On the Origin of Earth's Moon

TL;DR

This paper reviews the Giant Impact hypothesis for the Moon's origin, highlighting recent advances in simulations and disk evolution studies that align with observational data, while noting areas for future research.

Contribution

It synthesizes recent progress in modeling lunar formation, emphasizing the development of an end-to-end theory consistent with chemical, thermal, and dynamical observations.

Findings

Simulations match bulk properties of the Moon.

Recent work explains Moon's chemical composition and thermal history.

Progress towards a comprehensive lunar origin theory.

Abstract

The Giant Impact is currently accepted as the leading theory for the formation of Earth's Moon. Successful scenarios for lunar origin should be able to explain the chemical composition of the Moon (volatile content and stable isotope ratios), the Moon's initial thermal state, and the system's bulk physical and dynamical properties. Hydrocode simulations of the formation of the Moon have long been able to match the bulk properties, but recent, more detailed work on the evolution of the protolunar disk has yielded great insight into the origin of the Moon's chemistry, and its early thermal history. Here, I show that the community has constructed the elements of an end-to-end theory for lunar origin that matches the overwhelming majority of observational constraints. In spite of the great progress made in recent years, new samples of the Moon, clarification of processes in the impact-generated disk, and a broader exploration of impact parameter space could yield even more insights into this fundamental and uniquely challenging geophysical problem.