NASA's Mars rover Spirit is in its final resting place, mired in sandy soil on the edge of a small crater in the Martian hills.
It has traveled nearly five miles and taken more than 100,000 pictures since it landed on Mars in 2004. Along with its twin, Opportunity, still driving on the opposite side of the planet, it has helped prove that Mars was once a warm, moist place, with pools of brackish water -- and perhaps conditions that made life possible. The six-wheeled Spirit has become, in a sense, a true Martian.
But since last spring it has been stuck in one place, and today NASA mission managers announced that they have given up trying to free it. They said they will try to continue taking scientific readings -- if Spirit's aging systems can survive the oncoming Martian winter.
"It's kind of a poignant moment for us," said Steve Squyres, the Cornell University scientist who helped get the two rovers to Mars and serves as principal investigator for the mission. "We built the rovers to move, and we've been driving to find new things."
Since the cameras, instruments and electronics still work, Squyres and his colleagues at NASA said they will continue their work. "The bottom line is that we're not giving up on Spirit," he said.
But time is running out. Winter -- with temperatures of 50 degrees below zero Fahrenheit -- is quickly coming to Spirit's resting place. The hardy little rover (about the size of a golf cart) survived three previous winters by parking on a sun-facing slope, so that its solar panels could still soak up power, even when the sun was low on the horizon.
The engineers on earth won't have that option this year. Spirit's wheels, dug deep in the dust, turn uselessly when the rover is commanded to move.
"The rover will be like a polar bear hibernating, and it could be that way for many months," said John Callas, the rover project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. For lack of solar power, even Spirit's radio transmitter will be turned off.
"Yes, the temperatures are within the rover's design limits, but that's for a brand-new rover, straight out of the box," said Callas during a teleconference today. After six years on Mars, he said, batteries are harder to charge and parts have worn out. "There's no guarantee it will survive these temperatures."
That said, NASA also points out that the twin rovers are a case in which the taxpayers got their money's worth. When they landed on Mars in January 2004, engineers said they would be pleased if they operated for 90 days. They've lasted six years.
Squyres said that using the data returned by the rovers, researchers have published 91 scholarly papers in scientific journals, and made 407 presentations at scientific conferences. Perhaps as important, the rovers' exploits have been exciting to people on earth who followed them.