The eccentricity evolution of particles orbiting a central gravity with GM = 1. Relatively inelastic collisions, with coefficient of restitution ϵ = 0.3, evolve towards an equilibrium eccentricity of 10^-3, with orbital excursions comparable to the grid spacing. More elastic collisions, with ϵ = 0.6, lead to catastrophic heating of the particle system. The results follow closely Fig. 1 of Lithwick & Chiang (2007).