In this photo released July 19, 2011 by NASA showing NASA's Mars Exploration Rover Opportunity. Months after the death of the Mars rover Spirit, its surviving twin Opportunity, is poised to reach the ... more 
In this photo released July 19, 2011 by NASA showing NASA's Mars Exploration Rover Opportunity. Months after the death of the Mars rover Spirit, its surviving twin Opportunity, is poised to reach the rim of a vast crater to begin a fresh round of exploration. (AP Photo/NASA/JPL) less 
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Associated Press | Photo By NASA/JPL
Mon, Aug 8, 2011 12:06 AM EDT