FROM WIKI: Almost all
water on
Mars today exists as ice, though it also exists in small quantities as vapor in the
atmosphere[4] and occasionally as low-volume liquid
brines in shallow
Martian soil.
[5][6] The only place where water ice is visible at the surface is at the
north polar ice cap.
[7] Abundant water ice is also present beneath the permanent
carbon dioxide ice cap at the Martian south pole and in the shallow subsurface at more temperate certain conditions.
[8][9] More than five million cubic kilometers of ice have been identified at or near the surface of modern Mars, enough to cover the whole planet to a depth of 35 meters (115 ft).
[10] Even more ice is likely to be locked away in the deep subsurface.
[11]
Some liquid water may occur transiently on the Martian surface today, but limited to traces of dissolved moisture from the atmosphere and thin films, which are challenging environments for life as we know it.
[6][12][13] No large standing bodies of liquid water exist, because the atmospheric pressure at the surface averages just 600
pascals (0.087
psi)—about 0.6% of Earth's mean sea level pressure—and because the global average temperature is far too low (210 K (−63 °C; −82 °F)), leading to either rapid evaporation (
sublimation) or rapid freezing. Before about
3.8 billion years ago, Mars may have had a denser
atmosphere and higher surface temperatures,
[14][15] allowing vast amounts of liquid water on the surface,
[16][17][18][19] possibly including
a large ocean[20][21][22][23] that may have covered one-third of the planet.
[24][25][26] Water has also apparently flowed across the surface for short periods at various intervals more recently in Mars' history.
[27][28][29] On December 9, 2013, NASA reported that, based on evidence from the
Curiosity rover studying
Aeolis Palus,
Gale Crater contained an ancient
freshwater lake that could have been a hospitable environment for
microbial life.
[30][31]
Although the surface of Mars was periodically wet and could have been hospitable to microbial life billions of years ago,
[54] the current environment at the surface is dry and subfreezing, probably presenting an insurmountable obstacle for living organisms. In addition, Mars lacks a thick atmosphere,
ozone layer, and
magnetic field, allowing solar and
cosmic radiation to strike the surface unimpeded. The damaging effects of ionizing radiation on cellular structure is another one of the prime limiting factors on the survival of life on the surface.
[55][56] Therefore, the best potential locations for discovering
life on Mars may be in subsurface environments.
[57][58][59] On November 22, 2016, NASA reported finding a large amount of underground ice on Mars; the volume of water detected is equivalent to the volume of water in
Lake Superior.
[1][2][3]
