An artist's depiction of NASA's Spirit rover on the surface of Mars. Spirit became unresponsive in March 2010. NASA announced it had ended attempts to communicate with the rover on May 24, 2011. NASA hide caption

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Jody Banks displays a selaginella plant at her desk at Purdue University. Banks says selaginella represents an important step in the evolution of plants and produces secondary metabolites that could have medical applications. Andy Jessop/The Purdue Exponent hide caption

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An ash plume rises from the Icelandic volcano Eyjafjallajokull on April 14, 2010. Arni Saeberg hide caption

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Charles Lotter is an operator of Tower Bridge in London and can work all night if a bridge lift is required. Sleep experts say that even people who routinely work night shifts will experience times when they get sleepy in the middle of the night. Peter Macdiarmid/Getty Images hide caption

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In November 1940, just months after its completion, a large section of the Tacoma Narrows Bridge crashed into Puget Sound in Tacoma, Wash. The bridge collapsed under high winds — a failure that shocked engineers at the time. AP hide caption

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Stone artifacts dating back 15,500 years suggest humans may have arrived 2,000 years earlier than previously thought. Courtesy of Michael R. Waters hide caption

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An evacuee is screened for radiation exposure at a testing center on Tuesday in Koriyama city, Fukushima prefecture. Officials are concerned about radiation leaking from the nuclear plant nearby. Wally Santana/AP hide caption

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The FBI used a new DNA fingerprinting technology to analyze the anthrax used in the 2001 mailings. These anthrax spores can live for many years. Janice Haney Carr/CDC Public Health Image Library hide caption

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Researchers used hatchling loggerhead turtles, like this one wearing a special harness, to see how the turtles responded to changing magnetic fields as guides for migration. Courtesy of Nathan Putman hide caption

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Scientists hope to use a fungus to keep malaria-carrying mosquitoes like the Anopheles gambiae species from growing resistant to insecticides. Courtesy of James Gathany/CDC hide caption

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Robert O'Rourke was diagnosed with idiopathic pulmonary fibrosis in late 2006. The lung disease causes scarring in the lungs, which makes breathing difficult. Courtesy of Robert O'Rourke hide caption

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An American black bear from the Kenai Peninsula in Alaska. A new study found that a bear's metabolism in hibernation drops by nearly 75 percent while its body temperature falls just slightly. Oivind Toien/Institute of Arctic Biology, University of Alaska, Fairbanks hide caption

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