February 2, 2010: Something awfully curious is happening 100 million miles from Earth in the asteroid belt. There's a newly discovered object that superficially looks like a comet but lives among the asteroids. The distinction? Comets swoop along elliptical orbits close in to the Sun and grow long gaseous and dusty tails, as ices near the surface turn into vapor and release dust. But asteroids are mostly in circular orbits in the asteroid belt and are not normally expected to be "volatile."
The mystery object was discovered on January 6, 2010, by the Lincoln Near-Earth Asteroid Research (LINEAR) sky survey. The object appears so unusual in ground-based telescopic images that discretionary time on NASA's Hubble Space Telescope was used to take a close-up look. The observations show a bizarre X-pattern of filamentary structures near the point-like nucleus of the object and trailing streamers of dust. This complex structure suggests the object is not a comet but instead the product of a head-on collision between two asteroids traveling five times faster than a rifle bullet. Astronomers have long thought that the asteroid belt is being ground down through collisions, but such a smashup has never before been seen.See the rest: