Accretion from a circumplanetary disk is a primary formation pathway of terrestrial moons, and these disks are an expected outcome of giant impacts, which are ubiquitous in terrestrial planet formation simulations. This is the leading theory for the formation of the Moon. The properties of possible moons formed from post-giant-impact disks naturally depend on properties of the disk, which are inherited from characteristics of the impact such as projectile-to-target mass ratio, impact parameter and velocity, as well as pre-impact rotational states. Here, we report a detailed study of how different properties of a post-giant-impact circumplanetary disk determine the properties of the final moon (or moons).
In order to conduct this study, we modified the Symba N-body integrator to include an inner viscous disk as well as an outer moonetesimal disk, following many of the prescriptions in Salmon & Canup (2012; 2019). We included the effects of viscous evolution of the disk, moonetesimal-disk interactions via Lindblad resonances, and tidal evolution of the moonetesimal orbits. We used this algorithm to conduct a parameter survey exploring the effects of adjusting the properties of a disk about an Earth-like planet. We explored changes to the mass of the circumplanetary disk, the radial extent of the disk, the slope of the surface density distribution of the disk, and the size distribution of the moonetesimals in the disk.
Our investigations have revealed a wide variety of final moons as well as moon systems. We find variations in the final mass and orbit of the surviving moon(s) including the existence of disk criteria for the creation of multiple stable moons. We are continuing our investigation exploring whether different disks grow moons at different rates, how material in the disk is incorporated into the final moon(s), and how the mass of resulting moon(s) changes with the disk’s specific angular momentum.