Chang’e-6 Lunar Soil Reveals Changing History of Asteroid Impacts – Chinese Academy of Sciences

The Chinese Academy of Sciences has released findings from the analysis of soil samples collected by the Chang’e-6 mission, revealing a detailed chronological record of asteroid impacts on the lunar far side. The data provides new evidence regarding how the frequency and intensity of these impacts shifted over billions of years, offering insights into the early evolution of the solar system.

The samples were retrieved from the South Pole-Aitken basin, which is one of the largest, deepest, and oldest known impact craters in the solar system. Because the lunar far side lacks the volcanic plains found on the near side, it preserves a more pristine record of the bombardment history that affected both the Moon and the early Earth.

Analyzing the South Pole-Aitken Basin

Researchers utilized the Chang’e-6 samples to examine the composition and age of the lunar crust in a region previously inaccessible to sample-return missions. By dating the minerals within the soil, the Chinese Academy of Sciences identified specific layers that correspond to different eras of asteroid activity.

The analysis indicates that the bombardment of the Moon was not a uniform process. Instead, the data suggests a changing history where the size and frequency of asteroid impacts evolved, helping scientists refine the timeline of the early solar system’s volatile period.

This research specifically addresses the Late Heavy Bombardment theory, which proposes that there was a spike in asteroid impacts between 4.1 and 3.8 billion years ago. The Chang’e-6 samples allow scientists to compare far-side impact data with existing near-side data collected during the Apollo missions.

Technical Significance of Far-Side Sampling

The lunar far side is characterized by a thicker crust and a higher concentration of highlands compared to the near side. This asymmetry has long been a subject of planetary science, as the near side was heavily resurfaced by basaltic lava flows from the Moon’s interior.

By obtaining physical samples from the South Pole-Aitken basin, the mission provides a direct geochemical baseline for the lunar far side. This allows researchers to determine if the differences between the two hemispheres were caused by the distribution of asteroid impacts or by internal thermal processes.

The sample return process involved a complex series of maneuvers, including a landing on the far side, the automated collection of regolith, and a transfer from the lunar surface to an orbiter before returning to Earth on June 25, 2024.

Implications for Solar System Evolution

The findings from the Chinese Academy of Sciences contribute to a broader understanding of the impact flux in the inner solar system. Because the Moon acts as a historical record for the Earth, the impact history revealed in the lunar soil mirrors the events that occurred on Earth during its earliest stages.

The data suggests that the distribution of impacts was not entirely random, pointing toward gravitational influences from the giant planets that may have nudged asteroids toward the inner solar system in waves.

This geological evidence helps researchers constrain the timing of the formation of the Moon’s crust and the period during which the lunar magma ocean solidified.

Future Research Trajectory

The analysis of the Chang’e-6 samples is expected to continue over several years, with international collaborations likely to expand the scope of the research. Scientists intend to use high-precision mass spectrometry and X-ray diffraction to further isolate the chemical signatures of the impactors.

The results from this mission establish a framework for future explorations of the lunar poles, where water ice is believed to exist in permanently shadowed regions. Understanding the impact history of the South Pole-Aitken basin is critical for selecting future landing sites for permanent lunar bases.

By mapping the history of asteroid impacts, the mission provides a blueprint for how planetary scientists can use sample-return data to reconstruct the history of other airless bodies in the solar system, such as Mars or asteroids.