: Spacecraft micrometeoroid shielding"><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:Hypervelocity_Impact_Demonstration.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Hypervelocity_Impact_Demonstration.jpg/220px-Hypervelocity_Impact_Demonstration.jpg" decoding="async" width="220" height="169" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Hypervelocity_Impact_Demonstration.jpg/330px-Hypervelocity_Impact_Demonstration.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/df/Hypervelocity_Impact_Demonstration.jpg/440px-Hypervelocity_Impact_Demonstration.jpg 2x" data-file-width="1474" data-file-height="1134" /></a><figcaption>The "energy flash" of a <a href="/wiki/Hypervelocity" title="Hypervelocity">hypervelocity</a> impact during a simulation of what happens when a piece of orbital debris hits a spacecraft in orbit</figcaption></figure> <p>Whipple's work pre-dated the <a href="/wiki/Space_Race" title="Space Race">Space Race</a> and it proved useful when space exploration started only a few years later. His studies had demonstrated that the chance of being hit by a meteoroid large enough to destroy a spacecraft was extremely remote. However, a spacecraft would be almost constantly struck by micrometeorites, about the size of dust grains.<sup id="cite_ref-whipple1951_6-1" class="reference"><a href="#cite_note-whipple1951-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>Whipple had already developed a solution to this problem in 1946. Originally known as a "meteor bumper" and now termed the <a href="/wiki/Whipple_shield" title="Whipple shield">Whipple shield</a>, this consists of a thin foil film held a short distance away from the spacecraft's body. When a micrometeoroid strikes the foil, it vaporizes into a plasma that quickly spreads. By the time this plasma crosses the gap between the shield and the spacecraft, it is so diffused that it is unable to penetrate the structural material below.<sup id="cite_ref-Marsden_15-0" class="reference"><a href="#cite_note-Marsden-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> The shield allows a spacecraft body to be built to just the thickness needed for structural integrity, while the foil adds little additional weight. Such a spacecraft is lighter than one with panels designed to stop the meteoroids directly. </p><p>For spacecraft that spend the majority of their time in orbit, some variety of the Whipple shield has been almost universal for decades.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> Later research showed that <a href="/wiki/Ceramic_engineering" title="Ceramic engineering">ceramic fibre</a> woven shields offer better protection to hypervelocity (~7 km/s) particles than <a href="/wiki/Aluminium" title="Aluminium">aluminium</a> shields of equal weight.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> Another modern design uses <a href="/wiki/Transhab#Multi-Layer_Inflatable_Shell" class="mw-redirect" title="Transhab">multi-layer flexible fabric</a>, as in <a href="/wiki/NASA" title="NASA">NASA</a>'s design for its never-flown <a href="/wiki/TransHab" title="TransHab">TransHab</a> expandable space habitation module,<sup id="cite_ref-nasa20030627_19-0" class="reference"><a href="#cite_note-nasa20030627-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> and the <a href="/wiki/Bigelow_Expandable_Activity_Module" title="Bigelow Expandable Activity Module">Bigelow Expandable Activity Module</a>, which was launched in April 2016 and attached to the <a href="/wiki/International_Space_Station" title="International Space Station">ISS</a> for two years of orbital testing.<sup id="cite_ref-sdc20141006_20-0" class="reference"><a href="#cite_note-sdc20141006-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading2"><h2 id="Footnotes">Footnotes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Micrometeoroid&action=edit&section=7" title="Edit section: Footnotes"><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"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></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="CITEREFIAU_Commission_F12017" class="citation web cs1">IAU Commission F1 (April 30, 2017). <a rel="nofollow" class="external text" href="https://www.iau.org/static/science/scientific_bodies/commissions/f1/meteordefinitions_approved.pdf">"Definition of terms in meteor astronomy"</a> <span class="cs1-format">(PDF)</span>. <i>International Astronomical Union</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 Jul</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=International+Astronomical+Union&rft.atitle=Definition+of+terms+in+meteor+astronomy&rft.date=2017-04-30&rft.au=IAU+Commission+F1&rft_id=https%3A%2F%2Fwww.iau.org%2Fstatic%2Fscience%2Fscientific_bodies%2Fcommissions%2Ff1%2Fmeteordefinitions_approved.