By Irene Klotz
CAPE CANAVERAL, Florida (Reuters) - NASA's Mars rover Opportunity is uncovering new details about the role water may have played on what is now a cold, dry planet, scientists said on Thursday.
Opportunity is one of two small rovers that landed on opposite sides of Mars in January 2004 for what were expected to be 90-day studies to look for signs of the past presence of water on the planet. Water is believed to be a key ingredient for life.
Sister probe Spirit succumbed to the harsh Martian environment last year, leaving Opportunity to go solo until the U.S. space agency's next rover, Curiosity, arrives in August 2012.
Opportunity originally touched down near the equator in an area called Meridiani Planum and almost immediately discovered evidence the plain was once covered by shallow, salty and highly acidic water. It later spent two years studying exposed bedrock and other features in a small crater named Victoria.
At a new destination, a 14-mile- (22-km) wide crater named Endeavour, Opportunity has discovered a different type of terrain with a chemical makeup unlike anything previously encountered.
"We may soon be able to study clay minerals and rock types that formed in low-acid, wet conditions, which may tell us more about a potentially habitable environment," Dave Lavery, who oversees the Mars Exploration Rovers program at NASA headquarters in Washington, told reporters during a conference call.
The first rock probed by Opportunity at Endeavour Crater shows very high levels of zinc, which on Earth is commonly found in rocks that have been exposed to hot water, such as thermal springs.
"This rock doesn't look like anything else we've ever seen before," said Cornell University planetary scientist Steve Squyres, the lead rover scientist. "We are thinking very hard over what this means."
The rock is basically basalt, a common volcanic rock, which was cemented together from fragments of other rocks shattered by an impact, for example.
"We may be dealing with a situation where water has percolated or flowed -- somehow moved through these rocks, maybe as vapor, maybe as liquid, don't know yet -- but has enhanced the zinc concentration in the rock to levels far in excess of anything that we have seen on Mars before," Squyres said.
Scientists plan to look for other zinc-rich rocks to see if the concentrations are the same, as well as probe for other minerals likewise tied to water.
Opportunity is on the hunt for bedrock, in particular, which is rock that has not been moved by impacts or other processes.
"We've got some strange stuff going on, but we're not ready to draw any firm conclusions," Squyres said.
(Editing by Tom Brown and Peter Cooney)