Several theories have been advanced to explain the origin of the lunar hemispheric dichotomy – an asymmetry between the nearside and farside hemispheres of the Moon that pervades nearly every global lunar dataset, including topography, gravity, surface geochemistry, and even surface volcanic flows.
The persistence of this global asymmetry across a variety of datasets suggests an ancient mechanism or process that likely occurred within ~500 Myr of lunar formation, yet few comprehensive theories have been proposed that are capable of explaining the full manifestation of the global lunar asymmetry. Of the most commonly recognized theories that have been suggested for the formation of the lunar asymmetry, some are either not supported by recent gravitational and physiographic analyses enabled by returned data from the Gravity Recovery and Interior Laboratory (GRAIL) mission and others could not be fully and satisfactorily evaluated until recently due to insufficient constraints on lunar rheology and chronology.
Fundamentally, the inability to reconcile predictions of the lunar magma ocean with direct observations of the Moon represents a major unanswered question in lunar evolution and highlights the existence of significant uncertainty in the structure and evolution of the Moon. Furthermore, as the Moon serves as the paradigm for magma ocean evolution and magma oceans are expected to have occurred on all differentiated planetary bodies in the inner Solar System (i.e., the Moon, Earth, Mars, Venus, Mercury) as well as other planetesimals (e.g., Vesta), reconciling this discrepancy will aid in our understanding of the post-accretionary evolution of planetary bodies throughout the Solar System.
For this work, we jointly investigate the evolution of a post-magma-ocean lunar structure in a dynamic early Solar Systetm environment. We use well-established numerical models – CitcomS, a 3D thermochemical evolution code, iSALE, a 2D/3D impact modeling code, and COMSOL Multiphysics®, a 1D/2D/3D multiphysics code.