The U.S. Mars rover Spiritmay have detected the first evidence of ancient liquid water on the other side of the planet from where scientists revealed last week that a shallow saltwater sea once existed.
Spirit's instruments have detected evidence that water once altered a rock in Gusev crater, a martian site that geologists believe is an ancient lake bed.
Until now, the Opportunity rover has received most of the public attention with its discovery that extensive salt water, possibly an ancient sea, once existed on a plain called Meridiani.
Now, University of Tennessee researcher Hap McSween says a rock at Spirit's landing site suggests strongly that Gusev crater had its own water supply, although nothing like a sea or even a lake.
"This is not water that sloshed around on the surface as it apparently did at Meridiani," said Hap McSween. "We're talking about small amounts of water, possibly underground, but nevertheless some evidence for water."
The scientists say they are still analyzing the data, but they believe one piece of evidence for the water is deposits of salt lining a thin crack inside the rock, which was uncovered by Spirit's scraping tool.