Science

Researchers claimed in late 2010 that they found bacteria in Mono Lake, Calif., that survived on the poison arsenic in the place of an element thought essential to life. The report was immediately greeted with skepticism from the scientific community. Ben Margot/AP hide caption

A group of harbor porpoises in San Francisco Bay, photographed from the Golden Gate Bridge. Harbor porpoises haven't been seen in the bay since the 1930s. Researchers believe World War II activity may have contributed to their disappearance. The Navy strung a seven-mile underwater net across the mouth of the bay to keep out enemy submarines. William Keener/Golden Gate Cetacean Research hide caption

A Kemp's ridley sea turtle like this one traveled 4,600 miles across the Atlantic ocean in 2008. After being rehabilitated in Portugal, it is being reintroduced into its native Gulf of Mexico waters on Tuesday. US EPA via flickr hide caption

Leonardo DaVinci noted that when trees branch, smaller branches have a precise, mathematical relationship to the branch they sprang from. iStockphoto.com hide caption

Frankincense comes from the Boswellia sacra tree, which grows mainly in the Horn of Africa. The number of trees that produce the fragrant resin could decline by 90 percent in the next 50 years. scott.zona/flickr hide caption

Northern cardinals have higher-pitched songs, but those sounds can get garbled in cities, so they've started to sing a little lower. Dr. Scott M. Lieberman/AP hide caption

The crippled Fukushima Dai-ichi nuclear power station is seen through a bus window on Nov. 12. The four reactors that failed were stabilized this month. David Guttenfelder/AFP/Getty Images hide caption

Indian firefighters attempt to put out a fire as smoke billows out of the historic Taj Mahal Hotel in Mumbai, which was stormed by armed gunmen in November 2008. Indranil Mukherjee/AFP/Getty Images hide caption