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMicrometeoroid" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text">P. Fraundorf (1980) The distribution of temperature maxima for micrometeorites decelerated in the Earth's atmosphere without melting <i>Geophys. Res. Lett.</i> <b>10</b>:765-768.</span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text">D. E. Brownlee, D. A. Tomandl and E. Olszewski (1977) Interplanetary dust: A new source of extraterrestrial material for laboratory studies, <i>Proc. Lunar Sci. Conf. <b>8th</b>:149-160.</i></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">Fred Whipple, <a rel="nofollow" class="external text" href="http://www.pnas.org/content/36/12/687.full.pdf?ck=nck">"The Theory of Micro-Meteorites, Part I: In an Isothermal Atmosphere"</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150924163355/http://www.pnas.org/content/36/12/687.full.pdf?ck=nck">Archived</a> 24 September 2015 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, <i>Proceedings of the National Academy of Sciences</i>, Volume 36 Number 12 (15 December 1950), pp. 667 – 695.</span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text">Fred Whipple, <a rel="nofollow" class="external text" href="http://adsabs.harvard.edu/full/1949PA.....57..517W">"The Theory of Micrometeorites."</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20151017195956/http://adsabs.harvard.edu/full/1949PA.....57..517W">Archived</a> 17 October 2015 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, <i>Popular Astronomy</i>, Volume 57, 1949, p. 517.</span> </li> <li id="cite_note-whipple1951-6"><span class="mw-cite-backlink">^ <a href="#cite_ref-whipple1951_6-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-whipple1951_6-1"><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="CITEREFWhipple1951" class="citation journal cs1">Whipple, Fred (1951). <a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F145416">"A Comet Model. II. Physical Relations for Comets and Meteors"</a>. <i>Astrophysical Journal</i>. <b>113</b>: 464–474. <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/1951ApJ...113..464W">1951ApJ...113..464W</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/10.1086%2F145416">10.1086/145416</a></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astrophysical+Journal&rft.atitle=A+Comet+Model.+II.+Physical+Relations+for+Comets+and+Meteors&rft.volume=113&rft.pages=464-474&rft.date=1951&rft_id=info%3Adoi%2F10.1086%2F145416&rft_id=info%3Abibcode%2F1951ApJ...113..464W&rft.aulast=Whipple&rft.aufirst=Fred&rft_id=https%3A%2F%2Fdoi.org%2F10.1086%252F145416&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMicrometeoroid" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBrownleeTomandlOlszewski1977" class="citation journal cs1">Brownlee, D. E.; Tomandl, D. A.; Olszewski, E. (1977). "1977LPI.....8..145B Interplanetary dust: A new source of extraterrestrial material for laboratory studies". <i>Proceedings of the 8th Lunar Scientific Conference</i>. <b>1977</b>: 149–160. <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/1977LPI.....8..145B">1977LPI.....8..145B</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+8th+Lunar+Scientific+Conference&rft.atitle=1977LPI.....8..145B+Interplanetary+dust%3A+A+new+source+of+extraterrestrial+material+for+laboratory+studies&rft.volume=1977&rft.pages=149-160&rft.date=1977&rft_id=info%3Abibcode%2F1977LPI.....8..145B&rft.aulast=Brownlee&rft.aufirst=D.+E.&rft.au=Tomandl%2C+D.+A.&rft.au=Olszewski%2C+E.