  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.
