Two weeks. The Mars Exploration Rover Spirit has until Christmas to make it to a nice, sunny slope of a nearby plateau, where it will point its solar panels towards the Sun and park for the winter. Unfortunately, Spirit can't just drive. A recent dust storm on the Red Planet drained much of the rover's energy, so at this point it needs a day of rest for every day of travel.
Engineers knew this energy problem would come eventually. Solar panels need to be clean and free of debris to soak up sunlight. But the Red Planet hasn't been cooperating. Those massive dust storms deposit a fine layer of dirt on the panels, vastly reducing their energy-generating capacity.
Some stiff winds blew much of the dust off Opportunity's panels, but Spirit hasn't been so lucky. Spirit is down to 42 percent capacity. Still, though, it's amazing that they're even roving at all at this point. They were supposed to run out of juice several years ago.—Gregory Mone