Mars ocean theory

Features shown by the Viking orbiters in 1976 revealed two possible ancient shorelines near the pole, Arabia and Deuteronilus, each thousands of kilometers long.{{cite news | author = Staff | title = Mars Probably Once Had A Huge Ocean | date = 13 June 2007 | work = Science Daily | url = https://www.sciencedaily.com/releases/2007/06/070613131912.htm |publisher = University of California, Berkeley | access-date = 2014-02-19}} Several physical features in the present geography of Mars suggest the past existence of a primordial ocean. Networks of gullies that merge into larger channels imply erosion by a liquid agent, and resemble ancient riverbeds on Earth. Enormous channels, 25 km wide and several hundred meters deep, appear to direct flow from underground aquifers in the Southern uplands into the Northern lowlands. Much of the northern hemisphere of Mars is located at a significantly lower elevation than the rest of the planet (the Martian dichotomy), and is unusually flat.

These observations led a number of researchers to look for remnants of more ancient coastlines and further raised the possibility that such an ocean once existed.{{cite news | title = Mars Ocean Hypothesis Hits the Shore | date = 26 January 2001 | url = http://www.astrobio.net/pressrelease/58/mars-ocean-hypothesis-hits-the-shore | work = Astrobiology Magazine | access-date = 19 February 2004 |archive-url=https://web.archive.org/web/20120211125813/http://astrobio.net/pressrelease/58/mars-ocean-hypothesis-hits-the-shore |archive-date=2012-02-11 |url-status=usurped}} In 1987, John E. Brandenburg published the hypothesis of a primordial Mars ocean he dubbed Paleo-Ocean. The ocean hypothesis is important because the existence of large bodies of liquid water in the past would have had a significant impact on ancient Martian climate, habitability potential and implications for the search for evidence of past life on Mars.

Beginning in 1998, scientists Michael Malin and Kenneth Edgett set out to investigate with higher-resolution cameras on board the Mars Global Surveyor with a resolution five to ten times better than those of the Viking spacecraft, in places that would test shorelines proposed by others in the scientific literature. Their analyses were inconclusive at best, and reported that the shoreline varies in elevation by several kilometers, rising and falling from one peak to the next for thousands of kilometers.{{cite journal | title=Oceans or Seas in the Martian Northern Lowlands: High Resolution Imaging Tests of Proposed Coastlines | author=Malin, M. C. | author2=Edgett, K. S. | journal=Geophys. Res. Lett. | year=1999 | volume=26 | issue=19 | pages=3049–3052 | doi=10.1029/1999GL002342| bibcode=1999GeoRL..26.3049M | url=http://www.msss.com/biographies/edgett/self_archived_papers/Malin_Edgett_GRL_1999_selfarchive.pdf | doi-access=free }} These trends cast doubt on whether the features truly mark a long-gone sea coast and, have been taken as an argument against the Martian shoreline (and ocean) hypothesis.

The Mars Orbiter Laser Altimeter (MOLA), which accurately determined in 1999 the altitude of all parts of Mars, found that the watershed for an ocean on Mars would cover three-quarters of the planet.{{cite journal|doi=10.1126/science.284.5419.1495|bibcode=1999Sci...284.1495S|title=The Global Topography of Mars and Implications for Surface Evolution|journal=Science|volume=284|issue=5419|pages=1495–1503|year=1999|last1=Smith|first1=D. E|pmid=10348732|s2cid=2978783}} The unique distribution of crater types below 2400 m elevation in the Vastitas Borealis was studied in 2005. The researchers suggest that erosion involved significant amounts of sublimation, and an ancient ocean at that location would have encompassed a volume of 6 x 10⁷ km³.{{Cite journal | last = Boyce | first = J. M. | author2 = Mouginis, P. | author3 = Garbeil, H. | title = Ancient oceans in the northern lowlands of Mars: Evidence from impact crater depth/diameter relationships | journal = Journal of Geophysical Research | volume = 110 | issue = E03008 | pages = 15 pp | date = 2005| url = http://www.agu.org/journals/ABS/2005/2004JE002328.shtml

| doi = 10.1029/2004JE002328 | access-date = 2 October 2010 |bibcode = 2005JGRE..110.3008B| doi-access = free }}

