DEC 31, 2007 - Asteroid Threatens Mars may sound like a B-movie title, but there's a 1-in-75 chance that it will be playing not in the cheap cinema houses, but right up there in the sky for all to see. If it happens - and that's still a long shot, since there's a lot of uncertainty about the orbit of the asteroid in question - it could be as soon as the end of January, 2008. With Mars still retrograde at that point, the Red Planet will still be near enough to Earth that any impact should be clearly discernible with a decent telescope; provided asteroid 2007 WDS strikes the side of Mars facing Earth at the time, and provided you've got a bead on Mars at that moment. (Current calculations make the western part of North America a pretty good seat for the show, if it happens.) Asteroid 2007 WDS was only discovered about six weeks ago at this point, so there's plenty of time for astronomers to refine their estimates as to how close this 160-foot space rock will actually approach Mars. If it hits, it'll be a doozy: about three megatons worth, roughly equivalent to the 1908 Tunguska strike in Siberia. That'd put a half-mile wide crater on Mars, nearly as big as Meteor Crater in Arizona.
