Details of the collisions recorded during the integration of a system of 25 000 particles, each with a radius of 50 km. Left panel: temporal distribution of collisions. The inset provides a close-up of the first twenty years of the integration. In this panel, collision times are normalized to the average orbital period of the fragments, P_avg, showing that impacts preferentially occur at multiples of this period. Right panel: distribution of impact velocities between the fragments.