THE AGE OF THE VERITAS ASTEROID FAMILY DEDUCED BY CHAOTIC CHRONOLOGY

ASTEROID families are groups of objects produced in disruptive collisi ons of a parent body. Although family members are widely dispersed in real space, they cluster in the parameter space defined by their so-ca lled proper elements, and can thus be distinguished from the backgroun d asteroid population(1-3). For most asteroids, these parameters are v ery close to being invariants of motion and families are still apparen t billions of years after their formation(4,5). But these parameters u ndergo chaotic diffusion, and in some cases the rate of diffusion migh t be large enough that a family member exits from the region of proper -element space occupied by the family after a characteristic time whic h is shorter than the lifetime of the Solar System. In this case, the characteristic time should provide an approximate upper bound to the a ge of the family. Here we use this 'chaotic chronology' method to esti mate the lifetime of the unusually compact Veritas family. Calculation s of the evolution of the proper elements of the family show that two members (including the largest, 490 Veritas) wander outside the border s of the family on a timescale of about 50 Myr, indicating that the fa mily has an age of less than this.