Hugh Pickens writes "According to NASA, a pair of asteroids — one just over three miles wide — passed Earth Tuesday and early Wednesday, avoiding a potentially cataclysmic impact with our home planet. 2012 XE5, estimated at 50-165 feet across, was discovered just days earlier, missing our planet by only 139,500 miles, or slightly more than half the distance to the moon. 4179 Toutatis, just over three miles wide, put on an amazing show for astronomers early Wednesday, missing Earth by 18 lunar lengths, while allowing scientists to observe the massive asteroid in detail. Asteroid Toutatis is well known to astronomers. It passes by Earth's orbit every four years and astronomers say its unique orbit means it is unlikely to impact Earth for at least 600 years. It is one of the largest known potentially hazardous asteroids, and its orbit is inclined less than half-a-degree from Earth's. 'We already know that Toutatis will not hit Earth for hundreds of years,' says Lance Benner of NASA's Near Earth Object Program. 'These new observations will allow us to predict the asteroid's trajectory even farther into the future.' Toutatis would inflict devastating damage if it slammed into Earth, perhaps extinguishing human civilization. The asteroid thought to have killed off the dinosaurs 65 million years ago was about 6 miles wide, researchers say. The fact that 2012 XE5 was discovered only a few days before the encounter prompted Minnesota Public Radio to poll its listeners with the following question: If an asteroid were to strike Earth within an hour, would you want to know?"