Catastrophic Collisions in the Asteroid Belt — The Identification of Dynamical Families

Abstract

Collisions play a capital role in the Solar System. Moon origin, tilt of Uranus pole axe, planet ring formation, heavy telluric planet surface craterisation, and the actual figure of the asteroid population are due to collisions. Unfortunately, models of collisions lay on laboratory experiments in which the involved targets and projectiles are centimeter sized objects. It is then difficult to apply scale laws to Predict mass, velocity or spin distributions of fragments resulting from a collision between astronomical bodies. Parameters such as the gravitational attraction between the different fragments are not taken into account in laboratory experiment due to the small size of the bodies.

The asteroid population is the best laboratory to study collisions between kilometer sized bodies. The origin and history of asteroids is closely linked to collision occurences, and asteroid families are the final product of a catastrophic break-up of a parent body. The members of an asteroid family are asteroids with a common origin and keeping evidences of the hyper-energetic collision they are issued from. The study of the members of different asteroid families is of great interest in order to stress the collisional models between kilometer sized bodies. Moreover the knowledge of the number of asteroid families will allow us to know the number of planetesimals in the early times of the Solar System formation and hence will permit to stress the models of Solar System formation. The first step of these studies is to determine the asteroid families and to have a list of family members on which later studies will be carried out. The aim of this chapter is to described two methods of asteroid family determination based on dynamical considerations. These totally independent methods allow to give a level of confidence to family members against chance fluctuations and so propose a reliable list of members for which physical and chemical (spectroscopy) parameters will be investigated.