Not just gas: How solids-driven torques shaped the migration of the Galilean moons

Context. A crucial aspect of formation models for the Galilean moons of Jupiter is that the objects survive rapid inward orbital migration. Aims. The primary aim of this study is to investigate the orbital migration of the Galilean moons by incorporating self-consistent solid dynamics in models of circumjovian disks. Methods. We performed two-fluid simulations using the code FARGO3D on a 2D polar grid. The simulations modeled a satellite with the mass of a protomoon, Europa, or Ganymede that interacts with a circumjovian disk. The dust component, coupled to the gas via a drag force, was characterized by the dust-to-gas mass ratio ( ϵ ) and the Stokes number ( T s ). Results. The effect of solids fundamentally alters the evolution of the satellites. We identified a vast parameter space in which migration is slowed, halted, robustly reversed (leading to outward migration), or significantly accelerated inward. The migration rate is dependent on satellite mass. This provides a natural source of differential migration. Conclusions. Solid dynamics provides a robust and self-consistent mechanism that fundamentally alters the migration of the Galilean moons. This might address the long-standing migration catastrophe. This mechanism critically affects the survival of satellites and might 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 the shaping of the final architecture of satellite systems.