In 2007, Taylor Perron and Michael Manga proposed a geophysical model that, after adjustment for true polar wander caused by mass redistributions from volcanism, the Martian paleo-shorelines first proposed in 1987 by John E. Brandenburg, meet this criterion.{{cite journal | last1 = Zuber | first1 = Maria T | year = 2007 | title = Planetary Science: Mars at the tipping point | journal = Nature | volume = 447 | issue = 7146| pages = 785–786 | doi=10.1038/447785a | pmid=17568733| bibcode = 2007Natur.447..785Z| s2cid = 4427572 }} The model indicates that these undulating Martian shorelines can be explained by the movement of Mars's rotation axis. Because centrifugal force causes spinning objects and large rotating objects to bulge at their equator (equatorial bulge), the polar wander could have caused the shoreline elevation to shift in a similar way as observed.{{cite journal | title = Evidence for an ancient martian ocean in the topography of deformed shorelines | journal = Nature | date = 14 June 2007 | first = J. Taylor | last = Perron | author2 = Jerry X. Mitrovica | author3-link = Michael Manga | author3 = Michael Manga | author4 = Isamu Matsuyama | author5 = Mark A. Richards | name-list-style = amp | volume = 447 | issue = 7146 | pages = 840–843 | doi=10.1038/nature05873 | pmid=17568743| bibcode = 2007Natur.447..840P | s2cid = 4332594 }}{{cite news | first = Will | last = Dunham | title = Evidence seen backing ancient Mars ocean shoreline | date = 13 June 2007 | url = https://www.reuters.com/article/us-mars-oceans-idUSN1337096720070613 | work = Reuters | access-date = 2014-02-19}} Their model does not attempt to explain what caused Mars's rotation axis to move relative to the crust.

Research published in 2009 shows a much higher density of stream channels than formerly believed. Regions on Mars with the most valleys are comparable to what is found on the Earth. In the research, the team developed a computer program to identify valleys by searching for U-shaped structures in topographical data.{{cite news | title = Martian North Once Covered by Ocean | date = 26 November 2009 | url = http://www.astrobio.net/pressrelease/3322/martian-north-once-covered-by-ocean | work = Astrobiology Magazine | access-date = 19 February 2014 |archive-url=https://web.archive.org/web/20110604121418/http://www.astrobio.net/pressrelease/3322/martian-north-once-covered-by-ocean |archive-date=2011-06-04 |url-status=usurped}} The large amount of valley networks strongly supports rain on the planet in the past. The global pattern of the Martian valleys could be explained with a big northern ocean. A large ocean in the northern hemisphere would explain why there is a southern limit to valley networks; the southernmost regions of Mars, farthest from the water reservoir, would get little rainfall and would develop no valleys. In a similar fashion the lack of rainfall would explain why Martian valleys become shallower from north to south.{{cite news | author = Staff | title = New Map Bolsters Case for Ancient Ocean on Mars | date = 23 November 2009 | url = http://www.space.com/7584-map-bolsters-case-ancient-ocean-mars.html | work = Space.com | access-date = 2014-02-19}}

A 2010 study of deltas on Mars revealed that seventeen of them are found at the altitude of a proposed shoreline for a Martian ocean.{{cite journal | last1 = DiAchille | first1 = G | last2 = Hynek | first2 = B. | year = 2010 | title = Ancient ocean on Mars supported by global distribution of deltas and valleys. nat | journal = Nature Geoscience| volume = 3 | issue = 7| pages = 459–463 | doi = 10.1038/ngeo891 | bibcode=2010NatGe...3..459D}} This is what would be expected if the deltas were all next to a large body of water.{{cite journal | last1 = DiBiasse | last2 = Limaye | first2 = A. | last3 = Scheingross | first3 = J. | last4 = Fischer | first4 = W. | last5 = Lamb | first5 = M. | year = 2013 | title = Deltic deposits at Aeolis Dorsa: Sedimentary evidence for a standing body of water on the northern plains of Mars | url = https://authors.library.caltech.edu/39420/1/jgre20100.pdf| journal = Journal of Geophysical Research: Planets | volume = 118 | issue = 6| pages = 1285–1302 | doi = 10.1002/jgre.20100 | bibcode = 2013JGRE..118.1285D | doi-access = free }} Research presented at a Planetary Conference in Texas suggested that the Hypanis Valles fan complex is a delta with multiple channels and lobes, which formed at the margin of a large, standing body of water. That body of water was a northern ocean. This delta is at the dichotomy boundary between the northern lowlands and southern highlands near Chryse Planitia.Fawdon, P., et al. 2018. HYPANIS VALLES DELTA: THE LAST HIGH-STAND OF A SEA ON EARLY MARS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2839.pdf

