Washington, Sept 2 : Veteran Martian rover Opportunity that is exploring the rim of a vast Martian crater have found evidence of water and chemicals unlike anything the robot has seen so far - a finding that could explain the red planet appears more favorable for life.

Opportunity arrived three weeks ago at the 22-km-wide crater, Endeavour, and the first rock it examined is a flat-topped object about the size of a footstool that apparently was cast up by an impact that left an impression the size of a tennis court on the crater's rim.

Called "Tisdale 2", the rock is different from any rock ever seen on Mars, said Steve Squyres, a Cornell University scientist who is the principal investigator for Opportunity.

"It has a composition similar to some volcanic rocks, but there's much more zinc and bromine than we've typically seen. We are getting confirmation that reaching Endeavour really has given us the equivalent of a second landing site for Opportunity," he said.

In the past two weeks, the researchers have used an instrument on the rover's robotic arm to identify elements at several spots on "Tisdale 2".

The observations by Mars orbiters suggest that the rocks on Endeavour's rim include clay minerals that form in less-acidic wet conditions, possibly more favorable for life.

"A bench around the edge of the crater looks like sedimentary rock that's been cut and filled with veins of material possibly delivered by water," said Ray Arvidson, the rover's deputy principal investigator at Washington University in St. Louis. (ANI)