A number of 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. Astrogeology scientist, Ken Herkenhoff and Scientist Emeritus 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 rover missions have greatly contributed to scientific studies of Mars. Missions of both rovers were extended beyond the initial three month mission plan. Spirit's mission officially ended 25 May 2011, but the USGS continues to use images taken during its time on Mars. Opportunity's mission continues, assisting in more great science!