Abstract
Carbonaceous asteroids are the source of the most primitive meteorites1 and represent leftover planetesimals that formed from ice and dust in the outer Solar System and may have delivered volatiles to the terrestrial planets2,3,4,5. Understanding the aqueous activity of asteroids is key to deciphering their thermal, chemical and orbital evolution, with implications for the origin of water on the terrestrial planets. Analyses of the objects, in particular pristine samples returned from asteroid Ryugu, have provided detailed information on fluid–rock interactions within a few million years after parent-body formation6,7,8,9,10,11. However, the long-term fate of asteroidal water remains poorly understood. Here we present evidence for fluid flow in a carbonaceous asteroid more than 1 billion years after formation, based on the 176Lu–176Hf decay systematics of Ryugu samples, which reflect late lutetium mobilization. Such late fluid flow was probably triggered by an impact that generated heat for ice melting and opened rock fractures for fluid migration. This contrasts the early aqueous activity powered by short-lived radioactive decay, with limited fluid flow and little elemental fractionation12. Our results imply that carbonaceous planetesimals accreted by the terrestrial planets could have retained not only hydrous minerals but also aqueous water, leading to an upwards revision of the inventory of their water delivery by a factor of two to three.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$32.99 / 30 days
cancel any time
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on SpringerLink
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Data availability
The whole Ryugu Sample Database is available from the Hayabusa2 Science Data Archives (DARTS; https://www.darts.isas.jaxa.jp/curation/hayabusa2/). The data generated in this study are provided in the Extended Data tables and are publicly available on Zenodo at https://doi.org/10.5281/zenodo.16462056 (ref. 109). Source data are provided with this paper.
References
DeMeo, F. E. et al. Connecting asteroids and meteorites with visible and near-infrared spectroscopy. Icarus 380, 114971 (2022).
Trigo-Rodríguez, J. M., Rimola, A., Tanbakouei, S., Soto, V. C. & Lee, M. Accretion of water in carbonaceous chondrites: current evidence and implications for the delivery of water to early Earth. Space Sci. Rev. 215, 18 (2019).
Alexander, C. M. O. ’D. et al. The provenances of asteroids, and their contributions to the volatile inventories of the terrestrial planets. Science 337, 721–723 (2012).
Morbidelli, A., Lunine, J. I., O’Brien, D. P., Raymond, S. N. & Walsh, K. J. Building terrestrial planets. Ann. Rev. Earth Planet. Sci. 40, 251–275 (2012).
McCubbin, F. M. & Barnes, J. J. Origin and abundances of H2O in the terrestrial planets, Moon, and asteroids. Earth Planet. Sci. Lett. 526, 115771 (2019).
Ito, M. et al. A pristine record of outer Solar System materials from asteroid Ryugu’s returned sample. Nat. Astron. 6, 1163–1171 (2022).
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).
Nakamura, T. et al. Formation and evolution of carbonaceous asteroid Ryugu: direct evidence from returned samples. Science 379, eabn8671 (2022).
Yokoyama, T. et al. Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites. Science 379, eabn7850 (2022).
Yamaguchi, A. et al. Insight into multi-step geological evolution of C-type asteroids from Ryugu particles. Nat. Astron. 7, 398–405 (2023).
McCain, K. A. et al. Early fluid activity on Ryugu inferred by isotopic analyses of carbonates and magnetite. Nat. Astron. 7, 309–317 (2023).
Tang, H. et al. The oxygen isotopic composition of samples returned from asteroid Ryugu with implications for the nature of the parent planetesimal. Planet. Sci. J. 4, 144 (2023).
Sugita, S. et al. The geomorphology, color, and thermal properties of Ryugu: implications for parent-body processes. Science 364, eaaw0422 (2019).
Watanabe, S. et al. Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu—a spinning top-shaped rubble pile. Science 364, 268–272 (2019).
