China's Chang'e-6 Mission Delivers Lunar Far Side Secrets, Challenging Major Theory of Solar System History

Global - Ekhbary News Agency

China's Chang'e-6 Mission Delivers Lunar Far Side Secrets, Challenging Major Theory of Solar System History

The scientific community is abuzz with the preliminary findings emerging from the lunar samples collected by China’s Chang’e-6 mission. This monumental endeavor successfully retrieved material from the enigmatic far side of the Moon, a region previously untouched by direct human or robotic sample collection. The initial analysis, detailed in a recent paper published in Science Advances by researchers from the Chinese Academy of Sciences, is not merely providing a close-up view of the far side's geology and history; it is actively reshaping our understanding of the Moon's ancient past and, by extension, the early dynamics of the entire solar system.

For decades, our direct knowledge of lunar geology has been overwhelmingly biased towards the "near" side, the face that perpetually points towards Earth. Missions like Apollo and Luna have provided abundant samples, leading to a relatively robust understanding of its formation and impact history. However, the far side has remained largely a mystery, its topography and geological composition inferred mostly through remote sensing. This disparity is primarily due to the inherent challenges of communication: the Moon itself blocks direct radio signals to Earth, necessitating complex relay satellite systems for any mission operating there. China’s space agency pioneered this feat with the Chang’e-4 lander in 2019, marking the first-ever soft landing on the lunar far side. The Chang’e-6 mission, launched in 2024, built upon this success, becoming the first to return samples from this unique lunar frontier.

Scientists have been working diligently on these invaluable samples, and the February paper highlights three particularly compelling insights. Firstly, the study confirms a long-held hypothesis: the impact rates on both the near and far sides of the Moon appear to be remarkably similar. This logical deduction, based on the Moon's exposure to the same celestial environment, had lacked direct evidence until now, making the Chang’e-6 samples crucial for its validation.

Secondly, the research suggests a significant recalibration for the lunar chronology function, a mathematical tool used to estimate the age of lunar surfaces by counting craters. Previously, this function was entirely calibrated using data from near-side samples. The integration of far-side data indicates a potential shift of approximately 340 million years for some dates attributed to specific lunar regions. While substantial in absolute terms, this adjustment represents less than a 10% variation within the Moon's more than 4-billion-year history, underscoring the overall robustness of prior dating methods while refining them with new empirical evidence.

However, the third finding is arguably the most revolutionary: the new data strongly challenges the existence of the "Late Heavy Bombardment" (LHB). This long-standing theory posits that around 3.9 billion years ago, the inner solar system, including Earth and the Moon, experienced an intense period of asteroid impacts. This cataclysmic event was thought to be triggered by gravitational shifts among the outer planets, sending a torrent of debris inwards. Much of the evidence for the LHB came from dating near-side lunar craters, many of which clustered around the 3.9-billion-year mark.

The Chang’e-6 mission’s landing site within the Apollo Basin is itself part of the much larger South-Pole Aitken (SPA) Basin, one of the Moon’s oldest and most prominent features. Samples from this region included the mineral norite, distinct from the more common basalt, and believed to be a direct relic of the massive impact that formed the SPA Basin. Using advanced lead-lead dating techniques, which measure the decay of uranium isotopes into lead isotopes (similar to carbon dating but for much older timescales), researchers determined the age of the SPA Basin to be approximately 4.25 billion years old. This date is significantly older than the theorized start of the LHB.

This discrepancy is profound. If the SPA Basin, arguably the Moon's oldest major structure, formed well before the LHB, it implies that the supposed global bombardment event might not have occurred as universally or intensely as previously believed. The paper suggests that the cluster of 3.9-billion-year-old craters on the near side might instead be attributed to a particularly violent, localized event, such as the Imbrium impact, which could have scattered massive amounts of ejecta across that hemisphere, creating numerous secondary craters of similar age.

Furthermore, by analyzing the distribution of other crater ages, the researchers observed a more gradual, steady decline in impact frequency throughout lunar history. This pattern aligns more closely with a scenario where the early solar system gradually cleared out its debris, rather than experiencing a sudden, chaotic spike in impacts at a specific epoch. Such a revised understanding of lunar impact history has far-reaching implications, potentially altering our fundamental models for the evolution of the entire solar system, including the timing and mechanisms of planetary migration and the delivery of volatile materials to Earth.

The Chang’e-6 mission has thus provided not just rocks, but a new lens through which to view the very foundations of our cosmic neighborhood. As more papers and analyses emerge from these unprecedented samples, the scientific community anticipates further revisions to our understanding of planetary formation and the tumultuous early history of the Moon and its celestial companions.

Ekhbary News Agency