Investigations of asteroid family geology

Abstract

A persistent problem in asteroid science is the continuing dispute over the assignment of asteroids to dynamical families. The recently proposed asteroid family classifications of Williams 1989 and Zappala et al. 1990 are evaluated by means of spectral reflectance data. The basic premise of this evaluation is that a "real" asteroid family is the product of a singular impact disrupted parent body. A variety of parent body models can be derived by interpreting asteroid spectral observations in terms of meteorite geochemistry. Each of the asteroid families are tested by comparing their members' observed compositions with those of the parent body models. The Zappala et al. 1990 analysis appears to be closer to "reality" than that of Williams 1989 in terms of the number of well-defined families, but the assignment of a particular asteroid to a given parent body is somewhat uncertain due to the presence of preexisting background asteroids in even the most well-defined families. Combining spectral and orbital data holds considerable promise in resolving the family problem, but a greatly expanded spectral data base is necessary.