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Planetary surface
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<h2 id="distribution-and-conditions">Distribution and conditions</h2> <p>Planetary surfaces are found throughout the <a href="/facts/Solar_System/QIcLSazQ">Solar System</a>, from the inner <a href="/facts/Terrestrial_planet/jpMC1ULt">terrestrial planets</a>, to the <a href="/facts/Asteroid_belt/YHAq2Eh3">asteroid belt</a>, the natural satellites of the <a href="/facts/Giant_planet/PjSfFuUF">giant planets</a> and beyond to the <a href="/facts/Trans-Neptunian_object/oF5vsbz9">Trans-Neptunian objects</a>. Surface conditions, temperatures and <a href="/facts/Terrain/r2lduLeI">terrain</a> vary significantly due to a number of factors including <a href="/facts/Albedo/TJDRdKEB">Albedo</a> often generated by the surfaces itself. Measures of surface conditions include <a href="/facts/Surface_area/WNowzFCw">surface area</a>, <a href="/facts/Surface_gravity/Q5QVbA7e">surface gravity</a>, <a href="/facts/Planetary_equilibrium_temperature/3jfAPVzE">surface temperature</a> and <a href="/facts/Atmospheric_pressure/wJLMSaVG">surface pressure</a>. Surface stability may be affected by erosion through <a href="/facts/Aeolian_processes/HpjdrW4l">Aeolian processes</a>, <a href="/facts/Hydrology/Xh727cnE">hydrology</a>, <a href="/facts/Subduction/rkasNdTo">subduction</a>, <a href="/facts/Volcanism/0s6p1eFJ">volcanism</a>, <a href="/facts/Sediment/zsIH1A6U">sediment</a> or <a href="/facts/Seismic/Lony1LYX">seismic</a> activity. Some surfaces are dynamic while others remain unchanged for millions of years. </p> <h2 id="exploration">Exploration</h2> <p>Distance, gravity, atmospheric conditions (extremely low or extremely high <a href="/facts/Atmospheric_pressure/wJLMSaVG">atmospheric pressure</a>) and unknown factors make exploration both costly and risky. This necessitates the space probes for early exploration of planetary surfaces. Many probes are stationary have a limited study range and generally survive on extraterrestrial surfaces for a short period, however mobile probes (rovers) have surveyed larger surface areas. <a href="/facts/Sample_return_mission/0bcaFtVx">Sample return missions</a> allow scientist to study extraterrestrial surface materials on Earth without having to send a crewed mission, however is generally only feasible for objects with low gravity and atmosphere. </p> <h3>Past missions</h3> <p>The first extraterrestrial planetary surface to be explored was the <a href="/facts/Lunar_surface/vhIu0V7k">lunar surface</a> by <a href="/facts/Luna_2/MxehgaRu">Luna 2</a> in 1959. The first and only human exploration of an extraterrestrial surface was the Moon, the <a href="/facts/Apollo_program/IC1Ek1Ao">Apollo program</a> included the first moonwalk on July 20, 1969, and successful return of extraterrestrial surface samples to Earth. <a href="/facts/Venera_7/3ryeSMHF">Venera 7</a> was the first landing of a probe on another planet on December 15, 1970. <a href="/facts/Mars_3/MKTBqEBD">Mars 3</a> "soft landed" and returned data from Mars on August 22, 1972, the first rover on Mars was <a href="/facts/Mars_Pathfinder/frq9TKut">Mars Pathfinder</a> in 1997, the <a href="/facts/Mars_Exploration_Rover/74WxIsHS">Mars Exploration Rover</a> has been studying the surface of the red planet since 2004. <a href="/facts/NEAR_Shoemaker/1Wblm4KL">NEAR Shoemaker</a> was the first to soft land on an asteroid – <a href="/facts/433_Eros/QWmGbK63">433 Eros</a> in February 2001 while <a href="/facts/Hayabusa/kFalgese">Hayabusa</a> was the first to return samples