研究者業績

臼井 寛裕

ウスイ トモヒロ  (Usui Tomohiro)

基本情報

所属
国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 教授
学位
博士(学術)(岡山大学)

J-GLOBAL ID
201901004664301386
researchmap会員ID
B000348549

外部リンク

Personal HP <https://sites.google.com/site/tomohirousui/>

Google Scholar <https://scholar.google.com/citations?user=iCTuRbUAAAAJ&hl=en>

ISAS astromaterial/curation research group HP <https://curation.isas.jaxa.jp/en/>


論文

 87
  • Alexander B Verchovsky, Feargus A J Abernethy, Mahesh Anand, Ian A Franchi, Monica M Grady, Richard C Greenwood, Simeon J Barber, Martin Suttle, Motoo Ito, Naotaka Tomioka, Masayuki Uesugi, Akira Yamaguchi, Makoto Kimura, Naoya Imae, Naoki Shirai, Takuji Ohigashi, Ming-Chang Liu, Kentaro Uesugi, Aiko Nakato, Kasumi Yogata, Hayato Yuzawa, Yuzuru Karouji, Satoru Nakazawa, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Makoto Yoshikawa, Akiko Miyazaki, Masahiro Nishimura, Toru Yada, Masanao Abe, Tomohiro Usui, Sen-Ichiro Watanabe, Yuichi Tsuda
    Nature communications 15(1) 8075-8075 2024年9月14日  
    Ryugu is the C-type asteroid from which material was brought to Earth by the Hayabusa2 mission. A number of individual grains and fine-grained samples analysed so far for noble gases have indicated that solar wind and planetary (known as P1) noble gases are present in Ryugu samples with concentrations higher than those observed in CIs, suggesting the former to be more primitive compared to the latter. Here we present results of analyses of three fine-grained samples from Ryugu, in one of which Xe concentration is an order of magnitude higher than determined so far in other samples from Ryugu. Isotopically, this Xe resembles P1, but with a much stronger isotopic fractionation relative to solar wind and significantly lower 36Ar/132Xe ratio than in P1. This previously unknown primordial noble gas component (here termed P7) provides clues to constrain how the solar composition was fractionated to form the planetary components.
  • Yuichiro Ueno, Johan A. Schmidt, Matthew S. Johnson, Xiaofeng Zang, Alexis Gilbert, Hiroyuki Kurokawa, Tomohiro Usui, Shohei Aoki
    Nature Geoscience 2024年5月9日  
    Abstract Organic matter found in early Martian sediment may yield clues to the planet’s environmental conditions, prebiotic chemistry and habitability, but its origin remains unclear. Strong 13C depletion in sedimentary organic matter at Gale crater was recently detected by the Curiosity rover. Although this enigmatic depletion remains debated, if correct, a mechanism to cause such strong 13C depletion is required. Here we show from CO2 photolysis experiments and theoretical considerations that solar ultraviolet photolysis of CO2 in a reducing atmosphere can yield strongly 13C-depleted CO. We suggest that atmospheric synthesis of organic compounds from photolysis-produced CO is a plausible mechanism to explain the source of isotopically depleted organic matter in early Martian sediments. Furthermore, this mechanism could explain 13C enrichment of early Martian CO2 without requiring long-term carbon escape into space. A mass balance model calculation using our estimated isotopic fractionation factor indicates the conversion of approximately 20% of volcanic CO2 emissions on early Mars into organics via CO, consistent with the available data for carbon isotopes of carbonate. Although alternative pathways for organic compound production have been proposed, our findings suggest that considerable amounts of organic matter may have been synthesized from CO in a reducing early Martian atmosphere and deposited in sediments.
  • Noriko T. Kita, Kouki Kitajima, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamoto, Wataru Fujiya, Yoshinari Abe, Jérôme Aléon, Conel M. O'D. Alexander, Sachiko Amari, Yuri Amelin, Ken‐ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon‐Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming‐Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing‐Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai‐Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei‐ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    METEORITICS & PLANETARY SCIENCE 2024年4月  
    Abstract Oxygen 3‐isotope ratios of magnetite and carbonates in aqueously altered carbonaceous chondrites provide important clues to understanding the evolution of the fluid in the asteroidal parent bodies. We conducted oxygen 3‐isotope analyses of magnetite, dolomite, and breunnerite in two sections of asteroid Ryugu returned samples, A0058 and C0002, using a secondary ion mass spectrometer (SIMS). Magnetite was analyzed by using a lower primary ion energy that reduced instrumental biases due to the crystal orientation effect. We found two groups of magnetite data identified from the SIMS pit morphologies: (1) higher δ18O (from 3‰ to 7‰) and ∆17O (~2‰) with porous SIMS pits mostly from spherulitic magnetite, and (2) lower δ18O (~ −3‰) and variable ∆17O (0‰–2‰) mostly from euhedral magnetite. Dolomite and breunnerite analyses were conducted using multi‐collection Faraday cup detectors with precisions ≤0.3‰. The instrumental bias correction was applied based on carbonate compositions in two ways, using Fe and (Fe + Mn) contents, respectively, because Ryugu dolomite contains higher amounts of Mn than the terrestrial standard. Results of dolomite and breunnerite analyses show a narrow range of ∆17O; 0.0‰–0.3‰ for dolomite in A0058 and 0.2‰–0.8‰ for dolomite and breunnerite in C0002. The majority of breunnerite, including large ≥100 μm grains, show systematically lower δ18O (~21‰) than dolomite (25‰–30‰ and 23‰–27‰ depending on the instrumental bias corrections). The equilibrium temperatures between magnetite and dolomite from the coarse‐grained lithology in A0058 are calculated to be 51 ± 11°C and 78 ± 14°C, depending on the instrumental bias correction scheme for dolomite; a reliable temperature estimate would require a Mn‐bearing dolomite standard to evaluate the instrumental bias corrections, which is not currently available. These results indicate that the oxygen isotope ratios of aqueous fluids in the Ryugu parent asteroid were isotopically heterogeneous, either spatially, or temporary. Initial water ice accreted to the Ryugu parent body might have ∆17O &gt; 2‰ that was melted and interacted with anhydrous solids with the initial ∆17O &lt; 0‰. In the early stage of aqueous alteration, spherulitic magnetite and calcite formed from aqueous fluid with ∆17O ~ 2‰ that was produced by isotope exchange between water (∆17O &gt; 2‰) and anhydrous solids (∆17O &lt; 0‰). Dolomite and breunnerite, along with some magnetite, formed at the later stage of aqueous alteration under higher water‐to‐rock ratios where the oxygen isotope ratios were nearly at equilibrium between fluid and solid phases. Including literature data, δ18O of carbonates decreased in the order calcite, dolomite, and breunnerite, suggesting that the temperature of alteration might have increased with the degree of aqueous alteration.
  • Kaori Hirata, Tomohiro Usui, Ryuki Hyodo, Hidenori Genda, Ryota Fukai, David J. Lawrence, Nancy L. Chabot, Patrick N. Peplowski, Hiroki Kusano
    Icarus 410 2024年3月1日  
    The formation process of the two Martian moons, Phobos and Deimos, is still debated with two main competing hypotheses: the capture of an asteroid or a giant impact onto Mars. In order to reveal their origin, the Martian Moons eXploration (MMX) mission by Japan Aerospace Exploration Agency (JAXA) plans to measure Phobos’ elemental composition by a gamma-ray and neutron spectrometer called MEGANE. This study provides a model of Phobos’ bulk elemental composition, assuming the two formation hypotheses. Using the mixing model, we established a MEGANE data analysis flow to discriminate between the formation hypotheses by multivariate analysis. The mixing model expresses the composition of Phobos in 6 key lithophile elements that will be measured by MEGANE (Fe, Si, O, Ca, Mg, and Th) as a linear mixing of two mixing components: material from Mars and material from an asteroid as represented by primitive meteorite compositions. The inversion calculation includes consideration of MEGANE's measurement errors (EP) and derives the mixing ratio for a given Phobos composition, based on which the formation hypotheses are judged. For at least 65% of the modeled compositions, MEGANE measurements will determine the origin uniquely (EP = 30%), and this increases from 74 to 87% as EP decreases from 20 to 10%. Although the discrimination performance depends on EP, the current operation plan for MEGANE predicts an instrument performance for EP of 20—30%, resulting in 70% discrimination between the original hypotheses. MEGANE observations can also enable the determination of the asteroid type of the captured body or the impactor. The addition of other measurements, such as MEGANE's measurements of the volatile element K, as well as observations by other MMX remote sensing instruments, will also contribute to the MMX mission's goal to constrain the origin of Phobos.
  • 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 2024年2月  
  • 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, Frédéric Moynier, Ryuji Okazaki, Sara S. Russell, Hirochika Sumino, Michael E. Zolensky, Haruna Sugahara, Shogo Tachibana, Kanako Sakamoto, Masanao Abe, Yuichiro Cho, Kiyoshi Kuramoto
    Meteoritics &amp; Planetary Science 2024年1月11日  
