131 results on '"Masahiko Arakawa"'
Search Results
2. Experimental Investigation of Visible-Light and X-ray Emissions during Rock and Mineral Fracture: Role of Electrons Traveling between Fracture Surfaces
- Author
-
Toshihiko Kadono, Kazunori Ogawa, Kei Shirai, Masahiko Arakawa, Kosuke Kurosawa, Takaya Okamoto, Takafumi Matsui, Sunao Hasegawa, Ayako I. Suzuki, and Hideyuki Kobayashi
- Subjects
rock and mineral fracture ,visible light ,X-ray ,electron travelling ,Mineralogy ,QE351-399.2 - Abstract
Radiation phenomena are usually observed during fracture of quartz-bearing rocks. Since quartz is a piezoelectric material, the associated electrical processes such as the electrification of fracture surface and the flight of electrons between fracture surfaces should be important for radiation during fractures. In this article, supposing that travelling electrons between crack surfaces cause the radiation, we experimentally investigate X-ray emission in a vacuum and visible-light emission in the atmosphere during rock and mineral fracture and verify the consistency of both emissions. The number of electrons in flight between surfaces during fracture that result in X-ray is estimated and the comparison with the number of photons in visible light suggests that one electron repeatedly collides with N2 molecules. The estimated number of collisions resulting in a visible-light emission is slightly less than the expected upper limit. This is reasonable because the collision would cause the light emission not always in the wavelengths of visible light. Moreover, the number of electrons resulting in X-rays is comparable with the number of electrons resulting in the emission of radio waves during fracture obtained in previous studies. Thus, we conclude that the radiations during fracture can be attributed to the flight of electrons between fracture surfaces. Finally, we evaluate the feasibility of observing the X-ray emission in planetary exploration and the radio waves and the visible light in natural earthquakes and find that these radiations are observable.
- Published
- 2022
- Full Text
- View/download PDF
3. Soluble Organic Molecules in Samples of the Carbonaceous Asteroid (162173) Ryugu
- Author
-
Hiroshi Naraoka, Yoshinori Takano, Jason P Dworkin, Yasuhiro Oba, Kenji Hamase, Aogu Furusho, Nanako O Ogawa, Minako Hashiguchi, Kazuhiko Fukushima, Dan Aoki, Philippe Schmitt Kopplin, José C Aponte, Eric T Parker, Daniel P Glavin, Hannah L McLain, Jamie E Elsila, Heather V Graham, John M Eiler, Francois-Regis Orthous-Daunay, Cedric Wolters, Junko Isa, Véronique Vuitton, Roland Thissen, Saburo Sakai, Toshihiro Yoshimura, Toshiki Koga, Naohiko Ohkouchi, Yoshito Chikaraishi, Haruna Sugahara, Hajime Mita, Yoshihiro Furukawa, Norbert Hertkorn, Alexander Ruf, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Kanako Sakamoto, Shogo Tachibana, Harold C Connolly, Jr, Dante S Lauretta, Masanao Abe, Toru Yada, Masahiro Nishimura, Kasumi Yogata, Aiko Nakato, Miwa Yoshitake, Ayako Suzuki, Akiko Miyazaki, Shizuho Furuya, Kentaro Hatakeda, Hiromichi Soejima, Yuya Hitomi, Kazuya Kumagai, Tomohiro Usui, Tasuku Hayashi, Daiki Yamamoto, Ryota Fukai, Kohei Kitazato, Seiji Sugita, Noriyuki Namiki, Masahiko Arakawa, Hitoshi Ikeda, Masateru Ishiguro, Naru Hirata, Koji Wada, Yoshiaki Ishihara, Rina Noguchi, Tomokatsu Morota, Naoya Sakatani, Koji Matsumoto, Hiroki Senshu, Rie Honda, Eri Tatsumi, Yasuhiro Yokota, Chikatoshi Honda, Tatsuhiro Michikami, Moe Matsuoka, Akira Miura, Hirotomo Noda, Tetsuya Yamada, Keisuke Yoshihara, Kosuke Kawahara, Masanobu Ozaki, Yu-ichi Iijima, Hajime Yano, Masahiko Hayakawa, Takahiro Iwata, Ryudo Tsukizaki, Hirotaka Sawada, Satoshi Hosoda, Kazunori Ogawa, Chisato Okamoto, Naoyuki Hirata, Kei Shirai, Yuri Shimaki, Manabu Yamada, Tatsuaki Okada, Yukio Yamamoto, Hiroshi Takeuchi, Atsushi Fujii, Yuto Takei, Kento Yoshikawa, Yuya Mimasu, Go Ono, Naoko Ogawa, Shota Kikuchi, Satoru Nakazawa, Fuyuto Terui, Satoshi Tanaka, Takanao Saiki, Makoto Yoshikawa, Sei-ichiro Watanabe, and Yuichi Tsuda
