China’s Chang’e-6 mission, the first sample return mission to the far side of the Moon last year, made a fascinating discovery.
Examining the returned lunar samples, which arrived on Earth in June last year, scientists discovered fragments of carbonaceous chondrite (CI chondrite), which once belonged to a water-bearing meteorite that rarely survives the journey through Earth’s atmosphere, such as Scientific alert reports.
This is the first time we have observed CI chondrites on the Moon, suggesting that volatile-rich asteroids – which are very porous, with hydrated minerals making up up to 20% of their mass – can reach the lunar surface.
Thanks to their porous nature, they can easily break if they hit another object or a planet’s atmosphere. According to a press release from the Chinese Academy of Sciences regarding the discovery, less than one percent of meteorites on Earth are CI chondrites. Even an impact with the Moon could vaporize or melt it, making the latest discovery particularly tantalizing.
“Given the rarity of CI chondrites in the Earth meteorite collection, our integrated methodology for identifying exogenous materials in lunar and potentially other returned samples offers a valuable tool for reassessing the proportions of chondrites in the inner Solar System,” the international team of researchers wrote in a new paper published in the journal. PNAS.
The samples brought back by the Chang’e-6 mission came from inside the South Pole-Aitken basin, where it landed, one of the largest known impact craters in the solar system.
The team used advanced microscopy and spectrometry techniques to identify highly unusual ratios of various isotopes in samples of olivine, a common silicate mineral found in volcanic rocks and meteorites.
These ratios were consistent with a Cl chondrite asteroid that collided with the Moon and cooled after melting into a puddle, effectively preserving it, as Scientific alert explain.
Researchers say the meteorite could have come from the outer solar system, indicating that the material can survive migration to the inner solar system.
The results also suggest that these asteroids are much more common on the Moon than previously estimated, accounting for up to 30% of the samples collected by Chang’e-6.
According to Lin Mang, co-author and researcher at the Guangzhou Institute of Geochemistry, the results could have implications for our understanding of how water reaches the lunar surface and its distribution.
The results support current theories that carbonaceous asteroids seeded Earth by bombarding it with water billions of years ago.
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