This image released by NASA shows an enhanced photo image of Mercury from its Messenger probe's 2008 flyby of the planet. (AP Photo/NASA/Johns Hopkins University Applied Physics Laboratory/Arizona ... more 
This image released by NASA shows an enhanced photo image of Mercury from its Messenger probe's 2008 flyby of the planet. (AP Photo/NASA/Johns Hopkins University Applied Physics Laboratory/Arizona State University/Carnegie Institution of Washington) less 
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Associated Press
Fri, Mar 1, 2013 9:00 AM EST