Researcher basic information

• 博士(理学), 東京大学, Mar. 2011

• https://researchmap.jp/k-bajo?lang=en

• https://jglobal.jst.go.jp/detail?JGLOBAL_ID=201301093277942347
• https://orcid.org/0000-0002-9013-2730
• https://sites.google.com/eis.hokudai.ac.jp/kbajo/

• https://orcid.org/0000-0002-9013-2730

• 201301093277942347

• Secondary Ion Mass Spectrometry
• Isotope
• Planetary science
• Mass Spectrometry
• Noble gas

• Natural Science, Space and planetary sciences

• Bachelor's degree program, School of Science
• Master's degree program, Graduate School of Science
• Doctoral (PhD) degree program, Graduate School of Science

Research activity information

• Depth-dependent mass fractionation of solar wind noble gases in lunar ilmenites revealed by high-resolution depth profiling
  Yuta Otsuki; Ken-ichi Bajo; Tomoya Obase; Rainer Wieler; Hisayoshi Yurimoto
  EARTH AND PLANETARY SCIENCE LETTERS, 683, 01 Jun. 2026, [Peer-reviewed]
  English, Scientific journal, 40245945
• Network structure of solar wind implanted on small celestial body surface
  Sohei Wada; Ken-ichi Bajo; Hisayoshi Yurimoto
  METEORITICS & PLANETARY SCIENCE, 61, 6, 987, 996, 07 May 2026
  English, Scientific journal
• History of individual presolar SiC grains revealed by stellar winds
  Ken-ichi Bajo; Tatsuki Izumi; Yuta Otsuki; Sachiko Amari; Hisayoshi Yurimoto
  Nature Communications, 16, 1, Springer Science and Business Media LLC, 14 Oct. 2025, [Lead author]
  Scientific journal
• 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; Jerome Aleon; 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; Frederic Moynier; Kazuhide Nagashima; Izumi Nakai; Ann Nguyen; Larry Nittler; Andreas Pack; Changkun Park; Laurette Piani; Liping Qin; Sara Russell; Naoya Sakamoto; Maria Schonbachler; 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, 646, 8083, 02 Oct. 2025
  English, Scientific journal
• 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, 18, 9, 832, 839, Springer Science and Business Media LLC, 22 Aug. 2025
  Scientific journal
• 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. Bekaer; E. Bloch; G. A. Brennecka; H. Busemann; J. S. Cowpe; S. A. Crowther; M. Ek; L. J. Fawce; 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. Rüfenach; 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 Jr; D. S. Lauretta
  Nature Astronomy, Jul. 2025, [Peer-reviewed]
• Evidence of solar wind irradiation on mineral grains embedded in matrix of the Northwest Africa 801 CR chondrite
  Sohei Wada; Ken-ichi Bajo; Tomoya Obase; Hisayoshi Yurimoto
  Meteoritics & Planetary Science, Wiley, 31 Mar. 2025, [Peer-reviewed]
  English, Scientific journal, Abstract
  
  Solar wind (SW) is preserved in meteorites as abundant solar noble gases. We performed in situ ⁴He isotope imaging of mineral grains in the CR2 chondrite matrix of Northwest Africa 801 using time‐of‐flight secondary neutral mass spectrometry with strong‐field post ionization. ⁴He⁺ signals were detected along the surfaces of individual grains of Fe‐Ni metal, ferrihydrite, olivine, pyroxene, and troilite. The high ⁴He concentrations along the surfaces indicate implantation of SW into the mineral grains. We determined the SW‐⁴He fluence of eight mineral grains from the line profiles across the grain boundaries. SW‐⁴He fluence ranged from 2.7 × 10¹⁶ to 58 × 10¹⁶ atoms cm⁻². These fluences were then used to calculate the SW irradiation durations. Assuming irradiation occurred at 4 astronomical units, the durations ranged from 3.8 to 82 kyr. These durations correspond to the residence time of individual mineral grains on the surface of the parent body. The variation in residence time for the mineral grains suggests variable durations for local mixing and burial processes on the parent body. The SW exposure ages provide insights into the gardening rate driven by small‐scale impact mixing processes on the parent body.
• Extreme Solar Particle Ejection Event in the Last Few Million Years from Asteroid Itokawa Sample
  Tomoya Obase; Ken-ichi Bajo; Yuta Otsuki; Hisayoshi Yurimoto
  The Astrophysical Journal, 978, 2, 142, 142, American Astronomical Society, 07 Jan. 2025, [Peer-reviewed]
  Scientific journal, Abstract
  
  Unusual explosive activity occasionally occurs from the Sun, releasing large amounts of solar energetic particles. Extreme solar particle ejection events in the past 11,000 yr have been detected by sharp increases of cosmogenic isotopes in annual tree rings and ice cores. However, quantitative estimation of the event magnitudes is not straightforward, as the cosmogenic isotopes are indirect records of solar particles. Similar solar particle ejection events may also accumulate records in surface materials of airless bodies such as the Moon and asteroids. Samples from the asteroid 25143 Itokawa have been irradiated by solar winds for tens to hundreds of years at some points in the last few million years. Here, we report implantation profiles of solar particle He from an Itokawa regolith grain that trace an extreme solar particle ejection event. The implantation profiles indicate that the fluences of suprathermal solar particles were 250–1300 times larger than that expected from the current normal solar activity. Since the degrees of excesses are inversely related to the solar wind irradiation periods, the high-energy particle fluence would have been derived from a single event. The event was approximately 40 times larger than the 2003 Halloween solar storms, which is one of the largest solar particle ejection events observed since the space-based measurement of solar activity began. The event magnitude is similar to the largest events inferred from the cosmogenic isotope records in terrestrial samples. Our result provides direct evidence of an extreme solar particle ejection event in the last few million years.
• Zirconium isotope composition indicates s-process depletion in samples returned from asteroid Ryugu
  Maria Schonbachler; Manuela A. Fehr; Tetsuya Yokoyama; Ikshu Gautam; Nao Nakanishi; Yoshinari Abe; Jerome Aleon; 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; Frederic 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, 60, 1, 3, 16, Jan. 2025
  English, Scientific journal
• Depth profiling of noble gases in ilmenite and olivine substrates
  Yuta Otsuki; Ken-ichi Bajo; Tomoya Obase; Hisayoshi Yurimoto
  Journal of Analytical Atomic Spectrometry, 40, 6, 1505, 1517, Royal Society of Chemistry (RSC), 2025, [Peer-reviewed]
  Scientific journal, High-resolution TOF-SNMS depth profiling of noble gas isotopes in natural samples.
• 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), 27 Sep. 2024
  Scientific journal, 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.
• 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; Jerome Aleon; 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; Frederic Moynier; Izumi Nakai; Kazuhide Nagashima; Ann Nguyen; Larry Nittler; Morihiko Onose; Andreas Pack; Changkun Park; Laurette Piani; Liping Qin; Sara Russell; Naoya Sakamoto; Maria Schonbachler; 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, 59, 8, 1966, 1982, Aug. 2024
  English, Scientific journal
• 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; Jerome Aleon; 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; Frederic Moynier; Izumi Nakai; Ann Nguyen; Larry Nittler; Morihiko Onose; Andreas Pack; Changkun Park; Laurette Piani; Liping Qin; Sara S. Russell; Maria Schonbachler; 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, 59, 8, 2097, 2116, Aug. 2024
  English, Scientific journal
• 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, Aug. 2024
  Scientific journal
• Nanoscale analysis of noble gas in solids
  Ken-ichi Bajo; Hisayoshi Yurimoto
  Journal of Analytical Science and Technology, 15, 1, Springer Science and Business Media LLC, 02 Apr. 2024, [Peer-reviewed]
  Scientific journal, Abstract
  
  Noble gases are useful tracers for geochemistry, used to elucidate the origin and evolution of the solar system and planets. Noble gas analyses have been limited to bulk and spot analyses of solids and have yet to be developed for two- and three-dimensional imaging analysis. Recent developments in He isotope imaging using secondary neutral mass spectrometry are reviewed. The images have been fully quantified, and the spatial resolution has reached the nanoscale. The detection limit has been reduced to the level of ~ 10^–3 cm³ STP g⁻¹ (~ 10¹⁷ cm⁻³, ~ 1 ppma) for helium at lateral micrometer resolution. With this development, the concentration distribution of He in solids has been visualized as a map for the first time.
• 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), 21 Mar. 2024, [Peer-reviewed], [Lead author, Corresponding author]
  Scientific journal
• Curation protocol of Phobos sample returned by Martian Moons eXploration
  Ryota Fukai; Tomohiro Usui; Wataru Fujiya; Yoshinori Takano; Ken-ichi Bajo; Andrew Beck; Enrica Bonato; Nancy L. Chabot; Yoshihiro Furukawa; Hidenori Genda; Yuki Hibiya; Fred Jourdan; Thorsten Kleine; Mizuho Koike; Moe Matsuoka; Yayoi N. Miura; Frederic Moynier; Ryuji Okazaki; Sara S. Russell; Hirochika Sumino; Michael E. Zolensky; Haruna Sugahara; Shogo Tachibana; Kanako Sakamoto; Masanao Abe; Yuichiro Cho; Kiyoshi Kuramoto
  METEORITICS & PLANETARY SCIENCE, 59, 2, 321, 337, Feb. 2024
  English, Scientific journal
• 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, Feb. 2024
  Scientific journal
• 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, Wiley, 26 Jan. 2024
  Scientific journal, Abstract
  