Tachibana, S. et al. Pebbles and sand on asteroid (162173) Ryugu: in situ observation and particles returned to Earth. Science 375, 1011–1016 (2022).
Hayakawa, T., Shizuma, T. & Iizuka, T. Half-life of the nuclear cosmochronometer 176Lu measured with a windowless 4π solid angle scintillation detector. Commun. Phys. 6, 299 (2023).
Patchett, P. J., Kouvo, O., Hedge, C. E. & Tatsumoto, M. Evolution of continental crust and mantle heterogeneity: evidence from Hf isotopes. Contrib. Mineral. Petrol. 78, 279–297 (1981).
Blichert-Toft, J. & Albarède, F. The Lu–Hf isotope geochemistry of chondrites and the evolution of the mantle–crust system. Earth Planet. Sci. Lett. 148, 243–258 (1997).
Scherer, E., Cameron, K. L. & Blichert-Toft, J. Lu–Hf garnet geochronology: closure temperature relative to the Sm–Nd system and the effects of trace mineral inclusions. Geochim. Cosmochim. Acta 64, 3413–3432 (2000).
Bizzarro, M., Baker, J. A., Haack, H., Ulfbeck, D. & Rosing, M. Early history of Earth’s crust–mantle system inferred from hafnium isotopes in chondrites. Nature 421, 931–933 (2003).
Patchett, P. J., Vervoort, J. D., Söderlund, U. & Salters, V. J. Lu–Hf and Sm–Nd isotopic systematics in chondrites and their constraints on the Lu–Hf properties of the Earth. Earth Planet. Sci. Lett. 222, 29–41 (2004).
Bouvier, A., Vervoort, J. D. & Patchett, P. J. The Lu–Hf and Sm–Nd isotopic composition of CHUR: constraints from unequilibrated chondrites and implications for the bulk composition of terrestrial planets. Earth Planet. Sci. Lett. 273, 48–57 (2008).
Dauphas, N. & Pourmand, A. Hf–W–Th evidence for rapid growth of Mars and its status as a planetary embryo. Nature 473, 489–492 (2011).
Tkalcec, B. J. et al. A comprehensive study of apatite grains in Ryugu rock fragments. Meteorit. Planet. Sci. 59, 2149–2165 (2024).
Morlok, A. et al. Brecciation and chemical heterogeneities of CI chondrites. Geochim. Cosmochim. Acta 70, 5371–5394 (2006).
Iizuka, T., Hibiya, Y., Yoshihara, S. & Hayakawa, T. Timescales of solar system formation based on Al–Ti isotope correlation by supernova ejecta. Astrophys. J. Lett. 979, L29 (2025).
Bizzarro, M., Connelly, J. N., Thrane, K. & Borg, L. E. Excess hafnium-176 in meteorites and the early Earth zircon record. Geochem. Geophys. Geosyst. 13, Q03002 (2012).
Albarède, F. et al. γ-ray irradiation in the early Solar System and the conundrum of the 176Lu decay constant. Geochim. Cosmochim. Acta 70, 1261–1270 (2006).
Thrane, K., Connelly, J. N., Bizzarro, M. & Meyer, B. S. Origin of excess 176Hf in meteorites. Astrophys. J. 717, 861–867 (2010).
Iizuka, T., Yamaguchi, T., Hibiya, Y. & Amelin, Y. Meteorite zircon constraints on the bulk Lu−Hf isotope composition and early differentiation of the Earth. Proc. Natl Acad. Sci. USA 112, 5331–5336 (2015).
Wimpenny, J., Amelin, Y. & Yin, Q.-Z. The Lu isotopic composition of achondrites: closing the case for accelerated decay of 176Lu. Astrophys. J. Lett. 812, L3 (2015).
Yin, Q.-Z., Lee, C. T. A. & Ott, U. Signatures of the s-process in presolar silicon carbide grains: barium through hafnium. Astrophy. J. 647, 676–684 (2006).
