What is the Mars Exploration Rover (MER) program?
Mars Missions in the Twenty-First Century
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The Mars Exploration Rover (MER) program was built on the tremendous success of the Mars Pathfinder mission to explore the surface of Mars using mobile, remotely controlled robotic rovers. The two spacecraft of the MER program, the rovers Spirit and Opportunity, succeeded beyond all expectations, giving us a remarkable and inspiring view of the geology of the Red Planet.