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NASA hopes to free Mars rover from sand
Earth-bound controllers are ordering Spirit, the aging Mars rover stuck in a deadly Martian sand trap since April, to start spinning its wheels in a last-ditch effort to make the little vehicle dig itself out and continue its epochal voyage over the red planet's hilly surface.
For six months, the engineers and scientists at NASA's Jet Propulsion Laboratory in Pasadena have been running every conceivable scenario for freeing the decrepit rover. Their first effort to drive it out of the loose sand in May failed.
They have repeatedly tested new strategies on a full-scale replica of Spirit that rests in the lab in a sandbox that exactly mimics the Martian soil that holds the vehicle captive.
Now they face a deadline of sorts.
Douglas McCuistion, director of NASA's Mars Exploration Program at the agency's headquarters in Washington, said the Jet Propulsion Laboratory team has until February to solve Spirit's problem, and if it isn't freed by then, the agency's senior advisers will decide on a course of action.
Either the rover will continue doing what it can where it stands as long as its instruments and communication system last, or the engineers will be allowed to make one more - and most probably fruitless - effort to get it out of its sandy trap.
The hardy robot vehicle and its twin rover, Opportunity, have been exploring Mars' surface since their landings by parachute in January 2004. They had a programmed lifetime of only three months, but have radioed major discoveries of the planet's history, geology and evidence of ancient water back to Earth ever since.
Now Spirit is in danger, said John Callas, the joint mission's engineering project manager, in a phone interview Wednesday.
"It's the most complex situation Spirit has faced in 5 1/2 years, and we can't make any predictions about whether we'll succeed ... in getting it out of the loose, fine sand where it's embedded," he said.
Early this morning, the rover's human controllers will send radio commands telling Spirit to spin its wheels for the equivalent of moving straight ahead for about 8 feet. At the same time, onboard cameras will photograph its underbelly and two of its six wheels.
Then, armed with the pictures and the results from the spinning wheels, the controllers will decide what to do next.
The aging rover faces other hazardous predicaments, controllers say: Its right front wheel has been jammed tight for many months; a sharp-pointed rock juts up just beneath Spirit's body and threatens to puncture it if the vehicle settles further into the sand; and the rover is tilted dangerously about 12 degrees.
Spirit had traveled 4.8 miles from where it landed in 2004 when it got stuck on April 23. It had just rounded a small plateau the scientists call Home Plate and was driving across a patch of sandy crust when it broke through and sank hub deep. An effort to free it by getting the rover to spin its wheels to gain traction proved futile; the rover just sank deeper. By May 5, mission controllers gave up and began working on a new strategy.
Data returned from the vehicle show that Spirit is straddling a crater 26 feet wide that was filled long ago with sulfate-bearing sands produced either by water or steam, said Raymond Arvidson, a planetary scientist at Washington University in St. Louis who is the mission's deputy chief scientist.
In that sense, the disaster produced some good, Arvidson said, because scientists were able to learn that the spot where Spirit stands holds some of the strongest evidence yet for sulfur-bearing rocks along the rover's route - again, more evidence that Mars once held water.
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