Planetocentric versus heliocentric impacts in the Jovian and Saturnian Satellite System

Abstract

Readily applicable equations are derived for calculating the impact velocities, collision intervals, and cumulative crater frequencies in a satellite system for planetocentric and heliocentric impactors. Observed cumulative crater frequencies in the Saturnian satellite system and a sometimes observed lack of apex‐antapex asymmetry of crater frequencies favor crater‐producing projectiles orbiting initially in elliptic orbits round the parent planet (planetocentric impactors). On the other hand, a sometimes observed asymmetry of crater size distribution and short collision intervals (<104 years) of planetocentric projectiles favor heliocentric impactors. We conclude that cratering on the Jovian and Saturnian satellites is produced by heliocentric projectiles as well as by captured planetocentric impactors. Small satellites could be crushed several times by major impacts and reaccrete from planetocentric orbits.