- Subjects
Lunar and Planetary Science and Exploration - Abstract
The Hayabusa2 spacecraft collected samples from the surface of the carbonaceous near-Earth asteroid (162173) Ryugu, and brought them to Earth. The samples were expected to contain organic molecules, which record processes that occurred in the early Solar System. We analyzed organic molecules extracted from the Ryugu surface samples. We identify a variety of molecules containing the atoms CHNOS, formed by methylation, hydration, hydroxylation, and sulfurization reactions. Amino acids, aliphatic amines, carboxylic acids, polycyclic aromatic hydrocarbons, and nitrogen-heterocyclic compounds were detected, with properties consistent with an abiotic origin. These compounds likely arose from aqueous reaction on Ryugu’s parent body and are similar to organics in Ivuna-type meteorites. These molecules can survive on the surfaces of asteroids and be transported throughout the Solar System.
- Published
- 2023
- Full Text
- View/download PDF
4. A pristine record of outer Solar System materials from asteroid Ryugu’s returned sample
- Author
-
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, and Yuichi Tsuda
- Subjects
Astronomy and Astrophysics - Abstract
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 °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.
- Published
- 2022
5. On the origin and evolution of the asteroid Ryugu: A comprehensive geochemical perspective
- Author
-
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, and Yuichi TSUDA
- Subjects
Water ,General Physics and Astronomy ,Meteoroids ,Solar System ,General Medicine ,General Agricultural and Biological Sciences - Abstract
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 δ18O, Δ17O, and ε54Cr 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)
- Published
- 2022
6. Macromolecular organic matter in samples of the asteroid (162173) Ryugu
- Author
-
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, Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), ANR-18-CE31-0011,COMETOR,Origine de la poussière cométaire(2018), and European Project: 819587,HYDROMA
- Subjects
Multidisciplinary ,[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] ,Macromolecular organic carbonaceous samples asteroid Ryugu Hayabusa2 MASCOT - Abstract
International audience; INTRODUCTION: Organic compounds in asteroids and comets contain information about the early history of the Solar System. They could also have delivered organic material to early Earth. The Hayabusa2 spacecraft visited the carbonaceous asteroid Ryugu and collected samples of its surface materials, which were brought to Earth in December 2020. RATIONALE: We investigated the macromolecular organic matter in the Ryugu samples, measuring its elemental, isotopic, and functional group compositions along with its small-scale structures and morphologies. Analytical methods used included spectro-microscopies, electron microscopy, and isotopic microscopy. We examined intact Ryugu grains and insoluble carbonaceous residues isolated by acid treatment of the Ryugu samples. RESULTS: Organic matter is abundant in the Ryugu grains, distributed as submicrometersized organic grains and as organic matter dispersed in matrix. The Ryugu organic matter consists of aromatic carbons, aliphatic carbons, ketones, and carboxyls. The functional group
- Published
- 2023
7. Preliminary analysis of the Hayabusa2 samples returned from C-type asteroid Ryugu
- Author
-
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, and Yuichi Tsuda
- Subjects
010504 meteorology & atmospheric sciences ,13. Climate action ,0103 physical sciences ,Astronomy and Astrophysics ,010303 astronomy & astrophysics ,01 natural sciences ,0105 earth and related environmental sciences - 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.
