On the Strength and Disruption Mechanisms of Small Bodies in the Solar System

Abstract

During their evolutions, the small bodies of our Solar System are affected by several mechanisms which can modify their properties. While dynamical mechanisms are at the origin of their orbital variations, there are other mechanisms which can change their shape, spin, and even their size when their strength threshold is reached, resulting in their disruption. Such mechanisms have been identified and studied, by both analytical and numerical tools. The main mechanisms that can result in the disruption of a small body are collisional events, tidal perturbations, and spin-ups. However, the efficiency of these mechanisms depends on the strength of the material constituing the small body, which also plays a role in its possible equilibrium shape. As it is often believed that most small bodies larger than a few hundreds meters in radius are gravitational aggregates or rubble piles, i.e., cohesionless bodies, a fluid model is often used to determine their bulk densities, based on their shape and assuming hydrostatic equilibrium. A representation by a fluid has also been often used to estimate their tidal disruption (Roche) distance to a planet. However, cohesionless bodies do not behave like fluids. In particular, they are subjected to different failure criteria depending on the supposed strength model. This chapter presents several important aspects of material strengths that are believed to be adapted to Solar System small bodies and reviews the most recent studies of the different mechanisms that can be at the origin of the disruption of these bodies. Our understanding of the complex process of rock failure is still poor and remains an open area of research. While our knowledge has improved on the disruption mechanisms of small bodies of our Solar System, there is still a large debate on the appropriate strength models for these bodies. Moreover, material properties of terrestrial rocks or meteorites are generally used to model small bodies in space, and only space missions to some of these bodies devoted to precise in situ analysis and sample return will allow us to determine whether those models are appropriate or need to be revised.