South Pole–Aitken (SPA) is the largest and oldest recognized impact basin on the Moon. Located on the farside hemisphere, SPA is nearly antipodal to the nearside geochemical province referred to as the Procellarum KREEP Terrane (PKT). The PKT signifies an unexplained lunar surface compositional asymmetry of KREEP , a geochemical component named for its enrichment in incompatible elements including potassium (K), rare earth elements (REE), and phosphorous (P).
Through our work published in Science Advances, we demonstrate that impact-induced mantle heating from the SPA basin-forming event would have greatly influenced lunar interior dynamics and generated a subsurface hemispheric compositional asymmetry closely aligned with the present location of the PKT. Such a subsurface asymmetry provides an origin for the Moon’s surface geochemical asymmetry, in particular, the presence of the PKT and the majority of lunar maria on the nearside hemisphere.