The largest meteorite strike in recorded history was in 1908, also over Russia. Know as the "Tunguska event," the blast from the impact was more powerful than the atomic bomb dropped on Hiroshima. It leveled millions of trees, but miraculously, no one was killed. If a similar impact happened over a metropolitan area, the city would be destroyed. "It's a global challenge and we need to find a solution together," says European Space Agency spokesman Bernhard von Weyhe.