    Abstract Japan Aerospace Exploration Agency's Martian Moons eXploration (MMX) mission will launch a spacecraft in 2024 to return samples from Phobos in 2029. Curatorial work for the returned Phobos samples is critical for the sample allocation without degrading the sample integrity and subsequent sample analysis that will provide new constraints on the origin of Phobos and the evolution of the circum‐Mars environment. The Sample Analysis Working Team of the MMX is designing the sample curation protocol. The curation protocol consists of three phases: (1) quick analysis (extraction and mass spectrometry for gases), (2) pre‐basic characterization (bulk‐scale observation), and (3) basic characterization (grain‐by‐grain observation and allocation of the sample aliquots). Nondestructive analyses within the clean chamber (e.g., visible and near‐infrared spectral imaging) and outside the chamber (e.g., gas mass spectrometry) are incorporated into the curation flow in coordination with the MMX mission instrument teams for ground‐truthing the remote‐sensing data sets. The MMX curation/sample analysis flow enables the seamless integration between the sample and remote‐sensing data sets to maximize the scientific value of the collected Phobos samples.
  • Yasuhiro Oba, Toshiki Koga, Yoshinori Takano, Nanako O. Ogawa, Naohiko Ohkouchi, Kazunori Sasaki, Hajime Sato, Daniel P. Glavin, Jason P. Dworkin, Hiroshi Naraoka, Shogo Tachibana, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei ichiro Watanabe, Yuichi Tsuda
    Nature Communications 14(1) 2023年12月  
    The pristine sample from the near-Earth carbonaceous asteroid (162173) Ryugu collected by the Hayabusa2 spacecraft enabled us to analyze the pristine extraterrestrial material without uncontrolled exposure to the Earth’s atmosphere and biosphere. The initial analysis team for the soluble organic matter reported the detection of wide variety of organic molecules including racemic amino acids in the Ryugu samples. Here we report the detection of uracil, one of the four nucleobases in ribonucleic acid, in aqueous extracts from Ryugu samples. In addition, nicotinic acid (niacin, a B3 vitamer), its derivatives, and imidazoles were detected in search for nitrogen heterocyclic molecules. The observed difference in the concentration of uracil between A0106 and C0107 may be related to the possible differences in the degree of alteration induced by energetic particles such as ultraviolet photons and cosmic rays. The present study strongly suggests that such molecules of prebiotic interest commonly formed in carbonaceous asteroids including Ryugu and were delivered to the early Earth.
  • Masahiro Nishimura, Aiko Nakato, Masanao Abe, Kana Nagashima, Hiromichi Soejima, Toru Yada, Kasumi Yogata, Akiko Miyazaki, Kentaro Hatakeda, Miwa Yoshitake, Ayako Iwamae, Cedric Pilorget, Rosario Brunetto, Damien Loizeau, Jean Pierre Bibring, Lucie Riu, Koki Yumoto, Yuichiro Cho, Yuna Yabe, Seiji Sugita, Motoo Ito, Tatsuaki Okada, Shogo Tachibana, Tomohiro Usui
    Earth, Planets and Space 75(1) 2023年12月  
    The JAXA Astromaterials Science Research Group developed a web-based database system for the Hayabusa2-returned samples from C-type asteroid Ryugu. The Ryugu Sample Database System database (RS-DBS) is designed as an online catalog for users of wide scientific communities to choose their preferred samples and propose the sample loan through the JAXA Ryugu Sample Announcement of Opportunity. Ryugu samples can be sorted and given identification numbers as individual particles larger than 1 mm and aggregate samples consisting of less than 1 mm particle through the Phase1 curation (i.e., the initial description). The RS-DBS lists all samples with analytical data such as a microscopy image, size, mass, spectroscopic data, and shape model obtained by the initial description at the JAXA curation facility. The list also includes research results conducted by previous projects (i.e., the Hayabusa2 initial analysis team and Phase2 curation teams). The RS-DBS, built with open-source technologies, archives the data securely and long-term on the Data Archives and Transmission System (DARTS) at ISAS/JAXA. Graphical Abstract: [Figure not available: see fulltext.]
  • Philippe Schmitt-Kopplin, Norbert Hertkorn, Mourad Harir, Franco Moritz, Marianna Lucio, Lydie Bonal, Eric Quirico, Yoshinori Takano, Jason P. Dworkin, Hiroshi Naraoka, Shogo Tachibana, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hisayoshi Yurimoto, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Tatsuaki Okada, Sei-ichiro Watanabe, Yuichi Tsuda, Kenji Hamase, Aogu Furusho, Minako Hashiguchi, Kazuhiko Fukushima, Dan Aoki, José C. Aponte, Eric T. Parker, Daniel P. Glavin, Hannah L. McLain, Jamie E. Elsila, Heather V. Graham, John M. Eiler, Alexander Ruf, Francois-Regis Orthous-Daunay, Junko Isa, Véronique Vuitton, Roland Thissen, Nanako O. Ogawa, Saburo Sakai, Toshihiro Yoshimura, Toshiki Koga, Haruna Sugahara, Naohiko Ohkouchi, Hajime Mita, Yoshihiro Furukawa, Yasuhiro Oba
    Nature Communications 14(1) 2023年10月16日  
    Abstract The sample from the near-Earth carbonaceous asteroid (162173) Ryugu is analyzed in the context of carbonaceous meteorites soluble organic matter. The analysis of soluble molecules of samples collected by the Hayabusa2 spacecraft shines light on an extremely high molecular diversity on the C-type asteroid. Sequential solvent extracts of increasing polarity of Ryugu samples are analyzed using mass spectrometry with complementary ionization methods and structural information confirmed by nuclear magnetic resonance spectroscopy. Here we show a continuum in the molecular size and polarity, and no organomagnesium molecules are detected, reflecting a low temperature and water-rich environment on the parent body approving earlier mineralogical and chemical data. High abundance of sulfidic and nitrogen rich compounds as well as high abundance of ammonium ions confirm the water processing. Polycyclic aromatic hydrocarbons are also detected in a structural continuum of carbon saturations and oxidations, implying multiple origins of the observed organic complexity, thus involving generic processes such as earlier carbonization and serpentinization with successive low temperature aqueous alteration.
  • Iori Kajitani, Mizuho Koike, Ryoichi Nakada, Gaku Tanabe, Tomohiro Usui, Fumihiro Matsu'ura, Keisuke Fukushi, Tetsuya Yokoyama
    Earth and Planetary Science Letters 620 118345-118345 2023年10月  
  • Yuki Kimura, Takeharu Kato, Toshiaki Tanigaki, Tetsuya Akashi, Hiroto Kasai, Satoshi Anada, Ryuji Yoshida, Kazuo Yamamoto, Tomoki Nakamura, Masahiko Sato, Kana Amano, Mizuha Kikuiri, Tomoyo Morita, Eiichi Kagawa, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Sei-ichiro Watanabe, Yuichi Tsuda, Shogo Tachibana
    SCIENTIFIC REPORTS 13(1) 2023年8月  
    In the samples collected from the asteroid Ryugu, magnetite displays natural remanent magnetization due to nebular magnetic field, whereas contemporaneously grown iron sulfide does not display stable remanent magnetization. To clarify this counterintuitive feature, we observed their nanoscale magnetic domain structures using electron holography and found that framboidal magnetites have an external magnetic field of 300 A m(-1), similar to the bulk value, and its magnetic stability was enhanced by interactions with neighboring magnetites, permitting a disk magnetic field to be recorded. Micrometer-sized pyrrhotite showed a multidomain magnetic structure that was unable to retain natural remanent magnetization over a long time due to short relaxation time of magnetic-domain-wall movement, whereas submicron-sized sulfides formed a nonmagnetic phase. These results show that both magnetite and sulfide could have formed simultaneously during the aqueous alteration in the parent body of the 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 2023年4月1日  査読有り
    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/HRyugu, to be [165 ± 19] × 10−6, which corresponds to δDRyugu = +59 ± 121‰ (2σ). The hydrous mineral D/HRyugu’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.
  • Eric T. Parker, Hannah L. McLain, Daniel P. Glavin, Jason P. Dworkin, Jamie E. Elsila, José C. Aponte, Hiroshi Naraoka, Yoshinori Takano, Shogo Tachibana, Hikaru Yabuta, Hisayoshi Yurimoto, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Satoru Nakazawa, Yuichi Tsuda, Fuyuto Terui, Takaaki Noguchi, Ryuji Okazaki, Sei-ichiro Watanabe, Tomoki Nakamura
    Geochimica et Cosmochimica Acta 347 42-57 2023年4月  
  • Christian Potiszil, Tsutomu Ota, Masahiro Yamanaka, Chie Sakaguchi, Katsura Kobayashi, Ryoji Tanaka, Tak Kunihiro, Hiroshi Kitagawa, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa, Masahiro Nishimura, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Tomohiro Usui, Sei-Ichiro Watanabe, Toru Yada, Kasumi Yogata, Makoto Yoshikawa, Eizo Nakamura
    Nature communications 14(1) 1482-1482 2023年3月17日  
    All life on Earth contains amino acids and carbonaceous chondrite meteorites have been suggested as their source at the origin of life on Earth. While many meteoritic amino acids are considered indigenous, deciphering the extent of terrestrial contamination remains an issue. The Ryugu asteroid fragments (JAXA Hayabusa2 mission), represent the most uncontaminated primitive extraterrestrial material available. Here, the concentrations of amino acids from two particles from different touchdown sites (TD1 and TD2) are reported. The concentrations show that N,N-dimethylglycine (DMG) is the most abundant amino acid in the TD1 particle, but below detection limit in the other. The TD1 particle mineral components indicate it experienced more aqueous alteration. Furthermore, the relationships between the amino acids and the geochemistry suggest that DMG formed on the Ryugu progenitor body during aqueous alteration. The findings highlight the importance of aqueous chemistry for defining the ultimate concentrations of amino acids in primitive extraterrestrial samples.
