Triton's Evolution with a Primordial Neptunian Satellite System

Abstract

The Neptunian satellite system is unusual. The major satellites of Jupiter, Saturn, and Uranus are all in prograde, low-inclination orbits. Neptune on the other hand, has the fewest satellites, and most of the system’s mass is within one irregular satellite, Triton. Triton was most likely captured by Neptune and destroyed the primordial regular satellite system. We investigate the interactions between a newly captured Triton and a prior Neptunian satellite system. We find that a prior satellite system with a mass ratio similar to the Uranian system or smaller has a substantial likelihood of reproducing the current Neptunian system, while a more massive system has a low probability of leading to the current configuration. Moreover, Triton’s interaction with a prior satellite system may offer a mechanism to decrease its high initial semimajor axis fast enough to preserve small irregular satellites (Nereid-like) that might otherwise be lost during a prolonged Triton circularization via tides alone.