Editing Solar System (section)

== Inner Solar System ==
The inner Solar System is the region comprising the [[#Terrestrial planets|terrestrial planets]] and the [[asteroid]]s.<ref>{{Cite web |title=Inner Solar System |url=https://science.nasa.gov/solar-system/focus-areas/inner-solar-system |url-status=live |archive-url=https://web.archive.org/web/20220410004501/https://science.nasa.gov/solar-system/focus-areas/inner-solar-system |archive-date=10 April 2022 |access-date=2 April 2022 |website=NASA Science: Share the Science|date=10 May 2016 }}</ref> Composed mainly of [[silicate]]s and metals,<ref>{{Cite book |last1=Del Genio |first1=Anthony D. |title=Planetary Astrobiology |last2=Brain |first2=David |last3=Noack |first3=Lena |last4=Schaefer |first4=Laura |date=2020 |publisher=University of Arizona Press |isbn=978-0816540655 |editor-last=Meadows |editor-first=Victoria S. |page=420 |chapter=The Inner Solar System's Habitability Through Time |bibcode=2018arXiv180704776D |author-link4=Laura K. Schaefer |editor-last2=Arney |editor-first2=Giada N. |editor-last3=Schmidt |editor-first3=Britney |editor-last4=Des Marais |editor-first4=David J. |arxiv=1807.04776}}</ref> the objects of the inner Solar System are relatively close to the Sun; the radius of this entire region is less than the distance between the orbits of Jupiter and Saturn. This region is within the [[Frost line (astrophysics)|frost line]], which is a little less than {{val|5|u=AU}} from the Sun.<ref name="Levison2003"/>

=== Inner planets<span class="anchor" id="Terrestrial planets"></span> ===
{{Main|Terrestrial planet}}
[[File:Terrestrial planet sizes 3.jpg|right|thumb|alt=Venus and Earth about the same size, Mars is about 0.55 times as big and Mercury is about 0.4 times as big|The four terrestrial planets [[Mercury (planet)|Mercury]], [[Venus]], [[Earth]] and [[Mars]]]]
The four terrestrial or inner planets have dense, rocky compositions, few or no [[natural satellite|moons]], and no [[planetary ring|ring systems]]. They are composed largely of [[Refractory (planetary science)|refractory]] minerals such as [[silicates]]{{Mdash}}which form their [[crust (geology)|crusts]] and [[mantle (geology)|mantles]]{{Mdash}}and metals such as iron and nickel which form their [[planetary core|cores]]. Three of the four inner planets (Venus, Earth, and Mars) have [[atmosphere]]s substantial enough to generate weather; all have impact craters and [[tectonics|tectonic]] surface features, such as [[rift valley]]s and volcanoes.<ref name="Ryden">{{Cite journal |last=Ryden |first=Robert |date=December 1999 |title=Astronomical Math |url=https://pubs.nctm.org/view/journals/mt/92/9/article-p786.xml |url-status=live |journal=The Mathematics Teacher |volume=92 |issue=9 |pages=786–792 |doi=10.5951/MT.92.9.0786 |issn=0025-5769 |jstor=27971203 |archive-url=https://web.archive.org/web/20220412010049/https://pubs.nctm.org/view/journals/mt/92/9/article-p786.xml |archive-date=12 April 2022 |access-date=29 March 2022}}</ref>
* {{Visible anchor|Mercury|text=[[Mercury (planet)|Mercury]]}} (0.31–0.59&nbsp;AU from the Sun)<ref name="nasa-factsheet" group="D">{{Cite web |last=Williams |first=David |date=27 December 2021 |title=Planetary Fact Sheet - Metric |url=https://nssdc.gsfc.nasa.gov/planetary/factsheet |access-date=11 December 2022 |publisher=[[Goddard Space Flight Center]] |archive-date=18 August 2011 |archive-url=https://web.archive.org/web/20110818181734/http://nssdc.gsfc.nasa.gov/planetary/factsheet/ |url-status=live }}</ref> is the smallest planet in the Solar System. Its surface is grayish, with an expansive [[rupes]] (cliff) system generated from [[thrust fault]]s and bright [[ray system]]s formed by [[Ejecta|impact event remnants]].<ref>{{Cite journal |last1=Watters |first1=Thomas R. |last2=Solomon |first2=Sean C. |last3=Robinson |first3=Mark S. |last4=Head |first4=James W. |last5=André |first5=Sarah L. |last6=Hauck |first6=Steven A. |last7=Murchie |first7=Scott L. |date=August 2009 |title=The tectonics of Mercury: The view after MESSENGER's first flyby |journal=Earth and Planetary Science Letters |language=en |volume=285 |issue=3–4 |pages=283–296 |bibcode=2009E&PSL.285..283W |doi=10.1016/j.epsl.2009.01.025}}</ref> The surface has widely varying temperature, with the [[equator]]ial regions ranging from {{convert|-170|C|F|sigfig=2}} at night to {{convert|420|C|F|sigfig=2}} during sunlight. In the past, Mercury was volcanically active, producing smooth [[basalt]]ic plains similar to the Moon.<ref name=Head_et_al_1981>{{cite journal |last1=Head |first1=James W. |author-link1=James W. Head |last2=Solomon |first2=Sean C. |author-link2=Sean Solomon |year=1981 |title=Tectonic Evolution of the Terrestrial Planets |url=http://www.planetary.brown.edu/pdfs/323.pdf |url-status=dead |journal=Science |volume=213 |issue=4503 |pages=62–76 |bibcode=1981Sci...213...62H |citeseerx=10.1.1.715.4402 |doi=10.1126/science.213.4503.62 |pmid=17741171 |archive-url=https://web.archive.org/web/20180721153426/http://www.planetary.brown.edu/pdfs/323.pdf |archive-date=21 July 2018 |access-date=25 October 2017 |hdl=2060/20020090713}}</ref> It is likely that Mercury has a silicate crust and a large iron core.<ref>{{cite web |date=21 March 2012 |editor-last=Talbert |editor-first=Tricia |title=MESSENGER Provides New Look at Mercury's Surprising Core and Landscape Curiosities |url=https://www.nasa.gov/mission_pages/messenger/media/PressConf20120321.html |url-status=dead |archive-url=https://web.archive.org/web/20190112170032/https://www.nasa.gov/mission_pages/messenger/media/PressConf20120321.html |archive-date=12 January 2019 |access-date=20 April 2018 |publisher=NASA}}</ref><ref name="Margot2012">{{cite journal |last1=Margot |first1=Jean-Luc |last2=Peale |first2=Stanton J. |last3=Solomon |first3=Sean C. |last4=Hauck |first4=Steven A. |last5=Ghigo |first5=Frank D. |last6=Jurgens |first6=Raymond F. |last7=Yseboodt |first7=Marie |last8=Giorgini |first8=Jon D. |last9=Padovan |first9=Sebastiano |last10=Campbell |first10=Donald B. |year=2012 |title=Mercury's moment of inertia from spin and gravity data |journal=Journal of Geophysical Research: Planets |volume=117 |issue=E12 |pages=n/a |bibcode=2012JGRE..117.0L09M |citeseerx=10.1.1.676.5383 |doi=10.1029/2012JE004161 |issn=0148-0227 |s2cid=22408219}}</ref> Mercury has a very tenuous atmosphere, consisting of [[Solar wind|solar-wind]] particles and ejected atoms.