P/2010 A2

First Small-Body Collision between Asteroids

On 6 January 2010, the Lincoln Near-Earth Asteroid Research (LINEAR) project discovered a mysterious X-shaped Solar System body, named P/2010 A2, traveling at 11,000 mph. The object has confused astronomers because it shows characteristics of both an asteroid and a comet. It has the orbit of a main-belt asteroid and the tail of a comet. For this reason, P/2010 A2 was originally listed as a main-belt comet.

Within a month of the discovery, analysis of the images captured by the Hubble telescope suggested that P/2010 A2 was generated from a recent head-on collision between asteroids. It was the first time a small-body collision by asteroids had been observed. The evidence was supported by the position of the object’s nucleus, which is offset from the axis and outside of the dust halo. P/2010 A2 has no sign of an active nucleus, which has caused scientists to believe it was moved in an impact event.

NASA determined that the nucleus was the “surviving remnant of a hypervelocity collision,” when two small and previously unknown asteroids hit. This event created a shower of debris that is being swept back into the tail by the pressure of the sunlight. The X-shaped debris pattern of P/2010 A2 is unusual and has confused scientists.

Before it was determined that P/2010 A2 came from an asteroid collision, some speculated that it may be a rare carbonaceous asteroid located in the inner main belt. If true, this would suggest that there are more volatile-rich asteroids closer to Earth. The orbit of P/2010 A2 is consistent with the Flora asteroid family, which was produced more than 100 million years ago. The Flora family of asteroids may be the source of the K/T impactor, which is the likely culprit in the extinction of the dinosaurs. The discovery of P/2010 A2 has spawned a collection of conspiracy theories regarding the collision hypothesis.