  In order to gain insights on the conditions of aqueous alteration on asteroid Ryugu and the origin of water in the outer solar system, we developed the measurement of water content in magnetite at the micrometer scale by secondary ion mass spectrometry (NanoSIMS) and determined the H and Si content of coarse‐grained euhedral magnetite grains (polyhedral magnetite) and coarse‐grained fibrous (spherulitic) magnetite from the Ryugu polished section A0058‐C1001. The hydrogen content in magnetite ranges between ~900 and ~3300 wt ppm equivalent water and is correlated with the Si content. Polyhedral magnetite has low and homogenous silicon and water content, whereas fibrous magnetite shows correlated Si and water excesses. These excesses can be explained by the presence of hydrous Si‐rich amorphous nanoinclusions trapped during the precipitation of fibrous magnetite away from equilibrium and testify that fibrous magnetite formed from a hydrous gel with possibly more than 20 wt% water. An attempt to determine the water content in sub‐μm framboids indicates that additional calibration and contamination issues must be addressed before a safe conclusion can be drawn, but hints at elevated water content as well. The high water content in fibrous magnetite, expected to be among the first minerals to crystallize at low water–rock ratio, points to the control of water content by local conditions of magnetite precipitation rather than large‐scale alteration conditions. Systematic lithological variations associated with water‐rich and water‐poor magnetite suggest that the global context of alteration may be better understood if local water concentrations are compared with millimeter‐scale distribution of the various morphologies of magnetite. Finally, the high water content in the magnetite precursor gel indicates that the initial O isotopic composition in alteration water must not have been very different from that of the earliest magnetite crystals.
• 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), 28 Dec. 2023
  Scientific journal
• 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, 24 Nov. 2023
  Scientific journal, 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.
• 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), 10 Nov. 2023
  Scientific journal, 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, 01 Aug. 2023
  Scientific journal, 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), 14 Jul. 2023
  Scientific journal, 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, 10 Jul. 2023
  Scientific journal
• 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, 01 Apr. 2023, [Peer-reviewed]
  Scientific journal, 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.
• 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. Ireland; Akira Ishikawa; Motoo Ito; 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; Laurette Piani; Liping Qin; Maria Schönbächler; Lauren Tafla; Haolan Tang; Kentaro Terada; Yasuko Terada; Tomohiro Usui; 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
  Science Advances, 8, 50, American Association for the Advancement of Science (AAAS), 16 Dec. 2022
  Scientific journal, 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, 12 Dec. 2022
  Scientific journal
• Development of electrostatic‐induced charge detector for multiturn time‐of‐flight mass spectrometer
  Ken‐ichi Bajo; Jun Aoki; Morio Ishihara; Shizuho Furuya; Masahiro Nishimura; Miwa Yoshitake; Hisayoshi Yurimoto
  Journal of Mass Spectrometry, 57, 11, 222, 24 Oct. 2022, [Peer-reviewed], [Lead author, Corresponding author]
  English
• Ryugu’s nucleosynthetic heritage from the outskirts of the Solar System
  Timo Hop; 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 Chaussido; Byeon-Gak Choi; Andrew M. Davis; Tommaso Di Rocco; Wataru Fujiya; Ryota Fukai; Ikshu Gautam; Makiko K. Hab; Yuki Hibiya; Hiroshi Hidaka; Hisashi Homma; Peter Hoppe; Gary R. Huss; Kiyohiro Ichida; Tsuyoshi Iizuka; Trevor R. Irelan; Akira Ishikawa; Motoo Ito; Shoichi Itoh; Noriyuki Kawasaki; Noriko T. Kit; Kouki Kitajim; Thorsten Kleine; Shintaro Komatani; Alexander N. Kro; Ming-Chang Liu; Yuki Masuda; Kevin D. McKeega; Mayu Morita; Kazuko Motomur; Frédéric Moynie; Izumi Nakai; Kazuhide Nagashim; David Nesvor; Ann Nguye; Larry Nittler; Morihiko Onose; Andreas Pack; Changkun Park; Laurette Piani; Liping Qi; Sara S. Russell; Naoya Sakamoto; Maria Schönbächler; Lauren Tafla; Haolan Tang; Kentaro Terada; Yasuko Terada; Tomohiro Usui; Sohei Wada; Meenakshi Wadhw; Richard J. Walke; Katsuyuki Yamashit; Qing-Zhu Yi; 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, American Association for the Advancement of Science (AAAS), 22 Oct. 2022
  Scientific journal, 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.
• First asteroid gas sample delivered by the Hayabusa2 mission: A treasure box from Ryugu
  Ryuji Okazaki; Yayoi N. Miura; Yoshinori Takano; Hirotaka Sawada; Kanako Sakamoto; Toru Yada; Keita Yamada; Shinsuke Kawagucci; Yohei Matsui; Ko Hashizume; Akizumi Ishida; Michael W. Broadley; Bernard Marty; David Byrne; Evelyn Füri; Alex Meshik; Olga Pravdivtsev; Henner Buseman; My E.I. Riebe; Jamie Gilmour; Jisun Park; Ken-ichi Bajo; Kevin Righter; Saburo Sakai; Shun Sekimoto; Fumio Kitajima; Sarah A. Crowthe; Naoyoshi Iwata; Naoki Shirai; Mitsuru Ebihara; Reika Yokochi; Kunihiko Nishiizumi; Keisuke Nagao; Jong Ik Le; Patricia Clay; Akihiro Kano; Marc W. Caffe; Ryu Uemura; Makoto Inagaki; Daniela Krietsch; Colin Maden; Mizuki Yamamoto; Lydia Fawcet; Thomas Lawto; Tomoki Nakamura; Hiroshi Naraoka; Takaaki Noguchi; Hikaru Yabuta; Hisayoshi Yurimoto; Yuichi Tsuda; Sei-ichiro Watanabe; Masanao Abe; Masahiko Arakawa; Atsushi Fujii; Masahiko Hayakawa; Naoyuki Hirat; 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 Matsumot; Moe Matsuoka; Tatsuhiro Michikami; Yuya Mimasu; Akira Miura; Tomokatsu Morota; Satoru Nakazawa; Noriyuki Namiki; Hirotomo Nod; Rina Noguchi; Naoko Ogawa; Kazunori Ogawa; Tatsuaki Okada; Chisato Okamoto; Go Ono; Masanobu Ozaki; Takanao Saiki; Naoya Sakatani; 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; Shizuho Furuya; Kentaro Hatakeda; Tasuku Hayashi; Yuya Hitomi; Kazuya Kumagai; Akiko Miyazaki; Aiko Nakato; Masahiro Nishimura; Hiromichi Soejima; Ayako Iwamae; Daiki Yamamoto; Kasumi Yogata; Miwa Yoshitake; Ryota Fukai; Tomohiro Usui; Trevor Irelan; Harold C. Connolly J; Dante S. Lauretta; Shogo Tachiba
  Science Advances, 8, 46, American Association for the Advancement of Science (AAAS), 20 Oct. 2022, [Peer-reviewed]
  Scientific journal, The Hayabusa2 spacecraft returned to Earth from the asteroid 162173 Ryugu on 6 December 2020. One day after the recovery, the gas species retained in the sample container were extracted and measured on-site and stored in gas collection bottles. The container gas consists of helium and neon with an extraterrestrial ³ He/ ⁴ He and ²⁰ Ne/ ²² Ne ratios, along with some contaminant terrestrial atmospheric gases. A mixture of solar and Earth’s atmospheric gas is the best explanation for the container gas composition. Fragmentation of Ryugu grains within the sample container is discussed on the basis of the estimated amount of indigenous He and the size distribution of the recovered Ryugu grains. This is the first successful return of gas species from a near-Earth asteroid.
• Noble gases and nitrogen in samples of asteroid Ryugu record its volatile sources and recent surface evolution
  Ryuji Okazaki; Bernard Marty; Henner Busemann; Ko Hashizume; Jamie D. Gilmour; Alex Meshik; Toru Yada; Fumio Kitajima; Michael W. Broadley; David Byrne; Evelyn Füri; My E. I. Riebe; Daniela Krietsch; Colin Maden; Akizumi Ishida; Patricia Clay; Sarah A. Crowther; Lydia Fawcett; Thomas Lawton; Olga Pravdivtseva; Yayoi N. Miura; Jisun Park; Ken-ichi Bajo; Yoshinori Takano; Keita Yamada; Shinsuke Kawagucci; Yohei Matsui; Mizuki Yamamoto; Kevin Righter; Saburo Sakai; Naoyoshi Iwata; Naoki Shirai; Shun Sekimoto; Makoto Inagaki; Mitsuru Ebihara; Reika Yokochi; Kunihiko Nishiizumi; Keisuke Nagao; Jong Ik Lee; Akihiro Kano; Marc W. Caffee; Ryu Uemura; Tomoki Nakamura; Hiroshi Naraoka; Takaaki Noguchi; Hikaru Yabuta; Hisayoshi Yurimoto; Shogo Tachibana; Hirotaka Sawada; Kanako Sakamoto; 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; 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; Shizuho Furuya; Kentaro Hatakeda; Tasuku Hayashi; Yuya Hitomi; Kazuya Kumagai; Akiko Miyazaki; Aiko Nakato; Masahiro Nishimura; Hiromichi Soejima; Ayako Iwamae; Daiki Yamamoto; Kasumi Yogata; Miwa Yoshitake; Ryota Fukai; Tomohiro Usui; Harold C. Connolly; Dante Lauretta; Sei-ichiro Watanabe; Yuichi Tsuda
  Science, 379, 6634, eabo0431, American Association for the Advancement of Science (AAAS), 20 Oct. 2022, [International Magazine]
  English, Scientific journal, The near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth’s volatiles. Samples of Ryugu were retrieved by the Hayabusa2 spacecraft. We measure noble gas and nitrogen isotopes in Ryugu samples, finding they are dominated by pre-solar and primordial components, incorporated during Solar System formation. Noble gas concentrations are higher than those in Ivuna-type carbonaceous (CI) chondrite meteorites. Several host phases of isotopically distinct nitrogen have heterogeneous abundances between the samples. Our measurements support a close relationship between Ryugu and CI chondrites. Noble gases produced by galactic cosmic rays, indicating ~5 Myr exposure, and from implanted solar wind, record the recent irradiation history of Ryugu after it migrated to its current orbit.
• 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. 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, Oct. 2022
  Scientific journal
• 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, Aug. 2022
  English, Scientific journal
• 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, American Association for the Advancement of Science (AAAS), 09 Jun. 2022
  Scientific journal, 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.
• The initial description and initial analysis for the return samples from Phobos by sample analysis working team in Martian Moon eXploration project
  Fukai Ryota; Usui Tomohiro; Fujiya Wataru; Takano Yoshinori; Bajo Ken―ichi; Koike Mizuho; Miura Yayoi; Beck Andrew; Bonato Enrica; L. Chabot Nancy; Moynier Frederic; S. Russell Sara; Genda Hidenori; Furukawa Yoshihiro; Matsuoka Moe; Sugahara Haruna; Tachibana Shogo; E. Zolensky Michael; Sakamoto Kanako; Abe Masanao
  Abstracts of Annual Meeting of the Geochemical Society of Japan, 69, 216, GEOCHEMICAL SOCIETY OF JAPAN, 2022
  Japanese, 火星衛星探査計画Martian Moons eXploration (MMX)は、火星衛星の一つであるフォボスからのサンプルリターンミッションである。Sample Analysis Working Team (SAWT)は、2029年に帰還するリターンサンプルの分析プロトコルの設計や、科学的要求の整理を行なっている。本発表において、MMXの科学目的である火星衛星の起源の解明等に向けて必要な分析方法と、分析チームへの分配のために必要な記載方法の検討状況を紹介する。
• Development of in-situ Depth Profiling for Extraterrestrial Materials with Isotope Nanoscope
  大槻悠太; 馬上謙一; 圦本尚義
  Journal of the Mass Spectrometry Society of Japan, 69, 6, 197, 201, The Mass Spectrometry Society of Japan, 2021, [Peer-reviewed]
  Japanese, Scientific journal, Lunar and asteroidal regolith contains noble gases derived from solar wind implantation. These particles preserve ancient solar wind, which can be revealed an energy distribution of the solar wind at the period of implantation. The energy distribution of ancient solar wind can be evaluated by depth profiling of noble gases into an extraterrestrial sample. Because typical solar wind ions are implanted at less than 50 nm from the sample surface, the particle surface for analysis must be kept in its original shape. In this study, particle samples were embedded in indium metal to adjust angle and position of the sample surfaces. We measured depth profiles for ¹⁶O⁺, ⁵⁶Fe²⁺, ⁴⁸Ti²⁺ and ²⁴Mg⁺ of ilmenite particles and a polished ilmenite. We obtained depth profiles of constant ion intensities from the ilmenite particles as well as the polished ilmenite. Reproducibilities for ion intensities normalized to ¹⁶O⁺ were up to 33% for particle samples and 19% for polished one.
• Visualization of DNA replication in single chromosome by stable isotope labeling
  Kosuke Nagata; Ken-ichi Bajo; Hideyuki Mitomo; Ryosuke Fujita; Ryota Uehara; Kuniharu Ijiro; Hisayoshi Yurimoto
  Cell Structure and Function, 46, 2, 95, 101, Japan Society for Cell Biology, 2021, [Peer-reviewed], [Domestic magazines]
  English, Scientific journal, Among the inheritance of cellular components during cell division, deoxyribonucleic acid (DNA) and its condensate (chromosome) are conventionally visualized using chemical tag-labeled nucleotide analogs. However, associated mutagenesis with nucleotide analogs in the visualization of chromosomes is cause for concern. This study investigated the efficiency of using stable isotope labels in visualizing the replicating cultured human cell-chromosomes, in the absence of analog labels, at a high spatial resolution of 100 nm. The distinct carbon isotope ratio between sister chromatids reflected the semi-conservative replication of individual DNA strands through cell cycles and suggested the renewal of histone molecules in daughter chromosomes. Thus, this study provides a new, powerful approach to trace and visualize cellular components with stable isotope labeling.Key words: stable isotope, chromosome replication, semi-conservative replication, imaging, mass spectrometry.
• Analytical Protocols for Phobos Regolith Samples Returned by the Martian Moons Exploration (MMX) Mission
  Wataru Fujiya; Yoshihiro Furukawa; Haruna Sugahara; Mizuho Koike; Ken-ichi Bajo; Nancy L. Chabot; Yayoi N. Miura; Frederic Moynier; Sara S. Russell; Shogo Tachibana; Yoshinori Takano; Tomohiro Usui; Michael E. Zolensky
  Research Square Platform LLC, 11 Dec. 2020, [Peer-reviewed]
  Abstract
  