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMicrometeoroid" class="Z3988"></span></span> </li> <li id="cite_note-pettersson1960-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-pettersson1960_8-0">^</a></b></span> <span class="reference-text">Hans Pettersson, "Cosmic Spherules and Meteoritic Dust." <i>Scientific American</i>, Volume 202 Issue 2 (February 1960), pp. 123–132.</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">Andrew Snelling and David Rush, <a rel="nofollow" class="external text" href="http://static.icr.org/i/pdf/technical/Moon-Dust-and-the-Age-of-the-Solar-System.pdf">"Moon Dust and the Age of the Solar System"</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110512174406/http://static.icr.org/i/pdf/technical/Moon-Dust-and-the-Age-of-the-Solar-System.pdf">Archived</a> 12 May 2011 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> <i>Creation Ex-Nihilo Technical Journal</i>, Volume 7 Number 1 (1993), p. 2–42.</span> </li> <li id="cite_note-:1-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-:1_10-0">^</a></b></span> <span class="reference-text">Snelling, Andrew and David Rush. <a rel="nofollow" class="external text" href="http://static.icr.org/i/pdf/technical/Moon-Dust-and-the-Age-of-the-Solar-System.pdf">"Moon Dust and the Age of the Solar System."</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20120309094615/http://static.icr.org/i/pdf/technical/Moon-Dust-and-the-Age-of-the-Solar-System.pdf">Archived</a> 2012-03-09 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> <i>Creation Ex-Nihilo Technical Journal</i>, Volume 7, Number 1, 1993, p. 242.</span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWilhelms1993" class="citation cs2">Wilhelms, Don E. (1993), <a rel="nofollow" class="external text" href="https://archive.org/details/torockymoongeolo0000wilh/page/97"><i>To a Rocky Moon: A Geologist's History of Lunar Exploration</i></a>, <a href="/wiki/University_of_Arizona_Press" title="University of Arizona Press">University of Arizona Press</a>, p. <a rel="nofollow" class="external text" href="https://archive.org/details/torockymoongeolo0000wilh/page/97">97</a>, <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0816510658" title="Special:BookSources/978-0816510658"><bdi>978-0816510658</bdi></a></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=To+a+Rocky+Moon%3A+A+Geologist%27s+History+of+Lunar+Exploration&rft.pages=97&rft.pub=University+of+Arizona+Press&rft.date=1993&rft.isbn=978-0816510658&rft.aulast=Wilhelms&rft.aufirst=Don+E.&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Ftorockymoongeolo0000wilh%2Fpage%2F97&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMicrometeoroid" class="Z3988"></span></span> </li> <li id="cite_note-:0-12"><span class="mw-cite-backlink">^ <a href="#cite_ref-:0_12-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:0_12-1"><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="CITEREFRodriguez2010" class="citation web cs1">Rodriguez, Karen (April 26, 2010). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20091028100716/http://www.nasa.gov/centers/wstf/laboratories/hypervelocity/mmod.html">"Micrometeoroids and Orbital Debris (MMOD)"</a>. <i>www.nasa.gov</i>. Archived from <a rel="nofollow" class="external text" href="https://www.nasa.gov/centers/wstf/laboratories/hypervelocity/mmod.html">the original</a> on October 28, 2009<span class="reference-accessdate">. Retrieved <span class="nowrap">2018-06-18</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.nasa.gov&rft.atitle=Micrometeoroids+and+Orbital+Debris+%28MMOD%29&rft.date=2010-04-26&rft.aulast=Rodriguez&rft.aufirst=Karen&rft_id=https%3A%2F%2Fwww.nasa.gov%2Fcenters%2Fwstf%2Flaboratories%2Fhypervelocity%2Fmmod.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMicrometeoroid" 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="CITEREFSwanRaittSwanPenny2013" class="citation book cs1">Swan, Peter A.; Raitt, David I.; Swan, Cathy W.; Penny, Robert E.; Knapman, John M. (2013). <i>Space Elevators: An Assessment of the Technological Feasibility and the Way Forward</i>. Virginia, USA: International Academy of Astronautics. pp. 10–11, 207–208. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9782917761311" title="Special:BookSources/9782917761311"><bdi>9782917761311</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Space+Elevators%3A+An+Assessment+of+the+Technological+Feasibility+and+the+Way+Forward&rft.place=Virginia%2C+USA&rft.pages=10-11%2C+207-208&rft.pub=International+Academy+of+Astronautics&rft.date=2013&rft.isbn=9782917761311&rft.aulast=Swan&rft.aufirst=Peter+A.&rft.au=Raitt%2C+David+I.&rft.au=Swan%2C+Cathy+W.&rft.au=Penny%2C+Robert+E.&rft.au=Knapman%2C+John+M.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMicrometeoroid" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text">Swan, P., Penny, R. Swan, C. Space Elevator Survivability, Space Debris Mitigation, Lulu.com Publishers, 2011</span> </li> <li id="cite_note-Marsden-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-Marsden_15-0">^</a></b></span> <span class="reference-text">Brian Marsden, <a rel="nofollow" class="external text" href="https://www.independent.co.uk/news/obituaries/professor-fred-whipple-533019.html">"Professor Fred Whipple: Astronomer who developed the idea that comets are 'dirty snowballs'."</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180211080325/http://www.independent.co.uk/news/obituaries/professor-fred-whipple-533019.html">Archived</a> 11 February 2018 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> <i>The Independent</i>, 13 November 2004.</span> </li> <li id="cite_note-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-16">^</a></b></span> <span class="reference-text">Fred Whipple, <a rel="nofollow" class="external text" href="http://www.sciencemag.org/cgi/content/full/289/5480/728">"Of Comets and Meteors"</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20080629032626/http://www.sciencemag.org/cgi/content/full/289/5480/728">Archived</a> 29 June 2008 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> <i>Science</i>, Volume 289 Number 5480 (4 August 2000), p. 728.</span> </li> <li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text">Judith Reustle (curator), <a rel="nofollow" class="external text" href="https://ares.jsc.nasa.gov/ares/hvit/basic.cfm">"Shield Development: Basic Concepts"</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110927133616/http://ares.jsc.nasa.gov/ares/hvit/basic.cfm">Archived</a> 27 September 2011 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, NASA HVIT. Retrieved 20 July 2011.</span> </li> <li id="cite_note-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-18">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.3m.com/market/industrial/ceramics/pdfs/CeramicFabric.pdf">Ceramic Fabric Offers Space Age Protection</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20120309094614/http://www.3m.com/market/industrial/ceramics/pdfs/CeramicFabric.pdf">Archived</a> 9 March 2012 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, 1994 Hypervelocity Impact Symposium</span> </li> <li id="cite_note-nasa20030627-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-nasa20030627_19-0">^</a></b></span> <span class="reference-text">Kim Dismukes (curator), <a rel="nofollow" class="external text" href="https://spaceflight.nasa.gov/history/station/transhab/">"TransHab Concept"</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070601021217/http://spaceflight.nasa.gov/history/station/transhab/">Archived</a> 1 June 2007 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, NASA, 27 June 2003. Retrieved 10 June 2007.</span> </li> <li id="cite_note-sdc20141006-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-sdc20141006_20-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHowell2014" class="citation news cs1">Howell, Elizabeth (2014-10-06). <a rel="nofollow" class="external text" href="http://www.space.com/27356-bigelow-inflatable-room-space-station.html">"Private Inflatable Room Launching to Space Station Next Year"</a>. <i>Space.com</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20141204004125/http://www.space.com/27356-bigelow-inflatable-room-space-station.html">Archived</a> from the original on 4 December 2014<span class="reference-accessdate">. Retrieved <span class="nowrap">2014-12-06</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Space.com&rft.atitle=Private+Inflatable+Room+Launching+to+Space+Station+Next+Year&rft.date=2014-10-06&rft.aulast=Howell&rft.aufirst=Elizabeth&rft_id=http%3A%2F%2Fwww.space.com%2F27356-bigelow-inflatable-room-space-station.