Dr. Mark Lemmon, associate professor of Atmospheric Sciences, has played a key role in the journeys of the Spirit and Opportunity rovers since 2003. As of January 4, the Spirit has been at work on Mars for 4 years, which is 3 years and 275 days longer than expected. January 25, Opportunity will celebrate its 4th anniversary on the red planet.  

See associated story in USA Today.

Four years on Mars: Rovers continue to amaze.