As winter fast approached, Spirit saw its life flash before its panoramic camera eyes.

Exposed on a flat surface with its solar energy dwindling, the Mars rover needed to find a safe hill on which to rest during win ter and soak up the sun’s rays at an appropriate tilt.

But there was a problem. Spirit’s right front wheel was dead, leaving the robotic NASA probe vulnerable to the planet’s harsh climate.

This rover, however, proved once again that survival is something it and its twin, Opportunity, continue to master since NASA sent them to Mars in January 2004.

Simply put, Spirit cheated death. Again.

The rover drove backward 262 feet, dragging itself to safety.  

Now, nearly 900 days into a mission that wasn’t supposed to last more than 90, the rover is  re-energizing, enjoying a software upgrade and waiting for the Martian thaw.

"Once spring comes, we’re going to be on our way again," said Steve Squyres, a Cornell University scientist who heads the mission’s science team.

Spirit, which along with Opportunity make up NASA’s $900 million Mars Exploration Rover Mission, first ran into trouble March 13 when the drive motor on its front-right wheel died.

The rover had been studying signs of an ancient explosion at a low plateau called Home Plate and was inching its way toward a north-facing hill where it could spend the winter.

During the Martian winter, the solar-powered rovers must face north and sit at an angle to recharge. Both are completely dependent on this process.

But on the way to the site, known as McCool Hill, the rover nearly got stuck in the loose soil. The team decided to change its course and head to a site called Low Ridge, where it sits now.

"I was frankly quite concerned about Spirit until we found this ridge," Squyres said. "It is really getting into the coldest, darkest, toughest months of winter, which means we don’t have a lot of solar power."

The rover reached the site in April and has been gathering the available solar energy and conducting research about 15 minutes a day, analyzing the atmosphere and the soil immediately around it and taking a massive panoramic photograph.

The Martian winter ends around Thanksgiving.

Though marginally operational, Spirit’s wheel likely will never be functional again.

"It’s kind of like having one of those grocery store shopping carts where one of the wheels is jammed," said project manager John Callas. "It will be more difficult to drive. We won’t be able to go as far."

Opportunity now is closing in on Victoria crater, said project scientist Bruce Banerdt. The crater is about a half-mile wide and 250 feet deep.

Examining the crater is "like turning back the pages of a history book," Banerdt said. "That’s one of the great things about craters: They excavate down into the rock layers."

Both rovers also are getting new computer software to make them more autonomous.

In addition to fixing minor bugs, the new software allows the rovers to navigate around complex obstacles, analyze rocks with their robotic arms and take targeted pictures of dust devils, all independent of human programmers.

As for when the project might end, nobody can tell, said Rongxing Li, an Ohio State University mapping specialist who heads a team plotting the rovers’ travels.

"And nobody wants to," he said.

mzapotosky@dispatch.com