Opportunity,which toucheddown on the red planet about 22 days later. At 24 hours and 37 minutes, onesol is slightly longer than one Earth day.

But despitean early softwareglitch and ongoingwheel issues, Spirit continues to return science from "Winter Haven" at itsGusev Crater landing site. The region served as a sort of red planet retreat duringsix months of harsh Martianwinter, Spirit's secondsuch season on Mars.

"We'vegotten through the worst of the winter season," Mapijevic told SPACE.com."Environmentally, we're going to go into another spring season, which is aperiod where the atmosphere tends to change quite a bit on Mars."

Themission continues

Altogether,Spirit has spent more time exploring Mars than the last five International Space Stationastronaut crews spent in Earth orbit. Its robotic twin Opportunity - currently stationed[image]on the other side of Mars at MeridianiPlanum'sare pretty much fine," Mapijevic said.

StevenSquyres, lead scientist for the rover mission at Ithaca, New York's CornellUniversity, has attributed the long life of Spirit and Opportunity to theirrobust design and talented handlers.

"Thesevehicles are 10 times past their warranty," he said in a mission briefing lastmonth on Opportunity's travels. "It is really a remarkable team effort."

Spiritstill has a long way to go before it catches up with the reigning champions ofMartian missions: NASA's Viking1 and Viking 2 landings in 1976.

Viking 2lasted some 1,281 sols, a feat eclipsed by Viking 1's four-Earth year missionthat ended on Nov. 13, 1982. But unlike Spirit and Opportunity, which drawtheir power from solar arrays that can decline over the years, the massiveViking landers used radioisotopethermal generators (RTGs) to generate electricity.

Break timeon Mars

Spirit andOpportunity are