P/2010 A2 (Cometary Asteroid)

Location:  Inner Main Asteroid Belt
Asteroid Family:  Flora (Ariadne)
Distance from Sun:  2.3 AU (344 Gm)
Radius:  ~70 meters

Mainstream description
Orbits in the warm inner region of the main Asteroid Belt where its nearest neighbors are dry rocky bodies lacking volatile materials.  However observations of the asteroid show a complex X-pattern of filaments near the main asteroid body or “nucleus and a long comet-like tail of debris trailing over 100,000 kilometers behind it.

“This is quite different from the smooth dust envelopes of normal comets,” says principal investigator David Jewitt of the University of California at 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 originate from tiny unseen parent bodies.”

Another unusual feature is that the nucleus of P/2010 A2 lies outside its own dust halo. This has never before been observed in a comet-like object. It is possible that the complex debris tail is the result of an impact between two bodies rather than ices from a parent body simply turning into vapor. Asteroid collisions are energetic, with an average impact speed of over 11,000 miles per hour (5 km/s, or five times faster than a rifle bullet).

Alternative description
The tails of these objects are the result of electric arc discharges to their surfaces following a charge imbalance between the object and the Sun and the weak but vast electrical field between them.  These discharges are powerful enough to excavate material from the surface of the object explosively at supersonic speeds and even cause the object to break apart.  This material is then accelerated into space and collimated along the object’s filamentary tail.

P/2010 A2 (Cometary Asteroid)Shannon Sims