  Japan Aerospace Exploration Agency (JAXA) will launch a spacecraft in 2024 for a sample return mission from Phobos (Martian Moons eXploration: MMX). Touchdown operations are planned to be performed twice at different landing sites on the Phobos surface to collect >10 g of the Phobos surface materials with coring and pneumatic sampling systems on board. The Sample Analysis Working Team (SAWT) of MMX is now designing analytical protocols of the returned Phobos samples to shed light on the origin of the Martian moons as well as the evolution of the Mars-moon system. Observations of petrology and mineralogy, and measurements of bulk chemical compositions and stable isotopic ratios of, e.g., O, Cr, and Ti can provide crucial information about the origin of Phobos. If Phobos is a captured asteroid composed of primitive chondritic materials, as inferred from its reflectance spectra, the nature of organic matter as well as bulk H, N, and Zn isotopic compositions characterize the volatile materials in the samples and constrain the type of the captured asteroid. Cosmogenic and solar wind components, most pronounced in noble gas isotopic compositions, can reveal surface processes on Phobos. Long- and short-lived radionuclide chronometry such as ⁵³Mn-⁵³Cr and ⁸⁷Rb-⁸⁷Sr systematics can date pivotal events like impacts, thermal metamorphism, and aqueous alteration on Phobos. It should be noted that the Phobos regolith is expected to contain a small amount of materials delivered from Mars, which may be physically and chemically different from any Martian meteorites in our collection and thus are particularly precious. The analysis plan will be designed to detect such Martian materials, if any, from the returned samples dominated by the Phobos building blocks in curation procedures at JAXA before they are processed for further analyses.
• The Importance of Phobos Sample Return for Understanding the Mars-Moon System
  Tomohiro Usui; Ken-ichi Bajo; Wataru Fujiya; Yoshihiro Furukawa; Mizuho Koike; Yayoi N. Miura; Haruna Sugahara; Shogo Tachibana; Yoshinori Takano; Kiyoshi Kuramoto
  SPACE SCIENCE REVIEWS, 216, 4, Apr. 2020, [Peer-reviewed]
  English
• Aberration-corrected focused ion beam for time-of-flight secondary neutral mass spectrometry
  Kosuke Nagata; Ken-ichi Bajo; Satoru Itose; Miyuki Matsuya; Morio Ishihara; Kiichiro Uchino; Hisayoshi Yurimoto
  Applied Physics Express, 12, 8, 2019, [Peer-reviewed]
  English, Scientific journal
• Electronic data acquisition and operational control system for time-of-flight sputtered neutral mass spectrometer
  Ken-ichi Bajo; Osamu Fujioka; Satoru Itose; Morio Ishihara; Kiichiro Uchino; Hisayoshi Yurimoto
  Surface and Interface Analysis, 51, 1, 35, 39, Jan. 2019, [Peer-reviewed]
  English, Scientific journal
• Epoch-making meteorites(12)Monahans (1998) and Zag : Primordial water from fluid inclusion bearing halite in the two chondrites
  Bajo K.
  Planetary People - The Japanese Society for Planetary Sciences, 27, 1, 40, 42, The Japanese Society for Planetary Sciences, Mar. 2018, [Peer-reviewed]
  Japanese, Monahans（ 1998）とZagは1998年に地球に落下した普通コンドライトである．これらの隕石には岩塩であるハライト（Halite : NaCl）が含まれており，そのハライト中には水を主成分とする流体包有物が存在していた．そのため，小惑星帯に存在する天体の水の起源を考える上で非常に興味深い試料として，様々な研究がなされてきた．これらの二つの隕石の岩石的な特徴と年代学的な研究，及び，ハライトの成因について紹介する．
• High spatial resolution imaging of helium isotope by TOF-SNMS
  Ken-ichi Bajo; Satoru Itose; Miyuki Matsuya; Morio Ishihara; Kiichiro Uchino; Masato Kudo; Isao Sakaguchi; Hisayoshi Yurimoto
  SURFACE AND INTERFACE ANALYSIS, 48, 11, 1190, 1193, Nov. 2016, [Peer-reviewed]
  English, Scientific journal
• Quantitative analysis of helium by post-ionization method using femtosecond laser technique
  Hisayoshi Yurimoto; Ken-ichi Bajo; Isao Sakaguchi; Taku T. Suzuki; Amy J. G. Jurewicz; Satoru Itose; Kiichiro Uchino; Morio Ishihara
  SURFACE AND INTERFACE ANALYSIS, 48, 11, 1181, 1184, Nov. 2016, [Peer-reviewed]
  English, Scientific journal
• Evaluation of multi-turn time-of-flight mass spectrum of laser ionization mass nanoscope
  Azusa Tonotani; Ken-ichi Bajo; Satoru Itose; Morio Ishihara; Kiichiro Uchino; Hisayoshi Yurimoto
  SURFACE AND INTERFACE ANALYSIS, 48, 11, 1122, 1126, Nov. 2016, [Peer-reviewed]
  English, Scientific journal
• MICRODISTRIBUTION OF SOLAR WIND HELIUM ON ITOKAWA PARTICLE SURFACES
  Yurimoto H; Bajo K; Sakaguchi I; Suzuki T. T; Itose S; Matsuya M; Ishihara M; Uchino K
  METEORITICS & PLANETARY SCIENCE, 50, Aug. 2015, [Peer-reviewed]
• Depth profiling analysis of solar wind helium collected in diamond-like carbon film from Genesis
  Ken-ichi Bajo; Chad T. Olinger; Amy J. G. Jurewicz; Donald S. Burnett; Isao Sakaguchi; Taku Suzuki; Satoru Itose; Morio Ishihara; Kiichiro Uchino; Rainer Wieler; Hisayoshi Yurimoto
  GEOCHEMICAL JOURNAL, 49, 5, 559, 566, 2015, [Peer-reviewed]
  English, Scientific journal
• Development of laser ionization mass nanoscope (LIMAS)
  Shingo Ebata; Morio Ishihara; Kiichiro Uchino; Satoru Itose; Miyuki Matsuya; Masato Kudo; Ken-ichi Bajo; Hisayoshi Yurimoto
  SURFACE AND INTERFACE ANALYSIS, 44, 6, 635, 640, Jun. 2012, [Peer-reviewed]
  English, Scientific journal
• Irradiation history of Itokawa regolith material deduced from noble gases in the Hayabusa samples.
  Keisuke Nagao; Ryuji Okazaki; Tomoki Nakamura; Yayoi N Miura; Takahito Osawa; Ken-ichi Bajo; Shintaro Matsuda; Mitsuru Ebihara; Trevor R Ireland; Fumio Kitajima; Hiroshi Naraoka; Takaaki Noguchi; Akira Tsuchiyama; Hisayoshi Yurimoto; Michael E Zolensky; Masayuki Uesugi; Kei Shirai; Masanao Abe; Toru Yada; Yukihiro Ishibashi; Akio Fujimura; Toshifumi Mukai; Munetaka Ueno; Tatsuaki Okada; Makoto Yoshikawa; Junichiro Kawaguchi
  Science (New York, N.Y.), 333, 6046, 1128, 31, 26 Aug. 2011, [Peer-reviewed], [International Magazine]
  English, Scientific journal
• 81Kr-Kr age and multiple cosmic-ray exposure history of the Vaca Muerta mesosiderite
  Ken-ichi Bajo; Keisuke Nagao
  METEORITICS & PLANETARY SCIENCE, 46, 4, 556, 573, Apr. 2011, [Peer-reviewed]
  English, Scientific journal
• Single grain noble gas analysis of Antarctic micrometeorites by stepwise heating method with a newly constructed miniature furnace
  Ken-ichi Bajo; Tomohiro Akaida; Noriaki Ohashi; Takaaki Noguchi; Tomoki Nakamura; Yoshinobu Nakamura; Hirochika Sumino; Keisuke Nagao
  EARTH PLANETS AND SPACE, 63, 10, 1097, 1111, 2011, [Peer-reviewed]
  English, Scientific journal
• Noble gas isotopic compositions of zircons above the Bangombe natural fission reactor
  Makiko Kikuchi; Keisuke Nagao; Ken-ichi Bajo; Hiroshi Hidaka
  GEOCHIMICA ET COSMOCHIMICA ACTA, 74, 12, A514, A514, Jun. 2010, [Peer-reviewed]
  English
• Irradiation histories of iron meteorites
  M. Honda; H. Nagai; K. Nagao; K. Bajo; N. Takaoka; Y. Oura; K. Nishiizumi
  Journal of the Physical Society of Japan, 78, 12, 17, Physical Society of Japan, 2009, [Peer-reviewed]
  English, International conference proceedings

