2021年, 日本地球化学会奨励賞　　　　　　　　　　　　　　　

Late fluid flow in a primitive asteroid revealed by Lu–Hf isotopes in Ryugu
Tsuyoshi Iizuka, Takazo Shibuya, Takehito Hayakawa, Tetsuya Yokoyama, Ikshu Gautam, Makiko K. Haba, Kengo T. M. Ito, Yuki Hibiya, Akira Yamaguchi, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Hiroshi Hidaka, Hisashi Homma, Gary R. Huss, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kazuko Motomura, Frédéric Moynier, Kazuhide Nagashima, Izumi Nakai, Ann Nguyen, Larry Nittler, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Nature, Springer Science and Business Media LLC, 2025年09月10日, ［査読有り］
研究論文（学術雑誌）

The variety and origin of materials accreted by Bennu’s parent asteroid
J. J. Barnes, A. N. Nguyen, F. A. J. Abernethy, K. Bajo, D. V. Bekaert, E. Bloch, G. A. Brennecka, H. Busemann, J. S. Cowpe, S. A. Crowther, M. Ek, L. J. Fawcett, M. A. Fehr, I. A. Franchi, E. Füri, J. D. Gilmour, M. M. Grady, R. C. Greenwood, P. Haenecour, N. Kawasaki, P. Koefoed, D. Krietsch, L. Le, K. M. Liszewska, C. Maden, J. Malley, Y. Marrocchi, B. Marty, L. A. E. Meyer, T. S. Peretyazhko, L. Piani, J. Render, S. S. Russell, M. Rüfenacht, N. Sakamoto, M. Schönbächler, Q. R. Shollenberger, L. Smith, K. Thomas-Keprta, A. B. Verchovsky, J. Villeneuve, K. Wang, K. C. Welten, J. Wimpenny, E. A. Worsham, H. Yurimoto, L. Zimmermann, X. Zhao, C. M. O’D. Alexander, M. Amini, A. Baczynski, P. Bland, L. E. Borg, R. Burgess, M. W. Caffee, L. C. Chaves, P. L. Clay, J. P. Dworkin, D. I. Foustoukos, D. P. Glavin, V. E. Hamilton, D. Hill, C. H. House, G. R. Huss, T. Ireland, C. E. Jilly, F. Jourdan, L. P. Keller, T. S. Kruijer, V. Lai, T. J. McCoy, K. Nagashima, K. Nishiizumi, R. Ogliore, I. J. Ong, S. M. Reddy, W. D. A. Rickard, S. Sandford, D. W. Saxey, N. Timms, D. Weis, Z. E. Wilbur, T. J. Zega, D. N. DellaGiustina, C. W. V. Wolner, H. C. Connolly, D. S. Lauretta
Nature Astronomy, Springer Science and Business Media LLC, 2025年08月22日, ［査読有り］
研究論文（学術雑誌）, Abstract

The first bodies to form in the Solar System acquired their materials from stars, the presolar molecular cloud and the protoplanetary disk. Asteroids that have not undergone planetary differentiation retain evidence of these primary accreted materials. However, geologic processes such as hydrothermal alteration can dramatically change their bulk mineralogy, isotopic compositions and chemistry. Here we analyse the elemental and isotopic compositions of samples from asteroid Bennu to uncover the sources and types of material accreted by its parent body. We show that some primary accreted materials escaped the extensive aqueous alteration that occurred on the parent asteroid, including presolar grains from ancient stars, organic matter from the outer Solar System or molecular cloud, refractory solids that formed close to the Sun, and dust enriched in neutron-rich Ti isotopes. We find Bennu to be richer in isotopically anomalous organic matter, anhydrous silicates, and light isotopes of K and Zn than its closest compositional counterparts, asteroid Ryugu and Ivuna-type (CI) carbonaceous chondrite meteorites. We propose that the parent bodies of Bennu, Ryugu and CI chondrites formed from a common but spatially and/or temporally heterogeneous reservoir of materials in the outer protoplanetary disk.

Mineralogical evidence for hydrothermal alteration of Bennu samples
T. J. Zega, T. J. McCoy, S. S. Russell, L. P. Keller, Z. Gainsforth, S. A. Singerling, V. R. Manga, C. Harrison, G. Libourel, B. S. Prince, K. Thomas-Keprta, A. King, M. Portail, V. Guigoz, V. Tu, L. Le, M. Thompson, M. C. Benner, N. A. Kerrison, J. J. Barnes, I. Ong, P. Haenecour, L. Chaves, L. Smith, M. Kontogiannis, N. Vega Santiago, D. Hill, Z. Zeszut, K. Domanik, Y.-J. Chang, C. M. Corrigan, S. Ray, L. R. Wardell, T. Gooding, T. R. Rose, H. C. Bates, P. F. Schofield, N. V. Almeida, T. Salge, J. Najorka, L. B. Seifert, N. Lunning, K. Righter, A. N. Nguyen, F. E. Brenker, S. A. Eckley, J. P. Dworkin, R. H. Jones, S. A. Sandford, M. A. Marcus, H. A. Bechtel, G. Dominguez, H. Yurimoto, N. Kawasaki, K. Bajo, N. Sakamoto, P.-M. Zanetta, S. Tachibana, H. Busemann, V. E. Hamilton, I. A. Franchi, M. Grady, R. C. Greenwood, K. Tait, N. Timms, P. Bland, F. Jourdan, S. M. Reddy, W. Rickard, D. Saxey, L. Vincze, H. C. Connolly, D. S. Lauretta
Nature Geoscience, Springer Science and Business Media LLC, 2025年08月22日, ［査読有り］
研究論文（学術雑誌）

Solar System’s earliest solids as tracers of the accretion region of Ryugu and Ivuna-type carbonaceous chondrites
Noriyuki Kawasaki, Sota Arakawa, Yushi Miyamoto, Naoya Sakamoto, Daiki Yamamoto, Sara S. Russell, Hisayoshi Yurimoto
Communications Earth & Environment, 6, 1, Springer Science and Business Media LLC, 2025年07月16日, ［査読有り］, ［筆頭著者, 責任著者］
研究論文（学術雑誌）

An overview of the petrography and petrology of particles from aggregate sample from asteroid Bennu
Harold C. Connolly, Dante S. Lauretta, Timothy J. McCoy, Sara S. Russell, Pierre Haenecour, Anjani Polit, Jessica J. Barnes, Thomas J. Zega, Hisayoshi Yurimoto, Noriyuki Kawasaki, Kevin Righter, Guy Libourel, Marc Portail, Vincent Guigoz, Ashley J. King, Lindsay P. Keller, Kathy Thomas‐Keprta, Loan Le, Valarie Tu, Scott A. Eckley, Catherine M. Corrigan, Timothy Gooding, Timothy Rose, Rob Wardell, Soumya Ray, Victoria E. Hamilton, Nicole G. Lunning, Christopher J. Snead, Francis M. McCubbin, Michelle S. Thompson, Rhian H. Jones, Kenneth Domanik, Dolores Hill, Lucas Smith, Iunn J. Ong, Tobias Salge, Natasha Almeida, Catherine Harrison, Helena Bates, Paul Schofield, Ian A. Franchi, Brian H. May, Claudia Manzoni, Andrew J. Ryan, Ronald‐Louis Ballouz, Robert J. Macke, Jason P. Dworkin, Charles C. Lorentson, Kimberly Tait, Erica R. Jawin, Hannah H. Kaplan, Daniella N. DellaGuistina, Kevin J. Walsh, Michael C. Moreau, Heather L. Enos, C. W. V. Wolner, Heather L. Roper, Shogo Tachibana
Meteoritics & Planetary Science, Wiley, 2025年03月20日, ［査読有り］
研究論文（学術雑誌）, Abstract

The OSIRIS‐REx mission returned a sample of regolith from the carbonaceous asteroid Bennu in September 2023. We present preliminary in situ investigations of the petrology and petrography of selected particles ranging in size from 0.5 to 3 mm. Using a combination of optical and electron beam techniques, we investigate whole specimens and polished sections belonging to morphologically and visually distinct categories of particles. We find that morphological differences in the particles are reflective of petrographic and petrologic differences, leading to the conclusion that we have at least two distinct major lithologies in the bulk sample. Our findings support predictions from remote sensing, suggesting that the morphological differences observed in the boulder population of Bennu correspond to petrologic differences. Our data provide insight into the geologic activity on Bennu's parent body and the petrographic framework needed to contextualize the detailed analyses of this pristine asteroidal material.

An evaporite sequence from ancient brine recorded in Bennu samples
T. J. McCoy, S. S. Russell, T. J. Zega, K. L. Thomas-Keprta, S. A. Singerling, F. E. Brenker, N. E. Timms, W. D. A. Rickard, J. J. Barnes, G. Libourel, S. Ray, C. M. Corrigan, P. Haenecour, Z. Gainsforth, G. Dominguez, A. J. King, L. P. Keller, M. S. Thompson, S. A. Sandford, R. H. Jones, H. Yurimoto, K. Righter, S. A. Eckley, P. A. Bland, M. A. Marcus, D. N. DellaGiustina, T. R. Ireland, N. V. Almeida, C. S. Harrison, H. C. Bates, P. F. Schofield, L. B. Seifert, N. Sakamoto, N. Kawasaki, F. Jourdan, S. M. Reddy, D. W. Saxey, I. J. Ong, B. S. Prince, K. Ishimaru, L. R. Smith, M. C. Benner, N. A. Kerrison, M. Portail, V. Guigoz, P.-M. Zanetta, L. R. Wardell, T. Gooding, T. R. Rose, T. Salge, L. Le, V. M. Tu, Z. Zeszut, C. Mayers, X. Sun, D. H. Hill, N. G. Lunning, V. E. Hamilton, D. P. Glavin, J. P. Dworkin, H. H. Kaplan, I. A. Franchi, K. T. Tait, S. Tachibana, H. C. Connolly, D. S. Lauretta
Nature, 637, 8048, 1072, 1077, Springer Science and Business Media LLC, 2025年01月29日, ［査読有り］
研究論文（学術雑誌）, Abstract

Evaporation or freezing of water-rich fluids with dilute concentrations of dissolved salts can produce brines, as observed in closed basins on Earth¹ and detected by remote sensing on icy bodies in the outer Solar System^2,3. The mineralogical evolution of these brines is well understood in regard to terrestrial environments⁴, but poorly constrained for extraterrestrial systems owing to a lack of direct sampling. Here we report the occurrence of salt minerals in samples of the asteroid (101955) Bennu returned by the OSIRIS-REx mission⁵. These include sodium-bearing phosphates and sodium-rich carbonates, sulfates, chlorides and fluorides formed during evaporation of a late-stage brine that existed early in the history of Bennu’s parent body. Discovery of diverse salts would not be possible without mission sample return and careful curation and storage, because these decompose with prolonged exposure to Earth’s atmosphere. Similar brines probably still occur in the interior of icy bodies Ceres and Enceladus, as indicated by spectra or measurement of sodium carbonate on the surface or in plumes^2,3.

