NASA Tries to Save Rover from Martian Winter
The NASA rover Spirit, which rolled onto the Martian surface six years ago Friday after a nearly seven-month journey from the Space Coast, is fighting for survival.
Mired since April in soft, talcum powder-like soil, and with only four of six wheels still working, efforts to free Spirit from its sand trap in recent months have made little progress.
Now with winter approaching, the priority is shifting to tilting the 384-pound rover so its solar arrays might be able to generate enough power to keep critical systems warm when temperatures dip as low as minus 150 degrees Fahrenheit.
"If we get favorable winds that blow the dust off the solar arrays, we could keep going for quite some time," said John Callas, project manager for Spirit and its twin, Opportunity, at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "But there's a chance we won't make it through the winter."
Managers haven't given up, but Spirit's mission sooner or later appears likely to change from rover status to that of a stationary science observatory.
Fortunately, after traveling a total of 4.8 miles, Spirit has stalled in a scientifically exciting place, akin to "your car breaking down next to Disney World," Callas said.
Spirit's crisis began last spring as it rolled backward across a location scientists call Troy. It was trying to reach two volcanoes for study before seeking a winter haven in a broader area known as Home Plate in Mars' southern hemisphere.
Crossing familiar-looking terrain, Spirit broke through a hard, crusty surface and sank into soft material, as if breaking through hard snow into a mushy layer below.
The wheels dug in deeper during escape attempts, embedding most to their hubcaps.
Complicating the situation, Spirit appears to be resting on top of a rock that may be making it harder to gain traction.
"It's like if you've gotten your car high-centered on a tree stump, then you've got to call AAA," Callas said. "But if it's a loose rock that's floating, that's moving around, then maybe it's not a problem."
Making matters worse: The rover's right-rear wheel recently locked up, leaving three functioning on the left side and one on the right. The right-front wheel failed in 2006, prompting "drivers" on Earth to often move the rover in reverse.
Only a few more maneuvers remain to be attempted.
"If Spirit cannot make the great escape from this sand trap, it's likely that this lonely spot straddling the edge of this crater might be where Spirit ends its adventures on Mars," said Doug McCuistion, director of the Mars exploration program at NASA Headquarters in Washington, D.C., before intense extrication efforts began in November.
Spirit is thought to be straddling the edge of a buried crater, in an area that shows evidence of minerals having been moved from one location to another, likely transported by water and perhaps as recently as 1 million years ago.
An immobile Spirit still could conduct meaningful research.
"We can study the interior of Mars, monitor the weather and continue examining the interesting deposits uncovered by Spirit's wheels," said Ray Arvidson of Washington University in St. Louis, deputy principal investigator for the rovers.
Opportunity, which landed about three weeks after Spirit, still is performing well halfway around the red planet.
But Callas said members of the Spirit team now view their rover a bit like a champion athlete relegated to a wheelchair by age and infirmity - still special, but no longer capable of the same feats.
"At some point, if we're doing our job, the rovers will wear out, and maybe that's what we're seeing with Spirit right now," Callas said. "Maybe the mobility system is finally wearing out after all the adventure and activity on the surface."
Next month could be a decision point, as NASA undertakes a scientific review of all its Mars missions and makes recommendations about how to maximize their scientific benefit. The rovers have a combined annual budget of $20 million.
Winter on Mars arrives in May, and the season lasts about twice as long as it does on Earth.
"The exploration that we've conducted while we've been on the surface of Mars has been phenomenal," Callas said. The missions were scheduled to last only three months. "It's exceeded all expectations."