NASA: Mars Once Had Shallow Pool of Water

The new findings suggest there was a pool of saltwater at least two inches deep.

A rocky outcropping examined by the rover had ripple patterns and concentrations of salt considered telltale signs that the rock formed in standing water.

"We think Opportunity is now parked on what was once the shoreline of a salty sea on Mars," said Cornell University astronomer Steve Squyres, the mission's main scientist.