Editing Water (section)

==Distribution in nature==

===In the universe===
[[File:Band 5 ALMA receiver.jpg|thumb|Band 5 [[Atacama Large Millimeter Array|ALMA]] receiver is an instrument specifically designed to detect water in the universe.<ref>{{cite web |title=ALMA Greatly Improves Capacity to Search for Water in Universe |url=http://www.eso.org/public/announcements/ann15059/ |access-date=20 July 2015 |archive-url=https://web.archive.org/web/20150723070436/http://www.eso.org/public/announcements/ann15059/ |archive-date=23 July 2015 |url-status=live }}</ref>]]

Much of the universe's water is produced as a byproduct of [[star formation]]. The formation of stars is accompanied by a strong outward wind of gas and dust. When this outflow of material eventually impacts the surrounding gas, the shock waves that are created compress and heat the gas. The water observed is quickly produced in this warm dense gas.<ref>Melnick, Gary, [[Harvard-Smithsonian Center for Astrophysics]] and Neufeld, David, [[Johns Hopkins University]] quoted in:
{{cite web |url=http://www.news.harvard.edu/gazette/1998/04.23/DiscoverofWater.html |title=Discover of Water Vapor Near Orion Nebula Suggests Possible Origin of H20 in Solar System (sic) |date=23 April 1998 |website=The Harvard University Gazette |url-status=dead |archive-url=https://web.archive.org/web/20000116054013/http://www.news.harvard.edu/gazette/1998/04.23/DiscoverofWater.html |archive-date=16 January 2000 }}
{{cite news |url=http://www.jhu.edu/news_info/news/home98/apr98/clouds.html |title=Space Cloud Holds Enough Water to Fill Earth's Oceans 1 Million Times |date=9 April 1998 |publisher=Headlines@Hopkins, JHU |access-date=21 April 2007 |archive-url=https://web.archive.org/web/20071109171410/http://www.jhu.edu/news_info/news/home98/apr98/clouds.html |archive-date=9 November 2007 |url-status=live }}
{{cite web |url=http://news.harvard.edu/gazette/1999/02.25/telescope.html |title=Water, Water Everywhere: Radio telescope finds water is common in universe |date=25 February 1999 |website=The Harvard University Gazette |access-date=19 September 2010 |archive-url=https://web.archive.org/web/20110519141432/http://news.harvard.edu/gazette/1999/02.25/telescope.html |archive-date=19 May 2011 |url-status=live }} ([https://web.archive.org/web/20160715053715/http://news.harvard.edu/gazette/1998/04.23/DiscoverofWater.html archive link])</ref>

On 22 July 2011, a report described the discovery of a gigantic cloud of water vapor containing "140 trillion times more water than all of Earth's oceans combined" around a [[quasar]] located 12 billion light years from Earth. According to the researchers, the "discovery shows that water has been prevalent in the universe for nearly its entire existence".<ref name="Clavin">{{cite web |last1=Clavin |first1=Whitney |last2=Buis |first2=Alan |title=Astronomers Find Largest, Most Distant Reservoir of Water |url=http://www.nasa.gov/topics/universe/features/universe20110722.html |date=22 July 2011 |publisher=[[NASA]] |access-date=25 July 2011 |archive-url=https://web.archive.org/web/20110724063244/http://www.nasa.gov/topics/universe/features/universe20110722.html |archive-date=24 July 2011 |url-status=live }}</ref><ref name="water vapor cloud">{{cite web |author=Staff |title=Astronomers Find Largest, Oldest Mass of Water in Universe |url=http://www.space.com/12400-universe-biggest-oldest-cloud-water.html |date=22 July 2011 |publisher=[[Space.com]] |access-date=23 July 2011 |archive-url=https://web.archive.org/web/20111029230319/http://www.space.com/12400-universe-biggest-oldest-cloud-water.html |archive-date=29 October 2011 |url-status=live }}</ref>

Water has been detected in [[interstellar cloud]]s within the [[Milky Way]].<ref>{{Cite book |url=https://books.google.com/books?id=m1gfe459yygC&pg=PA90 |title=Faint Echoes, Distant Stars: The Science and Politics of Finding Life Beyond Earth |last=Bova |first=Ben |year=2009 |publisher=Zondervan |isbn=978-0-06-185448-4 |access-date=31 August 2020 |archive-date=14 April 2021 |archive-url=https://web.archive.org/web/20210414164517/https://books.google.com/books?id=m1gfe459yygC&pg=PA90 |url-status=live }}</ref> Water probably exists in abundance in other galaxies, too, because its components, hydrogen, and oxygen, are among the most abundant elements in the universe. Based on models of the [[formation and evolution of the Solar System]] and that of other star systems, most other [[planetary system]]s are likely to have similar ingredients.

