Martian Gypsum

NASA's Opportunity rover has found what looks to be a vein of gypsum on the rim of Endeavour crater. Gypsum has been found elsewhere on Mars, but this would be the first time it was found clearly in association to where it formed.

Gypsum is a mineral associated with running water on Earth, and scientists think the same would hold true on Mars. If it does, this discovery could be the strongest evidence yet for a warmer, wetter early Mars. That, in turn, would increase the odds for life existing on Mars at some point.