Research published in 2012 using data from MARSIS, a radar on board the Mars Express orbiter, supports the hypothesis of an extinct large, northern ocean. The instrument revealed a dielectric constant of the surface that is similar to those of low-density sedimentary deposits, massive deposits of ground-ice, or a combination of the two. The measurements were not like those of a lava-rich surface.{{cite journal | last1 = Mouginot | first1 = J. | last2 = Pommerol | first2 = A. | last3 = Beck | first3 = P. | last4 = Kofman | first4 = W. | last5 = Clifford | first5 = S. | year = 2012 | title = Dielectric map of the Martian northern hemisphere and the nature of plain filling materials | url = https://boris.unibe.ch/18086/1/grl28854.pdf| journal = Geophysical Research Letters | volume = 39 | issue = 2| page = L02202 | doi = 10.1029/2011GL050286 | bibcode=2012GeoRL..39.2202M| doi-access = free }}

In March 2015, scientists stated that evidence exists for an ancient volume of water that could comprise an ocean, likely in the planet's northern hemisphere and about the size of Earth's Arctic Ocean.Villanueva G. L., Mumma M. J., Novak R. E., Käufl H. U., Hartogh P., Encrenaz T., Tokunaga A., Khayat A., and Smith M. D., Science, Published online 5 March 2015 [DOI:10.1126/science.aaa3630]Villanueva, G., et al. 2015. Strong water isotopic anomalies in the martian atmosphere: Probing current and ancient reservoirs. Science 10 Apr 2015:

Vol. 348, Issue 6231, pp. 218-221. This finding was derived from the ratio of water and deuterium in the modern Martian atmosphere compared to the ratio found on Earth and derived from telescopic observations. Eight times as much deuterium was inferred at the polar deposits of Mars than exists on Earth (VSMOW), suggesting that ancient Mars had significantly higher levels of water. The representative atmospheric value obtained from the maps (7 VSMOW) is not affected by climatological effects as those measured by localized rovers, although the telescopic measurements are within range to the enrichment measured by the Curiosity rover in Gale Crater of 5–7 VSMOW.{{cite journal | last1 = Webster | first1 = C.R. |display-authors=etal | year = 2013 | title = Isotope Ratios of H, C, and O in CO2 and H2O of the Martian Atmosphere | journal = Science | volume = 341 | issue = 6| pages = 260–263 | bibcode = 2013Sci...341..260W | doi = 10.1126/science.1237961 | pmid = 23869013 | s2cid = 206548962 | url = https://authors.library.caltech.edu/102999/ }} Even back in 2001, a study of the ratio of molecular hydrogen to deuterium in the upper atmosphere of Mars by the NASA Far Ultraviolet Spectroscopic Explorer spacecraft suggested an abundant water supply on primordial Mars.{{cite journal | last1 = Krasnopolsky | first1 = Vladimir A. | last2 = Feldman | first2 = Paul D. | year = 2001 | title = Detection of Molecular Hydrogen in the Atmosphere of Mars | journal = Science | volume = 294 | issue = 5548| pages = 1914–1917 | doi=10.1126/science.1065569 | pmid=11729314| bibcode = 2001Sci...294.1914K | s2cid = 25856765 }}

Further evidence that Mars once had a thicker atmosphere which would make an ocean more probable came from the MAVEN spacecraft that has been making measurements from Mars orbit. Bruce Jakosky, lead author of a paper published in Science, stated that "We've determined that most of the gas ever present in the Mars atmosphere has been lost to space."{{cite web | url=https://www.nasa.gov/press-release/nasas-maven-reveals-most-of-mars-atmosphere-was-lost-to-space | title=NASA's MAVEN Reveals Most of Mars' Atmosphere Was Lost to Space| date=2017-03-30}} This research was based upon two different isotopes of argon gas.{{cite journal | last1 = Jakosky | first1 = B.M. | display-authors = etal | year = 2017 | title = Mars' atmospheric history derived from upper-atmosphere measurements of 38Ar/36Ar | journal = Science | volume = 355 | issue = 6332| pages = 1408–1410 | doi = 10.1126/science.aai7721 | pmid = 28360326 | doi-access = free | bibcode = 2017Sci...355.1408J }}{{cite web | url=http://www.sci-news.com/space/maven-martian-atmosphere-lost-space-04750.html | title=MAVEN Finds New Evidence that Most of Martian Atmosphere Was Lost to Space | Planetary Science, Space Exploration | Sci-News.com| date=31 March 2017}}

For how long this body of water was in the liquid form is still unknown, considering the high greenhouse efficiency required to bring water to the liquid phase in Mars at a heliocentric distance of 1.4–1.7 AU. It is now thought that the canyons filled with water, and at the end of the Noachian Period the Martian ocean disappeared, and the surface froze for approximately 450 million years. Then, about 3.2 billion years ago, lava beneath the canyons heated the soil, melted the icy materials, and produced vast systems of subterranean rivers extending hundreds of kilometers. This water erupted onto the now-dry surface in giant floods.