from <a href="/facts/25143_Itokawa/V57ybCSg">25143 Itokawa</a> on 13 June 2010. <i><a href="/facts/Huygens_(spacecraft)/a4CxSs7N">Huygens</a></i> soft landed and returned data from <a href="/facts/Titan_(moon)/lg0l9PCH">Titan</a> on January 14, 2005. </p><p>There have been many failed attempts, more recently <a href="/facts/Fobos-Grunt/mDKzr71w">Fobos-Grunt</a>, a sample return mission aimed at exploring the surface of <a href="/facts/Phobos_(moon)/qqS9JvuG">Phobos</a>. </p> <h2 id="forms">Forms</h2> <p>The surfaces of Solar System objects, other than the four <a href="/facts/Outer_Solar_System/QIcLSazQ">Outer Solar System</a> giant planets, are mostly solid, with few having liquid surfaces. </p><p>In general <a href="/facts/Terrestrial_planet/jpMC1ULt">terrestrial planets</a> have either <a href="/facts/Ice_planet/GGA9fSc6">surfaces of ice</a>, or surface <a href="/facts/Crust_(geology)/FYG1kP4F">crusts</a> of <a href="/facts/Rock_(geology)/FXCJkmop">rock</a> or <a href="/facts/Regolith/EdXuHK56">regolith</a>, with distinct <a href="/facts/Terrain/r2lduLeI">terrains</a>. Water ice predominates surfaces in the Solar System beyond the <a href="/facts/Frost_line_(astrophysics)/jIvm90Mm">frost line</a> in the Outer Solar System, with a range of <a href="/facts/Ice_planet/GGA9fSc6">icy celestial bodies</a>. Rock and regolith is <a href="/facts/Geology_of_solar_terrestrial_planets/tYYQTApK">common in the Inner Solar System</a> until Mars. </p><p>The only Solar System object having a mostly liquid surface is Earth, with its global <a href="/facts/Ocean_surface/8W8lYgjD">ocean surface</a> comprising 70.8 % of <a href="/facts/Earth%2527s_surface/HLLmDfj0">Earth's surface</a>, filling its <a href="/facts/Oceanic_basin/TKKHflL6">oceanic basins</a> and covering Earth's <a href="/facts/Oceanic_crust/0lGjI7jN">oceanic crust</a>, making Earth an <a href="/facts/Ocean_world/Ml33anp6">ocean world</a>. The remaining part of its surface consists of rocky or organic carbon and silicon rich <a href="/facts/Chemical_compound/37FXqqtv">compounds</a>. </p> <p>Liquid water as surface, beside on Earth, has only been found, as <a href="/facts/Seasonal_flows_on_warm_Martian_slopes/n38qcelY">seasonal flows on warm Martian slopes</a>, as well as past occurrences, and suspected at the <a href="/facts/Habitable_zone/bjgaUkfB">habitable zones</a> of other <a href="/facts/Planetary_system/6mcVtrTC">planetary systems</a>. Surface liquid of any kind, has been found notably on <a href="/facts/Titan_(moon)/lg0l9PCH">Titan</a>, having large <a href="/facts/Methane/kBHneYnh">methane</a> lakes, some of which are the <a href="/facts/List_of_largest_lakes_and_seas_in_the_Solar_System/gW6p8w19">largest known lakes in the Solar System</a>. </p><p><a href="/facts/Volcanism/0s6p1eFJ">Volcanism</a> can cause flows such as <a href="/facts/Lava/q2an5SVN">lava</a> on the surface of geologically active bodies (the largest being the <a href="/facts/Amirani_(volcano)/BaLhcQzG">Amirani (volcano)</a> flow on Io). Many of Earth's <a href="/facts/Igneous_rock/xeMJhUah">Igneous rocks</a> are formed through processes rare elsewhere, such as the presence of volcanic magma and water. Surface mineral deposits such as <a href="/facts/Olivine/tLLL4rae">olivine</a> and <a href="/facts/Hematite/716YBzGr">hematite</a> discovered on Mars by lunar rovers provide direct evidence of past stable <a href="/facts/Water_on_Mars/uBNTfa37">water on the surface of Mars</a>. </p><p>Apart from water, many other abundant surface materials are unique to Earth in the Solar System as they are not only <a