A research team from the Chinese Academy of Sciences (CAS) has analyzed samples collected by the Chang”e-6 mission from the Moon”s far side. The study revealed minerals believed to originate from carbonaceous chondrite meteorites, which are known for containing water and organic compounds. This discovery lends credence to the hypothesis that asteroids and comets delivered water and essential components for life to Earth billions of years ago.
Meteorites serve as both messengers and time capsules within our Solar System. They are fragments from larger asteroids or debris ejected by impacts on other celestial bodies. These “space rocks” preserve the original composition of their source, allowing scientists to analyze the chemical makeup of various planetary bodies by studying meteorites. However, weathering, atmospheric processes, and geological activities on Earth complicate such analyses. In contrast, the Moon”s environment is largely unaltered due to its lack of atmosphere, wind, or water erosion, making it an ideal location for preserving meteorite impacts.
The CAS team identified seven olivine-bearing minerals within the lunar regolith that they attributed to Carbonaceous Ivuna-type (CI) chondrites. These fragile meteorites seldom survive their journey through Earth”s atmosphere. The research, led by Professors Xu Yigang and Lin Mang, included experts from various institutions, including the CAS”s Guangzhou Institute of Geochemistry and Brown University. Their findings were published in the Proceedings of the National Academy of Sciences on October 20.
CI chondrites are distinguished by their high carbon content, which can reach up to 3% in forms such as graphite and organic molecules like amino acids. These meteorites originated in the outer Solar System and many migrated inward as the planets were forming. Due to their delicate nature, CI chondrites represent less than 1% of all meteorite samples studied by scientists. However, their preservation on the Moon allows for valuable insights into the conditions prevailing in the early Solar System.
The researchers noted, “Systematic identification and classification of meteorites on the airless Moon thus provide additional critical constraints for reconstructing the primordial accretion history and impactor population of the inner Solar System.” The study faced challenges, as meteors vaporize upon high-velocity impacts with the lunar surface. The team confirmed that the samples formed from molten droplets created during impacts, which rapidly cooled and crystallized in the extreme conditions of space.
Through detailed textural analysis and in-situ triple oxygen isotope assessment, the researchers established that the samples were remnants of CI-like chondrites that struck the Moon prior to the Nectarian Period, approximately 3.92 billion years ago. This timeframe aligns with the Late Heavy Bombardment, a period marked by a significant increase in asteroids and comets impacting the Earth-Moon system and other inner Solar System bodies.
These impacts are believed to have facilitated the introduction of water and organic materials to the inner Solar System. Given that CI chondrites are recognized for their richness in water and organic substances, as evidenced by samples from asteroid Bennu containing amino acids, these results bolster the theory that asteroids were instrumental in delivering vital resources to Earth and its lunar companion. Additionally, the research team posits that previously identified deposits of water ice on the Moon, which displayed specific oxygen isotopes, may have been contributed by CI chondrites in earlier epochs.
Based on their investigation, the researchers conducted a preliminary statistical analysis of meteoritic materials, indicating that CI chondrites likely played a more significant role in shaping the Earth-Moon system than previously understood. Their study provides new insights into the evolutionary history of our Solar System and the events that may have contributed to the emergence of life. Moreover, the methodologies developed during this research could serve as essential tools for analyzing future samples of extraterrestrial materials, paving the way for further scientific exploration.