Qin, L., Carlson, R. W. & Alexander, C. M. O. ’D. Correlated nucleosynthetic isotopic variability in Cr, Sr, Ba, Sm, Nd and Hf in Murchison and QUE 97008. Geochim. Cosmochim. Acta 75, 7806–7828 (2011).
Bisterzo, S., Gallino, R., Straniero, O., Cristallo, S. & Käppeler, F. The s-process in low-metallicity stars–II. Interpretation of high-resolution spectroscopic observations with asymptotic giant branch models. Mon. Not. R. Astron. Soc. 418, 284–319 (2011).
Torrano, Z. A. et al. Neodymium-142 deficits and samarium neutron stratigraphy of C-type asteroid (162173) Ryugu. Meteorit. Planet. Sci. 59, 1966–1982 (2024).
Sprung, P., Kleine, T. & Scherer, E. E. Isotopic evidence for chondritic Lu/Hf and Sm/Nd of the Moon. Earth Planet. Sci. Lett. 380, 77–87 (2013).
Bloch, E., Watkins, J. & Ganguly, J. Diffusion kinetics of lutetium in diopside and the effect of thermal metamorphism on Lu–Hf systematics in clinopyroxene. Geochim. Cosmochim. Acta 204, 32–51 (2017).
Debaille, V., Van Orman, J., Yin, Q.-Z. & Amelin, Y. The role of phosphates for the Lu–Hf chronology of meteorites. Earth Planet. Sci. Lett. 473, 52–61 (2017).
Bast, R. et al. Reconciliation of the excess 176Hf conundrum in meteorites: recent disturbances of the Lu–Hf and Sm–Nd isotope systematics. Geochim. Cosmochim. Acta 212, 303–323 (2017).
Maeda, R. et al. The effects of Antarctic alteration and sample heterogeneity on Sm–Nd and Lu–Hf systematics in H chondrites. Geochim. Cosmochim. Acta 305, 106–129 (2021).
Bast, R., Scherer, E. E. & Bischoff, A. The 176Lu–176Hf systematics of ALM-A: a sample of the recent Almahata Sitta meteorite fall. Geochem. Persp. Lett. 3, 45–54 (2017).
Yokoyama, T. et al. The elemental abundances of Ryugu: assessment of chemical heterogeneities and the nugget effect. Geochem. J. 59, 45–63 (2025).
Dauphas, N. & Pourmand, A. Thulium anomalies and rare earth element patterns in meteorites and Earth: nebular fractionation and the nugget effect. Geochim. Cosmochim. Acta 163, 234–261 (2015).
Ota, T. et al. The formation of a rubble pile asteroid: Insights from the asteroid Ryugu. Universe 9, 293 (2023).
Turner, S., McGee, L., Humayun, M., Creech, J. & Zanda, B. Carbonaceous chondrite meteorites experienced fluid flow within the past million years. Science 371, 164–167 (2021).
McSween, H. Y. Jr Are carbonaceous chondrites primitive or processed? A review. Rev. Geophys. 17, 1059–1078 (1979).
Young, E. D., Zhang, K. K. & Schubert, G. Conditions for pore water convection within carbonaceous chondrite parent bodies—implications for planetesimal size and heat production. Earth Planet. Sci. Lett. 213, 249–259 (2003).
Bland, P. A. et al. Why aqueous alteration in asteroids was isochemical: high porosity ≠ high permeability. Earth Planet. Sci. Lett. 287, 559–568 (2009).
Vacher, L. G. et al. Hydrogen in chondrites: influence of parent body alteration and atmospheric contamination on primordial components. Geochim. Cosmochim. Acta 281, 53–66 (2020).
Suttle, M. D., Folco, L., Genge, M. J. & Russell, S. S. Flying too close to the Sun—the viability of perihelion-induced aqueous alteration on periodic comets. Icarus 351, 113956 (2020).