====Water vapor====
Water is present as vapor in:
* [[Solar atmosphere|Atmosphere of the Sun]]: in detectable trace amounts<ref name=Solanki1994>{{cite journal |last1=Solanki |first1=S.K. |last2=Livingston |first2=W. |last3=Ayres |first3=T. |year=1994 |title=New Light on the Heart of Darkness of the Solar Chromosphere |journal=[[Science (journal)|Science]] |pmid=17748350 |volume=263 |issue=5143 |pages=64–66 |bibcode=1994Sci...263...64S |doi=10.1126/science.263.5143.64 |s2cid=27696504 |url=http://pdfs.semanticscholar.org/f20e/89b9c386ff2dea7d990f8ff6a09d550e5e43.pdf |archive-url=https://web.archive.org/web/20190307030222/http://pdfs.semanticscholar.org/f20e/89b9c386ff2dea7d990f8ff6a09d550e5e43.pdf |url-status=dead |archive-date=7 March 2019 }}</ref>
* [[Atmosphere of Mercury]]: 3.4%, and large amounts of water in [[Mercury (planet)|Mercury's]] [[exosphere]]<ref name="planetary society">{{cite web |url=http://www.planetary.org/news/2008/0703_MESSENGER_Scientists_Astonished_to.html |title=MESSENGER Scientists 'Astonished' to Find Water in Mercury's Thin Atmosphere |access-date=5 July 2008 |publisher=Planetary Society |date=3 July 2008 |archive-url=https://web.archive.org/web/20100406034624/http://www.planetary.org/news/2008/0703_MESSENGER_Scientists_Astonished_to.html |url-status=dead |archive-date=6 April 2010}}</ref>
* [[Atmosphere of Venus]]: 0.002%<ref name=Bertaux2007>{{cite journal |last=Bertaux |first=Jean-Loup |title=A warm layer in Venus' cryosphere and high-altitude measurements of HF, HCl, H2O and HDO |journal=Nature |year=2007 |volume=450 |pages=646–649 |doi=10.1038/nature05974 |bibcode=2007Natur.450..646B |pmid=18046397 |issue=7170 |author2=Vandaele, Ann-Carine |last3=Korablev |first3=Oleg |last4=Villard |first4=E. |last5=Fedorova |first5=A. |last6=Fussen |first6=D. |last7=Quémerais |first7=E. |last8=Belyaev |first8=D. |last9=Mahieux |first9=A. |hdl=2268/29200 |s2cid=4421875 |url=https://orbi.uliege.be/bitstream/2268/29200/1/Bertaux-2007-a%20warm.pdf |access-date=8 October 2022 |archive-date=7 September 2022 |archive-url=https://web.archive.org/web/20220907122145/https://orbi.uliege.be/bitstream/2268/29200/1/Bertaux-2007-a%20warm.pdf |url-status=live }}</ref>
* [[Earth's atmosphere]]: ≈0.40% over full atmosphere, typically 1–4% at surface
* [[Atmosphere of the Moon]]: in trace amounts<ref name="Sridharan2010">{{cite journal |last1=Sridharan |first1=R. |first2=S.M. |last2=Ahmed |first3=Tirtha Pratim |last3=Dasa |first4=P. |last4=Sreelathaa |first5=P. |last5=Pradeepkumara |first6=Neha |last6=Naika |first7=Gogulapati |last7=Supriya |year=2010 |page=947 |issue=6 |volume=58 |title='Direct' evidence for water (H2O) in the sunlit lunar ambience from CHACE on MIP of Chandrayaan I |journal=Planetary and Space Science |doi=10.1016/j.pss.2010.02.013 |bibcode=2010P&SS...58..947S}}</ref>
* [[Atmosphere of Mars]]: 0.03%<ref name="Rapp2012">{{cite book |author=Rapp, Donald |title=Use of Extraterrestrial Resources for Human Space Missions to Moon or Mars |url=https://books.google.com/books?id=2xzxhnBRHCMC&pg=PA78 |year=2012 |publisher=Springer |isbn=978-3-642-32762-9 |page=78 |access-date=9 February 2016 |archive-url=https://web.archive.org/web/20160715154349/https://books.google.com/books?id=2xzxhnBRHCMC&pg=PA78 |archive-date=15 July 2016 |url-status=live }}</ref>
* [[Atmosphere of Ceres]]<ref name="Kuppers2014">{{cite journal |last1=Küppers |first1=M. |last2=O'Rourke |first2=L. |last3=Bockelée-Morvan |first3=D.|author3-link=Dominique Bockelée-Morvan |last4=Zakharov |first4=V. |last5=Lee |first5=S. |last6=Von Allmen |first6=P. |last7=Carry |first7=B. |last8=Teyssier |first8=D. |last9=Marston |first9=A. |last10=Müller |first10=T. |last11=Crovisier |first11=J. |last12=Barucci |first12=M.A. |last13=Moreno |first13=R. |title=Localized sources of water vapour on the dwarf planet (1) Ceres |journal=Nature |volume=505 |issue=7484 |date=23 January 2014 |pages=525–527|doi=10.1038/nature12918 |pmid=24451541 |bibcode=2014Natur.505..525K|s2cid=4448395 }}</ref>
