'Layer cake' bedrock on Mars hints at water

PASADENA, Calif. -- The "most striking image yet" from NASA's Mars rovers reveals fine layers within bedrock, suggesting that the rock was formed by sediments swept down by ancient waters, the lead scientist for the mission said Tuesday.

"Wonderful layer-cake structure here," said Steven W. Squyres, a professor of astronomy at Cornell and the Mars mission's principal science investigator. "It's going to be fascinating beyond words to get up-close-and-personal with these things."

Andrew H. Knoll of Harvard, a member of the mission's science team, said the layers could also have formed out of ash from successive volcanic eruptions.

Scientists cannot tell from the photographs alone which explanation is more likely, but other instruments aboard the rover Opportunity should offer more conclusive evidence.

"We should be able to distinguish between those two hypotheses," Knoll said.

Squyres and Knoll described the new photographs at a news conference here at NASA's Jet Propulsion Laboratory, which is running the mission.

The Opportunity landed early on Sunday, and controllers are now powering up equipment and putting the rover to work. Jim Erickson, a mission controller, said Tuesday that the high-speed antenna had been deployed and tested. With it, the rover's transmissions to Earth will be able to pack in 10 times as much data.

Engineers for NASA said they were investigating why one of the Opportunity's heaters would not turn off completely. They said it did not pose a major problem at the moment.

The rover, which was folded to fit in tight confines for the journey to Mars, will next "stand up," lifting itself on a post so it can extend its six wheels. Controllers expect it will take at least another week to get the rover ready to begin driving around the surface and heading toward the bedrock outcrop.

"We are about to embark on what is arguably going to be the coolest geologic field trip in human history," Squyres said.

The light-colored bedrock is believed to underlie the whole region where the Opportunity landed, known as Meridiani Planum and spanning tens of thousands of square miles. Knoll said the vast expanse of rock led him to discount the possibility that the rocks formed out of sediment blown in by wind.

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