The Mars rover Spirit, hampered by a broken wheel, has failed to reach its destination and will spend the Martian winter at an alternate site, scientists said Monday.
The solar-powered Spirit was rolling toward the north-facing side of McCool Hill last month to recharge on some sunshine during the winter when its right front wheel stopped working.
After they failed three times to get it to climb McCool, engineers steered Spirit to a closer slope known as Low Ridge, where it arrived over the weekend and will spend the winter, said principal scientist Steve Squyres of Cornell University.
It's not the first time Spirit has had trouble with its right front wheel. The wheel previously had an episode of balkiness, but the latest problem is worse because the motor that spins the wheel stopped working.
"We are anticipating it will be a five-wheeled rover for the rest of the mission," he said.
After the wheel stopped working last month, Spirit drove backward while dragging its broken wheel. But the bad wheel kept slipping into a sandy trench on its way toward McCool, said Jacob Matijevic, engineering team chief.
Although the alternate site should provide enough sunlight for Spirit, it won't be as strong as it would have received on McCool Hill, Matijevic said.
Engineers are considering directing Spirit to McCool in the spring.
Spirit and its twin, Opportunity, landed on opposite ends of Mars in January 2004. Opportunity is making its way to the giant Victoria crater.
Spirit and Opportunity, managed by NASA's Jet Propulsion Laboratory, have outlasted their primary missions.