• Isotope Imaging Using SIMS
  Bajo Ken-ichi, Journal of the Mass Spectrometry Society of Japan, 73, 4, 186, 186, 01 Dec. 2025
  The Mass Spectrometry Society of Japan, Japanese
• High-spatial resolution in-situ helium analysis
  KENICHI BAJO; Sohei Wada; Hisayoshi Yurimoto, Abstracts of Annual Meeting of the Geochemical Society of Japan, 72, 204, 2025
  希ガス元素は，地球化学分野において主にトレーサー元素として利用されている。これらは固体物質中に極めて微量しか含まれておらず，一次的には枯渇している。一方で，ウランやトリウムの放射壊変によるヘリウム生成や，カリウム-40の崩壊に伴うアルゴン生成などの二次的な起源により，固体物質中の希ガス元素比や同位体比は著しく変動する。このような変動は，物質の形成履歴や熱的イベントの復元に利用されている。本研究では，太陽系小天体の表層環境を物質科学的に解明することを目的として，太陽風起源ヘリウムに着目した。そこで，ヘリウムの局所分析手法(ヘリウムイメージング法)を新たに開発し，太陽風起源ヘリウムの局在を可視化することに成功した．さらに，局所的なヘリウム濃度の定量化を通じて，レゴリス粒子の表層露出期間(滞在期間)を推定することが可能となった。開発と隕石試料への応用の経緯に加え，当手法の空間分解能・感度の特性評価について紹介する。, GEOCHEMICAL SOCIETY OF JAPAN, Japanese
• Development of Simultaneous in-situ Micro-analysis for He, Ne, and Ar Isotopes in Minerals by Isotope Nanoscope
  大槻悠太; 馬上謙一; 小長谷智哉; WIELER Rainer; 圦本尚義, 質量分析総合討論会講演要旨集, 72nd, 2024
• Helium isotope imaging for CM chondrites
  小長谷智哉; 馬上謙一; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2024, 2024
• In-situ analysis of helium, neon, and argon isotopes in ilmenite and olivine
  大槻悠太; 馬上謙一; 小長谷智哉; WIELER Rainer; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2024, 2024
• Helium-rich clast in the MIL 090657 CR chondrite: Evidence for exposure to solar energetic particles from the pre-main-sequence Sun
  小長谷智哉; 馬上謙一; 松本恵; 和田壮平; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2024, 2024
• In-situ Noble Gas Analysis Using Isotope Nanoscope
  Bajo Ken-ichi, Journal of the Mass Spectrometry Society of Japan, 71, 2, 91, 92, 01 Jun. 2023
  The Mass Spectrometry Society of Japan, Japanese
• Imaging of solar wind helium in the Fe-Ni metal and metal hydroxide from Northwest Africa 801
  和田壮平; 馬上謙一; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2023, 2023
• ⁴He and ²⁰Ne from Coronal Mass Ejection Recorded in Ilmenite Grain from Lunar Soil 71501
  大槻悠太; 馬上謙一; WIELER Rainer; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2023, 2023
• Three-dimensional distributions of solar wind helium on the surfaces of Itokawa regolith particles
  小長谷智哉; 馬上謙一; 大槻悠太; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2023, 2023
• VISUALIZATION OF SEDIMENTARY STRUCTURE IN CHONDRITE BY 2-D HELIUM IMAGING.
  Sohei Wada; Ken-ichi Bajo; Hisayoshi Yurimoto, METEORITICS & PLANETARY SCIENCE, 57, Aug. 2022
  English, Summary international conference
• 安定同位体を標識とした染色体の高空間分解能質量イメージング
  永田康祐; 永田康祐; 馬上謙一; 三友秀之; 藤田龍介; 上原亮太; 上原亮太; 居城邦治; 圦本尚義, 日本生化学会大会(Web), 95th, 2022
• Depth distributions of solar wind noble gases in lunar ilmenite
  大槻悠太; 馬上謙一; WIELER Rainer; 圦本尚義, 日本地球化学会年会要旨集(Web), 69th, 179, 2022
  月レゴリスは過去の地球・月系における太陽風照射を記録している。本研究では月イルメナイト粒子の希ガス深さ方向分析を行い、過去のコロナ質量放出(CME)に伴う高エネルギー粒子の検出を試みた。その結果、分析を行った2つのイルメナイト試料の希ガス同位体分布は共通して10–30 nmの深さに濃度のピークを持ち、深部にかけて減衰する、イオン注入による分布を示した。10–30 nmのピークは現在の太陽風粒子の平均エネルギーでのイオン注入に対応する。また、ピーク以深の希ガス濃度の減衰の程度が試料によって異なっていた。深部に分布する成分は過去の高エネルギーなイオン注入に対応している。このため、試料ごとの深さ方向分布の減衰の程度の違いは個々の粒子が太陽風の照射を受けていた期間に太陽が起こしたCMEの規模や回数の違いを反映していると考えられる。, GEOCHEMICAL SOCIETY OF JAPAN, Japanese
• Helium depth profiling for presolar silicon carbide
  和泉樹; 馬上謙一; 川崎教行; 大槻悠太; 甘利幸子; 圦本尚義, 日本地球化学会年会要旨集(Web), 69th, 2022
• Solar wind helium distribution in Northwest Africa 801 meteorite by a large-area imaging of helium isotope
  和田壮平; 馬上謙一; 圦本尚義, 日本地球化学会年会要旨集(Web), 69th, 178, 2022
  同位体ナノスコープによる広領域イメージング法を用いて，太陽風起源希ガスに富むNorthwest Africa 801(NWA 801)CRコンドライト中のヘリウム分布を調査した。NWA 801隕石は，数百µmから数mmのコンドリュールと，その間隙を埋めるマトリクスから構成される。本研究において，ヘリウムはコンドリュールからは検出されなかったが，マトリクスには含まれていた。マトリクス中のヘリウムは均質に存在しておらず，ヘリウムに乏しい領域と富む領域に分かれていた。ヘリウムに乏しい領域は数十µmから数百µmの塊状(礫状)で，ヘリウムに富む領域は，その塊の間を埋めるように分布していた。ヘリウムに乏しい塊の間を埋めるようにヘリウムに富む領域が分布している構造は，太陽風に曝されていない礫の隙間に母天体表面で太陽風に曝された砂が入り込んだ，この隕石母天体でのレゴリスの堆積過程を反映している。, GEOCHEMICAL SOCIETY OF JAPAN, Japanese
• Host mineral phases of solar wind helium and their occurrence in Northwest Africa 801 meteorite
  和田壮平; 馬上謙一; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2022, 2022
• Depth profiling of solar wind noble gases in lunar soils by isotope nanoscope
  大槻悠太; 馬上謙一; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2022, 2022
• Development of in-situ Analysis for Extraterrestrial Particles with Isotope Nanoscope
  大槻悠太; 馬上謙一; 圦本尚義, 質量分析総合討論会講演要旨集, 69th, 2021
• Development of large-area imaging of helium isotope by SNMS using post ionization by a femto-second laser
  和田壮平; 馬上謙一; 圦本尚義, 日本地球化学会年会要旨集(Web), 68th, 143, 2021
  LIMAS(Laser Ionization Mass Nanoscope)は、微小領域の希ガス分析が可能な、フェムト秒レーザーを用いた二次中性粒子質量分析計(SNMS)の一種である。本研究では、コンドリュール中の太陽起源高エネルギー粒子を検出するため、LIMASを改造しヘリウム広領域イメージング法を開発した。ポストイオン化領域を広げるため、一次イオンの画像走査に同期してレーザービームの中心線が移動するソフトウェアを開発し、広領域イメージングシステムを構築した。基礎実験として、15 keVの⁴He⁺イオンをシリコン基板に照射量1 × 10¹⁶ cm⁻²をイオン打ち込みした試料を用いて、広領域イメージングを行った。その結果、200 × 100 µm四方のヘリウムイメージングが可能になった。, GEOCHEMICAL SOCIETY OF JAPAN, Japanese
• Analytical Protocols for Phobos Regolith Samples Returned by the Martian Moons Exploration (MMX) Mission
  Wataru Fujiya; Yoshihiro Furukawa; Haruna Sugahara; Mizuho Koike; Ken-ichi Bajo; Nancy L. Chabot; Yayoi N. Miura; Frederic Moynier; Sara S. Russell; Shogo Tachibana; Yoshinori Takano; Tomohiro Usui; Michael E. Zolensky, Abstracts of Annual Meeting of the Geochemical Society of Japan, 67, 88, 11 Dec. 2020, [Peer-reviewed]
  