* [[Atmosphere of Jupiter]]: 0.0004%<ref>{{cite journal |doi=10.1007/s11214-005-1951-5 |last1=Atreya |first1=Sushil K. |last2=Wong |first2=Ah-San |year=2005 |title=Coupled Clouds and Chemistry of the Giant Planets&nbsp;– A Case for Multiprobes |journal=Space Science Reviews |volume=116 |issue=1–2 |pages=121–136 |url=http://www-personal.umich.edu/~atreya/Chapters/2005_JovianCloud_Multiprobes.pdf |bibcode=2005SSRv..116..121A |access-date=1 April 2014 |archive-url=https://web.archive.org/web/20110722074717/http://www-personal.umich.edu/~atreya/Chapters/2005_JovianCloud_Multiprobes.pdf |archive-date=22 July 2011 |url-status=live |hdl=2027.42/43766 |s2cid=31037195 |hdl-access=free }}</ref> – in [[Volatile (astrogeology)|ices]] only; and that of its moon [[Europa (moon)|Europa]]<ref name="NASA-20131212-EU">{{cite web |last1=Cook |first1=Jia-Rui C. |last2=Gutro |first2=Rob |last3=Brown |first3=Dwayne |last4=Harrington |first4=J.D. |last5=Fohn |first5=Joe |title=Hubble Sees Evidence of Water Vapor at Jupiter Moon |url=http://www.jpl.nasa.gov/news/news.php?release=2013-363 |date=12 December 2013 |website=[[NASA]] |access-date=12 December 2013 |archive-url=https://web.archive.org/web/20131215053143/http://www.jpl.nasa.gov/news/news.php?release=2013-363 |archive-date=15 December 2013 |url-status=live}}</ref>
* [[Atmosphere of Saturn]] – in [[Volatile (astrogeology)|ices]] only; [[Enceladus (moon)|Enceladus]]: 91%<ref name="Hansen">{{cite journal |doi=10.1126/science.1121254 |title=Enceladus' Water Vapor Plume |year=2006 |author=Hansen |journal=Science |volume=311 |pages=1422–1425 |pmid=16527971 |issue=5766 |bibcode=2006Sci...311.1422H |author2=C.J.|last3=Stewart |first3=AI |last4=Colwell |first4=J |last5=Hendrix |first5=A |last6=Pryor |first6=W |last7=Shemansky |first7=D |last8=West |first8=R|s2cid=2954801 |url=https://pdfs.semanticscholar.org/89b1/1f34539a1b9b8a9dcb5a1d835e693bea1940.pdf |archive-url=https://web.archive.org/web/20200218132849/https://pdfs.semanticscholar.org/89b1/1f34539a1b9b8a9dcb5a1d835e693bea1940.pdf |url-status=dead |archive-date=18 February 2020 }}</ref> and [[Dione (moon)|Dione]] (exosphere){{Citation needed|date=May 2018}}
* [[Atmosphere of Uranus]] – in trace amounts below 50 bar
* [[Atmosphere of Neptune]] – found in the deeper layers<ref name=hubbard>{{cite journal |last=Hubbard |first=W.B. |title=Neptune's Deep Chemistry |journal=Science |year=1997 |volume=275 |issue=5304 |pages=1279–1280 |doi=10.1126/science.275.5304.1279 |pmid=9064785|s2cid=36248590 }}</ref>
* [[Extrasolar planet]] atmospheres: including those of [[HD 189733 b]]<ref>[http://www.time.com/time/health/article/0,8599,1642811,00.html Water Found on Distant Planet] {{Webarchive|url=https://web.archive.org/web/20070716081124/http://www.time.com/time/health/article/0,8599,1642811,00.html |date=16 July 2007 }} 12 July 2007 By Laura Blue, ''[[Time (magazine)|Time]]''</ref> and [[HD 209458 b]],<ref name="Space.com water">[http://www.space.com/scienceastronomy/070410_water_exoplanet.html Water Found in Extrasolar Planet's Atmosphere] {{Webarchive|url=https://web.archive.org/web/20101230065702/http://www.space.com/scienceastronomy/070410_water_exoplanet.html |date=30 December 2010 }} – Space.com</ref> [[Tau Boötis b]],<ref>{{Cite journal |arxiv = 1402.0846|last1 = Lockwood|first1 = Alexandra C|title = Near-IR Direct Detection of Water Vapor in Tau Boo B|journal = The Astrophysical Journal|volume = 783|issue = 2|pages = L29|last2 = Johnson|first2 = John A|last3 = Bender|first3 = Chad F|last4 = Carr|first4 = John S|last5 = Barman|first5 = Travis|last6 = Richert|first6 = Alexander J.W.