Nishiizumi, K. et al. Exposure conditions of samples collected on Ryugu’s two touchdown sites determined by cosmogenic nuclides 10Be and 26Al. In 53rd Lunar and Planetary Science Conference 1777 (2022).
Okazaki, R. et al. Noble gases and nitrogen in samples of asteroid Ryugu record its volatile sources and recent surface evolution. Science 379, eabo0431 (2022).
Grimm, R. E. & McSween, H. Y. Jr Water and the thermal evolution of carbonaceous chondrite parent bodies. Icarus 82, 244–280 (1989).
Campins, H. et al. Water ice and organics on the surface of the asteroid 24 Themis. Nature 464, 1320–1321 (2010).
Rivkin, A. S. & Emery, J. P. Detection of ice and organics on an asteroidal surface. Nature 464, 1322–1323 (2010).
Morota, T. et al. Sample collection from asteroid (162173) Ryugu by Hayabusa2: implications for surface evolution. Science 368, 654–659 (2020).
Naraoka, H. et al. Soluble organic molecules in samples of the carbonaceous asteroid (162173) Ryugu. Science 379, eabn9033 (2023).
Gautam, I., Yokoyama, T., Horan, M. F. & Carlson, R. W. Five-stage multielement separation procedure: a unique and essential tool for the multi-isotopic analyses of precious (<30 mg) extraterrestrial materials. Geochem. J. 59, 64–83 (2025).
Bizzarro, M. et al. The magnesium isotope composition of samples returned from asteroid Ryugu. Astrophys. J. Lett. 958, L25 (2023).
Hopp, T. et al. Ryugu’s nucleosynthetic heritage from the outskirts of the Solar System. Sci. Adv. 8, eadd8141 (2022).
Yokoyama, T. et al. Water circulation in Ryugu asteroid affected the distribution of nucleosynthetic isotope anomalies in returned sample. Sci. Adv. 9, eadi7048 (2023).
Nakanishi, N. et al. Nucleosynthetic s-process depletion in Mo from Ryugu samples returned by Hayabusa2. Geochem. Persp. Lett. 28, 31–36 (2023).
Moynier, F. et al. The Solar System calcium isotopic composition inferred from Ryugu samples. Geochem. Persp. Lett. 24, 1–6 (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).
Münker, C., Weyer, S., Scherer, E. & Mezger, K. Separation of high field strength elements (Nb, Ta, Zr, Hf) and Lu from rock samples for MC‐ICPMS measurements. Geochem. Geophys. Geosyst. https://doi.org/10.1029/2001GC000183 (2001).
Wimpenny, J. B., Amelin, Y. & Yin, Q.-Z. Precise determination of the lutetium isotopic composition in rocks and minerals using multicollector ICPMS. Anal. Chem. 85, 11258–11264 (2013).
Yokoyama, T., Nagai, Y., Hinohara, Y. & Mori, T. Investigating the influence of non-spectral matrix effects in the determination of twenty-two trace elements in rock samples by ICP-QMS. Geostand. Geoanal. Res. 41, 221–242 (2016).
Thirlwall, M. F. & Anczkiewicz, R. Multidynamic isotope ratio analysis using MC–ICP–MS and the causes of secular drift in Hf, Nd and Pb isotope ratios. Int. J. Mass Spectrom. 235, 59–81 (2004).
Völkening, J., Köppe, M. & Heumann, K. G. Tungsten isotope ratio determinations by negative thermal ionization mass spectrometry. Int. J. Mass. Spectrom. Ion Proc. 107, 361–368 (1991).
Iizuka, T., Eggins, S. M., McCulloch, M. T., Kinsley, L. P. J. & Morimer, G. E. Precise and accurate determination of 147Sm/144Nd and 143Nd/144Nd in monazite using laser ablation-MC-ICPMS. Chem. Geol. 282, 45–57 (2011).