New evidence for a vast northern ocean was published in May 2016. A large team of scientists described how some of the surface in Ismenius Lacus quadrangle was altered by two tsunamis. The tsunamis were caused by asteroids striking the ocean. Both were thought to have been strong enough to create 30 km diameter craters. The first tsunami picked up and carried boulders the size of cars or small houses. The backwash from the wave formed channels by rearranging the boulders. The second came in when the ocean was 300 m lower. The second carried a great deal of ice which was dropped in valleys. Calculations show that the average height of the waves would have been 50 m, but the heights would vary from 10 m to 120 m. Numerical simulations show that in this particular part of the ocean two impact craters of the size of 30 km in diameter would form every 30 million years. The implication here is that a great northern ocean may have existed for millions of years. One argument against an ocean has been the lack of shoreline features. These features may have been washed away by these tsunami events. The parts of Mars studied in this research are Chryse Planitia and northwestern Arabia Terra. These tsunamis affected some surfaces in the Ismenius Lacus quadrangle and in the Mare Acidalium quadrangle.{{cite web | url=http://astrobiology.com/2016/05/ancient-tsunami-evidence-on-mars-reveals-life-potential.html | title=Ancient Tsunami Evidence on Mars Reveals Life Potential - Astrobiology| date=20 May 2016}}{{cite journal | url=https://www.hou.usra.edu/meetings/lpsc2016/pdf/1680.pdf | title=Tsunami waves extensively resurfaced the shorelines of an early Martian ocean | author=Rodriguez, J. |display-authors=etal| journal= Scientific Reports| year=2016 | volume=6 | issue=1 | pages=25106 | doi=10.1038/srep25106| pmid=27196957 | pmc=4872529 | bibcode=2016NatSR...625106R }}[https://www.nature.com/articles/srep25106 version at Nature]Cornell University. [https://www.sciencedaily.com/releases/2016/05/160519101756.htm "Ancient tsunami evidence on Mars reveals life potential."] ScienceDaily. 19 May 2016. The impact that created the crater Lomonosov has been identified as a likely source of tsunami waves.{{Cite news | url = https://www.bbc.com/news/science-environment-39394583 | title = Impact crater linked to Martian tsunamis | last = Rincon | first = P. | date = 2017-03-26 | newspaper = BBC News | access-date = 2017-03-26}}{{cite conference | first1 = F. | last1 = Costard | first2 = A. | last2 = Séjourné | first3 = K. | last3 = Kelfoun | first4 = S. | last4 = Clifford | first5 = F. | last5 = Lavigne | first6 = I. | last6 = Di Pietro | first7 = S. | last7 = Bouley | title = Modelling Investigation of Tsunamis on Mars | book-title = Lunar and Planetary Science XLVIII | pages = 1171 | publisher = Lunar and Planetary Institute | date = 2017 | location = The Woodlands, Texas | url = http://www.lpi.usra.edu/meetings/lpsc2017/pdf/1171.pdf | access-date = 2017-03-26}}Costard, F., et al. 2018. FORMATION OF THE NORTHERN PLAINS LOMONOSOV CRATER DURING A TSUNAMI GENERATING MARINE IMPACT CRATER EVENT. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1928.pdf

ESP 028537 2270tsunamischannels.jpg|Channels made by the backwash from tsunamis, as seen by HiRISE. The tsunamis were probably caused by asteroids striking the ocean.

28537 2270tsunamisboulders.jpg|Boulders that were picked up, carried, and dropped by tsunamis, as seen by HiRISE. The boulders are between the size of cars and houses.

Tsunamisstreamlinedp20008931.jpg|Streamlined promontory eroded by tsunami, as seen by HiRISE.

Research reported in 2017 found that the amount of water needed to develop valley networks, outflow channels, and delta deposits of Mars was larger than the volume of a Martian ocean. The estimated volume of an ocean on Mars ranges from 3 meters to about 2 kilometers GEL (Global equivalent layer). This implies that a large amount of water was available on Mars.{{cite journal | url=https://www.hou.usra.edu/meetings/lpsc2017/pdf/1734.pdf | title=New Martian valley network volume estimate consistent with ancient ocean and warm and wet climate | author=Luo, W. |display-authors=etal| journal=Lunar and Planetary Science | year=2017 | volume=XLVIII | issue=1 | pages=15766 | doi=10.1038/ncomms15766 | pmid=28580943 |pmc=5465386| bibcode=2017NatCo...815766L }}

