Imperfect Accretion in a GPU-enhanced N-Body Simulator

Accretion during the late stage of terrestrial planet formation is dominated by collisions between planetary embryos—Moon-size to nearly Earth-size bodies. These collisions are not always perfect mergers because they often eject material from the colliding bodies. The projectile may even survive after an oblique impact. Impact outcomes are sorted into several different regimes by the relative impact velocity, the angle of impact, and the mass ratio between the colliding objects. Depending on the type of collision, the post-impact mass of the target and the amount of material ejected can vary widely. Accounting for the large amount of debris generated in some impacts places a significant strain on CPU-only astrophysical N-body integrators, so neglecting the debris is standard practice; however this may lead to inaccurate results. Here, we show an implementation of imperfect accretion in a GPU-enhanced astrophysical N-body integrator (GENGA; Grimm & Stadel, 2014) and how different initial parameters result in different collision types. We expect an increase in the computation time as the simulation progresses due to debris generation. It may be that the inclusion of imperfect accretion into the simulator could have a negligible effect on the outcome if most of the debris is re-accreted soon after each impact, or this could be a significant way of eroding planetary mass and distributing it throughout the Solar System in a new population of planetesimals.