Numerical Simulations of Granular Asteroid Growth

It is believed that planetesimals and asteroids are created by the accumulation of interstellar dust. However, the processes that govern the collision, agglomeration, and fragmentation of clusters of grains are not well understood. Prior research in the topic has established regimes for the results of conservative collisions of particle clusters held together by contact forces, but neglects gravity, a critical component once particles are no longer touching. We run simulations of clusters of particles modeled as hard frictionless spheres that take into account gravity and dissipation of energy. We obtain outcomes of collisions of two clusters with variable masses, particle counts, velocities, and impact parameters. We then compare our results to other models and simulations, and find that conservative collisions can take place at higher energies than classically predicted.