The team from the Institute of Geology at the Chinese Academy of Geological Sciences analyzed fragments of impact-melted material found in the samples using a domestically developed ion probe, explained Long Tao, deputy director of the institution’s Planetary Science Center.

  Long compared the procedure to shooting a basketball into a hoop from a distance of 3,000 meters, given the precision required to direct the beam onto a specific point on the sample.

  The results link the difference between the two lunar sides to the massive impact that created the South Pole-Aitken basin approximately 4.3 billion years ago—considered the largest, deepest, and oldest known impact structure on the Moon.

  The near side features numerous dark zones of volcanic basalt, known as lunar maria (seas), whereas the far side is dominated by bright, elevated terrain and contains far fewer maria.

  Che Xiaochao, an associate researcher at the institute, noted that the massive impact could have displaced materials from the far side, explaining why samples obtained from the South Pole-Aitken basin show a higher proportion of radioactive elements than those originating from the more primitive lunar crust.

  The Chang’e-6 mission returned to Earth in 2024 with 1,935.3 grams of samples collected—for the first time—from the Moon’s far side, specifically the South Pole-Aitken basin.

  Studying these materials allows for a direct comparison of the composition of regions on both sides and provides new data to investigate the origin of the so-called lunar dichotomy, one of the key questions regarding the evolution of Earth’s natural satellite.

jdt/ro/idm