href="/facts/Organic_compound/gqCNaN45">organic</a> but have formed due to the presence of life – these include <a href="/facts/Carbonate_hardgrounds/Doa9pJxN">carbonate hardgrounds</a>, <a href="/facts/Limestone/8ntvtFnR">limestone</a>, <a href="/facts/Vegetation/nAHr9kjk">vegetation</a> and artificial structures although the latter is present due to probe exploration (see also <a href="/facts/List_of_artificial_objects_on_extra-terrestrial_surfaces/FEft5jxC">List of artificial objects on extra-terrestrial surfaces</a>). </p> <h3>Extraterrestrial organic compounds</h3> <p>Increasingly, organic compounds are being found on objects throughout the Solar System. While unlikely to indicate the presence of extraterrestrial life, all known life is based on these compounds. Complex carbon molecules may form through various complex chemical interactions or delivered through impacts with small solar system objects and can combine to form the "building blocks" of <a href="/facts/Carbon-based_life/hBEUtBtu">carbon-based life</a>. As organic compounds are often <a href="/facts/Volatile_organic_compound/BFMlKwgt">volatile</a>, their persistence as a solid or liquid on a planetary surface is of scientific interest as it would indicate an intrinsic source (such as from the object's interior) or residue from larger quantities of organic material preserved through special circumstances over geological timescales, or an extrinsic source (such as from past or recent collision with other objects).<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> Radiation makes the detection of organic matter difficult, making its detection on atmosphereless objects closer to the Sun extremely difficult.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p><p>Examples of likely occurrences include: </p> <ul><li><a href="/facts/Tholin/DLuT4Tde">Tholins</a> – many Trans Neptunian Objects including Pluto-Charon,<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> Titan,<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> Triton,<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> <a href="/facts/Eris_(dwarf_planet)/vuaR65F7">Eris</a>,<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> <a href="/facts/90377_Sedna/6aXuaYoM">Sedna</a>,<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> 28978 Ixion,<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> 90482 Orcus,<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> <a href="/facts/24_Themis/x3a5cdxm">24 Themis</a><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a><a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a></li> <li><a href="/facts/Methane_clathrate/s1USL49e">Methane clathrate</a> (CH4·5.75H2O) – <a href="/facts/Oberon_(moon)/Xmfrr6aK">Oberon</a>, <a href="/facts/Titania_(moon)/Ts4j9JLM">Titania</a>, <a href="/facts/Umbriel/U16UuENx">Umbriel</a>, <a href="/facts/Pluto/egq7MBeR">Pluto</a>, 90482 Orcus, <a href="/facts/Comet_67P/FBdA81uy">Comet 67P</a></li></ul> <h4>On Mars</h4> <p>Martian exploration including samples taken by on the ground rovers and spectroscopy from orbiting satellites have revealed the presence of a number of complex organic molecules, some of which could be biosignatures in the search for life. </p> <ul><li><a href="/facts/Thiophene/pQhcmsCK">Thiophene</a> (C4H4S)<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a></li> <li><a href="/facts/Polythiophene/hxWfRhS7">Polythiophene</a> (polymer of C4H4S)<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a></li> <li><a href="/facts/Methanethiol/hKk384K1">Methanethiol</a> (CH3SH)<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a></li> <li><a href="/facts/Dimethyl_sulfide/mUrg1jol">Dimethyl sulfide</a> (CH2S)<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a></li></ul> <h4>On Ceres</h4> <ul><li><a href="/facts/Ammonium_bicarbonate/NKAfhKEp">Ammonium bicarbonate</a> (NH4HCO3).