2022/11/29 更新

写真a

ノグチ リナ
野口 里奈
NOGUCHI Rina
所属
教育研究院 自然科学系 地球・生物科学系列 助教
自然科学研究科 環境科学専攻 助教
理学部 理学科 助教
職名
助教
外部リンク

代表的な業績

    • 【論文】 Crater depth-to-diameter ratios on asteroid 162173 Ryugu  2021年1月

    • 【論文】 Radar Sounding of Subsurface Structure in Eastern Coprates and Capri Chasmata, Mars  2020年8月

    • 【論文】 Detailed topographical, distributional, and material analyses of rootless cones in Myvatn, Iceland  2016年4月

学位

  • 博士(理学) ( 2015年7月   東京大学 )

研究キーワード

  • 火星

  • ルートレスコーン

  • 火山灰

  • 火山地形

  • 火山学

  • 露頭調査

研究分野

  • 自然科学一般 / 宇宙惑星科学  / 惑星科学

  • 自然科学一般 / 固体地球科学  / 火山学

経歴(researchmap)

  • 新潟大学   自然科学系   助教

    2021年4月 - 現在

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  • 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   研究員

    2018年4月 - 2021年3月

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    国名:日本国

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  • 東京工業大学   火山流体研究センター   研究員

    2016年4月 - 2018年3月

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    国名:日本国

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  • 国立研究開発法人産業技術総合研究所   地質調査総合センター   産総研特別研究員

    2015年11月 - 2016年3月

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    国名:日本国

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  • 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   招聘研究職員

    2015年8月 - 2015年10月

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    国名:日本国

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経歴

  • 新潟大学   教育研究院 自然科学系 地球・生物科学系列   助教

    2021年4月 - 現在

  • 新潟大学   理学部 理学科   助教

    2021年4月 - 現在

  • 新潟大学   自然科学研究科 環境科学専攻   助教

    2021年4月 - 現在

学歴

  • 東京大学   大学院理学系研究科   地球惑星科学専攻

    2012年4月 - 2015年7月

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    国名: 日本国

    備考: 博士課程

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  • 東京大学   大学院理学系研究科   地球惑星科学専攻

    2010年4月 - 2012年3月

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    国名: 日本国

    備考: 修士課程

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  • 東海大学   海洋学部   海洋資源学科

    2006年4月 - 2010年3月

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    国名: 日本国

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所属学協会

 

論文

  • Site selection for the Hayabusa2 artificial cratering and subsurface material sampling on Ryugu

    Shota Kikuchi, Sei-ichiro Watanabe, Koji Wada, Takanao Saiki, Hikaru Yabuta, Seiji Sugita, Masanao Abe, Masahiko Arakawa, Yuichiro Cho, Masahiko Hayakawa, Naoyuki Hirata, Naru Hirata, Chikatoshi Honda, Rie Honda, Ko Ishibashi, Yoshiaki Ishihara, Takahiro Iwata, Toshihiko Kadono, Shingo Kameda, Kohei Kitazato, Toru Kouyama, Koji Matsumoto, Moe Matsuoka, Tatsuhiro Michikami, Yuya Mimasu, Akira Miura, Tomokatsu Morota, Tomoki Nakamura, Satoru Nakazawa, Noriyuki Namiki, Rina Noguchi, Kazunori Ogawa, Naoko Ogawa, Tatsuaki Okada, Go Ono, Naoya Sakatani, Hirotaka Sawada, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Shogo Tachibana, Yuto Takei, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Manabu Yamada, Yukio Yamamoto, Yasuhiro Yokota, Kent Yoshikawa, Makoto Yoshikawa, Yuichi Tsuda

    PLANETARY AND SPACE SCIENCE   219   2022年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Hayabusa2 took on the challenge of collecting fresh subsurface samples from asteroid (162173) Ryugu during its second touchdown operation. For this ambitious goal, the spacecraft conducted artificial cratering by using a small carry-on impactor (SCI), leading to the exposure of subsurface materials. The key to mission success lies in the target site selection for the SCI and landing operations, which is the focus of this paper. On the one hand, the science goal of collecting subsurface materials required us to land on one of the areas with a large amount of impact ejecta excavated by SCI, where boulder abundance is not necessarily low. On the other hand, spacecraft safety demanded that we avoid landing on hazardous areas with large boulders. These two conditions often conflicted with each other. In order to resolve this dilemma, we developed a scheme to select a target site that secures the chance of retrieving a significant amount of subsurface samples without posing serious safety risks. Although the basic selection scheme was similar to that for the first touchdown, the second landing site selection involved additional analyses of artificial cratering and subsurface sampling. Consequently, the site selection campaign, including various types of spacecraft operations, contributed to the successful retrieval of Ryugu samples, which presumably contain materials excavated from subsurface layers. The present study provides the framework to access internal asteroid materials, pushing the envelope of space exploration.

    DOI: 10.1016/j.pss.2022.105519

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  • A pristine record of outer Solar System materials from asteroid Ryugu's returned sample

    Motoo Ito, Naotaka Tomioka, Masayuki Uesugi, Akira Yamaguchi, Naoki Shirai, Takuji Ohigashi, Ming-Chang Liu, Richard C. Greenwood, Makoto Kimura, Naoya Imae, Kentaro Uesugi, Aiko Nakato, Kasumi Yogata, Hayato Yuzawa, Yu Kodama, Akira Tsuchiyama, Masahiro Yasutake, Ross Findlay, Ian A. Franchi, James A. Malley, Kaitlyn A. McCain, Nozomi Matsuda, Kevin D. McKeegan, Kaori Hirahara, Akihisa Takeuchi, Shun Sekimoto, Ikuya Sakurai, Ikuo Okada, Yuzuru Karouji, Masahiko Arakawa, Atsushi Fujii, Masaki Fujimoto, 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, Osamu Mori, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hirotaka Sawada, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Ryudo Tsukizaki, Koji Wada, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Ryota Fukai, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Masahiro Nishimura, Hiromichi Soejima, Ayako Iwamae, Daiki Yamamoto, Miwa Yoshitake, Toru Yada, Masanao Abe, Tomohiro Usui, Sei-ichiro Watanabe, Yuichi Tsuda

    NATURE ASTRONOMY   6 ( 10 )   1163 - 1171   2022年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATURE PORTFOLIO  

    Volatile and organic-rich C-type asteroids may have been one of the main sources of Earth's water. Our best insight into their chemistry is currently provided by carbonaceous chondritic meteorites, but the meteorite record is biased: only the strongest types survive atmospheric entry and are then modified by interaction with the terrestrial environment. Here we present the results of a detailed bulk and microanalytical study of pristine Ryugu particles, brought to Earth by the Hayabusa2 spacecraft. Ryugu particles display a close compositional match with the chemically unfractionated, but aqueously altered, CI (Ivuna-type) chondrites, which are widely used as a proxy for the bulk Solar System composition. The sample shows an intricate spatial relationship between aliphatic-rich organics and phyllosilicates and indicates maximum temperatures of -30 degrees C during aqueous alteration. We find that heavy hydrogen and nitrogen abundances are consistent with an outer Solar System origin. Ryugu particles are the most uncontaminated and unfractionated extraterrestrial materials studied so far, and provide the best available match to the bulk Solar System composition.

    DOI: 10.1038/s41550-022-01745-5

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  • Three-axial shape distributions of pebbles, cobbles and boulders smaller than a few meters on asteroid Ryugu

    Tatsuhiro Michikami, Axel Hagermann, Tomokatsu Morota, Yasuhiro Yokota, Seitaro Urakawa, Hiroyuki Okamura, Naoya Tanabe, Koki Yumoto, Tatsuki Ebihara, Yuichiro Cho, Carolyn M. Ernst, Masahiko Hayakawa, Masatoshi Hirabayashi, Naru Hirata, Chikatoshi Honda, Rie Honda, Shingo Kameda, Masanori Kanamaru, Hiroshi Kikuchi, Shota Kikuchi, Toru Kouyama, Moe Matsuoka, Hideaki Miyamoto, Takaaki Noguchi, Rina Noguchi, Kazunori Ogawa, Tatsuaki Okada, Naoya Sakatani, Sho Sasaki, Hirotaka Sawada, Chiho Sugimoto, Hidehiko Suzuki, Satoshi Tanaka, Eri Tatsumi, Akira Tsuchiyama, Yuichi Tsuda, Sei ichiro Watanabe, Manabu Yamada, Makoto Yoshikawa, Kazuo Yoshioka, Seiji Sugita

    Icarus   381   2022年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    Over a broad size range, the shapes of impact fragments from catastrophic disruptions are distributed around the mean axial ratio 2: √2: 1, irrespective of experimental conditions and target materials. Although most blocks on asteroids are likely to be impact fragments, there is not enough quantitative data for reliable statistics on their three-axial lengths and/or ratios because it is difficult to precisely estimate the heights of the blocks. In this study, we evaluate the heights of blocks on asteroid Ryugu by measuring their shadows. The three-axial ratios of ~4100 small blocks with diameters from 5.0 cm to 7.6 m in Ryugu's equatorial region are investigated using eight close-up images of narrower localities taken at altitudes below 500 m, i.e. at <5.4 cm/pixel resolution, obtained immediately before the second touch-down of the Hayabusa2 spacecraft. The purpose of this study is to investigate the block shape distribution, which is important for understanding the geological history of asteroid Ryugu. Specifically, the shape distribution is compared to laboratory impact fragments. Our observations indicate that the shape distributions of blocks smaller than 1 m on Ryugu are consistent with laboratory impact fragment shape distributions, implying that the dominant shape-determining process for blocks on Ryugu was impact fragmentation. Blocks several meters in size in the equatorial region seem to be slightly flatter than the rest, suggesting that some blocks are partly buried in a bed of regolith. In conclusion, the shape distributions of blocks from several-cm to several-m in the equatorial region of asteroid Ryugu suggest that these are mainly fragments originating from the catastrophic disruption of their parent body and/or from a later impact.