|last7 = Blake|first7 = Geoffrey A|year = 2014|doi = 10.1088/2041-8205/783/2/L29|bibcode = 2014ApJ...783L..29L|s2cid = 8463125}}</ref> [[HAT-P-11b]],<ref name="NASA-20140924">{{cite web |last1=Clavin |first1=Whitney |last2=Chou |first2=Felicia |last3=Weaver |first3=Donna |last4=Villard |first45=Ray |last5=Johnson |first5=Michele |title=NASA Telescopes Find Clear Skies and Water Vapor on Exoplanet |url=http://www.jpl.nasa.gov/news/news.php?release=2014-322&1 |date=24 September 2014 |website=[[NASA]] |access-date=24 September 2014 |archive-url=https://web.archive.org/web/20170114220647/http://www.jpl.nasa.gov/news/news.php?release=2014-322&1 |archive-date=14 January 2017 |url-status=live}}</ref><ref name="Hanslmeier2010">{{cite book |author=Arnold Hanslmeier |title=Water in the Universe |url=https://books.google.com/books?id=Mj5tSld5tjMC&pg=PA159 |year=2010 |publisher=Springer Science & Business Media |isbn=978-90-481-9984-6 |pages=159– |access-date=9 February 2016 |archive-url=https://web.archive.org/web/20160715031920/https://books.google.com/books?id=Mj5tSld5tjMC&pg=PA159 |archive-date=15 July 2016 |url-status=live }}</ref> [[XO-1b]], [[WASP-12b]], [[WASP-17b]], and [[WASP-19b]].<ref name="NASA-20131203">{{cite web |title=Hubble Traces Subtle Signals of Water on Hazy Worlds |url=http://www.nasa.gov/content/goddard/hubble-traces-subtle-signals-of-water-on-hazy-worlds/ |date=3 December 2013 |publisher=[[NASA]] |access-date=4 December 2013 |archive-url=https://web.archive.org/web/20131206012837/http://www.nasa.gov/content/goddard/hubble-traces-subtle-signals-of-water-on-hazy-worlds/ |archive-date=6 December 2013 |url-status=live}}</ref>
* [[Stellar atmosphere]]s: not limited to cooler stars and even detected in giant hot stars such as [[Betelgeuse]], [[Mu Cephei]], [[Antares]] and [[Arcturus]].<ref name="Hanslmeier2010" /><ref name="Lund Observatory">Andersson, Jonas (June 2012). [http://lup.lub.lu.se/luur/download?func=downloadFile&recordOId=2969749&fileOId=2969772 Water in stellar atmospheres "Is a novel picture required to explain the atmospheric behavior of water in red giant stars?"] {{Webarchive|url=https://web.archive.org/web/20150213133956/http://lup.lub.lu.se/luur/download?func=downloadFile&recordOId=2969749&fileOId=2969772 |date=13 February 2015 }} Lund Observatory, Lund University, Sweden</ref>
* [[Circumstellar disk]]s: including those of more than half of [[T Tauri star]]s such as [[AA Tauri]]<ref name="Hanslmeier2010" /> as well as [[TW Hydrae]],<ref>[http://www.nasa.gov/mission_pages/herschel/news/herschel20111020.html Herschel Finds Oceans of Water in Disk of Nearby Star] {{Webarchive|url=https://web.archive.org/web/20150219053556/http://www.nasa.gov/mission_pages/herschel/news/herschel20111020.html |date=19 February 2015 }}. Nasa.gov (20 October 2011). Retrieved on 28 September 2015.</ref><ref>{{Cite web|url=https://jpl.nasa.gov/|archiveurl=https://web.archive.org/web/20120604082809/http://www.jpl.nasa.gov/news/news.cfm?release=2011-327|url-status=dead|title=JPL|archivedate=4 June 2012|website=NASA Jet Propulsion Laboratory (JPL)}}</ref> [[IRC +10216]]<ref>Lloyd, Robin. ''"Water Vapor, Possible Comets, Found Orbiting Star"'', 11 July 2001, [http://www.space.com/searchforlife/swas_water_010711.html Space.com]. Retrieved 15 December 2006. {{webarchive |url=https://web.archive.org/web/20090523025818/http://www.space.com/searchforlife/swas_water_010711.html |date=23 May 2009 }}</ref> and [[APM 08279+5255]],<ref name="Clavin" /><ref name="water vapor cloud" /> [[VY Canis Majoris]] and [[S Persei]].<ref name="Lund Observatory" />