<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a><a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a></li> <li><a href="/facts/Gilsonite/7s8xE9wq">Gilsonite</a><a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a></li></ul> <h4>On Enceladus</h4> <ul><li><a href="/facts/Methylamine/srMMDp0D">Methylamine</a>/Ethylamine<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> (<a href="/facts/Methyl/fkM97EMD">CH3</a> <a href="/facts/Amine/SN7W44fv">NH2</a>)</li> <li><a href="/facts/Acetaldehyde/QllLbSUe">Acetaldehyde</a><a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> (<a href="/facts/Methyl/fkM97EMD">CH3</a> <a href="/facts/Formyl/xSIRkW03">CHO</a>)</li></ul> <h4>On Comet 67P</h4> <p>The space probe <a href="/facts/Philae_(spacecraft)/MzUzq8f0">Philae (spacecraft)</a> discovered the following organic compounds on the surface of Comet 67P:.<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a><a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a><a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a> </p> <ul><li><a href="/facts/Acetamide/3coa1Ez5">Acetamide</a> (CH3CONH2)</li> <li><a href="/facts/Acetone/cVyJxKqw">Acetone</a> (CH3)2CO</li> <li><a href="/facts/Methyl_isocyanate/N9hgqxLe">Methyl isocyanate</a> (CH3NCO)</li> <li><a href="/facts/Propionaldehyde/N6wpBbxx">Propionaldehyde</a> (CH3CH2CHO)</li></ul> <h3>Inorganic materials</h3> <p>The following is a non-exhaustive list of surface materials that occur on more than one planetary surface along with their locations in order of distance from the Sun. Some have been detected by spectroscopy or direct imaging from orbit or flyby. </p> <ul><li><a href="/facts/Ice/BGvkKFjD">Ice</a> (H2O) – Mercury (polar); Earth-Moon system;<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> Mars (polar); <a href="/facts/Ceres_(dwarf_planet)/yIVEMYtG">Ceres</a><a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> and some asteroids such as <a href="/facts/24_Themis/x3a5cdxm">24 Themis</a>;<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> Jupiter moons – <a href="/facts/Europa_(moon)/2A9nleK3">Europa</a>,<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> <a href="/facts/Ganymede_(moon)/AmKsF10c">Ganymede</a> and <a href="/facts/Callisto_(moon)/et0eIutu">Callisto</a>; <a href="/facts/Triton_(moon)/mxxRUygc">Triton</a>,;<a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a> Saturn moons – Titan and <a href="/facts/Enceladus_(moon)/DyWXz9jl">Enceladus</a>; Uranus moons – <a href="/facts/Miranda_(moon)/ILmQCtMM">Miranda</a>, <a href="/facts/Umbriel/U16UuENx">Umbriel</a>, <a href="/facts/Oberon_(moon)/Xmfrr6aK">Oberon</a>; <a href="/facts/Kuiper_belt/IvLzYp5P">Kuiper belt</a> objects including <a href="/facts/Pluto/egq7MBeR">Pluto</a>-<a href="/facts/Charon_(moon)/elazjsMp">Charon</a> system, <a href="/facts/Haumea_(dwarf_planet)/C1xJDm3B">Haumea</a>, <a href="/facts/28978_Ixion/6u3CyF31">28978 Ixion</a>, <a href="/facts/90482_Orcus/PbDdmqbd">90482 Orcus</a>, <a href="/facts/50000_Quaoar/Yweth54G">50000 Quaoar</a></li> <li><a href="/facts/Silicate/7NdthSRM">Silicate</a> rock – Mercury, Venus, Earth, Mars, asteroids, <a href="/facts/Ganymede_(moon)/AmKsF10c">Ganymede</a>, <a href="/facts/Callisto_(moon)/et0eIutu">Callisto</a>, Moon, Triton</li> <li><a href="/facts/Regolith/EdXuHK56">Regolith</a> – Mercury;<a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a> Venus,<a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a> Earth-Moon