New analysis of lunar samples returned by China’s mission is reshaping our understanding of the Moon’s history, revealing evidence of a colossal impact that profoundly altered its interior. The samples, collected from the far side of the Moon’s South Pole-Aitken (SPA) Basin, exhibit unusual chemical signatures suggesting a far more dramatic reshaping of the lunar mantle than previously thought.
The findings, published by researchers at the Chinese Academy of Sciences’ Institute of Geology and Geophysics (IGGCAS), center around the isotopic composition of potassium found within the lunar basalt. The potassium in the Chang’e-6 samples is “heavier” – meaning it has a different isotopic makeup – than that found in samples brought back by the Apollo missions or in lunar meteorites. This difference isn’t random; it points to a significant loss of volatile elements during a massive impact event.
Potassium is considered a moderately volatile element, meaning it can vaporize under extreme heat. During a giant impact, the temperatures generated are sufficient to allow potassium to evaporate, and its isotopes to separate. The heavier isotopic signature observed in the Chang’e-6 samples suggests that a substantial amount of the lighter potassium isotopes were lost during the formation of the SPA Basin, the largest and oldest known impact basin on the Moon.
“The key turned out to be potassium,” explains analysis from Universe Magazine. “Fragments of basalt from Chang’e-6 were found to have a heavier isotopic composition of potassium than samples from Apollo and lunar meteorites.” Researchers meticulously ruled out other potential explanations for this isotopic anomaly, including the influence of cosmic rays, magma evolution processes, and contamination from meteorites. The evidence consistently pointed to the SPA impact as the primary cause.
The SPA Basin, a vast depression spanning approximately ’s Science Daily report doesn’t specify the exact dimensions, but it is described as the largest known impact basin on the Moon, is believed to have formed early in the Moon’s history. The new data suggests this impact wasn’t just a surface event; it penetrated deep into the lunar mantle, causing widespread melting and the loss of volatile elements like potassium. This process likely had cascading effects on the Moon’s subsequent volcanic activity and overall chemical composition.
Interestingly, the impact may also explain a long-standing asymmetry observed between the near and far sides of the Moon. The near side, which faces Earth, is characterized by a greater concentration of volcanic features – known as maria – compared to the far side. The researchers propose that the SPA impact could have generated enough heat to trigger convection within the lunar interior, leading to increased volcanism on the near side. The impact’s energy distribution would have favored the side opposite the impact site, explaining the observed difference in volcanic activity.
Beyond the implications for understanding the Moon’s internal structure and volcanic history, the Chang’e-6 samples are also providing a refined chronology of lunar impacts. According to Phys.org, the revised cratering chronology based on the new data provides an improved framework for dating unsampled regions of the Moon. This is crucial for understanding the broader history of the inner solar system and the frequency of impacts that have shaped planetary surfaces.
The success of the Chang’e-6 mission, which achieved the first-ever sample return from the far side of the Moon in , has opened up new avenues for lunar exploration. The 1,935.3 grams of lunar material brought back by the mission are providing scientists with unprecedented insights into the Moon’s ancient past. The analysis of these samples is ongoing, and further discoveries are expected in the coming months and years.
The findings underscore the importance of sample return missions for advancing our understanding of planetary science. While remote sensing and orbital observations provide valuable data, the ability to analyze actual rock samples in terrestrial laboratories offers a level of detail and precision that is simply not possible otherwise. The Chang’e-6 mission, and the insights gleaned from its samples, represent a significant step forward in our quest to unravel the mysteries of the Moon and its place in the solar system.
The research also highlights the growing capabilities of China’s space program and its commitment to lunar exploration. The Chang’e program has consistently pushed the boundaries of lunar science and technology, and the success of Chang’e-6 demonstrates China’s ability to conduct complex and ambitious space missions. This success is likely to spur further investment in lunar exploration and inspire new collaborations between nations.
