Full-scale models of three generations of NASA Mars rovers show the increase in size from the Sojourner rover of the Mars Pathfinder project that landed on Mars in 1997 (center), to the twin Mars Exploration Rovers Spirit and Opportunity that landed in 2004 (left), to the Mars Science Laboratory rover for a mission to land in 2010 (right).

The Mars Science Laboratory rover is about 9 feet wide, 10 feet long (not counting its robotic arm) and 7 feet tall.

This image was taken in May 2008 at NASA's Jet Propulsion Laboratory, Pasadena, Calif., which has built the real Mars rovers and managed the rover missions for NASA's Science Mission Directorate, Washington. JPL is a division of the California Institute of Technology.