In 2018, a team of scientists proposed that Martian oceans appeared very early, before or along with the growth of Tharsis. Because of this the depth of the oceans would be only half as deep as had been thought. The full weight of Tharsis would have created deep basins, but if the ocean occurred before the mass of Tharsis had formed deep basins, much less water would be needed. Also, the shorelines would not be regular since Tharsis would still be growing and consequently changing the depth of the ocean's basin. As Tharsis volcanoes erupted they added huge amounts of gases into the atmosphere that created a global warming, thereby allowing liquid water to exist.[https://www.sciencedaily.com/releases/2018/03/180319124255.htm Mars' oceans formed early, possibly aided by massive volcanic eruptions]. University of California - Berkeley. March 19, 2018.{{cite journal | last1 = Citron | first1 = R. | last2 = Manga | first2 = M. | last3 = Hemingway | first3 = D. | year = 2018 | title = Timing of oceans on Mars from shoreline deformation | url = http://www.escholarship.org/uc/item/810840x9| journal = Nature | volume = 555| issue = 7698| pages = 643–646| doi = 10.1038/nature26144 | pmid = 29555993 | bibcode = 2018Natur.555..643C | s2cid = 4065379 }}Citro, R., et al. 2018. EVIDENCE OF EARLY MARTIAN OCEANS FROM SHORELINE DEFORMATION DUE TO THARSIS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1244.pdf

In July 2019, support was reported for an ancient ocean on Mars that may have been formed by a possible mega-tsunami source resulting from a meteorite impact creating Lomonosov crater.{{cite news |last=Andrews |first=Robin George|title=When a Mega-Tsunami Drowned Mars, This Spot May Have Been Ground Zero - The 75-mile-wide crater could be something like a Chicxulub crater for the red planet. |url=https://www.nytimes.com/2019/07/30/science/mars-tsunami-crater.html |date=30 July 2019 |work=The New York Times |access-date=31 July 2019 }}{{cite journal |author=Costard, F. |display-authors=et al. |title=The Lomonosov Crater Impact Event: A Possible Mega-Tsunami Source on Mars |date=26 June 2019 |journal=Journal of Geophysical Research: Planets |volume=124 |issue=7 |pages=1840–1851 |doi=10.1029/2019JE006008 |bibcode=2019JGRE..124.1840C |hdl=20.500.11937/76439 |s2cid=198401957 |hdl-access=free }}

In January 2022, a study about the climate 3 billion years ago on Mars shows that an ocean is stable with a water cycle that is closed.{{cite journal |last1=Schmidt |first1=Frédéric |last2=Way |first2=Michael|display-authors=et al.|title=Circumpolar ocean stability on Mars 3 Gy ago |journal=Proceedings of the National Academy of Sciences |date=2022 |volume=119 |issue=4 |doi=10.1073/pnas.2112930118 |doi-access=free |pmid=35042794 |pmc=8795497 |arxiv=2310.00461 |bibcode=2022PNAS..11912930S }} They estimate a return water flow, in form of ice in glacier, from the icy highlands to the ocean is in magnitude less than the Earth at the last glacial maximum. This simulation includes for the first time a circulation of the ocean. They demonstrate that the ocean's circulation prevent the ocean to freeze. These also shows that simulations are in agreement with observed geomorphological features identified as ancient glacial valleys.{{cn|date=August 2024}}

In a paper published by the Journal of Geophysical Research: Planets in 2022, Benjamin T. Cardenas and Michael P. Lamb asserted that evidence of accumulated sediment suggests Mars had a large, northern ocean in the distant past.{{cite journal |last1=Cardenas |first1=Benjamin T. |last2=Lamb |first2=Michael P. |title=Paleogeographic Reconstructions of an Ocean Margin on Mars Based on Deltaic Sedimentology at Aeolis Dorsa |journal=Journal of Geophysical Research: Planets |date=12 October 2022 |volume=127 |issue=10 |doi=10.1029/2022JE007390 |bibcode=2022JGRE..12707390C |s2cid=252934644 |url=https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022JE007390 |access-date=31 October 2022}}

The existence of liquid water on the surface of Mars requires both a warmer and thicker atmosphere. Atmospheric pressure on the present-day Martian surface only exceeds that of the triple point of water (6.11 hPa) in the lowest elevations; at higher elevations pure water can exist only as a solid or a vapor. Annual mean temperatures at the surface are currently less than 210 K (-63 °C/-82 °F), significantly less than what is needed to sustain liquid water. However, early in its history Mars may have had conditions more conducive to retaining liquid water at the surface.

