Evidence of liquid water in Mars's distant past suggests that it had a substantial atmospherecompared to what it has presently. What happened to its water vapor?

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Quizplus · Accepted Answer

Evidence shows that Mars had a warmer and wetter past, which suggests a thicker atmosphere. However, Mars is smaller than Earth and has weaker gravity, which allowed its atmosphere to gradually escape into space. As it lost its atmosphere, the planet cooled and water vapor condensed and froze out into the polar ice caps and permafrost. As Mars cooled, the water vapor in its atmosphere froze out into the polar ice caps and permafrost, leading to the loss of a substantial amount of water vapor in its atmosphere. This is supported by data from various Mars missions, such as the Mars Reconnaissance Orbiter, which has detected water ice on Mars's surface, and the Phoenix lander, which found evidence of subsurface water ice.

Evidence of Liquid Water in Mars's Distant Past Suggests That