Resonances in the Early Evolution of the Earth-Moon System

Abstract

Most scenarios for the formation of the Moon place the Moon near Earth in low-eccentricity orbit in the equatorial plane of Earth. We examine the dynamical evolution of the Earth-Moon system from such initial configurations. We find that during the early evolution of the system, strong orbital resonances are encountered. Passage through these resonances can excite large lunar orbital eccentricity and modify the inclination of the Moon to the equator. Scenarios that resolve the mutual inclination problem are presented. A period of large lunar eccentricity would result in substantial tidal heating in the early Moon, providing a heat source for the lunar magma ocean. The resonance may also play a role in the formation of the Moon.