Modelling Collisions Between Asteroids: From Laboratory Experiments to Numerical Simulations

TLDR: In this article, the authors present a brief review of the current understanding of the fragmentation process of solid bodies and its im- plementation in numerical codes aimed at simulating asteroid break-up events.

Abstract: Thanks to the development of sophisticated numerical codes, a major breakthrough has been achieved in our understanding of the process involved in small body collisions. Such events play a fundamental role in all the stages of the formation and evolution of planetary systems, and more particularly of our Solar System. Laboratory experiments on centimeter-sized targets have been performed to improve our knowledge on this process, but their extrapolation to asteroid scales remains confronted to major difficulties. In this lecture, we present a brief review of our current understanding of the fragmentation process of solid bodies and its im- plementation in numerical codes aimed at simulating asteroid break-up events. The most recent results provided by numerical simulations are also presented. Although our current understanding is still based on several limitations and assumptions, the development of sophisticated numerical codes accounting for the fragmentation of an asteroid and for the gravitational interactions of the generated fragments have allowed to improve greatly our knowledge on the main mechanisms that are at the origin of some observed features in the asteroid belt. In particular, the simulations have demonstrated that, for bodies larger than several kilometers, the collisional process does not only involves the fragmentation of the asteroid but also the gravi- tational interactions between the fragments that are ejected. This latter mechanism can lead to the formation of large agregates by gravitational reaccumulation of smaller fragments, allowing to explain the presence of large members within aster- oid families. Numerical simulations of the complete process have thus been able to reproduce for the first time the main properties of asteroid families, each formed by the disruption of a large parent body, and also to derive some information on the possible internal structure of the parent bodies. A large amount of work remains however necessary to understand in deeper details the physical process as a function of material properties that are relevant to asteroids and to determine in a more quantitative way the outcome properties such as fragments' shapes and rotational states.