Near-Earth object the largest explosion in recorded history, equivalent to 20,000 megatons of TNT. It attracted widespread attention because it was discovered only after the closest approach. In March 1998, early orbit calculations for recently discovered asteroid showed a potential 2028 close approach from the Earth, well within the orbit of the Moon, but with a large error margin allowing for a direct hit. Further data allowed a revision of the 2028 approach distance to , with no chance of collision. By that time, inaccurate reports of a potential impact had caused a media storm. From the late 1990s, a typical frame
Origin of the Moon of the present size of Earth, and another the diameter of Mars (half of the terrestrial radius and a tenth of its mass). The colliding body has sometimes been referred to as Theia, the mother of Selene, the Moon goddess in Greek mythology. This size ratio is needed in order for the resulting system to have sufficient angular momentum to match the current orbital configuration. Such an impact would have put enough material into orbit around Earth to have eventually accumulated to form the Moon. Computer simulations show a need for a glancing blow, which causes a portion of the