====Liquid water====
{{Further|List of largest lakes and seas in the Solar System|Extraterrestrial liquid water}}
Liquid water is present on Earth, covering 71% of its surface.<ref name="WSS" /> Liquid water is also occasionally present in small amounts [[Water on Mars|on Mars]].<ref>{{cite web |title=NASA Confirms Evidence That Liquid Water Flows on Today's Mars |url=https://www.nasa.gov/press-release/nasa-confirms-evidence-that-liquid-water-flows-on-today-s-mars |website=NASA |access-date=22 June 2020 |date=28 September 2015 |archive-date=28 September 2015 |archive-url=https://archive.today/20150928154622/http://www.nasa.gov/press-release/nasa-confirms-evidence-that-liquid-water-flows-on-today-s-mars/ |url-status=live }}</ref> Scientists believe liquid water is present in the Saturnian moons of [[Enceladus (moon)|Enceladus]], as a 10-kilometre thick ocean approximately 30–40 kilometers below Enceladus' south polar surface,<ref name="NASA-20140403">{{cite web |last1=Platt |first1=Jane |last2=Bell |first2=Brian |title=NASA Space Assets Detect Ocean inside Saturn Moon |url=http://www.jpl.nasa.gov/news/news.php?release=2014-103 |date=3 April 2014 |website=[[NASA]] |access-date=3 April 2014 |archive-url=https://web.archive.org/web/20140403235224/http://www.jpl.nasa.gov/news/news.php?release=2014-103 |archive-date=3 April 2014 |url-status=live}}</ref><ref name="SCI-20140404">{{cite journal |last1=Iess |first1=L. |last2=Stevenson |first2=D. J. |last3=Parisi |first3=M. |last4=Hemingway |first4=D. |last5=Jacobson |first5=R.A. |last6=Lunine |first6=Jonathan I. |last7=Nimmo |first7=F. |last8=Armstrong |first8=J. W. |last9=Asmar |first9=S. W. |last10=Ducci |first10=M. |last11=Tortora |first11=P. |title=The Gravity Field and Interior Structure of Enceladus |date=4 April 2014 |journal=[[Science (journal)|Science]] |volume=344 |number=6179 |pages=78–80 |doi=10.1126/science.1250551 |bibcode=2014Sci...344...78I |pmid=24700854|s2cid=28990283 |url=https://authors.library.caltech.edu/45462/7/Iess-SM.pdf |access-date=14 July 2019 |archive-url=https://web.archive.org/web/20171202120709/https://authors.library.caltech.edu/45462/7/Iess-SM.pdf |archive-date=2 December 2017 |url-status=live }}</ref> and [[Titan (moon)|Titan]], as a subsurface layer, possibly mixed with [[ammonia]].<ref>{{Cite journal |url=http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2454.pdf |bibcode=2013LPI....44.2454D |author1=Dunaeva, A.N. |author2=Kronrod, V.A. |author3=Kuskov, O.L. |title=Numerical Models of Titan's Interior with Subsurface Ocean |journal=44th Lunar and Planetary Science Conference (2013) |issue=1719 |page=2454 |year=2013 |access-date=23 March 2014 |archive-url=https://web.archive.org/web/20140323033113/http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2454.pdf |archive-date=23 March 2014 |url-status=live}}</ref> Jupiter's moon [[Europa (moon)|Europa]] has surface characteristics which suggest a subsurface liquid water ocean.<ref>{{cite web |url=http://people.msoe.edu/~tritt/sf/europa.life.html |title=Possibility of Life on Europa |last=Tritt |first=Charles S. |access-date=10 August 2007 |publisher=Milwaukee School of Engineering |date=2002 |url-status=dead |archive-url=https://web.archive.org/web/20070609150109/http://people.msoe.edu/~tritt/sf/europa.life.html |archive-date=9 June 2007}}</ref> Liquid water may also exist on Jupiter's moon [[Ganymede (moon)|Ganymede]] as a layer sandwiched between high pressure ice and rock.<ref>Dunham, Will. (3 May 2014) [http://in.reuters.com/article/us-space-ganymede-idINKBN0DJ00H20140503 Jupiter's moon Ganymede may have 'club sandwich' layers of ocean | Reuters] {{Webarchive|url=https://web.archive.org/web/20140503100145/http://in.reuters.com/article/2014/05/03/us-space-ganymede-idINKBN0DJ00H20140503 |date=3 May 2014 }}. In.reuters.com. Retrieved on 28 September 2015.</ref>

