Age, terrain challenge rovers

PASADENA, Calif. -- NASA's Mars rovers, challenged by tough terrain and age, are still making discoveries, including a new find of a mineral usually formed in water, scientists said Friday.

The Spirit rover found hematite in a rock at the Columbia Hills after a trek across the plains of the Gusev Crater region, where it previously had seen geologic evidence of only limited past moisture.

Spirit's twin, Opportunity, found hematite soon after landing on the other side of the planet, leading scientists to believe that area was once drenched in water, and conditions there could have been suitable for life.

Finding hematite again cheered scientists even though they have yet to make enough observations to determine if the hematite formed in water or through dry processes.

Spirit was sent to Gusev Crater to find "a water story," said Steve Squyres, an astronomer at Cornell University and the mission's principal investigator. Only lava was discovered.

The faraway Columbia Hills looked more promising but the 1 1/2-mile distance seemed too much for the rover, which was designed to travel one kilometer, or 0.6 mile. The drive was apparently worth it.

"We may have a water story here," Squyres said.

The hematite was found in a rock dubbed "Pot of Gold" -- small enough to fit in the palm of a hand, with microscopic features that Squyres described as "little nuggets on the end of stalks."

He said he did not know how the features formed.

The drive to Columbia Hills took a toll on Spirit. Like a balky shopping cart, the rover has a front wheel that's having difficulty turning. So rover drivers are learning to maneuver the vehicle with only five wheels if they must.

Opportunity, meanwhile, faces an increasingly steep slope as it descends into Endurance Crater at Meridiani Planum to examine rocks older than the surface outcrop where it found evidence of past water.

"We think we're into something that is subtly different," Squyres said.

"It's pointing in a direction of there having been more water than we originally thought, but periods of wetting and drying."

The rover is on a 23-degree slope at the precipice of a 35- to 40-degree slope.

"There is an extremely large amount of advantage to being able to continue down that slope, but we're right at the design capability of the vehicle," Rover engineer Chris Voorhees said.

He said the rovers were operating soundly despite being well into extended missions. Both touched down on Mars in January.

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On the Net:

JPL: http://marsrovers.jpl.nasa.gov

Cornell University: http://athena.cornell.edu