Zirconium isotope composition indicates s‐process depletion in samples returned from asteroid Ryugu
Maria Schönbächler, Manuela A. Fehr, Tetsuya Yokoyama, Ikshu Gautam, Nao Nakanishi, Yoshinari Abe, Jérôme Aléon, Conel Alexander, Sachiko Amari, Yuri Amelin, Ken‐ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon‐Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming‐Chang Liu, Yuki Masuda, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara Russell, Naoya Sakamoto, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing‐Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai‐Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei‐ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Meteoritics & Planetary Science, Wiley, 2024年11月25日, ［査読有り］
研究論文（学術雑誌）, Abstract

Nucleosynthetic isotope variations are powerful tracers to determine genetic relationships between meteorites and planetary bodies. They can help to link material collected by space missions to known meteorite groups. The Hayabusa 2 mission returned samples from the Cb‐type asteroid (162173) Ryugu. The mineralogical, chemical, and isotopic characteristics of these samples show strong similarities to carbonaceous chondrites and in particular CI chondrites. The nucleosynthetic isotope compositions of Ryugu overlap with CI chondrites for several elements (e.g., Cr, Ti, Fe, and Zn). In contrast to these isotopes, which are of predominately supernovae origin, s‐process variations in Mo isotope data are similar to those of carbonaceous chondrites, but even more s‐process depleted. To further constrain the origin of this depletion and test whether this signature is also present for other s‐process elements, we report Zr isotope compositions for three bulk Ryugu samples (A0106, A0106‐A0107, C0108) collected from the Hayabusa 2 mission. The data are complemented with that of terrestrial rock reference materials, eucrites, and carbonaceous chondrites. The Ryugu samples are characterized by distinct ⁹⁶Zr enrichment relative to Earth, indicative of a s‐process depletion. Such depletion is also observed for carbonaceous chondrites and eucrites, in line with previous Zr isotope work, but it is more extreme in Ryugu, as observed for Mo isotopes. Since s‐process Zr and Mo are coupled in mainstream SiC grains, these distinct s‐process variations might be due to SiC grain depletion in the analyzed materials, potentially caused by incomplete sample digestion, because the Ryugu samples were dissolved on a hotplate only to avoid high blank levels for other elements (e.g., Cr). However, local depletion of SiC grains cannot be excluded. An alternative, equally possible scenario is that aqueous alteration redistributed anomalous, s‐process‐depleted, Zr on a local scale, for example, into Ca‐phosphates or phyllosilicates.

Oxygen Isotope Exchange between Dust Aggregates and Ambient Nebular Gas
Sota Arakawa, Daiki Yamamoto, Lily Ishizaki, Tamami Okamoto, Noriyuki Kawasaki
The Astrophysical Journal, 2024年10月01日, ［査読有り］, ［最終著者］
研究論文（学術雑誌）

Update on the 53Mn-53Cr ages of dolomite in the Ivuna CI chondrite and asteroid Ryugu sample
Shingo Sugawara, Wataru Fujiya, Noriyuki Kawasaki, Naoya Sakamoto, Akira Yamaguchi, Hisayoshi Yurimoto
Geochimica et Cosmochimica Acta, 382, 40, 50, Elsevier BV, 2024年10月, ［査読有り］
研究論文（学術雑誌）

The Ni isotopic composition of Ryugu reveals a common accretion region for carbonaceous chondrites
Fridolin Spitzer, Thorsten Kleine, Christoph Burkhardt, Timo Hopp, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel M. O’D Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Mayu Morita, Fréderic Moynier, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Science Advances, 10, 39, American Association for the Advancement of Science (AAAS), 2024年09月27日, ［査読有り］
研究論文（学術雑誌）, The isotopic compositions of samples returned from Cb-type asteroid Ryugu and Ivuna-type (CI) chondrites are distinct from other carbonaceous chondrites, which has led to the suggestion that Ryugu/CI chondrites formed in a different region of the accretion disk, possibly around the orbits of Uranus and Neptune. We show that, like for Fe, Ryugu and CI chondrites also have indistinguishable Ni isotope anomalies, which differ from those of other carbonaceous chondrites. We propose that this unique Fe and Ni isotopic composition reflects different accretion efficiencies of small FeNi metal grains among the carbonaceous chondrite parent bodies. The CI chondrites incorporated these grains more efficiently, possibly because they formed at the end of the disk’s lifetime, when planetesimal formation was also triggered by photoevaporation of the disk. Isotopic variations among carbonaceous chondrites may thus reflect fractionation of distinct dust components from a common reservoir, implying CI chondrites/Ryugu may have formed in the same region of the accretion disk as other carbonaceous chondrites.

Microscopic slickenside as a record of weak shock metamorphism in the surface layer of asteroid Ryugu
Masaaki Miyahara, Takaaki Noguchi, Toru Matsumoto, Naotaka Tomioka, Akira Miyake, Yohei Igami, Yusuke Seto, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Hope A. Ishii, John P. Bradley, Kenta K. Ohtaki, Elena Dobrică, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Peña, Sylvain Laforet, Bahae‐Eddine Mouloud, Maya Marinova, Falko Langenhorst, Dennis Harries, Pierre Beck, Thi H. V. Phan, Rolando Rebois, Neyda M. Abreu, Jennifer Gray, Thomas Zega, Pierre‐M. Zanetta, Michelle S. Thompson, Rhonda Stroud, Kate Burgess, Brittany A. Cymes, John C. Bridges, Leon Hicks, Martin R. Lee, Luke Daly, Phil A. Bland, Michael E. Zolensky, David R. Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Masanao Abe, Satoru Nakazawa, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Makoto Yoshikawa, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tomohiro Usui, Toru Yada, Hisayoshi Yurimoto, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamotoa, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei‐ichiro Watanabe, Yuichi Tsuda
Meteoritics & Planetary Science, Wiley, 2024年09月26日, ［査読有り］
研究論文（学術雑誌）, Abstract

The surface morphology of regolith grains from the C‐type asteroid Ryugu was studied in search of evidence of impact events on the asteroid. Scanning electron microscopy revealed that ~8% of C0105‐042 Ryugu grains have a smooth surface on one side of the grains. One of these grains has striated linear grooves (striations) on its smooth surface. Transmission electron microscopy of the grain showed that a porous fine‐grained Mg‐Fe phyllosilicate assemblage, which is the main component of Ryugu grains, is compacted near the smooth surface. The smooth surface with striations closely resembles a slickenside, a characteristic texture found in terrestrial fault rocks formed by shear deformation. There is no evidence of melting/decomposition in the Mg‐Fe phyllosilicates near the smooth surface, indicating that the shear heating temperature is less than ~1100 K. Assuming that the average length of the striations corresponds to the minimum displacement of the micro‐fault, the shock pressure recorded in the C0105‐042 Ryugu grain is estimated to be <~4.5 GPa by a fault mechanics calculation. The shock pressures of C0105‐042, together with those of C0014 (~2 GPa) and C0055 (>~3.9 GPa) in previous studies suggest that the impact velocities recorded in these grains are < ~0.89–1.63 km s⁻¹. Based on the impact velocities, these grains may record an impact event that occurred when asteroid Ryugu was in the orbit in Main Belt.

Condensation of refractory minerals on igneous compact type A Ca‐Al‐rich inclusion from Northwest Africa 7865 CV chondrite
Akimasa Suzumura, Noriyuki Kawasaki, Hisayoshi Yurimoto, Shoichi Itoh
Meteoritics & Planetary Science, 2024年09月, ［査読有り］
研究論文（学術雑誌）

Pyrrhotites in asteroid 162173 Ryugu: Records of the initial changes on their surfaces with aqueous alteration
Hiroharu Yui, Shu-hei Urashima, Morihiko Onose, Mayu Morita, Shintaro Komatani, Izumi Nakai, Yoshinari Abe, Yasuko Terada, Hisashi Homma, Kazuko Motomura, Kiyohiro Ichida, Tetsuya Yokoyama, Kazuhide Nagashima, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Peter Hoppe, Gary R. Huss, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Sasha Krot, Ming-Chang Liu, Yuki Masuda, Frédéric Moynier, Ann Nguyen, Larry Nittler, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Tommaso Di Rocco, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Geochimica et Cosmochimica Acta, 379, 172, 183, Elsevier BV, 2024年08月, ［査読有り］
研究論文（学術雑誌）

Disequilibrium oxygen isotope distribution among aqueously altered minerals in Ryugu asteroid returned samples
Noriko T. Kita, Kouki Kitajima, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamoto, Wataru Fujiya, Yoshinari Abe, Jérôme Aléon, Conel M. O'D. Alexander, Sachiko Amari, Yuri Amelin, Ken‐ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon‐Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming‐Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing‐Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai‐Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei‐ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Meteoritics & Planetary Science, 2024年08月, ［査読有り］
研究論文（学術雑誌）

Hydrogen in magnetite from asteroid Ryugu
J. Aléon, S. Mostefaoui, H. Bureau, D. Vangu, H. Khodja, K. Nagashima, N. Kawasaki, Y. Abe, C. M. O'D. Alexander, S. Amari, Y. Amelin, K. Bajo, M. Bizzarro, A. Bouvier, R. W. Carlson, M. Chaussidon, B.‐G. Choi, N. Dauphas, A. M. Davis, T. Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M. K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G. R. Huss, K. Ichida, T. Iizuka, T. R. Ireland, A. Ishikawa, S. Itoh, N. T. Kita, K. Kitajima, T. Kleine, S. Komatani, A. N. Krot, M.‐C. Liu, Y. Masuda, M. Morita, K. Motomura, F. Moynier, I. Nakai, A. Nguyen, L. R. Nittler, M. Onose, A. Pack, C. Park, L. Piani, L. Qin, S. S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada, T. Usui, S. Wada, M. Wadhwa, R. J. Walker, K. Yamashita, Q.‐Z. Yin, T. Yokoyama, S. Yoneda, E. D. Young, H. Yui, A.‐C. Zhang, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H. Yabuta, M. Abe, A. Miyazaki, A. Nakato, M. Nishimura, T. Okada, T. Yada, K. Yogata, S. Nakazawa, T. Saiki, S. Tanaka, F. Terui, Y. Tsuda, S. Watanabe, M. Yoshikawa, S. Tachibana, H. Yurimoto
Meteoritics & Planetary Science, 2024年08月, ［査読有り］
研究論文（学術雑誌）

