Beijing – Scientists have confirmed a consistent rate of meteorite impacts across both the near and far sides of the Moon, a finding enabled by analysis of samples returned to Earth by China’s Chang’e-6 mission in June 2024. The research, published in Science Advances on February 4th, revises decades-old models of lunar chronology and provides a crucial anchor point for understanding the Moon’s early geological history.
The Chang’e-6 mission successfully retrieved 1,935 grams of lunar material from the Apollo Basin, located within the South Pole-Aitken Basin on the Moon’s far side. Analysis of these samples revealed two key rock types: basalt dated to 2.807 billion years old and norite formed 4.25 billion years ago. The norite originated from magma crystallized after the impact that created the South Pole-Aitken Basin, the largest and oldest impact structure on the Moon.
For decades, lunar age estimations relied on counting impact craters, assuming a higher density indicated an older surface. However, this method was limited by the availability of samples exclusively from the Moon’s near side, with the oldest specimens dating back only 4 billion years. This geographical bias fueled debate regarding the Moon’s early impact history, including the controversial Late Heavy Bombardment (LHB) hypothesis.
The modern analysis, conducted by a team led by the Chinese Academy of Sciences’ Institute of Geology and Geophysics, demonstrates a uniform impact flux across both lunar hemispheres. This finding challenges previous suggestions of differing impact rates between the near and far sides. Researchers also found evidence that early lunar impact events followed a gradual decline, rather than the dramatic fluctuations previously proposed.
High-precision isotope analysis of the Chang’e-6 basalt samples revealed minute variations that captured traces of the major impact event that formed the South Pole-Aitken Basin. Scientists determined the impact also heated materials deep within the Moon, leading to the loss of volatile elements. This provides insight into how large impacts affected the Moon’s interior and reshaped its surface.
The findings are particularly relevant as international space agencies, including China, NASA, and the European Space Agency, plan future lunar missions and potential base construction in the South Pole-Aitken Basin, drawn by the presence of permanently shadowed regions containing significant quantities of water ice. The revised lunar chronology model will be essential for accurately dating geological features and understanding the environment in this region.
The Institute of Geology and Geophysics collaborated with the CAS Aerospace Information Research Institute on the study. No immediate comment was available from NASA regarding the implications of the findings for planned Artemis missions.
