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Mars rovers appear to be shrinking with age! The biggest, baddest, newest rover being built is the Mars Science Laboratory rover (right). It's the size of a small sport-utility vehicle. Still exploring Mars four years after landing are the dune-buggy-sized rovers Spirit and Opportunity (left). The first-generation rover, Sojourner, is the size of a microwave oven.
Why are the rovers getting bigger? The answer is one word: science. The mass and volume of science instruments -- tools the rovers use to study the Martian surface and environment -- have remained fairly constant at about 10 percent. To determine if Mars ever could have supported life, the Mars Science Laboratory rover will travel farther, carry more instruments, and sample more rocks and soils than ever before. Like a car with more gizmos, the newest robotic beast has to evolve to carry all the gear!
Image Credit: NASA/JPL-Caltech