writes "Researchers speaking at the American Geophysical Union meeting in Acapulco, Mexico, this week will outline a new theory for the extinction event and subsequent global cooling that occured about 13,000 years ago. From the Guardian: 'A group of US scientists have found a layer of microscopic diamonds at 26 different sites in Europe, Canada and America. These are the remains of a giant carbon-rich comet that crashed in pieces on our planet 12,900 years ago.' According to geophysicist Allen West, the comet was 'about 2km-3km in diameter and broke up just before impact, setting off a series of explosions, each the equivalent of an atomic bomb blast. The result would have been hell on Earth. Most of the northern hemisphere would have been left on fire.'"