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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Texas Find Turns Back Clock On Settlers In America

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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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Explainer: What Are Spent Fuel Rods?

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Japan Nuclear Plant Rocked By Second Blast

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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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Lab Vs. Courtroom: Different Definitions Of Proof

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Scientists Doubt Meteorite Carried Life To Earth

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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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For Turtles, Earth's Magnetism Is A Built-In GPS

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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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Fungus Knocks Out Malaria In Mosquitoes

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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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Hibernating Bears 'A Metabolic Marvel'

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Hazardous materials experts enter the Hart Building of the U.S. Senate on Nov. 7, 2001, in Washington. The building was closed after an anthrax-laced letter was found in then-Sen. Tom Daschle's office. Stephen Jaffe/AFP/Getty Images hide caption

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FBI Faulted For Overstating Science In Anthrax Case

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Fleas push off the ground from the ends of their legs, not from the part of the leg that resembles a knee. Gregory Sutton hide caption

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Itching To Know How Fleas Flee? Mystery Solved

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Researchers have sequenced the genome of the common water flea, Daphnia, shown in this false-color micrograph. About 35 percent of the genes are brand new to science. Jan Michels/Christian-Albrechts-Universitat zu Kiel hide caption

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Tiny Water Flea Clocks In Record Number Of Genes

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With just 600 residents and no cities, Sark, located about 80 miles off the coast of England in the English Channel, is the first dark-sky island. Phllip Capper/Flickr hide caption

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The space shuttle Challenger explodes shortly after lifting off from the Kennedy Space Center in Cape Canaveral, Fla., on Jan. 28, 1986. Bruce Weaver/AP hide caption

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Lessons Linger 25 Years After Challenger Tragedy

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