Interesting. Let's say Gliese 581 c is far too hot for human habitation, but not like Venus or anything. If it did form beyond the snow line and has lots of water, let's hypothesize that it has a water-rich atmosphere. Imagine a steamy, hot place.
Now just imagine these rocks, coated with bacteria, pulling water from fog.
Of course, this assumes Gliese 581 c doesn't resemble Venus.
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