- Published
- 2021
8. A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu
- Author
-
Takaaki Noguchi, Toru Matsumoto, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hope A. Ishii, John P. Bradley, Kenta K. Ohtaki, Elena Dobrică, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Peña, Sylvain Laforet, Maya Marinova, Falko Langenhorst, Dennis Harries, Pierre Beck, Thi H. V. Phan, Rolando Rebois, Neyda M. Abreu, Jennifer Gray, Thomas Zega, Pierre-M. Zanetta, Michelle S. Thompson, Rhonda Stroud, Kate Burgess, Brittany A. Cymes, John C. Bridges, Leon Hicks, Martin R. Lee, Luke Daly, Phil A. Bland, Michael E. Zolensky, David R. Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Masanao Abe, Masahiko Arakawa, Atsushi Fujii, Masahiko Hayakawa, Naru Hirata, Naoyuki Hirata, Rie Honda, Chikatoshi Honda, Satoshi Hosoda, Yu-ichi Iijima, Hitoshi Ikeda, Masateru Ishiguro, Yoshiaki Ishihara, Takahiro Iwata, Kousuke Kawahara, Shota Kikuchi, Kohei Kitazato, Koji Matsumoto, Moe Matsuoka, Yuya Mimasu, Akira Miura, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hirotaka Sawada, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Ryudo Tsukizaki, Koji Wada, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Ryohta Fukai, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Hiromichi Soejima, Ayako I. Suzuki, Tomohiro Usui, Toru Yada, Daiki Yamamoto, Kasumi Yogata, Miwa Yoshitake, Harold C. Connolly, Dante S. Lauretta, Hisayoshi Yurimoto, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamoto, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei-ichiro Watanabe, Yuichi Tsuda, Université de Lille, CNRS, INRAE, ENSCL, Unité Matériaux et Transformations (UMET) - UMR 8207, Unité Matériaux et Transformations - UMR 8207 [UMET], and Institut Chevreul - FR2638
- Subjects
Astronomy and Astrophysics - Abstract
Without a protective atmosphere, space-exposed surfaces of airless Solar System bodies gradually experience an alteration in composition, structure and optical properties through a collective process called space weathering. The return of samples from near-Earth asteroid (162173) Ryugu by Hayabusa2 provides the first opportunity for laboratory study of space-weathering signatures on the most abundant type of inner solar system body: a C-type asteroid, composed of materials largely unchanged since the formation of the Solar System. Weathered Ryugu grains show areas of surface amorphization and partial melting of phyllosilicates, in which reduction from Fe3+ to Fe2+ and dehydration developed. Space weathering probably contributed to dehydration by dehydroxylation of Ryugu surface phyllosilicates that had already lost interlayer water molecules and to weakening of the 2.7 µm hydroxyl (–OH) band in reflectance spectra. For C-type asteroids in general, this indicates that a weak 2.7 µm band can signify space-weathering-induced surface dehydration, rather than bulk volatile loss.
