Investigating the onset of multi-ring impact basin formation

Abstract

Multi-ring basins represent some of the largest, oldest, rarest and, therefore, least understood impact crater structures. Various theories have been put forward to explain their formation; there is currently, however, no consensus. Here, numerical modeling is used to investigate the onset of multi-ring basin formation on the Moon using two thermal profiles suitable for the lunar basin-forming epoch. Various multi-ring basin formation hypotheses are discussed, compared, and evaluated against target deformation and strain distribution in the models, as well as geological and geophysical observations. The mechanism that most closely resembles the numerical models in terms of basin formation and structure, as well as observations, appears to be the ring tectonic theory, whereby ring formation is dependent on transient cavities penetrating entirely through the Moon’s lithosphere into the asthenosphere below. The numerical models suggest that all lunar basins larger than Schrödinger (320km diameter) should be capable of forming multiple rings, as their transient cavities penetrate into the asthenosphere for both thermal profiles. Additionally, the models demonstrate that the target’s thermal profile starts to influence basin formation and structure when impact energy exceeds that of the Schrödinger event.