Mare basalt flooding events surrounding Chang'e-4 landing site as revealed by Zhinyu crater ejecta

Abstract

Von Kármán crater's floor was flooded with mare basalts during the Imbrian period. This site is the target of China's ongoing Chang'e-4 mission that includes the Yutu-2 rover and its instrumental payload. The Zhinyu crater, one of the largest craters within a few tens of kilometers from the landing site, is the product of a fresh impact that excavated subsurface, basaltic materials onto the surface. The compositional characteristics of the continuous ejecta around the crater vary radially with distance, suggesting possible mineral heterogeneity at depth. At least three main mare flooding phases could have occurred within Von Kármán, producing a basalt layer of at least 320 m in thickness. However, a broadly consistent olivine composition (Fo#: 55) of the three proposed basalt layers suggests that the sources of the mare basalts would have been similar in composition, perhaps even consisting of a single magma chamber where magma had time to evolve. The Yutu-2 rover that is edging its way westwards, could in principle test this hypothesis, thus further constraining the thermal history of the Von Kármán crater.