====Water ice====
Water is present as ice on:
* [[File:Plan view of Korolev crater.jpg|thumb|Water ice in the [[Korolev (Martian crater)|Korolev]] crater on Mars]][[Water on Mars|Mars]]: under the regolith and at the poles.<ref>{{cite book |last=Carr |first=M.H. |date=1996 |title=Water on Mars |publisher=Oxford University Press |location=New York |page=197}}</ref><ref>{{cite journal |last1=Bibring |first1=J.-P. |last2=Langevin |first2=Yves |date=2004 |title=Perennial Water Ice Identified in the South Polar Cap of Mars |journal=Nature |volume=428 |issue=6983 |pages=627–630 |doi=10.1038/nature02461|pmid=15024393 |last3=Poulet |first3=François |last4=Gendrin |first4=Aline |last5=Gondet |first5=Brigitte |last6=Berthé |first6=Michel |last7=Soufflot |first7=Alain |last8=Drossart |first8=Pierre |last9=Combes |first9=Michel |last10=Bellucci |first10=Giancarlo |last11=Moroz |first11=Vassili |last12=Mangold |first12=Nicolas |last13=Schmitt |first13=Bernard |last14=Omega Team |first14=the|last15=Erard |first15=S. |last16=Forni |first16=O. |last17=Manaud |first17=N. |last18=Poulleau |first18=G. |last19=Encrenaz |first19=T.|author19-link=Thérèse Encrenaz |last20=Fouchet |first20=T. |last21=Melchiorri |first21=R. |last22=Altieri |first22=F. |last23=Formisano |first23=V. |last24=Bonello |first24=G. |last25=Fonti |first25=S. |last26=Capaccioni |first26=F. |last27=Cerroni |first27=P. |last28=Coradini |first28=A. |last29=Kottsov |first29=V. |last30=Ignatiev |first30=N. |bibcode=2004Natur.428..627B |s2cid=4373206 |url=https://hal.science/hal-03785230v1/file/bibring2004.pdf }}</ref>
* Earth–Moon system: mainly as [[ice sheet]]s on Earth and in Lunar craters and volcanic rocks<ref>[http://www.spiegel.de/wissenschaft/weltall/0,1518,564911,00.html Versteckt in Glasperlen: Auf dem Mond gibt es Wasser – Wissenschaft –] {{Webarchive|url=https://web.archive.org/web/20080710220126/http://www.spiegel.de/wissenschaft/weltall/0,1518,564911,00.html |date=10 July 2008 }} [[Der Spiegel]] – Nachrichten</ref> NASA reported the detection of water molecules by NASA's Moon Mineralogy Mapper aboard the Indian Space Research Organization's Chandrayaan-1 spacecraft in September 2009.<ref>[https://science.nasa.gov/headlines/y2009/24sep_moonwater.htm Water Molecules Found on the Moon] {{webarchive|url=https://web.archive.org/web/20090927092541/https://science.nasa.gov/headlines/y2009/24sep_moonwater.htm |date=27 September 2009 }}, NASA, 24 September 2009</ref>
* [[Ceres (dwarf planet)|Ceres]]<ref name="McCord2005-jgrp">{{cite journal |title=Ceres: Evolution and current state |journal=Journal of Geophysical Research: Planets |date=21 May 2005 |last1=McCord |first1=T.B. |last2=Sotin |first2=C. |volume=110 |issue=E5 |page=E05009 |doi=10.1029/2004JE002244 |bibcode=2005JGRE..110.5009M |doi-access=free |url=https://hal.archives-ouvertes.fr/hal-00116029/file/2004JE002244.pdf |access-date=5 March 2024 |archive-date=18 July 2021 |archive-url=https://web.archive.org/web/20210718171117/https://hal.archives-ouvertes.fr/hal-00116029/file/2004JE002244.pdf |url-status=live }}</ref><ref name="Thomas2005">{{cite journal |first1=P.C. |last1=Thomas |last2=Parker|first2=J.Wm.|last3=McFadden|first3= L.A. |title=Differentiation of the asteroid Ceres as revealed by its shape |year=2005 |journal=Nature |volume=437 |pages=224–226 |doi=10.1038/nature03938 |bibcode=2005Natur.437..224T |pmid=16148926 |issue=7056 |s2cid=17758979}}</ref><ref name="Carey2006">{{cite news|url=http://space.com/scienceastronomy/050907_ceres_planet.html |title=Largest Asteroid Might Contain More Fresh Water than Earth |first=Bjorn |last=Carey |publisher=SPACE.com |date=7 September 2005 |access-date=16 August 2006 |archive-url=https://web.archive.org/web/20101218180330/http://www.space.com/scienceastronomy/050907_ceres_planet.html |archive-date=18 December 2010 |url-status=live}}</ref>
* Jupiter's moons: [[Europa (moon)|Europa]]'s surface and also that of [[Ganymede (moon)|Ganymede]]<ref name="NYT-20150315">{{cite news |last=Chang |first=Kenneth |title=Suddenly, It Seems, Water Is Everywhere in Solar System |url=https://www.nytimes.com/2015/03/13/science/space/suddenly-it-seems-water-is-everywhere-in-solar-system.html |date=12 March 2015 |work=[[New York Times]] |access-date=12 March 2015 |archive-url=https://web.archive.org/web/20180812232556/https://www.nytimes.com/2015/03/13/science/space/suddenly-it-seems-water-is-everywhere-in-solar-system.html |archive-date=12 August 2018 |url-status=live}}</ref> and [[Callisto (moon)|Callisto]]<ref name=Kuskov2005>{{cite journal| last=Kuskov|first=O.L.|author2=Kronrod, V.A.|title=Internal structure of Europa and Callisto| year=2005|volume=177| issue=2|pages=550–369|doi=10.1016/j.icarus.2005.04.014| bibcode=2005Icar..177..550K| journal = Icarus}}</ref><ref name="Showman1999">{{cite journal|last1= Showman|first1=A. P.|last2= Malhotra|first2= R.|title=The Galilean Satellites|journal= Science|volume= 286|issue= 5437|date= 1 October 1999|pages =77–84|doi= 10.1126/science.286.5437.77|pmid=10506564|s2cid=9492520|url= http://pdfs.semanticscholar.org/3e6e/f125bbbafd779a0af6813ba0f5a18edea652.pdf|archive-url= https://web.archive.org/web/20200412142819/http://pdfs.semanticscholar.org/3e6e/f125bbbafd779a0af6813ba0f5a18edea652.pdf|url-status= dead|archive-date= 12 April 2020}}</ref>
* Saturn: in the [[Rings of Saturn|planet's ring system]]<ref name="Sparrow">{{cite book |last=Sparrow |first=Giles |title=The Solar System |publisher=Thunder Bay Press |year=2006 |isbn=978-1-59223-579-7}}</ref> and on the surface and mantle of [[Titan (moon)|Titan]]<ref name="Tobie">{{cite journal |last1=Tobie |first1=G. |last2=Grasset |first2=Olivier |last3=Lunine |first3=Jonathan I. |last4=Mocquet |first4=Antoine |last5=Sotin |first5=Christophe
|date=2005 |bibcode=2005Icar..175..496T |title=Titan's internal structure inferred from a coupled thermal-orbital model |journal=Icarus |volume=175 |issue=2 |pages=496–502 |doi=10.1016/j.icarus.2004.12.007 }}</ref> and [[Enceladus (moon)|Enceladus]]<ref name="Verbiscer et al. 2007">{{cite journal| doi = 10.1126/science.1134681| last1 = Verbiscer| first1 = A.| last2 = French| first2 = R.| last3 = Showalter| first3 = M.| last4 = Helfenstein| first4 = P.| title = Enceladus: Cosmic Graffiti Artist Caught in the Act| journal = Science| volume = 315| issue = 5813| page = 815| date = 9 February 2007| pmid = 17289992| bibcode = 2007Sci...315..815V| s2cid = 21932253| ref = {{sfnRef|Verbiscer French et al.|2007}}| df = dmy-all}} (supporting online material, table S1)</ref>
* [[Pluto]]–[[Charon (moon)|Charon]] system<ref name="Sparrow" />
* [[Comets]]<ref>{{cite journal |bibcode=1998A&A...330..375G |title=Making a comet nucleus |last1=Greenberg |first1=J. Mayo |volume=330 |date=1998 |page=375 |journal=Astronomy and Astrophysics}}</ref><ref>{{cite web |url=http://starryskies.com/solar_system/Comet/dirty_snowballs.html |title=Dirty Snowballs in Space |publisher=Starryskies |access-date=15 August 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130129035627/http://starryskies.com/solar_system/Comet/dirty_snowballs.html |archive-date=29 January 2013}}</ref> and other related [[Kuiper belt]] and [[Oort cloud]] objects<ref>{{cite journal |author=E.L. Gibb |author2=M.J. Mumma |author3=N. Dello Russo |author4=M.A. DiSanti |author5=K. Magee-Sauer |date=2003 |title=Methane in Oort Cloud comets |journal=[[Icarus (journal)|Icarus]] |volume=165 |issue=2 |pages=391–406 |bibcode=2003Icar..165..391G |doi=10.1016/S0019-1035(03)00201-X }}</ref>

