H5N1 avian flu viruses (seen in gold) grow inside canine kidney cells (seen in green). Cynthia Goldsmith/CDC hide caption

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NASA's next Mars rover, Curiosity, seen in this artist's rendering, will use 8 pounds of plutonium-238 as its power supply. That's a significant portion of the remaining space fuel. NASA and the Department of Energy have offered to split the costs of producing the fuel, but Congress has so far opposed that arrangement. NASA hide caption

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A researcher who wrote a famous report about dead polar bears was asked to take a polygraph test by a federal agent who has been investigating allegations of scientific misconduct. Above, a polar bear rests with her cubs on pack ice in the Beaufort Sea in northern Alaska.

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A museum employee stands beneath a mastodon skeleton on display at the U.S. National Museum, now the Smithsonian National Museum of Natural History, circa 1917. A new study revisits an old debate about the evidence for an early mastodon hunt in North America.

Smithsonian Institution Archives hide caption

itoggle caption Smithsonian Institution Archives

A researcher who wrote a famous report about dead polar bears is being re-interviewed by federal investigators, who are continuing to probe allegations of misconduct. Above, a polar bear walks on the frozen tundra on the edge of Hudson Bay.

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Naked mole rats are becoming more popular in research laboratories, The rodents have surprised scientists with their ability to live up to 30 years and their potential to offer insights into human health.

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Victims of the plague are consigned to a communal burial during the Plague of London in 1665.

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The main ring of the Tevatron, seen in a time exposure. For a quarter century, the particle accelerator at a lab outside Chicago was the most powerful machine of its kind in the world. Reidar Hahn/Fermilab hide caption

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This picture of the Eros asteroid is the first of an asteroid taken from an orbiting spacecraft. The crater at the center is about 4 miles across. JPL/JHUAPL/NASA hide caption

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This artist's conceptual image shows the Upper Atmosphere Research Satellite, or UARS. After two decades in orbit, the satellite will make an uncontrolled re-entry into the Earth's atmosphere. NASA hide caption

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A view inside the Tevatron ring, currently in its final days as a particle superhighway. Reider Hahn/Fermilab hide caption

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Two polar bears spar on the shoreline of the Hudson Bay in November 2007. Paul J. Richards/AFP/Getty Images hide caption

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"Shrimp on a treadmill" has become a euphemism for questionable government spending on scientific research. The actual research study was focused on how water quality affects a shrimp's performance. Lou Burnett/College of Charleston hide caption

itoggle caption Lou Burnett/College of Charleston

A look inside the Dark Energy Camera shows the 74 blue-tinged sensors that detect light. The camera will survey distant, faint galaxies to learn more about dark energy. Reidar Hahn/Fermilab hide caption

itoggle caption Reidar Hahn/Fermilab