Overlooked material in Ryugu and meteorites may explain how water spared ancient chemistry

A research team led by Kanazawa University and The University of Tokyo used powerful X-rays at the large-scale synchrotron facilities KEK-PF and SPring-8 to examine asteroid Ryugu and carbonaceous meteorites. They identified a previously overlooked material resembling poorly crystalline magnesium silicate hydrate (M-S-H), which may explain how water reacted with these materials without altering their original chemical composition. The material can accommodate a wide range of magnesium-to-silicon ratios, suggesting it may have formed under similar aqueous conditions. This flexibility could have allowed water to interact with the minerals without erasing their original chemical differences. The findings suggest that different alteration minerals could form while preserving preexisting compositional differences. M-S-H may provide an important clue to understanding how these materials could be extensively altered yet remain chemically primitive.

The study published in Communications Earth & Environment, led by Reon Okumura et al., found that M-S-H is widespread in Ryugu and carbonaceous meteorites. This material is distinct from serpentine and saponite, which are typically associated with aqueous alteration. The researchers used synchrotron-based soft X-ray absorption spectroscopy to detect M-S-H. The results suggest that M-S-H could have formed from precursor materials before transforming into the more crystalline minerals. This finding challenges previous interpretations of aqueous alteration in primitive carbonaceous meteorites.

The study highlights the importance of examining the composition of altered materials to understand how water could have affected them without destroying their original chemical structure. The discovery of M-S-H may provide a key insight into the mechanisms of water-rock interactions in the early solar system. The research underscores the value of advanced analytical techniques in uncovering the complex processes that shaped extraterrestrial materials.

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