Rubble Pile Asteroids

TL;DR

Rubble pile asteroids are loosely bound, porous bodies formed through collisional evolution, with their internal structure inferred from indirect observations and their dynamic properties.

Contribution

This paper synthesizes observational and theoretical evidence to characterize the internal structure and formation history of rubble pile asteroids.

Findings

Most near-Earth asteroids are likely rubble piles.

Rubble pile structure results from collisional evolution.

Internal composition is inferred from shape, spin, and impact evidence.

Abstract

The moniker rubble pile is typically applied to all solar system bodies with Diameter between 200m and 10km - where in this size range there is an abundance of evidence that nearly every object is bound primarily by self-gravity with significant void space or bulk porosity between irregularly shaped constituent particles. The understanding of this population is derived from wide-ranging population studies of derived shape and spin, decades of observational studies in numerous wavelengths, evidence left behind from impacts on planets and moons and the in situ study of a few objects via spacecraft flyby or rendezvous. The internal structure, however, which is responsible for the name rubble pile, is never directly observed, but belies a violent history. Many or most of the asteroids on near-Earth orbits, and the ones most accessible for rendezvous and in situ study, are likely byproducts of the continued collisional evolution of the Main Asteroid Belt.