New Evidence of "Wetter" Mars

The Mars rover Spirit has uncovered the strongest evidence yet that the planet used to be wetter than previously thought.

Scientists say the robot analyzed a patch of soil in Gusev Crater and found it unusually rich in silica, which is produced by water.

Researchers say the latest find is compelling because of the high silica content, raising the possibility that conditions may have been favorable for the emergence of primitive life.

The durable Spirit and its twin, Opportunity, have been working on overtime since completing their primary, three-month mission in 2004.

The mission is managed at NASA"s Jet Propulsion Laboratory in Pasadena.

NASA said the find was "compelling new evidence for ancient conditions that might have been favorable for life".

"This is a remarkable discovery," said Steve Squyres of Cornell University. "And the fact that we found something this new and different after nearly 1,200 days on Mars makes it even more remarkable.

The discovery was made by a highly sensitive X-ray spectrometer fitted on the rover"s arm as it probed a low range of hills near the Gusev Crater.

Spirit had earlier gleaned further clues that water had once flowed at the site including patches of water-bearing, sulfur-rich soil and evidence of explosive volcanic activity.

"This is some of the best evidence Spirit has found for water at Gusev," said Albert Yen, a geochemist at NASA"s Jet Propulsion Laboratory, Pasadena.

The silica may have originated from volcanic activity or could have been from water in a hot spring environment, NASA said.