Soldiers walk past part of a message written in blood at the site of a massacre at a ranch in northern Guatemala on May 16. The message is a warning to Otto Salguero — the owner of the ranch, according to local media. Guatemalan authorities blame the killings on the Mexican drug cartel Los Zetas.
Moises Castillo/AP
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President Obama, with Facebook CEO Mark Zuckerberg, speaks during a town hall meeting April 20 at Facebook headquarters in Palo Alto, Calif.
Mandel Ngan/AFP/Getty Images
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A study published in the journal Science last December suggested that a bacterium found in California's Mono Lake was able to substitute arsenic for phosphorous. But that conclusion has many critics.
Miss Bliss 55 via Flickr
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