An experimental simulation of oxygen isotope exchange reaction between amorphous silicate dust and carbon monoxide gas in the early Solar System
Daiki Yamamoto, Noriyuki Kawasaki, Shogo Tachibana, Lily Ishizaki, Ryosuke Sakurai, Hisayoshi Yurimoto
Geochimica et Cosmochimica Acta, 2024年06月, ［査読有り］
研究論文（学術雑誌）

In Situ Helium Isotope Microimaging of Meteorites
Ken-ichi Bajo, Noriyuki Kawasaki, Isao Sakaguchi, Taku T. Suzuki, Satoru Itose, Miyuki Matsuya, Morio Ishihara, Kiichiro Uchino, Hisayoshi Yurimoto
Analytical Chemistry, 96, 13, 5143, 5149, American Chemical Society (ACS), 2024年03月21日, ［査読有り］
研究論文（学術雑誌）

Pervasive aqueous alteration in the early Solar System revealed by potassium isotopic variations in Ryugu samples and carbonaceous chondrites
Yan Hu, Frédéric Moynier, Wei Dai, Marine Paquet, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel M. O'D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Mayu Morita, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Icarus, 409, 115884, 115884, Elsevier BV, 2024年02月, ［査読有り］
研究論文（学術雑誌）

In situ investigation of an organic micro‐globule and its mineralogical context within a Ryugu “sand” grain
Van T. H. Phan, Pierre Beck, Rolando Rebois, Eric Quirico, Takaaki Noguchi, Toru Matsumoto, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hope A. Ishii, John P. Bradley, Kenta K. Ohtaki, Elena Dobrică, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Peña, Sylvain Laforet, Maya Marinova, Falko Langenhorst, Dennis Harries, Neyda M. Abreu, Jennifer Gray, Thomas Zega, Pierre‐M. Zanetta, Michelle S. Thompson, Rhonda Stroud, Jérémie Mathurin, Alexandre Dazzi, Emmanuel Dartois, Cécile Engrand, Kate Burgess, Brittany A. Cymes, John C. Bridges, Leon Hicks, Martin R. Lee, Luke Daly, Phil A. Bland, Michael E. Zolensky, David R. Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Masanao Abe, Satoru Nakazawa, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Makoto Yoshikawa, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tomohiro Usui, Toru Yada, Hisayoshi Yurimoto, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamotoa, Peter Hoppe, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei‐ichiro Watanabe, Yuichi Tsuda
Meteoritics & Planetary Science, Wiley, 2024年01月08日, ［査読有り］
研究論文（学術雑誌）, Abstract

The Hayabusa2 mission from the Japan Aerospace Exploration Agency (JAXA) returned to the Earth samples of carbonaceous asteroid (162173) Ryugu. This mission offers a unique opportunity to investigate in the laboratory samples from a C‐type asteroid, without physical or chemical alteration by the terrestrial atmosphere. Here, we report on an investigation of the mineralogy and the organo‐chemistry of Hayabusa2 samples using a combination of micro‐ and nano‐infrared spectroscopy. Particles investigated with conventional FTIR spectroscopy have spectra dominated by phyllosilicate‐related absorption, as observed for samples of CI‐chondrites, selected ungrouped carbonaceous chondrites, and selected hydrated micrometeorites. Ryugu samples show smaller sulfate‐related absorption than CI‐chondrites. Our samples that were only briefly exposed to the Earth atmosphere show absorptions related to molecular water, revealing fast terrestrial contamination of the spectral signature at 3 μm. Overall, our FTIR data are in agreement with other work done on Ryugu samples, revealing a low degree of mineralogical variability across Ryugu samples. AFM‐IR mapping of the grains shows the presence of a micrometer‐sized organic globule in one of our analyzed grains. The AFM‐IR spectra obtained on this globule are similar to IR spectra obtained on IOM suggesting that it is constituted of refractory organic matter. This globule may host silicate in its interior, with a different mineralogy than bulk Ryugu phyllosilicate. The shape, presence of peculiar silicate, and the nature of organic constituting the globule point toward a pre‐accretionary origin of this globule and that at least part of Ryugu organics were inherited from the protosolar nebulae or the interstellar media. Altogether, our results show the similarities between Ryugu samples and CI chondrites.

Four‐dimensional‐STEM analysis of the phyllosilicate‐rich matrix of Ryugu samples
Bahae‐eddine Mouloud, Damien Jacob, Francisco de la Peña, Maya Marinova, Corentin Le Guillou, Jean‐Christophe Viennet, Sylvain Laforet, Hugues Leroux, Adrien Teurtrie, Takaaki Noguchi, Toru Matsumoto, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hope A. Ishii, John P. Bradley, Kenta K. Ohtaki, Elena Dobrica, Falko Langenhorst, Dennis Harries, Pierre Beck, Thi H. V. Phan, Rolando Rebois, Neyda M. Abreu, Jennifer Gray, Thomas Zega, Pierre‐M. Zanetta, Michelle S. Thompson, Rhonda Stroud, Kate Burgess, Brittany A. Cymes, John C. Bridges, Leon Hicks, Martin R. Lee, Luke Daly, Phil A. Bland, Michael E. Zolensky, David R. Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Masanao Abe, Satoru Nakazawa, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Makoto Yoshikawa, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tomohiro Usui, Toru Yada, Hisayoshi Yurimoto, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamotoa, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei‐ichiro Watanabe, Yuichi Tsuda
Meteoritics & Planetary Science, Wiley, 2024年01月05日, ［査読有り］
研究論文（学術雑誌）, Abstract

Ryugu asteroid grains brought back to the Earth by the Hayabusa2 space mission are pristine samples containing hydrated minerals and organic compounds. Here, we investigate the mineralogy of their phyllosilicate‐rich matrix with four‐dimensional scanning transmission electron microscopy (4D‐STEM). We have identified and mapped the mineral phases at the nanometer scale (serpentine, smectite, pyrrhotite), observed the presence of Ni‐bearing pyrrhotite, and identified the serpentine polymorph as lizardite, in agreement with the reported aqueous alteration history of Ryugu. Furthermore, we have mapped the d‐spacings of smectite and observed a broad distribution of values, ranging from 1 to 2 nm, with an average d‐spacing of 1.24 nm, indicating significant heterogeneity within the sample. Such d‐spacing variability could be the result of either the presence of organic matter trapped in the interlayers or the influence of various geochemical conditions at the submicrometer scale, suggestive of a range of organic compounds and/or changes in smectite crystal chemistry.

Analysis of Cation Composition in Dolomites on the Intact Particles Sampled from Asteroid Ryugu
Mayu Morita, Hiroharu Yui, Shu-hei Urashima, Morihiko Onose, Shintaro Komatani, Izumi Nakai, Yoshinari Abe, Yasuko Terada, Hisashi Homma, Kazuko Motomura, Kiyohiro Ichida, Tetsuya Yokoyama, Kazuhide Nagashima, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Peter Hoppe, Gary R. Huss, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Sasha Krot, Ming-Chang Liu, Yuki Masuda, Frédéric Moynier, Ann Nguyen, Larry Nittler, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Tommaso Di Rocco, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Analytical Chemistry, American Chemical Society (ACS), 2023年12月28日, ［査読有り］
研究論文（学術雑誌）

Neodymium‐142 deficits and samarium neutron stratigraphy of C‐type asteroid (162173) Ryugu
Zachary A. Torrano, Michelle K. Jordan, Timothy D. Mock, Richard W. Carlson, Ikshu Gautam, Makiko K. Haba, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel Alexander, Sachiko Amari, Yuri Amelin, Ken‐ichi Bajo, Martin Bizzarro, Audrey Bouvier, Marc Chaussidon, Byeon‐Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming‐Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing‐Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai‐Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei‐ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Meteoritics & Planetary Science, Wiley, 2023年12月07日, ［査読有り］
研究論文（学術雑誌）, Abstract

We report Nd and Sm isotopic compositions of four samples of Ryugu returned by the Hayabusa2 mission, including “A” (first touchdown) and “C” (second touchdown) samples, and several carbonaceous chondrites to evaluate potential genetic relationships between Ryugu and known chondrite groups and track the cosmic ray exposure history of Ryugu. We resolved Nd and Sm isotopic anomalies in small (<20 ng Nd and Sm) sample sizes via thermal ionization mass spectrometer using 10¹³ Ω amplifiers. Ryugu samples exhibit resolvable negative μ¹⁴²Nd values consistent with carbonaceous chondrite values, suggesting that Ryugu is related to the parent bodies of carbonaceous chondrites. Ryugu's negative μ¹⁴⁹Sm values are the result of exposure to galactic cosmic rays, as demonstrated by the correlation between ¹⁵⁰Sm/¹⁵²Sm and ¹⁴⁹Sm/¹⁵²Sm ratios that fall along the expected neutron capture correlation line. The neutron fluence calculated in the “A” samples (2.75 ± 1.94 × 10¹⁵ n cm⁻²) is slightly higher compared to the “C” samples (0.95 ± 2.04 × 10¹⁵ n cm⁻²), though overlapping within measurement uncertainty. The Sm results for Ryugu, at this level of precision, thus are consistent with a well‐mixed surface layer at least to the depths from which the “A” and “C” samples derive.

