Formation of Regular Satellites from Ancient Massive Rings in the Solar System

TL;DR

This paper proposes that most regular satellites in the solar system formed from ancient massive rings spreading beyond the Roche radius, with the process's speed determining satellite system characteristics.

Contribution

It introduces an analytical model linking ring spreading rates to satellite formation, explaining diverse satellite systems across planets.

Findings

Slow spreading leads to multiple satellites with increasing mass outward.

Fast spreading results in a single large satellite.

Uranus and Neptune likely had massive rings that formed their satellites.

Abstract

When a planetary tidal disk -like Saturn's rings- spreads beyond the Roche radius (inside which planetary tides prevent aggregation), satellites form and migrate away. Here, we show that most regular satellites in the solar system probably formed in this way. According to our analytical model, when the spreading is slow, a retinue of satellites appear with masses increasing with distance to the Roche radius, in excellent agreement with Saturn's, Uranus', and Neptune's satellite systems. This suggests that Uranus and Neptune used to have massive rings that disappeared to give birth to most of their regular satellites. When the spreading is fast, only one large satellite forms, as was the case for Pluto and Earth. This conceptually bridges the gap between terrestrial and giant planet systems.