Liquid water[edit]
Main article: Water on Mars
A series of artist's conceptions of past water coverage on Mars.
Liquid water, necessary for life as we know it, cannot exist on the surface of Mars except at the lowest elevations for minutes or hours.[56][57] Liquid water does not appear at the surface itself,[58] but it could form in minuscule amounts around dust particles in snow heated by the Sun.[59][60] Also, the ancient equatorial ice sheets beneath the ground may slowly sublimate or melt, accessible from the surface via caves.[61][62][63][64]
Water on Mars exists almost exclusively as water ice, located in the Martian polar ice caps and under the shallow Martian surface even at more temperate latitudes.[65][66] A small amount of water vapor is present in the atmosphere.[67] There are no bodies of liquid water on the Martian surface because its atmospheric pressure at the surface averages 600 pascals (0.087 psi)—about 0.6% of Earth's mean sea level pressure—and because the temperature is far too low, (210 K (−63 °C)) leading to immediate freezing. Despite this, about 3.8 billion years ago,[68] there was a denser atmosphere, higher temperature, and vast amounts of liquid water flowed on the surface,[69][70][71][72] including large oceans.[73][74][75][76][77] It has been estimated that the primordial oceans on Mars would have covered between 36%[78] and 75% of the planet.[79]
Liquid water[edit]
Main article: Water on Mars
A series of artist's conceptions of past water coverage on Mars.
Liquid water, necessary for life as we know it, cannot exist on the surface of Mars except at the lowest elevations for minutes or hours.[56][57] Liquid water does not appear at the surface itself,[58] but it could form in minuscule amounts around dust particles in snow heated by the Sun.[59][60] Also, the ancient equatorial ice sheets beneath the ground may slowly sublimate or melt, accessible from the surface via caves.[61][62][63][64]
Water on Mars exists almost exclusively as water ice, located in the Martian polar ice caps and under the shallow Martian surface even at more temperate latitudes.[65][66] A small amount of water vapor is present in the atmosphere.[67] There are no bodies of liquid water on the Martian surface because its atmospheric pressure at the surface averages 600 pascals (0.087 psi)—about 0.6% of Earth's mean sea level pressure—and because the temperature is far too low, (210 K (−63 °C)) leading to immediate freezing. Despite this, about 3.8 billion years ago,[68] there was a denser atmosphere, higher temperature, and vast amounts of liquid water flowed on the surface,[69][70][71][72] including large oceans.[73][74][75][76][77] It has been estimated that the primordial oceans on Mars would have covered between 36%[78] and 75% of the planet.[79]
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