Nucleosynthetic s-Process Depletion in Mo from Ryugu samples returned by Hayabusa2
N. Nakanishi, T. Yokoyama, A. Ishikawa, R.J. Walker, Y. Abe, J. Aléon, C.M.O'D. Alexander, S. Amari, Y. Amelin, K.-I. Bajo, M. Bizzarro, A. Bouvier, R.W. Carlson, M. Chaussidon, B.-G. Choi, N. Dauphas, A.M. Davis, T. Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M.K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G.R. Huss, K. Ichida, T. Iizuka, T.R. Ireland, S. Itoh, N. Kawasaki, N.T. Kita, K. Kitajima, T. Kleine, S. Komatani, A.N. Krot, M.-C. Liu, Y. Masuda, M. Morita, K. Motomura, F. Moynier, I. Nakai, K. Nagashima, A. Nguyen, L. Nittler, M. Onose, A. Pack, C. Park, L. Piani, L. Qin, S.S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada, T. Usui, S. Wada, M. Wadhwa, K. Yamashita, Q.-Z. Yin, S. Yoneda, E.D. Young, H. Yui, A.-C. Zhang, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H. Yabuta, M. Abe, A. Miyazaki, A. Nakato, M. Nishimura, T. Okada, T. Yada, K. Yogata, S. Nakazawa, T. Saiki, S. Tanaka, F. Terui, Y. Tsuda, S.-I. Watanabe, M. Yoshikawa, S. Tachibana, H. Yurimoto
Geochemical Perspectives Letters, 28, 31, 36, European Association of Geochemistry, 2023年12月, ［査読有り］
研究論文（学術雑誌）

The Magnesium Isotope Composition of Samples Returned from Asteroid Ryugu
Martin Bizzarro, Martin Schiller, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Mayu Morita, Fréderic Moynier, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
The Astrophysical Journal Letters, 958, 2, L25, L25, American Astronomical Society, 2023年11月24日, ［査読有り］
研究論文（学術雑誌）, Abstract

The nucleosynthetic isotope composition of planetary materials provides a record of the heterogeneous distribution of stardust within the early solar system. In 2020 December, the Japan Aerospace Exploration Agency Hayabusa2 spacecraft returned to Earth the first samples of a primitive asteroid, namely, the Cb-type asteroid Ryugu. This provides a unique opportunity to explore the kinship between primitive asteroids and carbonaceous chondrites. We report high-precision μ²⁶Mg* and μ²⁵Mg values of Ryugu samples together with those of CI, CM, CV, and ungrouped carbonaceous chondrites. The stable Mg isotope composition of Ryugu aliquots defines μ²⁵Mg values ranging from –160 ± 20 ppm to –272 ± 30 ppm, which extends to lighter compositions relative to Ivuna-type (CI) and other carbonaceous chondrite groups. We interpret the μ²⁵Mg variability as reflecting heterogeneous sampling of a carbonate phase hosting isotopically light Mg (μ²⁵Mg ∼ –1400 ppm) formed by low temperature equilibrium processes. After correcting for this effect, Ryugu samples return homogeneous μ²⁶Mg* values corresponding to a weighted mean of 7.1 ± 0.8 ppm. Thus, Ryugu defines a μ²⁶Mg* excess relative to the CI and CR chondrite reservoirs corresponding to 3.8 ± 1.1 and 11.9 ± 0.8 ppm, respectively. These variations cannot be accounted for by in situ decay of ²⁶Al given their respective ²⁷Al/²⁴Mg ratios. Instead, it requires that Ryugu and the CI and CR parent bodies formed from material with a different initial ²⁶Al/²⁷Al ratio or that they are sourced from material with distinct Mg isotope compositions. Thus, our new Mg isotope data challenge the notion that Ryugu and CI chondrites share a common nucleosynthetic heritage.

Mineralogy and petrology of fine‐grained samples recovered from the asteroid (162173) Ryugu
Takaaki Noguchi, Toru Matsumoto, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hope A. Ishii, John P. Bradley, Kenta K. Ohtaki, Elena Dobrică, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Peña, Sylvain Laforet, Bahae‐Eddine Mouloud, Maya Marinova, Falko Langenhorst, Dennis Harries, Pierre Beck, Thi H. V. Phan, Rolando Rebois, Neyda M. Abreu, Jennifer Gray, Thomas Zega, Pierre‐M. Zanetta, Michelle S. Thompson, Rhonda Stroud, Kate Burgess, Brittany A. Cymes, John C. Bridges, Leon Hicks, Martin R. Lee, Luke Daly, Phil A. Bland, William A. Smith, Sam McFadzean, Pierre‐Etienne Martin, Paul A. J. Bagot, Dennis Fougerouse, David W. Saxey, Steven Reddy, William D. A. Rickard, Michael E. Zolensky, David R. Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Masanao Abe, Satoru Nakazawa, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Makoto Yoshikawa, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tomohiro Usui, Toru Yada, Hisayoshi Yurimoto, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamotoa, Peter Hoppe, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei‐ichiro Watanabe, Yuichi Tsuda
Meteoritics & Planetary Science, Wiley, 2023年11月22日, ［査読有り］
研究論文（学術雑誌）, Abstract

Samples returned from the carbonaceous asteroid (162173) Ryugu by the Hayabusa2 mission revealed that Ryugu is composed of materials consistent with CI chondrites and some types of space weathering. We report detailed mineralogy of the fine‐grained Ryugu samples allocated to our “Sand” team and report additional space weathering features found on the grains. The dominant mineralogy is composed of a fine‐grained mixture of Mg‐rich saponite and serpentine, magnetite, pyrrhotite, pentlandite, dolomite, and Fe‐bearing magnesite. These grains have mineralogy comparable to that of CI chondrites, showing severe aqueous alteration but lacking ferrihydrite and sulfate. These results are similar to previous works on large Ryugu grains. In addition to the major minerals, we also find many minerals that are rare or have not been reported among CI chondrites. Accessory minerals identified are hydroxyapatite, Mg‐Na phosphate, olivine, low‐Ca pyroxene, Mg‐Al spinel, chromite, manganochromite, eskolaite, ilmenite, cubanite, polydymite, transjordanite, schreibersite, calcite, moissanite, and poorly crystalline phyllosilicate. We also show scanning transmission electron microscope and scanning electron microscope compositional maps and images of some space‐weathered grains and severely heated and melted grains. Although our mineralogical results are consistent with that of millimeter‐sized grains, the fine‐grained fraction is best suited to investigate impact‐induced space weathering.

Phyllosilicates with embedded Fe‐based nanophases in Ryugu and Orgueil
Hugues Leroux, Corentin Le Guillou, Maya Marinova, Sylvain Laforet, Jean‐Christophe Viennet, Bahae‐Eddine Mouloud, Adrien Teurtrie, Francisco de la Peña, Damien Jacob, Daniel Hallatt, Mario Pelaez Fernandez, David Troadec, Takaaki Noguchi, Toru Matsumoto, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hope A. Ishii, John P. Bradley, Kenta K. Ohtaki, Elena Dobrică, Falko Langenhorst, Dennis Harries, Pierre Beck, Thi H. V. Phan, Rolando Rebois, Neyda M. Abreu, Jennifer Gray, Thomas Zega, Pierre‐M. Zanetta, Michelle S. Thompson, Rhonda Stroud, Kate Burgess, Brittany A. Cymes, John C. Bridges, Leon Hicks, Martin R. Lee, Luke Daly, Phil A. Bland, Michael E. Zolensky, David R. Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Masanao Abe, Satoru Nakazawa, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Makoto Yoshikawa, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tomohiro Usui, Toru Yada, Hisayoshi Yurimoto, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamotoa, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei‐Ichiro Watanabe, Yuichi Tsuda
Meteoritics & Planetary Science, Wiley, 2023年11月14日, ［査読有り］
研究論文（学術雑誌）, Abstract

Samples were recently collected from the carbonaceous asteroid (162173) Ryugu, by the Japan Aerospace Exploration Agency (JAXA) Hayabusa2 mission. They resemble CI chondrites material, thus showing clear evidence of extensive aqueous alteration attested by the widespread presence of a mixture of serpentine and saponite. We present here a scanning transmission electron microscopy study of the Ryugu dominant lithology of the phyllosilicate matrix at the nanometer scale, which we compare with that of the Orgueil CI chondrite. In both objects, the phyllosilicates are of comparable nature and texture, consisting of a mixture of small‐sized crystallites of serpentine and saponite. At the micrometer scale or less, the texture is an alternation of fine and coarse domains. The fine‐grained regions are dominated by saponite. In Ryugu, they enclose numerous Fe,Ni nanosulfides, whereas in Orgueil, S‐ and Ni‐rich ferrihydrite is abundant. The coarse‐grained regions contain more serpentine and no or little Fe,Ni sulfides or ferrihydrite. Scanning transmission x‐ray microscopy at the Fe‐L₃ edge also reveals that iron valency of phyllosilicates is higher and more homogeneous in Orgueil (~70% Fe³⁺) than in Ryugu (<50% Fe³⁺). We interpret the observed textures as being mostly a consequence of aqueous alteration, likely resulting from the replacement by phyllosilicates of submicrometric components, initially agglomerated by a primary accretion. The fine‐grained domains may result from the replacement of GEMS (GEMS—glass with embedded metal and sulfides) objects or from other types of nanometric assemblages of silicate and Fe‐based nanophases. On the other hand, the coarse‐grained regions may correspond to the replacement of anhydrous crystalline silicates of the olivine and pyroxene type. The major difference is the presence of Fe,Ni sulfides in Ryugu and of ferrihydrite and higher iron valency of phyllosilicates in Orgueil. This might be due to long‐term terrestrial weathering that would have destabilized the nanosulfides. We also explore an alternative scenario involving more oxidizing hydrothermal conditions on the Orgueil parent body.

Water circulation in Ryugu asteroid affected the distribution of nucleosynthetic isotope anomalies in returned sample
Tetsuya Yokoyama, Meenakshi Wadhwa, Tsuyoshi Iizuka, Vinai Rai, Ikshu Gautam, Yuki Hibiya, Yuki Masuda, Makiko K. Haba, Ryota Fukai, Rebekah Hines, Nicole Phelan, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Trevor Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Science Advances, 9, 45, American Association for the Advancement of Science (AAAS), 2023年11月10日, ［査読有り］
研究論文（学術雑誌）, Studies of material returned from Cb asteroid Ryugu have revealed considerable mineralogical and chemical heterogeneity, stemming primarily from brecciation and aqueous alteration. Isotopic anomalies could have also been affected by delivery of exogenous clasts and aqueous mobilization of soluble elements. Here, we show that isotopic anomalies for mildly soluble Cr are highly variable in Ryugu and CI chondrites, whereas those of Ti are relatively uniform. This variation in Cr isotope ratios is most likely due to physicochemical fractionation between ⁵⁴ Cr-rich presolar nanoparticles and Cr-bearing secondary minerals at the millimeter-scale in the bulk samples, likely due to extensive aqueous alteration in their parent bodies that occurred after Solar System birth. In contrast, Ti isotopes were marginally affected by this process. Our results show that isotopic heterogeneities in asteroids are not all nebular or accretionary in nature but can also reflect element redistribution by water.

