A Crater Chronology for the Jupiter’s Trojan Asteroids

Abstract

We present a new crater chronology for Jupiter’s Trojan asteroids. This tool can be used to interpret the collisional history of the bodies observed by NASA’s Lucy mission. The Lucy mission will visit a total of six Trojan asteroids: Eurybates, Polymele, Orus, Leucus, and the near-equal-mass binary Patroclus–Menoetius. In addition, Eurybates and Polymele each have a small satellite. Here we present a prediction of Trojan cratering based on current models of how the solar system and the objects themselves evolved. We give particular emphasis to the time lapsed since their implantation into stable regions near Jupiter’s Lagrangian L4 and L5 points. We find that cratering on Trojans is generally dominated by mutual collisions, with the exception of a short period of time (∼10 Myr) after implantation, in which cometary impacts may have been significant. For adopted crater scaling laws, we find that the overall spatial density of craters on Trojans is significantly lower than that of Main Belt asteroids on surfaces with similar formation ages. We also discuss specific predictions for similar-sized Eurybates and Orus, and the binary system Patroclus–Menoetius.