  • Hikaru Yabuta, George D. Cody, Cécile Engrand, Yoko Kebukawa, Bradley De Gregorio, Lydie Bonal, Laurent Remusat, Rhonda Stroud, Eric Quirico, Larry Nittler, Minako Hashiguchi, Mutsumi Komatsu, Taiga Okumura, Jérémie Mathurin, Emmanuel Dartois, Jean Duprat, Yoshio Takahashi, Yasuo Takeichi, David Kilcoyne, Shohei Yamashita, Alexandre Dazzi, Ariane Deniset-Besseau, Scott Sandford, Zita Martins, Yusuke Tamenori, Takuji Ohigashi, Hiroki Suga, Daisuke Wakabayashi, Maximilien Verdier-Paoletti, Smail Mostefaoui, Gilles Montagnac, Jens Barosch, Kanami Kamide, Miho Shigenaka, Laure Bejach, Megumi Matsumoto, Yuma Enokido, Takaaki Noguchi, Hisayoshi Yurimoto, Tomoki Nakamura, Ryuji Okazaki, Hiroshi Naraoka, Kanako Sakamoto, Harold C. Connolly, Dante S. Lauretta, Masanao Abe, Tatsuaki Okada, Toru Yada, Masahiro Nishimura, Kasumi Yogata, Aiko Nakato, Miwa Yoshitake, Ayako Iwamae, Shizuho Furuya, Kentaro Hatakeda, Akiko Miyazaki, Hiromichi Soejima, Yuya Hitomi, Kazuya Kumagai, Tomohiro Usui, Tasuku Hayashi, Daiki Yamamoto, Ryota Fukai, Seiji Sugita, Kohei Kitazato, Naru Hirata, Rie Honda, Tomokatsu Morota, Eri Tatsumi, Naoya Sakatani, Noriyuki Namiki, Koji Matsumoto, Rina Noguchi, Koji Wada, Hiroki Senshu, Kazunori Ogawa, Yasuhiro Yokota, Yoshiaki Ishihara, Yuri Shimaki, Manabu Yamada, Chikatoshi Honda, Tatsuhiro Michikami, Moe Matsuoka, Naoyuki Hirata, Masahiko Arakawa, Chisato Okamoto, Masateru Ishiguro, Ralf Jaumann, Jean-Pierre Bibring, Matthias Grott, Stefan Schröder, Katharina Otto, Cedric Pilorget, Nicole Schmitz, Jens Biele, Tra-Mi Ho, Aurélie Moussi-Soffys, Akira Miura, Hirotomo Noda, Tetsuya Yamada, Keisuke Yoshihara, Kosuke Kawahara, Hitoshi Ikeda, Yukio Yamamoto, Kei Shirai, Shota Kikuchi, Naoko Ogawa, Hiroshi Takeuchi, Go Ono, Yuya Mimasu, Kent Yoshikawa, Yuto Takei, Atsushi Fujii, Yu-ichi Iijima, Satoru Nakazawa, Satoshi Hosoda, Takahiro Iwata, Masahiko Hayakawa, Hirotaka Sawada, Hajime Yano, Ryudo Tsukizaki, Masanobu Ozaki, Fuyuto Terui, Satoshi Tanaka, Masaki Fujimoto, Makoto Yoshikawa, Takanao Saiki, Shogo Tachibana, Sei-ichiro Watanabe, Yuichi Tsuda
    Science 379(6634) 2023年2月24日  査読有り
    Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugu’s parent body.
  • Daisuke Nakashima, Tomoki Nakamura, Mingming Zhang, Noriko T. Kita, Takashi Mikouchi, Hideto Yoshida, Yuma Enokido, Tomoyo Morita, Mizuha Kikuiri, Kana Amano, Eiichi Kagawa, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Satoru Nakazawa, Fuyuto Terui, Hisayoshi Yurimoto, Takaaki Noguchi, Hikaru Yabuta, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Sei-ichiro Watanabe, Shogo Tachibana, Yuichi Tsuda
    Nature Communications 14(1) 532-532 2023年2月16日  
    Abstract Chondrule-like objects and Ca-Al-rich inclusions (CAIs) are discovered in the retuned samples from asteroid Ryugu. Here we report results of oxygen isotope, mineralogical, and compositional analysis of the chondrule-like objects and CAIs. Three chondrule-like objects dominated by Mg-rich olivine are 16O-rich and -poor with Δ17O (=δ17O – 0.52 × δ18O) values of ~ –23‰ and ~ –3‰, resembling what has been proposed as early generations of chondrules. The 16O-rich objects are likely to be melted amoeboid olivine aggregates that escaped from incorporation into 16O-poor chondrule precursor dust. Two CAIs composed of refractory minerals are 16O-rich with Δ17O of ~ –23‰ and possibly as old as the oldest CAIs. The discovered objects (&lt;30 µm) are as small as those from comets, suggesting radial transport favoring smaller objects from the inner solar nebula to the formation location of the Ryugu original parent body, which is farther from the Sun and scarce in chondrules. The transported objects may have been mostly destroyed during aqueous alteration in the Ryugu parent body.
  • Jose C. Aponte, Jason P. Dworkin, Daniel P. Glavin, Jamie E. Elsila, Eric T. Parker, Hannah L. McLain, Hiroshi Naraoka, Ryuji Okazaki, Yoshinori Takano, Shogo Tachibana, Guannan Dong, Sarah S. Zeichner, John M. Eiler, Hisayoshi Yurimoto, Tomoki Nakamura, Hikaru Yabuta, Fuyuto Terui, Takaaki Noguchi, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Satoru Nakazawa, Yuichi Tsuda, Sei-ichiro Watanabe
    EARTH PLANETS AND SPACE 75(1) 2023年2月  
    Evaluating the molecular distribution of organic compounds in pristine extraterrestrial materials is cornerstone to understanding the abiotic synthesis of organics and allows us to better understand the molecular diversity available during the formation of our solar system and before the origins of life on Earth. In this work, we identify multiple organic compounds in solvent extracts of asteroid Ryugu samples A0106 and C0107 and the Orgueil meteorite using two-dimensional gas chromatography and time-of-flight high resolution mass spectrometry (GCxGC-HRMS). Our analyses found similarities between the molecular distribution of organic compounds in Ryugu and the CI carbonaceous chondrite Orgueil. Specifically, several PAHs and organosulfides were found in Ryugu and Orgueil suggesting an interstellar and parent body origin for these compounds. We also evaluated the common relationship between Ryugu, Orgueil, and comets, such as Wild-2; however, until comprehensive compound-specific isotopic analyses for these organic species are undertaken, and until the effects of parent body processes and Earth's weathering processes on meteoritic organics are better understood, their parent-daughter relationships will remain unanswered. Finally, the study of organic compounds in Ryugu samples and the curation practices for the future preservation of these unvaluable materials are also of special interest for future sample return missions, including NASA's OSIRIS-REx asteroid sample return mission.
  • 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) 2022年12月16日  査読有り
    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.
  • 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 Pravdivtseva, Henner Busemann, My E.I. Riebe, Jamie Gilmour, Jisun Park, Ken-ichi Bajo, Kevin Righter, Saburo Sakai, Shun Sekimoto, Fumio Kitajima, Sarah A. Crowther, Naoyoshi Iwata, Naoki Shirai, Mitsuru Ebihara, Reika Yokochi, Kunihiko Nishiizumi, Keisuke Nagao, Jong Ik Lee, Patricia Clay, Akihiro Kano, Marc W. Caffee, Ryu Uemura, Makoto Inagaki, Daniela Krietsch, Colin Maden, Mizuki Yamamoto, Lydia Fawcett, Thomas Lawton, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Hikaru Yabuta, Hisayoshi Yurimoto, Yuichi Tsuda, Sei-ichiro Watanabe, 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, Trevor Ireland, Harold C. Connolly, Dante S. Lauretta, Shogo Tachibana
    Science Advances 8(46) 2022年11月18日  
    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.
  • Timo Hopp, Nicolas Dauphas, Yoshinari Abe, Jérôme Aléon, Conel M O'D Alexander, Sachiko Amari, Yuri Amelin, Ken-Ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W Carlson, Marc Chaussidon, Byeon-Gak Choi, Andrew M Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N Krot, Ming-Chang Liu, Yuki Masuda, Kevin D McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-Ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Science advances 8(46) eadd8141 2022年10月20日  
    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 inwards 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.
  • 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 Jr, Dante Lauretta, Sei-Ichiro Watanabe, Yuichi Tsuda
    Science (New York, N.Y.) 379(6634) eabo0431 2022年10月20日  
    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.
  • Jens Barosch, Larry R. Nittler, Jianhua Wang, Conel M. Conel, Bradley T. De Gregorio, Cécile Engrand, Yoko Kebukawa, Kazuhide Nagashima, Rhonda M. Stroud, Hikaru Yabuta, Yoshinari Abe, Jérôme Aléon, 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, Jérémie Mathurin, Kevin D. McKeegan, Gilles Montagnac, Mayu Morita, Smail Mostefaoui, Kazuko Motomura, Frédéric 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 Schönbächler, 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
    Astrophysical Journal Letters 935(1) 2022年8月1日  査読有り
    We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2 mission. We report the detection of all major presolar grain types with O- and C-anomalous isotopic compositions typically identified in carbonaceous chondrite meteorites: 1 silicate, 1 oxide, 1 O-anomalous supernova grain of ambiguous phase, 38 SiC, and 16 carbonaceous grains. At least two of the carbonaceous grains are presolar graphites, whereas several grains with moderate C isotopic anomalies are probably organics. The presolar silicate was located in a clast with a less altered lithology than the typical extensively aqueously altered Ryugu matrix. The matrix-normalized presolar grain abundances in Ryugu are 4.8 − 2.6 + 4.7 ppm for O-anomalous grains, 25 − 5 + 6 ppm for SiC grains, and 11 − 3 + 5 ppm for carbonaceous grains. Ryugu is isotopically and petrologically similar to carbonaceous Ivuna-type (CI) chondrites. To compare the in situ presolar grain abundances of Ryugu with CI chondrites, we also mapped Ivuna and Orgueil samples and found a total of 15 SiC grains and 6 carbonaceous grains. No O-anomalous grains were detected. The matrix-normalized presolar grain abundances in the CI chondrites are similar to those in Ryugu: 23 − 6 + 7 ppm SiC and 9.0 − 3.6 + 5.4 ppm carbonaceous grains. Thus, our results provide further evidence in support of the Ryugu-CI connection. They also reveal intriguing hints of small-scale heterogeneities in the Ryugu samples, such as locally distinct degrees of alteration that allowed the preservation of delicate presolar material.
  • Kaori Hirata, Tomokatsu Morota, Seiji Sugita, Carolyn M. Ernst, Tomohiro Usui
    Icarus 382 2022年8月  
