DATE2023.07.11 #Press Releases

Deciphering the temporal change of oxygen concentrations and other gaseous species from Ryugu carbonates

Overview of the press release

A research team led by Associate Professor Wataru Fujiya of the Graduate School of Science and Engineering, Ibaraki University, Associate Professor Noriyuki Kawasaki and Professor Hisayoshi Yurimoto of the Faculty of Science, Hokkaido University, Professor Tetsuya Yokoyama of the Department of Earth and Planetary Sciences, School of Science, Tokyo Institute of Technology, and Professor Shogo Tachibana of the Graduate School of Science, the University of Tokyo has analyzed samples returned by the Hayabusa2 spacecraft from asteroid Ryugu. The researchers successfully deciphered the temporal change of oxygen concentrations and gaseous species present on Ryugu.

The team investigated the ratios of carbon and oxygen isotopes in the carbonate minerals (calcite and dolomite) of the Ryugu samples. The results show that the isotope ratios of both carbon and oxygen varied greatly in the calcite sample, but varied little in dolomite. This suggests that calcite formed early in Ryugu’s history, when temperature and oxygen concentrations were increasing and the ratio of gaseous species were in flux, while dolomite formed when the system was in equilibrium, at higher temperatures, and with a relatively high ratio of carbon dioxide among the gases.

Such isotopic compositions of carbonate minerals have not been reported in previous meteorite studies, indicating that the parent bodies of Ryugu and other meteorites are composed of different materials and evolved in unique environments.

The research results were published online in Nature Geoscience on Wednesday, July 10, 2023.

The team compared the carbon and oxygen isotope ratios of the calcite and dolomite in samples taken from Ryugu and Ivuna (meteorite) and found that calcite exhibited greater variability than dolomite. The arrows in the diagram show the changes in isotope ratios following water-rock reactions, temperature increase, and increase in oxygen fugacity.

To read the full press release, please visit the website of Ibaraki University.^{*japanese only}

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