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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All data generated or analysed during this study are included in this published article (and its supplementary information files) and are available via Zenodo (https://doi.org/10.5281/zenodo.7957625). 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.
Tachibana, S. et al. Hayabusa2: scientific importance of samples returned from C-type near-Earth asteroid (162173) 1999 JU3. Geochem. J. 48, 571–587 (2014).
Tachibana, S. et al. Pebbles and sand on asteroid (162173) Ryugu: in situ observation and particles returned to Earth. Science 375, 1011–1016 (2022).
Binzel, R. P., Harris, A. W., Bus, S. J. & Burbine, T. H. Spectral properties of near-Earth objects: Palomar and IRTF results for 48 objects including spacecraft targets (9969) Braille and (10302) 1989 ML. Icarus 151, 139–149 (2001).
Campins, H. et al. Spitzer observations of spacecraft target 162173 (1999 JU3). Astron. Astrophys. 503, L17–L20 (2009).
Watanabe, S. et al. Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu—a spinning top-shaped rubble pile. Science 364, 268–272 (2019).
Sugita, S. et al. The geomorphology, color, and thermal properties of Ryugu: implications for parent-body processes. Science 364, eaaw0422 (2019).
Kitazato, K. et al. The surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy. Science 364, 272–275 (2019).
Yokoyama, T. et al. Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites. Science 379, eabn7850 (2023).
Nakamura, T. et al. Formation and evolution of carbonaceous asteroid Ryugu: direct evidence from returned samples. Science 379, eabn8671 (2023).
Nakamura, E. et al. On the origin and evolution of the asteroid Ryugu: a comprehensive geochemical perspective. Proc. Jpn Acad. Ser. B 98, 227–282 (2022).
Hopp, T. et al. Ryugu’s nucleosynthetic heritage from the outskirts of the Solar System. Sci. Adv. 8, eadd8141 (2022).
Paquet, M. et al. Contribution of Ryugu-like material to Earth’s volatile inventory by Cu and Zn isotopic analysis. Nat. Astron. 7, 182–189 (2023).
Moynier, F. et al. The Solar System calcium isotopic composition inferred from Ryugu samples. Geochem. Persp. Lett. 24, 1–6 (2022).
Johnson, C. A. & Prinz, M. Carbonate compositions in CM and CI chondrites, and implications for aqueous alteration. Geochim. Cosmochim. Acta 57, 2843–2852 (1993).
Riciputi, L. R., McSween, H. Y. Jr., Johnson, C. A. & Prinz, M. Minor and trace element concentrations in carbonates of carbonaceous chondrites, and implications for the compositions of coexisting fluids. Geochim. Cosmochim. Acta 58, 1343–1351 (1994).
Guo, W. & Eiler, J. M. Temperatures of aqueous alteration and evidence for methane generation on the parent bodies of the CM chondrites. Geochim. Cosmochim. Acta 71, 5565–5575 (2007).
Verdier-Paoletti, M. J. et al. Oxygen isotope constraints on the alteration temperatures of CM chondrites. Earth Planet. Sci. Lett. 458, 273–281 (2017).
Alexander, C. M. O. ’D., Bowden, R., Fogel, M. L. & Howard, K. T. Carbonate abundances and isotopic compositions in chondrites. Meteorit. Planet. Sci. 50, 810–833 (2015).
Fujiya, W. et al. Migration of D-type asteroids from the outer Solar System inferred from carbonate in meteorites. Nat. Astron. 3, 910–915 (2019).
McCain, K. A. et al. Early fluid activity on Ryugu inferred by isotopic analyses of carbonates and magnetite. Nat. Astron. 7, 309–317 (2023).
Chacko, T., Cole, D. R. & Horita, J. in Stable Isotope Geochemistry (eds Valley, J. W. and Cole, D. R.) 1–81 (Mineralogical Society of America, 2001).
Zolensky, M. E., Bourcier, W. L. & Gooding, J. L. Aqueous alteration on the hydrous asteroids: results of EQ3/6 computer simulations. Icarus 78, 411–425 (1989).
Zheng, Y.-F. On the theoretical calculations of oxygen isotope fractionation factors for carbonate–water systems. Geochem. J. 45, 341–354 (2011).
Clayton, R. N. & Mayeda, T. K. The oxygen isotope record in Murchison and other carbonaceous chondrites. Earth Planet. Sci. Lett. 67, 151–161 (1984).
Marrocchi, Y., Bekaert, D. V. & Piani, L. Origin and abundance of water in carbonaceous asteroids. Earth Planet. Sci. Lett. 482, 23–32 (2018).
Sakamoto, N. et al. Remnants of the early Solar System water enriched in heavy oxygen isotopes. Science 317, 231–233 (2007).
Vacher, L. G., Marrocchi, Y., Verdier-Paoletti, M. J., Villeneuve, J. & Gounelle, M. Inward radial mixing of interstellar water ices in the solar protoplanetary disk. Astrophys. J. Lett. 827, L1 (2016).
Kawasaki, N. et al. Oxygen isotopes of anhydrous primary minerals show kinship between steroid Ryugu and comet 81P/Wild2. Sci. Adv. 8, eade2067 (2022).
