The Mars rover Spirit has become stuck in loose dirt while ambling around a low plateau, NASA said Monday.
The rover slipped during a recent series of backward drives and its wheels were stuck halfway in the ground. A team at NASA's Jet Propulsion Laboratory was diagnosing the problem and planned to use a test rover on Earth to try to figure out how to get Spirit out of its jam.
"Spirit is in a very difficult situation," JPL project manager John Callas said in a statement.
Engineers and scientists are concerned the rover's chassis could soon touch the rocks underneath and complicate efforts to free itself.
Engineers temporarily stopped sending commands to move Spirit and it could be weeks before the rover drives again.
Spirit and its twin Opportunity landed on opposite ends of Mars in 2004 and have far outlasted their primary, three-month mission.
Spirit has five working wheels; its right front wheel stopped working three years ago.
Lately, Spirit has been showing its age. Last month, it suffered several bouts of amnesia and other problems including sudden computer reboots and failure to wake up when called on. Though the rover has since recovered, investigators still do not know the reason for its strange behavior.