    The MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) mission by the National Aeronautics and Space Administration revealed that ~27% of the surface of Mercury is occupied by smooth plains potentially formed by magma eruptions. Most of these smooth plain units are located on the floors of the impact basins; these plains occupy a surface area that is approximately seven times larger in the northern hemisphere than in the southern hemisphere. This suggests a difference in thermal conditions in the mantle and/or the ease of magma eruption between hemispheres. This study re-estimated magma eruption ages and volumes within the Rembrandt and Caloris basins; these are representative impact basins in the southern and northern hemispheres, respectively. The estimations of eruption ages and volumes were carried out by measuring crater size-frequency distributions and the diameters of partially buried craters. The formation and eruption ages of the Rembrandt and the Caloris basins were estimated by adopting the porous-target chronology model; the formation ages were estimated as 3.93 ± 0.06 and 3.94 ± 0.04 Gy, while their eruption ages were from 3.87 ± 0.04 to 3.76 ± 0.01 Gy and 3.88 ± 0.03 to 3.74 ± 0.01 Gy, respectively. The observed crater size-frequency distributions in both basins might show multiple resurfacing from episodic eruptions, as suggested by previous numerical simulations of Mercurian thermal evolution. The estimated magma eruption fluxes in the Caloris basin (9.3–15.1 km/Gy) were at most, three times larger than that in the Rembrandt basin (5.2–12.3 km/Gy). Given its larger diameter, the crust beneath the Caloris basin is likely to be ~1.8 times thinner than the crust beneath the Rembrandt basin. This will make it easier for magma to ascend to the surface beneath Caloris than beneath Rembrandt; as such, quantities of magma production in the mantle beneath the two basins should not differ by a factor of <3. These results suggest that there are no large spatial variations in the abundance of heat-producing elements in the mantle and lower crust of Mercury unlike the concentration of heat-production elements on the nearside of the Moon.
  • Aina Oura, Kasaba Yasumasa, Rina Noguchi, Atsushi Kumamoto, Ken Ishiyama, Tomohiro Usui, Fuminori Tsuchiya, Chihiro Uemura, Tomoki Kimura
    Icarus 380 2022年7月1日  
    Chryse and Acidalia Planitiae (CAP) are known as one of the areas which have abundant sites of recurring slope lineae (RSL) on Mars. We present a radar survey of shallow subsurface structures across the CAP regions using the Mars SHAllow RADar sounder (SHARAD) onboard the Mars Reconnaissance Orbiter (MRO). A total of 25 subsurface reflectors were identified. The detected reflectors do not constitute apparent subsurface structures larger than 30 km. Because those have no counterparts in nearby tracks, we could not suggest that those are real subsurface structures. This study suggests that the CAP region does not have special wide-spread subsurface features which could be linked to the RSL sites.
  • 矢田 達, 安部 正真, 岡田 達明, 中藤 亜衣子, 与賀田 佳澄, 宮﨑 明子, 西村 征洋, 坂本 佳奈子, 畠田 健太朗, 熊谷 和也, 古屋 静萌, 岩前 絢子, 吉武 美和, 人見 勇矢, 副島 広道, 長島 加奈, 金丸 礼, 山本 大貴, 林 佑, 深井 稜汰, 菅原 春菜, 鈴木 志野, 橘 省吾, 臼井 寛裕, 圦本 尚義, 藤本 正樹, 澤田 弘崇, 岡崎 隆司, 高野 淑識, 三浦 弥生, 矢野 創, Ireland Trevor, 杉田 精司, 長 勇一郎, 湯本 航生, 矢部 佑奈, 森 晶輝, Bibring Jean-Pierre, Pilorget Cedric, Brunetto Rosario, Riu Lucie, Loizeau Damian, Lourit Lionel, Hamm Vincent, 中澤 暁, 田中 智, 佐伯 孝尚, 吉川 真, 渡邊 誠一郎, 津田 雄一
    日本惑星科学会誌遊星人 31(2) 153-164 2022年6月25日  
    2020年12月6日に小惑星探査機「はやぶさ2」はC型小惑星リュウグウ表層物質を収めた再突入カ プセルを地球に帰還させた.回収された再突入カプセルに収められた試料コンテナは,オーストラリア現地でのガス採取を実施した後,JAXA相模原キャンパスの惑星物質試料受入設備に搬入され,チェンバー導入前の部品取り外し・洗浄等のプロセスを経てクリーンチェンバー内で真空中での開封・高純度窒素環境下での帰還試料の取り出し・初期記載が行われた.これらのリュウグウ帰還試料の初期記載の結果,これまでに回収されたどの隕石よりも反射率が低く,全体密度が小さい事が判明した.また,赤外反射スペクトルの吸収特性から水酸基を含む含水鉱物と炭酸塩鉱物,及びCH結合に富む有機物が試料中に含まれることが明らかになった.これらの情報を既知の隕石と比較すると,CIコンドライト隕石に最も似ていると言える.また探査機搭載機器によって得られた可視・近赤外スペクトルと比較した結果,帰還試料はリュウグウ表層全体を代表している事が分かった.取り出された試料の一部は既に初期分析チーム,2次キュレーションチーム,NASAへ配分され,更に国際公募研究による配布が予定されている.本稿では一連の試料取り扱いプロセス・初期記載内容について述べる.
  • Eizo NAKAMURA, Katsura KOBAYASHI, Ryoji TANAKA, Tak KUNIHIRO, Hiroshi KITAGAWA, Christian POTISZIL, Tsutomu OTA, Chie SAKAGUCHI, Masahiro YAMANAKA, Dilan M. RATNAYAKE, Havishk TRIPATHI, Rahul KUMAR, Maya-Liliana AVRAMESCU, Hidehisa TSUCHIDA, Yusuke YACHI, Hitoshi MIURA, Masanao ABE, Ryota FUKAI, Shizuho FURUYA, Kentaro HATAKEDA, Tasuku HAYASHI, Yuya HITOMI, Kazuya KUMAGAI, Akiko MIYAZAKI, Aiko NAKATO, Masahiro NISHIMURA, Tatsuaki OKADA, Hiromichi SOEJIMA, Seiji SUGITA, Ayako SUZUKI, Tomohiro USUI, Toru YADA, Daiki YAMAMOTO, Kasumi YOGATA, Miwa YOSHITAKE, 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, Chisato OKAMOTO, Go ONO, Masanobu OZAKI, Takanao SAIKI, Naoya SAKATANI, Hirotaka SAWADA, Hiroki SENSHU, Yuri SHIMAKI, Kei SHIRAI, 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, Masaki FUJIMOTO, Sei-ichiro WATANABE, Yuichi TSUDA
    Proceedings of the Japan Academy, Series B 98(6) 227-282 2022年6月10日  査読有り
  • Tetsuya Yokoyama, Kazuhide Nagashima, Izumi Nakai, Edward D. Young, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Hiroharu Yui, Ai-Cheng Zhang, Harold C. Connolly, Dante S. Lauretta, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Masahiko Arakawa, Atsushi Fujii, Masahiko Hayakawa, Naoyuki Hirata, Naru Hirata, Rie Honda, Chikatoshi Honda, Satoshi Hosoda, Yu-ichi Iijima, Hitoshi Ikeda, Masateru Ishiguro, Yoshiaki Ishihara, Takahiro Iwata, Kosuke Kawahara, Shota Kikuchi, Kohei Kitazato, Koji Matsumoto, Moe Matsuoka, Tatsuhiro Michikami, Yuya Mimasu, Akira Miura, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hirotaka Sawada, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Yuichi Tsuda, Ryudo Tsukizaki, Koji Wada, Sei-ichiro Watanabe, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Hiromichi Soejima, Ayako Suzuki, Toru Yada, Daiki Yamamoto, Kasumi Yogata, Miwa Yoshitake, Shogo Tachibana, Hisayoshi Yurimoto
    Science 379(6634) eabn7850 2022年6月9日  査読有り
    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.
  • Satoshi Sasaki, Akihiko Yamagishi, Yoshitaka Yoshimura, Keigo Enya, Atsuo Miyakawa, Sosuke Ohno, Kazuhisa Fujita, Tomohiro Usui, Sanjay S Limaye
    Canadian journal of microbiology 68(6) 413-425 2022年6月  
    Much of the information about the size and shape of aerosols forming haze and the cloud layer of Venus is obtained from indirect inferences from nephelometers on probes and from the analysis of the variation of polarization with the phase angle and the glory feature from images of Venus. The microscopic imaging of Venus' aerosols has recently been advocated. Direct measurements from a fluorescence microscope can provide information on the morphology, density, and biochemical characteristics of the particles; thus, fluorescence microscopy is attractive for in situ particle characterization of the Venus cloud layer. Fluorescence imaging of Venus cloud particles presents several challenges owing to the sulfuric acid composition and corrosive effects. In this article, we identify the challenges and describe our approach to overcoming them for a fluorescence microscope based on an in situ biochemical and physical characterization instrument for use in the clouds of Venus from a suitable aerial platform. We report that pH adjustment using alkali was effective for obtaining fluorescence images and that fluorescence attenuation was observed after the adjustment, even when the acidophile suspension in concentrated sulfuric acid was used as a sample.
  • Toru Yada, Masanao Abe, Tatsuaki Okada, Aiko Nakato, Kasumi Yogata, Akiko Miyazaki, Kentaro Hatakeda, Kazuya Kumagai, Masahiro Nishimura, Yuya Hitomi, Hiromichi Soejima, Miwa Yoshitake, Ayako Iwamae, Shizuho Furuya, Masayuki Uesugi, Yuzuru Karouji, Tomohiro Usui, Tasuku Hayashi, Daiki Yamamoto, Ryota Fukai, Seiji Sugita, Yuichiro Cho, Koki Yumoto, Yuna Yabe, Jean-Pierre Bibring, Cedric Pilorget, Vincent Hamm, Rosario Brunetto, Lucie Riu, Lionel Lourit, Damien Loizeau, Guillaume Lequertier, Aurelie Moussi-Soffys, Shogo Tachibana, Hirotaka Sawada, Ryuji Okazaki, Yoshinori Takano, Kanako Sakamoto, Yayoi N. Miura, Hajime Yano, Trevor R. Ireland, Tetsuya Yamada, Masaki Fujimoto, Kohei Kitazato, Noriyuki Namiki, Masahiko Arakawa, Naru Hirata, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Hikaru Yabuta, Hiroshi Naraoka, Motoo Ito, Eizo Nakamura, Kentaro Uesugi, Katsura Kobayashi, Tatsuhiro Michikami, Hiroshi Kikuchi, Naoyuki Hirata, Yoshiaki Ishihara, Koji Matsumoto, Hirotomo Noda, Rina Noguchi, Yuri Shimaki, Kei Shirai, Kazunori Ogawa, Koji Wada, Hiroki Senshu, Yukio Yamamoto, Tomokatsu Morota, Rie Honda, Chikatoshi Honda, Yasuhiro Yokota, Moe Matsuoka, Naoya Sakatani, Eri Tatsumi, Akira Miura, Manabu Yamada, Atsushi Fujii, Chikako Hirose, Satoshi Hosoda, Hitoshi Ikeda, Takahiro Iwata, Shota Kikuchi, Yuya Mimasu, Osamu Mori, Naoko Ogawa, Go Ono, Takanobu Shimada, Stefania Soldini, Tadateru Takahashi, Yuto Takei, Hiroshi Takeuchi, Ryudo Tsukizaki, Kent Yoshikawa, Fuyuto Terui, Satoru Nakazawa, Satoshi Tanaka, Takanao Saiki, Makoto Yoshikawa, Sei-ichiro Watanabe, Yuichi Tsuda
    Nature Astronomy 6(2) 214-220 2022年2月  
    Abstract C-type asteroids1 are considered to be primitive small Solar System bodies enriched in water and organics, providing clues to the origin and evolution of the Solar System and the building blocks of life. C-type asteroid 162173 Ryugu has been characterized by remote sensing2–7 and on-asteroid measurements8,9 with Hayabusa2 (ref. 10). However, the ground truth provided by laboratory analysis of returned samples is invaluable to determine the fine properties of asteroids and other planetary bodies. We report preliminary results of analyses on returned samples from Ryugu of the particle size distribution, density and porosity, spectral properties and textural properties, and the results of a search for Ca–Al-rich inclusions (CAIs) and chondrules. The bulk sample mainly consists of rugged and smooth particles of millimetre to submillimetre size, confirming that the physical and chemical properties were not altered during the return from the asteroid. The power index of its size distribution is shallower than that of the surface boulder observed on Ryugu11, indicating differences in the returned Ryugu samples. The average of the estimated bulk densities of Ryugu sample particles is 1,282 ± 231 kg m−3, which is lower than that of meteorites12, suggesting a high microporosity down to the millimetre scale, extending centimetre-scale estimates from thermal measurements5,9. The extremely dark optical to near-infrared reflectance and spectral profile with weak absorptions at 2.7 and 3.4 μm imply a carbonaceous composition with indigenous aqueous alteration, matching the global average of Ryugu3,4 and confirming that the sample is representative of the asteroid. Together with the absence of submillimetre CAIs and chondrules, these features indicate that Ryugu is most similar to CI chondrites but has lower albedo, higher porosity and more fragile characteristics.
