Mars rovers have found new evidence that water was once plentiful in the hills and plains of the now-barren Red Planet. 

After discovering the plains where it landed was once a salty sea, Opportunity sent back new evidence suggesting that the area had a second drenching sometime after the plains dried out.

Spirit also found signs that water changed rocks in a range of hills halfway around the planet from its partner Opportunity.

After completing its primary mission, Spirit drove about two miles from its landing site to the Columbia Hills where it found rocks, older than the lava flows forming the floor of Gusev Crater that contained water-related minerals.

Scientists say all of the hill's rocks had been altered by exposure to water.

The twin robots have been examining rocks and terrain on opposite sides of Mars since January for clues about whether the planet once held enough water to support life.

(CRI October 9, 2004)