- Published
- 2022
9. Exploration-Based Reconstruction of Planetesimals.
- Author
-
Sei-ichiro Watanabe, Masahiko Arakawa, Masatoshi Hirabayashi, Seiji Sugita, Bottke, William F., and Michel, Patrick
- Published
- 2023
- Full Text
- View/download PDF
10. The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos
- Author
-
Patrick Michel, Michael Küppers, Adriano Campo Bagatin, Benoit Carry, Sébastien Charnoz, Julia de Leon, Alan Fitzsimmons, Paulo Gordo, Simon F. Green, Alain Hérique, Martin Juzi, Özgür Karatekin, Tomas Kohout, Monica Lazzarin, Naomi Murdoch, Tatsuaki Okada, Ernesto Palomba, Petr Pravec, Colin Snodgrass, Paolo Tortora, Kleomenis Tsiganis, Stephan Ulamec, Jean-Baptiste Vincent, Kai Wünnemann, Yun Zhang, Sabina D. Raducan, Elisabetta Dotto, Nancy Chabot, Andy F. Cheng, Andy Rivkin, Olivier Barnouin, Carolyn Ernst, Angela Stickle, Derek C. Richardson, Cristina Thomas, Masahiko Arakawa, Hirdy Miyamoto, Akiko Nakamura, Seiji Sugita, Makoto Yoshikawa, Paul Abell, Erik Asphaug, Ronald-Louis Ballouz, William F. Bottke, Dante S. Lauretta, Kevin J. Walsh, Paolo Martino, Ian Carnelli, Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE), Universidad de Alicante. Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Astronomía y Astrofísica, Department of Geosciences and Geography, Geology and Geophysics, Department of Physics, Planetary-system research, Michel P., Kuppers M., Bagatin A.C., Carry B., Charnoz S., de Leon J., Fitzsimmons A., Gordo P., Green S.F., Herique A., Juzi M., Karatekin O., Kohout T., Lazzarin M., Murdoch N., Okada T., Palomba E., Pravec P., Snodgrass C., Tortora P., Tsiganis K., Ulamec S., Vincent J.-B., Wunnemann K., Zhang Y., Raducan S.D., Dotto E., Chabot N., Cheng A.F., Rivkin A., Barnouin O., Ernst C., Stickle A., Richardson D.C., Thomas C., Arakawa M., Miyamoto H., Nakamura A., Sugita S., Yoshikawa M., Abell P., Asphaug E., Ballouz R.-L., Bottke W.F., Lauretta D.S., Walsh K.J., Martino P., and Carnelli I.
- Subjects
1171 Geosciences ,Asteroid surfaces ,Impact phenomena ,Impact phenomena (779) ,Mission ,Near-Earth objects ,114 Physical sciences ,Asteroid dynamic ,Autre ,Asteroid satellites ,Earth and Planetary Sciences (miscellaneous) ,Binary ,Near-Earth objects (1092) ,Near-Earth object ,520 Astronomy ,Asteroid dynamics ,Asteroid ,Astronomy and Astrophysics ,620 Engineering ,115 Astronomy, Space science ,Asteroid satellites (2207) ,Asteroid satellite ,Asteroid surfaces (2209) ,Geophysics ,Space and Planetary Science ,Asteroid dynamics (2210) ,Planetary defense - Abstract
Funding Information: To achieve these objectives, Milani is carrying two scientific payloads, the ASPECT visual and near-infrared (Vis-NIR) imaging spectrometer and the VISTA thermogravimeter aimed at collecting and characterizing volatiles and dust particles below 10 μm. Additionally, navigation payloads include a visible navigation camera and lidar. The Milani consortium is composed of entities and institutions from Italy, the Czech Republic, and Finland. The consortium Prime is Tyvak International, responsible for the whole program management and platform design, development, integration, testing, and final delivery to the customer. Politecnico di Torino is tasked with defining requirements and performing thermal, radiation, and debris analysis. Politecnico di Milano is responsible for mission analysis and GNC. Altec will support the Ground Segment architecture and interface definition. Centro Italiano per la Ricerca Aerospaziale (CIRA) is responsible for the execution of the vehicle environmental campaign. HULD contributes to developing the mission-specific software. VTT is the main payload (ASPECT hyperspectral imager) provider and is supported by the following entities dealing with ASPECT-related development: University of Helsinki (ASPECT calibration); Reaktor Space Lab (ASPECT Data Processing Unit development), Institute