    DOI: 10.1016/j.icarus.2022.115007

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  • Search for shallow subsurface structures in Chryse and Acidalia Planitiae on Mars

    Aina Oura, Kasaba Yasumasa, Rina Noguchi, Atsushi Kumamoto, Ken Ishiyama, Tomohiro Usui, Fuminori Tsuchiya, Chihiro Uemura, Tomoki Kimura

    Icarus   380   2022年7月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Wiley  

    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.

    DOI: 10.1016/j.icarus.2022.114991

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  • On the origin and evolution of the asteroid Ryugu: A comprehensive geochemical perspective

    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-PHYSICAL AND BIOLOGICAL SCIENCES   98 ( 6 )   227 - 282   2022年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN ACAD  

    Presented here are the observations and interpretations from a comprehensive analysis of 16 representative particles returned from the C-type asteroid Ryugu by the Hayabusa2 mission. On average Ryugu particles consist of 50% phyllosilicate matrix, 41% porosity and 9% minor phases, including organic matter. The abundances of 70 elements from the particles are in close agreement with those of CI chondrites. Bulk Ryugu particles show higher delta O-18, Delta O-17, and epsilon Cr-54 values than CI chondrites. As such, Ryugu sampled the most primitive and least-thermally processed protosolar nebula reservoirs. Such a finding is consistent with multi-scale H-C-N isotopic compositions that are compatible with an origin for Ryugu organic matter within both the protosolar nebula and the interstellar medium. The analytical data obtained here, suggests that complex soluble organic matter formed during aqueous alteration on the Ryugu progenitor planetesimal (several 10's of km), <2.6 Myr after CAI formation. Subsequently, the Ryugu progenitor planetesimal was fragmented and evolved into the current asteroid Ryugu through sublimation.

    DOI: 10.2183/pjab.98.015

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  • Pebbles and sand on asteroid (162173) Ryugu: In situ observation and particles returned to Earth

    S. Tachibana, H. Sawada, R. Okazaki, Y. Takano, K. Sakamoto, Y. N. Miura, C. Okamoto, H. Yano, S. Yamanouchi, P. Michel, Y. Zhang, S. Schwartz, F. Thuillet, H. Yurimoto, T. Nakamura, T. Noguchi, H. Yabuta, H. Naraoka, A. Tsuchiyama, N. Imae, K. Kurosawa, A. M. Nakamura, K. Ogawa, S. Sugita, T. Morota, R. Honda, S. Kameda, E. Tatsumi, Y. Cho, K. Yoshioka, Y. Yokota, M. Hayakawa, M. Matsuoka, N. Sakatani, M. Yamada, T. Kouyama, H. Suzuki, C. Honda, T. Yoshimitsu, T. Kubota, H. Demura, T. Yada, M. Nishimura, K. Yogata, A. Nakato, M. Yoshitake, A. I. Suzuki, S. Furuya, K. Hatakeda, A. Miyazaki, K. Kumagai, T. Okada, M. Abe, T. Usui, T. R. Ireland, M. Fujimoto, T. Yamada, M. Arakawa, H. C. Connolly, A. Fujii, S. Hasegawa, N. Hirata, N. Hirata, C. Hirose, S. Hosoda, Y. Iijima, H. Ikeda, M. Ishiguro, Y. Ishihara, T. Iwata, S. Kikuchi, K. Kitazato, D. S. Lauretta, G. Libourel, B. Marty, K. Matsumoto, T. Michikami, Y. Mimasu, A. Miura, O. Mori, K. Nakamura-Messenger, N. Namiki, A. N. Nguyen, L. R. Nittler, H. Noda, R. Noguchi, N. Ogawa, G. Ono, M. Ozaki, H. Senshu, T. Shimada, Y. Shimaki, K. Shirai, S. Soldini, T. Takahashi, Y. Takei, H. Takeuchi, R. Tsukizaki, K. Wada, Y. Yamamoto

    Science   375 ( 6584 )   1011 - 1016   2022年3月

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    掲載種別:研究論文(学術雑誌)  

    The Hayabusa2 spacecraft investigated the C-type (carbonaceous) asteroid (162173) Ryugu. The mission performed two landing operations to collect samples of surface and subsurface material, the latter exposed by an artificial impact. We present images of the second touchdown site, finding that ejecta from the impact crater was present at the sample location. Surface pebbles at both landing sites show morphological variations ranging from rugged to smooth, similar to Ryugu’s boulders, and shapes from quasi-spherical to flattened. The samples were returned to Earth on 6 December 2020. We describe the morphology of >5 grams of returned pebbles and sand. Their diverse color, shape, and structure are consistent with the observed materials of Ryugu; we conclude that they are a representative sample of the asteroid.

    DOI: 10.1126/science.abj8624

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  • Preliminary analysis of the Hayabusa2 samples returned from C-type asteroid Ryugu

    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

    Nature Astronomy   6 ( 2 )   214 - 220   2022年2月

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    掲載種別:研究論文(学術雑誌)  

    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.

    DOI: 10.1038/s41550-021-01550-6

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  • Anomalously porous boulders on (162173) Ryugu as primordial materials from its parent body

    N. Sakatani, S. Tanaka, T. Okada, T. Fukuhara, L. Riu, S. Sugita, R. Honda, T. Morota, S. Kameda, Y. Yokota, E. Tatsumi, K. Yumoto, N. Hirata, A. Miura, T. Kouyama, H. Senshu, Y. Shimaki, T. Arai, J. Takita, H. Demura, T. Sekiguchi, T. G. Müller, A. Hagermann, J. Biele, M. Grott, M. Hamm, M. Delbo, W. Neumann, M. Taguchi, Y. Ogawa, T. Matsunaga, T. Wada, S. Hasegawa, J. Helbert, N. Hirata, R. Noguchi, M. Yamada, H. Suzuki, C. Honda, K. Ogawa, M. Hayakawa, K. Yoshioka, M. Matsuoka, Y. Cho, H. Sawada, K. Kitazato, T. Iwata, M. Abe, M. Ohtake, S. Matsuura, K. Matsumoto, H. Noda, Y. Ishihara, K. Yamamoto, A. Higuchi, N. Namiki, G. Ono, T. Saiki, H. Imamura, Y. Takagi, H. Yano, K. Shirai, C. Okamoto, S. Nakazawa, Y. Iijima, M. Arakawa, K. Wada, T. Kadono, K. Ishibashi, F. Terui, S. Kikuchi, T. Yamaguchi, N. Ogawa, Y. Mimasu, K. Yoshikawa, T. Takahashi, Y. Takei, A. Fujii, H. Takeuchi, Y. Yamamoto, C. Hirose, S. Hosoda, O. Mori, T. Shimada, S. Soldini, R. Tsukizaki, M. Ozaki, S. Tachibana, H. Ikeda, M. Ishiguro, H. Yabuta, M. Yoshikawa, S. Watanabe, Y. Tsuda

    Nature Astronomy   5 ( 8 )   766 - 774   2021年8月

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    掲載種別:研究論文(学術雑誌)  

    Planetesimals—the initial stage of the planetary formation process—are considered to be initially very porous aggregates of dusts1,2, and subsequent thermal and compaction processes reduce their porosity3. The Hayabusa2 spacecraft found that boulders on the surface of asteroid (162173) Ryugu have an average porosity of 30–50% (refs. 4–6), higher than meteorites but lower than cometary nuclei7, which are considered to be remnants of the original planetesimals8. Here, using high-resolution thermal and optical imaging of Ryugu’s surface, we discovered, on the floor of fresh small craters (<20 m in diameter), boulders with reflectance (~0.015) lower than the Ryugu average6 and porosity >70%, which is as high as in cometary bodies. The artificial crater formed by Hayabusa2’s impact experiment9 is similar to these craters in size but does not have such high-porosity boulders. Thus, we argue that the observed high porosity is intrinsic and not created by subsequent impact comminution and/or cracking. We propose that these boulders are the least processed material on Ryugu and represent remnants of porous planetesimals that did not undergo a high degree of heating and compaction3. Our multi-instrumental analysis suggests that fragments of the highly porous boulders are mixed within the surface regolith globally, implying that they might be captured within collected samples by touch-down operations10,11.