<ref>{{Cite journal |last1=Domingue |first1=Deborah L. |last2=Koehn |first2=Patrick L. |last3=Killen |first3=Rosemary M. |last4=Sprague |first4=Ann L. |last5=Sarantos |first5=Menelaos |last6=Cheng |first6=Andrew F. |last7=Bradley |first7=Eric T. |last8=McClintock |first8=William E. |display-authors=2 |date=2009 |title=Mercury's Atmosphere: A Surface-Bounded Exosphere |journal=Space Science Reviews |volume=131 |issue=1–4 |pages=161–186 |bibcode=2007SSRv..131..161D |doi=10.1007/s11214-007-9260-9 |s2cid=121301247 |quote=The composition of Mercury's exosphere, with its abundant H and He, clearly indicates a strong solar wind source. Once solar wind plasma and particles gain access to the magnetosphere, they predominantly precipitate to the surface, where solar wind species are neutralized, thermalized, and released again into the exosphere. Moreover, bombardment of the surface by solar wind particles, especially energetic ions, contributes to ejection of neutral species from the surface into the exosphere (via "sputtering") as well as other chemical and physical surface modification processes.}}</ref> Mercury has no natural satellites.<ref name="spaceplace.nasa.gov">{{Cite web |title=How Many Moons Does Each Planet Have? {{!}} NASA Space Place – NASA Science for Kids |url=https://spaceplace.nasa.gov/how-many-moons/en/ |access-date=21 April 2024 |website=spaceplace.nasa.gov |archive-date=21 April 2024 |archive-url=https://web.archive.org/web/20240421061913/https://spaceplace.nasa.gov/how-many-moons/en/ |url-status=live }}</ref>
* {{Visible anchor|Venus|text=[[Venus]]}} (0.72–0.73&nbsp;AU)<ref name="nasa-factsheet" group="D" /> has a reflective, whitish atmosphere that is mainly composed of [[carbon dioxide]]. At the surface, the atmospheric pressure is ninety times as dense as on Earth's sea level.<ref name="u3r1a">{{cite journal |last1=Lebonnois |first1=Sebastien |last2=Schubert |first2=Gerald |date=26 June 2017 |title=The deep atmosphere of Venus and the possible role of density-driven separation of CO2 and N2 |url=https://hal.archives-ouvertes.fr/hal-01635402/file/deepatm_persp_rev2.pdf |url-status=live |journal=Nature Geoscience |publisher=Springer Science and Business Media LLC |volume=10 |issue=7 |pages=473–477 |bibcode=2017NatGe..10..473L |doi=10.1038/ngeo2971 |issn=1752-0894 |s2cid=133864520 |archive-url=https://web.archive.org/web/20190504081028/https://hal.archives-ouvertes.fr/hal-01635402/file/deepatm_persp_rev2.pdf |archive-date=4 May 2019 |access-date=11 August 2023}}</ref> Venus has a surface temperatures over {{Cvt|400|C|F}}, mainly due to the amount of [[greenhouse gas]]es in the atmosphere.<ref>{{Cite thesis |last=Bullock |first=Mark Alan |title=The Stability of Climate on Venus |date=1997 |degree=PhD |publisher=Southwest Research Institute |url=http://www.boulder.swri.edu/~bullock/Homedocs/PhDThesis.pdf |access-date=26 December 2006 |url-status=dead |archive-url=https://web.archive.org/web/20070614202751/http://www.boulder.swri.edu/~bullock/Homedocs/PhDThesis.pdf |archive-date=14 June 2007}}</ref> The planet lacks a protective magnetic field to protect against [[Atmospheric stripping|stripping]] by the solar wind, which suggests that its atmosphere is sustained by volcanic activity.<ref>{{Cite web |last=Rincon |first=Paul |date=1999 |title=Climate Change as a Regulator of Tectonics on Venus |url=http://www.boulder.swri.edu/~bullock/Homedocs/Science2_1999.pdf |url-status=dead |archive-url=https://web.archive.org/web/20070614202807/http://www.boulder.swri.edu/~bullock/Homedocs/Science2_1999.pdf |archive-date=14 June 2007 |access-date=19 November 2006 |website=Johnson Space Center Houston, TX, Institute of Meteoritics, University of New Mexico, Albuquerque, NM}}</ref> Its surface displays extensive evidence of volcanic activity with stagnant [[lid tectonics]].<ref>{{Cite journal |last1=Elkins-Tanton |first1=L. T. |last2=Smrekar |first2=S. E. |last3=Hess |first3=P. C. |last4=Parmentier |first4=E. M. |date=March 2007 |title=Volcanism and volatile recycling on a one-plate planet: Applications to Venus |journal=Journal of Geophysical Research |volume=112 |issue=E4 |bibcode=2007JGRE..112.4S06E |doi=10.1029/2006JE002793 |id=E04S06 |doi-access=free}}</ref> Venus has no natural satellites.<ref name="spaceplace.nasa.gov"/>
* {{Visible anchor|Earth|text=[[Earth]]}} (0.98–1.02&nbsp;AU)<ref name="nasa-factsheet" group="D" /> is the only place in the universe where [[life]] and [[Water distribution on Earth|surface liquid water]] are known to exist.<ref name="life">{{Cite web |title=What are the characteristics of the Solar System that lead to the origins of life? |url=https://science.nasa.gov/planetary-science/big-questions/what-are-the-characteristics-of-the-solar-system-that-lead-to-the-origins-of-life-1 |url-status=dead |archive-url=https://web.archive.org/web/20100408055814/http://science.nasa.gov/planetary-science/big-questions/what-are-the-characteristics-of-the-solar-system-that-lead-to-the-origins-of-life-1 |archive-date=8 April 2010 |access-date=30 August 2011 |publisher=NASA Science (Big Questions)}}</ref> Earth's atmosphere contains 78% [[nitrogen]] and 21% [[oxygen]], which is the result of the presence of life.<ref name="handbook">{{Cite book |title=[[CRC Handbook of Chemistry and Physics]] |publisher=CRC Press |year=2016–2017 |isbn=978-1-4987-5428-6 |editor-last=Haynes |editor-first=H. M. |edition=97th |page=14{{Hyphen}}3<!-- the page ref itself is hyphenated -->}}</ref><ref name="NYT-20131003">{{Cite news |last=Zimmer |first=Carl |author-link=Carl Zimmer |date=3 October 2013 |title=Earth's Oxygen: A Mystery Easy to Take for Granted |work=[[The New York Times]] |url=https://www.nytimes.com/2013/10/03/science/earths-oxygen-a-mystery-easy-to-take-for-granted.html |url-access=limited |access-date=3 October 2013 |archive-url=https://web.archive.org/web/20131003121909/http://www.nytimes.com/2013/10/03/science/earths-oxygen-a-mystery-easy-to-take-for-granted.html |archive-date=3 October 2013}}</ref> The planet has a complex [[climate]] and [[weather]] system, with conditions differing drastically between [[climate region]]s.<ref name="climate_zones">{{cite web |author=Staff |title=Climate Zones |url=http://www.ace.mmu.ac.uk/eae/climate/older/Climate_Zones.html |archive-url=https://web.archive.org/web/20100808131632/http://www.ace.mmu.ac.uk/eae/climate/older/Climate_Zones.html |archive-date=8 August 2010 |access-date=24 March 2007 |publisher=UK Department for Environment, Food and Rural Affairs}}</ref> The solid surface of Earth is dominated by green [[vegetation]], [[Hot deserts|deserts]] and white [[ice sheet]]s.<ref name="Carlowicz Simmon 2019">{{cite web |last1=Carlowicz |first1=Michael |last2=Simmon |first2=Robert |date=15 July 2019 |title=Seeing Forests for the Trees and the Carbon: Mapping the World's Forests in Three Dimensions |url=https://earthobservatory.nasa.gov/features/ForestCarbon#:~:text=They%20cover%20about%2030%20percent,percent%20of%20the%20Earth's%20land. |access-date=31 December 2022 |website=NASA Earth Observatory |archive-date=31 December 2022 |archive-url=https://web.archive.org/web/20221231005400/https://earthobservatory.nasa.gov/features/ForestCarbon#:~:text=They%20cover%20about%2030%20percent,percent%20of%20the%20Earth's%20land. |url-status=live }}</ref><ref name="Cain 2010">{{cite web |last=Cain |first=Fraser |date=1 June 2010 |title=What Percentage of the Earth's Land Surface is Desert? |url=https://www.universetoday.com/65639/what-percentage-of-the-earths-land-surface-is-desert/ |access-date=3 January 2023 |website=Universe Today |archive-date=3 January 2023 |archive-url=https://web.archive.org/web/20230103153344/https://www.universetoday.com/65639/what-percentage-of-the-earths-land-surface-is-desert/ |url-status=live }}</ref><ref name="National Geographic Society 2006">{{cite web |date=6 August 2006 |title=Ice Sheet |url=https://education.nationalgeographic.org/resource/ice-sheet/ |access-date=3 January 2023 |website=National Geographic Society |archive-date=27 November 2023 |archive-url=https://web.archive.org/web/20231127174259/https://education.nationalgeographic.org/resource/ice-sheet/ |url-status=live }}</ref> Earth's surface is shaped by [[plate tectonics]] that formed the continental masses.<ref name=Head_et_al_1981/> Earth's planetary [[magnetosphere]] shields the surface from radiation, limiting [[atmospheric stripping]] and maintaining life habitability.<ref>{{Cite book |last=Pentreath |first=R. J. |url=https://books.google.com/books?id=avRVEAAAQBAJ&pg=PA94 |title=Radioecology: Sources and Consequences of Ionising Radiation in the Environment |date=2021 |publisher=Cambridge University Press |isbn=978-1009040334 |pages=94–97 |access-date=12 April 2022 |archive-url=https://web.archive.org/web/20220420161217/https://www.google.com/books/edition/Radioecology/avRVEAAAQBAJ?hl=en&gbpv=1&pg=PA94 |archive-date=20 April 2022 |url-status=live}}</ref>
** The [[Moon]] is Earth's only natural satellite.<ref>{{Cite web |title=Facts About Earth - NASA Science |url=https://science.nasa.gov/earth/facts/ |access-date=11 January 2024 |website=NASA Science |date=30 May 2023 |language=en}}</ref> Its diameter is one-quarter the size of Earth's.<ref name="Metzger2021">{{Citation |last1=Metzger |first1=Philip |title=Moons are planets: Scientific usefulness versus cultural teleology in the taxonomy of planetary science |date=2021 |journal=[[Icarus (journal)|Icarus]] |volume=374 |page=114768 |arxiv=2110.15285 |bibcode=2022Icar..37414768M |doi=10.1016/j.icarus.2021.114768 |s2cid=240071005 |last2=Grundy |first2=Will |last3=Sykes |first3=Mark |last4=Stern |first4=Alan |last5=Bell |first5=James |last6=Detelich |first6=Charlene |last7=Runyon |first7=Kirby |last8=Summers |first8=Michael |author-link1=Philip T. Metzger}}</ref> Its surface is covered in [[Lunar soil|very fine regolith]] and dominated by [[impact crater]]s.<ref>{{cite web |date=30 January 2006 |title=The Smell of Moondust |url=https://science.nasa.gov/headlines/y2006/30jan_smellofmoondust.htm |url-status=dead |archive-url=https://web.archive.org/web/20100308112332/http://science.nasa.gov/headlines/y2006/30jan_smellofmoondust.htm |archive-date=8 March 2010 |access-date=15 March 2010 |publisher=NASA}}</ref><ref>{{cite book |last=Melosh |first=H. J. |title=Impact cratering: A geologic process |date=1989 |publisher=[[Oxford University Press]] |isbn=978-0-19-504284-9}}</ref> Large dark patches on the Moon, [[Lunar mare|maria]], are formed from past volcanic activity.<ref>{{cite web |last=Norman |first=M. |date=21 April 2004 |title=The Oldest Moon Rocks |url=http://www.psrd.hawaii.edu/April04/lunarAnorthosites.html |url-status=live |archive-url=https://web.archive.org/web/20070418152325/http://www.psrd.hawaii.edu/April04/lunarAnorthosites.html |archive-date=18 April 2007 |access-date=12 April 2007 |work=Planetary Science Research Discoveries |publisher=Hawai'i Institute of Geophysics and Planetology}}</ref> The Moon's atmosphere is extremely thin, consisting of a [[partial vacuum]] with particle densities of under 10<sup>7</sup> per cm<sup>−3</sup>.<ref>{{cite book |last=Globus |first=Ruth |title=Space Settlements: A Design Study |date=1977 |publisher=NASA |editor=Richard D. Johnson & Charles Holbrow |chapter=Chapter 5, Appendix J: Impact Upon Lunar Atmosphere |access-date=17 March 2010 |chapter-url=http://settlement.arc.nasa.gov/75SummerStudy/5appendJ.html |archive-url=https://web.archive.org/web/20100531205037/http://settlement.arc.nasa.gov/75SummerStudy/5appendJ.html |archive-date=31 May 2010 |url-status=dead}}</ref>
* {{Visible anchor|Mars|text=[[Mars]]}} (1.38–1.67&nbsp;AU)<ref name="nasa-factsheet" group="D" /> has a radius about half of that of Earth.<ref name="Seidelmann2007">{{cite journal |last1=Seidelmann |first1=P. Kenneth |last2=Archinal |first2=Brent A. |last3=A'Hearn<!-- written A'hearn here, mostly A'Hearn elsewhere --> |first3=Michael F. |last4=Conrad |first4=Albert R. |last5=Consolmagno |first5=Guy J. |last6=Hestroffer |first6=Daniel |last7=Hilton |first7=James L. |last8=Krasinsky |first8=Georgij A. |last9=Neumann |first9=Gregory A. |last10=Oberst |first10=Jürgen |last11=Stooke |first11=Philip J. |last12=Tedesco |first12=Edward F. |last13=Tholen |first13=David J. |last14=Thomas |first14=Peter C. |last15=Williams |first15=Iwan P. |year=2007 |title=Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements: 2006 |journal=Celestial Mechanics and Dynamical Astronomy |volume=98 |issue=3 |pages=155–180 |bibcode=2007CeMDA..98..155S |doi=10.1007/s10569-007-9072-y |ref={{sfnRef|Seidelmann Archinal A'hearn et al.