Akram, W., Schönbächler, M., Sprung, P. & Vogel, N. Zirconium–hafnium isotope evidence from meteorites for the decoupled synthesis of light and heavy neutron-rich nuclei. Astrophys. J. 777, 169 (2013).
Elfers, B.-M. et al. Variable distribution of s-process Hf and W isotope carriers in chondritic meteorites—evidence from 174Hf and 180W. Geochim. Cosmochim. Acta 239, 346–362 (2018).
Sprung, P., Scherer, E. E., Upadhyay, D., Leya, I. & Mezger, K. Non-nucleosynthetic heterogeneity in non-radiogenic stable Hf isotopes: Implications for early Solar System chronology. Earth Planet. Sci. Lett. 295, 1–11 (2010).
Chen, X. et al. Methodologies for 176Lu–176Hf analysis of zircon grains from the Moon and beyond. ACS Earth Space Chem. 8, 36–53 (2024).
Nyquist, L. E. et al. 146Sm–142Nd formation interval for the lunar mantle. Geochim. Cosmochim. Acta 59, 2817–2837 (1995).
Mughabghab, S. F. Atlas of Neutron Resonances Vol. 2 (Elsevier, 2018).
Otuka, N. et al. Towards a more complete and accurate experimental nuclear reaction data library (EXFOR): International collaboration between Nuclear Reaction Data Centres (NRDC). Nucl. Data Sheets 120, 272–276 (2014).
Barrat, J. A. et al. Geochemistry of CI chondrites: major and trace elements, and Cu and Zn isotopes. Geochim. Cosmochim. Acta 83, 79–92 (2012).
Beer, H., Walter, G., Macklin, R. L. & Patchett, P. J. Neutron capture cross sections and solar abundances of 160, 161Dy, 170, 171Yb, 175,176Lu, and 176, 177Hf for the s-process analysis of the radionuclide 176Lu. Phy. Rev. C 30, 464–478 (1984).
Lodders, K. Relative atomic solar system abundances, mass fractions, and atomic masses of the elements and their isotopes, composition of the solar photosphere, and compositions of the major chondritic meteorite groups. Space Sci. Rev. 217, 44 (2021).
Macke, R. J., Consolmagno, G. J. & Britt, D. T. Density, porosity, and magnetic susceptibility of carbonaceous chondrites. Meteorit. Planet. Sci. 46, 1842–1862 (2011).
Tack, P. et al. Rare earth element identification and quantification in millimetre-sized Ryugu rock fragments from the Hayabusa2 space mission. Earth Planets Space 74, 146 (2022).
Shibuya, T. et al. Aqueous alteration in icy planetesimals: the effect of outward transport of gaseous hydrogen. Geochim. Cosmochim. Acta 374, 264–283 (2024).
Wolery, T. W. & Larek, R. L. Software User's Manual EQ3/6, Version 8.0 (Sandia National Laboratories, 2003).
Helgeson, H. C. Thermodynamics of hydrothermal systems at elevated temperatures and pressures. Am. J. Sci. 267, 729–804 (1969).
Helgeson, H. C. & Kirkham, D. H. Theoretical prediction of the thermodynamic behavior of aqueous electrolytes at high pressures and temperatures; II, Debye–Hückel parameters for activity coefficients and relative partial molal properties. Am. J. Sci. 274, 1199–1261 (1974).
Drummond, S. E. Boiling and Mixing of Hydrothermal Fluids: Chemical Effects on Mineral Precipitation. PhD thesis, Pennsylvania State Univ. (1981).
Johnson, J. W., Oelkers, E. H. & Helgeson, H. C. SUPCRT92: a software package for calculating the standard molal thermodynamic properties of minerals, gases, aqueous species, and reactions from 1 to 5000 bar and 0 to 1000 °C. Comput. Geosci. 18, 899–947 (1992).
Helgeson, H. C., Delany, J. M., Nesbitt, H. W. & Bird, D. K. Summary and critique of the thermodynamic properties of rock-forming minerals. Am. J. Sci. 278-A, 1–229 (1978).
