Mars ocean theory
Evidence for this ocean includes geographic features resembling ancient shorelines, and the chemical properties of the Martian soil and atmosphere.
[9][10][11][12] Features shown by the Viking orbiters in 1976 revealed two possible ancient shorelines near the pole, Arabia and Deuteronilus, each thousands of kilometers long.
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.
[9][4] 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.
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.
[24] 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.
[25] 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.
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.
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.
[37][38][39] 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.
As Tharsis volcanoes erupted they added huge amounts of gases into the atmosphere that created a global warming, thereby allowing liquid water to exist.
[41][42][43] 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.
[44][45] 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.
[46] 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.
[citation needed] 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.
The atmosphere has since been reduced by sequestration in the ground in the form of carbonates through weathering,[48] as well as loss to space through sputtering (an interaction with the solar wind due to the lack of a strong Martian magnetosphere).
[53][54][55] The obliquity (axial tilt) of Mars varies considerably on geologic timescales, and has a strong impact on planetary climate conditions.
[57] 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.
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.
[65][66][67] 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.