  Japan Aerospace Exploration Agency (JAXA) will launch a spacecraft in 2024 for a sample return mission from Phobos (Martian Moons eXploration: MMX). Touchdown operations are planned to be performed twice at different landing sites on the Phobos surface to collect >10 g of the Phobos surface materials with coring and pneumatic sampling systems on board. The Sample Analysis Working Team (SAWT) of MMX is now designing analytical protocols of the returned Phobos samples to shed light on the origin of the Martian moons as well as the evolution of the Mars-moon system. Observations of petrology and mineralogy, and measurements of bulk chemical compositions and stable isotopic ratios of, e.g., O, Cr, and Ti can provide crucial information about the origin of Phobos. If Phobos is a captured asteroid composed of primitive chondritic materials, as inferred from its reflectance spectra, the nature of organic matter as well as bulk H, N, and Zn isotopic compositions characterize the volatile materials in the samples and constrain the type of the captured asteroid. Cosmogenic and solar wind components, most pronounced in noble gas isotopic compositions, can reveal surface processes on Phobos. Long- and short-lived radionuclide chronometry such as ⁵³Mn-⁵³Cr and ⁸⁷Rb-⁸⁷Sr systematics can date pivotal events like impacts, thermal metamorphism, and aqueous alteration on Phobos. It should be noted that the Phobos regolith is expected to contain a small amount of materials delivered from Mars, which may be physically and chemically different from any Martian meteorites in our collection and thus are particularly precious. The analysis plan will be designed to detect such Martian materials, if any, from the returned samples dominated by the Phobos building blocks in curation procedures at JAXA before they are processed for further analyses., Research Square Platform LLC, English
• Study of the Solar Wind by Secondary Neutral Mass Spectroscopy Using Post Ionization by a Femto-Second Laser
  Hisayoshi Yurimoto; Ken-ichi Bajo, The review of laser engineering, 48, 8, 441, 446, Aug. 2020, [Peer-reviewed], [Last author]
  レーザー学会, Japanese
• 星雲ガス中で集積する岩石惑星の希ガス同位体比
  齊藤大晶; 馬上謙一; 山本順司; 倉本圭, 日本惑星科学会秋季講演会予稿集(Web), 2020, 2020
• Significance of Phobos Sample for Understanding the Mars-moon System
  Usui Tomohiro; Bajo Ken'ichi; L. Chabot Nancy.; Fujiya Wataru; Furukawa Yoshihiro; Koike Mizuho; Miura Yayohi; Moynier Frederic; S. Russell Sara; Sugahara Haruna; Tachibana Shogo; Takano Yoshinori; E. Zolensky Michael., Abstracts of Annual Meeting of the Geochemical Society of Japan, 67, 93, 2020
  本発表は、2020年代に行われる火星衛星からのサンプルリターン計画(MMX: Martian Moons eXploration)によってもたらされるフォボス試料の科学意義に関する発表を行う。, GEOCHEMICAL SOCIETY OF JAPAN, Japanese
• 安定同位体標識を用いた染色体中のDNA複製の可視化
  永田康祐; 馬上謙一; 三友秀之; 三友秀之; 藤田龍介; 上原亮太; 上原亮太; 居城邦治; 居城邦治; 圦本尚義, 日本分子生物学会年会プログラム・要旨集(Web), 43rd, 2020
• HELIUM FROM CORONAL MASS EJECTA COLLECTED BY NASA'S GENESIS
  H. Yurimoto; A. Tonotani; K. Bajo; C. T. Olinger; D. Reisenfeld; A. J. G. Jurewicz; S. Itose; I. Sakaguchi; M. Ishihara; K. Uchino; D. S. Burnet, METEORITICS & PLANETARY SCIENCE, 52, A401, A401, Aug. 2017
  English, Summary international conference
• Genesis‐DOS試料中に打ち込まれた太陽風起源希ガスのCME起源粒子検出
  殿谷梓; 馬上謙一; OLINGER Chad T; JUREWICZ Amy J G; 坂口勲; 鈴木拓; BURNETT Donald S; 糸瀬悟; 石原盛男; 内野喜一郎; 圦本尚義; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2017, ROMBUNNO.PPS10‐04 (WEB ONLY), 2017
  Japanese
• レーザーイオン化ナノ質量分析計(LIMAS)の多重周回飛行時間型質量分析計の評価
  殿谷梓; 馬上謙一; 糸瀬悟; 石原盛男; 内野喜一郎; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2016, ROMBUNNO.MTT28‐P03 (WEB ONLY), 2016
  Japanese
• 同位体ナノスコープを用いたジルコン中放射壊変起源ヘリウム分析法の開発
  吉成耕一; 馬上謙一; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2016, ROMBUNNO.SGL38‐P05 (WEB ONLY), 2016
  Japanese
• Mass Spectrometry Laboratory
  馬上 謙一, Journal of the Mass Spectrometry Society of Japan, 64, 5, 219, 221, 2016
  <p>北海道大学大学院理学研究院地球惑星科学部門地球惑星システム科学分野地球化学研究グループでは，太陽系の起源と進化の解明を目指しています．そのため，光学顕微鏡，電子顕微鏡，X線分光法，質量分析法などの手法を駆使して，地球内外の物質を正確に分析し，解析しています．この結果，全く新しい惑星や太陽系の起源や生い立ちが詳しくわかってきました．また，地球内外物質からこれまで読み取られていなかった全く新しい情報を獲得するため，物質を解析する新しい方法（分析法，解析装置，合成装置）の設計・開発も同時に行っています．また，これら一連の研究の中に，現在まで認知されていない自然法則や現象が潜んでいて，それを発見できれば一層楽しいと考えています．現在筆者が使用している質量分析装置は非常に小さな領域（<i>μ</i>mからnmスケール）の希ガス同位体を測定するためのスパッタ中性粒子質量分析装置（Sputtered Neutral Mass Spectrometer; SNMS）です．この装置の開発の経緯やどのような分析ができるのかを紹介させていただきます．</p>, The Mass Spectrometry Society of Japan, Japanese
• トンネルイオン化SNMS装置(LIMAS)の飛行時間型質量分析計の評価
  殿谷梓; 馬上謙一; 圦本尚義, 日本地球惑星科学連合大会予稿集(Web), 2015, ROMBUNNO.MTT44‐02 (WEB ONLY), 2015
  Japanese
• 同位体ナノスコープ
  YURIMOTO HISAYOSHI; BAJO KEN'ICHI; ISHIHARA MORIO; UCHINO KIICHIRO; ITOSE SATORU; MATSUYA MIYUKI; KUDO MASATO, 質量分析総合討論会講演要旨集, 61st, 16, 02 Sep. 2013
  Japanese
• TOF‐SNMSのタイミング制御に関する実験
  BAJO KEN-ICHI; YURIMOTO NAOYOSHI, 質量分析総合討論会講演要旨集, 61st, 134, 02 Sep. 2013
  Japanese
• Interaction between solar-wind-He and materials by using high spatial resolution TOF-SIMS
  Bajo Ken-ichi; Sakaguchi Isao; Suzuki Taku; Itose Satoru; Matsuya Miyuki; Kudo Masato; Ishihara Morio; Uchino Kichiro; Yurimoto Hisayoshi, Abstracts of Annual Meeting of the Geochemical Society of Japan, 60, 0, 8, 8, 2013
  Nagao et al. (2011) によるはやぶさ試料の希ガス同位体分析は太陽風照射とそれに伴う太陽風起源He/Ne間の分別を明らかにした．しかし，希ガス分析は粒子一粒ごとの結果でありSTEM観察との直接比較を行うには希ガス分析事前にSTEM観察を行うなど，分析方法の工夫が必要である．そこで，我々が開発したポストイオン化二次イオン質量分析装置LIMAS(Laser Ionization Mass Nanoscope)を用いることで，希ガス同位体分析を数十nmスケールの空間分解能で行うことが可能となり得る．本発表では新しい局所希ガス同位体分析手法をもとに，イトカワ表層での太陽風照射の履歴に関して期待される結果について述べる．, GEOCHEMICAL SOCIETY OF JAPAN, Japanese
• Construction of a Newly Designed Small-Size Mass Spectrometer for Helium Isotope Analysis : Toward the Continuous Monitoring of ³He/⁴He Ratios in Natural Fluids (Mass Spectrometry) -- (Special Issue : Professor Hisashi Matsuda Memorial Issue)
  Bajo Ken-ichi; Sumino Hirochika; Toyoda Michisato, Journal of the Mass Spectrometry Society of Japan = 質量分析, 60, 6, 1, 10, Dec. 2012
  日本質量分析学会, English
• Construction of a Newly Designed Small-Size Mass Spectrometer for Helium Isotope Analysis : Toward the Continuous Monitoring of ^3He/^4He Ratios in Natural Fluids
  BAJO Ken-ichi; SUMINO Hirochika; TOYODA Michisato; OKAZAKI Ryuji; OSAWA Takahito; ISHIHARA Morio; KATAKUSE Itsuo; NOTSU Kenji; IGARASHI George; NAGAO Keisuke, Mass Spectrometry, 1, 2, A0009, A0009, 01 Dec. 2012
  The construction of a small-size, magnetic sector, single focusing mass spectrometer (He-MS) for the continuous, on-site monitoring of He isotope ratios (³He/⁴He) is described. The instrument is capable of measuring ⁴He/²⁰Ne ratios dissolved in several different types of natural fluids of geochemical interest, such as groundwater and gas from hot springs, volcanoes and gas well fields. The ion optics of He-MS was designed using an ion trajectory simulation program “TRIO,” which permits the simultaneous measurement of ³He and ⁴He with a double collector system under a mass resolution power (<i>M</i>/Δ<i>M</i>) of >500. The presently attained specifications of the He-MS are; (1) a mass resolving power of ca. 490, sufficient to separate ³He⁺ from interfering ions, HD⁺ and H₃⁺, (2) ultra-high vacuum conditions down to 3&times;10⁻⁸ Pa, and (3) a sufficiently high sensitivity to permit amounts of ³He to be detected at levels as small as 10⁻¹³ cm³STP (3&times;10⁶ atoms). Long term stability for ³He/⁴He analysis was examined by measuring the ³He/⁴He standard gas (HESJ) and atmospheric He, resulting in ∼3% reproducibility and ≤5% experimental error for various amounts of atmospheric He from 0.3 to 2.3&times;10⁻⁶ cm³STP introduced into the instrument. A dynamic range of measurable ³He/⁴He ratios with He-MS is greater than 10³ which was determined by measuring various types of natural fluid samples from continental gas (with a low ³He/⁴He ratio down to 2&times;10⁻⁸) to volcanic gas (with a high ³He/⁴He ratio up to 3&times;10⁻⁵). The accuracy and precision of ³He/⁴He and ⁴He/²⁰Ne ratios were evaluated by comparing the values with those measured using well established noble gas mass spectrometers (modified VG5400/MS-III and -IV) in our laboratory, and were found to be in good agreement within analytical errors. Usefulness of the selective extraction of He from water/gas using a high permeability of He through a silica glass wall at high temperature (700&deg;C) is demonstrated., The Mass Spectrometry Society of Japan, English
• Noble gas analysis by Laser Ionization Mass NanoScope (II)
  Bajo Ken-ichi; Kudo Masato; Ebata Shingo; Fujioka Osamu; Sakaguchi Isao; Yurimoto Hisayoshi; Uchino Kichiro; Ishihara Morio; Itose Satoru; Matsuya Miyuki, Abstracts of Annual Meeting of the Geochemical Society of Japan, 59, 0, 286, 286, 2012
  二次イオン質量分析は高い空間分解能と多元素の高感度な定量が出来るため微小領域の同位体分析において重用されている。しかしながら希ガスはイオン化ポテンシャルが高いことと含有量が微量であることから、天然試料のSIMSでの分析は不可能であった。そこで我々はLaser Ionization MAss nanoScopeを用いて希ガス同位体分析を天然試料に適応するための開発を行っている。この装置は一次イオンビームによりスパッタされた希ガス原子をフェムト秒レーザーによりポストイオン化させることが可能である。従来の希ガス局所分析の空間分解能は100 μm程度であったが、LIMASではサブミクロン(最高空間分解能10 nm)で分析が可能である。この装置を用いてレゴリスブレッチャの太陽風起源希ガスの2次元分布を分析することにより、小惑星表層を覆うレゴリスの形成過程を明らかにすることが本研究の主題である。, GEOCHEMICAL SOCIETY OF JAPAN, Japanese
• S12-07 イトカワでのレゴリス年代学(口頭セッション12:はやぶさ,口頭発表)
  長尾 敬介; 岡崎 隆司; 中村 智樹; 三浦 弥生; 大澤 崇人; 馬上 謙一; 松田 伸太郎; 海老原 充; Ireland Trevor R.; 北島 富美雄; 奈良岡 浩; 野口 高明; 土山 明; 上椙 真之; 圦本 尚義; Zolensky Michael E.; 白井 慶; 安部 正真; 矢田 達; 石橋 之宏; 藤村 彰夫; 向井 利典; 上野 宗孝; 岡田 達明; 吉川 真; 川口 淳一郎, 日本惑星科学会秋期講演会予稿集, 2011, 19, 19, 23 Oct. 2011
  日本惑星科学会, Japanese
• SOLAR NOBLE GASES IN ITOKAWA REGOLITH MATERIALS RETURNED BY THE HAYABUSA MISSION
  K. Nagao; R. Okazaki; T. Nakamura; Y. N. Miura; T. Osawa; K. Bajo; S. Matsuda; M. Ebihara; T. R. Ireland; F. Kitajima; H. Naraoka; T. Noguchi; A. Tsuchiyama; M. Uesugi; H. Yurimoto; M. E. Zolensky; K. Shirai; M. Abe; T. Yada; Y. Ishibashi; A. Fujimura; T. Mukai; M. Ueno; T. Okada; M. Yoshikawa; J. Kawaguchi, METEORITICS & PLANETARY SCIENCE, 46, A171, A171, Jul. 2011
  English, Summary international conference
• CONSTRAINTS ON COSMIC-RAY EXPOSURE HISTORY OF THE VACA MUERTA MESOSIDERITE FROM NOBLE GAS ANALYSIS OF NEUTRON-IRRADIATED SAMPLES
  K. Bajo; H. Sumino; K. Nagao, METEORITICS & PLANETARY SCIENCE, 46, A14, A14, Jul. 2011
  English, Summary international conference
• 鉄道博物館開館三周年特別企画展「御料車--知られざる美術品」の開催にいたるまで
  松久 謙一; 馬上 弥生, JR gazette, 69, 1, 64, 67, Jan. 2011
  東京 : 交通新聞社, Japanese
• The implantation process of solar wind noble gases into asteroids
  Miyazaki Yusuke; Bajo Kenichi; Sumino Hirochika; Yamamoto Yasuo; Fukura Satoshi; Kagi Hiroyuki; Nagao Keisuke, Abstracts of Annual Meeting of the Geochemical Society of Japan, 58, 0, 168, 168, 2011