The Oxygen Isotopic Composition of Samples Returned from Asteroid Ryugu with Implications for the Nature of the Parent Planetesimal
Haolan Tang, Edward D. Young, Lauren Tafla, Andreas Pack, Tommaso Di Rocco, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Kazuhide Nagashima, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
The Planetary Science Journal, 4, 8, 144, 144, American Astronomical Society, 2023年08月
研究論文（学術雑誌）, Abstract

We present oxygen isotopic analyses of fragments of the near-Earth C_b-type asteroid Ryugu returned by the Hayabusa2 spacecraft that reinforce the close correspondence between Ryugu and CI chondrites. Small differences between Ryugu samples and CI chondrites in ${ { \rm{\Delta } } }^{ { \prime} 17},{\rm{O } }$ can be explained at least in part by contamination of the latter by terrestrial water. The discovery that a randomly sampled C-complex asteroid is composed of CI-chondrite-like rock, combined with thermal models for formation prior to significant decay of the short-lived radioisotope ²⁶Al, suggests that if lithified at the time of alteration, the parent body was small (≪50 km radius). If the parent planetesimal was large (>50 km in radius), it was likely composed of high-permeability, poorly lithified sediment rather than consolidated rock.

Abundant presolar grains and primordial organics preserved in carbon-rich exogenous clasts in asteroid Ryugu
Ann. N. Nguyen, Prajkta Mane, Lindsay P. Keller, Laurette Piani, Yoshinari Abe, Jérôme Aléon, Conel M. O'D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Science Advances, 9, 28, American Association for the Advancement of Science (AAAS), 2023年07月14日, ［査読有り］
研究論文（学術雑誌）, Preliminary analyses of asteroid Ryugu samples show kinship to aqueously altered CI (Ivuna-type) chondrites, suggesting similar origins. We report identification of C-rich, particularly primitive clasts in Ryugu samples that contain preserved presolar silicate grains and exceptional abundances of presolar SiC and isotopically anomalous organic matter. The high presolar silicate abundance (104 ppm) indicates that the clast escaped extensive alteration. The 5 to 10 times higher abundances of presolar SiC (~235 ppm), N-rich organic matter, organics with N isotopic anomalies (1.2%), and organics with C isotopic anomalies (0.2%) in the primitive clasts compared to bulk Ryugu suggest that the clasts formed in a unique part of the protoplanetary disk enriched in presolar materials. These clasts likely represent previously unsampled outer solar system material that accreted onto Ryugu after aqueous alteration ceased, consistent with Ryugu’s rubble pile origin.

Carbonate record of temporal change in oxygen fugacity and gaseous species in asteroid Ryugu
Wataru Fujiya, Noriyuki Kawasaki, Kazuhide Nagashima, Naoya Sakamoto, Conel M. O’D. Alexander, Noriko T. Kita, Kouki Kitajima, Yoshinari Abe, Jérôme Aléon, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Nature Geoscience, 16, 8, 675, 682, Springer Science and Business Media LLC, 2023年07月10日, ［査読有り］
研究論文（学術雑誌）

26Al-26Mg chronology of high‐temperature condensate hibonite in a fine‐grained, Ca-Al-rich inclusion from reduced CV chondrite
Noriyuki Kawasaki, Daiki Yamamoto, Sohei Wada, Changkun Park, Hwayoung Kim, Naoya Sakamoto, Hisayoshi Yurimoto
Meteoritics & Planetary Science, Wiley, 2023年05月15日, ［査読有り］, ［筆頭著者, 責任著者］
研究論文（学術雑誌）

Hydrogen Isotopic Composition of Hydrous Minerals in Asteroid Ryugu
Laurette Piani, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamoto, Ken-ichi Bajo, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Liping Qin, Sara S. Russell, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
The Astrophysical Journal Letters, 946, 2, L43, L43, American Astronomical Society, 2023年04月01日, ［査読有り］
研究論文（学術雑誌）, Abstract

Rock fragments of the Cb-type asteroid Ryugu returned to Earth by the JAXA Hayabusa2 mission share mineralogical, chemical, and isotopic properties with the Ivuna-type (CI) carbonaceous chondrites. Similar to CI chondrites, these fragments underwent extensive aqueous alteration and consist predominantly of hydrous minerals likely formed in the presence of liquid water on the Ryugu parent asteroid. Here we present an in situ analytical survey performed by secondary ion mass spectrometry from which we have estimated the D/H ratio of Ryugu’s hydrous minerals, D/H_Ryugu, to be [165 ± 19] × 10⁻⁶, which corresponds to δD_Ryugu = +59 ± 121‰ (2σ). The hydrous mineral D/H_Ryugu’s values for the two sampling sites on Ryugu are similar; they are also similar to the estimated D/H ratio of hydrous minerals in the CI chondrites Orgueil and Alais. This result reinforces a link between Ryugu and CI chondrites and an inference that Ryugu’s samples, which avoided terrestrial contamination, are our best proxy to estimate the composition of water at the origin of hydrous minerals in CI-like material. Based on this data and recent literature studies, the contribution of CI chondrites to the hydrogen of Earth’s surficial reservoirs is evaluated to be ∼3%. We conclude that the water responsible for the alteration of Ryugu’s rocks was derived from water ice precursors inherited from the interstellar medium; the ice partially re-equilibrated its hydrogen with the nebular H₂ before being accreted on the Ryugu’s parent asteroid.

隕石の難揮発性包有物CAIのAl–Mg年代学
川﨑 教行
地球化学, 57, 1, 1, 12, 2023年03月25日, ［査読有り］, ［招待有り］, ［筆頭著者, 責任著者］
日本語, 研究論文（学術雑誌）

A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu
Takaaki Noguchi, Toru Matsumoto, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hope A. Ishii, John P. Bradley, Kenta K. Ohtaki, Elena Dobrică, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Peña, Sylvain Laforet, Maya Marinova, Falko Langenhorst, Dennis Harries, Pierre Beck, Thi H. V. Phan, Rolando Rebois, Neyda M. Abreu, Jennifer Gray, Thomas Zega, Pierre-M. Zanetta, Michelle S. Thompson, Rhonda Stroud, Kate Burgess, Brittany A. Cymes, John C. Bridges, Leon Hicks, Martin R. Lee, Luke Daly, Phil A. Bland, Michael E. Zolensky, David R. Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Masanao Abe, Masahiko Arakawa, Atsushi Fujii, Masahiko Hayakawa, Naru Hirata, Naoyuki Hirata, Rie Honda, Chikatoshi Honda, Satoshi Hosoda, Yu-ichi Iijima, Hitoshi Ikeda, Masateru Ishiguro, Yoshiaki Ishihara, Takahiro Iwata, Kousuke Kawahara, Shota Kikuchi, Kohei Kitazato, Koji Matsumoto, Moe Matsuoka, Yuya Mimasu, Akira Miura, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hirotaka Sawada, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Ryudo Tsukizaki, Koji Wada, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Ryohta Fukai, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Hiromichi Soejima, Ayako I. Suzuki, Tomohiro Usui, Toru Yada, Daiki Yamamoto, Kasumi Yogata, Miwa Yoshitake, Harold C. Connolly, Dante S. Lauretta, Hisayoshi Yurimoto, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamoto, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei-ichiro Watanabe, Yuichi Tsuda
Nature Astronomy, 7, 2, 170, 181, Springer Science and Business Media LLC, 2022年12月19日
研究論文（学術雑誌）

Oxygen isotopes of anhydrous primary minerals show kinship between asteroid Ryugu and comet 81P/Wild2
Noriyuki Kawasaki, Kazuhide Nagashima, Naoya Sakamoto, Toru Matsumoto, Ken-ichi Bajo, Sohei Wada, Yohei Igami, Akira Miyake, Takaaki Noguchi, Daiki Yamamoto, Sara S. Russell, Yoshinari Abe, Jérôme Aléon, Conel M, O'D. Alexander, Sachiko Amari, Yuri Amelin, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Irelan, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriko T. Kita, Kouki Kitajim, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Meenakshi Wadhw, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Science Advances, 8, 50, American Association for the Advancement of Science (AAAS), 2022年12月17日, ［査読有り］, ［筆頭著者, 責任著者］
研究論文（学術雑誌）, The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: ¹⁶ O-rich (associated with refractory inclusions) and ¹⁶ O-poor (associated with chondrules). Both the ¹⁶ O-rich and ¹⁶ O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward. The abundance ratios of the ¹⁶ O-rich to ¹⁶ O-poor minerals in Ryugu and CI chondrites are higher than in other carbonaceous chondrite groups but are similar to that of comet 81P/Wild2, suggesting that Ryugu and CI chondrites accreted in the outer Solar System closer to the accretion region of comets.

Contribution of Ryugu-like material to Earth’s volatile inventory by Cu and Zn isotopic analysis
Marine Paquet, Frederic Moynier, Tetsuya Yokoyama, Wei Dai, Yan Hu, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann N. Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Nature Astronomy, 7, 2, 182, 189, Springer Science and Business Media LLC, 2022年12月12日, ［査読有り］
研究論文（学術雑誌）

Ryugu’s nucleosynthetic heritage from the outskirts of the Solar System
Timo Hopp, Nicolas Dauphas, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Science Advances, 8, 46, eadd8141, American Association for the Advancement of Science (AAAS), 2022年11月18日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Little is known about the origin of the spectral diversity of asteroids and what it says about conditions in the protoplanetary disk. Here, we show that samples returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable from Ivuna-type (CI) chondrites, which are distinct from all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate that Ryugu and CI chondrites formed in a reservoir that was different from the source regions of other carbonaceous asteroids. Growth and migration of the giant planets destabilized nearby planetesimals and ejected some inward to be implanted into the Main Belt. In this framework, most carbonaceous chondrites may have originated from regions around the birthplaces of Jupiter and Saturn, while the distinct isotopic composition of CI chondrites and Ryugu may reflect their formation further away in the disk, owing their presence in the inner Solar System to excitation by Uranus and Neptune.

