Large impact cratering during lunar magma ocean solidification

K Miljković,M Laneuville,M A Wieczorek,M T Zuber,A Nemchin,P A Bland

doi:10.1038/s41467-021-25818-7

Abstract

The lunar cratering record is used to constrain the bombardment history of both the Earth and the Moon. However, it is suggested from different perspectives, including impact crater dating, asteroid dynamics, lunar samples, impact basin-forming simulations, and lunar evolution modelling, that the Moon could be missing evidence of its earliest cratering record. Here we report that impact basins formed during the lunar magma ocean solidification should have produced different crater morphologies in comparison to later epochs. A low viscosity layer, mimicking a melt layer, between the crust and mantle could cause the entire impact basin size range to be susceptible to immediate and extreme crustal relaxation forming almost unidentifiable topographic and crustal thickness signatures. Lunar basins formed while the lunar magma ocean was still solidifying may escape detection, which is agreeing with studies that suggest a higher impact flux than previously thought in the earliest epoch of Earth-Moon evolution.

Highlights

IntroductionThough the sizes of these basins are similar, based on the diameter of their previously mapped main topographic rings, the older pre-Nectarian basins have a relatively thicker crust in the centre of the basin and lack the distinct crustal thickening between 1 and 2 main rim radii as is observed with younger basins[27,28]
The lunar cratering record is used to constrain the bombardment history of both the Earth and the Moon
A recent reconstruction of the lateaccretion history of the Moon based on impact-delivered siderophile elements has suggested that there could have been as many as 200 basin-forming impacts that formed before 4.35 Ga that are unaccounted for in the current lunar cratering record[19]

Summary

Introduction

Though the sizes of these basins are similar, based on the diameter of their previously mapped main topographic rings, the older pre-Nectarian basins have a relatively thicker crust in the centre of the basin and lack the distinct crustal thickening between 1 and 2 main rim radii as is observed with younger basins[27,28]. Earlier works attributed such differences to long-term viscous flow of materials in the deep crust where temperatures were sufficiently elevated[26,29,30,31].

Methods

Results

Conclusion