Rock Varnish - life on Mars?

http://www.spaceref.com/news/viewpr.html?pid=27197

Rocks coated with a bacteria that needs very little water. It pulls its water from fog. The bacteria has been found in deserts that are the closes to Mars' conditions.

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.