A Magnetized, Moon-Forming Giant Impact

TL;DR

This paper uses advanced simulations to show that magnetic fields significantly influence the dynamics and evolution of the debris disk in the Moon-forming giant impact, affecting Moon formation timescales.

Contribution

It introduces the role of magnetic fields and turbulence in the giant impact scenario, highlighting their effects on disk evolution and Moon formation.

Findings

Magnetic fields are amplified by impact-generated turbulence.

Magnetic turbulence enhances angular momentum transport in the disk.

Magnetic effects accelerate the Moon formation process.

Abstract

The Moon is believed to have formed in the aftermath of a giant impact between a planetary mass body and the proto-Earth. In a typical giant impact scenario, a disk of vapor, liquid, and solid debris forms around the proto-Earth and--after possibly decades of evolution--condenses to form the Moon. Using state-of-the-art numerical simulations, we investigate the dynamical effects of magnetic fields on the Moon-forming giant impact. We show that turbulence generated by the collision itself, shear in the boundary layer between the post-impact debris field and the proto-Earth, and turbulence in the vapor component of the disk amplify the field to dynamically significant strengths. Magnetically driven turbulence promotes angular momentum transport in the protolunar disk. Debris material is accreted onto the proto-Earth, making Moon formation less efficient, while the disk is forced to spread to larger radii, cooling at its outer edge. Magnetic fields speed the evolution of the vapor component of the protolunar disk and hasten the formation of the Moon.