These observations contrast sharply with the findings of Mars rover Opportunity, which landed on a different part of Mars in 2004 and is still chugging along.

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"You take what Mars gives you, " said Squyres, also the lead scientist on the Mars Exploration Rover Mission, which includes Spirit and Opportunity.

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Before Curiosity, NASA's big rover project was the Mars Exploration Rover Mission: two golf-cart-sized rovers called Spirit and Opportunity.

CNN: What we've done on Mars, and what's next

The rover is built to run for two years, but a previous rover, Opportunity, has been working on Mars since 2004, well beyond the three months NASA planned.

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The rover is supposed to run for two years, but a previous rover, Opportunity, has been working on Mars since 2004 -- well beyond the three months NASA planned.

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Having written the rover simulation, driven Opportunity for three years, and practiced in the Mars Yard, Tompkins was at one with her software.

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Opportunity has seen similar small structures out on Mars' Meridiani plains, which the rover team nicknamed "blueberries".

BBC: Opportunity and Curiosity find similar rocks on Mars