|2007}} |doi-access=free}}</ref> Most of the planet is red due to [[iron(III) oxide|iron oxide]] in Martian soil,<ref>{{Cite journal |last=Peplow |first=Mark |date=6 May 2004 |title=How Mars got its rust |url=http://www.nature.com/articles/news040503-6 |url-status=live |journal=Nature |language=en |pages=news040503–6 |doi=10.1038/news040503-6 |issn=0028-0836 |archive-url=https://web.archive.org/web/20220407105832/https://www.nature.com/articles/news040503-6 |archive-date=7 April 2022 |access-date=9 April 2022}}</ref> and the polar regions are covered in [[Martian polar ice caps|white ice caps]] made of water and [[carbon dioxide]].<ref>{{Cite web |title=Polar Caps |url=https://marsed.asu.edu/mep/ice/polar-caps |access-date=6 January 2022 |website=Mars Education at Arizona State University |archive-date=28 May 2021 |archive-url=https://web.archive.org/web/20210528133135/https://marsed.asu.edu/mep/ice/polar-caps |url-status=live }}</ref> Mars has an atmosphere composed mostly of carbon dioxide, with surface pressure 0.6% of that of Earth, which is sufficient to support some weather phenomena.<ref>{{Cite book |last1=Gatling |first1=David C. |title=Encyclopaedia of the Solar System |last2=Leovy |first2=Conway |date=2007 |editor-last=Lucy-Ann McFadden |pages=301–314 |chapter=Mars Atmosphere: History and Surface Interactions |display-editors=etal}}</ref> During the Mars year (687 Earth days), there are large surface temperature swings on the surface between {{Cvt|-78.5|C|F}} to {{Cvt|5.7|C|F}}. The surface is peppered with volcanoes and [[rift valley]]s, and has a rich collection of [[mineral]]s.<ref>{{Cite web |last=Noever |first=David |date=2004 |title=Modern Martian Marvels: Volcanoes? |url=https://www.astrobio.net/mars/modern-martian-marvels-volcanoes |url-status=dead |archive-url=https://web.archive.org/web/20200314112555/https://www.astrobio.net/mars/modern-martian-marvels-volcanoes |archive-date=14 March 2020 |access-date=23 July 2006 |website=NASA Astrobiology Magazine}}</ref><ref name="ismars">[http://mars.jpl.nasa.gov/msl/multimedia/videos/index.cfm?v=29&a=2 NASA – ''Mars in a Minute: Is Mars Really Red?''] {{Webarchive|url=https://web.archive.org/web/20140720135450/http://mars.jpl.nasa.gov/msl/multimedia/videos/index.cfm?v=29&a=2|date=20 July 2014}} ([http://mars.jpl.nasa.gov/multimedia/videos/movies/miam20111110/miam20111110.pdf Transcript] {{Webarchive|url=https://web.archive.org/web/20151106174558/http://mars.jpl.nasa.gov/multimedia/videos/movies/miam20111110/miam20111110.pdf|date=6 November 2015}}) {{PD-notice}}</ref> Mars has a highly [[Planetary differentiation|differentiated]] internal structure, and lost its magnetosphere 4&nbsp;billion years ago.<ref name="Nimmo 2005">{{cite journal |last1=Nimmo |first1=Francis |last2=Tanaka |first2=Ken |year=2005 |title=Early Crustal Evolution of Mars |journal=Annual Review of Earth and Planetary Sciences |volume=33 |issue=1 |pages=133–161 |bibcode=2005AREPS..33..133N |doi=10.1146/annurev.earth.33.092203.122637 |s2cid=45843366}}</ref><ref name="swind">{{cite web |last=Philips |first=Tony |date=31 January 2001 |title=The Solar Wind at Mars |url=https://science.nasa.gov/science-news/science-at-nasa/2001/ast31jan_1/ |url-status=dead |archive-url=https://web.archive.org/web/20110818180040/https://science.nasa.gov/science-news/science-at-nasa/2001/ast31jan_1/ |archive-date=18 August 2011 |access-date=22 April 2022 |website=Science@NASA}} {{PD-notice}}</ref> [[Moons of Mars|Mars has two tiny moons]]:<ref name="NYT-20200725">{{cite news |last=Andrews |first=Robin George |date=25 July 2020 |title=Why the 'Super Weird' Moons of Mars Fascinate Scientists - What's the big deal about little Phobos and tinier Deimos? |url=https://www.nytimes.com/2020/07/25/science/mars-moons-phobos-deimos.html |url-status=live |archive-url=https://web.archive.org/web/20200725094039/https://www.nytimes.com/2020/07/25/science/mars-moons-phobos-deimos.html |archive-date=25 July 2020 |access-date=25 July 2020 |work=[[The New York Times]]}}</ref>
** [[Phobos (moon)|Phobos]] is Mars's inner moon. It is a small, irregularly shaped object with a mean radius of {{convert|11|km|abbr=on|sigfig=1}}. Its surface is very unreflective and dominated by impact craters.<ref name="jplssd" group="D">{{cite web |date=13 July 2006 |title=Planetary Satellite Physical Parameters |url=http://ssd.jpl.nasa.gov/?sat_phys_par |access-date=29 January 2008 |publisher=[[JPL]] (Solar System Dynamics) |archive-date=1 November 2013 |archive-url=https://web.archive.org/web/20131101144111/http://ssd.jpl.nasa.gov/?sat_phys_par |url-status=live }}</ref><ref>{{cite web |date=12 January 2004 |title=Phobos |url=http://www.bbc.co.uk/science/space/solarsystem/mars/phobos.shtml |url-status=dead |archive-url=https://web.archive.org/web/20090422160500/http://www.bbc.co.uk/science/space/solarsystem/mars/phobos.shtml |archive-date=22 April 2009 |access-date=19 July 2021 |work=[[BBC Online]]}}</ref> In particular, Phobos's surface has a very large [[Stickney (crater)|Stickney impact crater]] that is roughly {{convert|4.5|km|mi|abbr=on}} in radius.<ref>{{cite web |title=Stickney Crater-Phobos |url=http://www.solarviews.com/cap/mars/phobos2.htm |quote=One of the most striking features of Phobos, aside from its irregular shape, is its giant crater Stickney. Because Phobos is only {{Convert|28|by|20|km||sp=us}}, it must have been nearly shattered from the force of the impact that caused the giant crater. Grooves that extend across the surface from Stickney appear to be surface fractures caused by the impact. |access-date=21 April 2024 |archive-date=3 November 2011 |archive-url=https://web.archive.org/web/20111103010644/http://www.solarviews.com/cap/mars/phobos2.htm |url-status=live }}</ref>
** [[Deimos (moon)|Deimos]] is Mars's outer moon. Like Phobos, it is irregularly shaped, with a mean radius of {{convert|6|km|mi|abbr=on|sigfig=1}} and its surface reflects little light.<ref name="Horizons-Deimos" group="D">{{cite web |date=21 September 2013 |title=HORIZONS Web-Interface |url=http://ssd.jpl.nasa.gov/?horizons |access-date=4 December 2013 |publisher=NASA |archive-date=28 March 2007 |archive-url=https://web.archive.org/web/20070328180634/http://ssd.jpl.nasa.gov/?horizons |url-status=live }}</ref><ref name="JPLSSD" group="D">{{cite web |date=13 July 2006 |title=Planetary Satellite Physical Parameters |url=http://ssd.jpl.nasa.gov/?sat_phys_par |access-date=29 January 2008 |publisher=[[Jet Propulsion Laboratory]] (Solar System Dynamics) |archive-date=1 November 2013 |archive-url=https://web.archive.org/web/20131101144111/http://ssd.jpl.nasa.gov/?sat_phys_par |url-status=live }}</ref> However, the surface of Deimos is noticeably smoother than Phobos because the regolith partially covers the impact craters.<ref>{{Cite web |date=6 June 2023 |title=Deimos |url=https://www.britannica.com/place/Deimos-moon-of-Mars |access-date=21 April 2024 |website=Britannica |language=en |quote=It thus appears smoother than Phobos because its craters lie partially buried under this loose material. |archive-date=12 November 2018 |archive-url=https://web.archive.org/web/20181112023547/https://www.britannica.com/place/Deimos-moon-of-Mars |url-status=live }}</ref>

===Asteroids===