of Geology of the Czech Academy of Sciences (ASPECT scientific algorithms requirements and testing); and Brno University of Technology (ASPECT scientific algorithms development). INAF-IAPS is the secondary Payload (VISTA, dust detector) provider. Funding Information: The Mission PI is appointed by ESA and is the primary interface to ESA. The Hera SMB consists of the ESA Hera Project Scientist (ESA PS), the Mission PI, and the Hera Advisory Board, consisting of four mission advisors. The Mission PI chairs the HIT and is supported by the Hera Advisory Board. The tasks of the Hera SMB are 1. advising the Hera mission project team on all aspects related to the Hera mission objectives; 2. ensuring that the WGs’ activities cover the needs of the Hera mission; 3. providing recommendations to ESA concerning the membership in the HIT; and 4. implementing the Publication Policy. Funding Information: Hera is the ESA contribution to the AIDA collaboration. Hera, Juventas, Milani, and their instruments are developed under ESA contract supported by national agencies. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 870377 (project NEO-MAPP), the CNRS through the MITI interdisciplinary programs, ASI, CNES, JAXA, the Academy of Finland project no. 335595, and was conducted with institutional support RVO 67985831 of the Institute of Geology of the Czech Academy of Sciences. M.L., E.P., P.T .and E.D. are grateful to the Italian Space Agency (ASI) for financial support through Agreement No. 2022-8-HH.0 in the context of ESA’s Hera mission. We are grateful to the whole Hera team, including Working Group core members and other contributors for their continuous efforts and support. Their names can be found on the following website: https:// www.heramission.space/team. Publisher Copyright: © 2022. The Author(s). Published by the American Astronomical Society. Hera is a planetary defense mission under development in the Space Safety and Security Program of the European Space Agency for launch in 2024 October. It will rendezvous in late 2026 December with the binary asteroid (65803) Didymos and in particular its moon, Dimorphos, which will be impacted by NASA’s DART spacecraft on 2022 September 26 as the first asteroid deflection test. The main goals of Hera are the detailed characterization of the physical properties of Didymos and Dimorphos and of the crater made by the DART mission, as well as measurement of the momentum transfer efficiency resulting from DART’s impact. The data from the Hera spacecraft and its two CubeSats will also provide significant insights into asteroid science and the evolutionary history of our solar system. Hera will perform the first rendezvous with a binary asteroid and provide new measurements, such as radar sounding of an asteroid interior, which will allow models in planetary science to be tested. Hera will thus provide a crucial element in the global effort to avert future asteroid impacts at the same time as providing world-leading science.
- Published
- 2022
11. Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites
- Author
-
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, Cosmochimie [IMPMC] (IMPMC_COSMO), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Centre de Recherches Pétrographiques et Géochimiques (CRPG), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Multidisciplinary ,[SDU]Sciences of the Universe [physics] - Abstract
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 measured the mineralogy and bulk chemical and isotopic compositions of Ryugu samples. The samples are mainly composed of materials similar to those of 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, about 5.2 − 0.7 + 0.8 million (statistical) or 5.2 − 2.1 + 1.6 million (systematic) years after the 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 that of the Sun’s photosphere than other natural samples do.