File:PIA03170 fig1duststroms.jpg

Early Mars had a carbon dioxide atmosphere similar in thickness to present-day Earth (1000 hPa).{{cite journal | last1 = Carr | first1 = Michael H | year = 1999 | title = Retention of an atmosphere on early Mars | journal = Journal of Geophysical Research | volume = 104 | issue = E9| pages = 21897–21909 | doi=10.1029/1999je001048 | bibcode=1999JGR...10421897C| doi-access = free }} Despite a weak early Sun, the greenhouse effect from a thick carbon dioxide atmosphere, if bolstered with small amounts of methane{{cite journal | last1 = Squyres | first1 = Steven W. | last2 = Kasting | first2 = James F. | year = 1994 | title = Early Mars: How warm and how wet? | journal = Science | volume = 265 | issue = 5173| pages = 744–749 | doi=10.1126/science.265.5173.744| pmid = 11539185 | bibcode = 1994Sci...265..744S | s2cid = 129373066 }} or insulating effects of carbon-dioxide-ice clouds,{{cite journal | last1 = Forget | first1 = F. | last2 = Pierrehumbert | first2 = R. T. | year = 1997 | title = Warming Early Mars with Carbon Dioxide Clouds That Scatter Infrared Radiation | journal = Science | volume = 278 | issue = 5341| pages = 1273–1276 | doi=10.1126/science.278.5341.1273 | pmid=9360920| bibcode = 1997Sci...278.1273F | citeseerx = 10.1.1.41.621 }} would have been sufficient to warm the mean surface temperature to a value above the freezing point of water. The atmosphere has since been reduced by sequestration in the ground in the form of carbonates through weathering, as well as loss to space through sputtering (an interaction with the solar wind due to the lack of a strong Martian magnetosphere).{{cite journal | last1 = Kass | first1 = D. M. | last2 = Yung | first2 = Y. L. | year = 1995 | title = Loss of atmosphere from Mars due to solar wind-induced sputtering | url = https://www.science.org/doi/10.1126/science.278.5341.1273 | journal = Science | volume = 268 | issue = 5211| pages = 697–699 | doi=10.1126/science.7732377| pmid = 7732377 | bibcode = 1995Sci...268..697K | s2cid = 23604401 }}Carr, M and J. Head III. 2003. Oceans on Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research: 108. 5042. A study of dust storms with the Mars Reconnaissance Orbiter suggested that 10 percent of the water loss from Mars may have been caused by dust storms. It was observed that dust storms can carry water vapor to very high altitudes. Ultraviolet light from the Sun can then break the water apart in a process called photodissociation. The hydrogen from the water molecule then escapes into space.{{cite web | url=https://www.sciencenews.org/article/mars-dust-storms-water?mode=topic&context=36 | title=Massive dust storms are robbing Mars of its water| date=2018-02-07}}{{cite journal | last1 = Heavens | first1 = N. | display-authors = etal | year = 2018| title = Hydrogen escape from Mars enhanced by deep convection in dust storms | journal = Nature Astronomy | volume = 2| issue = 2| pages = 126–132| doi = 10.1038/s41550-017-0353-4 | bibcode = 2018NatAs...2..126H | s2cid = 134961099 }}{{cite web | url=https://www.jpl.nasa.gov/news/news.php?release=2018-012&rn=news.xml&rst=7041 | title=Dust Storms Linked to Gas Escape from Mars Atmosphere| website=Jet Propulsion Laboratory}}

The obliquity (axial tilt) of Mars varies considerably on geologic timescales, and has a strong impact on planetary climate conditions.{{cite journal | last1 = Abe | first1 = Yutaka | last2 = Numaguti | first2 = Atsushi | last3 = Komatsu | first3 = Goro | last4 = Kobayashi | first4 = Yoshihide | year = 2005 | title = Four climate regimes on a land planet with wet surface: Effects of obliquity change and implications for ancient Mars | journal = Icarus | volume = 178 | issue = 1| pages = 27–39 | doi=10.1016/j.icarus.2005.03.009 | bibcode=2005Icar..178...27A}} The study by Schmidt et al. in 2022 shows that the circulation of the ocean tends to minimize the effect of obliquity.{{cite journal |last1=Schmidt |first1=Frédéric |last2=Way |first2=Michael|display-authors=et al.|title=Circumpolar ocean stability on Mars 3 Gy ago |journal=Proceedings of the National Academy of Sciences |date=2022 |volume=119 |issue=4 |doi=10.1073/pnas.2112930118 |doi-access=free |pmid=35042794 |pmc=8795497 |arxiv=2310.00461 |bibcode=2022PNAS..11912930S }} In other words, a circulating ocean will transport heat from the hottest region to the coldest ones (usually mid-latitude to the pole) in order to cancel the effect of obliquity.

