Impact Rates in the Outer Solar System

Previous studies of cometary impacts in the outer solar system used the spatial distribution of ecliptic comets (ECs) from dynamical models that assumed ECs began on low-inclination orbits (≲5°) in the Kuiper Belt. In reality, the source population of ECs—the trans-Neptunian scattered disk—has orbital inclinations reaching up to ∼30°. In Nesvorný et al., we developed a new dynamical model of ECs by following comets as they evolved from the scattered disk to the inner solar system. The model was absolutely calibrated from the population of Centaurs and active ECs. Here we use our EC model to determine the steady-state impact flux of cometary/Centaur impactors on Jupiter, Saturn, Uranus, and their moons. Relative to previous work, we find slightly higher impact probabilities on the outer moons and lower impact probabilities on the inner moons. The impact probabilities are smaller when comet disruption is accounted for. The results provide a modern framework for the interpretation of the cratering record in the outer solar system.