Astrooceanography
Astrooceanography is the study of oceans outside planet Earth. Unlike other planetary sciences like astrobiology, astrochemistry and planetary geology, it only began after the discovery of underground oceans in Saturn's Titan[1] and Jupiter's Europa.[2] This field remains speculative until further missions reach the oceans beneath the rock or ice layer of the moons. There are many theories about oceans or even ocean worlds of celestial bodies in the Solar System, from oceans made of diamond in Neptune to a gigantic ocean of liquid hydrogen that may exist underneath Jupiter's surface.[3][4]
Early in their geologic histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, and a runaway greenhouse effect may have boiled away the global ocean of Venus. Compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many dwarf planets and natural satellites; notably, the ocean of the moon Europa is estimated to have over twice the water volume of Earth. The Solar System's giant planets are also thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of liquid water within a circumstellar habitable zone. Ocean planets are a hypothetical type of planet with a surface completely covered with liquid.[5][6]
Astrooceanography is closely related to Astrobiology, as oceans are expected to have higher chances to house simple forms of life.
Extraterrestrial water oceans[edit]
Planets[edit]
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,[9] though some studies have suggested that exotic oceans of liquid diamond are possible.[10]
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. Astronomers now think that Venus may have had liquid water and perhaps oceans for over 2 billion years. [11]
Natural satellites[edit]
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 and, with less certainty, Callisto, Ganymede[12][13] and Triton.[14][15] A magma ocean is thought to be present on Io.[16] Geysers have been found on Saturn's moon Enceladus, possibly originating from an ocean about 10 kilometers (6.2 mi) beneath the surface ice shell.[7] Other icy moons may also have internal oceans, or may once have had internal oceans that have now frozen.[17]
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.
Dwarf planets and trans-Neptunian objects[edit]
Ceres appears to be differentiated into a rocky core and icy mantle and may harbour a liquid-water ocean under its surface.[18][19]
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,[20] Eris, Sedna, and Orcus have oceans beneath solid icy crusts approximately 100 to 180 km thick.[17] 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.[21][22]
Extrasolar[edit]
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,[23] making it an ocean planet.
Other possible candidates are merely speculated 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.[24] 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".[25] 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."[26]
Non-water surface liquids[edit]
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.[27] 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.[28][29][30][31][32] Earth is often called the ocean planet because it is 70% covered in water.[33][34] 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.[35] It is also possible that terrestrial planets had magma oceans at some point during their formation as a result of giant impacts.[36] Hot Neptunes close to their star could lose their atmospheres via hydrodynamic escape, leaving behind their cores with various liquids on the surface.[37] Where there are suitable temperatures and pressures, volatile chemicals that might exist as liquids in abundant quantities on planets include ammonia, argon, carbon disulfide, ethane, hydrazine, hydrogen, hydrogen cyanide, hydrogen sulfide, methane, neon, nitrogen, nitric oxide, phosphine, silane, sulfuric acid, and water.[38]
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.[39] The gaseous outer layers of Jupiter and Saturn transition smoothly into oceans of supercritical hydrogen.[40][41] The atmosphere of Venus is 96.5% carbon dioxide, which is a supercritical fluid at its surface.
See also[edit]
References[edit]
- ↑ "Titan's Underground Ocean | Science Mission Directorate".
- ↑ "NASA discovers an underground ocean on Jupiter's largest moon".
- ↑ "10 Mind-Boggling Oceans That Exist in Space". 3 April 2015.
- ↑ "A Freaky Fluid inside Jupiter? | Science Mission Directorate".
- ↑ "Titan Likely To Have Huge Underground Ocean | Mind Blowing Science". Mindblowingscience.com. Retrieved 2012-11-08.
- ↑ "Ocean-bearing Planets: Looking For Extraterrestrial Life In All The Right Places". Sciencedaily.com. Retrieved 2012-11-08.
- ↑ 7.0 7.1 Platt, Jane; Bell, Brian (2014-04-03). "NASA Space Assets Detect Ocean inside Saturn Moon". NASA. Retrieved 2014-04-03.