{{Main|Asteroid}}
[[File:Inner solar system objects top view for wiki.png|right|thumb|alt=Asteroid populations depicted: near-Earth asteroids, Earth trojans, Mars trojans, main asteroid belt, Jupiter trojans, Jupiter Greeks, Jupiter Hilda's triangle|Overview of the inner Solar System up to Jupiter's orbit]]Asteroids, except for the largest, Ceres, are classified as [[small Solar System bodies]] and are composed mainly of [[carbon]]aceous, refractory rocky and metallic minerals, with some ice.<ref>{{Cite web |date=2006 |title=IAU Planet Definition Committee |url=http://www.iau.org/public_press/news/release/iau0601/newspaper |url-status=dead |archive-url=https://web.archive.org/web/20090603001603/http://www.iau.org/public_press/news/release/iau0601/newspaper |archive-date=3 June 2009 |access-date=1 March 2009 |publisher=International Astronomical Union}}</ref><ref>{{Cite web |title=Are Kuiper Belt Objects asteroids? Are large Kuiper Belt Objects planets? |url=http://curious.astro.cornell.edu/question.php?number=601 |url-status=dead |archive-url=https://web.archive.org/web/20090103110110/http://curious.astro.cornell.edu/question.php?number=601 |archive-date=3 January 2009 |access-date=1 March 2009 |publisher=[[Cornell University]]}}</ref> They range from a few meters to hundreds of kilometers in size. {{Visible anchor|Asteroid groups|text=Many asteroids are divided into [[asteroid group]]s and [[Asteroid family|families]]}} based on their orbital characteristics. Some [[Minor-planet moon|asteroids have natural satellites that orbit them]], that is, asteroids that orbit larger asteroids.<ref>{{Cite journal |last1=Snodgrass |first1=Colin |last2=Agarwal |first2=Jessica |last3=Combi |first3=Michael |last4=Fitzsimmons |first4=Alan |last5=Guilbert-Lepoutre |first5=Aurelie |last6=Hsieh |first6=Henry H. |last7=Hui |first7=Man-To |last8=Jehin |first8=Emmanuel |last9=Kelley |first9=Michael S. P. |last10=Knight |first10=Matthew M. |last11=Opitom |first11=Cyrielle |date=November 2017 |title=The Main Belt Comets and ice in the Solar System |url=http://link.springer.com/10.1007/s00159-017-0104-7 |url-status=live |journal=The Astronomy and Astrophysics Review |language=en |volume=25 |issue=1 |page=5 |arxiv=1709.05549 |bibcode=2017A&ARv..25....5S |doi=10.1007/s00159-017-0104-7 |issn=0935-4956 |s2cid=7683815 |archive-url=https://web.archive.org/web/20220420161227/https://idp.springer.com/favicon.ico |archive-date=20 April 2022 |access-date=9 March 2022}}</ref>
* [[List of Mercury-crossing minor planets|Mercury-crossing asteroids]] are those with [[perihelia]] within the orbit of Mercury. At least 362 are known to date, and include the closest objects to the Sun known in the Solar System.<ref name="JPLcrosserlist">[http://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=all;obj_kind=ast;obj_numbered=all;OBJ_field=0;ORB_field=0;c1_group=ORB;c1_item=Bi;c1_op=%3C;c1_value=0.3075;table_format=HTML;max_rows=200;format_option=comp;c_fields=BgBhBiBjBnBsChAcCq;.cgifields=format_option;.cgifields=ast_orbit_class;.cgifields=table_format;.cgifields=obj_kind;.cgifields=obj_group;.cgifields=obj_numbered;.cgifields=com_orbit_class&query=1&c_sort=BiA List of asteroids with q<0.3075 AU generated by the JPL Small-Body Database Search Engine] {{Webarchive|url=https://web.archive.org/web/20160303213657/http://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=all&obj_kind=ast&obj_numbered=all&OBJ_field=0&ORB_field=0&c1_group=ORB&c1_item=Bi&c1_op=%3C&c1_value=0.3075&table_format=HTML&max_rows=200&format_option=comp&c_fields=BgBhBiBjBnBsChAcCq&.cgifields=format_option&.cgifields=ast_orbit_class&.cgifields=table_format&.cgifields=obj_kind&.cgifields=obj_group&.cgifields=obj_numbered&.cgifields=com_orbit_class&query=1&c_sort=BiA |date=3 March 2016 }} Retrieved 30 May 2012</ref> No [[vulcanoid]]s, asteroids between the orbit of Mercury and the Sun, have been discovered.<ref>{{Cite journal |last1=Durda |first1=D .D. |last2=Stern |first2=S. A. |last3=Colwell |first3=W. B. |last4=Parker |first4=J. W. |last5=Levison |first5=H. F. |last6=Hassler |first6=D. M. |date=2004 |title=A New Observational Search for Vulcanoids in SOHO/LASCO Coronagraph Images |journal=[[Icarus (journal)|Icarus]] |volume=148 |issue=1 |pages=312–315 |bibcode=2000Icar..148..312D |doi=10.1006/icar.2000.6520}}</ref><ref name="Steffl2013">{{Cite journal |last1=Steffl |first1=A. J. |last2=Cunningham |first2=N. J. |last3=Shinn |first3=A. B. |last4=Stern |first4=S. A. |date=2013 |title=A Search for Vulcanoids with the STEREO Heliospheric Imager |journal=Icarus |volume=233 |issue=1 |pages=48–56 |arxiv=1301.3804 |bibcode=2013Icar..223...48S |doi=10.1016/j.icarus.2012.11.031 |s2cid=118612132}}</ref> As of 2024, one asteroid has been discovered to orbit completely within Venus's orbit, [[594913 ꞌAylóꞌchaxnim]].<ref>{{cite journal |last1=Bolin |first1=Bryce T. |last2=Ahumada |first2=T. |last3=van Dokkum |first3=P. |last4=Fremling |first4=C. |last5=Granvik |first5=M. |last6=Hardegree-Ullmann |first6=K. K. |last7=Harikane |first7=Y. |last8=Purdum |first8=J. N. |last9=Serabyn |first9=E. |last10=Southworth |first10=J. |last11=Zhai |first11=C. |date=November 2022 |title=The discovery and characterization of (594913) 'Ayló'chaxnim, a kilometre sized asteroid inside the orbit of Venus |url=https://academic.oup.com/mnrasl/article/517/1/L49/6665933 |journal=[[Monthly Notices of the Royal Astronomical Society Letters]] |volume=517 |issue=1 |pages=L49–L54 |arxiv=2208.07253 |bibcode=2022MNRAS.517L..49B |doi=10.1093/mnrasl/slac089 |access-date=1 October 2022 |doi-access=free |archive-date=1 October 2022 |archive-url=https://web.archive.org/web/20221001070557/https://academic.oup.com/mnrasl/article/517/1/L49/6665933 |url-status=live }}</ref>