system; Mars (and its moons <a href="/facts/Phobos_(moon)/qqS9JvuG">Phobos</a> and <a href="/facts/Deimos_(moon)/Sm30nJWY">Deimos</a>); asteroids (including <a href="/facts/4_Vesta/xnQ8acw1">4 Vesta</a><a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a>); Titan</li> <li><a href="/facts/Solid_nitrogen/6KF2HYIx">Nitrogen ice</a> (N) – <a href="/facts/Pluto/egq7MBeR">Pluto</a>–Charon,<a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a> <a href="/facts/Triton_(moon)/mxxRUygc">Triton</a>,<a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a> <a href="/facts/Kuiper_belt/IvLzYp5P">Kuiper belt</a> objects, <a href="/facts/Plutino/ptGoJLgF">Plutinos</a></li> <li><a href="/facts/Sulphur/IK0amTfM">Sulphur</a> (S) – Mercury; Earth; Mars; Jupiter moons – Io and Europa</li></ul> <h4>Rare inorganics</h4> <ul><li><a href="/facts/Salt_(chemistry)/lsSKwGpn">Salts</a> – Earth, Mars, Ceres, Europa and Jupiter Trojans,<a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a> Enceladus<a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a></li> <li><a href="/facts/Clay_mineral/A1Sod7Hp">Clays</a> – Earth; Mars;<a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a> asteroids including Ceres<a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a> and <a href="/facts/Tempel_1/e0PnhUdh">Tempel 1</a>;<a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a> Europa<a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a></li> <li><a href="/facts/Sand/MdTIt0M8">Sand</a> – Earth, Mars, Titan</li> <li><a href="/facts/Calcium_carbonate/UQ1wLFna">Calcium carbonate</a> (CaCO3) – Earth, Mars<a class="footnote-ref" id="fnref:43" href="#fn:43"><sup>43</sup></a><a class="footnote-ref" id="fnref:44" href="#fn:44"><sup>44</sup></a></li> <li><a href="/facts/Sodium_carbonate/P6RHvIoK">Sodium carbonate</a> (Na2CO3) – Earth, Ceres<a class="footnote-ref" id="fnref:45" href="#fn:45"><sup>45</sup></a><a class="footnote-ref" id="fnref:46" href="#fn:46"><sup>46</sup></a><a class="footnote-ref" id="fnref:47" href="#fn:47"><sup>47</sup></a></li></ul> <h5>Carbon Ices</h5> <ul><li><a href="/facts/Dry_ice/BvW99HtH">Dry ice</a> (CO2) – Mars (polar);<a class="footnote-ref" id="fnref:48" href="#fn:48"><sup>48</sup></a> Ariel;<a class="footnote-ref" id="fnref:49" href="#fn:49"><sup>49</sup></a> Umbriel;<a class="footnote-ref" id="fnref:50" href="#fn:50"><sup>50</sup></a> Titania;<a class="footnote-ref" id="fnref:51" href="#fn:51"><sup>51</sup></a> Ganymede;<a class="footnote-ref" id="fnref:52" href="#fn:52"><sup>52</sup></a> Callisto<a class="footnote-ref" id="fnref:53" href="#fn:53"><sup>53</sup></a></li></ul> <ul><li><a href="/facts/Carbon_monoxide/CKuLtEMJ">Carbon monoxide</a> ice (CO) - Triton<a class="footnote-ref" id="fnref:54" href="#fn:54"><sup>54</sup></a></li></ul> <h2 id="landforms">Landforms</h2> <p>Common rigid surface features include: </p> <ul><li><a href="/facts/Impact_crater/nWntooh4">Impact craters</a> (though rarer on bodies with thick atmospheres, the largest being <a href="/facts/Hellas_Planitia/sX6et9v8">Hellas Planitia</a> on <a href="/facts/Mars/AQGtVvz0">Mars</a>)</li> <li><a href="/facts/List_of_extraterrestrial_dune_fields/9jQkdGED">Dunes</a> as found on Venus, Earth, Mars and Titan</li> <li><a href="/facts/List_of_extraterrestrial_volcanoes/HVsFejCg">volcanoes</a> and <a href="/facts/Cryovolcanoes/YyWhVCJ3">cryovolcanoes</a></li> <li><a href="/facts/Rille/UHbe2Wdm">Rilles</a></li> <li><a href="/facts/List_of_tallest_mountains_in_the_Solar_System/hvppaJvg">Mountains</a> (the