China achieved a historic milestone in June 2024 when the Chang’e-6 mission successfully returned 1,935.3 grams (approximately 4.25 pounds) of lunar regolith and rock from the Moon. This unprecedented sample return has provided valuable insights into the Moon’s composition and geological history, revealing significant differences between its two hemispheres. The findings are particularly relevant as international space agencies, including NASA and the European Space Agency (ESA), alongside commercial partners, prepare for future lunar bases on the Moon’s far side.
The focus of these upcoming missions is the South Pole-Aitken Basin, a region characterized by numerous permanently shadowed areas that could harbor vast reserves of water ice. The analysis of Chang’e-6 samples addresses several unresolved questions regarding the Moon’s geological evolution, particularly the impact events that shaped its surface. One such event, believed to have created the South Pole-Aitken Basin approximately 4.25 billion years ago, has drawn particular interest among scientists studying its long-term effects on the Moon’s interior and surface.
Significant Findings from Basalt Samples
Researchers from the Institute of Geology and Geophysics (IGG) at the Chinese Academy of Sciences (CAS) have conducted a detailed analysis of the basalt samples returned by the Chang’e-6 lander. Their findings indicate that the massive impact responsible for the basin also caused heating in the Moon’s deep materials, leading to the loss of certain volatile elements. Utilizing high-precision isotope analysis, the team detected subtle variations in isotope ratios, capturing the effects left by the impact event.
Scientists emphasize the importance of understanding how impacts have influenced the Moon’s surface, as they are considered the primary external force in its geological history. In contrast to Earth, where tectonic activity drives geological changes, the Moon’s landscape has been shaped predominantly by impacts. The research team reported that the high-temperature environment generated by the significant impact affected moderately volatile elements such as potassium, zinc, and gallium. These elements are particularly sensitive to volatilization and isotopic fractionation at elevated temperatures, making their isotopic fingerprints valuable for understanding the conditions created by these impacts.
Another intriguing discovery was the contrast between the samples from Chang’e-6 and those collected during the Apollo missions to the near side of the Moon. The basalts retrieved from the far side exhibited a higher concentration of the heavier potassium-41 isotope. To investigate the source of this discrepancy, the research team explored various factors, including cosmic rays, volcanic activity, and impactor deposition. Ultimately, they concluded that an early large-scale impact altered the potassium isotope composition in the deep lunar mantle, resulting in the loss of the lighter potassium-39 isotope and an increase in potassium-41.
Implications for Future Lunar Exploration
These findings contribute to a growing body of evidence that highlights significant differences in the geological evolution of the near and far sides of the Moon over billions of years. The loss of volatile elements, as indicated by the study, may have suppressed volcanic activity on the Moon’s far side, further differentiating it from the near side.
The analysis of Chang’e-6 samples underscores the critical role that Chinese missions and scientists are playing in enhancing our understanding of the Moon’s history and its co-evolution with Earth. As the global interest in lunar exploration intensifies, this research not only informs future missions but also enriches the collective knowledge of our celestial neighbor.