Consideration of chemistry can yield additional insight into the properties of Oceanus Borealis. With a Martian atmosphere of predominantly carbon dioxide, one might expect to find extensive evidence of carbonate minerals on the surface as remnants from oceanic sedimentation. An abundance of carbonates has yet to be detected by the Mars space missions. However, if the early oceans were acidic, carbonates would not have been able to form.{{cite journal | last1 = Fairen | first1 = A.G. | last2 = Fernadez-Remolar | first2 = D. | last3 = Dohm | first3 = J. M. | last4 = Baker | first4 = V.R. | last5 = Amils | first5 = R. | year = 2004 | title = Inhibition of carbonate synthesis in acidic oceans on early Mars | journal = Nature | volume = 431 | issue = 7007| pages = 423–426 | doi=10.1038/nature02911 | pmid=15386004| bibcode = 2004Natur.431..423F | s2cid = 4416256 }} The positive correlation of phosphorus, sulfur, and chlorine in the soil at two landing sites suggest mixing in a large acidic reservoir.{{cite journal | last1 = Greenwood | first1 = James P. | last2 = Blake | first2 = Ruth E. | year = 2006 | title = Evidence for an acidic ocean on Mars from phosphorus geochemistry of Martian soils and rocks | journal = Geology | volume = 34 | issue = 11| pages = 953–956 | doi=10.1130/g22415a.1| bibcode = 2006Geo....34..953G }} Hematite deposits detected by TES have also been argued as evidence of past liquid water.{{cite journal | last1 = Tang | first1 = Y. | last2 = Chen | first2 = Q. | last3 = Huang | first3 = Y. | year = 2006 | title = Early Mars may have had a methanol ocean | doi = 10.1016/j.icarus.2005.09.013 | journal = Icarus | volume = 180 | issue = 1| pages = 88–92 | bibcode = 2006Icar..180...88T }}

Given the proposal of a vast primordial ocean on Mars, the fate of the water requires explanation. As the Martian climate cooled, the surface of the ocean would have frozen. One hypothesis states that part of the ocean remains in a frozen state buried beneath a thin layer of rock, debris, and dust on the flat northern plain Vastitas Borealis.{{cite journal | last1 = Janhunen | first1 = P. | author-link = Janhunen, P. | year = 2002 | title = Are the northern plains of Mars a frozen ocean? | doi = 10.1029/2000je001478| journal = Journal of Geophysical Research | volume = 107 | issue = E11| page = 5103 | bibcode = 2002JGRE..107.5103J | s2cid = 53529761 | doi-access = free }} The water could have also been absorbed into the subsurface cryosphere or been lost to the atmosphere (by sublimation) and eventually to space through atmospheric sputtering.

Based on data from InSight, scientists suggested liquid water exists deep underground. According to a paper published April 25, 2025 in the journal National Science Review, recordings of seismic waves from deep within the Red Planet indicate that a layer of liquid water may be in the Martian rocks between 3.4 and 5 miles [5.4 to 8 kilometers] below the surface.

The total volume of hidden water could flood the whole of Mars' surface with an ocean 1,700 to 2,560 feet [520 to 780 metres] deep, around the same volume of liquid that is contained within Antarctica's ice sheet, the study authors estimate.

https://www.livescience.com/space/mars/scientists-find-hint-of-hidden-liquid-water-ocean-deep-below-mars-surface?utm_term=CABA215D-3D47-4C9A-92FE-9ECF8D4C7909&lrh=e62336263a3610a07ef7c8af2080c758f2ecd0661aab1a8e6234cf31f0d0fdff&utm_campaign=368B3745-DDE0-4A69-A2E8-62503D85375D&utm_medium=email&utm_content=7A404C61-C432-438F-9414-F1C935EF3C79&utm_source=SmartBrief Sun, W., et al. 2025. Seismic evidence of liquid water at the base of Mars' upper crust. National Science Review. nwaf166, https://doi.org/10.1093/nsr/nwaf166 . Another group earilier found similar results and suggested the water would be in fractures in igneous rocks.Liquid water in the Martian mid-crust

Vashan Wright https://orcid.org/0000-0002-3238-4526 vwright@ucsd.edu, Matthias Morzfeld https://orcid.org/0000-0003-2257-8930, and Michael Manga https://orcid.org/0000-0003-3286-4682

121 (35) e2409983121

https://doi.org/10.1073/pnas.2409983121 https://www.pnas.org/doi/10.1073/pnas.2409983121 https://www.youtube.com/watch?v=6cPSA9_PrMg https://www.youtube.com/watch?v=KOTxzi_CqFU