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMicrometeoroid" class="Z3988"></span></span> </li> <li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</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.nasaspaceflight.com/2016/04/iss-crs-8-dragon-arrival-flawless-launch/">"ISS welcomes CRS-8 Dragon after flawless launch"</a>. 9 April 2016. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20160423015518/https://www.nasaspaceflight.com/2016/04/iss-crs-8-dragon-arrival-flawless-launch/">Archived</a> from the original on 23 April 2016<span class="reference-accessdate">. Retrieved <span class="nowrap">14 May</span> 2016</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=ISS+welcomes+CRS-8+Dragon+after+flawless+launch&rft.date=2016-04-09&rft_id=https%3A%2F%2Fwww.nasaspaceflight.com%2F2016%2F04%2Fiss-crs-8-dragon-arrival-flawless-launch%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMicrometeoroid" class="Z3988"></span></span> </li> </ol></div></div> <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=Micrometeoroid&action=edit&section=8" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Extraterrestrial_materials" title="Extraterrestrial materials">Extraterrestrial materials</a></li> <li><a href="/wiki/Interplanetary_dust_cloud" title="Interplanetary dust cloud">Interplanetary dust cloud</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=Micrometeoroid&action=edit&section=9" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="http://www.psrd.hawaii.edu/Sept07/cosmicSpherules.html">Melted Crumbs from Asteroid Vesta</a> article about micrometeorites collected in Antarctica in Planetary Science Research Discoveries educational journal</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 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href="/wiki/Template:Meteorites" title="Template:Meteorites"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Meteorites" title="Template talk:Meteorites"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Meteorites" title="Special:EditPage/Template:Meteorites"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Meteorites_and_meteoritics" style="font-size:114%;margin:0 4em"><a href="/wiki/Meteorite" title="Meteorite">Meteorites</a> and <a href="/wiki/Meteoritics" title="Meteoritics">meteoritics</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Meteorite" title="Meteorite">Meteorite</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/Glossary_of_meteoritics" title="Glossary of meteoritics">Glossary</a></li> <li><a href="/wiki/Meteorite_fall" title="Meteorite fall">Fall</a> <ul><li><a href="/wiki/Bolide" title="Bolide">bolide</a></li> <li><a href="/wiki/Impactite" title="Impactite">impactite</a></li> <li><a href="/wiki/Meteorite_fall_statistics" title="Meteorite fall statistics">statistics</a></li> <li><a href="/wiki/Strewn_field" title="Strewn field">strewn field</a></li></ul></li> <li><a href="/wiki/Meteorite_find" title="Meteorite find">Find</a> <ul><li><a href="/wiki/Meteorite_hunting" title="Meteorite hunting">hunting</a></li></ul></li> <li><a href="/wiki/List_of_largest_meteorites_on_Earth" title="List of largest meteorites on Earth">Largest</a></li> <li><a href="/wiki/Micrometeorite" title="Micrometeorite">Micrometeorite</a></li> <li><a href="/wiki/Meteorite#Notable_meteorites" title="Meteorite">Notable</a></li> <li><a href="/wiki/Parent_body" title="Parent body">Parent body</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Meteorite_classification" title="Meteorite classification">Classification</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 id="By_type,_class,clan,_group_and_grouplet" scope="row" class="navbox-group" style="width:1%">By <a href="/wiki/Category:Meteorite_types" title="Category:Meteorite types">type</a>, <a href="/wiki/Category:Meteorite_classes" title="Category:Meteorite classes">class</a>,<br /><a href="/wiki/Category:Meteorite_clans" title="Category:Meteorite clans">clan</a>, <a href="/wiki/Category:Meteorite_groups" title="Category:Meteorite groups">group</a><br /> and <a href="/wiki/Category:Meteorite_grouplets" title="Category:Meteorite grouplets">grouplet</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%"><a