The Mars rover Spirit has suffered through many hardships in its five years on the forbidding planet, outliving the scope of its original mission by more than 20 times in the process.

But now Spirit faces a new and tricky challenge—its wheels have partly sunk into a patch of soft soil. The rover's controllers have put a halt to driving operations while they try to figure out how to get it unstuck.

"Spirit is in a very difficult situation," John Callas, project manager for the rovers at the NASA Jet Propulsion Laboratory (JPL) in Pasadena, Calif., said in a statement yesterday. "We are proceeding methodically and cautiously. It may be weeks before we try moving Spirit again." A JPL spokesperson said today that the rover's condition had not changed.

Since 2006 the buggy has been dragging a broken front wheel, and this year Spirit has suffered a few mysterious bouts of amnesia and erratic behavior. (Its twin rover, Opportunity, is aging somewhat better and soldiers on without a hitch.)

Even now, the rover remains powered and alert, and project scientists plan to use its onboard geological instruments to investigate the pesky soil. Researchers on the ground will also "attempt to replicate the rover's plight in what is known as the 'sandbox,' a lab at JPL where scientists try to simulate conditions on Mars," according to the Los Angeles Times.

Photo of Spirit's partially buried wheels on May 6: NASA/JPL-Caltech