Dynamical capture in the Pluto-Charon system

TL;DR

This study investigates whether small satellites of Pluto could have been captured from a heliocentric disk and formed through subsequent collisional evolution, concluding that the scenario is unlikely due to long collisional lifetimes.

Contribution

It introduces a dynamical capture model for Pluto's satellites and assesses the feasibility of satellite formation via collisional debris, finding it unlikely.

Findings

Temporary capture is possible with low disk excitation.

Captured objects have highly elliptical orbits and short capture times.

Large objects needed for satellite formation have too long collisional lifetimes.

Abstract

This paper explores the possibility that the progenitors of the small satellites of Pluto got captured in the Pluto-Charon system from the massive heliocentric planetesimal disk in which Pluto was originally embedded into. We find that, if the dynamical excitation of the disk is small, temporary capture in the Pluto-Charon system can occur with non-negligible probability, due to the dynamical perturbations exerted by the binary nature of the Pluto-Charon pair. However, the captured objects remain on very elliptic orbits and the typical capture time is only 100 years. In order to explain the origin of the small satellites of Pluto, we conjecture that some of these objects got disrupted during their Pluto-bound phase by a collision with a planetesimal of the disk. This could have generated a debris disk, which damped under internal collisional evolution, until turning itself into an accretional disk that could form small satellites on circular orbits, co-planar with Charon. Unfortunately, we find that objects large enough to carry a sufficient amount of mass to generate the small satellites of Pluto have collisional lifetimes orders of magnitude longer than the capture time. Thus, this scenario cannot explain the origin of the small satellites of Pluto, which remains elusive.