    DOI: 10.1038/s41550-021-01371-7

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  • Thermally altered subsurface material of asteroid (162173) Ryugu 査読

    K. Kitazato, R. E. Milliken, T. Iwata, M. Abe, M. Ohtake, S. Matsuura, Y. Takagi, T. Nakamura, T. Hiroi, M. Matsuoka, L. Riu, Y. Nakauchi, K. Tsumura, T. Arai, H. Senshu, N. Hirata, M. A. Barucci, R. Brunetto, C. Pilorget, F. Poulet, J.-P. Bibring, D. L. Domingue, F. Vilas, D. Takir, E. Palomba, A. Galiano, D. Perna, T. Osawa, M. Komatsu, A. Nakato, T. Arai, N. Takato, T. Matsunaga, M. Arakawa, T. Saiki, K. Wada, T. Kadono, H. Imamura, H. Yano, K. Shirai, M. Hayakawa, C. Okamoto, H. Sawada, K. Ogawa, Y. Iijima, S. Sugita, R. Honda, T. Morota, S. Kameda, E. Tatsumi, Y. Cho, K. Yoshioka, Y. Yokota, N. Sakatani, M. Yamada, T. Kouyama, H. Suzuki, C. Honda, N. Namiki, T. Mizuno, K. Matsumoto, H. Noda, Y. Ishihara, R. Yamada, K. Yamamoto, F. Yoshida, S. Abe, A. Higuchi, Y. Yamamoto, T. Okada, Y. Shimaki, R. Noguchi, A. Miura, N. Hirata, S. Tachibana, H. Yabuta, M. Ishiguro, H. Ikeda, H. Takeuchi, T. Shimada, O. Mori, S. Hosoda, R. Tsukizaki, S. Soldini, M. Ozaki, F. Terui, N. Ogawa, Y. Mimasu, G. Ono, K. Yoshikawa, C. Hirose, A. Fujii, T. Takahashi, S. Kikuchi, Y. Takei, T. Yamaguchi, S. Nakazawa, S. Tanaka, M. Yoshikawa, S. Watanabe, Y. Tsuda

    Nature Astronomy   5 ( 3 )   246 - 250   2021年3月

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    担当区分:責任著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Science and Business Media LLC  

    Analyses of meteorites and theoretical models indicate that some carbonaceous near-Earth asteroids may have been thermally altered due to radiative heating during close approaches to the Sun1–3. However, the lack of direct measurements on the subsurface doesn’t allow us to distinguish thermal alteration due to radiative heating from parent-body processes. In April 2019, the Hayabusa2 mission successfully completed an artificial impact experiment on the carbonaceous near-Earth asteroid (162173) Ryugu4,5, which provided an opportunity to investigate exposed subsurface material and test potential effects of radiative heating. Here we report observations of Ryugu’s subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. The strength and shape of the OH feature suggests that the subsurface material experienced heating above 300 °C, similar to the surface. In contrast, thermophysical modelling indicates that radiative heating cannot increase the temperature above 200 °C at the estimated excavation depth of 1 m, even at the smallest heliocentric distance possible for Ryugu. This supports the hypothesis that primary thermal alteration occurred on Ryugu’s parent body.

    DOI: 10.1038/s41550-020-01271-2

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  • Imaging the Source Region of the 2015 Phreatic Eruption at Owakudani, Hakone Volcano, Japan, Using High‐Density Audio‐Frequency Magnetotellurics 査読

    K. Seki, W. Kanda, K. Mannen, S. Takakura, T. Koyama, R. Noguchi, Y. Yukutake, M. Ishikawa, M. Fukai, M. Harada, Y. Abe

    Geophysical Research Letters   48 ( 1 )   2021年1月

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    担当区分:責任著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union (AGU)  

    Since phreatic eruptions often occur near the surface, it is important to understand the shallow subsurface structure of a volcano to clarify the eruption mechanism. The 2015 phreatic eruption at Owakudani, Hakone Volcano, Japan, was preceded by localized uplift and intensified steam activity. However, the cause of these events is unknown due to a poor understanding of the shallow subsurface structure. We report on a three-dimensional resistivity structure inferred from dense audio-frequency magnetotelluric surveys conducted in Owakudani that revealed a ∼100-m thick conductive layer at the surface underlain by a resistive section, at the edge of which eruptions craters were located. This conductive layer is estimated to be a low-permeability cap layer, because the inflation source prior to the eruption is located beneath it and the ejecta from the eruption was reported to have originated from a depth of 100 m or less.

    DOI: 10.1029/2020gl091568

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    その他リンク: https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2020GL091568

  • Crater depth-to-diameter ratios on asteroid 162173 Ryugu 査読

    Rina Noguchi, Naoyuki Hirata, Naru Hirata, Yuri Shimaki, Naoki Nishikawa, Sayuri Tanaka, Takaaki Sugiyama, Tomokatsu Morota, Seiji Sugita, Yuichiro Cho, Rie Honda, Shingo Kameda, Eri Tatsumi, Kazuo Yoshioka, Hirotaka Sawada, Yasuhiro Yokota, Naoya Sakatani, Masahiko Hayakawa, Moe Matsuoka, Manabu Yamada, Toru Kouyama, Hidehiko Suzuki, Chikatoshi Honda, Kazunori Ogawa, Masanori Kanamaru, Sei-ichiro Watanabe

    Icarus   354   114016 - 114016   2021年1月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    The near-Earth asteroid 162173 Ryugu, the target of the Hayabusa2 mission, is noted to be a spinning top-shaped rubble-pile. Craters are among the most prominent surface features on Ryugu. Their shapes, particularly their depth-to-diameter ratio (d/D), can provide an important proxy for probing both the internal structure and surface processes of planetary bodies. Here, we report d/D of every impact crater on Ryugu using a shape model derived from stereo-photoclinometry. We found that the average, standard deviation, and observed range of d/D for the entire set of craters are 0.09, 0.02, and 0.03–0.15, respectively. Except for possible pit craters, the maximum d/D of large craters on Ryugu (D > 50 m) is close to 0.13, which is comparable with those of fresh simple craters on rocky asteroids, such as Gaspra and Ida. Conversely, the d/D of small craters (D < 50 m) increases with the crater diameter. This behavior implies that a smaller crater on Ryugu is formed as a shallower crater. As on Itokawa, the surface environment on Ryugu likely inhibits craters becoming deep. This especially affects smaller craters, as their normal small depth decreases in the Ryugu environment and they become still more shallow. As a result, small craters rapidly degrade beyond the point where they can be identified as candidate craters. This is likely responsible for the apparent lack of small craters. The d/D has no reliable relationship with the types of crater classification in Hirata et al. (2020). Examination of latitudinal and longitudinal variation in d/D of craters on Ryugu revealed no statistically significant trends.

    DOI: 10.1016/j.icarus.2020.114016

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  • Hayabusa2 Landing Site Selection: Surface Topography of Ryugu and Touchdown Safety 査読

    Shota Kikuchi, Sei-ichiro Watanabe, Takanao Saiki, Hikaru Yabuta, Seiji Sugita, Tomokatsu Morota, Naru Hirata, Naoyuki Hirata, Tatsuhiro Michikami, Chikatoshi Honda, Yashuhiro Yokota, Rie Honda, Naoya Sakatani, Tatsuaki Okada, Yuri Shimaki, Koji Matsumoto, Rina Noguchi, Yuto Takei, Fuyuto Terui, Naoko Ogawa, Kent Yoshikawa, Go Ono, Yuya Mimasu, Hirotaka Sawada, Hitoshi Ikeda, Chikako Hirose, Tadateru Takahashi, Atsushi Fujii, Tomohiro Yamaguchi, Yoshiaki Ishihara, Tomoki Nakamura, Kohei Kitazato, Koji Wada, Shogo Tachibana, Eri Tatsumi, Moe Matsuoka, Hiroki Senshu, Shingo Kameda, Toru Kouyama, Manabu Yamada, Kei Shirai, Yuichiro Cho, Kazunori Ogawa, Yukio Yamamoto, Akira Miura, Takahiro Iwata, Noriyuki Namiki, Masahiko Hayakawa, Masanao Abe, Satoshi Tanaka, Makoto Yoshikawa, Satoru Nakazawa, Yuichi Tsuda

    Space Science Reviews   216 ( 7 )   2020年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Science and Business Media LLC  

    One of the primary goals of Hayabusa2 is to land on the asteroid Ryugu to collect its surface materials. The key for a successful touchdown is to find a promising landing site that meets both scientific and engineering requirements. Due to the limited availability of pre-arrival information about Ryugu, the landing site selection (LSS) must be conducted based on proximity observations over a limited length of time. In addition, Ryugu was discovered to possess an unexpectedly high abundance of boulders with an absence of wide and flat areas, further complicating the LSS. To resolve these problems, we developed a systematic and stepwise LSS process with a focus on the surface topography of Ryugu and the associated touchdown safety. The proposed LSS scheme consists of two phases: Phase-I LSS, a comprehensive survey of potential landing areas at the 100-m scale based on the global mapping of Ryugu, and Phase-II LSS, a narrowing-down process of the candidate landing sites at the 10-m scale using high-resolution images and a local terrain model. To verify the feasibility of a precision landing at the target site, we also investigated the landing dispersion via a Monte Carlo simulation, which incorporates the effect of the irregular surface gravity field. One of the major characteristics of the Hayabusa2 LSS developed in this study is the iterative feedback between LSS analyses on the ground and actual spacecraft operations near the target asteroid. Using the newly developed method, we chose a landing site with a radius of 3 m, and Hayabusa2 successfully conducted its first touchdown on February 21, 2019. This paper reports the methodology and results of the stepwise iterative LSS for the first Hayabusa2 touchdown. The touchdown operation results reconstructed from flight data are also provided, demonstrating the validity of the adopted LSS strategy.