Shock, E. L. & Helgeson, H. C. Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures: correlation algorithms for ionic species and equation of state predictions to 5 kb and 1000 °C. Geochim. Cosmochim. Acta 52, 2009–2036 (1988).
Shock, E. L., Helgeson, H. C. & Sverjensky, D. A. Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures: standard partial molal properties of inorganic neutral species. Geochim. Cosmochim. Acta 53, 2157–2183 (1989).
Shock, E. L. & Koretsky, C. M. Metal–organic complexes in geochemical processes: estimation of standard partial molal thermodynamic properties of aqueous complexes between metal cations and monovalent organic acid ligands at high pressures and temperatures. Geochim. Cosmochim. Acta 59, 1497–1532 (1995).
Shock, E. L., Sassani, D. C., Willis, M. & Sverjensky, D. A. Inorganic species in geologic fluids: correlations among standard molal thermodynamic properties of aqueous ions and hydroxide complexes. Geochim. Cosmochim. Acta 61, 907–950 (1997).
Sverjensky, D. A., Shock, E. L. & Helgeson, H. C. Prediction of the thermodynamic properties of aqueous metal complexes to 1000 °C and 5 kb. Geochim. Cosmochim. Acta 61, 1359–1412 (1997).
McCollom, T. M. & Bach, W. Thermodynamic constraints on hydrogen generation during serpentinization of ultramafic rocks. Geochim. Cosmochim. Acta 73, 856–875 (2009).
Zolotov, M. Y. Aqueous fluid composition in CI chondritic materials: Chemical equilibrium assessments in closed systems. Icarus 220, 713–729 (2012).
Brearly, A. J. in Meteorites and the Early Solar System II (eds Lauretta, D. S. & McSween, H. Y.) 587–624 (Univ. Arizona Press, 2006).
Zolensky, M. E. et al. CM chondrites exhibit the complete petrologic range from type 2 to 1. Geochim. Cosmochim. Acta 61, 5099–5115 (1997).
Clayton, R. N. & Mayeda, T. K. Oxygen isotope studies of carbonaceous chondrites. Geochim. Cosmochim. Acta 63, 2089–2104 (1999).
Zolensky, M., Barrett, R. & Browning, L. Mineralogy and composition of matrix and chondrule rims in carbonaceous chondrites. Geochim. Cosmochim. Acta 57, 3123–3148 (1993).
Cherniak, D. J. Rare earth element diffusion in apatite. Geochim. Cosmochim. Acta 64, 3871–3885 (2000).
Louvel, M., Etschmann, B., Guan, Q., Testemale, D. & Brugger, J. Carbonate complexation enhances hydrothermal transport of rare earth elements in alkaline fluids. Nat. Commun. 13, 1456 (2022).
Rai, D., Xia, Y., Hess, N. J., Strachan, D. M. & McGrail, B. P. Hydroxo and chloro complexes/ion interaction of Hf4+ and the solubility product of HfO2(am). J. Solution Chem. 30, 949–967 (2001).
Fujiya, W. et al. Carbonate record of temporal change in oxygen fugacity and gaseous species in asteroid Ryugu. Nat. Geosci. 16, 675–682 (2023).
Kita, N. T. et al. Disequilibrium oxygen isotope distribution among aqueously altered minerals in Ryugu asteroid returned samples. Meteorit. Planet. Sci. 59, 2097–2116 (2024).
Yoshimura, T. et al. Breunnerite grain and magnesium isotope chemistry reveal cation partitioning during aqueous alteration of asteroid Ryugu. Nat. Commun. 15, 6809 (2024).
Tsuchiyama, A. et al. Three-dimensional textures of Ryugu samples and their implications for the evolution of aqueous alteration in the Ryugu parent body. Geochim. Cosmochim. Acta 375, 146–172 (2024).
Postberg, F. et al. Detection of phosphates originating from Enceladus’s ocean. Nature 618, 489–493 (2023).
