关键词: 嫦娥六号, 月壤, 南极-艾特肯盆地, 大型撞击, 火山活动, 玄武岩, 撞击熔岩

Abstract: The Chang’e-6 mission has successfully returned samples from the farside of the Moon for the first time, marking a significant milestone in the realm of human lunar exploration. The Chang’e-6 mission successfully landed in the South Pole-Aitken (SPA) basin, one of the Moon’s three major geological terranes. Analysis of the lunar soil samples collected by Chang’e-6 provides valuable insights into the evolutionary history of the Moon’s farside. A new type of rock, designated as impact melt rock, was discovered in the Chang’e-6 soil. Chronological studies on the impact melt rock indicate that the SPA impact may have occurred 4.25 billion years ago, providing a key anchor point for the early impact history of the inner Solar System. The Chang’e-6 soil also contains various types of basalt, including high-alumina basalt erupted 4.2 billion years ago, very-low-titanium basalt erupted 2.9 billion years ago, and low-titanium basalt erupted 2.8 billion years ago. These findings indicate that volcanic activity on the farside lasted for at least 1.4 billion years. The geochemical compositions of the low-titanium basalts indicate that the lunar mantle underlying the SPA basin exhibits characteristics of “ultra-depleted”, “more drier”, “more reduced” and “heavier potassium isotope”, which differ significantly from those observed on the nearside mantle. This finding suggests that the mantle beneath the SPA basin has undergone processes of melt extraction and degassing, likely induced by the SPA impact. Paleomagnetic studies have indicated that the palaeointensities of the Moon rebounded approximately 2.8 billion years ago. When considered as a whole, these findings provide the first insights into the evolutionary history of the Moon’s farside and further support the significant contribution of the SPA impact to the formation of the Moon’s asymmetry.