MELISSA BLOCK, host:
In case you haven't been paying attention, NASA's two Mars rovers are still alive. Spirit and Opportunity have been driving around Mars for three and a half years, far longer than anticipated. In about a week, NASA plans to try to send one of them down into the crater of death, actually it's called Victoria Crater, but it could be the crater of death if there are problems.
NPR's David Kestanbaum has the story.
DAVID KESTENBAUM: The rover Opportunity arrived at the crater nine months ago. Since then it has been driving around the edge peering in. In part, looking for a safe way to descend. All, of course, at the direction of scientists back here on earth, like Alan Stern, who made the decision to go for it.
Mr. ALAN STERN (Associate Administrator, National Aeronautics and Space Administration): Now entering this crater does come with some unknowns. We can't be certain about the terrains and the footing down in the crater until we go there.
KESTENBAUM: We are, he said, quote, "leaning forward with our risk posture." The crater may have formed billions of years ago, and all down its walls are layers of rock going back in time. Steven Squires is the lead scientist on the mission.
Mr. STEVE SQUIRES (Lead Scientist, Mars Science Exploration Program): The thing that really caught our eye, and this visible all the way around the crater like a bathtub ring, there is a band of bright material at the very top. It's less than a meter thick and it's distinctly bright. It weathers differently. It is somehow different from everything else around it.
KESTENBAUM: Victoria Crater is a couple of hundred feet deep. From orbit, it looks like a cupcake wrapper that's been shoved in the ground. John Callas, the project manager, says they found a way in that's not so steep.
Mr. JOHN CALLAS (Project Manager, Mars Exploration Rover Mission): You could walk down it, provided you kept careful footing as you went in. I mean, you know, it's much like going up to the rim of a meteor crater in northern Arizona.
KESTENBAUM: The rover is slightly arthritic, Callas said. The steering for one of its six wheels jammed a while back. Fortunately it jammed with the wheel straight ahead.
Mr. CALLAS: Driving down is not a problem, it's coming back out again. And we have driven up things as steep as 32 degrees. And the steepest we should ever see here is 20 degrees. So we feel confident that the rover can get out safely, provided the rover remains healthy.
KESTENBAUM: The original mission called for three months of operation. The rovers have been on Mars for three-and-half years now. John Callas says another couple of years would be fine with him.
Mr. CALLAS: Perhaps when the times comes that they're degraded, they've lost their mobility and then you might, you know, think maybe it's better that they pass on, but right now they are doing great stuff.
KESTENBAUM: The plan is to have the rover dip its toes in the crater then come right back out as a test in about a week.
David Kestenbaum, NPR News.
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