Chinese scientists studying a 2-gram lunar soil sample from the Chang'e 6 mission have identified rare CI chondrite impact residues, providing new insights into mass transfer in the inner solar system and offering new perspectives on lunar water distribution and evolution.

The study, led by academician Xu Yigang and researcher Lin Mang from the Guangzhou Institute of Geochemistry of the Chinese Academy of Sciences, was published in the journal Proceedings of the National Academy of Sciences on Tuesday.

CI chondrites, or Ivuna-type carbonaceous chondrites, are a super rare type of meteorite characterized by their primitive chemical composition, which is similar to the sun's nonvolatile elements. Rich in water and volatiles, these meteorites mainly formed in the outer solar system and some of them migrated into the asteroid belt in the inner solar system during the early formation of planets. The CI chondrites are so rare on Earth that they account for less than 1 percent of all collected meteorites.

The identification of CI chondrite impact residues indicates that this material can migrate to the Earthmoon system.

In addition, the research team suggests that the water with positive oxygen isotope characteristics previously detected in lunar samples is likely contributed by impacts from this type of meteorite. This finding provides a new direction for future studies on the contributions of water to the surface of the moon.

In 2024, Chang'e 6 made history by bringing 1,935.3 grams of lunar far-side samples back to Earth. These samples were collected from the South Pole-Aitken Basin, the largest, deepest, and oldest basin on the moon.