Evolution of a terrestrial multiple-moon system

The currently favored theory of lunar origin is the giant-impact hypothesis. Recent work that has modeled accretional growth in impact-generated disks has found that systems with one or two large moons and external debris are common outcomes. In this paper we investigate the evolution of terrestrial multiple-moon systems as they evolve due to mutual interactions (including mean motion resonances) and tidal interaction with Earth, using both analytical techniques and numerical integrations. We find that multiple-moon configurations that form from impact-generated disks are typically unstable: these systems will likely evolve into a single-moon state as the moons mutually collide or as the inner moonlet crashes into Earth.