Iizuka, T. & Hayabusa2-initial-analysis chemistry team Repository: Late fluid flow in a primitive asteroid revealed by Lu–Hf isotopes in Ryugu [Dataset]. Zenodo https://doi.org/10.5281/zenodo.16462056 (2025).
Lodders, K. Solar System abundances and condensation temperatures of the elements. Astrophys. J. 591, 1220–1247 (2003).
Acknowledgements
We thank the National Museum of Natural History, France and the Smithsonian National Museum of Natural History for meteorite samples. We are grateful to T. Kogure, K. Hamano, H. Sakuma, Y. Takano, T. Yoshimura, and K. Hirose for discussions. Hayabusa2 was developed and built under the leadership of the Japan Aerospace Exploration Agency (JAXA), with contributions from the German Aerospace Center (DLR) 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 work was supported by Japan Society for the Promotion of Science KAKENHI grants (21KK0057, 22H00170).
Author information
Authors and Affiliations
Contributions
T.I., T. Yokoyama and H. Yurimoto designed this study. T. Yokoyama, I.G. and T.I. separated Hf and Lu from the matrix. M.K.H., K.T.M.I. and Y.H. supported the separation. T. Yokoyama and H.N. conducted the SOM extraction tests. T.I. and T. Yokoyama were responsible for data acquisition and interpretation. T. Shibuya carried out thermodynamic modelling. T.I. wrote the initial draft of the paper, with contributions from T.H., T. Shibuya and T. Yokoyama. The draft was edited by N.D., A.B., Y. Amelin, Q.-Z.Y., M.W., T.H., T. Yokoyama, K.T.M.I., Y.H., A.Y., H.N., S. Tachiband and H. Yurimoto. The paper was reviewed and approved by T.I., T. Shibuya, T.H., T. Yokoyama, I.G., M.K.H., K.T.M.I., Y.H., A.Y., Y. Abe, J.A., C.M.O’D.A, S.A., Y. Amelin, K.-i.B., M.B., A.B., R.W.C., M.C., B.-G.C., N.D., A.M.D., T.D.R., W.F., R.F., H. Hidaka, H. Homma, G.R.H., T.R.I., A.I., S.I., N.K., N.T.K., K.K., T.K., S.K., A.N.K., M.-C.L., Y.M., K.M., F.M., K.N., I.N., A. Nguyen, L.N., A.P., C.P., L.P., L.Q., S.R., N.S., M.S., L.T., H.T., K.T., Y. Terada, T.U., S.W., M.W., R.J.W., K. Yamashita, Q.-Z.Y., S.Y., H. Yui, A.-C.Z., 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. Saiki, S. Tanaka, F.T., Y. Tsuda, S.-i.W., M.Y., S. Tachiband and H. Yurimoto.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Peer review
Peer review information
Nature thanks Vinciane Debaille and Erik Scherer for their contribution to the peer review of this work. Peer reviewer reports are available.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended data figures and tables
Extended Data Fig. 1 Plot of ε178Hfcorr versus ε149Sm for Ryugu and carbonaceous chondrite samples.
The ε178Hfcorr values were calculated from measured ε180Hf and ε178Hf values using equation (4). The ε149Sm values are from ref. 35 Error ellipses represent the 95% confidence intervals. Also shown are predicted isotopic variations at different neutron fluence conditions. The dashed and dotted lines are loci of equal neutron fluences of thermal (Φ) and epithermal (Θ) neutrons, respectively.
Extended Data Fig. 2 Excess 176Hf produced by reactions with cosmogenic neutrons.
Contours of 176Hf/177Hf shifts arising from neutron-induced reactions are plotted as a function of thermal (Φ) and epithermal (Θ) neutron fluences. The contour interval is 0.2ε.
Extended Data Fig. 3 Schematics of the Lu–Hf isotopic evolution of an object subjected to secondary Lu-loss.