* [[Venus-crossing asteroid]]s are those that cross the orbit of Venus. There are 2,809 as of 2015.<ref name=jpello/>
* [[near-Earth object|Near-Earth asteroids]] have orbits that approach relatively close to Earth's orbit,<ref name="MorbidelliAstIII">{{Cite book |last1=Morbidelli |first1=A. |last2=Bottke |first2=W.F. |last3=Froeschlé |first3=Ch. |last4=Michel |first4=P. |date=January 2002 |editor2-last=A. Cellino |editor3-last=P. Paolicchi |editor4-last=R.P. Binzel |chapter=Origin and Evolution of Near-Earth Objects |chapter-url=http://www.boulder.swri.edu/~bottke/Reprints/Morbidelli-etal_2002_AstIII_NEOs.pdf |url-status=live |title=Asteroids III |pages=409–422 |publisher=University of Arizona Press |bibcode=2002aste.book..409M |doi=10.2307/j.ctv1v7zdn4.33 |isbn=978-0-8165-2281-1 |archive-url=https://web.archive.org/web/20170809014123/http://www.boulder.swri.edu/~bottke/Reprints/Morbidelli-etal_2002_AstIII_NEOs.pdf |archive-date=9 August 2017 |access-date=30 August 2009 |editor=W.F. Bottke Jr.}}</ref> and some of them are [[potentially hazardous object]]s because they might collide with Earth in the future.<ref name="CNEOS-Basics">{{Cite web |title=NEO Basics – Potentially Hazardous Asteroids (PHAs) |url=https://cneos.jpl.nasa.gov/about/neo_groups.html |url-status=live |archive-url=https://web.archive.org/web/20211111141623/https://cneos.jpl.nasa.gov/about/neo_groups.html |archive-date=11 November 2021 |access-date=10 March 2022 |publisher=CNEOS NASA/JPL}}</ref><ref name="NEO-groups">{{cite web |last1=Baalke |first1=Ron |title=Near-Earth Object Groups |url=http://neo.jpl.nasa.gov/neo/groups.html |url-status=dead |archive-url=https://web.archive.org/web/20020202160655/http://neo.jpl.nasa.gov/neo/groups.html |archive-date=2 February 2002 |access-date=11 November 2016 |website=[[Jet Propulsion Laboratory]] |publisher=[[NASA]]}}</ref> There are over 37,000 known as of 2024.<ref name="neo-jpl-stats">{{cite web
  |title      = Discovery Statistics – Cumulative Totals
  |date       = December 30, 2024
  |publisher  = NASA/JPL CNEOS
  |url        = https://cneos.jpl.nasa.gov/stats/totals.html
  |access-date = January 1, 2025
  |url-status = live
  |archive-url = https://web.archive.org/web/20250101175111/https://cneos.jpl.nasa.gov/stats/totals.html
  |archive-date = January 1, 2025}}</ref> A number of solar-orbiting [[meteoroid]]s were large enough to be tracked in space before striking Earth. It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of Earth.<ref name="BROWN02">{{cite news |first=Richard |last=Monastersky |title=The Call of Catastrophes |work=Science News Online |date=March 1, 1997  |url=https://www.sciencenews.org/archive/call-catastrophes |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20040313165341/http://www.sciencenews.org/pages/sn_arc97/75th/rm_essay.htm |archive-date=March 13, 2004 }}</ref>
* [[Mars-crossing asteroids]] are those with perhihelia above 1.3&nbsp;AU which cross the orbit of Mars.<ref>{{cite journal|journal=Astronomy & Astrophysics|volume=391|pages=757–765|year=2002|doi=10.1051/0004-6361:20020834|title=Spectral properties of Mars-crossers and near-Earth objects|author=C. A. Angeli - D. Lazzaro|issue=2 }}</ref> As of 2024, NASA lists 26,182 confirmed Mars-crossing asteroids.<ref name=jpello>{{cite web|title=Small-Body Database Query|url=https://ssd.jpl.nasa.gov/tools/sbdb_query.html#!|work=NASA|accessdate=3 June 2024|archive-date=27 September 2021|archive-url=https://web.archive.org/web/20210927184129/https://ssd.jpl.nasa.gov/tools/sbdb_query.html#!|url-status=live}}</ref>

====Asteroid belt====
The [[asteroid belt]] occupies a torus-shaped region between 2.3 and {{val|3.3|u=AU}} from the Sun, which lies between the orbits of Mars and Jupiter. It is thought to be remnants from the Solar System's formation that failed to coalesce because of the gravitational interference of Jupiter.<ref>{{Cite journal |last1=Petit |first1=J.-M. |last2=Morbidelli |first2=A. |last3=Chambers |first3=J. |date=2001 |title=The Primordial Excitation and Clearing of the Asteroid Belt |url=http://www.gps.caltech.edu/classes/ge133/reading/asteroids.pdf |url-status=dead |journal=[[Icarus (journal)|Icarus]] |volume=153 |issue=2 |pages=338–347 |bibcode=2001Icar..153..338P |doi=10.1006/icar.2001.6702 |archive-url=https://web.archive.org/web/20070221085835/http://www.gps.caltech.edu/classes/ge133/reading/asteroids.pdf |archive-date=21 February 2007 |access-date=22 March 2007}}</ref> The asteroid belt contains tens of thousands, possibly millions, of objects over one kilometer in diameter.<ref>{{Cite journal |last1=Tedesco |first1=Edward F. |last2=Cellino |first2=Alberto |last3=Zappalá |first3=Vincenzo |date=June 2005 |title=The Statistical Asteroid Model. I. The Main-Belt Population for Diameters Greater than 1 Kilometer |journal=The Astronomical Journal |language=en |volume=129 |issue=6 |pages=2869–2886 |bibcode=2005AJ....129.2869T |doi=10.1086/429734 |issn=0004-6256 |s2cid=119906696 |doi-access=free}}</ref> Despite this, the total mass of the asteroid belt is unlikely to be more than a thousandth of that of Earth.<ref name="Krasinsky2002">{{Cite journal |last1=Krasinsky |first1=G. A. |author-link=Georgij A. Krasinsky |last2=Pitjeva |first2=E. V. |author-link2=Elena V. Pitjeva |last3=Vasilyev |first3=M. V. |last4=Yagudina |first4=E. I. |date=July 2002 |title=Hidden Mass in the Asteroid Belt |journal=[[Icarus (journal)|Icarus]] |volume=158 |issue=1 |pages=98–105 |bibcode=2002Icar..158...98K |doi=10.1006/icar.2002.6837}}</ref> The asteroid belt is very sparsely populated; spacecraft routinely pass through without incident.<ref>{{Cite web |date=14 April 2000 |title=Cassini Passes Through Asteroid Belt |url=https://solarsystem.nasa.gov/news/12195/cassini-passes-through-asteroid-belt |url-status=live |archive-url=https://web.archive.org/web/20210125180703/https://solarsystem.nasa.gov/news/12195/cassini-passes-through-asteroid-belt |archive-date=25 January 2021 |access-date=1 March 2021 |website=NASA}}</ref>
[[File:The Four Largest Asteroids.jpg|thumb|The four largest asteroids: [[Ceres (dwarf planet)|Ceres]], [[4 Vesta|Vesta]], [[2 Pallas|Pallas]], [[10 Hygiea|Hygiea]]. Only Ceres and Vesta have been visited by a spacecraft and thus have a detailed picture.]]