They estimate that there is enough liquid water under the surface to produce water across the surface that would be more than half a mile deep. However, it would be hard to get to as it is 10-20km deep. The team of researchers used measurements from more than 1,319 quakes to come to their conclusions.https://www.bbc.com/news/articles/czxl849j77ko Calculations obtained from InSight lander's data suggest up to 2 km global equivalent layer (GEL) could be in the crust.https://www.pnas.org/doi/10.1073/pnas.2418978122 Jakosky, B. 2025. Results from the inSight Mars mission do not require a water-saturated mid crust. Letter Earth, Atmospheric, and Planetary Sciences. 122 (11) e2418978122 https://doi.org/10.1073/pnas.2418978122 https://www.space.com/the-universe/mars/what-happened-to-all-the-water-on-mars-the-debate-continues?utm_term=CABA215D-3D47-4C9A-92FE-9ECF8D4C7909&lrh=e62336263a3610a07ef7c8af2080c758f2ecd0661aab1a8e6234cf31f0d0fdff&utm_campaign=58E4DE65-C57F-4CD3-9A5A-609994E2C5A9&utm_medium=email&utm_content=22609226-D300-4C70-9B8F-1139DC6030FA&utm_source=SmartBrief

The existence of a primordial Martian ocean remains controversial among scientists. The Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE) has discovered large boulders on the site of the ancient seabed, which should contain only fine sediment.{{cite journal | last1 = Kerr | first1 = Richard A | year = 2007 | title = Is Mars Looking Drier and Drier for Longer and Longer? | journal = Science | volume = 317 | issue = 5845| page = 1673 | doi=10.1126/science.317.5845.1673 | pmid=17885108| s2cid = 41739356 }} However, the boulders could have been dropped by icebergs, a process common on Earth.{{Cite conference

| first = A. G. | last = Fairén

| author2 = Davila, A. F.

| author3 = Lim, D.

| author4 = McKay, C. | author4-link = Christopher McKay (planetary scientist)

| title = Icebergs on Early Mars

| book-title = Astrobiology Science Conference

| date = 2010 | url = http://www.lpi.usra.edu/meetings/abscicon2010/pdf/5467.pdf

| access-date = 2010-10-02}}{{Cite web | last = Chol | first = Charles Q.

| title = New Evidence Suggests Icebergs in Frigid Oceans on Ancient Mars

| work = www.space.com, Space.Com website | date = 2010-10-01

| url = http://www.space.com/scienceastronomy/ancient-icebergs-mars-oceans-101001.html

| access-date =2010-10-02 }} The interpretations of some features as ancient shorelines has been challenged.{{cite journal | last1 = Carr | first1 = M. H. | last2 = Head | first2 = J.W. | year = 2002 | title = Oceans on Mars: An assessment of the observational evidence and possible fate | journal = Journal of Geophysical Research | volume = 108 | issue = E5| page = 5042 | doi=10.1029/2002je001963 | bibcode=2003JGRE..108.5042C| s2cid = 16367611 | doi-access = free }}{{cite journal |last1=Sholes |first1=S.F. |author2= Montgomery, D.R. |author2-link=David R. Montgomery |author3=Catling, D.C. |author3-link=David Catling |title=Quantitative High-Resolution Re-Examination of a Hypothesized Ocean Shoreline in Cydonia Mensae on Mars |journal=Journal of Geophysical Research: Planets |date=2019 |volume=124 |issue=2 |pages=316–336 |doi=10.1029/2018JE005837 |bibcode=2019JGRE..124..316S |s2cid=134889910 }}{{cite journal |last1=Malin |first1=M.C. |last2=Edgett |first2=K.S. |title=Oceans or seas in the Martian northern lowlands: High resolution imaging tests of proposed coastlines |journal=Geophysical Research Letters |date=1999 |volume=26 |issue=19 |pages=3049–3052 |doi=10.1029/1999GL002342 |bibcode=1999GeoRL..26.3049M |doi-access=free }}

A study published in September 2021 comparing potassium isotopes found in rocks from various bodies proposes that the surface gravity on Mars was too low to retain enough water to form a large ocean.[https://www.npr.org/2021/09/22/1039288432/mars-liquid-water-surface-size-potassium-mass-space Mars Had Liquid Water On Its Surface. Here's Why Scientists Think It Vanished]

Alternate theories for the creation of surface gullies and channels include wind erosion,{{cite journal | last1 = Leovy | first1 = C.B. | year = 1999 | title = Wind and climate on Mars | journal = Science | volume = 284 | issue = 5422| page = 1891a | doi=10.1126/science.284.5422.1891a| s2cid = 129657297 | doi-access = }} liquid carbon dioxide, and liquid methanol.

Confirmation or refutation of the Mars ocean hypothesis awaits additional observational evidence from future Mars missions.

{{Portal|Solar System}}

• {{annotated link|Extraterrestrial liquid water}}
• {{annotated link|Lakes on Mars}}
• {{annotated link|Life on Mars}}
• {{annotated link|Water on Mars}}
• Terraforming of Mars – Hypothetical modification of Mars that would include a large northern ocean

{{Reflist|2}}

{{Mars}}

Category:Historical oceans

Category:Water on Mars