The Fate of Debris in the Pluto-Charon System

TL;DR

This study uses N-body simulations to explore debris evolution in the Pluto-Charon system, assessing crater formation, debris ejection, and the potential for identifying a collisional family in the Solar System.

Contribution

It provides new insights into debris dynamics, crater formation constraints, and the survivability of a Pluto-Charon collisional family, incorporating planetary migration effects.

Findings

Crater counts may constrain debris disc properties.

Most debris is lost from the Solar System, but some survive as a collisional family.

Planetary migration does not destroy the potential collisional family.

Abstract

The Pluto-Charon system has come into sharper focus following the fly by of New Horizons. We use N-body simulations to probe the unique dynamical history of this binary dwarf planet system. We follow the evolution of the debris disc that might have formed during the Charon-forming giant impact. First, we note that in-situ formation of the four circumbinary moons is extremely difficult if Charon undergoes eccentric tidal evolution. We track collisions of disc debris with Charon, estimating that hundreds to hundreds of thousands of visible craters might arise from 0.3--5 km radius bodies. New Horizons data suggesting a dearth of these small craters may place constraints on the disc properties. While tidal heating will erase some of the cratering history, both tidal and radiogenic heating may also make it possible to differentiate disc debris craters from Kuiper belt object craters. We also track the debris ejected from the Pluto-Charon system into the Solar System; while most of this debris is ultimately lost from the Solar System, a few tens of 10--30 km radius bodies could survive as a Pluto-Charon collisional family. Most are plutinos in the 3:2 resonance with Neptune, while a small number populate nearby resonances. We show that migration of the giant planets early in the Solar System's history would not destroy this collisional family. Finally, we suggest that identification of such a family would likely need to be based on composition as they show minimal clustering in relevant orbital parameters.