Below are the descriptions of the three largest bodies in the asteroid belt. They are all considered to be relatively intact [[protoplanet]]s, a precursor stage before becoming a fully-formed planet (see [[List of exceptional asteroids]]):<ref>{{Cite journal |last1=McCord |first1=Thomas B. |last2=McFadden |first2=Lucy A. |last3=Russell |first3=Christopher T. |last4=Sotin |first4=Christophe |last5=Thomas |first5=Peter C. |date=7 March 2006 |title=Ceres, Vesta, and Pallas: Protoplanets, Not Asteroids |url=https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006EO100002 |url-status=live |journal=Eos |volume=87 |page=105 |bibcode=2006EOSTr..87..105M |doi=10.1029/2006EO100002 |archive-url=https://web.archive.org/web/20210928160233/https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006EO100002 |archive-date=28 September 2021 |access-date=12 September 2021 |number=10}}</ref><ref name="nasa-dawn20110329">{{cite web |author=Cook, Jia-Rui C. |date=29 March 2011 |title=When Is an Asteroid Not an Asteroid? |url=http://www.nasa.gov/mission_pages/dawn/news/dawn20110329.html |url-status=live |archive-url=https://web.archive.org/web/20110629163004/http://www.nasa.gov/mission_pages/dawn/news/dawn20110329.html |archive-date=29 June 2011 <!--DASHBot--> |access-date=30 July 2011 |publisher=NASA/JPL}}</ref><ref name="Marsset2020">{{Cite journal |last1=Marsset |first1=M. |last2=Brož |first2=M. |last3=Vernazza |first3=P. |last4=Drouard |first4=A. |display-authors=3 |date=2020 |title=The violent collisional history of aqueously evolved (2) Pallas |url=https://orbi.uliege.be/bitstream/2268/246670/1/Pallas_Marsset.pdf |journal=Nature Astronomy |volume=4 |issue=6 |pages=569–576 |bibcode=2020NatAs...4..569M |doi=10.1038/s41550-019-1007-5 |s2cid=212927521 |hdl-access=free |hdl=10261/237549 |access-date=4 January 2023 |archive-date=7 January 2023 |archive-url=https://web.archive.org/web/20230107085352/https://orbi.uliege.be/bitstream/2268/246670/1/Pallas_Marsset.pdf |url-status=live }}</ref>
* {{Visible anchor|Ceres|text=[[Ceres (dwarf planet)|Ceres]]}} (2.55–2.98&nbsp;AU) is the only dwarf planet in the asteroid belt.<ref name="IAU-QA">{{Cite web |title=Question and answers 2 |url=https://www.iau.org/public/themes/pluto/ |url-status=live |archive-url=https://web.archive.org/web/20160130022141/http://www.iau.org/public/themes/pluto/ |archive-date=30 January 2016 |access-date=31 January 2008 |publisher=IAU |quote=Ceres is (or now we can say it was) the largest asteroid{{spaces}}... There are many other asteroids that can come close to the orbital path of Ceres.}}</ref> It is the largest object in the belt, with a diameter of {{Convert|940|km|abbr=on}}.<ref name="Ermakov2017">{{cite journal |last1=Ermakov |first1=A. I. |last2=Fu |first2=R. R. |last3=Castillo-Rogez |first3=J. C. |last4=Raymond |first4=C. A. |last5=Park |first5=R. S. |last6=Preusker |first6=F. |last7=Russell |first7=C. T. |last8=Smith |first8=D. E. |last9=Zuber |first9=M. T. |date=November 2017 |title=Constraints on Ceres' Internal Structure and Evolution From Its Shape and Gravity Measured by the Dawn Spacecraft |journal=Journal of Geophysical Research: Planets |volume=122 |issue=11 |pages=2267–2293 |bibcode=2017JGRE..122.2267E |doi=10.1002/2017JE005302 |s2cid=133739176 |doi-access=free}}</ref> Its surface contains a mixture of [[carbon]],<ref name="Nature 12 2018">{{Cite journal |last1=Marchi |first1=S. |last2=Raponi |first2=A. |last3=Prettyman |first3=T. H. |last4=De Sanctis |first4=M. C. |last5=Castillo-Rogez |first5=J. |last6=Raymond |first6=C. A. |last7=Ammannito |first7=E. |last8=Bowling |first8=T. |last9=Ciarniello |first9=M. |last10=Kaplan |first10=H. |last11=Palomba |first11=E. |last12=Russell |first12=C. T. |last13=Vinogradoff |first13=V. |last14=Yamashita |first14=N. |year=2018 |title=An aqueously altered carbon-rich Ceres |journal=[[Nature Astronomy]] |volume=3 |issue=2 |pages=140–145 |doi=10.1038/s41550-018-0656-0 |s2cid=135013590}}</ref> frozen water and [[hydrate]]d minerals.<ref name="EPSC2">{{Cite book |last1=Raymond |first1=C. |title=European Planetary Science Congress |last2=Castillo-Rogez |first2=J. C. |last3=Park |first3=R. S. |last4=Ermakov |first4=A. |last5=Bland |first5=M. T. |last6=Marchi |first6=S. |last7=Prettyman |first7=T. |last8=Ammannito |first8=E. |last9=De Sanctis |first9=M. C. |date=September 2018 |volume=12 |chapter=Dawn Data Reveal Ceres' Complex Crustal Evolution |display-authors=4 |access-date=19 July 2020 |chapter-url=https://meetingorganizer.copernicus.org/EPSC2018/EPSC2018-645-1.pdf |archive-url=https://web.archive.org/web/20200130111631/https://meetingorganizer.copernicus.org/EPSC2018/EPSC2018-645-1.pdf |archive-date=30 January 2020 |url-status=live |author10=Russell, C.T.}}</ref> There are signs of past [[cryovolcano|cryovolcanic]] activity, where [[volatile (astrogeology)|volatile]] material such as water are erupted onto the surface, as seen in [[Bright spots on Ceres|surface bright spots]].<ref>{{cite web |last1=Krummheuer |first1=Birgit |date=6 March 2017 |title=Cryovolcanism on Dwarf Planet Ceres |url=http://www.mps.mpg.de/Cryovolcanism-on-Dwarf-Planet-Ceres |website=Max Planck Institute for Solar System Research |access-date=22 April 2024 |archive-date=2 February 2024 |archive-url=https://web.archive.org/web/20240202180118/https://www.mps.mpg.de/Cryovolcanism-on-Dwarf-Planet-Ceres |url-status=live }}</ref> Ceres has a very thin water vapor atmosphere, but practically speaking it is indistinguishable from a vacuum.<ref>{{Cite news |date=6 April 2017 |title=Confirmed: Ceres Has a Transient Atmosphere |url=https://www.universetoday.com/134922/confirmed-ceres-transient-atmosphere/ |url-status=live |archive-url=https://web.archive.org/web/20170415103956/https://www.universetoday.com/134922/confirmed-ceres-transient-atmosphere/ |archive-date=15 April 2017 |access-date=14 April 2017 |work=Universe Today |language=en}}</ref>