- Published
- 2022
12. Motion reconstruction of the small carry-on impactor aboard Hayabusa2
- Author
-
Yuto Takei, Yuya Mimasu, Takanao Saiki, Yasuhiro Yokota, Hirohito Ohtsuka, Go Ono, Shota Kikuchi, Hirotaka Sawada, Kent Yoshikawa, Sei-ichiro Watanabe, Satoshi Tanaka, Yukio Yamamoto, Chikako Hirose, Naruhisa Sano, Satoru Nakazawa, Fuyuto Terui, Kei Shirai, Akira Miura, Masahiko Arakawa, Seiji Sugita, Rie Honda, Takahiro Iwata, Kazunori Ogawa, Hiroshi Takeuchi, Yuichi Tsuda, Makoto Yoshikawa, Manabu Yamada, Koji Wada, Yuri Shimaki, and Naoko Ogawa
- Subjects
Spacecraft ,business.industry ,Projectile ,Motion reconstruction ,Impact angle ,Aerospace Engineering ,Astronomy and Astrophysics ,Altitude ,Impact crater ,Space and Planetary Science ,Asteroid ,Aerospace engineering ,business ,Ejecta ,Geology - Abstract
Subsurface exploration is one of the most ambitious scientific objectives of the Hayabusa2 mission. A small device called small carry-on impactor (SCI) was developed to create an artificial crater on the surface of asteroid Ryugu. This enables us to sample subsurface materials, which will provide a window to the past. The physical properties of the resulting crater are also useful for understanding the internal structure of Ryugu. Accurate understanding of the crater and ejecta properties, including the depth of excavation of subsurface materials, requires accurate information on impact conditions. In particular, the impact angle is a critical factor because it greatly influences the size and shape of the crater. On April 5, 2019, the Hayabusa2 spacecraft deployed the SCI at 500 m of altitude above the asteroid surface. The SCI gradually reduced its altitude, and it shot a 2 kg copper projectile into the asteroid 40 min after separation. Estimating the position of the released SCI is essential for determining the impact angle. This study describes the motion reconstruction of the SCI based on the actual operation data. The results indicate that the SCI was released with high accuracy.
- Published
- 2020
13. Hayabusa2's kinetic impact experiment: Operational planning and results
- Author
-
Kent Yoshikawa, Hirotaka Sawada, Takanao Saiki, Seiji Sugita, Yuichi Tsuda, Satoru Nakazawa, Fuyuto Terui, Yuya Mimasu, Yuto Takei, Sei-ichiro Watanabe, Masahiko Arakawa, Makoto Yoshikawa, Naoko Ogawa, and Go Ono
- Subjects
020301 aerospace & aeronautics ,Spacecraft ,business.industry ,Aerospace Engineering ,02 engineering and technology ,Kinetic energy ,01 natural sciences ,Regolith ,0203 mechanical engineering ,Impact crater ,Asteroid ,0103 physical sciences ,Environmental science ,Operational planning ,Two sample ,Aerospace engineering ,business ,Interplanetary spaceflight ,010303 astronomy & astrophysics - Abstract
Hayabusa2 is a Japanese interplanetary probe launched on December 3, 2014, which arrived at asteroid Ryugu on June 27, 2018. During its stay around Ryugu, it completed several challenging operations, including deploying two rovers and a lander, conducting two sample collections, and performing a kinetic impact experiment. The kinetic impact experiment was one of the biggest challenges of the Hayabusa2 mission. Investigating the physical and chemical properties of asteroid internal materials and structures is an important scientific objective for small body exploration. We developed a small kinetic impactor called the SCI (Small Carry-on Impactor) to achieve this objective. The SCI is a compact kinetic impactor designed to remove a small region of Ryugu's uppermost surface regolith layer and create an artificial crater. The spacecraft deployed the SCI on April 5, 2019, successfully creating an artificial crater with a diameter of 15 m. This paper describes the operational planning of the kinetic impact experiment and summarizes the operation results.