  小惑星や宇宙塵の表層から数百nmまでの深さに打ち込まれている。太陽風起源希ガスは太陽の元素組成および同位体組成を理解する上で重要であるが、深さ方向の打ち込みプロファイルを調べた実験データは、Genesis missionで得られた太陽風回収ターゲットや月面土壌を、表面から段階的に酸分解して希ガスを抽出したもののみであり（Grimberg et al, 2008）、コンドライト的組成の小惑星表層への太陽風起源希ガスの打ち込みについては調べられていない。本研究では、1.固体中へのイオン注入を三次元シミュレートするソフトウエアであるSRIMを用いた太陽風起源希ガス注入の再現、2.疑似小惑星表層サンプルの段階加熱希ガス分析を行う。そして得られた深さ方向の元素組成・同位体比変動を定式化し、宇宙風化作用（Raquin et al, 2009）も考慮した小惑星表層への太陽風起源希ガス注入過程を明らかにする。, GEOCHEMICAL SOCIETY OF JAPAN
• Noble gas analysis by Laser Ionization Mass NanoScope (LIMAS)
  Bajo Ken-ichi; Ebata Shingo; Uchino Kiichiro; Ishihara Morio; Itose Satoru; Matsuya Miyuki; Kudo Masato; Yurimoto Hisayoshi, Abstracts of Annual Meeting of the Geochemical Society of Japan, 58, 0, 177, 177, 2011
  二次イオン質量分析は高い空間分解能と多元素の高感度な定量が出来るため微小領域の同位体分析において重用されている。しかしながら希ガスはイオン化ポテンシャルが高いことと、含有量が極微量であることから二次イオン質量分析での分析は不可能であった。そこで発表者らは新たに開発された超高感度極微量質量分析システムを用いて希ガス同位体分析を試みている。このシステムでは一次イオンビームによりスパッタされた希ガス原子を高光子密度のレーザーを照射することにより希ガス原子をイオン化させることができる。発表者らは隕石中の太陽風起源希ガスに注目して実験を行っており、今後はSolar-gas-rich 隕石から太陽風起源希ガス同位体の検出を試みる予定である。, GEOCHEMICAL SOCIETY OF JAPAN
• Development of Laser Ionization Mass Nanoscope:LIMAS""
  Ebata Shingo; Bajo Ken-ichi; Uchino Kiichiro; Ishihara Morio; Itose Satoru; Matsuya Miyuki; Kudo Masato; Yurimoto Hisayoshi, Abstracts of Annual Meeting of the Geochemical Society of Japan, 58, 0, 176, 176, 2011
  In sample-return missions, samples collected on planets or asteroids are returned to the Earth by space spacecrafts, and then analyzed in laboratories. However, amounts of samples would be limited. Here, we have developed a novel time-of-flight SNMS (TOF-SNMS) system with ultra-high sensitivity and ultra-high mass resolving power. This instrument would be effective for ultrahigh sensitive analysis of nano-size particles such as return samples., GEOCHEMICAL SOCIETY OF JAPAN
• I-Xe AND Ar-39-Ar-40 AGES OF THE UNIQUE ACHONDRITE GRA 06129
  K. Bajo; S. Matsuda; H. Sumino; K. Nagao; T. Mikouchi, METEORITICS & PLANETARY SCIENCE, 45, A11, A11, Jul. 2010
  English, Summary international conference
• Determination of trace amounts of halogens using noble gas mass spectrometry
  Saito Takehiko; Sumino Hirochika; Bajo Kenichi; Toyama Chiaki; Muramatsu Yasuyuki; Nagao Keisuke, Abstracts of Annual Meeting of the Geochemical Society of Japan, 57, 0, 185, 185, 2010
  An extension of 40Ar-39Ar and I-Xe dating methods enables us to simultaneously determine trace amounts of noble gases, halogens, potassium, calcium, barium and uranium using high-sensitive noble gas mass spectrometry. This method has several advantages: (i) detection limits for halogens are two or three orders of magnitude lower than those of other conventional analytical methods, and (ii) several components of different origin can be distinguished based on their relationships with specific noble gas isotopes and by using various noble gas extraction methods. We have set up a mass spectrometric system for precise noble gas isotope measurement of neutron-irradiated geological samples and meteorites. Br and I (and Cl to some extent) concentrations in GSJ and USGS rock standards determined by this method are systematically lower than the literature values. This difference would be due to a contribution of surface adsorbed halogens on powder of standards which are not detected as converted noble gas isotopes because they are removed by pumping in the vacuum line for noble gas analysis., GEOCHEMICAL SOCIETY OF JAPAN
• Isotopic compositions of noble gases in zircons above the Bangombe natural reactor
  KIKUCHI MAKIKO; NAGAO KEISUKE; BAJO KEN-ICHI; HIDAKA HIROSHI, Abstracts of Annual Meeting of the Geochemical Society of Japan, 57, 0, 39, 39, 2010
  中央アフリカ，ガボン共和国のオクロ・バゴンベウラン鉱床では，約20億年前に大規模な核分裂連鎖反応が起こったことが確認されている。これまでに発見された18か所の天然原子炉の中で，バゴンベ天然原子炉は地表から約12ｍの浅所に位置しており，激しい風化作用を受けている。原子炉上部を覆っている粘土層中の二次ウラン鉱物，ジルコンの局所同位体分析の結果から，これらの鉱物には原子炉部分またはその周辺に存在していたウランならびに核分裂起源軽希土類元素が再分配され固定されていることが明らかとなった。また，粘土層中に見出されるジルコンのウラン含有量（<0.01-22.2 wt.%）は非常に幅広いことが示されている。本研究では，バゴンベ天然原子炉上部に存在するジルコンを用いて，1)レーザー抽出法による一粒のジルコンの希ガス同位体分析法の確立，2)ジルコン内部に存在する核分裂起源Kr, Xeの検出，および希ガス同位体組成の変動に関与する核反応の特定，を目指し測定を行った。, GEOCHEMICAL SOCIETY OF JAPAN
• (KR)-K-81-KR AGE OF THE VACA MUERTA MESOSIDERITE: ON THEIR PARENT BODY EXPOSURE
  K. Bajo; K. Nagao, METEORITICS & PLANETARY SCIENCE, 44, A26, A26, Jul. 2009
  English, Summary international conference
• Measurements of high-energy neutron cross sections for accurate cosmogenic nuclide production rates
  K. Nishiizumi; K. C. Welten; H. Matsumura; M. W. Caffee; K. Ninomiya; T. Omoto; R. Nakagaki; T. Shima; N. Takahashi; S. Sekimoto; H. Yashima; S. Shibata; K. Bajo; K. Nagao; N. Kinoshita; M. Imamura; J. Sisterson; A. Shinohara, GEOCHIMICA ET COSMOCHIMICA ACTA, 73, 13, A945, A945, Jun. 2009
  English, Summary international conference
• Determination of trace amounts of halogens using an extension of Ar-Ar and I-Xe methods
  Sumino Hirochika; Bajo Ken-ichi; Nagao Keisuke, Annual Meeting of the Geological Society of Japan, 2009, 0, 76, 76, 2009
  The Geological Society of Japan, Japanese
• Cosmogenic noble gases and cosmic-ray exposure age of individual Allende chondrule
  Nakamura Yoshinobu; Bajo Ken-ichi; Nakashima Daisuke; Nagao Keisuke, Abstracts of Annual Meeting of the Geochemical Society of Japan, 56, 0, 158, 158, 2009
  始原的隕石は、現在、我々が手にできる太陽系初期の情報を持つ数少ない試料のひとつである。そのため、これらが「いつ」「どのように」形成したのかを明らかにする事は太陽系の進化を考える上で重要である。我々は、宇宙線照射起源希ガスを用いて、これらの隕石に含まれているコンドリュールの形成時期またはコンドリュールが微惑星に取り込まれるまでの期間を解明することを目的とした。始原的隕石は母天体での変成をあまり受けていないため、コンドリュールが母天体に取り込まれる前の宇宙線照射履歴を残している可能性がある。, GEOCHEMICAL SOCIETY OF JAPAN
• Noble gas analyses of individual chondrules from the Allende CV3 chondrite
  Y. Nakamura; K. Bajo; D. Nakashima; K. Nagao, METEORITICS & PLANETARY SCIENCE, 43, 7, A110, A110, Jul. 2008
  English, Summary international conference
• Cosmogenic histories in gibeon and campo del cielo iron meteorites
  M. Honda; H. Nagai; K. Nagao; K. Bajo; Y. Oura, METEORITICS & PLANETARY SCIENCE, 43, 7, A59, A59, Jul. 2008
  English, Summary international conference
• Noble gases in a gibeon iron meteorite fragment heavily shielded to cosmic rays
  K. Bajo; K. Nagao; M. Honda, METEORITICS & PLANETARY SCIENCE, 43, 7, A21, A21, Jul. 2008
  English, Summary international conference
• Noble gas analyses of small extraterrestrial samples
  Nagao Keisuke; Bajo Kenichi; Okazaki Ryuji; Nakamura Tomoki, Abstracts of Annual Meeting of the Geochemical Society of Japan, 55, 0, 183, 183, 2008
  We will present an outline of results expected from noble gas analyses on small extraterrestrial samples obtained by sample return missions. Methods of extremely small amounts of noble gases, detection limits with our noble gas mass spectrometers, and treatment of small samples will be presented., GEOCHEMICAL SOCIETY OF JAPAN
• Development of small furnace for noble gas extraction from small sample
  Bajo Ken-ichi; Nakamura Yoshinobu; Akaida Tomohiro; Nagao Keisuke, Abstracts of Annual Meeting of the Geochemical Society of Japan, 55, 0, 284, 284, 2008
  地球外物質が持つ希ガス濃度・同位体比は、我々に太陽系の進化やその環境に関する情報を与えてくれている。例えば、隕石中に蓄積された希ガス(宇宙線照射起源3He、21Ne、放射壊変起源4He、40Ar)から宇宙線照射年代やガス保持年代を求めることができる。このような試料、特に宇宙塵のような微小試料の希ガス分析には高感度であることに加え、低ブランク(つまり高S/N比)であることが求められる。我々は微小試料に対して段階加熱法を適用できる低ブランクの加熱炉を開発している。本発表ではその性能と解決すべき点を紹介する。, GEOCHEMICAL SOCIETY OF JAPAN
• Solar noble gases in chondrules
  Matsuda Shintaro; Iio Hiroyuki; Bajo Ken-ichi; Nakashima Daisuke; Nagao Keisuke, Abstracts of Annual Meeting of the Geochemical Society of Japan, 54, 0, 41, 41, 2007
  CRコンドライト隕石は、多量のFe-Ni合金を含有するコンドリュールを有し、またマトリックス内にも多量のFe-Ni合金を有するという点で大変珍しい構造を持つ隕石である。今回の研究ではCRコンドライトNWA852に対してレーザーを用いた局所希ガス分析測定を行った。その結果から太陽風起源希ガスが、マトリックス部分のみならず、コンドリュール部分にも含有されていることが確認された。この結果に基づき、コンドリュール中の太陽起源希ガスの捕獲プロセスについて議論する。, GEOCHEMICAL SOCIETY OF JAPAN
• Isotopic compositions of noble gases in inclusions of Udei Station(IAB iron)
  Bajo Ken-ichi; Nagao Keisuke, Abstracts of Annual Meeting of the Geochemical Society of Japan, 54, 0, 42, 42, 2007
  IAB族は鉄隕石のグループである。これらの隕石中にはケイ酸塩包有物が含まれており、ウィノナイト(始原的エコンドライトの一種)と同一の母天体であると考えられている(Clayton and Mayeda, 1996) 。この隕石グル－プに含まれる希ガスはサブソーラーと呼ばれる元素組成（Crabb and Anders, 1981）に属する。サブソーラーが取り込まれる仕組みは太陽風が天体の元となった微小鉱物表層に撃ち込まれる際に元素及び同位体分別を受けたものであるという報告がある(Okazaki et al., 2001) 。しかし、IAB族の元素組成が本当にサブソーラーであるかどうかはわかっていない。そこで、私はこの隕石の希ガス同位体組成の測定を行った。今回は測定でわかったこと、そして今後の課題について発表する。, GEOCHEMICAL SOCIETY OF JAPAN
• Complex exposure history of Vaca Muerta mesosiderite inferred from noble gases
  K. Nagao; K. Bajo, METEORITICS & PLANETARY SCIENCE, 41, 8, A127, A127, Aug. 2006
  English, Summary international conference
• Gene-Expression in Radiation Sensitive and Insensitive Mouse Lymph Node Cells by Ultraviolet-Ray Stimulation
  NIIMURA Yukio; MOUE Toshiko; NAGAI Ken-ichi, The Japan Radiation Research Society Annual Meeting Abstracts, 2006, 329, 329, 2006
  Mouse lymph node cell (M10) is highly sensitive to X-ray irradiation. This cell is also sensitive against UV-ray irradiation. Growth of this cell depended on the UV-rays (310 nm, band B) irradiation, and the cell growth was suppressed in proportion to the UV irradiation time. UV irradiation doses (10, 20, 30 and 60sec) showed the induction of cell apoptosis and necrosis. Cell sorting analysis distinguished the difference of the apoptosis and the necrosis of M10 cells. Apoptotic cells increased in proportion to UV-irradiation. We also analyzed the gene expression in the UV-irradiated cells using DNA array technology. Dynamic changes of 597 genes after the UV-B (310 nm) irradiation of three doses (10, 20 and 30sec) were investigated on DNA array membranes. Radioactivities obtained from imaging analyzer were analyzed using software of ArrayGauge. The expression of mRNA was further analyzed by EX-ARRAY program. Time course of the gene expression was investigated at 2h and 5h after the irradiation. The expression of almost genes reduced in proportion to the doses. The comparison of the gene expression with the parental cells (L5178Y) by northern blot hybridization demonstrated the activation of several genes (MCP-3, Cdx-2, HMG-14, glucose-regulated protein gene, serotonin receptor gene and Hox-2.4)., The Japanese Radiation Research Society, Japanese
• Noble gas isotope analysis of Gibeon iron meteorite
  Bajo Ken-ichi; Yamamoto Yukio; Nagao Keisuke; Honda Masatake, Abstracts of Annual Meeting of the Geochemical Society of Japan, 53, 0, 154, 154, 2006
  鉄隕石Gibeon(IVA)のいろいろなフラグメントの希ガス(He、Ne、Ar)同位体組成を測定した。これらの希ガスは宇宙線照射起源であり、地球落下前の鉄隕石の表面付近と中心部分の3Heのガス量の分布が6桁ほども差があることがわかった。このような鉄隕石のデータはこれまで報告されたことがない。鉄隕石の希ガス分析は、石質隕石の分析に較べて様々な実験的困難が伴う。本講演では、特に宇宙線照射起源希ガス濃度が低い中心部の試料の測定方法について詳細に述べる。, GEOCHEMICAL SOCIETY OF JAPAN

