Host: The Japanese Society for Planetary Sciences: Local Organizing Committee for 2006 Fall Meeting
Recent observations suggest that many of small asteroids (100m $<$ R $<$ 100km) may be gravitational aggregates.Since collisions change the spin of these asteroids, their spin distribution would provide useful information about their origin and collisional evolution.However, little has been studied on the efficiency of angular momentum transfer during collision between rubble pile objects.Using N-body method to simulate impact event between rubble pile objects, we have examined transfer of angular momentum to a target (or the largest remnant if the impact is disruptive) from the orbital angular momentum of an impactor. Our simulations show low angular momentum transfer efficiency at disruptive collisions, and we found a clear relationship between the angular momentum transfer efficiency and the degree of disruption.Also, we exmined the spin-down effect of the assymetrical ejection of fragments due to the initial spin of the target, and confirmed that the rubble pile objects spin down by collisions.The rotating object spins down proportionally to the amount of mass ejection.In the case that about half the mass of the target is lost by a head-on collision, the target spins down 30-50%.
