Spirit, one of the twin Mars rovers that have patrolled the Red Planet since 2004, appears to have suffered another glitchy episode. The rover team is trying to figure out why Spirit rebooted itself at least twice over the weekend; in January the rover perplexed its handlers when it failed to respond to commands and did not record its activities for a spell.

As the rover bounced information to and from Earth, some of its communications were interrupted; Spirit appears to have rebooted while it was using an antenna that allows direct contact with Earth.

"While we don't have an explanation yet" for the glitches, Spirit appears to be fully powered and within its temperature bounds, project manager John Callas of the NASA Jet Propulsion Laboratory in Pasadena, Calif., said in a statement. "The rover is in a stable operations state called automode and taking care of itself. It could stay in this stable mode for some time if necessary while we diagnose the problem."

Such wonky moments are to be expected of the Mars rovers, which have dramatically outlasted their original three-month missions. Spirit's advanced age shows in its hardware as well as in its erratic behavior: the rover has been dragging a broken wheel since 2006.

"We are aware of the reality that we have an aging rover, and there may be age-related effects here," Callas said.

Both rovers continue to investigate the Red Planet: Spirit is limping around a surface feature known as "Home Plate," while its more able-bodied twin Opportunity is on an ambitious trip to the distant Endeavour Crater. If Opportunity can traverse the more than seven miles (12 kilometers) to Endeavour, it will have more or less matched the total mileage from its first five years of exploration.

Panorama of "Home Plate" taken by Spirit in February: NASA/JPL-Caltech