And is also likely present on:
* [[Mercury (planet)|Mercury]]'s poles<ref>NASA, "[http://www.nasa.gov/mission_pages/messenger/media/PressConf20121129.html MESSENGER Finds New Evidence for Water Ice at Mercury's Poles] {{Webarchive|url=https://web.archive.org/web/20121130062257/http://www.nasa.gov/mission_pages/messenger/media/PressConf20121129.html |date=30 November 2012 }}", ''NASA'', 29 November 2012.</ref>
* [[Tethys (moon)|Tethys]]<ref>{{cite journal| doi = 10.1016/j.icarus.2007.03.012| last1 = Thomas| first1 = P.C.| last2 = Burns| first2 = J.A.| last3 = Helfenstein| first3 = P.| last4 = Squyres| first4 = S.| last5 = Veverka| first5 = J.| last6 = Porco| first6 = C.| last7 = Turtle| first7 = E.P.| last8 = McEwen| first8 = A.| last9 = Denk| first9 = T.| first10 = B.| last10 = Giesef| first11 = T.| last11 = Roatschf| first12 = T.V.| last12 = Johnsong| first13 = R.A.| last13 = Jacobsong| date = October 2007| title = Shapes of the saturnian icy satellites and their significance| journal = Icarus| volume = 190| issue = 2| pages = 573–584| bibcode = 2007Icar..190..573T| url = http://www.geoinf.fu-berlin.de/publications/denk/2007/ThomasEtAl_SaturnMoonsShapes_Icarus_2007.pdf| access-date = 15 December 2011| ref = {{sfnRef|Thomas Burns et al.|2007}}| archive-url = https://web.archive.org/web/20110927220431/http://www.geoinf.fu-berlin.de/publications/denk/2007/ThomasEtAl_SaturnMoonsShapes_Icarus_2007.pdf| archive-date = 27 September 2011| url-status=live| df = dmy-all}}</ref>