  • Satoshi Sasaki, Akihiko Yamagishi, Yoshitaka Yoshimura, Keigo Enya, Atsuo Miyakawa, Sosuke Ohno, Kazuhisa Fujita, Tomohiro Usui, Sanjay S. Limaye
    Canadian Journal of Microbiology 68(6) 413-425 2022年  
    Much of the information about the size and shape of aerosols forming haze and the cloud layer of Venus is obtained from indirect inferences from nephelometers on probes and from the analysis of the variation of polarization with the phase angle and the glory feature from images of Venus. The microscopic imaging of Venus’ aerosols has recently been advocated. Direct measurements from a fluorescence microscope can provide information on the morphology, density, and biochemical characteristics of the particles; thus, fluorescence microscopy is attractive for in situ particle characterization of the Venus cloud layer. Fluorescence imaging of Venus cloud particles presents several challenges owing to the sulfuric acid composition and corrosive effects. In this article, we identify the challenges and describe our approach to overcoming them for a fluorescence microscope based on an in situ biochemical and physical characterization instrument for use in the clouds of Venus from a suitable aerial platform. We report that pH adjustment using alkali was effective for obtaining fluorescence images and that fluorescence attenuation was observed after the adjustment, even when the acidophile suspension in concentrated sulfuric acid was used as a sample.
  • Asobo Nkengmatia Elvis Asaah, Tetsuya Yokoyama, Hikaru Iwamori, Festus Tongwa Aka, Jules Tamen, Takeshi Kuritani, Tomohiro Usui, Takeshi Hasegawa, Eric Martial Fozing
    Geochemistry 125865-125865 2022年1月  
  • Masashi Shidare, Ryoichi Nakada, Tomohiro Usui, Minato Tobita, Kenji Shimizu, Yoshio Takahashi, Tetsuya Yokoyama
    Geochimica et Cosmochimica Acta 313 85-98 2021年11月15日  
    The surface of Mars has experienced progressive oxidation, resulting in the formation of sulfate minerals as evidenced from surface exploration missions. However, no clear evidence for the presence of sulfate minerals has been reported within Martian meteorites. This study examined sulfur speciation in impact glasses of three basaltic shergottites, Elephant Moraine (EETA) 79001, Larkman Nunatak (LAR) 06319, and Dhofar 019, using X-ray absorption near-edge structure (XANES) spectroscopy. The measured XANES spectra were classified into four types: (1) sulfide, (2) highly reduced sulfide glass (∼IW+1), (3) mixture of sulfide and sulfate, and (4) sulfate. The sulfate spectra observed from EETA79001 and LAR 06319 were mixed with sulfide from the reduced igneous host rock as impact glasses were formed by shock on the surface of Mars, both sulfide and sulfate would have possibly originated on Mars. Besides, highly reduced sulfide present in the same impact glasses is inconsistent with secondary alteration on the oxic Earth's environment. In contrast to EETA79001 and LAR 06319, all of the XANES spectra from Dhofar 019 showed the only sulfate, whose origin is most likely from terrestrial alteration. Combining with the geochemical signatures of volatile elements (e.g., D/H, C, and halogens) in impact glasses of EETA79001 and LAR 06319, we propose two possible scenarios for the formation of sulfate species to the shergottite host-rocks: (i) oxidation of sulfide minerals by subsurface oxic water in Mars, or (ii) precipitation of sulfate mineral derived from Martian subsurface water. The difference between the two models is the source of S(VI) species, whether it originated from (i) magmatic sulfide in shergottite or (ii) sulfate ion in the subsurface water/ice. Both models indicate that the ancient (∼4 Ga) water reservoir might have already been oxic, and it requires post-magmatic water–rock interaction that formed sulfate minerals whose oxidized signatures were incorporated into impact glass.
  • Fumihiro Matsu'ura, Ryoichi Nakada, Tomohiro Usui, Yusuke Sawaki, Yuichiro Ueno, Iori Kajitani, Masafumi Saitoh
    GEOCHIMICA ET COSMOCHIMICA ACTA 306 20-43 2021年8月  
    The Ediacaran period was characterized by numerous events, including the emergence of large multi-cellular metazoans and surface environmental perturbations. This period was also characterized by an increase in atmospheric oxygen concentrations that was critical for the evolution of life. Oceanic sulfate concentrations varied in association with atmospheric oxygen concentrations, which have been constrained by sulfur isotopic compositions of sedimentary sulfates and pyrite, and sulfur concentrations of pyrite and carbonate associated sulfate (CAS). However, other parameters such as sedimentation rate or iron availability have a strong impact on the abundance and isotopic composition of pyrite. In addition, recent studies have demonstrated that some Phanerozoic limestones include a mix of various carbonate minerals, the compositions and diagenetic histories of which differ at the mu m scale. Thus, the mu m scale description of sulfur species is necessary to accurately extract information preserved in carbonate rocks. In this study, we investigated the speciation and concentrations of sulfur in the matrix of the Ediacaran Doushantuo and Dengying limestones exposed in South China using mu-X-ray fluorescence (XRF) mapping and S K-edge X-ray absorption near edge structure (XANES) analyses. In addition to pyrite, the XANES spectra of the Doushantuo limestone indicate that sulfur occurs as CAS, while the Dengying limestone contains CAS and abundant organic sulfur. Pyrite oxidation and re-mineralization of organic sulfur had little influence on CAS content in the samples, whereas sparitization produced decreases in CAS and organic sulfur concentrations. The CAS content of the Dengying sparite was lower than that of the Dengying micrite, indicating that the CAS content decreased even during marine diagenesis. Thus, the micrite is more appropriate for extracting paleo-oceanic information. On the other hand, variations in the CAS concentrations of the limestone matrix in the Dengying Formation were larger than those in the Doushantuo Formation, regardless of grain size. The large variations in the Dengying limestone resulted from local alkalinity fluctuations caused by temporal changes in microbial activity within microbial mats. Existence of abundant organic sulfur in the Dengying limestones has another implication to ancient sedimentary environment. The low pyrite content of the Dengying limestone is likely due to a deficient supply of reactive iron to the sediment-water interface, because the supply of organic matter was likely sufficient. (C) 2021 Elsevier Ltd. All rights reserved.
  • 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
    EARTH PLANETS AND SPACE 73(1) 2021年6月  
    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, Ti, and Zn 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, geochemical data including the nature of organic matter as well as bulk H and N 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 Mn-53-Cr-53 and Rb-87-Sr-87 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 endogenous Phobos materials in curation procedures at JAXA before they are processed for further analyses.
  • Charles Edwards, Vlada Stamenkovic, Penelope Boston, Kennda Lynch, Jesse Tarnas, Barbara Sherwood-Lollar, Sushil Atreya, Alexis Templeton, Anthony Freeman, Woodward Fischer, Tilman Spohn, Chris Webster, Alberto G. Fairén, John (Jack) Mustard, Michael Mischna, Tullis C. Onstott, Magdalena Rose Osburn, Thomas Kieft, Robert E. Grimm, William B. Brinckerhoff, Sarah Johnson, Luther Beegle, James Head, Albert Haldemann, Charles Cockell, John Hernlund, Brian Wilcox, David Paige, Giuseppe Etiope, Daniel Glavin, Maria-Paz Zorzano, Yasuhito Sekine, Stalport Fabien, Joseph Kirschvink, Cara Magnabosco, Roberto Orosei, Matthias Grott, John D. Rummel, Atsuko Kobayashi, Fumio Inagaki, Janice Bishop, Vincent Chevrier, Mary Sue Bell, Beth N. Orcutt, Jennifer McIntosh, Katarina Miljkovic, Doris Breuer, Tomohiro Usui, Kris Zacny, Essam Heggy, Edgard G. Rivera-Valentín, Nathan J. Barba, Ryan Woolley, Oliver Warr, Mike Malaska, Jennifer G. Blank, Donald F. Ruffatto, Haley M. Sapers, Larry H. Matthies, Lewis Ward, Svetlana Shkolyar, Cedric Schmelzbach, Travis S. J. Gabriel, Ceth Parker, Hermes Hernan Bolivar-Torres, Bernadett Pál, Dirk Schulze-Makuch, Jorge Andres Torres Celis, Akos Kereszturi, J. Andy Spry, Kyle Uckert, Marc A. Hesse, Rachel Harris, A.-C. Plesa, Renyu Hu, Ali-akbar Agha-mohammadi, Brian D. Wade, Snehamoy Chatterjee, Patrick McGarey, Heather Valeah Graham, Shino Suzuki, Matt Schrenk, Kristopher Sherrill, Scott Howe, Raju Manthena, Mariko Burgin, Kalind Carpenter, Louis Giersch, Velibor Cormarkovic, Nigel Smith, Jeffrey J. McDonnell, Joseph Michalski, Devanshu Jha, Morgan L. Cable, Elodie Gloesener, Varun Paul, Stewart Gault, Sharon Kedar, Eloise Marteau, Orkun Temel, Seth Krieger, Ryan Timoney
    Bulletin of the AAS 53(4) 2021年3月18日  
  • Hirotaka Sawada, Hiroki Kato, Yasutaka Satou, Kent Yoshikawa, Tomohiro Usui, Haruna Sugahara, Amiko Takano, Fuminobu Sakamoto, Mikio Miyaoka, Takeshi Kuratomi
    IEEE Aerospace Conference Proceedings 2021-March 2021年3月6日  
