Planetary oceanography#Natural satellites

{{Further|Extraterrestrial liquid water}}

File:PIA19656-SaturnMoon-Enceladus-Ocean-ArtConcept-20150915.jpg |volume=344 |number=6179 |pages=78–80 |doi=10.1126/science.1250551 |pmid=24700854|bibcode=2014Sci...344...78I |s2cid=28990283 |url=https://authors.library.caltech.edu/45462/7/Iess-SM.pdf }}]]

File:Europa_poster.svg

The gas giants, Jupiter and Saturn, are thought to lack surfaces and instead have a stratum of liquid hydrogen; however their planetary geology is not well understood. The possibility of the ice giants Uranus and Neptune having hot, highly compressed, supercritical water under their thick atmospheres has been hypothesised. Although their composition is still not fully understood, a 2006 study by Wiktorowicz and Ingersall ruled out the possibility of such a water "ocean" existing on Neptune,{{cite journal |last1=Wiktorowicz |first1=Sloane J. |last2=Ingersoll |first2=Andrew P. |title=Liquid water oceans in ice giants |journal=Icarus |volume=186 |issue=2 |date=2007 |pages=436–447 |issn=0019-1035 |doi=10.1016/j.icarus.2006.09.003 |arxiv=astro-ph/0609723 |bibcode=2007Icar..186..436W |s2cid=7829260 }} though oceans of metallic liquid carbon are possible.

The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, though the water on Mars is no longer oceanic (much of it residing in the ice caps). The possibility continues to be studied along with reasons for their apparent disappearance. Some astronomers now propose that Venus may have had liquid water and perhaps oceans for over 2 billion years. M. Way et al. "Was Venus the First Habitable World of Our Solar System?" Geophysical Research Letters, Vol. 43, Issue 16, pp. 8376-8383.