- ↑ Iess, L.; Stevenson, D. J.; Parisi, M.; Hemingway, D.; et al. (4 April 2014). "The Gravity Field and Interior Structure of Enceladus" (PDF). Science. 344 (6179): 78–80. Bibcode:2014Sci...344...78I. doi:10.1126/science.1250551. PMID 24700854. Unknown parameter
|s2cid=ignored (help) - ↑ Wiktorowicz, Sloane J.; Ingersoll, Andrew P. (2007). "Liquid water oceans in ice giants". Icarus. 186 (2): 436–447. arXiv:astro-ph/0609723. Bibcode:2007Icar..186..436W. doi:10.1016/j.icarus.2006.09.003. ISSN 0019-1035. Unknown parameter
|s2cid=ignored (help) - ↑ Silvera, Isaac (2010). "Diamond: Molten under pressure" (PDF). Nature Physics. 6 (1): 9–10. Bibcode:2010NatPh...6....9S. doi:10.1038/nphys1491. ISSN 1745-2473.
- ↑ M. Way et al. "Was Venus the First Habitable World of Our Solar System?" Geophysical Research Letters, Vol. 43, Issue 16, pp. 8376-8383.
- ↑ Clavin, Whitney (May 1, 2014). "Ganymede May Harbor 'Club Sandwich' of Oceans and Ice". NASA. Jet Propulsion Laboratory. Retrieved 2014-05-01.
- ↑ Vance, Steve; Bouffard, Mathieu; Choukroun, Mathieu; Sotina, Christophe (12 April 2014). "Ganymede's internal structure including thermodynamics of magnesium sulfate oceans in contact with ice". Planetary and Space Science. 96: 62–70. Bibcode:2014P&SS...96...62V. doi:10.1016/j.pss.2014.03.011.
- ↑ McKinnon, William B.; Kirk, Randolph L. (2007). "Triton". In Lucy Ann Adams McFadden; Lucy-Ann Adams; Paul Robert Weissman; Torrence V. Johnson. Encyclopedia of the Solar System (2nd ed.). Amsterdam; Boston: Academic Press. pp. 483–502. ISBN 978-0-12-088589-3.
- ↑ Ruiz, Javier (December 2003). "Heat flow and depth to a possible internal ocean on Triton" (PDF). Icarus. 166 (2): 436–439. Bibcode:2003Icar..166..436R. doi:10.1016/j.icarus.2003.09.009.
- ↑ Khurana, K. K.; Jia, X.; Kivelson, M. G.; Nimmo, F.; Schubert, G.; Russell, C. T. (12 May 2011). "Evidence of a Global Magma Ocean in Io's Interior". Science. 332 (6034): 1186–1189. Bibcode:2011Sci...332.1186K. doi:10.1126/science.1201425. PMID 21566160. Unknown parameter
|s2cid=ignored (help) - ↑ 17.0 17.1 Hussmann, Hauke; Sohl, Frank; Spohn, Tilman (November 2006). "Subsurface oceans and deep interiors of medium-sized outer planet satellites and large trans-neptunian objects". Icarus. 185 (1): 258–273. Bibcode:2006Icar..185..258H. doi:10.1016/j.icarus.2006.06.005.
- ↑ McCord, Thomas B. (2005). "Ceres: Evolution and current state". Journal of Geophysical Research. 110 (E5): E05009. Bibcode:2005JGRE..11005009M. doi:10.1029/2004JE002244.
- ↑ Castillo-Rogez, J. C.; McCord, T. B.; Davis, A. G. (2007). "Ceres: evolution and present state" (PDF). Lunar and Planetary Science. XXXVIII: 2006–2007. Retrieved 2009-06-25.
- ↑ "The Inside Story". pluto.jhuapl.edu — NASA New Horizons mission site. Johns Hopkins University Applied Physics Laboratory. 2013. Archived from the original on 13 November 2014. Retrieved 2 August 2013. Unknown parameter
|url-status=ignored (help) - ↑ Rabie, Passant (22 June 2020). "New Evidence Suggests Something Strange and Surprising about Pluto - The findings will make scientists rethink the habitability of Kuiper Belt objects". Inverse. Retrieved 23 June 2020.
- ↑ Bierson, Carver; et al. (22 June 2020). "Evidence for a hot start and early ocean formation on Pluto". Nature Geoscience. 769 (7): 468–472. Bibcode:2020NatGe..13..468B. doi:10.1038/s41561-020-0595-0. Retrieved 23 June 2020. Unknown parameter
|s2cid=ignored (help) - ↑ Aguilar, David A. (2009-12-16). "Astronomers Find Super-Earth Using Amateur, Off-the-Shelf Technology". Harvard-Smithsonian Center for Astrophysics. Retrieved January 23, 2010.
- ↑ Mendez Torres, Abel (2011-12-08). "Updates on Exoplanets during the First Kepler Science Conference". Planetary Habitability Laboratory at UPR Arecibo.