    The Martian Moons Exploration (MMX) mission of the Japan Aerospace Exploration Agency (JAXA) is scheduled to launch in 2024 and aims to be the world's first mission to return a sample from Phobos. For this, JAXA is developing the MMX sampler. There is a special interest in developing the corer shooting mechanism (C-Sampler) to acquire regolith, a robotic arm to position the core sampler and transfer the acquired regolith, and a sample transfer mechanism to move the regolith to a sample return capsule. This paper reports the system design of the MMX Sampler as well as the results of the tests for the corer sampling mechanism and the regolith conditions needed for effective penetration.
  • Ryoichi Nakada, Gaku Tanabe, Iori Kajitani, Tomohiro Usui, Masashi Shidare, Tetsuya Yokoyama
    Minerals 11(2) 176-176 2021年2月8日  
  • Makoto Yoshikawa, Yuichi Tsuda, Satoru Nakazawa, Satoshi Tanaka, Tomohiro Usui, Elizabeth Tasker, Shogo Tachibana, Sei Ichiro Watanabe
    Proceedings of the International Astronautical Congress, IAC A3 2021年  
    Hayabusa2 is the second asteroid sample return mission in the world following Hayabusa. The target asteroid was (162173) Ryugu, a C-Type near-Earth asteroid. The principal science purpose of the mission is to study the organic matter and water in the early stages of the Solar System, with the aim to understand the origin of the Earth s water and that of the substances that began life, as well as the origin and evolution of Solar System bodies. The mission successfully returned samples from Ryugu and collected a large amount of data on the asteroid through the onboard instruments, rovers, and lander. The mission completed several challenges such as two touchdowns, an impact experiment, and artificial satellite experiments. All of these challenges were important from the scientific point of view. The results revealed a range of the physical properties of Ryugu. With the samples of Ryugu now back on Earth, the sample analysis is currently underway to understand the materials from the early era of our Solar System. In addition to the scientific research, the mission also focused on outreach. We carried out a number of special campaigns, such as observations of the asteroid and spacecraft from Earth and an art contest, many talk events, web and twitter releases among other activities. We tried to inform people about our mission in real time and also tried to publish information both in Japanese and English simultaneously. Through these activities, we think we were able to make people feel connected with the Hayabusa2 mission and we hope that many more people have become interested in space activities. In this paper, we summarize the results of science and outreach for the Hayabusa2 mission.
  • Hiroki Suga, Keika Suzuki, Tomohiro Usui, Akira Yamaguchi, Oki Sekizawa, Kiyofumi Nitta, Yasuo Takeichi, Takuji Ohigashi, Yoshio Takahashi
    Minerals 11(5) 2021年  
    Iddingsite in Martian nakhlites contains various secondary minerals that reflect water– rock interaction on Mars. However, the formation processes of secondary Fe minerals in iddingsite are unclear because they include carbonates precipitated under reductive and alkaline conditions and sulfates that are generally precipitated under oxidative and acidic conditions. Mineral types cannot coexist under equilibrium. Herein, we characterize the carbonate phase of meteorite Yamato 000593 as siderite and Mn-bearing siderite via field-emission electron probe microanalyzer (FE-EPMA). Then, we examined the distribution and speciation of trace Cr and S within the carbonates through synchrotron micro-focused X-ray fluorescence-X-ray absorption fine structure and scanning transmission X-ray microscopy (μ-XRF-XAFS/STXM) analysis to estimate the transition history of Eh-pH conditions during siderite formation to explain the coexistence of carbonate and sulfate phases in the nakhlitse vein. Specifically, the distribution and speciation of S in the mesostasis and carbonate phases and the heterogeneous distribution of Mn-FeCO3 incorporating Cr(III) in the carbonate constrain the Eh-pH condition. The conditions and transition of the fluid chemistry determined herein based on speciation of various elements provide a new constraint on the physicochemical condition of the water that altered the nakhlite body during the Amazonian epoch.
  • H. Kurokawa, B. L. Ehlmann, M. C. De Sanctis, M. G. A. Lapôtre, T. Usui, N. T. Stein, T. H. Prettyman, A. Raponi, M. Ciarniello
    Journal of Geophysical Research: Planets 125(12) 2020年12月  
  • Ryoichi Nakada, Tomohiro Usui, Masashi Ushioda, Yoshio Takahashi
    American Mineralogist 105(11) 1695-1703 2020年11月1日  
  • Rina Noguchi, Ken Ishiyama, Atsushi Kumamoto, Chihiro Uemura, Yasumasa Kasaba, Tomohiro Usui, Aina Oura, Daigo Shoji
    GEOPHYSICAL RESEARCH LETTERS 47(16) 2020年8月  
    We surveyed the subsurface structure in eastern Coprates and Capri Chasmata in the equatorial region using high-resolution visible images, digital terrain models, and radar sounding data. We identified subsurface reflectors in four areas of the chasmata. At the stratigraphic exposure on the chasmata walls, the corresponding depth of the reflector is similar to 60 m. The bulk dielectric constants of the layers above the reflectors are calculated as 3.4-4.0, suggesting a rock-air mixture with similar to 39.3% and 46.1% porosity or a rock-air-ice mixture with <21.2% water ice fraction. This high porosity corresponds to nonwelded and unconsolidated sediments emplaced by aeolian, fluvial, and volcanic activities. If water ice actually exists, further studies and discussions are required for the mechanism to maintain it within low latitudes.
  • Mizuho Koike, Ryoichi Nakada, Iori Kajitani, Tomohiro Usui, Yusuke Tamenori, Haruna Sugahara, Atsuko Kobayashi
    NATURE COMMUNICATIONS 11(1) 2020年4月  
    Understanding the origin of organic material on Mars is a major issue in modern planetary science. Recent robotic exploration of Martian sedimentary rocks and laboratory analyses of Martian meteorites have both reported plausible indigenous organic components. However, little is known about their origin, evolution, and preservation. Here we report that 4-billion-year-old (Ga) carbonates in Martian meteorite, Allan Hills 84001, preserve indigenous nitrogen(N)-bearing organics by developing a new technique for high-spatial resolution in situ N-chemical speciation. The organic materials were synthesized locally and/or delivered meteoritically on Mars during Noachian age. The carbonates, alteration minerals from the Martian near-surface aqueous fluid, trapped and kept the organic materials intact over long geological times. This presence of N-bearing compounds requires abiotic or possibly biotic N-fixation and ammonia storage, suggesting that early Mars had a less oxidizing environment than today. Mars has long been thought to contain organic compounds, but the origins and plausibility are debated. Here the authors employ a new technique to assess organic nitrogen compounds in a Martian meteorite, concluding that these compounds are indeed likely to originate from the Red Planet.
  • 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) 2020年4月  
    Phobos and Deimos occupy unique positions both scientifically and programmatically on the road to the exploration of the solar system. Japan Aerospace Exploration Agency (JAXA) plans a Phobos sample return mission (MMX: Martian Moons eXploration). The MMX spacecraft is scheduled to be launched in 2024, orbit both Phobos and Deimos (multiple flybys), and retrieve and return >10 g of Phobos regolith back to Earth in 2029. The Phobos regolith represents a mixture of endogenous Phobos building blocks and exogenous materials that contain solar system projectiles (e.g., interplanetary dust particles and coarser materials) and ejecta from Mars and Deimos. Under the condition that the representativeness of the sampling site(s) is guaranteed by remote sensing observations in the geologic context of Phobos, laboratory analysis (e.g., mineralogy, bulk composition, O-Cr-Ti isotopic systematics, and radiometric dating) of the returned sample will provide crucial information about the moon's origin: capture of an asteroid or in-situ formation by a giant impact. If Phobos proves to be a captured object, isotopic compositions of volatile elements (e.g., D/H, C-13/C-12, N-15/N-14) in inorganic and organic materials will shed light on both organic-mineral-water/ice interactions in a primitive rocky body originally formed in the outer solar system and the delivery process of water and organics into the inner rocky planets.
  • Ryota Moriwaki, Tomohiro Usui, Minato Tobita, Tetsuya Yokoyama
    GEOCHIMICA ET COSMOCHIMICA ACTA 274 157-171 2020年4月  査読有り
    Radiogenic isotopic compositions of shergottite meteorites suggest that early planetary differentiation processes, which are related to the crystallization of the Martian Magma Ocean (MMO), resulted in the geochemically heterogeneous Martian mantle. In order to understand the early geochemical evolution of Mars, we investigated the Pb isotope systematics in the depleted Martian mantle on the basis of the analyses of two geochemically depleted shergottites, Dar al Gani (DaG) 476 and Yamato 980459 (Y-980459). Their initial Pb isotopic compositions were estimated from geochemical analyses of highly leached acid residues and age-correction calculations using reference crystallization ages. This yielded mu-values (U-238/Pb-204) for the DaG 476 and Y-980459 source reservoirs of 2.33 +/- 0.07 and 2.32 +/- 0.06, respectively. These mu-values are distinct from those of other depleted shergottite source reservoirs (e.g., 1.4 +/- 0.1 for the Tissint meteorite) and show a negative correlation with corresponding Sm-147/Nd-144, Lu-176/Hf-177, epsilon W-182, and epsilon Nd-142 compositions. Such correlations between long- and short-lived isotopic signatures suggest that a geochemically heterogeneous depleted shergottite source mantle was formed on the early Mars. This geochemical heterogeneity would have been formed by variable mixing of depleted and enriched end-member components that originally formed by fractional crystallization in the MMO. Local remelting in the geochemically depleted Martian mantle after the crystallization of the MMO is another possible explanation for the formation of a geochemically heterogeneous depleted shergottite source mantle. (C) 2020 Elsevier Ltd. All rights reserved.