- Published
- 2020
14. Hayabusa2 returned samples: A unique and pristine record of outer Solar System materials from asteroid Ryugu
- Author
-
Motoo Ito, Naotaka Tomioka, Masayuki Uesugi, Akira Yamaguchi, Naoki Shirai, Takuji Ohigashi, Ming-Chang Liu, Richard Greenwood, Makoto Kimura, Naoya Imae, Kentaro Uesugi, Aiko Nakato, Kasumi Yogata, Hayato Yuzawa, Yu Kodama, Akira Tsuchiyama, Masahiro Yasutake, Ross Findlay, Ian Franchi, James Malley, Kaitlyn McCain, Nozomi Matsuda, Kevin 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, Tmokatsu 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, and Yuichi Tsuda
- Abstract
C-type asteroids likely formed in the outer Solar System and were then scattered inwards during giant planet migration (Walsh et al., 2011). They may have transported volatiles to the inner Solar System and created the conditions suitable for life on Earth(Alexander, 2017). Carbonaceous chondrites are fragments from C-type asteroids and provide evidence that these generally organic-rich (Garvie and Buseck, 2007) bodies experienced extensive aqueous alteration early in Solar System history (Alexander et al., 2014). On 6th December 2020, ~5.4g of material was delivered to Earth from the C-type asteroid 162173 Ryugu by the Hayabusa2 spacecraft (Yada et al., 2021). Here we present the results of an integrated bulk and micro-analytical study of Ryugu particles, which provides a unique insight into the interrelationship between aliphatic-rich organics and surrounding hydrous minerals at a sub-micrometer scale. This dataset has clear implications for better understanding the origin and early evolution of Solar System organic matter and demonstrates that Ryugu particles are among the most uncontaminated extraterrestrial materials so far studied.
- Published
- 2022
15. Contributors
- Author
-
Masanao Abe, Masahiko Arakawa, Julie Bellerose, Satoshi Danno, Davide Farnocchia, Atsushi Fujii, Kazuhisa Fujita, Naoyuki Fujita, Katsumi Furukawa, Daisuke Goto, Daisuke Hayashi, Hiroki Hihara, Masatoshi Hirabayashi, Chikako Hirose, Tra-Mi Ho, Rie Honda, Satoshi Hosoda, Tsutomu Ichikawa, Hitoshi Ikeda, Ko Ishibashi, Takahiro Ishimaru, Taichi Ito, Toshihiko Kadono, Hideshi Kagawa, Shingo Kameda, Takaaki Kato, Kosuke Kawahara, Shota Kikuchi, Kohei Kitazato, Noboru Kobiki, Toru Kouyama, Kenichi Kushiki, Yusuke Maru, Tetsuya Masuda, Takashi Matsuhisa, Masatoshi Matsuoka, Moe Matsuoka, Kota Matsushima, Keisuke Michigami, Yuya Mimasu, Akira Miura, Osamu Mori, Tomokatsu Morota, Aurelie Moussi, Taiichi Nagata, Junichi Nakatsuka, Satoru Nakazawa, Noriyuki Namiki, Kazutaka Nishiyama, Kenji Oda, Kazunori Ogawa, Naoko Ogawa, Takafumi Ohnishi, Tatsuaki Okada, Yusuke Oki, Go Ono, Takeshi Oshima, Takanao Saiki, Naoya Sakatani, Junpei Sano, Hirotaka Sawada, Shujiro Sawai, Maki Shida, Daisuke Shimada, Takanobu Shimada, Kei Shirai, Stefania Soldini, Seiji Sugita, Shogo Tachibana, Tsuyoshi Takami, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Sho Taniguchi, Hideyuki Tanno, Zahi Tarzi, Elizabeth Tasker, Eri Tatsumi, Fuyuto Terui, Tomoaki Toda, Yuichi Tsuda, Ryudo Tsukizaki, Masashi Uo, Hikaru Uramachi, Stefaan Van Wal, Koji Wada, Sei-ichiro Watanabe, Hikaru Yabuta, Manabu Yamada, Tetsuya Yamada, Tomohiro Yamaguchi, Seiji Yasuda, Yasuhiro Yokota, Keisuke Yoshihara, Kent Yoshikawa, Makoto Yoshikawa, and Koki Yumoto
- Published
- 2022
16. Hayabusa2’s kinetic impact experiment
- Author
-
Takanao Saiki, Hirotaka Sawada, Kazunori Ogawa, Yuya Mimasu, Yuto Takei, Masahiko Arakawa, Toshihiko Kadono, Koji Wada, Atsushi Fujii, Fuyuto Terui, Naoko Ogawa, Go Ono, Kei Shirai, Rie Honda, Ko Ishibashi, Naoya Sakatani, Kent Yoshikawa, Makoto Yoshikawa, Satoru Nakazawa, and Yuichi Tsuda