    DOI: 10.1007/s11214-020-00737-z

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  • Thermophysical properties of the surface of asteroid 162173 Ryugu: Infrared observations and thermal inertia mapping 査読

    Yuri Shimaki, Hiroki Senshu, Naoya Sakatani, Tatsuaki Okada, Tetsuya Fukuhara, Satoshi Tanaka, Makoto Taguchi, Takehiko Arai, Hirohide Demura, Yoshiko Ogawa, Kentaro Suko, Tomohiko Sekiguchi, Toru Kouyama, Sunao Hasegawa, Jun Takita, Tsuneo Matsunaga, Takeshi Imamura, Takehiko Wada, Kohei Kitazato, Naru Hirata, Naoyuki Hirata, Rina Noguchi, Seiji Sugita, Shota Kikuchi, Tomohiro Yamaguchi, Naoko Ogawa, Go Ono, Yuya Mimasu, Kent Yoshikawa, Tadateru Takahashi, Yuto Takei, Atsushi Fujii, Hiroshi Takeuchi, Yukio Yamamoto, Manabu Yamada, Kei Shirai, Yu-ichi Iijima, Kazunori Ogawa, Satoru Nakazawa, Fuyuto Terui, Takanao Saiki, Makoto Yoshikawa, Yuichi Tsuda, Sei-ichiro Watanabe

    Icarus   348   113835 - 113835   2020年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    TIR, the thermal infrared imager on Hayabusa2, acquired high-resolution thermal images of the asteroid 162173 Ryugu for one asteroid rotation period on August 1, 2018 to investigate the thermophysical properties of the asteroid. The surface temperatures of Ryugu suggest that the surface has a low thermal inertia, indicating the presence of porous materials. Thermophysical models that neglect or oversimplify surface roughness cannot reproduce the flat diurnal temperature profiles observed during daytime. We performed numerical simulations of a thermophysical model, including the effects of roughness on the diurnal brightness temperature, the predictions of which successfully reproduced the observed diurnal variation of temperature. The global thermal inertia was obtained with a standard deviation of 225 ± 45 J m s K , which is relatively low but still within the range of the value estimated in our previous study (Okada et al., Nature 579, 518–522, 2020), confirming that the boulders on Ryugu are more porous in nature than typical carbonaceous chondrites. The global surface roughness (the ratio of the variance of the height relative to a local horizontal surface length) was determined as 0.41 ± 0.08, corresponding to a RMS surface slope of 47 ± 5°. We identified a slightly lower roughness distributed along the equatorial ridge, implying a mass movement of boulders from the equatorial ridge to the mid-latitudes. −2 −0.5 −1

    DOI: 10.1016/j.icarus.2020.113835

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  • Radar Sounding of Subsurface Structure in Eastern Coprates and Capri Chasmata, Mars 査読

    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

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union ({AGU})  

    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.

    DOI: 10.1029/2020GL088556

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  • Rotational effect as the possible cause of the east-west asymmetric crater rims on Ryugu observed by LIDAR data 査読

    Naoyuki Hirata, Noriyuki Namiki, Fumi Yoshida, Koji Matsumoto, Hirotomo Noda, Hiroki Senshu, Takahide Mizuno, Fuyuto Terui, Yoshiaki Ishihara, Ryuhei Yamada, Keiko Yamamoto, Sinsuke Abe, Rina Noguchi, Naru Hirata, Yuichi Tsuda, Sei-ichiro Watanabe

    Icarus   354   114073 - 114073   2020年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    © 2020 Elsevier Inc. Asteroid 162,173 Ryugu is a rubble-pile asteroid, whose top-shape is compatible with models of deformation by spin up. Rims of major craters on Ryugu have an east–west asymmetric profile; their western crater rims are sharp and tall, while their eastern crater rims are rounded and low. Although there are various possible explanations, we theoretically assess the effect of asteroid rotation as the possible reason for this east–west asymmetry. It is known that the trajectories and fates of ejecta are affected by the rotation. The Coriolis force and the inertial speed of the rotating surface are the factors altering the ejecta trajectories. Consequently, we found that the east–west asymmetric crater rims might be formed as a result of rotation, when the inertial speed of the rotating surface is nearly equal to the first cosmic velocity of the body. In other words, it is possible that the observed east–west asymmetric rims of the Urashima, Cendrillon, and Kolobok craters were formed when Ryugu's rotation period was ~3.6 h.

    DOI: 10.1016/j.icarus.2020.114073

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  • Sample collection from asteroid (162173) Ryugu by Hayabusa2: Implications for surface evolution 査読

    T. Morota, S. Sugita, Y. Cho, M. Kanamaru, E. Tatsumi, N. Sakatani, R. Honda, N. Hirata, H. Kikuchi, M. Yamada, Y. Yokota, S. Kameda, M. Matsuoka, H. Sawada, C. Honda, T. Kouyama, K. Ogawa, H. Suzuki, K. Yoshioka, M. Hayakawa, N. Hirata, M. Hirabayashi, H. Miyamoto, T. Michikami, T. Hiroi, R. Hemmi, O. S. Barnouin, C. M. Ernst, K. Kitazato, T. Nakamura, L. Riu, H. Senshu, H. Kobayashi, S. Sasaki, G. Komatsu, N. Tanabe, Y. Fujii, T. Irie, M. Suemitsu, N. Takaki, C. Sugimoto, K. Yumoto, M. Ishida, H. Kato, K. Moroi, D. Domingue, P. Michel, C. Pilorget, T. Iwata, M. Abe, M. Ohtake, Y. Nakauchi, K. Tsumura, H. Yabuta, Y. Ishihara, R. Noguchi, K. Matsumoto, A. Miura, N. Namiki, S. Tachibana, M. Arakawa, H. Ikeda, K. Wada, T. Mizuno, C. Hirose, S. Hosoda, O. Mori, T. Shimada, S. Soldini, R. Tsukizaki, H. Yano, M. Ozaki, H. Takeuchi, Y. Yamamoto, T. Okada, Y. Shimaki, K. Shirai, Y. Iijima, H. Noda, S. Kikuchi, T. Yamaguchi, N. Ogawa, G. Ono, Y. Mimasu, K. Yoshikawa, T. Takahashi, Y. Takei, A. Fujii, S. Nakazawa, F. Terui, S. Tanaka, M. Yoshikawa, T. Saiki, S. Watanabe, Y. Tsuda

    Science   368 ( 6491 )   654 - 659   2020年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Association for the Advancement of Science (AAAS)  

    The near-Earth asteroid (162173) Ryugu is thought to be a primitive carbonaceous object that contains hydrated minerals and organic molecules. We report sample collection from Ryugu’s surface by the Hayabusa2 spacecraft on 21 February 2019. Touchdown images and global observations of surface colors are used to investigate the stratigraphy of the surface around the sample location and across Ryugu. Latitudinal color variations suggest the reddening of exposed surface material by solar heating and/or space weathering. Immediately after touchdown, Hayabusa2’s thrusters disturbed dark, fine grains that originate from the redder materials. The stratigraphic relationship between identified craters and the redder material indicates that surface reddening occurred over a short period of time. We suggest that Ryugu previously experienced an orbital excursion near the Sun.

    DOI: 10.1126/science.aaz6306

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  • An artificial impact on the asteroid (162173) Ryugu formed a crater in the gravity-dominated regime 査読

    M. Arakawa, T. Saiki, K. Wada, K. Ogawa, T. Kadono, K. Shirai, H. Sawada, K. Ishibashi, R. Honda, N. Sakatani, Y. Iijima, C. Okamoto, H. Yano, Y. Takagi, M. Hayakawa, P. Michel, M. Jutzi, Y. Shimaki, S. Kimura, Y. Mimasu, T. Toda, H. Imamura, S. Nakazawa, H. Hayakawa, S. Sugita, T. Morota, S. Kameda, E. Tatsumi, Y. Cho, K. Yoshioka, Y. Yokota, M. Matsuoka, M. Yamada, T. Kouyama, C. Honda, Y. Tsuda, S. Watanabe, M. Yoshikawa, S. Tanaka, F. Terui, S. Kikuchi, T. Yamaguchi, N. Ogawa, G. Ono, K. Yoshikawa, T. Takahashi, Y. Takei, A. Fujii, H. Takeuchi, Y. Yamamoto, T. Okada, C. Hirose, S. Hosoda, O. Mori, T. Shimada, S. Soldini, R. Tsukizaki, T. Iwata, M. Ozaki, M. Abe, N. Namiki, K. Kitazato, S. Tachibana, H. Ikeda, N. Hirata, N. Hirata, R. Noguchi, A. Miura

    Science   368 ( 6486 )   67 - 71   2020年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Association for the Advancement of Science (AAAS)  

    The Hayabusa2 spacecraft investigated the small asteroid Ryugu, which has a rubble-pile structure. We describe an impact experiment on Ryugu using Hayabusa2’s Small Carry-on Impactor. The impact produced an artificial crater with a diameter &gt;10 meters, which has a semicircular shape, an elevated rim, and a central pit. Images of the impact and resulting ejecta were recorded by the Deployable CAMera 3 for &gt;8 minutes, showing the growth of an ejecta curtain (the outer edge of the ejecta) and deposition of ejecta onto the surface. The ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface. The crater formed in the gravity-dominated regime; in other words, crater growth was limited by gravity not surface strength. We discuss implications for Ryugu’s surface age.

