DATE2026.09.17 #Press Releases

"Invisible Matter" Found in Ryugu and Carbonaceous Meteorites

Disclaimer: machine translated by DeepL which may contain errors.

Records from the Early Solar System Provide Clues to Solving a Mystery

Abstract

The asteroid Ryugu and certain carbonaceous meteorites are believed to be remnants of celestial bodies formed in the very early Solar System and are known as “primitive” materials that well preserve the elemental composition present at the time of the Solar System’s formation.However, after their formation, these rocks reacted strongly with water, causing many of the original minerals to transform into different minerals (hydrometamorphism).When rocks react with water, elements may dissolve into the water or migrate, potentially altering the original elemental composition. This seemingly contradictory characteristic —that “despite reacting strongly with water, they retain the elemental composition of the early solar system” —is one of the long-standing mysteries in astrochemistry.

Led by Reon Okumura, a master’s student in the Graduate School of Natural Science and Technology at Kanazawa University; Professor Keisuke Fukushi of the Japan Sea Environmental Research Center; and Professor Yoshio Takahashi of the Graduate School of Science at The University of Tokyo, a joint research group comprising Kanazawa University,The University of Tokyo, the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Hiroshima University, the Japan Synchrotron Radiation Research Institute (JASRI·NanoTerasu), the High Energy Accelerator Research Organization (KEK), and Tokyo University of Science has discovered a substance in extraterrestrial samples that provides a clue to solving this long-standing mystery.

Using powerful X-rays from a large synchrotron radiation facility, the research group conducted detailed analyses and revealed that components similar to low-crystalline magnesium silicate hydrate (M-S-H) —which had not been fully recognized until now—are widely present in Ryugu and carbonaceous meteorites.M-S-H is a substance that can contain magnesium and silicon in various proportions. Generally, different compositions of a substance correspond to different aqueous environments in which it can exist.However, when our research group investigated the solubility of M-S-H in water using laboratory experiments and existing data, we found that even M-S-H with different compositions can exist under similar aqueous conditions.These results support the possibility that, even when rock compositions vary from place to place, reactions with water proceeded without significantly losing those differences. This property of M-S-H provides a strong clue for explaining the seemingly contradictory characteristic of being “strongly altered yet primitive.”

The findings of this study were published on September 7, 2026, in the British scientific journal *Communications Earth & Environment*.

A model based on the conventional mineralogical interpretation of Ryugu and carbonaceous meteorites that have undergone strong alteration by water, combined with the spectroscopic and physicochemical results obtained in this study. 🄫Fukushi., K. et al., Kanazawa University (2026)

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