gbrumfiel writes "A meteor that exploded over Russia's Chelyabinsk region this morning was the largest recorded object to strike the earth in more than a century, Nature reports. Infrasound data collected by a network designed to watch for nuclear weapons testing suggests that today's blast released hundreds of kilotons of energy. That would make it far more powerful than the nuclear weapon tested by North Korea just days ago, and the largest rock to strike the earth since a meteor broke up over Siberia's Tunguska river in 1908. Despite its incredible power, the rock evaded detection by astronomers. Estimates show it was likely only 15 meters across — too small to be seen by networks searching for near earth asteroids." Today's meteor event came a day after California scientists proposed a system to vaporize asteroids that threaten Earth. Of course, the process needs to be started when the asteroid is still tens of millions of kilometers away; there's no chance to shoot down something that's already arrived.