highest being <a href="/facts/Rheasilvia/P0dq18De">Rheasilvia</a> on <a href="/facts/4_Vesta/xnQ8acw1">4 Vesta</a>)</li> <li><a href="/facts/Escarpment/apJ1d2XB">Escarpments</a></li> <li>Canyons and <a href="/facts/Valley/gKmvE6L1">valleys</a> (the largest being <a href="/facts/Valles_Marineris/Yn3xDfDl">Valles Marineris</a> on Mars)</li> <li><a href="/facts/Cave/SNfJTJtM">Caves</a></li> <li><a href="/facts/Lava_tube/UmD2vNro">Lava tubes</a>, found on Venus, Earth, The Moon and Mars</li></ul> <h2 id="surface-of-giant-planets">Surface of giant planets</h2> <p>Normally, <a href="/facts/Giant_planet/PjSfFuUF">giant planets</a> are considered to not have a surface, although they might have a solid core of rock or various types of ice, or a liquid core of <a href="/facts/Metallic_hydrogen/Wc4P3R6I">metallic hydrogen</a>. However, the core, if it exists, does not include enough of the planet's mass to be actually considered a surface. Some scientists consider the point at which the atmospheric pressure is equal to 1 <a href="/facts/Bar_(unit)/wwFWTTkT">bar</a>, equivalent to the atmospheric pressure at Earth's surface, to be the surface of the planet,<a href="http://www.universetoday.com/22719/surface-of-jupiter/">[1]</a> if the planet has no clear rigid terrain. Therefore the location of the surface of terrestrial planets do not depend on an atmospheric pressure of 1 Bar, even if for example <a href="/facts/Atmosphere_of_Venus/N4psbW2p">Venus has a thick atmosphere</a> with pressures at Venus's surface increasing well above Earth's atmospheric pressure. </p> <h2 id="life">Life</h2> <p class="note">Main articles: <a href="/facts/Planetary_habitability/n8A0ehR8">Planetary habitability</a>, <a href="/facts/Biosignature/vaG06nRB">Biosignature</a>, and <a href="/facts/Lunar_habitation/PRvH0tGl">Lunar habitation</a></p> <p>Planetary surfaces are investigated for the presence of past or present <a href="/facts/Extraterrestrial_life/arxCPFTQ">extraterrestrial life</a>. </p> <h2 id="gallery">Gallery</h2> Some planetary surfaces of the Solar System and their compositions <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Extraterrestrial_atmosphere/m2IsfwJ3">Extraterrestrial atmosphere</a></li> <li><a href="/facts/Hydrosphere/RbJmcSX6">Hydrosphere</a> <ul><li><a href="/facts/Subsurface_ocean/8W8lYgjD">Subsurface ocean</a></li> <li><a href="/facts/Ocean_world/Ml33anp6">Ocean world</a></li></ul></li> <li><a href="/facts/Planetary_radius/PgECMfzl">Planetary radius</a></li> <li><a href="/facts/Planetary_geoid/PgECMfzl">Planetary geoid</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Meyer, Charles; Treiman, Allan H.; Kostiuk, Theodor, eds. (May 12–13, 1995). Planetary Surface Instruments Workshop (PDF). Houston, Texas: Lunar and Planetary Institute. p. 3. Bibcode:1996psi..work.....M. Retrieved 2012-02-10. <a href="http://www.lpi.usra.edu/publications/psiw/psiw.pdf" target="_blank">http://www.lpi.usra.edu/publications/psiw/psiw.pdf</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"Planetary Surface Materials Haskin Research Group". Department of Earth and Planetary Sciences | Washington University in St. Louis. Archived from the original on Mar 10, 2014. Retrieved 2012-02-10. <a href="https://web.archive.org/web/20140310170859/http://epsc.wustl.edu/haskin-group/" target="_blank">https://web.archive.org/web/20140310170859/http://epsc.wustl.edu/haskin-group/</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Melosh, Jay (August 2007). Planetary Surface Processes. Cambridge Planetary Science. p. 9. 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