Rover Record

NASA's Mars rovers Spirit and Opportunity are closing in on the record for the longest operating probes on Mars. That record is currently held by NASA's Viking Lander-1, which touched down on Mars July 20, 1976-- seven years to the day after the first manned lunar landing-- and maintained contact with Earth for a bit over six years. Actually, it's not clear that Spirit is still operational-- its latest call home was March 31-- but Opportunity is still roving the surface, headed for its next target.

A high percentage of the total number of missions that have aimed for Mars have failed. Getting there is tough. However, as those three efforts demonstrate, if you can get your technology to the surface in one functioning piece, the Martian environment is not so harsh as to disallow extended operations. That's good news for the future of Mars exploration, both robotic and manned.