Joint Press Release
Shogo Tachibana (Professor, UTOPS, Department of Earth and Planetary Science, ISAS)

An international joint research group led by Deputy Chief Researcher Toshihiro Yoshimura and Senior Researcher Yoshinori Takano of the Japan Agency for Marine-Earth Science and Technology, Chief Researcher Daisuke Araoka of the National Institute of Advanced Industrial Science and Technology, and Professor Hiroshi Naraoka of the Graduate School of Science, Kyushu University, together with researchers from the University of Tokyo, Horiba Techno Service, Hokkaido University, Tokyo Institute of Technology, and Tokai National University Organization Nagoya University, have conducted an international joint research project on the asteroid Ryugu. Precise chemical analyses of magnesian minerals such as breunnerite and primitive brines in samples from the asteroid Ryugu revealed their composition and content.

Asteroid Ryugu is one of the most primitive bodies that retain the chemical composition of the entire solar system before the birth of the Earth. Although analyses by various research groups have revealed aqueous metamorphism involving minerals, organic matter, and water, the reaction history of the so-called “brine chemical composition and precipitation of ionic components” has remained unknown.

In this study, we isolated and identified small carbonate minerals (breunnerite) from samples from the asteroid Ryugu, extracted the cationic components with solvents, and performed precise chemical composition analysis. As a result, the cation composition of the last water in contact with the minerals in Ryugu was found to be rich in sodium ions (Na⁺). There are several minerals in Ryuguu that are very rich in magnesium, which elucidated the precipitation order of magnesium removal from the water. Sodium ions may have acted as electrolytes that stabilized the surface charges of minerals and organic materials.

This achievement is an important finding that unravels the chemical evolution of the early solar system and provides primary information on primordial brine material and water-mineral interactions on carbonaceous asteroids.

The results were published in the scientific journal Nature Communications on September 5, 2024 (JST).

For more information, please refer to the following

Graduate School of Science web: https://www.s.u-tokyo.ac.jp/en/press/10478/

Publication URL: https://www.nature.com/articles/s41467-024-50814-y