A global layer of liquid water thick enough to decouple the crust from the mantle is thought to be present on the natural satellites Titan, Europa, Enceladus, Ganymede,{{cite journal |title=The search for a subsurface ocean in Ganymede with Hubble Space Telescope observations of its auroral ovals |date=March 2015 |last1=Joachim |first1=Saur |last2=Duling |first2=Stefan |last3=Roth |first3=Lorenz |last4=Jia |first4=Xianzhe |display-authors=et al. |doi=10.1002/2014JA020778 |bibcode=2015JGRA..120.1715S |journal=Journal of Geophysical Research: Space Physics |volume=120 |issue=3 |pages=1715–1737|hdl=2027.42/111157 |hdl-access=free }}{{cite journal |title=Ganymede's internal structure including thermodynamics of magnesium sulfate oceans in contact with ice |journal=Planetary and Space Science |date=12 April 2014 |last1=Vance |first1=Steve |last2=Bouffard |first2=Mathieu |last3=Choukroun |first3=Mathieu |last4=Sotina |first4=Christophe |doi=10.1016/j.pss.2014.03.011 |bibcode=2014P&SS...96...62V |volume=96 |pages=62–70}} and Triton;{{Cite journal |doi=10.3390/rs13173476 |title=Triton: Topography and Geology of a Probable Ocean World with Comparison to Pluto and Charon |date=September 2021 |last1=Schenk | first1=Paul |last2=Beddingfield |first2=Chloe |last3=Bertrand |first3=Tanguy |display-authors=et al. |journal=Remote Sensing | volume=13 |issue=17 |pages=3476 |doi-access=free |bibcode=2021RemS...13.3476S }}{{cite journal |first=Javier |last=Ruiz |title=Heat flow and depth to a possible internal ocean on Triton |journal=Icarus |volume=166 |issue=2 |pages=436–439 |date=December 2003 |doi=10.1016/j.icarus.2003.09.009 |bibcode=2003Icar..166..436R |url=http://eprints.ucm.es/10454/1/11-Trit%C3%B3n_1.pdf }} and, with less certainty, in Callisto,{{cite journal |last1=Khurana|first1=K. K.|title=Induced magnetic fields as evidence for subsurface oceans in Europa and Callisto| journal=Nature| year=1998|volume=395|pages=777–780|doi=10.1038/27394| url=http://www.igpp.ucla.edu/people/mkivelson/Publications/N395777.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.igpp.ucla.edu/people/mkivelson/Publications/N395777.pdf |archive-date=2022-10-09 |url-status=live|pmid=9796812 | issue=6704| bibcode = 1998Natur.395..777K |last2=Kivelson|first2=M. G.| last3=Stevenson| first3=D. J.| last4=Schubert|first4=G.|last5=Russell|first5=C. T.|last6=Walker|first6=R. J.| last7=Polanskey| first7=C.|s2cid=4424606}}{{cite journal| last1=Zimmer| first1=C.|last2=Khurana, K. K.|title=Subsurface Oceans on Europa and Callisto: Constraints from Galileo Magnetometer Observations|journal=Icarus|year=2000|volume=147|issue=2|pages=329–347|doi=10.1006/icar.2000.6456| url=http://www.igpp.ucla.edu/people/mkivelson/Publications/ICRUS147329.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.igpp.ucla.edu/people/mkivelson/Publications/ICRUS147329.pdf |archive-date=2022-10-09 |url-status=live| bibcode=2000Icar..147..329Z| last3=Kivelson| first3=Margaret G.| citeseerx=10.1.1.366.7700}} Mimas,{{cite journal |last1=Lainey |first1=V. |last2=Rambaux |first2=N. |last3=Tobie |first3=G. |last4=Cooper |first4=N. |last5=Zhang |first5=Q. |last6=Noyelles |first6=B. |last7=Baillié |first7=K. |title=A recently formed ocean inside Saturn's moon Mimas |journal=Nature |date=February 2024 |volume=626 |issue=7998 |pages=280–282 |doi=10.1038/s41586-023-06975-9 |pmid=38326592 |bibcode=2024Natur.626..280L |url=https://www.nature.com/articles/s41586-023-06975-9 |access-date=9 February 2024 |language=en |issn=1476-4687}} Miranda, and Ariel.{{cite web |last1=Jeremy |first1=Rehm |title=Two of Uranus' Moons May Harbor Active Oceans, Radiation Data Suggests {{!}} Johns Hopkins University Applied Physics Laboratory |url=https://www.jhuapl.edu/news/news-releases/230316-radiation-around-uranus-suggests-it-has-ocean-moons |website=Johns Hopkins University Applied Physics Laboratory |publisher=Johns Hopkins University |access-date=9 February 2024 |archive-url=https://web.archive.org/web/20240128011057/https://www.jhuapl.edu/news/news-releases/230316-radiation-around-uranus-suggests-it-has-ocean-moons |archive-date=28 January 2024 |language=en |date=16 March 2023}} A magma ocean is thought to be present on Io.{{cite journal |last1=Khurana |first1=K. K. |last2=Jia |first2=X. |last3=Kivelson |first3=M. G. |last4=Nimmo |first4=F. |last5=Schubert |first5=G. |last6=Russell |first6=C. T. |title=Evidence of a Global Magma Ocean in Io's Interior |journal=Science |date=12 May 2011 |volume=332 |issue=6034 |pages=1186–1189 |doi=10.1126/science.1201425|pmid=21566160 |bibcode=2011Sci...332.1186K |s2cid=19389957 |doi-access=free }} Geysers or fumaroles have been found on Saturn's moon Enceladus, possibly originating from an ocean about {{convert|10|km|sp=us|sigfig=1}} beneath the surface ice shell.{{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 |work=NASA |date=2014-04-03 |access-date=2014-04-03 }} Other icy moons may also have internal oceans, or may once have had internal oceans that have now frozen.{{cite journal| doi = 10.1016/j.icarus.2006.06.005| last1 = Hussmann| first1 = Hauke| last2 = Sohl| first2 = Frank| last3 = Spohn| first3 = Tilman| date = November 2006| title = Subsurface oceans and deep interiors of medium-sized outer planet satellites and large trans-neptunian objects| journal = Icarus| volume = 185| issue = 1| pages = 258–273| url = https://www.researchgate.net/publication/225019299| bibcode = 2006Icar..185..258H| ref = {{sfnRef|Hussmann Sohl et al.|2006}}}}

Large bodies of liquid hydrocarbons are thought to be present on the surface of Titan, although they are not large enough to be considered oceans and are sometimes referred to as lakes or seas. The Cassini–Huygens space mission initially discovered only what appeared to be dry lakebeds and empty river channels, suggesting that Titan had lost what surface liquids it might have had. Later flybys of Titan provided radar and infrared images that showed a series of hydrocarbon lakes in the colder polar regions. Titan is thought to have a subsurface liquid-water ocean under the ice in addition to the hydrocarbon mix that forms atop its outer crust.

