Scientists have been studying the the McMurdo Dry Valleys: places in Antarctica where it never rains. Ever. And, yet, you’ll find patches of moisture on the ground. Why?
Salt. What happens is, the soil is at a certain salinity, and once there’s enough humidity, the soil sucks the water right out of the air.
So what’s this have to do with Mars? The soil is salty enough and the humidity is high enough that this probably happens quite a lot on Mars. This is good news on several levels: first, it means alien microbes might be living in Mars soil. Secondly, it means terraforming Mars might be easier: for example, we could dump machines on the surface that do nothing but combine hydrogen and oxygen from Mars’ atmosphere, and pump it into the air.
And, really, anything to get off this rock. We want a Mars colony, dammit!
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