A South Pole–Aitken impact origin of the lunar compositional asymmetry

• Published in: Science Advances
• Main Authors: Jones, Matt J., Evans, Alexander J., Johnson, Brandon C., Weller, Matthew B., Andrews-Hanna, Jeffrey C., Tikoo, Sonia M., Keane, James T.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Association for the Advancement of Science (AAAS) 2022
• Subjects: South pole
• Online Access: http://dx.doi.org/10.1126/sciadv.abm8475; https://www.science.org/doi/pdf/10.1126/sciadv.abm8475

The formation of the largest and most ancient lunar impact basin, South Pole–Aitken (SPA), was a defining event in the Moon’s evolution. Using numerical simulations, we show that widespread mantle heating from the SPA impact can catalyze the formation of the long-lived nearside-farside lunar asymmetry in incompatible elements and surface volcanic deposits, which has remained unexplained since its discovery in the Apollo era. The impact-induced heat drives hemisphere-scale mantle convection, which would sequester Th- and Ti-rich lunar magma ocean cumulates in the nearside hemisphere within a few hundred million years if they remain immediately beneath the lunar crust at the time of the SPA impact. A warm initial upper mantle facilitates generation of a pronounced compositional asymmetry consistent with the observed lunar asymmetry.