This concept illustration for the Kennedy Space Center Visitor Complex shows how a space shuttle might be displayed, if NASA decides to award one to the facility. PGAV Destinations/Kennedy Space Center hide caption

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Space shuttle Discovery ended its 39th and final mission to space Wednesday, touching down at Kennedy Space Center in Cape Canaveral, Fla., just before noon local time. John Raoux/AP hide caption

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Space shuttle Discovery lifts off at Kennedy Space Center in Cape Canaveral, Fla., on Thursday for the final time. The world's most traveled spaceship is heading toward the International Space Station with a crew of six on a journey that marks the beginning of the end of the shuttle era. Chris O'Meara/AP hide caption

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Discovery leaves the International Space Station on June 11, 2008. NASA hide caption

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IBM's Watson computer system competes in a Jeopardy! practice round on Jan. 13 against two of the show's most celebrated contestants: Ken Jennings and Brad Rutter. IBM hide caption

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The Tennessee coneflower is listed under the U.S. Endangered Species Act. A hybrid version of the plant, a cross between the Tennessee coneflower and the purple coneflower, was created in 2003. But experts warn that the new plant could pose a significant risk if it encroaches on the historical range of the Tennessee coneflower. J.S. Peterson/USDA hide caption

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The SpaceX Falcon 9, carrying a Dragon capsule, lifts off the launch pad at Launch Complex 40 at Cape Canaveral on Dec. 8, 2010. NASA hide caption

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These primitive tools were found on the eastern edge of the Arabian Peninsula, outside the range of Neanderthals. Researchers say humans may have left Africa earlier than previously thought, crossing what is now the bottom of the Red Sea. Science/AAAS hide caption

itoggle caption Science/AAAS

A recent survey of microbiologists across the country documented 13 episodes of microbial destruction involving viral, bacterial and fungal strains. iStockphoto.com hide caption

itoggle caption iStockphoto.com

It was Christiane Benson's diagnosis with juvenile Batten disease in 2008 that inspired her parents to start the Beyond Batten Disease Foundation and to develop the universal carrier screening test. Courtesy of Charlotte Benson hide caption

itoggle caption Courtesy of Charlotte Benson

A robotic sub found an underwater mountain range beneath Pine Island Glacier. British Antarctic Survey hide caption

itoggle caption British Antarctic Survey

An oiled white ibis lands on an island in Barataria Bay off the coast of Louisiana June 8. Charlie Riedel/AP hide caption

itoggle caption Charlie Riedel/AP