Oxygen isotope exchange kinetics between CAI melt and carbon monoxide gas: Implication for CAI formation in the earliest Solar System
Daiki Yamamoto, Noriyuki Kawasaki, Shogo Tachibana, Michiru Kamibayashi, Hisayoshi Yurimoto
Geochimica et Cosmochimica Acta, 336, 104, 112, 2022年11月, ［査読有り］
英語, 研究論文（学術雑誌）

The Solar System calcium isotopic composition inferred from Ryugu samples
F. Moynier, W. Dai, T. Yokoyama, Y. Hu, M. Paquet, Y. Abe, J. Aléon, C.M.O'D Alexander, S. Amari, Y. Amelin, K.-I. Bajo, M. Bizzarro, A. Bouvier, R.W. Carlson, M. Chaussidon, B.-G. Choi, N. Dauphas, A.M. Davis, T. Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M.K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G.R. Huss, K. Ichida, T. Iizuka, T.R. Ireland, A. Ishikawa, M. Ito, S. Itoh, N. Kawasaki, N.T. Kita, K. Kitajima, T. Kleine, S. Komatani, A.N. Krot, M.-C. Liu, Y. Masuda, K.D. McKeegan, M. Morita, K. Motomura, I. Nakai, K. Nagashima, D. Nesvorný, A. Nguyen, L. Nittler, M. Onose, A. Pack, C. Park, L. Piani, L. Qin, S.S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada, T. Usui, S. Wada, M. Wadhwa, R.J. Walker, K. Yamashita, Q.-Z. Yin, S. Yoneda, E.D. Young, H. Yui, A.-C. Zhang, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H. Yabuta, M. Abe, A. Miyazaki, A. Nakato, M. Nishimura, T. Okada, T. Yada, K. Yogata, S. Nakazawa, T. Saiki, S. Tanaka, F. Terui, Y. Tsuda, S.-I. Watanabe, M. Yoshikawa, S. Tachibana, H. Yurimoto
Geochemical Perspectives Letters, 24, 1, 6, European Association of Geochemistry, 2022年10月, ［査読有り］
研究論文（学術雑誌）

Presolar Stardust in Asteroid Ryugu
Jens Barosch, Larry R. Nittler, Jianhua Wang, Conel M. O'D Alexander, Bradley T. De Gregorio, Cecile Engrand, Yoko Kebukawa, Kazuhide Nagashima, Rhonda M. Stroud, Hikaru Yabuta, Yoshinari Abe, Jerome Aleon, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Laure Bejach, Martin Bizzarro, Lydie Bonal, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, George D. Cody, Emmanuel Dartois, Nicolas Dauphas, Andrew M. Davis, Alexandre Dazzi, Ariane Deniset-Besseau, Tommaso Di Rocco, Jean Duprat, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Minako Hashiguchi, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Kanami Kamide, Noriyuki Kawasaki, A. L. David Kilcoyne, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Mutsumi Komatsu, Alexander N. Krot, Ming-Chang Liu, Zita Martins, Yuki Masuda, Jeremie Mathurin, Kevin D. McKeegan, Gilles Montagnac, Mayu Morita, Smail Mostefaoui, Kazuko Motomura, Frederic Moynier, Izumi Nakai, Ann N. Nguyen, Takuji Ohigashi, Taiga Okumura, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Eric Quirico, Laurent Remusat, Sara S. Russell, Naoya Sakamoto, Scott A. Sandford, Maria Schonbachler, Miho Shigenaka, Hiroki Suga, Lauren Tafla, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Maximilien Verdier-Paoletti, Sohei Wada, Meenakshi Wadhwa, Daisuke Wakabayashi, Richard J. Walker, Katsuyuki Yamashita, Shohei Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa, Masahiro Nishimura, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Toru Yada, Kasumi Yogata, Makoto Yoshikawa, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Shogo Tachibana, Hisayoshi Yurimoto
ASTROPHYSICAL JOURNAL LETTERS, 935, 1, 2022年08月, ［査読有り］
英語, 研究論文（学術雑誌）

Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites
Tetsuya Yokoyama, Kazuhide Nagashima, Izumi Nakai, Edward D. Young, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Hiroharu Yui, Ai-Cheng Zhang, Harold C. Connolly, Dante S. Lauretta, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Masahiko Arakawa, Atsushi Fujii, Masahiko Hayakawa, Naoyuki Hirata, Naru Hirata, Rie Honda, Chikatoshi Honda, Satoshi Hosoda, Yu-ichi Iijima, Hitoshi Ikeda, Masateru Ishiguro, Yoshiaki Ishihara, Takahiro Iwata, Kosuke Kawahara, Shota Kikuchi, Kohei Kitazato, Koji Matsumoto, Moe Matsuoka, Tatsuhiro Michikami, Yuya Mimasu, Akira Miura, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hirotaka Sawada, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Yuichi Tsuda, Ryudo Tsukizaki, Koji Wada, Sei-ichiro Watanabe, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Hiromichi Soejima, Ayako Suzuki, Toru Yada, Daiki Yamamoto, Kasumi Yogata, Miwa Yoshitake, Shogo Tachibana, Hisayoshi Yurimoto
Science, 379, 6634, eabn7850, American Association for the Advancement of Science (AAAS), 2022年06月09日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measure the mineralogy, bulk chemical and isotopic compositions of Ryugu samples. They are mainly composed of materials similar to carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The samples consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37 ± 10°C, (Stat.) (Syst.) million years after formation of the first solids in the Solar System. After aqueous alteration, the Ryugu samples were likely never heated above ~100°C. The samples have a chemical composition that more closely resembles the Sun’s photosphere than other natural samples do.

Effect of Hydrogen Gas Pressure on Calcium–Aluminum-rich Inclusion Formation in the Protosolar Disk: a Laboratory Simulation of Open-system Melt Crystallization
Michiru Kamibayashi, Shogo Tachibana, Daiki Yamamoto, Noriyuki Kawasaki, Hisayoshi Yurimoto
The Astrophysical Journal Letters, 923, 1, L12, L12, American Astronomical Society, 2021年12月01日, ［査読有り］
研究論文（学術雑誌）, Abstract

Calcium–aluminum-rich inclusions (CAIs) are the oldest materials that formed in the protosolar disk. Igneous CAIs experienced melting and subsequent crystallization in the disk during which the evaporation of relatively volatile elements such as Mg and Si occurred. Evaporation from the melt would have played a significant role in the variation of chemical, mineralogical, and petrologic characteristics of the igneous CAIs. In this study, we investigated crystallization of CAI analog melt under disk-like low-pressure hydrogen (P_H2) conditions of 0.1, 1, and 10 Pa to constrain the pressure condition of the early solar system in which type B CAIs were formed. At P_H2 = 10 Pa, the samples were mantled by melilite crystals, as observed for type B1 CAIs. However, the samples heated at P_H2 = 0.1 Pa exhibited random distribution of melilite, as in type B2 CAIs. At the intermediate P_H2 of 1 Pa, type-B1-like structure formed when the cooling rate was 5°C hr⁻¹, whereas the formation of type-B2-like structure required a cooling rate faster than 20°C hr⁻¹. The compositional characteristics of melilite in type B1 and B2 CAIs could also be reproduced by experiments. The results of the present study suggest that P_H2 required for type-B1-like textural and chemical characteristics is greater than 1 Pa. The hydrogen pressure estimated in this study would impose an important constraint on the physical condition of the protosolar disk where type B CAIs were formed.

Inter- and intra-crystal quartz δ18O homogeneity at Okataina volcano, Aotearoa New Zealand: Implications for rhyolite genesis
May Sas, Phil Shane, Noriyuki Kawasaki, Naoya Sakamoto, Georg F. Zellmer, Hisayoshi Yurimoto
Journal of Volcanology and Geothermal Research, 421, 107430, 107430, 2021年11月, ［査読有り］
英語, 研究論文（学術雑誌）

An experimental study on oxygen isotope exchange reaction between CAI melt and low-pressure water vapor under simulated Solar nebular conditions
Daiki Yamamoto, Noriyuki Kawasaki, Shogo Tachibana, Michiru Kamibayashi, Hisayoshi Yurimoto
Geochimica et Cosmochimica Acta, 314, 108, 120, Elsevier BV, 2021年09月, ［査読有り］
研究論文（学術雑誌）

Oxygen and Al‐Mg isotopic constraints on cooling rate and age of partial melting of an Allende Type B CAI, Golfball
Noriyuki Kawasaki, Shoichi Itoh, Naoya Sakamoto, Steven B. Simon, Daiki Yamamoto, Hisayoshi Yurimoto
Meteoritics & Planetary Science, 56, 6, 1224, 1239, Wiley, 2021年06月07日, ［査読有り］, ［筆頭著者, 責任著者］, ［国際共著］
研究論文（学術雑誌）

Origin of minerals in akermanite-rich patch texture and oxygen isotopic evolution of compact Type A Ca-Al-rich inclusions from the Northwest Africa 7865 CV chondrite
Akimasa Suzumura, Noriyuki Kawasaki, Yusuke Seto, Hisayoshi Yurimoto, Shoichi Itoh
GEOCHIMICA ET COSMOCHIMICA ACTA, 303, 51, 65, 2021年06月, ［査読有り］
英語, 研究論文（学術雑誌）

Hydrogen isotopic exchange kinetics between organic matter and water: Implications for chemical evolution during meteorite parent body processing
Yoko Kebukawa, Sachio Kobayashi, Noriyuki Kawasaki, Ying Wang, Hisayoshi Yurimoto, George D. Cody
METEORITICS & PLANETARY SCIENCE, 56, 3, 440, 454, 2021年03月, ［査読有り］, ［国際共著］
英語, 研究論文（学術雑誌）

An effect of variations in relative sensitivity factors on Al-Mg systematics of Ca-Al-rich inclusions in meteorites with secondary ion mass spectrometry
Noriyuki Kawasaki, Changkun Park, Shigeyuki Wakaki, Hwayoung Kim, Sunyoung Park, Toshihiro Yoshimura, Kazuya Nagaishi, Hyun Na Kim, Naoya Sakamoto, Hisayoshi Yurimoto
GEOCHEMICAL JOURNAL, 55, 4, 283, 287, 2021年, ［査読有り］, ［筆頭著者, 責任著者］, ［国際共著］
英語, 研究論文（学術雑誌）

Isotope Microscopic Observation of Osteogenesis Process Forming Robust Bonding of Double Network Hydrogel to Bone.
Takayuki Nonoyama, Lei Wang, Masumi Tsuda, Yuki Suzuki, Ryuji Kiyama, Kazunori Yasuda, Shinya Tanaka, Kousuke Nagata, Ryosuke Fujita, Naoya Sakamoto, Noriyuki Kawasaki, Hisayoshi Yurimoto, Jian Ping Gong
Advanced healthcare materials, 10, 3, e2001731, 2020年11月16日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Tough double network (DN) hydrogels are promising substitutes of soft supporting tissues such as cartilage and ligaments. For such applications, it is indispensable to robustly fix the hydrogels to bones with medically feasible methods. Recently, robustly bonding the DN hydrogels to defected bones of rabbits in vivo has been proved successful. The low crystalline hydroxyapatite (HAp) of calcium-phosphate-hydroxide salt coated on the surface layer of the DN hydrogels induced spontaneous osteogenesis penetrating into the semi-permeable hydrogels to form a gel/bone composite layer. In this work, the 44 Ca isotope-doped HAp/DN hydrogel is implanted in a defect of rabbit femoral bone and the dynamic osteogenesis process at the gel/bone interface is analyzed by tracing the calcium isotope ratio using isotope microscopy. The synthetic HAp hybridized on the surface layer of DN gel dissolves rapidly in the first two weeks by inflammation, and then the immature bone with a gradient structure starts to form in the gel region, reutilizing the dissolved Ca ions. These results reveal, for the first time, that synthetic HAp is reutilized for osteogenesis. These facts help to understand the lifetime of bone absorbable materials and to elucidate the mechanism of spontaneous, non-toxic, but strong fixation of hydrogels to bones.

