Lunar Accretion from an Impact-Generated Disk

Abstract

We investigate the evolution of a circumterrestrial disk of debris generated by a giant impact on the Earth and the dynamical characteristics of the moon accreted from the disk by using N-body simulation. We find that in most cases the disk evolution results in the formation of a single large moon on a nearly circular orbit close to the equatorial plane of the initial disk just outside the Roche limit. The efficiency of incorporation of disk material into a moon is 10-55%, which increases with the initial specific angular momentum of the disk. These results hardly depend on the initial condition of the disk as long as the disk mass is a few times the present lunar mass and most disk mass exists inside the Roche limit.