Several USGS scientists and specialists have worked with NASA on the planning, day-to-day operation and image processing for Spirit and Opportunity on the Mars Exploration Rover (MER) Project. Two Astrogeology scientists, Ken Herkenhoff and Larry Soderblom, are MER Co-Investigators. Ken Herkenhoff was also the Payload Element Lead (PEL) for the Microscopic Imager.
The Mars Exploration Rover mission launched in the summer of 2003. Rover Spirit landed 3 January 2004, and Rover Opportunity landed 24 January 2004. Both rovers have been very successful and are have had their missions extended beyond the initial three month mission plan. Although Spirit's mission has officially ended, the USGS continues to use and process images taken during its time on Mars.