Wilson, L., Keil, K., Browning, L. B., Krot, A. N. & Bourcier, W. Early aqueous alteration, explosive disruption, and reprocessing of asteroids. Meteorit. Planet. Sci. 34, 541–557 (1999).
Beck, P. et al. The redox state of iron in the matrix of CI, CM and metamorphosed CM chondrites by XANES spectroscopy. Geochim. Cosmochim. Acta 99, 305–316 (2012).
Barnaby, R. J. & Rimstidt, J. D. Redox conditions of calcite cementation interpreted from Mn and Fe contents of authigenic calcites. Geol. Soc. Am. Bull. 101, 795–804 (1989).
Fujiya, W., Aoki, Y., Ushikubo, T., Hashizume, K. & Yamaguchi, A. Carbon isotopic evolution of aqueous fluids in CM chondrites: clues from in-situ isotope analyses within calcite grains in Yamato-791198. Geochim. Cosmochim. Acta 274, 246–260 (2020).
Mumma, M. J. & Charnley, S. B. The chemical composition of comets—emerging taxonomies and natal heritage. Annu. Rev. Astron. Astrophys. 49, 471–524 (2011).
Ootsubo, T. et al. AKARI near-infrared spectroscopic survey for CO2 in 18 comets. Astrophys. J. 752, 15 (2012).
Richet, P., Bottinga, Y. & Javoy, M. A review of hydrogen, carbon, nitrogen, and chlorine stable isotope fractionation among gaseous molecules. Annu. Rev. Earth Planet. Sci. 5, 65–110 (1977).
Fujiya, W., Sugiura, N., Sano, Y. & Hiyagon, H. Mn–Cr ages of dolomites in CI chondrites and the Tagish Lake ungrouped carbonaceous chondrite. Earth Planet. Sci. Lett. 362, 130–142 (2013).
Thiagarajan, N. et al. Isotopic evidence for quasi-equilibrium chemistry in thermally mature natural gases. Proc. Natl Acad. Sci. USA 117, 3989–3995 (2017).
Telus, M., Alexander, C. M. O. ’D., Hauri, E. H. & Wang, J. Calcite and dolomite formation in the CM parent body: insight from in situ C and O isotope analyses. Geochim. Cosmochim. Acta 260, 275–291 (2019).
Vacher, L. G., Marrocchi, Y., Villeneuve, J., Verdier-Paoletti, M. J. & Gounelle, M. Petrographic and C & O isotopic characteristics of the earliest stages of aqueous alteration of CM chondrites. Geochim. Cosmochim. Acta 213, 271–290 (2017).
Sheppard, S. M. F. & Schwarcz, H. P. Fractionation of carbon and oxygen isotopes and magnesium between coexisting metamorphic calcite and dolomite. Contrib. Mineral. Petrol. 26, 161–198 (1970).
Romanek, C. S., Grossman, E. L. & Morse, J. W. Carbon isotopic fractionation in synthetic aragonite and calcite: effects of temperature and precipitation rate. Geochim. Cosmochim. Acta 56, 419–430 (1992).
Aponte, J. C., McLain, H. L., Dworkin, J. P. & Elsila, J. E. Aliphatic amines in Antarctic CR2, CM2, and CM1/2 carbonaceous chondrites. Geochim. Cosmochim. Acta 189, 296–311 (2016).
Hässig, M. et al. Isotopic composition of CO2 in the coma of 67P/Churyumov-Gerasimenko measured with ROSINA/DFMS. Astron. Astrophys. 605, A50 (2017).
Yurimoto, H. & Kuramoto, K. Molecular cloud origin for the oxygen isotope heterogeneity in the Solar System. Science 305, 1763–1766 (2004).
Lyons, J. R. & Young, E. D. CO self-shielding as the origin of oxygen isotope anomalies in the early solar nebula. Nature 435, 317–320 (2005).
Lyons, J. R., Gharib-Nezhad, E. & Ayres, T. R. A light carbon isotope composition for the Sun. Nat. Commun. 9, 908 (2018).
Visser, R., van Dishoeck, E. F. & Black, J. H. The photodissociation and chemistry of CO isotopologues: applications to interstellar clouds and circumstellar disks. Astron. Astrophys. 503, 323–353 (2009).
Woods, P. M. & Willacy, K. Carbon isotope fractionation in protoplanetary disks. Astrophys. J. 693, 1360–1378 (2009).
Kozdon, R., Ushikubo, T., Kita, N. T., Spicuzza, M. & Valley, J. W. Intratest oxygen isotope variability in the planktonic foraminifer N. pachyderma: real vs. apparent vital effects by ion microprobe. Chem. Geol. 258, 327–337 (2009).
Śliwiński, M. G. et al. Secondary ion mass spectrometry bias on isotope ratios in dolomite–ankerite, part I: δ18O matrix effects. Geostand. Geoanal. Res. 40, 157–172 (2015).
Śliwiński, M. G. et al. Secondary ion mass spectrometry bias on isotope ratios in dolomite-ankerite, part II: δ13C matrix effects. Geostand. Geoanal. Res. 40, 173–184 (2015).
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.).
The authors declare no competing interests.
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(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). https://doi.org/10.1038/s41561-023-01226-y