- ↑ Fox, Maggie (May 16, 2007). "Hot "ice" may cover recently discovered planet". Reuters. Retrieved May 18, 2012.
- ↑ Elkins-Tanton (2010). "Formation of Early Water Oceans on Rocky Planets". Astrophysics and Space Science. 332 (2): 359–364. arXiv:1011.2710. Bibcode:2011Ap&SS.332..359E. doi:10.1007/s10509-010-0535-3. Unknown parameter
|s2cid=ignored (help) - ↑ McKinnon, William B.; Kirk, Randolph L. (2007). "Triton". In Lucy Ann Adams McFadden; Lucy-Ann Adams; Paul Robert Weissman; Torrence V. Johnson. Encyclopedia of the Solar System (2nd ed.). Amsterdam; Boston: Academic Press. p. 485. ISBN 978-0-12-088589-3.
- ↑ Coustenis, A.; Lunine, Jonathan I.; Lebreton, J.; Matson, D.; et al. (2008). "The Titan Saturn System Mission". American Geophysical Union, Fall Meeting. 21: 1346. Bibcode:2008AGUFM.P21A1346C.
the Titan system, rich in organics, containing a vast subsurface ocean of liquid water
- ↑ Nimmo, F.; Bills, B. G. (2010). "Shell thickness variations and the long-wavelength topography of Titan". Icarus. 208 (2): 896–904. Bibcode:2010Icar..208..896N. doi:10.1016/j.icarus.2010.02.020.
observations can be explained if Titan has a floating, isostatically-compensated ice shell
- ↑ Goldreich, Peter M.; Mitchell, Jonathan L. (2010). "Elastic ice shells of synchronous moons: Implications for cracks on Europa and non-synchronous rotation of Titan". Icarus. 209 (2): 631–638. arXiv:0910.0032. Bibcode:2010Icar..209..631G. doi:10.1016/j.icarus.2010.04.013.
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
Unknown parameter|s2cid=ignored (help) - ↑ "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" (PDF). Retrieved 2011-10-14.
- ↑ "Tidal heating and the long-term stability of a subsurface ocean on Enceladus" (PDF). Archived from the original (PDF) on 2010-07-21. Retrieved 2011-10-14. Unknown parameter
|url-status=ignored (help) - ↑ Hinrichsen, D (2011-10-03). "The ocean planet". People Planet. 7 (2): 6–9. PMID 12349465.
- ↑ "Irrigating Crops with Seawater". Scientific American. August 1998. Archived from the original on 2011-06-10. Retrieved 2014-03-16. Unknown parameter
|url-status=ignored (help) - ↑ Schaefer, Laura; Fegley, Bruce, Jr. (2009). "Chemistry of Silicate Atmospheres of Evaporating Super-Earths". The Astrophysical Journal Letters. 703 (2): L113–L117. arXiv:0906.1204. Bibcode:2009ApJ...703L.113S. doi:10.1088/0004-637X/703/2/L113. Unknown parameter
|s2cid=ignored (help) - ↑ Solomatov, V. S. (2000). "Fluid Dynamics of a Terrestrial Magma Ocean" (PDF). Archived from the original (PDF) on 2012-03-24. Retrieved 2021-02-26. Unknown parameter
|url-status=ignored (help) - ↑ Leitner, J.J.; Lammer, H.; Odert, P.; Leitzinger, M.; et al. (2009). Atmospheric Loss of Sub-Neptune's and Implications for Liquid Phases of Different Solvents on Their Surfaces (PDF). European Planetary Science Congress. EPSC Abstracts. 4. p. 542. Bibcode:2009epsc.conf..542L. EPSC2009-542.
- ↑ Tables 3 and 4 in Bains, William (2004). "Many Chemistries Could Be Used to Build Living Systems" (PDF). Astrobiology.
- ↑ Atreya, S.; Egeler, P.; Baines, K. (2006). "Water-ammonia ionic ocean on Uranus and Neptune?" (PDF). Geophysical Research Abstracts. 8: P11A–0088. Bibcode:2005AGUFM.P11A0088A.
- ↑ Guillot, T. (1999). "A comparison of the interiors of Jupiter and Saturn" (PDF). Planetary and Space Science. 47 (10–11): 1183–200. arXiv:astro-ph/9907402. Bibcode:1999P&SS...47.1183G. doi:10.1016/S0032-0633(99)00043-4. Unknown parameter
|s2cid=ignored (help) - ↑ Lang, Kenneth R. (2003). "Jupiter: a giant primitive planet". NASA. Retrieved 2007-01-10.
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