Spirit Struggles to Survive the Martian Winter 

Two years and three months after landing on Mars, Spirit can't help but dig trenches in the martian sand. The right front wheel of NASA's Mars Exploration Rover is no longer working.

As a result, the rover's handlers on Earth are having a difficult time getting the rover to a suitably north-facing slope to survive the cold, dark, martian winter. The rover must face its solar panels northward to collect enough solar energy as the sun sinks low above the horizon. Essentially, it's a race against time. The period of minimum sunshine in the martian winter is more than 100 days away, but Spirit currently gets only enough power for about one hour of driving on flat ground. And, Spirit literally has an up-hill battle. 

Safety is Priority #1

"It is too early to tell how serious this is," said Project Manager John Callas. "The nature of the terrain is a dominant factor."

"The climate is changing rapidly, and we have to put our primary emphasis on keeping the rover safe,” remarked principal investigator and Cornell University geologist Steve Squyres. “Assuring survival has to take priority over science until we've got the vehicle on safer ground." That means the team has stopped trying to move Spirit along an uphill route that proved too daunting. Instead, Spirit is in the process of driving back downhill before beginning a different trek toward a slope that will provide maximum sunlight--and thus power--to survive the martian winter. (On the other side of Mars and nearer to the martian equator, Spirit's twin Opportunity does not face the same power concerns.)

 Rover Loses Traction in Soft Soil

Progress has been intermittent. Spirit drove 10 meters (33 feet) in one day after the wheel stopped working, then lost traction on following days because of wheel slippage in difficult terrain. The rover team continues to evaluate all potential directions of travel, as well as mechanical tricks for tilting the rover sunward.

The rovers' suspension systems, which keep all six wheels in contact with the surface, have helped make both Spirit and Opportunity hardy explorers on steep slopes and sandy terrain as their investigations have continued far beyond their original 90-day warranties.