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Carbonate record of temporal change in oxygen fugacity and gaseous species in asteroid Ryugu


The Hayabusa2 spacecraft explored asteroid Ryugu and brought its surface materials to Earth. Ryugu samples resemble Ivuna-type (CI) chondrites—the most chemically primitive meteorites—and contain secondary phyllosilicates and carbonates, which are indicative of aqueous alteration. Understanding the conditions (such as temperature, redox state and fluid composition) during aqueous alteration is crucial to elucidating how Ryugu evolved to its present state, but little is known about the temporal changes in these conditions. Here we show that calcium carbonate (calcite) grains in Ryugu and Ivuna samples have variable 18O/16O and 13C/12C ratios that are, respectively, 24–46‰ and 65–108‰ greater than terrestrial standard values, whereas those of calcium–magnesium carbonate (dolomite) grains are much more homogeneous, ranging within 31–36‰ for oxygen and 67–75‰ for carbon. We infer that the calcite precipitated first over a wide range of temperatures and oxygen partial pressures, and that the proportion of gaseous CO2/CO/CH4 molecules changed temporally. By contrast, the dolomite formed later in a more oxygen-rich and thus CO2-dominated environment when the system was approaching equilibrium. The characteristic isotopic compositions of secondary carbonates in Ryugu and Ivuna are not observed for other hydrous meteorites, suggesting a unique evolutionary pathway for their parent asteroid(s).

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Fig. 1: Calcite grains in the Ryugu C0002 sample.
Fig. 2: Oxygen isotope compositions of the calcite and dolomite in Ryugu and Ivuna samples.
Fig. 3: Comparison between C and O isotope compositions of the calcite and dolomite in Ryugu and Ivuna samples.

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Data availability

All data generated or analysed during this study are included in this published article (and its supplementary information files) and are available via Zenodo ( As the initial analysis of Ryugu samples collected by the Hayabusa2 spacecraft, the specimens analysed in this study were allocated to us by JAXA. The Ivuna specimen used in this study was kindly proved by the Natural History Museum, UK.


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We thank D. Rogers, M. Spicuzza and J. Valley for the preparation of carbonate standard materials for SIMS measurements and A. Tsuchiyama for discussion. Hayabusa2 was developed and built under the leadership of Japan Aerospace Exploration Agency (JAXA), with contributions from the German Aerospace Center (DLR) and the Centre National d’Études Spatiales (CNES), and in collaboration with NASA, and other universities, institutes and companies in Japan. The curation system was developed by JAXA in collaboration with companies in Japan. This research was supported in part by the JSPS KAKENHI grant numbers 19H00725 (W.F.), 20K20934 (W.F. and T.N.) and 22K18722 (N.K.).

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Authors and Affiliations



W.F., N.K., K.N., N.S. and H. Yurimoto designed this study and T. Nakamura, H.N., T. Noguchi, R.O., K.S., H. Yabuta, M.A., A.M., A. Nakato, M.N., T.O., T. Yada, K. Yogata, S.N., T.S., S. Tanaka, F.T., Y. Tsuda, S. Watanabe, M.Y. and S. Tachibana supported them. W.F., N.K., K.N., N.S. and H. Yurimoto analysed the samples, and N.T.K. and K.K. assisted the analysis. W.F., N.K., K.N. and H. Yurimoto were involved in data reduction. C.M.O’D.A., Y. Abe, J.A., S.A., Y. Amelin, K.B., M.B., A.B., R.W.C., M.C., B.-G.C., N.D., A.M.D., T.D.R., R.F., I.G., M.K.H., Y.H., H. Hidaka., H. Homma, P.H., G.R.H., K.I., T.I., T.R.I., A.I., S.I., T.K., S.K., A.N.K., M.-C.L., Y.M., K.D.M., M.M., K.M., F.M., I.N., A. Nguyen, L.N., M.O., A.P., C.P., L.P., L.Q., S.S.R., M.S., L.T., H.T., K.T., Y. Terada, T.U., S. Wada, M.W., R.J.W., K. Yamashita, Q.-Z.Y., T. Yokoyama, S.Y., E.D.Y., H. Yui and A.-C.Z. contributed to data interpretation. W.F. wrote the paper with support and approval of all co-authors.

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Correspondence to Wataru Fujiya.

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Nature Geoscience thanks John Eiler, Michael Zolensky and Christopher Herd for their contribution to the peer review of this work. Primary Handling Editors: Stefan Lachowycz and Alison Hunt, in collaboration with the Nature Geoscience team.

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Extended data

Extended Data Fig. 1 Compositional variation of Ryugu and Ivuna carbonates.

(a) Ternary diagram of dolomite and calcite in Ryugu and Ivuna samples (see also Supplementary Table 1). (b-d) Backscattered electron image: BEI (b), Mn Kα1 X-ray map (c), Fe Kα1 X-ray map (d) of a dolomite grain in the Ryugu C0002 sample.

Extended Data Fig. 2 Comparison between C and O isotope compositions of carbonates in Ryugu, CI, and CM chondrites.

CM chondrite data are taken from Telus et al. (ref. 38). The δ13C values of CM calcite are variable like Ryugu/CI calcite, but the highest reported value in CM calcite is lower than that of Ryugu/CI calcite. The δ13C and δ18O values of CM dolomite are also variable, whereas those of Ryugu/CI dolomite are more homogeneous. Data generated during this study are presented as mean values ± 2σ errors which are either external reproducibility (2 SD, N = 6–20 depending on the measurement sessions) of standard measurements or internal precision (2SE) of the data within single measurements, whichever is larger.

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Fujiya, W., Kawasaki, N., Nagashima, K. et al. Carbonate record of temporal change in oxygen fugacity and gaseous species in asteroid Ryugu. Nat. Geosci. 16, 675–682 (2023).

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