File:Ceres Cutaway-en.svg]]

Ceres appears to be differentiated into a rocky core and icy mantle and may harbour a liquid-water ocean under its surface.{{cite journal |last=McCord |first=Thomas B. |title=Ceres: Evolution and current state |journal=Journal of Geophysical Research |volume=110 |issue=E5 |page=E05009 |date=2005 |doi=10.1029/2004JE002244 |bibcode=2005JGRE..110.5009M |doi-access=free }}{{cite journal |last1=Castillo-Rogez |first1=J. C. |last2=McCord |first2=T. B. |last3=Davis |first3=A. G. |title=Ceres: evolution and present state |journal=Lunar and Planetary Science |volume=XXXVIII |pages=2006–2007 |date=2007 |url=http://www.lpi.usra.edu/meetings/lpsc2007/pdf/2006.pdf |access-date=2009-06-25 }}

Not enough is known of the larger trans-Neptunian objects to determine whether they are differentiated bodies capable of supporting oceans, although models of radioactive decay suggest that Pluto,{{cite web |title=The Inside Story |publisher=Johns Hopkins University Applied Physics Laboratory |work=pluto.jhuapl.edu — NASA New Horizons mission site |url=http://pluto.jhuapl.edu/science/everything_pluto/9_insideStory.php |date=2013 |access-date=2 August 2013 |url-status=dead |archive-url=https://web.archive.org/web/20141113225441/http://pluto.jhuapl.edu/science/everything_pluto/9_insideStory.php |archive-date=13 November 2014 }} Eris, Sedna, and Orcus have oceans beneath solid icy crusts approximately {{convert|100|to|180|km|sp=us|-1}} thick. In June 2020, astronomers reported evidence that the dwarf planet Pluto may have had a subsurface ocean, and consequently may have been habitable, when it was first formed.{{cite news |last=Rabie |first=Passant |title=New Evidence Suggests Something Strange and Surprising about Pluto - The findings will make scientists rethink the habitability of Kuiper Belt objects. |url=https://www.inverse.com/science/pluto-hot-star |date=22 June 2020 |work=Inverse |access-date=23 June 2020 }}{{cite journal |author=Bierson, Carver |display-authors=et al. |title=Evidence for a hot start and early ocean formation on Pluto |url=https://www.nature.com/articles/s41561-020-0595-0

|date=22 June 2020 |journal=Nature Geoscience |volume=769 |issue=7 |pages=468–472 |doi=10.1038/s41561-020-0595-0 |bibcode=2020NatGe..13..468B |s2cid=219976751 |access-date=23 June 2020 }}

File:UpsilonAndromedae D moons.jpg with surface liquid-water oceans]]

Some planets and natural satellites outside the Solar System are likely to have oceans, including possible water ocean planets similar to Earth in the habitable zone or "liquid-water belt". The detection of oceans, even through the spectroscopy method, however is likely extremely difficult and inconclusive.

Theoretical models have been used to predict with high probability that GJ 1214 b, detected by transit, is composed of exotic form of ice VII, making up 75% of its mass,{{cite web |url=http://www.cfa.harvard.edu/news/2009/pr200924.html |title=Astronomers Find Super-Earth Using Amateur, Off-the-Shelf Technology |first=David A. |last=Aguilar |date=2009-12-16 |publisher=Harvard-Smithsonian Center for Astrophysics |access-date=January 23, 2010 }}

making it an ocean planet.

Other possible candidates are merely speculative based on their mass and position in the habitable zone include planet though little is actually known of their composition. Some scientists speculate Kepler-22b may be an "ocean-like" planet.{{cite web |url=http://phl.upr.edu/library/notes/updatesonexoplanetsduringthefirstkeplerscienceconference |title=Updates on Exoplanets during the First Kepler Science Conference |date=2011-12-08 |first=Abel |last=Mendez Torres |publisher=Planetary Habitability Laboratory at UPR Arecibo }} Models have been proposed for Gliese 581 d that could include surface oceans. Gliese 436 b is speculated to have an ocean of "hot ice".{{cite news |url=https://www.reuters.com/article/us-space-planet-idUSN1621607620070516 |title=Hot "ice" may cover recently discovered planet |first=Maggie |last=Fox |work=Reuters |date=May 16, 2007 |access-date=May 18, 2012 }} Exomoons orbiting planets, particularly gas giants within their parent star's habitable zone may theoretically have surface oceans.

