A meteor exploded in a fireball in the Earth's atmosphere in December—surely a spectacular sight, but no one seems to have seen it. The blast occurred over the Bering Sea, off Russia's Kamchatka Peninsula, the BBC reports. The Air Force notified NASA after military satellites picked up the blast, which took place more than 16 miles from the Earth's surface with 10 times the energy released by the Hiroshima atomic bomb. NASA is checking with airlines to see if there were any sightings. The explosion was the biggest since the one over Chelyabinsk in Russia six years ago; because that blast took place over a city, security and cellphone cameras captured images of it, per the Guardian. NASA said it expects a fireball as big as the December one only two or three times a century.
Small objects often slam into Earth, Brandon Johnson of Brown University tells New Scientist, but can go unnoticed, especially if it happens over an ocean. "If you go out on a clear night, you'll see little meteoroids burning up in the atmosphere," Johnson says. Asteroids roughly 15 feet in diameter to 160 feet seem to hit Earth more often than the data suggests they should. That could mean there are more small meteors arriving than are picked up by telescopes, a situation that will change as technology evolves. "We really should try to track more bodies to smaller sizes so that we have a better understanding of the threat from these kinds of air blasts," Johnson says. (In Michigan, a meteor once caused a small earthquake.)