Melilite condensed from an O-16-poor gaseous reservoir: Evidence from a fine-grained Ca-Al-rich inclusion of Northwest Africa 8613
Sohei Wada, Noriyuki Kawasaki, Changkun Park, Hisayoshi Yurimoto
GEOCHIMICA ET COSMOCHIMICA ACTA, 288, 161, 175, 2020年11月, ［査読有り］, ［国際共著］
英語, 研究論文（学術雑誌）

Mineralogical and oxygen isotopic study of a new ultrarefractory inclusion in the Northwest Africa 3118 CV3 chondrite
Yong Xiong, Ai-Cheng Zhang, Noriyuki Kawasaki, Chi Ma, Naoya Sakamoto, Jia-Ni Chen, Li-Xin Gu, Hisayoshi Yurimoto
METEORITICS & PLANETARY SCIENCE, 55, 10, 2184, 2205, 2020年10月, ［査読有り］, ［国際共著］
英語, 研究論文（学術雑誌）

Variations in initial Al-26/Al-27 ratios among fine-grained Ca-Al-rich inclusions from reduced CV chondrites
Noriyuki Kawasaki, Sohei Wada, Changkun Park, Naoya Sakamoto, Hisayoshi Yurimoto
GEOCHIMICA ET COSMOCHIMICA ACTA, 279, 1, 15, 2020年06月, ［査読有り］, ［筆頭著者, 責任著者］, ［国際共著］
英語, 研究論文（学術雑誌）

Survivability of presolar oxygen isotopic signature of amorphous silicate dust in the protosolar disk
Daiki Yamamoto, Shogo Tachibana, Noriyuki Kawasaki, Hisayoshi Yurimoto
METEORITICS & PLANETARY SCIENCE, 55, 6, 1281, 1292, 2020年06月, ［査読有り］
英語, 研究論文（学術雑誌）

Unique angrite-like fragments in a CH3 chondrite reveal a new basaltic planetesimal
Ai-Cheng Zhang, Noriyuki Kawasaki, Minami Kuroda, Yang Li, Hua-Pei Wang, Xue-Ning Bai, Naoya Sakamoto, Qing-Zhu Yin, Hisayoshi Yurimoto
GEOCHIMICA ET COSMOCHIMICA ACTA, 275, 48, 63, 2020年04月, ［査読有り］, ［国際共著］
英語, 研究論文（学術雑誌）

Evidence of metasomatism in the interior of Vesta
Ai-Cheng Zhang, Noriyuki Kawasaki, Huiming Bao, Jia Liu, Liping Qin, Minami Kuroda, Jian-Feng Gao, Li-Hui Chen, Ye He, Naoya Sakamoto, Hisayoshi Yurimoto
NATURE COMMUNICATIONS, 11, 1, 2020年03月, ［査読有り］, ［国際共著］
英語, 研究論文（学術雑誌）

Combined U-corrected Pb-Pb dating and Al-26-Mg-26 systematics of individual chondrules - Evidence for a reduced initial abundance of Al-26 amongst inner Solar System chondrules
Jean Bollard, Noriyuki Kawasaki, Naoya Sakamoto, Mia Olsen, Shoichi Itoh, Kirsten Larsen, Daniel Wielandt, Martin Schiller, James N. Connelly, Hisayoshi Yurimoto, Martin Bizzarro
GEOCHIMICA ET COSMOCHIMICA ACTA, 260, 62, 83, 2019年09月, ［査読有り］, ［国際共著］
英語, 研究論文（学術雑誌）

The ion microprobe as a tool for obtaining strontium isotopes in magmatic plagioclase: A case study at Okataina Volcanic Centre, New Zealand
May Sas, Noriyuki Kawasaki, Naoya Sakamoto, Phil Shane, Georg F. Zellmer, Adam J. R. Kent, Hisayoshi Yurimoto
CHEMICAL GEOLOGY, 513, 153, 166, 2019年05月, ［査読有り］, ［国際共著］
英語, 研究論文（学術雑誌）

Variations in initial Al-26/Al-27 ratios among fluffy Type A Ca-Al-rich inclusions from reduced CV chondrites
Noriyuki Kawasaki, Changkun Park, Naoya Sakamoto, Sun Young Park, Hyun Na Kim, Minami Kuroda, Hisayoshi Yurimoto
EARTH AND PLANETARY SCIENCE LETTERS, 511, 25, 35, 2019年04月, ［査読有り］, ［筆頭著者, 責任著者］, ［国際共著］
英語, 研究論文（学術雑誌）

Crystal growth and disequilibrium distribution of oxygen isotopes in an igneous Ca-Al-rich inclusion from the Allende carbonaceous chondrite
Noriyuki Kawasaki, Steven B. Simon, Lawrence Grossman, Naoya Sakamoto, Hisayoshi Yurimoto
GEOCHIMICA ET COSMOCHIMICA ACTA, 221, 318, 341, 2018年01月, ［査読有り］, ［筆頭著者, 責任著者］, ［国際共著］
英語, 研究論文（学術雑誌）

Chronological study of oxygen isotope composition for the solar protoplanetary disk recorded in a fluffy Type A CAI from Vigarano
Noriyuki Kawasaki, Shoichi Itoh, Naoya Sakamoto, Hisayoshi Yurimoto
GEOCHIMICA ET COSMOCHIMICA ACTA, 201, 201, 83, 102, 2017年03月, ［査読有り］, ［筆頭著者, 責任著者］
英語, 研究論文（学術雑誌）

Al-26-Mg-26 chronology and oxygen isotope distributions of multiple melting for a Type C CAI from Allende
Noriyuki Kawasaki, Chizu Kato, Shoichi Itoh, Shigeyuki Wakaki, Motoo Ito, Hisayoshi Yurimoto
GEOCHIMICA ET COSMOCHIMICA ACTA, 169, 99, 114, 2015年11月, ［査読有り］, ［筆頭著者, 責任著者］
英語, 研究論文（学術雑誌）

Synthesis of large and homogeneous single crystals of water-bearing minerals by slow cooling at deep-mantle pressures
Takuo Okuchi, Narangoo Purevjav, Naotaka Tomioka, Jung-Fu Lin, Takahiro Kuribayashi, Louise Schoneveld, Huijeong Hwang, Naoya Sakamoto, Noriyuki Kawasaki, Hisayoshi Yurimoto
AMERICAN MINERALOGIST, 100, 7, 1483, 1492, 2015年07月, ［査読有り］, ［国際共著］
英語, 研究論文（学術雑誌）

Oxygen isotopic and chemical zoning of melilite crystals in a type A Ca-Al-rich inclusion of Efremovka CV3 chondrite
Noriyuki Kawasaki, Naoya Sakamoto, Hisayoshi Yurimoto
METEORITICS & PLANETARY SCIENCE, 47, 12, 2084, 2093, 2012年12月, ［査読有り］, ［筆頭著者, 責任著者］
英語, 研究論文（学術雑誌）

Oxygen Isotopic Compositions of Asteroidal Materials Returned from Itokawa by the Hayabusa Mission
Hisayoshi Yurimoto, Ken-ichi Abe, Masanao Abe, Mitsuru Ebihara, Akio Fujimura, Minako Hashiguchi, Ko Hashizume, Trevor R. Ireland, Shoichi Itoh, Juri Katayama, Chizu Kato, Junichiro Kawaguchi, Noriyuki Kawasaki, Fumio Kitajima, Sachio Kobayashi, Tatsuji Meike, Toshifumi Mukai, Keisuke Nagao, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Changkun Park, Naoya Sakamoto, Yusuke Seto, Masashi Takei, Akira Tsuchiyama, Masayuki Uesugi, Shigeyuki Wakaki, Toru Yada, Kosuke Yamamoto, Makoto Yoshikawa, Michael E. Zolensky
SCIENCE, 333, 6046, 1116, 1119, 2011年08月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

原始太陽系円盤における物質の時空間分布と輸送作用の解明
科学研究費助成事業
2025年04月 - 2029年03月
川崎 教行, 荒川 創太, 馬上 謙一, 山本 大貴, 坂本 直哉
日本学術振興会, 基盤研究(A), 北海道大学, 研究代表者, 25H00678

太陽系最古の物質の酸化還元状態から解き明かす円盤物理化学環境
科学研究費助成事業
2024年09月 - 2029年03月
川崎 教行, 山本 大貴, 荒川 創太
日本学術振興会, 国際共同研究加速基金(海外連携研究), 北海道大学, 研究代表者, 24KK0072

古代中国の失われた漆芸技法とその復元への挑戦
科学研究費助成事業
2025年06月27日 - 2028年03月31日
若木 重行, 高橋 嘉夫, 川崎 教行, 岡田 文男, 橋口 未奈子
日本学術振興会, 挑戦的研究(萌芽), 国立歴史民俗博物館, 25K21870

三つの消滅核種の存在⽐から迫る原始太陽周囲での原⼦核反応プロセス　　　　　　　　　　　　　　　
基礎科学研究助成
2024年11月 - 2026年10月
川崎 教行
住友財団, 研究代表者, 2402563

小惑星サンプルに含まれる惑星材料物質の形成年代の測定　　　　　　　　　　　　　　　
研究助成
2024年09月 - 2026年08月
川崎 教行
日揮・実吉奨学会, 研究代表者

微惑星における水の活動時期の年代測定　　　　　　　　　　　　　　　
科学研究費助成事業 挑戦的研究(萌芽)
2022年06月 - 2025年03月
川崎 教行
日本学術振興会, 挑戦的研究(萌芽), 北海道大学, 研究代表者, 22K18722