Terrestrial planets will acquire water during their accretion, some of which will be buried in the magma ocean but most of it will go into a steam atmosphere, and when the atmosphere cools it will collapse on to the surface forming an ocean. There will also be outgassing of water from the mantle as the magma solidifies—this will happen even for planets with a low percentage of their mass composed of water, so "super-Earth exoplanets may be expected to commonly produce water oceans within tens to hundreds of millions of years of their last major accretionary impact."{{cite journal |last=Elkins-Tanton |doi=10.1007/s10509-010-0535-3 |title=Formation of Early Water Oceans on Rocky Planets |date=2010 |journal=Astrophysics and Space Science |volume=332 |issue=2 |pages=359–364 |arxiv=1011.2710 |bibcode=2011Ap&SS.332..359E |s2cid=53476552 }}

Image:PIA17655 Kraken Mare crop no labels.jpg of Kraken Mare on Titan, the largest known body of surface liquid beside Earth's Ocean. The large island Mayda Insula is left of top center, and Jingpo Lacus is at upper left. A portion of Ligeia Mare enters the view at top right.]]

Oceans, seas, lakes and other bodies of liquids can be composed of liquids other than water, for example the hydrocarbon lakes on Titan. The possibility of seas of nitrogen on Triton was also considered but ruled out.{{cite encyclopedia |title=Encyclopedia of the Solar System |chapter=Triton |last1=McKinnon |first1=William B. |last2=Kirk |first2=Randolph L. |publisher=Academic Press |date=2007 |editor=Lucy Ann Adams McFadden |editor2=Lucy-Ann Adams |editor3=Paul Robert Weissman |editor4=Torrence V. Johnson |edition=2nd |location=Amsterdam; Boston |isbn=978-0-12-088589-3 |page=[https://archive.org/details/encyclopediaofso0000unse_u6d1/page/485 485] |chapter-url=https://archive.org/details/encyclopediaofso0000unse_u6d1/page/485 }} There is evidence that the icy surfaces of the moons Ganymede, Callisto, Europa, Titan and Enceladus are shells floating on oceans of very dense liquid water or water–ammonia solution.{{cite journal |bibcode=2008AGUFM.P21A1346C |date=2008 |page=1346 |volume=21 |title=The Titan Saturn System Mission |journal=American Geophysical Union, Fall Meeting |last1=Coustenis |first1=A. |display-authors=4 |last2=Lunine |first2=Jonathan I. |last3=Lebreton |first3=J. |last4=Matson |first4=D. |last5=Erd |first5=C. |last6=Reh |first6=K. |last7=Beauchamp |first7=P. |last8=Lorenz |first8=R. |last9=Waite |first9=H. |last10=Sotin |first10=C. |author11=Titan and Saturn System Mission (TSSM) Joint Science Definition Team (JSDT) |quote=the Titan system, rich in organics, containing a vast subsurface ocean of liquid water }}{{cite journal |doi=10.1016/j.icarus.2010.02.020 |journal=Icarus |volume=208 |issue=2 |date=2010 |pages=896–904 |title=Shell thickness variations and the long-wavelength topography of Titan |first1=F. |last1=Nimmo |first2=B. G. |last2=Bills |quote=observations can be explained if Titan has a floating, isostatically-compensated ice shell |bibcode=2010Icar..208..896N }}{{cite journal |arxiv=0910.0032 |title=Elastic ice shells of synchronous moons: Implications for cracks on Europa and non-synchronous rotation of Titan |first1=Peter M. |last1=Goldreich |first2=Jonathan L. |last2=Mitchell |doi=10.1016/j.icarus.2010.04.013 |journal=Icarus |volume=209 |issue=2 |date=2010 |pages=631–638 |quote=A number of synchronous moons are thought to harbor water oceans beneath their outer ice shells. A subsurface ocean frictionally decouples the shell from the interior |bibcode=2010Icar..209..631G |s2cid=119282970 }}{{cite web |url=http://meetingorganizer.copernicus.org/EPSC2009/EPSC2009-213.pdf |title=Study of the ice shells and possible subsurface oceans of the Galilean satellites using laser altimeters on board the Europa and Ganymede orbiters JEO and JGO |access-date=2011-10-14 }}{{cite web |url=http://www.pmc.ucsc.edu/~jhr/research/Roberts_Nimmo_2008_Icarus.pdf |title=Tidal heating and the long-term stability of a subsurface ocean on Enceladus |access-date=2011-10-14 |archive-date=2010-07-21 |archive-url=https://web.archive.org/web/20100721134758/http://www.pmc.ucsc.edu/~jhr/research/Roberts_Nimmo_2008_Icarus.pdf |url-status=dead }}

