The Hubble Space Telescope has zoomed in on the potential crash scene of two asteroids in the Asteroid Belt, showing evidence for a never before seen head-on collision.

Discovered on 6 January by the Lincoln Near-Earth Asteroid Research (LINEAR) sky survey, early images raised the question as to whether the object, which appeared to display a long tail of debris, was in fact a comet. Now, close-up images captured by Hubble's new Wide Field Camera 3 on 25 and 29 January reveal a complex X-shaped pattern near the nucleus of the object.

“This is quite different from the smooth dust envelopes of normal comets,” says principal investigator David Jewitt of the University of California, Los Angeles. “The filaments are made of dust and gravel, presumably recently thrown out of the nucleus. Some are swept back by radiation pressure from sunlight to create straight dust streaks. Embedded in the filaments are co-moving blobs of dust that likely originated from tiny unseen parent bodies.”

Curiously, the nucleus of the object, currently known as P/2010 A2, lies outside the dusty halo of material, a phenomena never before seen in a comet. An alternative explanation is that the complex debris tail is the result of a head-on collision between two small rocky asteroids, and not from the vaporization of ice from a comet nucleus that occurs when a comet approaches the Sun. The observed nucleus would therefore be the surviving remnant of this high-speed crash.

“If this interpretation is correct, two small and previously unknown asteroids recently collided, creating a shower of debris that is being swept back into a tail from the collision site by the pressure of sunlight,” says Jewitt. “The filamentary appearance of P/2010 A2 is different from anything seen in Hubble images of normal comets, consistent with the action of a different process.”

The Asteroid Belt records the history of countless ancient collisions and the orbit of P/2010 A2 is consistent with membership in the Flora asteroid family, which was produced by collisional shattering more than 100 million years ago. Until now, however, no such collision has been caught on camera.