初期太陽系における微惑星の形成年代の測定　　　　　　　　　　　　　　　
研究援助
2022年08月 - 2024年03月
川崎 教行
山田科学振興財団, 研究代表者

小惑星リュウグウの進化史の解明　　　　　　　　　　　　　　　
若手研究人材・ネットワーク育成補助金（ノースタレント補助金）
2022年08月 - 2023年03月
川崎 教行
北海道科学技術総合振興センター ノーステック財団, 研究代表者

個々のプレソーラー粒子の希ガス同位体分析による星間滞留環境の解明
科学研究費助成事業
2020年04月 - 2023年03月
馬上 謙一, 川崎 教行
プレソーラー炭化ケイ素(SiC)は炭素星やAGB星の星周で形成したと考えられている. これらの星では太陽系とは異なる核反応が進行しているため，太陽系とは異なる同位体組成を持つ．またこれらの星周で形成したSiCは高エネルギー粒子を含む恒星風や星間での銀河宇宙線が照射されていると考えられる．SiCに残されている恒星風起源希ガスの深さ方向のプロファイルは恒星風のエネルギーを反映していると考えられる．本研究では同位体ナノスコープを用いたプレソーラーSiC中のHe測定を行い，深さ方向の分布を測定した．
プレソーラーSiCはMurchison 隕石から抽出したKJGグループを用いた．
SiCスタンダード基盤を用いて，He-4， C-12，13， Si-28, 29, 30が定量できるような同位体ナノスコープの分析条件を確立した．そして，KJG粒子の深さ方向分析によってHe-4の深さ方向の分布を見積もることができた．KJGのHe-4深さ方向分析の結果，主要元素であるSiとCはスタンダードと同様のイオン強度が一定なプロファイルが得られた．そして， He-4もKJGから検出され，更に，深さ方向に分布が見られた．これは恒星風がHeイオン注入されていることを示唆しており，初めて実験的に太陽系外の恒星風を検証する手法を提示することができた．
現在の同位体ナノスコープでの炭素・シリコン同位体比測定精度はプレソーラーSiCが持っている同位体異常と同程度であることがわかった．SiとCの同位体は，SiCが形成した恒星の化学組成や大きさに依存しているため，SiCの形成環境を知る重要な手掛かりとなる．そのため，SiCの起源決定には，CAMECA ims-1280HR を用いた高精度Si，C同位体比測定を行うことにした．
日本学術振興会, 基盤研究(C), 北海道大学, 研究分担者, 20K04036

太陽型から地球型への星間ダストの変身
科学研究費助成事業
2019年04月 - 2023年03月
橘 省吾, 瀧川 晶, 川崎 教行, 圦本 尚義
本研究では「太陽型ダスト」から「地球型ダスト」への星間ダストの変身を担った太陽系最初期の化学過程(地球型ダストの誕生)に注目し，太陽系最初期のケイ酸塩・酸化物ダストとガス（H2O, CO）との酸素同位体交換反応の速度やメカニズムを実験で決定し，酸素同位体交換に必要な原始惑星系円盤の物理化学条件を定量的に決定する．また，酸素同位体交換反応によって，酸素同位体組成は地球型になったが，金属元素同位体組成は恒星周ダストのままである（円盤ガス中の金属元素存在度は低く，同位体交換が進まない）太陽系原材料ダストを始原隕石中に発見し，初期太陽系での酸素同位体交換反応による地球型ダスト誕生過程の証明をめざす（これまでの分析手法では，発見が困難であった）．今年度は，FeOを含むかんらん石組成の非晶質ケイ酸塩の結晶化速度の決定に加え，酸素同位体交換速度の推定をおこなった．FeOを含むかんらん石組成の非晶質ケイ酸塩の結晶化速度は，FeOを含まないかんらん石組成の非晶質ケイ酸塩に比べ，3-4桁結晶化速度が速いが，酸素同位体交換速度は一桁程度しか速くないことが予察的結果として，得られた．この結果はFeOを含むかんらん石組成の非晶質ケイ酸塩は原始惑星系円盤で結晶化が速やかに起こり，酸素同位体交換が十分に起きない可能性を示す．すなわち，このような組成のダストが初期太陽系には存在しなかった（非晶質ケイ酸塩への鉄の混入は小天体形成後に起きた）ことを示唆する．酸素同位体交換速度の決定を今後進める．また，一酸化炭素と非晶質ケイ酸塩との酸素同位体交換実験，非晶質アルミナと水蒸気の酸素同位体交換実験も進めた．
日本学術振興会, 基盤研究(A), 東京大学, 研究分担者, 19H00712

太陽系円盤における高温形成ダストの凝縮生成プロセスの年代学的研究
科学研究費助成事業
2018年04月 - 2020年03月
川崎 教行
初期太陽系円盤の高温のガスから凝縮したダストの形成年代を系統的に測定し，その分布を明らかにすることが研究の目的である。始原的なコンドライト隕石に含まれる細粒CAI（Ca-Al-rich inclusion）は，約1700-1400 Kの太陽組成ガスから凝縮した鉱物の集合体であるといわれている。本研究では，始原的なコンドライト隕石である，CV3 reducedコンドライト中の細粒CAIのAl-Mg形成年代を，二次イオン質量分析法による局所同位体分析で系統的に測定する。本年度は以下の研究成果が得られた。
1. 走査電子顕微鏡を用いて，CV3 reducedコンドライト隕石から，Al-Mg形成年代を測定可能な細粒CAIを8つ見繕った。
2. 二次イオン質量分析計の光学系の調整を見直すことで，Al-Mg形成年代測定時における二次イオンの透過効率を，これまで（Kawasaki et al., 2018, GCA）の約2倍に向上させた。これにより細粒CAI中の微小鉱物結晶の年代測定が可能となった。
3. 見繕った8つの細粒CAIのうち，5つの細粒CAIのAl-Mg形成年代の測定を完了した。測定は北海道大学のマルチコレクター型質量分析計（Cameca ims-1280HR）を用いて行った。それぞれの細粒CAIについて得られたAl-Mg鉱物アイソクロンの傾きから，初生26Al/27Al比が得られ，(5.19 ± 0.17) × 10^-5から (3.35 ± 0.21) × 10^-5の広がりを示すことがわかった。この初生26Al/27Al比の広がりは，44 ± 7万年の形成年代幅に相当する。本研究により得られた細粒CAIの初生26Al/27Al比の広がりは，初期太陽系円盤の高温のガスからのダストの高温凝縮プロセスが，太陽系形成最初期の少なくとも約40万年間続いていたことを示す。
日本学術振興会, 若手研究, 北海道大学, 研究代表者, 18K13609

初期太陽系円盤におけるダスト高温加熱期間の解明
科学研究費助成事業
2016年04月 - 2018年03月
川崎 教行
本研究は，隕石中の難揮発性包有物CAIの形成年代の精密測定から，初期太陽系円盤の高温環境における，CAIダスト凝縮プロセスの継続期間を明らかにした。三つの高温凝縮物CAIの形成年代に成功し，一つは太陽系誕生時（±5万年）に形成したものであったが，他二つは，その10±4万年後と17±4万年後に，それぞれ形成したものであった。高温凝縮物CAIの中で，太陽系誕生時と有意に異なる形成年代をもつものが初めて発見された。本研究により，初期太陽系円盤において，ダスト凝縮プロセスと溶融プロセスが，太陽系誕生から少なくとも約20万年間，同時に起き続けていたことが示唆された。
日本学術振興会, 若手研究(B), 研究代表者, 16K17837

隕石の多元素同位体分析から原始太陽の挙動を理解する
科学研究費助成事業
2015年04月 - 2018年03月
馬上 謙一, 岡崎 隆司, 川﨑 教行
本研究はNaを含む火成メリライトの成因を鉱物組成・化学組成から把握したうえで，二次イオン質量分析装置（SIMS）及び希ガス質量分析装置を用いた同位体分析を行った．
Allende隕石中の火成メリライトに対し，同位体分析を行った．Be-B系ではBe-10の過剰が見られ，先行研究の結果と比較するとこのCAIは典型的なBe-10を保持していたCAIであることが分かった．またAl-Mg年代は最古のCAIよりも9万年ほど若い年代を示した．希ガス同位体分析では，Ne-22の過剰が見つかり，このCAIは太陽起源の高エネルギー粒子の照射によってNa-22がCAI形成領域で生成されていたとこが明らかにできた．
日本学術振興会, 若手研究(B), 北海道大学, 連携研究者, 15K17791

太陽系の消滅核種Al-26の起源の解明
科学研究費助成事業
2014年04月 - 2016年03月
川﨑 教行
26Alは半減期約70万年で26Mgへと放射壊変する短寿命放射性核種である。初期太陽系において26Alが存在していた証拠が隕石中のCAIやコンドリュールなどから発見されたが，その起源はよくわかっていない。同じようなPb-Pb形成年代をもつCAIとコンドリュールが，それぞれ異なる初生26Al量をもつことを，前年度までの研究で明らかとなった。これにより，初期太陽系円盤内における26Al量の不均一分布が示された。本年度，形成時の26Al量が我々により測定済みであるコンドリュールの，TIMSを用いたPb-Pb年代測定が共同研究者らにより引続き行われた。得られたPb-Pb年代を用いて，コンドリュール前駆物質の26Al量を見積もると，初生26Al/27Al同位体比が比較的高い集団と低い集団とに大別された。コンドリュール形成領域内においても，26Al量が不均一であることがわかり，26Alの起源研究に一石を投じる結果となった。
本年度は並行して，SIMSによるCAIのAl-Mg年代測定を行った。初期太陽系星雲の最内縁部とされるCAI形成領域では，26Al量が均一であったことがこれまでに示されている。年代測定の結果，アエンデ隕石のType C CAIは，太陽系誕生から200万年後以上後に加熱により再溶融し，ヴィガラノ隕石産fluffy Type A CAIは，約20万年かけて凝縮・集積を経て形成，アエンデ隕石産Type B1 CAIは，太陽系誕生から約5万年後に加熱により再溶融していたことがそれぞれわかった。後者二つのCAIの酸素同位体組成を同じくSIMSにより分析した結果，太陽系誕生から，少なくとも，5から20万年の間，CAIダスト周囲のガスの酸素同位体組成が，太陽に近い組成と地球に近い組成との間で，何度も入れ替わり変化していたことが明らかとなった。
日本学術振興会, 特別研究員奨励費, 北海道大学, 研究代表者, 14J00594