Brandee07 writes "Designed for a 90 day mission, the Spirit Mars Rover is starting its 4th year of exploration. Spirit's sister-module, Opportunity, will turn four on Jan 25. 'We never thought we'd still be driving these robots all over Mars,' said Mark Lemmon, a planetary scientist at Texas A&M University and member of the rover science team. 'We joked about driving Opportunity into Victoria Crater, but now we're there, and we're looking at doing even more science. Each day they still work is an amazing one.'"