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First compositional analysis of Ryugu samples by the MicrOmega hyperspectral microscope


The characterization of objects that have best preserved the mineralogical and molecular phases formed in the earliest stages of the Solar System evolution is key to understanding the processes that led to the formation of the planets in their diversity. The Hayabusa2 mission of the Japan Aerospace Exploration Agency has returned for the first time samples collected at the surface of a C-type asteroid, Ryugu1,2. They are now preserved at the Extraterrestrial Samples Curation Center of the Japan Aerospace Exploration Agency at the Institute of Space and Astronautical Science in Sagamihara, Japan, where they are submitted to a first round of purely non-destructive analyses. The MicrOmega hyperspectral microscope developed at the Institut d'Astrophysique Spatiale (Orsay, France), which operates in the near-infrared range (0.99–3.65 µm), is performing their mineralogical and molecular characterization down to the scale of a few tens of micrometres. Strong features at 2.7 µm (indicating their OH-rich content) and at 3.4 µm (diagnostic of the presence of organics) dominate at a global scale, but key distinctive signatures have been identified at a submillimetre scale. In particular, carbonates (a fraction of them enriched in iron) as well as NH-rich compounds have been detected. The occurrence of volatile-rich species, likely originating from the outer Solar System, would support Ryugu having preserved both pristine material and altered phases, which are now available for refined laboratory analyses with the potential to draw new insights into the formation and evolution paths of planetary bodies in our Solar System.

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Fig. 1: Bulk A and C reflectance spectra.
Fig. 2: 3.4 µm band variations at the scale of a few tens of microns.
Fig. 3: Examples of compositional heterogeneities at sub-mm scale.
Fig. 4: Example of carbonate detection.

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All the data related to this manuscript will be put on the Data ARchives and Transmission System (DARTS) after a one-year proprietary period.


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We are very grateful to have been invited by the Hayabusa2 Project to contribute to their outstanding mission. We thank the French space agency CNES for its full support. The Japan Society for the Promotion of Science (JSPS) provided support through KAKENHI grant no. 17H06459 (T.U. and T.O.) and grant no. 19K03958 (M.A.). We also acknowledge the JSPS Core-to-Core Program ‘International Network for Planetary Science’.

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V.H., M.C., B.C., G.L., L.L., J.-P.B. and C.P. contributed to the instrument development. T.Y., T.O., L.L., V.H., L.R., A.N., K.Y. G.L., J.-P.B., C.P., D.L. and R.B. contributed to the installation of the instrument in the Curation Facility and to the protocol development. L.R., V.H., C.L., J.-P.B. and C.P. contributed to the calibration. J.-P.B., C.P., V.H., L.R., T.Y., D.L., R.B., K.H., A.N., K.Y., C.L., T.L.P.-J., G.L., L.L., K.Kumagai., A.M. and M.N. participated in the operations. B.G., D.L., J.-P.B., L.R., R.B., C.P., K.H., A.N., K.Y., J.C., Y.L., T.L.P.-J., C.L., F.P. and A.A.-T. contributed to the data analysis and interpretation. J.-P.B., C.P. and R.B. wrote the draft of the manuscript. All authors were involved in the discussions of the results and the finalization of the manuscript.

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Correspondence to C. Pilorget.

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Peer review information Nature Astronomy thanks Beth Clark, Hannah Kaplan and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Pilorget, C., Okada, T., Hamm, V. et al. First compositional analysis of Ryugu samples by the MicrOmega hyperspectral microscope. Nat Astron 6, 221–225 (2022).

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