A new perspective on the irregular satellites of Saturn - II Dynamical and physical origin

TL;DR

This paper investigates the origin of Saturn's irregular satellites, proposing a collisional capture scenario supported by dynamical modeling and Cassini data analysis, suggesting these satellites may have been captured through impacts within Saturn's sphere of influence.

Contribution

It introduces a collisional capture model for irregular satellites, estimating parent body orbits and impact conditions, and tests this hypothesis on Phoebe using Cassini crater data.

Findings

Range of capture solutions consistent with observations

Parent body orbits align with outer Solar System minor bodies

Cassini data supports collisional capture hypothesis

Abstract

The origin of the irregular satellites of the giant planets has been long debated since their discovery. Their dynamical features argue against an in-situ formation suggesting they are captured bodies, yet there is no global consensus on the physical process at the basis of their capture. In this paper we explore the collisional capture scenario, where the actual satellites originated from impacts occurred within Saturn's influence sphere. By modeling the inverse capture problem, we estimated the families of orbits of the possible parent bodies and the specific impulse needed for their capture. The orbits of these putative parent bodies are compared to those of the minor bodies of the outer Solar System to outline their possible region of formation. Finally, we tested the collisional capture hypothesis on Phoebe by taking advantage of the data supplied by Cassini on its major crater, Jason. Our results presented a realistic range of solutions matching the observational and dynamical data.