The Discovery of Arsenic-Based Twitter

Cast your mind back six months, to late November 2010. Wikileaks had unveiled the first goodies from its cache of 250,000 State Department cable. Hosni Mubarak's National Democratic Party was coasting toward yet another easy win in Egyptian elections. And, for just a few days, a lot of us wondered if NASA had discovered aliens.

If you've forgotten about that otherworldly dalliance, today is a good time to refresh your memory. On November 29, NASA announced that it would soon hold a press conference to "discuss an astrobiology finding that will impact the search for evidence of extraterrestrial life." Wild speculation ran amok—perhaps scientists had found living things on one of Saturn's moons. At the press conference, the scientists did not unveil an actual extraterrestrial, but they did have big news. A new paper had just been published in the journal Science, they said, which described bacteria that seemed able to build their own DNA from arsenic. If that were true, it would be an historic discovery, because no such ability has ever been found among Earth's life-forms.