Polar bears in the Beaufort Sea in northern Alaska. Scientist Charles Monnett caused a stir with a 2006 report on polar bears that were drowning, apparently owing to a lack of ice. Steve Amstrup/Fish and Wildlife Service hide caption

itoggle caption Steve Amstrup/Fish and Wildlife Service

NASA says it has found proof that water shaped the rocks on the left, in a photograph taken by the Mars rover Curiosity (left). For comparison, the agency released an image of rocks from Earth (right). NASA hide caption

itoggle caption NASA

The African spiny mouse has the ability to regrow large patches of skin and hair without scarring. Ashley W. Seifert/Nature hide caption

itoggle caption Ashley W. Seifert/Nature

Federally funded chimps at the New Iberia Research Center in Louisiana will retire to either a lab in Texas or a chimp sanctuary in Louisiana. Courtesy of the Humane Society of the United States hide caption

itoggle caption Courtesy of the Humane Society of the United States

Space shuttle Endeavour is towed to the Kennedy Space Center landing facility in Cape Canaveral, Fla., on Friday. John Raoux/AP Photo hide caption

itoggle caption John Raoux/AP Photo

The two Voyager spacecraft launched on Aug. 20 and Sept. 5, 1977, on a mission to explore Jupiter and Saturn. This true-color image, captured by Voyager 2 on July 21, 1981, shows the moons Dione (small dot at left) and Rhea (lower right) near Saturn. NASA/JPL hide caption

itoggle caption NASA/JPL

A rhesus monkey eats watermelon, provided by zookeepers, at the Kamla Nehru Zoological Gardens in India in May 2012. Sam Panthaky/AFP/Getty Images hide caption

itoggle caption Sam Panthaky/AFP/Getty Images

Generating artificial lightning in Nikola Tesla's laboratory. Bettmann/Corbis hide caption

itoggle caption Bettmann/Corbis

A school of Blue Tang fish swimming together off the Caribbean island of Bonaire. It has long been assumed that the schooling behavior of fish evolved in part to protect animals from being attacked by predators. David J. Phillip/AP hide caption

itoggle caption David J. Phillip/AP

National Institute of Allergy and Infectious Diseases Director Dr. Anthony Fauci said a voluntary halt to bird flu research should stay in effect. Chip Somodevilla/Getty Images hide caption

itoggle caption Chip Somodevilla/Getty Images

A government official in Bali, Indonesia, holds a chicken before administering an injection to cull it as a precautionary measure in April to prevent the spread of bird flu. Firdia Lisnawati/AP hide caption

itoggle caption Firdia Lisnawati/AP

Chickens are under quarantine in Tepatitlan, Jalisco State, Mexico. The Mexican government declared a national animal health emergency July 2 in the face of an aggressive bird flu epidemic that has infected nearly 1.7 million poultry. Hector Guerrero/AFP/Getty Images hide caption

itoggle caption Hector Guerrero/AFP/Getty Images