Where does the water on the moon come from? Can the matter from the outer solar system travel billions of miles to reach us? The lunar soil of Chang'e-6 provides key clues for solving these puzzles. Chinese researchers have discovered rare meteorite impact remnants in lunar soil samples from the Chang'e-6 mission, which not only confirms that asteroid fragments can travel long distances from the outer solar system to the inner solar system, but also provides new clues to explain the source of water on the moon. The relevant research results were published on the 21st in the Proceedings of the National Academy of Sciences in the United States. Meteorites are known as the 'messengers of the solar system', carrying the secrets of planetary birth and evolution. But the Earth has a thick atmosphere, and when meteorites fall, they are like passing through an incinerator, mostly burned or worn down; Due to frequent crustal movements, the traces left by meteorites are also difficult to preserve. This makes a precious meteorite rich in water and organic matter, the CI type carbonaceous chondrite, extremely rare on Earth. On the contrary, the moon has no atmosphere or geological activity, just like a perfect "natural archive" that can clearly preserve the traces of meteorite impacts over billions of years. In this study, a team led by Academician Xu Yigang and researcher Lin Mang of the Chinese Academy of Sciences Guangzhou Institute of Geochemistry conducted a systematic analysis on the lunar soil samples of Chang'e 6, and successfully identified the impact debris of CI type carbonaceous chondrite. "Our research found that these fragments were the products of melting and rapid cooling of the parent body of this type of meteorite after it hit the moon surface. At the same time, we also established a new method to effectively identify meteorite materials in extraterrestrial samples." said Wang Jintuan, co first author of the paper and associate researcher of the Guangzhou Institute of Geochemistry of the Chinese Academy of Sciences. It is worth noting that the parent asteroids of CI type meteorites are mainly distributed in the outer solar system and are usually rich in volatile components such as water and organic matter. Statistical analysis shows that the proportion of such meteorites on the lunar surface is much higher than on Earth, indicating that the contribution of carbonaceous meteorites to the Earth Moon system in the past may have been severely underestimated. Xu Yigang stated that this discovery not only confirms that materials from the outer solar system can migrate inward, refreshing previous understanding of the mechanisms of material movement in the solar system, but also provides new directions for future research on the distribution and evolution of lunar water resources. Researchers suggest that the specific features of water detected in lunar samples previously may have originated from the impact of such meteorites. (New Society)