Extrasolar terrestrial planets that are extremely close to their parent star will be tidally locked and so one half of the planet will be a magma ocean.{{cite journal |arxiv=0906.1204 |title=Chemistry of Silicate Atmospheres of Evaporating Super-Earths |first1=Laura |last1=Schaefer|author1-link=Laura K. Schaefer |first2=Bruce Jr. |last2=Fegley |journal=The Astrophysical Journal Letters |date=2009 |volume=703 |issue=2 |pages=L113–L117 |doi=10.1088/0004-637X/703/2/L113 |bibcode=2009ApJ...703L.113S |s2cid=28361321 }} It is also possible that terrestrial planets had magma oceans at some point during their formation as a result of giant impacts.{{cite web |url=http://geophysics.nmsu.edu/slava/publications/OEM.pdf |title=Fluid Dynamics of a Terrestrial Magma Ocean |first=V. S. |last=Solomatov |date=2000 |access-date=2021-02-26 |archive-date=2012-03-24 |archive-url=https://web.archive.org/web/20120324155804/http://geophysics.nmsu.edu/slava/publications/OEM.pdf |url-status=dead }} Hot Neptunes close to their star could lose their atmospheres via hydrodynamic escape, leaving behind their cores with various liquids on the surface.{{cite conference |url=http://meetingorganizer.copernicus.org/EPSC2009/EPSC2009-542.pdf |title=Atmospheric Loss of Sub-Neptune's and Implications for Liquid Phases of Different Solvents on Their Surfaces |first1=J.J. |last1=Leitner |first2=H. |display-authors=4 |last2=Lammer |first3=P. |last3=Odert |first4=M. |last4=Leitzinger |first5=M.G. |last5=Firneis |first6=A. |last6=Hanslmeier |journal=EPSC Abstracts |volume=4 |id=EPSC2009-542 |date=2009 |page=542 |bibcode=2009epsc.conf..542L |conference=European Planetary Science Congress }} Where there are suitable temperatures and pressures, volatile chemicals that might exist as liquids in abundant quantities on planets (thalassogens) include ammonia, argon, carbon disulfide, ethane, hydrazine, hydrogen, hydrogen cyanide, hydrogen sulfide, methane, neon, nitrogen, nitric oxide, phosphine, silane, sulfuric acid, and water.Tables 3 and 4 in {{cite web |url=http://www.ifa.hawaii.edu/~meech/a281/handouts/Baines_astrobio04.pdf |title=Many Chemistries Could Be Used to Build Living Systems |first=William |last=Bains |work=Astrobiology |volume=4 |number=2 |date=2004 }}

Supercritical fluids, although not liquids, do share various properties with liquids. Underneath the thick atmospheres of the planets Uranus and Neptune, it is expected that these planets are composed of oceans of hot high-density fluid mixtures of water, ammonia and other volatiles.{{cite journal |url=http://www.cosis.net/abstracts/EGU06/05179/EGU06-J-05179-1.pdf |title=Water-ammonia ionic ocean on Uranus and Neptune? |first1=S. |last1=Atreya |first2=P. |last2=Egeler |first3=K. |last3=Baines |journal=Geophysical Research Abstracts |volume=8 |pages=P11A–0088 |date=2006 |bibcode=2005AGUFM.P11A0088A }} The gaseous outer layers of Jupiter and Saturn transition smoothly into oceans of supercritical hydrogen.{{cite journal |last=Guillot |first=T. |title=A comparison of the interiors of Jupiter and Saturn |journal=Planetary and Space Science |date=1999 |volume=47 |issue=10–11 |pages=1183–200 |bibcode=1999P&SS...47.1183G |arxiv=astro-ph/9907402 |doi=10.1016/S0032-0633(99)00043-4 |s2cid=19024073 |url=https://cds.cern.ch/record/394768/files/9907402.pdf }}{{cite web |last=Lang |first=Kenneth R. |date=2003 |url=http://ase.tufts.edu/cosmos/view_chapter.asp?id=9&page=3 |title=Jupiter: a giant primitive planet |publisher=NASA |access-date=2007-01-10 }} The atmosphere of Venus is 96.5% carbon dioxide, and is a supercritical fluid at the surface.

• Extraterrestrial liquid water
• Lava planet
• List of largest lakes and seas in the Solar System
• Magma ocean
• Ocean world

{{Reflist}}

{{Water}}

Category:Space science

Category:Oceanography

Category:Extraterrestrial water