YOUNGER DAYS: The Spirit rover, being prepped for launch in 2003, has endured on Mars for six years but will face a major hurdle in trying to survive the Martian winter without all of its faculties. Image: NASA
The Mars rover Spirit, which this month passed its sixth anniversary of landing on the Red Planet, will apparently rove no more. NASA announced in a teleconference Tuesday that Spirit, stuck for months in a patch of soft soil known as Troy, has been designated a "stationary research platform". Spirit has not managed to free itself in a series of extraction maneuvers that began in November, and the rover's controllers say that their focus must now turn to preparing for the onset of winter in the Martian southern hemisphere—a harsh season, lasting nearly half an Earth year, that Spirit may not survive.
Doug McCuistion, director of NASA's Mars Exploration Program, said that Spirit's driving days are likely finished. He called the rover's plight "a golfer's worst nightmare—the sand trap that no matter how many strokes you take, you can't get out of it."
Spirit lost the use of one of its six wheels years ago, and another wheel gave out during the rover's recent struggles at Troy. With only four functioning wheels, the extrication process has been hindered, said John Callas, project manager for Spirit and its twin rover, Opportunity, at the NASA Jet Propulsion Laboratory (JPL) in Pasadena, Calif. (Opportunity soldiers gamely on from its landing site halfway around the planet.) Callas said the most immediate challenge for Spirit will now be surviving the long, cold Martian winter, for which the rover is not well positioned to maximize its gathering of solar power. "We're clearly seeing a decrease in energy levels for the rover," Callas said. "The embedding has left the rover in an unfavorable position."
Rover driver Ashley Stroupe of JPL said that Spirit's controllers are working to improve the positioning of the rover's solar panels, whether by adjusting Spirit's tilt or rotating it in place somewhat. If Spirit cannot gather enough power to stay awake throughout the winter, Callas said, it will enter a state of hibernation from which it will periodically awake and attempt to communicate when its batteries are sufficiently charged.
One concern is that without the energy necessary to keep its components warm, Spirit will experience a fatal electronics failure. Callas estimated that the temperatures Spirit will experience during winter, reaching down below –40 degrees Celsius, would approach the boundaries of the rover's operating specs. Although the temperatures should remain within Spirit's nominal limits, no one knows how fragile the aging rover may be at this point. "Those design limits were tested for a brand-new rover, fresh out of the box," Callas said.
Cornell University planetary scientist Steve Squyres, the principal science investigator for the rovers, expressed hope "that Spirit will survive this cold, dark winter that we have ahead of us." If it can hang on, Squyres said, spring will bring a slew of opportunities for Spirit to conduct scientific investigations on Mars. "The one that I am most excited about is tracking the radio signal from Spirit," Squyres said. Now that its roving days are done, Spirit will act as a stationary radio beacon, tracing Mars's orbit through space in three dimensions. That motion, over a period of months, would allow researchers to very accurately characterize the wobble in Mars's axis of rotation, and might therefore provide a long-sought answer to whether Mars has a molten core, as Earth does. This is "totally new science, never been done before, really fundamental stuff," Squyres said.
McCuistion echoed the optimistic sentiment, noting that Spirit has more contributions to make, both to science and to public interest in space exploration. "This is not a day to mourn Spirit," he said. "This is not a day of loss."