China’s lunar exploration continues to yield remarkable discoveries. The Chang’e-6 mission has returned with an unexpected find: microscopic dust containing fragments of a rare type of meteorite known as CI chondrite, or Ivuna-type carbonaceous chondrite. This marks the first confirmed detection of this fragile material on the Moon, challenging previous assumptions about the survival of such meteorites in lunar conditions.
The research team, led by geochemists Jintuan Wang and Zhiming Chen from the Chinese Academy of Sciences, analyzed over 5,000 fragments collected from the Moon’s far side. They focused on the Apollo Basin, a crater within the expansive South Pole-Aitken Basin, which is one of the largest impact craters in the Solar System. This site was selected for its potential to yield ancient impact debris.
Significance of CI Chondrites
CI chondrites are known for being highly volatile and water-rich, with up to 20 percent of their mass composed of hydrated minerals. These meteorites are soft and porous, making them less likely to survive atmospheric entry on Earth, with less than one percent of meteorites found being classified as CI chondrites. The Moon’s lack of atmosphere presents its own challenges; however, the high-impact velocities at which objects collide with the lunar surface typically lead to vaporization or ejection back into space.
The researchers concentrated on olivine, a mineral commonly found in both volcanic rocks and meteorites. Through meticulous preparation, they isolated several olivine-bearing fragments, which were then subjected to advanced analytical techniques, including scanning electron microscopy and secondary ion mass spectrometry. Ultimately, they identified seven clasts with chemical signatures consistent with those found in CI chondrites.
Implications for Lunar Science
The findings revealed that these olivine clasts exhibited porphyritic structures, indicating they formed from impact melts that cooled quickly. Notably, the chemical and isotopic analyses showed that the iron-to-manganese ratios, along with other elemental compositions, did not align with either lunar or terrestrial origins. Instead, they matched the expected values for CI chondrites, suggesting that these meteorites impacted the Moon, melted, and retained their unique chemical signatures over billions of years.
This discovery provides the first direct evidence that CI chondrites contributed to the lunar surface early in the Solar System’s history. It also suggests that the Moon may be more conducive to the preservation of such fragile materials than Earth. The researchers propose that CI chondrites could represent as much as 30 percent of the Moon’s meteorite collection.
Past studies have speculated about the role of CI chondrites in delivering water and volatiles to early Earth and the Moon. The tiny grains of dust from the Moon’s far side strengthen this hypothesis, opening avenues for further exploration.
The research findings have been published in the Proceedings of the National Academy of Sciences. As future lunar missions continue to gather samples, scientists hope to expand their understanding of the role these meteorites played in shaping the early Solar System and potentially influencing the development of life on Earth.
The implications of this research are profound, providing valuable insights into the composition of celestial bodies and the history of our planetary system.
