PHOTOS: The Ever-Mysterious Landscape of Mars

Scientists believe a canyon might have been a lake before Mars dried up.

The Ever-Mysterious Landscape of Mars

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This computer-enhanced image shows Victoria Crater on Mars, where NASA's Mars Exploration Rover Opportunity has been perched on a rim. Mission controllers decided to send the rover down into the crater, knowing there was a risk it could not get back out. (NASA/JPL/Cornell/Univ. of Ariz./US Geological Survey)
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