Heating Early Mars

A new study argues that huge impacts early in Mars history, nearly four billion years ago, could have heated the planet hundreds of degrees, releasing greenhouse gases into the atmosphere that could have sustained a warm, wet climate for centuries.

Huge craters on Mars, hundreds of miles in diameter, bear witness to several catastrophic collisions, each of which would have dwarfed the shot that presumably wiped out the dinosaurs.  The terrific energy of the blasts would have pushed the surface temperature well beyond the boiling point of water, but the planet would have begun to cool.  At some point during the cooling, before Mars became the cold, dry world of today, it would have passed through a brief era when liquid water could have existed on the surface.  There is good geological evidence to support water playing a significant role in shaping the surface we see.

Was the warm, wet period long enough to allow life to arise?  That's the big question, and it remains unanswered.