Mars rover reveals details of intriguing rock outcrop

PASADENA, Calif. -- NASA's Opportunity rover has revealed new details about the finely layered rocks that partially ring the shallow crater cradling the spacecraft. New photographs of the rock outcrop, no taller than a curb, show the layers aren't always parallel to one another, NASA said. That suggests the layers were laid down in a dynamic environment. Scientists believe volcanic ash blown across the landscape or dust, transported by water or wind, accumulated to form the angled layers visible in the sulfur-rich rock.

"That generally means whatever medium the matrix was deposited in was in motion -- whether it was the air or water," said Steve Squyres, a Cornell University astronomer and the mission's main scientist.

Opportunity is in the midst of scooting along the outcrop, photographing it and picking specific targets scientists want the spacecraft to revisit and study in further detail. The composition of the rock remains unknown, although scientists have ruled out some minerals.

Opportunity's twin, Spirit, was to resume its own movement after cold temperatures left it grounded for a day.

NASA temporarily could not send commands to Spirit, after the cold prevented the rover from rotating a lollipop-shaped antenna toward Earth. Without the set of commands, Spirit remained parked overnight Tuesday, one day after completing a record-breaking 70-foot drive across the rocky martian surface.

Scientists planned for Spirit to continue rolling toward a crater about 800 feet away. It should reach it within the next three weeks.

NASA sent the rover pair on an $820 million mission to look for geologic evidence that Mars was once a wetter place that might have been hospitable to life.

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