The signs of a hydrothermal system found by the Surveyor hint at a thicker, more Earth-like atmosphere during the planet's first couple billion years. High temperatures may also be one reason the planet is now red. The Greeks thought the Martian color meant war and destruction; Surveyor may end up proving it means creation.
Hot Times on Mars
If life teemed upon the Red Planet once upon a millennium, it
wouldn't have lacked for H20. The Jet Propulsion Laboratory, which pulls
the strings on the Mars Global Surveyor satellite, now reports that Earth's
neighbor shows the first clear evidence of oceans and widespread thermal
activity
in its early history -- both crucial elements in any sort of Martian genesis.