    DOI: 10.1126/science.aaz1701

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  • Highly porous nature of a primitive asteroid revealed by thermal imaging 査読

    Tatsuaki Okada, Tetsuya Fukuhara, Satoshi Tanaka, Makoto Taguchi, Takehiko Arai, Hiroki Senshu, Naoya Sakatani, Yuri Shimaki, Hirohide Demura, Yoshiko Ogawa, Kentaro Suko, Tomohiko Sekiguchi, Toru Kouyama, Jun Takita, Tsuneo Matsunaga, Takeshi Imamura, Takehiko Wada, Sunao Hasegawa, Jörn Helbert, Thomas G. Müller, Axel Hagermann, Jens Biele, Matthias Grott, Maximilian Hamm, Marco Delbo, Naru Hirata, Naoyuki Hirata, Yukio Yamamoto, Seiji Sugita, Noriyuki Namiki, Kohei Kitazato, Masahiko Arakawa, Shogo Tachibana, Hitoshi Ikeda, Masateru Ishiguro, Koji Wada, Chikatoshi Honda, Rie Honda, Yoshiaki Ishihara, Koji Matsumoto, Moe Matsuoka, Tatsuhiro Michikami, Akira Miura, Tomokatsu Morota, Hirotomo Noda, Rina Noguchi, Kazunori Ogawa, Kei Shirai, Eri Tatsumi, Hikaru Yabuta, Yasuhiro Yokota, Manabu Yamada, Masanao Abe, Masahiko Hayakawa, Takahiro Iwata, Masanobu Ozaki, Hajime Yano, Satoshi Hosoda, Osamu Mori, Hirotaka Sawada, Takanobu Shimada, Hiroshi Takeuchi, Ryudo Tsukizaki, Atsushi Fujii, Chikako Hirose, Shota Kikuchi, Yuya Mimasu, Naoko Ogawa, Go Ono, Tadateru Takahashi, Yuto Takei, Tomohiro Yamaguchi, Kent Yoshikawa, Fuyuto Terui, Takanao Saiki, Satoru Nakazawa, Makoto Yoshikawa, Seiichiro Watanabe, Yuichi Tsuda

    Nature   579 ( 7800 )   518 - 522   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Science and Business Media LLC  

    Carbonaceous (C-type) asteroids1 are relics of the early Solar System that have preserved primitive materials since their formation approximately 4.6 billion years ago. They are probably analogues of carbonaceous chondrites2,3 and are essential for understanding planetary formation processes. However, their physical properties remain poorly known because carbonaceous chondrite meteoroids tend not to survive entry to Earth’s atmosphere. Here we report on global one-rotation thermographic images of the C-type asteroid 162173 Ryugu, taken by the thermal infrared imager (TIR)4 onboard the spacecraft Hayabusa25, indicating that the asteroid’s boulders and their surroundings have similar temperatures, with a derived thermal inertia of about 300 J m−2 s−0.5 K−1 (300 tiu). Contrary to predictions that the surface consists of regolith and dense boulders, this low thermal inertia suggests that the boulders are more porous than typical carbonaceous chondrites6 and that their surroundings are covered with porous fragments more than 10 centimetres in diameter. Close-up thermal images confirm the presence of such porous fragments and the flat diurnal temperature profiles suggest a strong surface roughness effect7,8. We also observed in the close-up thermal images boulders that are colder during the day, with thermal inertia exceeding 600 tiu, corresponding to dense boulders similar to typical carbonaceous chondrites6. These results constrain the formation history of Ryugu: the asteroid must be a rubble pile formed from impact fragments of a parent body with microporosity9 of approximately 30 to 50 per cent that experienced a low degree of consolidation. The dense boulders might have originated from the consolidated innermost region or they may have an exogenic origin. This high-porosity asteroid may link cosmic fluffy dust to dense celestial bodies10.

    DOI: 10.1038/s41586-020-2102-6

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  • The spatial distribution of impact craters on Ryugu 査読

    Naoyuki Hirata, Tomokatsu Morota, Yuichiro Cho, Masanori Kanamaru, Sei-ichiro Watanabe, Seiji Sugita, Naru Hirata, Yukio Yamamoto, Rina Noguchi, Yuri Shimaki, Eri Tatsumi, Kazuo Yoshioka, Hirotaka Sawada, Yasuhiro Yokota, Naoya Sakatani, Masahiko Hayakawa, Moe Matsuoka, Rie Honda, Shingo Kameda, Manabu Yamada, Toru Kouyama, Hidehiko Suzuki, Chikatoshi Honda, Kazunori Ogawa, Yuichi Tsuda, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Shota Kikuchi, Tomohiro Yamaguchi, Naoko Ogawa, Go Ono, Yuya Mimasu, Kent Yoshikawa, Tadateru Takahashi, Yuto Takei, Atsushi Fujii, Hiroshi Takeuchi, Tatsuaki Okada, Kei Shirai, Yu-ichi Iijima

    Icarus   338   113527 - 113527   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    Asteroid 162173 Ryugu has numerous craters. The initial measurement of impact craters on Ryugu, by Sugita et al. (2019), is based on Hayabusa2 ONC images obtained during the first month after the arrival of Hayabusa2 in June 2018. Utilizing new images taken until February 2019, we constructed a global impact crater catalogue of Ryugu, which includes all craters larger than 20 m in diameter on the surface of Ryugu. As a result, we identified 77 craters on the surface of Ryugu. Ryugu shows variation in crater density which cannot be explained by the randomness of cratering; there are more craters at lower latitudes and fewer at higher latitudes, and fewer craters in the western bulge (160 degrees E - 290 degrees E) than in the region around the meridian (300 degrees E - 30 degrees E). This variation implies a complicated geologic history for Ryugu. It seems that the variation in crater density indicates that the equatorial ridge located in the western hemisphere is relatively young, while that located in the eastern hemisphere is a fossil structure formed during the short rotational period in the distant past.

    DOI: 10.1016/j.icarus.2019.113527

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  • Boulder size and shape distributions on asteroid Ryugu 査読

    Tatsuhiro Michikami, Chikatoshi Honda, Hideaki Miyamoto, Masatoshi Hirabayashi, Axel Hagermann, Terunori Irie, Keita Nomura, Carolyn M. Ernst, Masaki Kawamura, Kiichi Sugimoto, Eri Tatsumi, Tomokatsu Morota, Naru Hirata, Takaaki Noguchi, Yuichiro Cho, Shingo Kameda, Toru Kouyama, Yasuhiro Yokota, Rina Noguchi, Masahiko Hayakawa, Naoyuki Hirata, Rie Honda, Moe Matsuoka, Naoya Sakatani, Hidehiko Suzuki, Manabu Yamada, Kazuo Yoshioka, Hirotaka Sawada, Ryodo Hemmi, Hiroshi Kikuchi, Kazunori Ogawa, Sei-ichiro Watanabe, Satoshi Tanaka, Makoto Yoshikawa, Yuichi Tsuda, Seiji Sugita

    Icarus   331   179 - 191   2019年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    In 2018, the Japanese spacecraft Hayabusa2, arrived at the small asteroid Ryugu. The surface of this C-type asteroid is covered with numerous boulders whose size and shape distributions are investigated in this study. Using a few hundred Optical Navigation Camera (ONC) images with a pixel scale of approximately 0.65 m, we focus on boulders greater than 5 m in diameter. Smaller boulders are also considered using five arbitrarily chosen ONC close-up images with pixel scales ranging from 0.7 to 6 cm. Across the entire surface area (~2.7 km ) of Ryugu, nearly 4400 boulders larger than 5 m were identified. Boulders appear to be uniformly distributed across the entire surface, with some slight differences in latitude and longitude. At ~50 km , the number density of boulders larger than 20 m is twice as large as on asteroid Itokawa (or Bennu). The apparent shapes of Ryugu's boulders resemble laboratory impact fragments, with larger boulders being more elongated. The ratio of the total volume of boulders larger than 5 m to the total excavated volume of craters larger than 20 m on Ryugu can be estimated to be ~94%, which is comparatively high. These observations strongly support the hypothesis that most boulders found on Ryugu resulted from the catastrophic disruption of Ryugu's larger parent body, as described in previous papers (Watanabe et al., 2019; Sugita et al., 2019). The cumulative size distribution of boulders larger than 5 m has a power-index of −2.65 ± 0.05, which is comparatively shallow compared with other asteroids visited by spacecraft. For boulders smaller than 4 m, the power-index is even shallower and ranges from −1.65 ± 0.05 to −2.01 ± 0.06. This particularly shallow power-index implies that some boulders are buried in Ryugu's regolith. Based on our observations, we suggest that boulders near the equator might have been buried by the migration of finer material and, as a result, the number density of boulders larger than 5 m in the equatorial region is lower than at higher latitudes. 2 −2

    DOI: 10.1016/j.icarus.2019.05.019

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  • Installation of New GNSS Network Around Kusatsu-Shirane Volcano, Japan: Its Perspective and the First Result 査読

    Rina Noguchi, Tatsuji Nishizawa, Wataru Kanda, Takahiro Ohkura, Akihiko Terada

    Journal of Disaster Research   14 ( 5 )   744 - 754   2019年8月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Fuji Technology Press Ltd.  

