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D.J. Lien (Washington and Jefferson College/Vanguard Research, Inc.)
The consequences of the collisional history of the asteroid belt have been alluded to in a recent spate of TV shows and movies. The earthly threat in most scenarios is a consequence of a collision between a comet and an asteroid, with the subsequent orbital shift of the collisional products into an Earth-bound trajectory. Fortunately, the reality is that collisions of this magnitude are rare. However, smaller, non-disruptive collisions are far more frequent, as evidenced by the heavily cratered surfaces of Gaspra and Ida.
Recently, deep surveys have found several faint "comets" with no discernible coma and a thin dust "tail" oriented along the orbit. One, C/Elst-Pizarro, has also been identified with a main belt asteroid (1979VA). Numerical models of these "tails" using a Monte Carlo dust ejection computer simulation shows that the dust is ejected at much lower velocities than found for typical comets (1 - 50 m/s) and that the radiation pressure parameter, beta, is consistent with particles much larger than typically found in the tails of active comets.
The most likely interpretation of these results is that the observed dust is a result of a cratering event on the surface of the parent body: the low velocities are consistent with numerical cratering models and the lack of a gas coma or higher beta particles precludes normal comet dust emission models.
I will present the results of the numerical simulations of a number of objects, including 1979VA, currently classified as comets, but which are most likely the result of the dust emission from a cratering event. For each object, the range of impact dates, approximate mass of dust in the debris trail, and ejection velocities will be presented, and the significance of these results in terms of the collisional history of the asteroid belt and new movie scripts will be discussed.
The author(s) of this abstract have provided an email address for comments about the abstract: lien@vrisv.com