This is an image of fog in a Martian canyon.
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Image from: NASA
Martian Fog
This is an image of fog in a Martian canyon. The presence of fog provides evidence of water, and a water cycle on Mars. More fog has been seen in images returned by Mars Global Surveyor of the south polar region of Mars.
Martian fog may contain a bit of carbonic acid, just as terrestrial rain also contains a little bit of acid. Acid in the fog may contribute toward weathering of the Martian surface rocks.
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