Gravitational re-accumulation as the origin of most contact binaries and other small body shapes

Abstract

Asteroids show a variety of shapes, ranging from roundish to elongated to binary systems and ‘contact binaries’ like (25143) Itokawa, the target of the Hayabusa mission (JAXA). These bodies spend most of their time within a collisional system, the asteroid belt, where impact processes are relatively frequent. Speculations on the origin of asteroid shapes invoke mechanisms such as collisions and spin-up effects. N-body numerical simulations of fragment evolution following catastrophic collisions have been recently carried out (Campo Bagatin et al., 2018). In this study the idea that the stochastic process of gravitational re-accumulation may be responsible for many observed asteroid shapes is introduced. Asteroid ‘contact binaries’ are shown to be regularly produced by the gravitational re-accumulation process following catastrophic impact. Similar processes may have occurred in the case of some comets and Trans-Neptunian Objects.