• In situ helium isotope imaging of meteorites
  K. Bajo; N. Kawasaki; T. Obase; I. Sakaguchi; T. T. Suzuki; S. Itose; M. Matsuya; M. Ishihara; K. Uchino; H. Yurimoto
  23rd Scientific International Symposium on SIMS, 14 Jun. 2024, English, Invited oral presentation
  13 Jun. 2024 - 14 Jun. 2024, [Invited]
• 同位体ナノスコープを用いた地球外物質の局所ヘリウム分析
  馬上謙一
  マイクロビームアナリシス技術部会第5回研究会, 28 Sep. 2021, Japanese, Invited oral presentation
  [Invited]
• 二次イオン質量分析法と宇宙地球化学への応用
  馬上謙一
  2020年 日本地球化学会 ショートコース (オンライン), Sep. 2020, Japanese, Invited oral presentation
  [Invited]
• SNMSを用いた太陽風起源希ガスの深さ方向分析
  馬上 謙一
  日本鉄鋼協会 評価・分析・解析部会, Nov. 2017, Japanese, Invited oral presentation
  [Invited]
• 小惑星「イトカワ」の微粒子解析に貢献するNI PXIモジュール式計測器
  馬上謙一
  NIDays 2013, 01 Nov. 2013, Japanese, Invited oral presentation
  [Invited], [Domestic Conference]