====Exotic forms====
Water and other [[Volatile (astrogeology)|volatiles]] probably comprise much of the internal structures of [[Uranus]] and [[Neptune]] and the water in the deeper layers may be in the form of [[ionic water]] in which the molecules break down into a soup of hydrogen and oxygen ions, and deeper still as [[superionic water]] in which the oxygen crystallizes, but the hydrogen ions float about freely within the oxygen lattice.<ref name="newscientist.com">[https://www.newscientist.com/article/mg20727764.500-weird-water-lurking-inside-giant-planets.html Weird water lurking inside giant planets] {{Webarchive|url=https://web.archive.org/web/20150415160045/http://www.newscientist.com/article/mg20727764.500-weird-water-lurking-inside-giant-planets.html |date=15 April 2015 }}, ''New Scientist'', 1 September 2010, Magazine issue 2776.</ref>

===Water and planetary habitability===
{{Further|Water distribution on Earth|Planetary habitability}}

The existence of liquid water, and to a lesser extent its gaseous and solid forms, on Earth are vital to the existence of [[Organism|life on Earth]] as we know it. The Earth is located in the [[habitable zone]] of the [[Solar System]]; if it were slightly closer to or farther from the [[Sun]] (about 5%, or about 8 million kilometers), the conditions which allow the three forms to be present simultaneously would be far less likely to exist.<ref>{{cite book |chapter=J.C.I. Dooge. "Integrated Management of Water Resources" |editor1=Ehlers, E. |editor2=Krafft, T |title=Understanding the Earth System: compartments, processes, and interactions |publisher=Springer |year=2001 |page=116}}</ref><ref>{{cite web |title=Habitable Zone |url=http://www.daviddarling.info/encyclopedia/H/habzone.html |website=The Encyclopedia of Astrobiology, Astronomy and Spaceflight |access-date=26 April 2007 |archive-url=https://web.archive.org/web/20070523143747/http://www.daviddarling.info/encyclopedia/H/habzone.html |archive-date=23 May 2007 |url-status=live }}</ref>

Earth's [[gravity]] allows it to hold an [[Celestial body atmosphere|atmosphere]]. Water vapor and carbon dioxide in the atmosphere provide a temperature buffer ([[greenhouse effect]]) which helps maintain a relatively steady surface temperature. If Earth were smaller, a thinner atmosphere would allow temperature extremes, thus preventing the accumulation of water except in [[polar ice cap]]s (as on [[Mars]]).{{Citation needed|date=May 2018}}

The surface temperature of Earth has been relatively constant through [[geologic time]] despite varying levels of incoming solar radiation ([[insolation]]), indicating that a dynamic process governs Earth's temperature via a combination of greenhouse gases and surface or atmospheric [[albedo]]. This proposal is known as the [[Gaia hypothesis]].{{Citation needed|date=May 2018}}

The state of water on a planet depends on ambient pressure, which is determined by the planet's gravity. If a planet is sufficiently massive, the water on it may be solid even at high temperatures, because of the high pressure caused by gravity, as it was observed on exoplanets [[Gliese 436 b]]<ref>{{cite news |magazine=New Scientist |url=https://www.newscientist.com/article/dn11864-strange-alien-world-made-of-hot-ice-and-steam.html |title=Strange alien world made of "hot ice" |date=6 May 2007 |first=David |last=Shiga |access-date=28 March 2010 |url-status=dead |archive-url=https://web.archive.org/web/20080706143705/http://space.newscientist.com/article/dn11864-strange-alien-world-made-of-hot-ice-and-steam.html |archive-date=6 July 2008}}</ref> and [[GJ 1214 b]].<ref>{{cite web |url=http://www.cfa.harvard.edu/news/2009/pr200924.html |title=Astronomers Find Super-Earth Using Amateur, Off-the-Shelf Technology |author=Aguilar, David A. |date=16 December 2009 |publisher=Harvard-Smithsonian Center for Astrophysics |access-date=28 March 2010 |archive-url=https://web.archive.org/web/20120407045343/http://www.cfa.harvard.edu/news/2009/pr200924.html |archive-date=7 April 2012 |url-status=live}}</ref>