Not Just Gas: How Solid-Driven Torques Shaped the Migration of the Galilean Moons

TL;DR

This study demonstrates that solid-driven torques significantly influence the orbital migration of Galilean moons, potentially explaining their current resonant configuration and survival by altering migration rates and directions.

Contribution

It introduces a self-consistent model incorporating solid dynamics into circumjovian disk simulations, revealing their crucial role in satellite migration.

Findings

Solid dynamics can reverse or halt inward migration.

Migration rates depend on satellite mass and solid parameters.

Solid torques can explain the current orbital architecture of Galilean moons.

Abstract

Surviving rapid inward orbital migration is a crucial aspect of formation models for the Jupiter's Galilean moons. The primary aim of this study is to investigate the orbital migration of the Galilean moons by incorporating self-consistent solid dynamics in circumjovian disk models. We perform two-fluid simulations using the FARGO3D code on a 2D polar grid. The simulations model a satellite with the mass of a proto-moon, Europa, or Ganymede interacting with a circumjovian disk. The dust component, coupled to the gas via a drag force, is characterized by the dust-to-gas mass ratio ($\epsilon$) and the Stokes number ($T_s$). The effect of solids fundamentally alter the satellites' evolution. We identify a vast parameter space where migration is slowed, halted, robustly reversed -leading to outward migration-, or significantly accelerated inward. The migration rate is dependent on satellite mass, providing a natural source of differential migration. Solid dynamics provides a robust and self-consistent mechanism that fundamentally alters the migration of the Galilean moons, potentially addressing the long-standing migration catastrophe. This mechanism critically affects the survival of satellites and could offer a viable physical process to explain the establishment of resonances through differential migration. These findings establish that solid torques are a critical, non-negligible factor in shaping the final architecture of satellite systems.