href="/wiki/Chondrite" title="Chondrite">Chondrite</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/Carbonaceous_chondrite" title="Carbonaceous chondrite">Carbonaceous</a> <ul><li>CB</li> <li>CH</li> <li><a href="/wiki/CI_chondrite" title="CI chondrite">CI</a></li> <li>CK</li> <li>CM</li> <li>CO</li> <li>CR</li> <li>CV</li> <li>C ungrouped</li></ul></li> <li><a href="/wiki/Enstatite_chondrite" title="Enstatite chondrite">Enstatite</a> <ul><li>EH</li> <li>EL</li></ul></li> <li><a href="/wiki/Chondrite#Kakangari_chondrites" title="Chondrite">Kakangari</a></li> <li><a href="/wiki/Ordinary_chondrite" title="Ordinary chondrite">Ordinary</a> <ul><li><a href="/wiki/H_chondrite" title="H chondrite">H</a></li> <li><a href="/wiki/L_chondrite" title="L chondrite">L</a></li> <li><a href="/wiki/LL_chondrite" title="LL chondrite">LL</a></li></ul></li> <li><a href="/wiki/Chondrite#Rumuruti_chondrites" title="Chondrite">Rumuruti</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Achondrite" title="Achondrite">Achondrite</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%"><a href="/wiki/Primitive_achondrite" title="Primitive achondrite">Primitive</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/Acapulcoite" title="Acapulcoite">Acapulcoite</a></li> <li><a href="/wiki/Brachinite" title="Brachinite">Brachinite</a></li> <li><a href="/wiki/IAB_meteorites" class="mw-redirect" title="IAB meteorites">IAB</a></li> <li><a href="/wiki/IIICD_meteorite" title="IIICD meteorite">IIICD</a></li> <li><a href="/wiki/Lodranite" title="Lodranite">Lodranite</a></li> <li><a href="/wiki/Ureilite" title="Ureilite">Ureilite</a></li> <li><a href="/wiki/Winonaite" title="Winonaite">Winonaite</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Asteroidal_achondrite" class="mw-redirect" title="Asteroidal achondrite">Asteroidal</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/Angrite" title="Angrite">Angrite</a></li> <li><a href="/wiki/Aubrite" title="Aubrite">Aubrite</a></li> <li><a href="/wiki/HED_meteorite" title="HED meteorite">HED</a> <ul><li><a href="/wiki/Diogenite" title="Diogenite">Diogenite</a></li> <li><a href="/wiki/Eucrite" title="Eucrite">Eucrite</a></li> <li><a href="/wiki/Howardite" title="Howardite">Howardite</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Lunar_meteorite" title="Lunar meteorite">Lunar</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/Impact_breccia" class="mw-redirect" title="Impact breccia">Impact breccia</a></li> <li><a href="/wiki/Mare_basalts" class="mw-redirect" title="Mare basalts">Mare basalts</a></li> <li><a href="/wiki/List_of_lunar_meteorites" title="List of lunar meteorites">List</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Martian_meteorite" title="Martian meteorite">Martian</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/Northwest_Africa_7034" title="Northwest Africa 7034">Basaltic Breccia</a> <ul><li><a href="/wiki/Northwest_Africa_7034" title="Northwest Africa 7034">NWA 7034</a></li></ul></li> <li><a href="/wiki/Chassignites" class="mw-redirect" title="Chassignites">Chassignites</a></li> <li><a href="/wiki/Kaidun_meteorite" title="Kaidun meteorite">Kaidun</a></li> <li><a href="/wiki/Nakhlite" title="Nakhlite">Nakhlites</a></li> <li><a href="/wiki/Orthopyroxenite" title="Orthopyroxenite">Orthopyroxenite</a> <ul><li><a href="/wiki/Allan_Hills_84001" title="Allan Hills 84001">ALH84001</a></li></ul></li> <li><a href="/wiki/Martian_meteorite#Shergottites" title="Martian meteorite">Shergottites</a></li> <li><a href="/wiki/List_of_Martian_meteorites" title="List of Martian meteorites">Martian meteorites list</a></li> <li><a href="/wiki/List_of_meteorites_on_Mars" class="mw-redirect" title="List of meteorites on Mars">Meteorites on Mars list</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Iron_meteorite" title="Iron meteorite">Iron</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>IC</li> <li><a href="/wiki/IIAB_meteorites" title="IIAB meteorites">IIAB</a></li> <li>IIC</li> <li>IID</li> <li><a href="/wiki/IIE_iron_meteorite" title="IIE iron meteorite">IIE</a></li> <li><a href="/wiki/IIG_meteorite" title="IIG meteorite">IIG</a></li> <li>IIIAB</li> <li>IIIE</li> <li>IIIF</li> <li>IVA</li> <li><a href="/wiki/IVB_meteorite" title="IVB