DiRAC resource used: DiAL 2.5
PI: G.S. Collins

The ~2500-km diameter South Pole-Aitkin (SPA) basin is the oldest and largest known impact structure in the Solar System. The crater dominates the topography, crustal structure, subsurface density distribution and surface composition of the southern farside of the moon. As the earliest known impact on the Moon, understanding the basin’s formation and its age is key to unlocking the Moon’s history and evolution and is among the highest priority objectives in planetary science. Collecting samples from the basin is a major objective of the Endurance-A lunar rover mission, recently prioritised by NASA’s 2023-2032 Decadal Review, to complement the Artemis program that will land humans in the SPA basin in the next decade.

In this work, we conducted a comprehensive 3D modelling study of the oblique SPA impact that includes a compositionally distinct crust and considers a range of target and impactor properties (Bill et al. 2024). Comparison of simulation results with crustal thickness maps of the basin derived from gravity and topography data have allowed us to establish the impactor size, speed and angle, as well as the near-surface target temperature gradient that best explain the basin’s formation. 

Fig 1: iSALE3D simulation performed on DiRAC DIaL 2.5 of the formation of the giant South Pole-Aitken basin on the farside of the Moon. 

Bill, C.A., Collins, G.S., Davison, T.M., Baijal, N., Kim, D., 2024. Constraining Impact Parameters for the South Pole-Aitken Basin. Presented at the Lunar and Planetary Science Conference, Lunar and Planetary Institute, The Woodlands, Texas, p. 2007. NASA ADS Bibcode: 2024LPICo3040.2007B