  • Ramses M. Ramirez, Robert A. Craddock, Tomohiro Usui
    JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS 125(3) 2020年3月  
    The debate over the early Martian climate is among the most intriguing in planetary science. Although the geologic evidence generally supports a warmer and wetter climate, climate models have had difficulty simulating such a scenario, leading some to suggest that the observed fluvial geology (e.g., valley networks, modified landscapes) on the Martian surface could have formed in a cold climate instead. However, as we have originally predicted using a single-column radiative-convective climate model (Ramirez, Kopparapu, Zugger, et al., 2014, https://doi.org/10.1038/ngeo2000), warming from CO2-H-2 collision-induced absorption on a volcanically active early Mars could have raised mean surface temperatures above the freezing point, with later calculations showing that this is achievable with hydrogen concentrations as low as similar to 1%. Nevertheless, these predictions should be tested against more complex models. Here we use an advanced energy balance model that includes a northern lowlands ocean to show that mean surface temperatures near or slightly above the freezing point of water were necessary to carve the valley networks. Our scenario is consistent with a relatively large ocean as has been suggested. Valley network distributions would have been global prior to subsequent removal processes. At lower mean surface temperatures and smaller ocean sizes, precipitation and surface erosion efficiency diminish. The warm period may have been approximately <10(7) years, perhaps suggesting that episodic warming mechanisms were not needed. Atmospheric collapse and permanently glaciated conditions occur once surface ice coverage exceeds a threshold depending on collision-induced absorption assumptions. Our results support an early warm and semiarid climate consistent with many geologic observations.Plain Language SummaryMars today is a dry and cold planet that looks quite "Moon-like." However, ancient landscapes on Mars depict a world that may have been much more Earth-like billions of years ago. The surface is filled with ancient riverbeds, deltas, and even features that look a lot like ancient ocean shorelines. Some scientists think that such features suggest a warmer and wetter early planet whereas others believe that these features had formed when the planet was not too different from today. Here we test the idea that a warm early Mars could have had a large northern ocean sustained by a thick carbon dioxide and hydrogen atmosphere. We first confirm previous studies that showed that such an atmosphere could have made Mars warm. We then demonstrate that a relatively large ocean would have been required to form the water features we see on the ancient surface. It may have taken as little as 10 million years or less to form them. In contrast, cold and icy climates, even if they were sporadically warmed from time to time, may not have produced enough precipitation to form these features. We confirm that rain would have been the dominant precipitation on a warm early Mars.
  • Yasuhiro Kawakatsu, Kiyoshi Kuramoto, Tomohiro Usui, Hitoshi Ikeda, Kent Yoshikawa, Hirotaka Sawada, Naoya Ozaki, Takane Imada, Hisashi Otake, Kenichiro Maki, Masatsugu Otsuki, Robert Muller, Kris Zacny, Yasutaka Satoh, Stephane Mary, Markus Grebenstein, Ayumu Tokaji, Liang Yuying, Ferran Gonzalez Franquesa, Nishanth Pushparaj, Takuya Chikazawa
    Proceedings of the International Astronautical Congress, IAC 2020-October 2020年  
    Martian Moons eXploration (MMX) is a mission to Martian moons under development in JAXA with international partners to be launched in 2024. This paper introduces the system definition and the latest status of MMX program. “How was water delivered to rocky planets and enabled the habitability of the solar system?” This is the key question to which MMX is going to answer in the context of our minor body exploration strategy preceded by Hayabusa and Hayabusa2. Solar system formation theories suggest that small bodies as comets and asteroids were delivery capsules of water, volatiles, organic compounds etc. from outside of the snow line to entitle the rocky planet region to be habitable. Mars was at the gateway position to witness the process, which naturally leads us to explore two Martian moons, Phobos and Deimos, to answer to the key question. The goal of MMX is to reveal the origin of the Martian moons, and then to make a progress in our understanding of planetary system formation and of primordial material transport around the border between the inner- and the outer-part of the early solar system. The mission is to survey two Martian moons, and return samples from one of them, Phobos. In view of the launch in 2024, the phase-A study was completed in February, 2020. The mission definition, mission scenario, system definition, critical technologies and programmatic framework are introduced int this paper.
  • Ryuki Hyodo, Kosuke Kurosawa, Hidenori Genda, Tomohiro Usui, Kazuhisa Fujita
    SCIENTIFIC REPORTS 9 2019年12月  
    Throughout the history of the solar system, Mars has experienced continuous asteroidal impacts. These impacts have produced impact-generated Mars ejecta, and a fraction of this debris is delivered to Earth as Martian meteorites. Another fraction of the ejecta is delivered to the moons of Mars, Phobos and Deimos. Here, we studied the amount and condition of recent delivery of impact ejecta from Mars to its moons. Using state-of-the-art numerical approaches, we report, for the first time, that materials delivered from Mars to its moons are physically and chemically different from the Martian meteorites, which are all igneous rocks with a limited range of ages. We show that Mars ejecta mixed in the regolith of its moons potentially covers all its geological eras and consists of all types of rocks, from sedimentary to igneous. A Martian moons sample-return mission will bring such materials back to Earth, and the samples will provide a wealth of "time-resolved" geochemical information about the evolution of Martian surface environments.
  • David J. Lawrence, Patrick N. Peplowski, Andrew W. Beck, Morgan T. Burks, Nancy Chabot, Michael J. Cully, Richard C. Elphic, Carolyn M. Ernst, Samuel Fix, John O. Goldsten, Erin M. Hoffer, Hiroki Kusano, Scott L. Murchie, Brian C. Schratz, Tomohiro Usui, Zachary W. Yokley
    EARTH AND SPACE SCIENCE 6(12) 2605-2623 2019年12月  
    The Mars-moon Exploration with GAmma rays and NEutrons (MEGANE) investigation will use gamma-ray and neutron spectroscopy to measure the elemental composition of Mars' moon Phobos. MEGANE is part of the Japanese Martian Moons eXploration (MMX) mission that will make comprehensive remote sensing measurements of both of Mars' moons Phobos and Deimos. MMX will also return to Earth regolith samples of Phobos. The science goals of the MEGANE investigation mirror those of the MMX mission. MEGANE will use elemental composition measurements to determine if Phobos is a captured asteroid or the end result of a giant impact event on Mars, study Phobos surface processes, provide reconnaissance to support the sample site selection, and supply compositional context for the returned samples. To accomplish its measurements, MEGANE will use a high-purity Ge gamma-ray spectrometer (GRS), and a neutron spectrometer (NS) that consists of two He-3 gas proportional neutron sensors. The GRS derives heritage from similar instruments from NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission and the Psyche mission that is currently in development; the NS is based on similar instruments used for NASA's Lunar Prospector and Psyche missions.
  • Saya Kagami, Makiko K. Haba, Tetsuya Yokoyama, Tomohiro Usui, Richard C. Greenwood
    METEORITICS & PLANETARY SCIENCE 54(11) 2710-2728 2019年11月  
    We report the results of a detailed study of the basaltic eucrite Northwest Africa (NWA) 7188, including its mineralogical and bulk geochemical characteristics, oxygen isotopic composition, and Sm-147,Sm-146-Nd-143,Nd-142 mineral isochron ages. The texture and chemical composition of pyroxene and plagioclase demonstrate that NWA 7188 is a monomict eucrite with a metamorphic grade of type 4. The oxygen isotopic composition and the Fe/Mn ratios of pyroxene confirmed that NWA 7188 belongs to the howardite-eucrite-diogenite meteorite suite, generally considered to originate from asteroid 4 Vesta. Whole-rock TiO2, La, and Hf concentrations and a CI chondrite-normalized rare earth element pattern are in good agreement with those of representative Stannern-group eucrites. The Sm-147,Sm-146-Nd-143,Nd-142 isochrons for NWA 7188 yielded ages of 4582 +/- 190 and 4554 +17/-19 Ma, respectively. The closure temperature of the Sm-Nd system for different fractions of NWA 7188 was estimated to be >865 degrees C, suggesting that the Sm-Nd decay system has either been resistant to reheating at similar to 800 degrees C during the global metamorphism or only partially reset. Therefore, the Sm-146-Nd-142 age of NWA 7188 corresponds to the period of initial crystallization of basaltic magmas and/or global metamorphism on the parent body, and is unlikely to reflect Sm-Nd disturbance by late reheating and impact events. In either case, NWA 7188 is a rare Stannern-group eucrite that preserves the chronological information regarding the initial crustal evolution of Vesta.