* {{Visible anchor|Pallas and Vesta|text=[[4 Vesta|Vesta]]}} (2.13–3.41&nbsp;AU) is the second-largest object in the asteroid belt.<ref name="Astronomy & Astrophysics">{{Cite report |url=https://meetingorganizer.copernicus.org/EPSC2022/EPSC2022-103.html |title=VLT/SPHERE imaging survey of D>100 km asteroids: Final results and synthesis |last1=Vernazza |first1=Pierre |last2=Ferrais |first2=Marin |date=6 July 2022 |publisher=Astronomy & Astrophysics |doi=10.5194/epsc2022-103 |page=A56 |last3=Jorda |first3=Laurent |last4=Hanus |first4=Josef |last5=Carry |first5=Benoit |last6=Marsset |first6=Michael |last7=Brož |first7=Miroslav |last8=Fetick |first8=Roman |last9=HARISSA team |doi-access=free |access-date=22 April 2024 |archive-date=22 April 2024 |archive-url=https://web.archive.org/web/20240422145344/https://meetingorganizer.copernicus.org/EPSC2022/EPSC2022-103.html |url-status=live }}</ref> Its fragments survive as the [[Vesta family|Vesta asteroid family]]<ref name="planetarysociety" /> and numerous [[HED meteorite]]s found on Earth.<ref name="Vestainterior">{{cite web |date=6 January 2011 |title=A look into Vesta's interior |url=https://www.mpg.de/877913/Vesta_asteroid |work=Max-Planck-Gesellschaft |access-date=22 April 2024 |archive-date=5 March 2023 |archive-url=https://web.archive.org/web/20230305200352/https://www.mpg.de/877913/Vesta_asteroid |url-status=live }}</ref> Vesta's surface, dominated by [[basalt]]ic and [[Metamorphic rock|metamorphic]] material, has a denser composition than Ceres's.<ref name="Takeda1997">{{cite journal |author=Takeda, H. |date=1997 |title=Mineralogical records of early planetary processes on the HED parent body with reference to Vesta |journal=Meteoritics & Planetary Science |volume=32 |issue=6 |pages=841–853 |bibcode=1997M&PS...32..841T |doi=10.1111/j.1945-5100.1997.tb01574.x |doi-access=free}}</ref> Its surface is marked by two giant craters: [[Rheasilvia]] and [[Veneneia (crater)|Veneneia]].<ref name="Schenk2012">{{cite journal |author=Schenk, P. |display-authors=etal |date=2012 |title=The Geologically Recent Giant Impact Basins at Vesta's South Pole |journal=Science |volume=336 |issue=6082 |pages=694–697 |bibcode=2012Sci...336..694S |doi=10.1126/science.1223272 |pmid=22582256 |s2cid=206541950}}</ref>
* [[2 Pallas|Pallas]] (2.15–2.57&nbsp;AU) is the third-largest object in the asteroid belt.<ref name="Astronomy & Astrophysics"/> It has its own [[Pallas family|Pallas]] [[Vesta family|asteroid family]].<ref name="planetarysociety">{{Cite web |last=Lakdawalla |first=Emily |author-link=Emily Lakdawalla |display-authors=etal |date=21 April 2020 |title=What Is A Planet? |url=https://www.planetary.org/worlds/what-is-a-planet |url-status=live |archive-url=https://web.archive.org/web/20220122142140/https://www.planetary.org/worlds/what-is-a-planet |archive-date=22 January 2022 |access-date=3 April 2022 |website=The Planetary Society}}</ref> Not much is known about Pallas because it has never been visited by a spacecraft,<ref>{{cite web |title=Athena: A SmallSat Mission to (2) Pallas |url=https://josephgorourke.com/research |url-status=dead |archive-url=https://web.archive.org/web/20211121181742/https://josephgorourke.com/research |archive-date=21 November 2021 |access-date=7 October 2020}}</ref> though its surface is predicted to be composed of silicates.<ref name="AutoCB-19">{{cite journal |author=Feierberg, M. A. |author2=Larson, H. P. |author3=Lebofsky, L. A. |date=1982 |title=The 3 Micron Spectrum of Asteroid 2 Pallas |journal=Bulletin of the American Astronomical Society |volume=14 |page=719 |bibcode=1982BAAS...14..719F}}</ref>

[[Hilda asteroid]]s are in a 3:2 resonance with Jupiter; that is, they go around the Sun three times for every two Jovian orbits.<ref name="Barucci">{{Cite book |last1=Barucci |first1=M. A. |title=Asteroids III |last2=Kruikshank |first2=D. P. |last3=Mottola |first3=S. |last4=Lazzarin |first4=M. |date=2002 |publisher=University of Arizona Press |location=Tucson, Arizona |pages=273–287 |chapter=Physical Properties of Trojan and Centaur Asteroids}}</ref> They lie in three linked clusters between Jupiter and the main asteroid belt.

[[Trojan (celestial body)|Trojan]]s are bodies located within another body's gravitationally stable [[Lagrangian point|Lagrange points]]: {{L4}}, 60° ahead in its orbit, or {{L5}}, 60° behind in its orbit.<ref name="spies">{{cite web |title=Trojan Asteroids |url=http://astronomy.swin.edu.au/cosmos/T/Trojan+Asteroids |url-status=live |archive-url=https://web.archive.org/web/20170623182748/http://astronomy.swin.edu.au/cosmos/T/Trojan+Asteroids |archive-date=23 June 2017 |access-date=13 June 2017 |website=Cosmos |publisher=Swinburne University of Technology}}</ref> Every planet except Mercury and Saturn is known to possess at least 1 trojan.<ref name="Connors">{{cite journal |last1= Connors|first1= Martin|last2= Wiegert|first2= Paul|last3= Veillet|first3= Christian|title= Earth's Trojan asteroid|date= 27 July 2011|journal= [[Nature (journal)|Nature]]|volume= 475|pages= 481–483|doi= 10.1038/nature10233|issue= 7357|bibcode= 2011Natur.475..481C|pmid= 21796207|s2cid= 205225571}}</ref><ref name=secondUranus>{{cite journal
|last2=de la Fuente Marcos |first2=Raúl
|last1=de la Fuente Marcos |first1=Carlos
|title=Asteroid 2014 YX<sub>49</sub>: a large transient Trojan of Uranus
|journal=Monthly Notices of the Royal Astronomical Society
|date=21 May 2017
|volume=467 |issue=2
|arxiv=1701.05541
|doi=10.1093/mnras/stx197 |pages=1561–1568|doi-access=free
|bibcode=2017MNRAS.467.1561D}}</ref><ref name=CeresVestatrojans>{{cite journal |first1=Apostolos A. |last1=Christou |first2=Paul |last2=Wiegert |title=A population of main belt asteroids co-orbiting with Ceres and Vesta |journal=Icarus |volume=217 |issue=1 |date=January 2012 |pages=27–42 |arxiv=1110.4810 |doi=10.1016/j.icarus.2011.10.016|bibcode=2012Icar..217...27C |s2cid=59474402 }}</ref> The [[Jupiter trojan]] population is roughly equal to that of the asteroid belt.<ref name="Yoshida2005">{{cite journal |last1=Yoshida |first1=Fumi |last2=Nakamura |first2=Tsuko |title=Size distribution of faint L4 Trojan asteroids |year=2005 |journal=The Astronomical Journal |volume=130 |issue=6 |pages=2900–11 |doi=10.1086/497571 |bibcode=2005AJ....130.2900Y|doi-access=free }}</ref> After Jupiter, Neptune possesses the most confirmed trojans, at 28.<ref>{{cite web |title=List of Neptune Trojans |work=Minor Planet Center |date=28 October 2018 |access-date=28 December 2018 |url=http://www.minorplanetcenter.org/iau/lists/NeptuneTrojans.html |archive-date=25 May 2012 |archive-url=https://archive.today/20120525133119/http://www.minorplanetcenter.org/iau/lists/NeptuneTrojans.html |url-status=live }}</ref>