So far, Nasa has successfully acquired four Mars rovers: the
Mars Pathfinder, Sojourner, Opportunity, and the Spirit. These were
managed by the Jet Propulsion Laboratory and the Mars Science
Laboratory.
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Mars Science Laboratory (a.k.a. Curiosity)
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The probe "Mars Science Laboratory" (MSL) and its rover,
Curiosity, were launched on November 26, 2011 and were scheduled to
arrive at Mars in August, 2012.
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The Mars Exploration Rovers (Spirit and Opportunity) and the Mars Science Laboratory rover (Curiosity) use the VxWorks operating system.