FORMATION AND EVOLUTION OF PLUTO’S SMALL SATELLITES

Abstract

Pluto's system of five known satellites is in a puzzling orbital configuration. Each of the four small satellites are on low-eccentricity and low-inclination orbits situated near a mean motion resonance with the largest satellite Charon. The Pluto–Charon binary likely formed as a result of a giant impact, and so the simplest explanation for the small satellites is that they accreted from the debris of that collision. The Pluto–Charon binary has evolved outward since its formation due to tidal forces, which drove them into their current doubly synchronous state. Meanwhile, leftover debris from the formation of Charon was not initially distant enough from Pluto–Charon to explain the orbits of the current small satellites. The outstanding problems of the system are the movement of debris outward and the small satellites' location near mean motion resonances with Charon. This work explores the dynamical behavior of the collisionally interacting debris orbiting the Pluto–Charon system. While this work specifically tests initial disk and ring configurations designed to mimic the aftermath of the disruption of satellites by heliocentric impactors, we generally find that collisional interactions can help move material outward and keep otherwise unstable material dynamically bound to the Pluto–Charon system. These processes can produce rings of debris whose orbits evolve rapidly due to collisional processes, with increasing pericenters and decreasing semimajor axes. While these rings and disks of debris eventually build satellites that are significantly farther out than the initial locations of a disrupted satellite, they do not show a strong preference for building satellites in or near mean motion resonances with Charon under a wide array of tested conditions.