    Crustal deformation is essential information for monitoring volcanic activity. In the summit area of the Kusatsu-Shirane Volcano (KSV), a dense Global Navigation Satellite System (GNSS) network has been operating near the recent volcanic center, Yugama crater. This network is sensitive to shallow depth activity, such as phreatic eruptions at the summit area, but is not applicable to deep magmatic activity, suggested to have been occurring for thousands of years by recent geological studies. Aiming to detect magmatic activity at a certain depth, we installed a new GNSS network near KSV. The observation sites were selected based on the crustal deformation pattern calculated for several intrusive events of the deep-seated magma. First, the GNSS sites for campaign observation were installed at eight locations in 2017. Then, four continuous sites commenced operation after a phreatic eruption at Mt. Motoshirane in January 2018. Here, we show the results of the first and second observation campaigns, operating in October 2017 and February 2018. Coordinate values are computed by precise point positioning with ambiguity resolution (PPP-AR) analysis and are used to calculate the displacement and the baseline length change during this period. The uncertainties of the calculated coordinate values are sufficiently small (less than 4.5 mm) except at some sites for which the data possibly include multipath errors due to trees and snow. Although any deformation associated with the 2018 eruption of Mt. Motoshirane is not detected, subsequent observations would contribute to monitoring long-term activity near KSV.

    DOI: 10.20965/jdr.2019.p0744

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  • Shift from magmatic to phreatomagmatic explosions controlled by the lateral evolution of a feeder dike in the Suoana-Kazahaya eruption, Miyakejima Volcano, Japan 査読

    Nobuo Geshi, Károly Németh, Rina Noguchi, Teruki Oikawa

    Earth and Planetary Science Letters   511   177 - 189   2019年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    © 2019 Explosive phreatomagmatic eruption is one of the most hazardous eruption styles, particularly in basaltic systems, as the instability of the conduit system can result in a sudden and unexpected shift of eruption style from a mild effusion of lavas to violently explosive activity. The geological investigations on the phreatomagmatic activities in the 7th Century, Suoana-Kazahaya eruption (SKE) of Miyakejima, reveal that the drop of magmatic overpressure in conduit and the distribution of groundwater controlled the occurrence of phreatomagmatic explosion. The “dry” magmatic eruption in the initial phase of the SKE indicates that the positive overpressure of magma in the propagating feeder dike prevents the invasion of external groundwater into the conduit. Explosive phreatomagmatic eruption occurred at the later phase of the SKE from the vents in the higher elevation. The drop of magmatic overpressure in the upper part of the feeder dike caused by the downslope propagation of the eruption fissure allowed groundwater inflow to the still hot and molten feeder dikes. The limited distribution of phreatomagmatic activities indicated the development of shallow groundwater, hosted in the porous pyroclastic deposits within a basin of less-permeable older edifice. As shifts of eruption style from initial magmatic to later phreatomagmatic explosive eruption style in the top of mafic volcanoes are globally observed in many mafic volcanic systems, such as Kilauea and Mt. Etna, this is probably a far more common eruption mechanism, than previously thought, and hence it needs to be considered in volcanic hazard scenario descriptions. The spatial distributions of phreatomagmatic activities in the SKE suggest that the detection of buried caldera structure in a volcanic edifice can indicate a potential site for phreatomagmatic explosion. The monitoring of the propagation of eruption fissure and drops of magmatic pressure and flux can indicate the potential of the phreatomagmatic explosion by the invasion of groundwater into the hot conduit.

    DOI: 10.1016/j.epsl.2019.01.038

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  • The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes 査読

    S. Sugita, R. Honda, T. Morota, S. Kameda, H. Sawada, E. Tatsumi, M. Yamada, C. Honda, Y. Yokota, T. Kouyama, N. Sakatani, K. Ogawa, H. Suzuki, T. Okada, N. Namiki, S. Tanaka, Y. Iijima, K. Yoshioka, M. Hayakawa, Y. Cho, M. Matsuoka, N. Hirata, N. Hirata, H. Miyamoto, D. Domingue, M. Hirabayashi, T. Nakamura, T. Hiroi, T. Michikami, P. Michel, R.-L. Ballouz, O. S. Barnouin, C. M. Ernst, S. E. Schröder, H. Kikuchi, R. Hemmi, G. Komatsu, T. Fukuhara, M. Taguchi, T. Arai, H. Senshu, H. Demura, Y. Ogawa, Y. Shimaki, T. Sekiguchi, T. G. Müller, A. Hagermann, T. Mizuno, H. Noda, K. Matsumoto, R. Yamada, Y. Ishihara, H. Ikeda, H. Araki, K. Yamamoto, S. Abe, F. Yoshida, A. Higuchi, S. Sasaki, S. Oshigami, S. Tsuruta, K. Asari, S. Tazawa, M. Shizugami, J. Kimura, T. Otsubo, H. Yabuta, S. Hasegawa, M. Ishiguro, S. Tachibana, E. Palmer, R. Gaskell, L. Le Corre, R. Jaumann, K. Otto, N. Schmitz, P. A. Abell, M. A. Barucci, M. E. Zolensky, F. Vilas, F. Thuillet, C. Sugimoto, N. Takaki, Y. Suzuki, H. Kamiyoshihara, M. Okada, K. Nagata, M. Fujimoto, M. Yoshikawa, Y. Yamamoto, K. Shirai, R. Noguchi, N. Ogawa, F. Terui, S. Kikuchi, T. Yamaguchi, Y. Oki, Y. Takao, H. Takeuchi, G. Ono, Y. Mimasu, K. Yoshikawa, T. Takahashi, Y. Takei, A. Fujii, C. Hirose, S. Nakazawa, S. Hosoda, O. Mori, T. Shimada, S. Soldini, T. Iwata, M. Abe, H. Yano, R. Tsukizaki, M. Ozaki, K. Nishiyama, T. Saiki, S. Watanabe, Y. Tsuda

    Science   364 ( 6437 )   eaaw0422 - eaaw0422   2019年3月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:American Association for the Advancement of Science (AAAS)  

    The near-Earth carbonaceous asteroid 162173 Ryugu is thought to have been produced from a parent body that contained water ice and organic molecules. The Hayabusa2 spacecraft has obtained global multi-color images of Ryugu. Geomorphological features present include a circum-equatorial ridge, east/west dichotomy, high boulder abundances across the entire surface, and impact craters. Age estimates from the craters indicate a resurfacing age of <inline-formula><m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"><m:mrow><m:mo>≲</m:mo><m:msup><m:mrow><m:mn>10</m:mn></m:mrow><m:mn>6</m:mn></m:msup></m:mrow></m:math></inline-formula> years for the top 1-meter layer. Ryugu is among the darkest known bodies in the Solar System. The high abundance and spectral properties of boulders are consistent with moderately dehydrated materials, analogous to thermally metamorphosed meteorites found on Earth. The general uniformity in color across Ryugu’s surface supports partial dehydration due to internal heating of the asteroid’s parent body.

