On Earth Day Astronauts Dr. Ed Lu, Tom Jones, and Bill Anders announced that between 2000 and 2013, the Nuclear Test Ban Treaty Organization Network detected 26 explosions on Earth ranging in energy from 1-600 kilotons of TNT. None of them were caused by nuclear explosions, but rather by asteroid impacts. Most of these asteroids exploded high in the atmosphere and did no damage on the ground. These data provide a measure of the frequency at which large space rocks enter our atmosphere.