We consider the case in which the object formed at t0 and lost Lu with a proportion p at a time ∆t after the formation. a. Radioactive decay and loss of 176Lu. b. Radiogenic growth of 176Hf. c. 176Hf/177Hf versus 176Lu/177Hf isochron diagram. Subscripts ‘0’ and ‘sample’ refer to the initial (at t0) and present values in the object, respectively. Notation is the same as equation (1). The (176Hf/177Hf)0 value of the object can be regarded as the same as the meteorite zircon value30. The degree of apparent 176Hf excess (∆176Hfsample) is a function of the extent (p) and timing (∆t) of Lu-loss.
Extended Data Fig. 4 Timing and extent of Lu-loss to produce apparent excess 176Hf.
The Ryugu samples A0106 (a), C0107 (b), and C0108 (c) and the ungrouped carbonaceous chondrite Tagish Lake (d). Notation is the same as in Fig. 3. For Ryugu samples, the upper limits on the proportion of lost Lu are estimated to be 14–27%, and the resultant lower bounds on the interval between the parent body accretion and Lu-loss are 103 Myr.
Extended Data Fig. 5 Elemental abundance patterns of Ryugu and carbonaceous chondrite samples.
a. Elemental abundances normalized to the CI chondrite mean values80 are plotted on a log scale as a function of 50% condensation temperature110. For the SOM-extracted Ryugu samples A0106 and C0107, open symbols represent elements for which total yields of the SOM-extraction test using carbonaceous chondrites exceed 5% (Extended Data Table 3). The depletion of alkali elements in these samples compared to the pristine Ryugu samples A0106-A0107 and C0108 can be attributed to their leaching out with SOM, especially by water. b. REE abundances normalized to the CI chondrite mean values are plotted on a log scale in order of atomic number. For both a and b, the data for A0106-A0107 and C0108 are from ref. 9. The data from this work are listed in Extended Data Table 4.
Extended Data Fig. 6 Thermodynamic modeling of the aqueous alteration on the Ryugu parent body.
The volume fractions of minerals in the rock (a) and the mass fraction of water in the rock-fluid system (b) are plotted as a function of initial water/rock mass ratio.
Extended Data Fig. 7 A flowchart of series of sample processing by the Hayabusa2-initial-analysis chemistry team.
These chemical processes were applied for chemical and isotopic analyses of Ryugu and carbonaceous samples.
Extended Data Fig. 8 Lu isotope fractionation induced by Ln resin chromatography.
(a) Elution profile for Lu during the isotope fractionation experiment using the SPEX Lu standard solution. (b) Isotope composition of eluted Lu represented as δ176Lu with respect to the unprocessed standard. Open symbols represent data for individual elution fractions, whereas solid symbols show those for the cumulative elution fractions. Error bars plotted on δ176Lu for individual fractions represent the 2 s.e. internal precisions. Grey band expresses the 2 s.d. external reproducibility of analyses (n = 14) of the unprocessed standard. Elution fractions are as follow: 3.3-(i), the first elution with 14 mL of 3.3 M HCl; 3.3-(ii), the second elution with 4 mL of 3.3 M HCl; 6-(i) to 6-(V), the following successive elution sections with 0.5 mL of 6 M HCl; and 6-(vi), the last fraction eluted between 2.5 and 4.5 mL of 6 M HCl. The δ176Lu values changed from negative at early elution stages to positive at late elution stages. The observed variation is comparable to analytical uncertainties for Ryugu samples and an order of magnitude smaller than required to account for the observed 176Hf excesses by accelerated 176Lu decay.
Supplementary information
Source data
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Iizuka, T., Shibuya, T., Hayakawa, T. et al. Late fluid flow in a primitive asteroid revealed by Lu–Hf isotopes in Ryugu. Nature 646, 62–67 (2025). https://doi.org/10.1038/s41586-025-09483-0
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41586-025-09483-0
