MAIN BELT ASTEROID COLLISION PROBABILITIES AND IMPACT VELOCITIES

A new method for estimating asteroid collision probabilities and impac t velocities (Vedder 1996, Icarus, 123, 436-449) is extended from sing le to multiple targets. It is then applied to estimating collision rat es and velocities of all asteroids in the main belt with each other. T he results obtained are compared with those obtained by previous inves tigators using other methods. The new method yields main belt collisio n probabilities about 10-15% higher than earlier results, and the impa ct velocity distribution is shifted downward by about 20%. Analysis of the velocity components shows that the most significant difference is in the component normal to the plane of the ecliptic, with the new me thod yielding a higher likelihood of this Z component having a low mag nitude. The nonnormal distribution of the Z component in previous resu lts may be due to underestimating the collision probability for nearly coplanar or nearly tangent orbits. For these frequently occurring cas es, the new method may well have advantages, because it is singularity -free and does not depend on an elaborate and very sensitive analytica l model of the geometry of close encounters. (C) 1998 Academic Press.