    DOI: 10.1126/science.aaw0422

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  • Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu—A spinning top–shaped rubble pile 査読

    S. Watanabe, M. Hirabayashi, N. Hirata, N. Hirata, R. Noguchi, Y. Shimaki, H. Ikeda, E. Tatsumi, M. Yoshikawa, S. Kikuchi, H. Yabuta, T. Nakamura, S. Tachibana, Y. Ishihara, T. Morota, K. Kitazato, N. Sakatani, K. Matsumoto, K. Wada, H. Senshu, C. Honda, T. Michikami, H. Takeuchi, T. Kouyama, R. Honda, S. Kameda, T. Fuse, H. Miyamoto, G. Komatsu, S. Sugita, T. Okada, N. Namiki, M. Arakawa, M. Ishiguro, M. Abe, R. Gaskell, E. Palmer, O. S. Barnouin, P. Michel, A. S. French, J. W. McMahon, D. J. Scheeres, P. A. Abell, Y. Yamamoto, S. Tanaka, K. Shirai, M. Matsuoka, M. Yamada, Y. Yokota, H. Suzuki, K. Yoshioka, Y. Cho, S. Tanaka, N. Nishikawa, T. Sugiyama, H. Kikuchi, R. Hemmi, T. Yamaguchi, N. Ogawa, G. Ono, Y. Mimasu, K. Yoshikawa, T. Takahashi, Y. Takei, A. Fujii, C. Hirose, T. Iwata, M. Hayakawa, S. Hosoda, O. Mori, H. Sawada, T. Shimada, S. Soldini, H. Yano, R. Tsukizaki, M. Ozaki, Y. Iijima, K. Ogawa, M. Fujimoto, T.-M. Ho, A. Moussi, R. Jaumann, J.-P. Bibring, C. Krause, F. Terui, T. Saiki, S. Nakazawa, Y. Tsuda

    Science   364 ( 6437 )   eaav8032 - eaav8032   2019年3月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:American Association for the Advancement of Science (AAAS)  

    The Hayabusa2 spacecraft arrived at the near-Earth carbonaceous asteroid 162173 Ryugu in 2018. We present Hayabusa2 observations of Ryugu’s shape, mass, and geomorphology. Ryugu has an oblate ‘spinning top’ shape with a prominent circular equatorial ridge. Its bulk density, 1.19 ± 0.02 g cm<sup>–3</sup>, indicates a high porosity (&gt;50%) interior. Large surface boulders suggest a rubble-pile structure. Surface slope analysis shows Ryugu’s shape may have been produced if it once spun at twice the current rate. Coupled with the observed global material homogeneity, this suggests that Ryugu was reshaped by centrifugally induced deformation during a period of rapid rotation. From these remote-sensing investigations, we identify a suitable sample collection site on the equatorial ridge.

    DOI: 10.1126/science.aav8032

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  • Experimental approach to rootless eruptions using kitchen materials 査読

    Rina Noguchi, Ai Hamada, Ayako I. Suzuki, Kei Kurita

    Earth, Planets and Space   70 ( 1 )   2018年12月

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    担当区分:筆頭著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Science and Business Media {LLC}  

    Rootless eruption is caused by lava flow entering inland water or wet sediment and forms craters and cones far from the actual vent. Since the rootless eruption can be significantly explosive, the possibility of rootless eruption is critical for hazard management; however, forecasting occurrence and explosiveness of a rootless eruption remains difficult because explosiveness is considered to correlate nonlinearly with the mass ratio of hot lava and water. Here, we show the nonlinear nature of this type of eruption roots from the nonlinearly determined area between lava and underlying wet sediment as a function of water content within the wet sediment by a series of analog experiments can be implemented in a kitchen. In our analog experiment, lava and wet sediment were replaced by heated syrup and mixture of baking soda (sodium bicarbonate) and cake syrup. From measurements of mass loss due to CO 2 gas emission during the heat-induced decomposition of baking soda, we estimated the reaction efficiency for various proportions of baking soda and cake syrup in the substrate. We observed a nonlinear dependence of CO 2 emission; the peak efficiency was achieved for the substrate with 15 and 35 g of baking soda and cake syrup, respectively. Considering physical properties such as density and viscosity, we found that the Rayleigh–Taylor instability between the poured heated syrup and the substrate can explain the observed nonlinear dependence of CO 2 emission. For natural settings, the results of this study suggest that both the availability of water and rheological properties of the substrate affect the occurrence and stability of hydrovolcanic eruptions.[Figure not available: see fulltext.].

    DOI: 10.1186/s40623-018-0974-6

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  • Classification of volcanic ash particles using a convolutional neural network and probability 査読

    Daigo Shoji, Rina Noguchi, Shizuka Otsuki, Hideitsu Hino

    Scientific Reports   8 ( 1 )   2018年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Science and Business Media LLC  

    Analyses of volcanic ash are typically performed either by qualitatively classifying ash particles by eye or by quantitatively parameterizing its shape and texture. While complex shapes can be classified through qualitative analyses, the results are subjective due to the difficulty of categorizing complex shapes into a single class. Although quantitative analyses are objective, selection of shape parameters is required. Here, we applied a convolutional neural network (CNN) for the classification of volcanic ash. First, we defined four basal particle shapes (blocky, vesicular, elongated, rounded) generated by different eruption mechanisms (e.g., brittle fragmentation), and then trained the CNN using particles composed of only one basal shape. The CNN could recognize the basal shapes with over 90% accuracy. Using the trained network, we classified ash particles composed of multiple basal shapes based on the output of the network, which can be interpreted as a mixing ratio of the four basal shapes. Clustering of samples by the averaged probabilities and the intensity is consistent with the eruption type. The mixing ratio output by the CNN can be used to quantitatively classify complex shapes in nature without categorizing forcibly and without the need for shape parameters, which may lead to a new taxonomy.

    DOI: 10.1038/s41598-018-26200-2

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    その他リンク: http://www.nature.com/articles/s41598-018-26200-2

  • Detailed topographical, distributional, and material analyses of rootless cones in Myvatn, Iceland 査読

    Rina Noguchi, Ármann Höskuldsson, Kei Kurita

    Journal of Volcanology and Geothermal Research   318   89 - 102   2016年4月

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    担当区分:筆頭著者   掲載種別:研究論文(学術雑誌)  

    Unique types of rootless cones have been found both on Earth and on Mars. They have inner cones inside their summit craters, and we call them double cones (DCs) and multiple cones. Though previous studies have mentioned their existence, there are no quantitative data on their topography, distribution, or constituent materials. Having this information available as a comparative reference could promote our understanding of Martian cones. For this study, we conducted a field campaign on terrestrial cones in Myvatn, Iceland. To provide high-quality reference data about the morphology of rootless cones, we performed kinematic Global Positioning System (GPS) measurements. In the study area DCs and multiple cones are located in the vicinity of the lake (Lake Myvatn) within 15 km of a fissure vent. There are no such cones on the paleo-riverbed. In crosscut outcrops of DCs on Geitey Island, a clearly recognizable structural boundary between the inner and outer cones shows that the inner cone was formed by a separate explosion episode. We propose a probable formation scenario for DCs here. We posit that the inner cones of DCs are formed by delayed explosions due to percolation of water through the lacustrine sediments. These unique characteristics of rootless cones are useful in the interpretation of Martian cones.

    DOI: 10.1016/j.jvolgeores.2016.03.020

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  • 火星におけるコーン地形 査読

    野口里奈, 栗田敬

    地學雜誌   125 ( 1 )   35 - 48   2016年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:公益社団法人 東京地学協会  

    &emsp;Cone morphologies with a variety of origins and sizes have been widely identified on Mars using remote sensing data such as ultra-high resolution visible images. Currently, small cones of less than 100 m in bottom diameter can be identified. These Martian cones are located in young surface regions, suggesting they were produced in an environment that existed in recent geological history. They had volcanic, periglacial, and other origins. This paper first introduces a classification of terrestrial cone morphology: volcanic (spatter cones, scoria/pumice cones, maars, tuff rings, tuff cones, and rootless cones), periglacial (pingos), and others (mud volcanoes). Then, it reviews the characteristics of cone morphology on Mars focusing on morphology, morphometry, and distribution. Previous cone studies show the existence of explosive basaltic eruptions on recent Mars, while young lava flows were pervasive. The prevalence of rootless cones suggests the presence of water/ice during their formation at many places on Mars. These discoveries contribute to clarifying the recent surface environment and thermal state of Mars. To further apply terrestrial knowledge to Martian cones, it is necessary to understand the relationship between the morphology and the formation process of cone morphologies on Earth from a wide perspective.

    DOI: 10.5026/jgeography.125.35

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  • 異なる噴火様式で形成された火砕物のクラスタリング

    野口 里奈, 下司 信夫

    日本火山学会講演予稿集   2016   20 - 20   2016年

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    記述言語:日本語   出版者・発行元:特定非営利活動法人 日本火山学会  

    DOI: 10.18940/vsj.2016.0_20

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  • Unique characteristics of cones in Central Elysium Planitia, Mars 査読

    Rina Noguchi, Kei Kurita

    Planetary and Space Science   111 ( 1 )   44 - 54   2015年6月

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    担当区分:筆頭著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    Martian magmatism within recent several hundreds of millions years is still controversial. Central Elysium Planitia (CEP) is suspected as a site of the latest magmatism on Mars, but hot debates have been caused as for the origin of this flat plain. Cones in CEP are expected to be a key to resolve this controversy. In previous works, there are 2 models proposed for the origin of CEP cones: volcanic rootless cone (e.g. Jaeger et al., 2007) and periglacial pingo (e.g. Burr et al., 2002; Page et al., 2009). In this study, we described detail morphology, distribution and size of CEP cones by using high-resolution images and topographic data. CEP cones are classified into 3 morphological types: Single Cone (SC), Double Cone (DC), and Lotus Fruit Cone (LC). DC has an inner cone in the summit crater of the outer cone, and LC has several inner cones in the summit crater of the outer cone. Several cones have moat structure around the edifice with peripheral rise. DCs and LCs are located in very flat areas of Athabasca Valles in the vicinity of Cerberus Fossae, while SCs distribute in the entire region of CEP. We compared CEP cones with terrestrial rootless cones and pingos in aerial photos. In Lake Myvatn, Iceland, there exist rootless cones which resemble DCs and LCs in CEP. Based on the similarities with terrestrial analogies, we concluded that the most feasible origin of CEP cones is rootless cones.

