The effect of falling particles on the shape and spin rate of an asteroid

Pulkovo Astronomical Observatory, 65/1 Pulkovskoje shosse, 196140 St.-Petersburg, Russian; Isaac Newton Institute of Chile, St. Petersburg Branch e-mail: olyaov@mail.ru

Received: 31 January 2002
Accepted: 25 February 2003

Abstract

This simulation is focused on the specific influence of the gravitational field of a very elongated rotating asteroid on the location of zones of the most intensive bombardment by falling particles. It is assumed that the particles are distributed uniformly in the space surrounding the asteroid. The asteroid shape is approximated by a triaxial ellipsoid with semiaxes 28,12,10.5 (equal to those of asteroid 243 Ida) and by a dumb-bell of the same mass. The computations and appropriate figures show that at a rotation period faster than approximately 9.1 hours for the triaxial ellipsoid model and 3.3 hours for the dumb-bell one the leading sides of the asteroid receive a higher flux of impacting particles than the trailing sides while at slower periods the situation is the opposite. The zones of possible erosion are computed depending on the asteroid rotation period and on the ratio of impact and rebound velocities of particles. The contribution of all impacting particles to the angular momentum of the asteroid is computed, which leads to the conclusion that falling out of particles damps the asteroid rotation at any spin period.