MISC

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  • Ryuki Hyodo, Tomohiro Usui
    SCIENCE 373(6556) 742-742 2021年8月  
  • 臼井寛裕, 菅倉春菜, 倉本圭, 倉本圭, 川勝康弘
    宇宙科学技術連合講演会講演集(CD-ROM) 65th 2021年  
  • 吉村義隆, 山岸明彦, 宮川厚夫, 今井栄一, 佐々木聰, 塩谷圭吾, 三田肇, 小林憲正, 癸生川陽子, 佐藤直人, 佐藤毅彦, 薮田ひかる, 長沼毅, 藤田和央, 臼井寛裕
    日本惑星科学会秋季講演会予稿集(Web) 2020 2020年  
  • 臼井寛裕, 関華奈子, 藤田和央
    日本惑星科学会秋季講演会予稿集(Web) 2020 2020年  
  • 鈴木 慧花, 菅 大暉, 山口 亮, 臼井 寛裕, 新田 清文, 関澤 央輝, 高橋 嘉夫
    日本地球化学会年会要旨集 66 177-177 2019年  
    <p>火星隕石ナクライトにはIddingsiteという変質脈が存在し、この中の変質鉱物には火星での水の痕跡が残されている。しかし、変質鉱物には炭酸塩と硫酸塩(jarositeなど)という異なるEh-pH条件で形成したと考えられる物質が共存しており、火星でのIddingsite形成環境・過程は不明瞭である。また、これらの関係性を正確に議論した研究は今までにほとんどない。本研究ではナクライト隕石Y000593のIddingsiteを対象とし、微量元素とその化学種に着目した分析を行った。従来の隕石分析に用いるSEM・EPMA分析に、放射光をベースとしたX線顕微分析(μ-XRF-XAFS@BL37XU SPring-8とsemi-μ-XRF-XAFS@BL-15A KEK-PF)から得られる知見を組み合わせることで、変質過程の詳細な解明を試みた。</p>

共同研究・競争的資金等の研究課題

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