    DOI: 10.1016/j.pss.2015.03.007

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  • K-GPSを用いた火山地形の計測 : 伊豆大室山での試行 査読

    野口里奈, 吉田朱里, 猿谷友孝, 西川泰弘, 栗田敬

    火山   60 ( 3 )   357 - 363   2015年5月

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    担当区分:筆頭著者   記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:特定非営利活動法人日本火山学会  

    Morphometrical studies on small volcanic edifices such as scoria cones have been extensively conducted. Nevertheless, some morphometric parameters have been difficult to obtain. For instance, it is often difficult to measure a slope angle of volcano edifice because DEM (Digital Elevation Model) with high spatial resolution are not always available. We used the K-GPS (Kinematic Global Positioning System) for high resolution measurement of the slope angle of Omuroyama, a typical young scoria cone in Eastern Izu, Japan, assuming no detailed DEM available in the region. We show the existence of constant slope of 32° from the base to the top. The result of the K-GPS measurement is consistent with the existing DEM of this region. We report the measuring system is simple and viable for summary survey of slope angle where no DEMs are available.

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書籍等出版物

  • 火星の歩き方

    臼井, 寛裕, 野口, 里奈, 庄司, 大悟

    光文社  2021年12月  ( ISBN:9784334045807

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    総ページ数:233p, 図版 [1] 枚   記述言語:日本語

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  • 「はやぶさ2」のすべて : 小惑星リュウグウ探査プロジェクト

    吉川, 真

    誠文堂新光社  2020年12月  ( ISBN:9784416620649

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    総ページ数:143p   記述言語:日本語

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MISC

  • 小惑星リュウグウ形状モデリングの現状

    平田成, 平田直之, 野口里奈, 嶌生有理, 杉田精司, 松本晃治, 千秋博紀, 山本幸生, 村上真也, 村上真也, 石原吉明, 津田雄一, 渡邊誠一郎, GASKELL Robert, PALMER Eric

    日本惑星科学会秋季講演会予稿集(Web)   2020   2020年

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  • ラブルパイル小惑星リュウグウの形状と起源

    渡邊誠一郎, 渡邊誠一郎, 平林正俊, 平田成, 平田直之, 野口里奈, 嶌生有理, 池田人, 巽瑛理, 吉川真, 菊地翔太, 薮田ひかる, 中村智樹, 橘省吾, 橘省吾, 石原吉明, 諸田智克, 北里宏平, 坂谷尚哉, 松本晃治, 松本晃治, 和田浩二, 千秋博紀, 本田親寿, 道上達広, 竹内央, 神山徹, 本田理恵, GASKELL Robert, PALMER Eric, BARNOUIN Olivier S., MICHEL Patrick, ABELL Paul, 山本幸生, 田中智, 白井慶, 松岡萌, 杉田精司, 杉田精司, 岡田達明, 並木則行, 荒川政彦, 石黒正晃, 小川和律, 照井冬人, 佐伯孝尚, 中澤暁, 津田雄一

    日本地球惑星科学連合大会予稿集(Web)   2019   2019年

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  • 火の鳥「はやぶさ」未来編 その17~リュウグウの地名~

    野口里奈, 嶌生有理, 吉川真, 宮本英昭, 小松吾郎, 渡邊誠一郎, 渡邊誠一郎, 石原吉明, 佐々木晶, 平林正俊, 平田成, 本田親寿, 出村裕英, 杉田精司, 津田雄一

    日本惑星科学会誌 遊・星・人   28 ( 1 )   2019年

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  • 162173リュウグウ表面の岩石の明るさと形状の変化

    佐々木晶, 杉田精司, 巽瑛理, 宮本英昭, 本田親寿, 諸田智克, 平林正稔, 神田志穂, 平田成, 廣井孝弘, 中村智樹, 野口高明, 本田理恵, 道上達広, 渡邊誠一郎, 並木則行, MICHEL Patrick, 亀田真吾, 神山徹, 鈴木秀彦, 山田学, 菊地紘, 長勇一郎, 吉岡和夫, 早川雅彦, 松岡萌, 野口里奈, 坂谷尚哉, 澤田弘崇, 横田康弘, 横田康弘, 吉川真

    日本地球惑星科学連合大会予稿集(Web)   2019   2019年

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  • はやぶさ2探査機の観測に基づく小惑星リュウグウの形状

    平田成, 平田直之, 田中小百合, 西川直輝, 杉山貴亮, GASKELL R., PALMER E., 野口里奈, 嶌生有理, 杉田精司, 津田雄一, 渡邊誠一郎

    日本惑星科学会秋季講演会予稿集(Web)   2018   2018年

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受賞

  • 理事長表彰

    2020年11月   宇宙航空研究開発機構  

    はやぶさ2プロジェクトチーム

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  • 第8回技術経営・イノベーション大賞(科学技術と経済の会会長賞)

    2020年2月   科学技術と経済の会   はやぶさ2による未踏天体探査の完遂と新たな探査技術の確立

    はやぶさ2プロジェクトチーム

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  • 内閣総理大臣顕彰

    2019年12月  

    はやぶさ2プロジェクトチーム

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  • 第50回星雲賞 自由部門

    2019年7月   日本SFファングループ連合会議   MINERVA-Ⅱ1のリュウグウ着地及び小惑星移動探査

    はやぶさ2プロジェクトチーム

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  • COOL JAPAN AWARD 2019 【一般部門】アウトバウンドカテゴリー

    2019年5月   クールジャパン協議会  

    JAXA「はやぶさ」および「はやぶさ 2」

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  • 日本航空宇宙学会賞 技術賞,プロジェクト部門

    2019年3月   日本航空宇宙学会   はやぶさ2による小天体ランデブーのための深宇宙航行技術の進展と小惑星Ryuguへの到着

    はやぶさ2プロジェクト

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  • 学生優秀発表賞

    2012年6月   日本地球惑星科学連合  

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  • 総長賞

    2010年3月   東海大学  

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共同研究・競争的資金等の研究

  • 火星への適用を目指した露頭柱状図の自動作成手法の開発

    研究課題/領域番号:22K14082  2022年4月 - 2026年3月

    日本学術振興会  科学研究費助成事業 若手研究  若手研究

    野口 里奈

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    配分額:4160000円 ( 直接経費:3200000円 、 間接経費:960000円 )

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  • 岩相の特徴量自動認識による火山性露頭その場調査手法の研究

    研究課題/領域番号:22H01326  2022年4月 - 2025年3月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    春山 純一

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    配分額:7670000円 ( 直接経費:5900000円 、 間接経費:1770000円 )

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  • 火山灰のシステマティックス構築に基づく噴火推移と火道進化過程の関係解明研究

    研究課題/領域番号:20H01986  2020年4月 - 2024年3月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    嶋野 岳人, 野口 里奈, 上木 賢太, 井口 正人, 桑谷 立, 安田 敦, 三輪 学央

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    配分額:17810000円 ( 直接経費:13700000円 、 間接経費:4110000円 )

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  • 火山噴火推移予測のための数理統計学的手法による噴出物データの解析研究

    研究課題/領域番号:17H02063  2017年4月 - 2020年3月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    嶋野 岳人, 野口 里奈, 上木 賢太, 井口 正人, 安田 敦, 三輪 学央

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    配分額:17940000円 ( 直接経費:13800000円 、 間接経費:4140000円 )

    初年度に引き続き,代表・各分担者がすでに獲得している火山噴出物データ(化学組成,形態,測色値)を用い,これらの統計解析を含む解析を行った.数理を専門とする研究者によるアドバイスを得ながら研究者間でこれらの結果について意見交換を行い,マグマの成因や噴火様式の違いなど,試料の持つ特性や指標などをより的確に導出するための方法を検討した.
    【課題1】については,時刻精度を高めるなどの改良を行った噴出物連続採取装置改良機による観測を5月から開始し,現在は試料回収が順調に進んでいる(嶋野).初年度にルーチン化を進めた調整・分析手法について,より効率的な解析環境の整備を行った.特に,電子顕微鏡写真から噴出物の気泡の径・形・量(数)を迅速に計測する手法を開発した(安田).
    【課題2】については,化学組成や噴出物の形態に関して主成分・クラスター分析をもちいて,マグマの生成条件や噴火様式を判別できることが明らかとなってきたが,これらが論文として発表された(野口,上木).
    【課題3】については,桜島火山の噴出物データ(火山灰測色値)と地球物理学的データ(地震・爆発回数や地殻変動量など)の時系列変化について解析を行った.特に,地下のマグマの上昇・移動などに伴って生じるであろうこれらのデータの時間差について,時系列解析の手法を用いて定量的に明らかにした.
    以上を代表者および分担者がそれぞれの担当分野,火山で行い,翌最終年度に向けてより汎用性の高い手法を確立していくための議論を行った.

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