meteorite">IVB</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Stony-iron_meteorite" title="Stony-iron meteorite">Stony-iron</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/Mesosiderite" title="Mesosiderite">Mesosiderite</a></li> <li><a href="/wiki/Pallasite" title="Pallasite">Pallasite</a> <ul><li><a href="/wiki/Pallasite_main_group" title="Pallasite main group">Main group</a></li> <li><a href="/wiki/Eagle_Station_group" title="Eagle Station group">Eagle Station</a></li> <li><a href="/wiki/Pyroxene_pallasite_grouplet" title="Pyroxene pallasite grouplet">Pyroxene</a></li></ul></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Structural</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/Ataxite" title="Ataxite">Ataxite</a></li> <li><a href="/wiki/Hexahedrite" title="Hexahedrite">Hexahedrite</a></li> <li><a href="/wiki/Octahedrite" title="Octahedrite">Octahedrite</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Obsolete terms</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/Amphoterite" title="Amphoterite">Amphoterite</a></li> <li><a href="/wiki/Nonmagmatic_meteorite" title="Nonmagmatic meteorite">Nonmagmatic meteorite</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Mineralogy" title="Mineralogy">Mineralogy</a> <br />and <a href="/wiki/Petrology" title="Petrology">petrology</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>Characteristics <ul><li><a href="/wiki/Meteorite_shock_stage" title="Meteorite shock stage">shock</a></li> <li><a href="/wiki/Total_known_weight" title="Total known weight">TKW</a></li> <li><a href="/wiki/Meteorite_weathering" title="Meteorite weathering">weathering</a></li></ul></li> <li>Grains <ul><li><a href="/wiki/Chondrule" title="Chondrule">chondrule</a></li> <li><a href="/wiki/Presolar_grains" title="Presolar grains">presolar</a></li></ul></li> <li><a href="/wiki/List_of_meteorite_minerals" title="List of meteorite minerals">Minerals</a> <ul><li><a href="/wiki/Calcium%E2%80%93aluminium-rich_inclusion" title="Calcium–aluminium-rich inclusion">Ca–Al-rich inclusion</a></li> <li><a href="/wiki/Extraterrestrial_materials" title="Extraterrestrial materials">extraterrestrial materials</a></li> <li><a href="/wiki/Meteoric_iron" title="Meteoric iron">meteoric iron</a></li></ul></li> <li>Patterns <ul><li><a href="/wiki/Neumann_lines" title="Neumann lines">Neumann lines</a></li> <li><a href="/wiki/Widmanst%C3%A4tten_pattern" title="Widmanstätten pattern">Widmanstätten</a></li></ul></li> <li><a href="/wiki/CI1_fossils" title="CI1 fossils">CI1 fossils</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Lists</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>Meteorites by <ul><li><a href="/wiki/Category:Meteorites_by_find_location" title="Category:Meteorites by find location">find location</a></li> <li><a href="/wiki/Category:Meteorites_by_type" title="Category:Meteorites by type">type</a></li></ul></li> <li><a href="/wiki/Category:Meteorite_prizes" title="Category:Meteorite prizes">Awards</a></li> <li><a href="/wiki/Category:Meteoritics_publications" title="Category:Meteoritics publications">Journals</a></li> <li><a href="/wiki/Category:Meteorite_organizations" title="Category:Meteorite organizations">Organizations</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><i>See also:</i> <a href="/wiki/Asteroid" title="Asteroid">Asteroid</a></li> <li><a href="/wiki/Atmospheric_entry" title="Atmospheric entry">Atmospheric entry</a></li> <li><a href="/wiki/Comet" title="Comet">Comet</a></li> <li><a href="/wiki/Impact_event" title="Impact event">Impact event</a></li> <li><a href="/wiki/Meteor" class="mw-redirect" title="Meteor">Meteor</a> <ul><li><a href="/wiki/Meteor_shower" title="Meteor shower">shower</a></li></ul></li> <li><a href="/wiki/Meteoroid" title="Meteoroid">Meteoroid</a></li> <li><a href="/wiki/Near-Earth_object" title="Near-Earth object">Near-Earth object</a></li></ul> </div></td></tr></tbody></table></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=Micrometeoroid&oldid=1233868656">https://en.wikipedia.org/w/index.php?title=Micrometeoroid&oldid=1233868656</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:Meteoroids" 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