• 地球化学特論, 2024年, 修士課程, 理学院
• 宇宙地球化学特論, 2024年, 修士課程, 理学院
• 地球惑星科学実験Ⅲ, 2024年, 学士課程, 理学部
• 現代地球惑星科学概論１, 2024年, 学士課程, 理学部
• 地球惑星物質科学実習, 2024年, 学士課程, 理学部

• Apr. 2023 - Present
  日本地球惑星科学連合
• The Meteoritical Society
• THE MASS SPECTROMETRY SOCIETY OF JAPAN
• GEOCHEMICAL SOCIETY OF JAPAN

• 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
  Apr. 2025 - Mar. 2029
  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, 25H00678
• Solar activities from pre-main-sequence stage to present
  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (S)
  Jul. 2021 - Mar. 2026
  圦本 尚義; 馬上 謙一; 青木 順
  本研究の目的は，前主系列星期から現在に至る46億年間の太陽活動の変遷を解明することである．そのために，46億年前に太陽風照射されたガスリッチ炭素質隕石；40億年前，30億年前，20億年前，10億年前，1億年前に太陽風照射された月面レゴリス；百万年前に太陽風照射された小惑星イトカワ粒子の分析を行う．これらの分析結果から解析されるkeVレベルからMeVレベルに至る運動エネルギーをもつ粒子放射スペクトルの比較により，太陽活動の経年変化を解明する．本研究は未踏の新規研究分野であり，その成果は恒星の進化を探るのみならず，原始惑星系円盤進化，惑星進化，宇宙風化，宇宙天気などの理解に向けて大きな意味を持つ．本年度は以下の研究成果が得られた．
  1. 同位体ナノスコープによる希ガスの組成分析・同位体分析 本研究では，世界唯一の希ガス局所分析が可能な同位体ナノスコープを用い，地球外物質の固体粒子局所表面の希ガス濃度・同位体分布より太陽風の照射量とエネルギー分布を決定することにより，過去の太陽活動を解析している．同位体ナノスコープの周回イオン軌道中に挿入する誘電電荷検出器を考案し，電荷増幅器による誘導電荷検出システムの設計を完了した．また，同位体ナノスコープの広領域イメージング化の装置開発を完了した． この装置を用い，Heに加え，新たにNe, Arの分析法の開発を進めている．
  2. 月粒子中に記録される太陽活動 1億年前までの太陽活動をNASA APOLLO探査機が持ち帰った月粒子（71501）から解読したHeの深さ方向分布を測定し，太陽風照射量を求めた．
  3. 隕石中に記録される太陽活動 前主系列星期の太陽活動を解析するためにガスリッチ炭素質隕石NWA 801を分析した．開発した広領域イメージング装置によりこの隕石中の太陽風希ガスの濃集箇所を特定した．今後，太陽風起源He, Ne, Ar分布を明らかにする.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (S), Hokkaido University, 21H04985
• Solar activity change between stages of protosun and main-sequense
  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
  05 Apr. 2021 - 31 Mar. 2024
  圦本 尚義; 馬上 謙一
  本研究の目的は，原始星太陽と主系列星太陽との間の太陽活動の違いを解明することである．そのために，46億年前に太陽風照射されたガスリッチ炭素質隕石； 1億年前に太陽風照射された月面レゴリス；百万年前に太陽風照射された小惑星イトカワ粒子の分析を行う．これらの分析結果から解析された粒子放射(太陽風)スペクトルの対比により，前主系列星期と主系列星期の太陽活動の特徴を解明する．本研究は未踏の新規研究分野であり，その成果は，恒星の進化を探るのみならず，原始惑星系円盤進化，惑星進化，宇宙風化，宇宙天気などの理解に向けて大きな意味を持つ．本年度は以下の研究を開始し，基盤S研究に引き継がれた．
  1. 同位体ナノスコープによる希ガスの組成分析・同位体分析
  希ガス超局所分析(空間分解能：縦800nm横800nm深5nm)が可能な同位体ナノスコープを用い，地球外物質の固体粒子局所表面の希ガス濃度・同位体分布より太陽風の照射量とエネルギー分布を決定する．今年度は，1辺100umを超える試料表面の広領域イメージングを可能にするための一段階として，真空ゲートバルブを購入し，改造にとりかかった．この改造は，新規に採択された基盤S研究に引き継がれた．
  2. 小惑星イトカワ粒子中に記録される太陽活動
  百万年前までの太陽活動をJAXA はやぶさ探査機が持ち帰った小惑星イトカワ粒子から解読する．イトカワ粒子の分析を行い，粒子の表面から太陽風Heの3次元濃度分布(nmスケールの分解能)の測定を開始し，Heは粒子表面下50nm付近に多く存在しているのを確認した．これは低速太陽風(keV/核子)の照射が多かったことを示す．今後は本研究課題を引き継いだ基盤S研究において，深さ400nm以深のHeを分析し，百keV/核子のエネルギーを持つコロナ質量放出の検出と定量を目指す．
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 21H04502
• マントルウェッジにおける沈み込み由来炭素の探索
  科学研究費助成事業 基盤研究(B)
  01 Apr. 2020 - 31 Mar. 2023
  山本 順司; 馬上 謙一; 吉村 俊平
  本研究では“マントルウェッジにおける海洋プレート由来炭素の有無”を検証することを目指している．地球表層の炭質物が地球内部に沈み込むプロセスについては様々な分野で研究が重ねられているが，地表へ戻る道筋に関してはモデルの域を出ない．マントルウェッジへの海洋プレート由来炭素の流入は，マントルウェッジにおけるマントル対流やマグマ生成，揮発性成分の循環など，地球の表層と内部をつなぐ熱や物質の流れに大きな影響を及ぼす．そこで本研究では，地球表層物質とマントル物質間で同位体比が顕著に異なる炭素に注目し，マントルウェッジのかんらん岩捕獲岩中に地表物質由来の炭素が含まれているか調べることを主眼に置いている．
  従来の研究の問題点は，地表地殻の混入が避けられない火山岩や火山性ガスを用いていたことである．そのため，地表物質由来の炭素同位体比が得られても，沈み込み由来炭素を検出したのか火道地殻の炭素が混入したのか判別できない状況に陥っていた．そこで本研究では，マントルウェッジ由来の捕獲岩に存在する流体包有物の炭素同位体比を直接測ることで，マントルウェッジにおけるリサイクル炭素の有無を査定する．
  そのため本研究では，マントル由来の捕獲岩中の流体包有物の炭素や窒素の同位体比を測定することを目指しており，令和３年度においては，CO2およびN2流体の炭素同位体比および窒素同位体比を決定するための測定装置を組み上げる作業を行った．炭素同位体比については10パーミルを下回る精度で決定できるようになり，窒素同位体比についても16パーミルの精度に達し，その成果を国際誌に投稿した．
  日本学術振興会, 基盤研究(B), 北海道大学, 20H02000
• Noble gas isotope analysis for individual presolar grain to study environment of interstellar material
  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
  01 Apr. 2020 - 31 Mar. 2023
  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．
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 20K04036
• Activity of the proto-Sun revealed by multi-isotope analyses
  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)
  01 Apr. 2015 - 31 Mar. 2018
  Bajo Ken-ichi; OKAZAKI Ryuji; KAWASAKI Noriyuki
  Ca-Al-rich inclusions (CAIs) in primitive chondrite meteorites contain detectable amounts of extinct nuclides such as 26Al (half life of 0.705 Myr) and 10Be (half life of 1.36 Myr). Especially, excess 10Be in CAIs, which would have been produced by solar cosmic ray (SCR) spallation, suggests that the proto-sun was more radiative than the present sun [1]. The intense SCRs could also produce 22Na, which decays to 22Ne (half life of 2.61 yr), from Mg, Al, and Si via spallation reaction. As sodium is a minor element composing melilite crystals of igneous CAIs [2, 3], excess 22Na could be found in CAIs formed at the early stage of the solar system evolution. However, such CAIs with excess 22Ne derived from 22Na have not been observed . Here, we report the excess in 22Ne in an igneous CAI from Allende CVox.
  Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Hokkaido University, 15K17791
• はやぶさ，Genesis，月試料による太陽活動と小天体表面の粒子運動の研究
  科学研究費助成事業 基盤研究(A)
  01 Apr. 2016 - 31 Mar. 2017
  圦本 尚義; 馬上 謙一
  本研究の目的は，宇宙空間において太陽風の直接照射を受けている固体微粒子表面直下の希ガス３次元分布を解析し，照射当時の太陽活動，すなわち，太陽風のエネルギー分布を決定することである．さらにこの分析を微粒子表面全体にわたり行い，天体上における微粒子の運動状態を特定することである．従来，このようなナノメーター空間分解能を持った希ガス分析は不可能であったが，申請者たちが開発した同位体ナノスコープが実現可能とした．人類は，現在，太陽風が直接照射された３種類の物質を宇宙から持ち帰っている．月，はやぶさ，Genesis試料である．これらは順に数十億年，数百～千年，現在の太陽風を記録しているので，太古代から現在に至る太陽活動の経時変化の情報が期待できる．また，試料表面に照射された太陽風の不均質性から月とイトカワとの天体サイズの違いによる小天体表面の粒子運動テクトニクスの理解が進むことが期待される．初年度は，Genesisターゲットの太陽風希ガスその場分析を重点的に行い，太陽活動と固体表面に打ち込まれた希ガス分布との対応，特に，フレア現象の記録の発見を目指した．そのため次の実験を行った．定常太陽風と太陽フレアを模擬したエネルギーを持つ希ガスイオンをGenesisターゲットにイオン注入することにより模擬試料を作成した．太陽フレア起源のHeをGenesisターゲットから検出した． 小天体表面のダイナミックスを解明するための分析をするために，現状の希ガス測定時間を短くする必要がある．この分析時間のボトルネックは大容量の飛行時間質量スペクトルのメモリーへの転送速度である．この転送速度を向上させるアルゴリズムを開発した．
  日本学術振興会, 基盤研究(A), 北海道大学, 16H02239
• A challenge to in-situ submicrometer (U-Th)/He chronology for minerals.
  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
  01 Apr. 2015 - 31 Mar. 2017
  YURIMOTO HISAYOSHI
  (U-Th)/He chronology, which show the lowest closure temperature among chronological methods, is useful for analysis of geological history under low temperature such as formation processes of mountains. Thus, in-situ microanalyses of He in minerals are demanded. However, helium microanalyses are limited larger than a spatial resolution of several tens micrometers using conventional techniques, which is not smaller than a typical range of He recoil losses. Here, we develop sputtered neutral mass spectrometry to analyze He in natural zircon crystal. We have succeeded that the in-situ analysis can apply to measure He in zircon having more than 1 ppm concentrations with a spatial resolution of 7 μm which is much smaller than recoil loss range of alpha-particles.
  Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Hokkaido University, 15K13598