Formation of the Moon and Binary Asteroids

TL;DR

This paper presents a multi-impact model for the formation of the Moon, Charon, and binary asteroids, emphasizing the role of asteroid impacts and a primordial proto-satellite disk, providing explanations for lunar composition and orbital stability.

Contribution

The paper introduces a novel multi-impact formation model that accounts for lunar and binary asteroid features without catastrophic events, highlighting impact-driven ejecta dynamics.

Findings

High efficiency of impact ejecta merging with proto-satellite disk

Explains lunar iron deficiency through impact ejection

Stable satellite orbits formed from impact debris

Abstract

The proposed multi-impact model explains the formation of the Moon, Charon, and binary asteroids without invoking catastrophic cosmic events. The main elements of the new model are as follows: a. A primordial, low-mass proto-satellite disk with prograde rotation existed around the proto-Earth. b. Most of the lunar material was ejected from Earth mantle by numerous impacts of large asteroids. This naturally explains the lunar iron deficiency. c. Collisions between ejecta and particles of the prograde proto-satellite disk stabilize the fragments on satellite orbits. We demonstrate the high efficiency of the multi-impact mechanism: ejecta on prograde orbits readily merges with the prograde proto-satellite disk, whereas retrograde ejecta falls back onto Earth.