- Published
- 2022
17. High-resolution observations of bright boulders on asteroid Ryugu: 2. Spectral properties
- Author
-
Moe Matsuoka, Yuichi Tsuda, Patrick Michel, Chisato Okamoto, H. Imamura, Eri Tatsumi, Hidehiko Suzuki, Masahiko Arakawa, Y. Takagi, Hajime Yano, Yosuhiro Yokota, Yuichi Iijima, Kazuo Yoshioka, Tatsuhiro Michikami, Seiji Sugita, Koki Yumoto, Manabu Yamada, Naoya Sakatani, Stefan Schröder, Masahiko Hayakawa, Rie Honda, Kei Shirai, Daniella DellaGiustina, Tomoki Nakamura, Tomokatsu Morota, Chikatoshi Honda, Deborah L. Domingue, Chiho Sugimoto, Satoru Nakazawa, Yuichiro Cho, Toru Kouyama, Minami Aoki, Shingo Kameda, Kazunori Ogawa, Hirotaka Sawada, Takanao Saiki, Takahiro Hiroi, and Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
- Subjects
Earth and Planetary Astrophysics (astro-ph.EP) ,Radiogenic nuclide ,010504 meteorology & atmospheric sciences ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,Spectral properties ,[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Parent body ,Spectral line ,Impact crater ,Space and Planetary Science ,Asteroid ,Chondrite ,[SDU]Sciences of the Universe [physics] ,0103 physical sciences ,Spectroscopy ,010303 astronomy & astrophysics ,Geology ,0105 earth and related environmental sciences ,Astrophysics - Earth and Planetary Astrophysics - Abstract
Many small boulders with reflectance values higher than 1.5 times the average reflectance have been found on the near-Earth asteroid 162173 Ryugu. Based on their visible wavelength spectral differences, Tatsumi et al. (2021) defined two bright boulder classes: C-type and S-type. These two classifications of bright boulders have different size distributions and spectral trends. In this study, we measured the spectra of 79 bright boulders and investigated their detailed spectral properties. Analyses obtained a number of important results. First, S-type bright boulders on Ryugu have spectra that are similar to those found for two different ordinary chondrites with different initial spectra that have been experimentally space weathered the same way. This suggests that there may be two populations of S-type bright boulders on Ryugu, perhaps originating from two different impactors that hit its parent body. Second, the model space-weathering ages of meter-size S-type bright boulders, based on spectral change rates derived in previous experimentally irradiated ordinary chondrites, are 0.1-1 Myr, which is consistent with the crater retention age (, Comment: 21 pages, 20 Figures, 1 Table, Published in Icarus, November 15 2021, 369 114591
- Published
- 2021
18. Effect of boulder size on ejecta velocity scaling law for cratering and its implication for formation of tiny asteroids
- Author
-
Hatsune Okawa, Masahiko Arakawa, Minami Yasui, Sunao Hasegawa, Mizuno Toda, Kei Shirai, and Yuya Yamamoto
- Subjects
Space and Planetary Science ,Impact processes ,Astronomy and Astrophysics ,Regoliths ,Asteroids ,Cratering - Published
- 2022
19. A weak and active surface of Bennu
- Author
-
Masahiko Arakawa
- Subjects
General Earth and Planetary Sciences - Published
- 2022
20. Effect of material strength and heterogeneity on small asteroid cratering events
- Author
-
Patrick Michel, Martin Jutzi, Yun Zhang, Masahiko Arakawa, and Sabina D. Raducan
- Abstract
Keywords: Impact; asteroid surfaces; SSDEM; SPH. Introduction: Impacts can modify the physical state of a substantial fraction of a target body. Studying the hypervelocity impact process and outcome is crucial in the interpretation of the history of a planetary body (Jutzi et al., 2015) and the design of asteroid deflection strategies based on the kinetic impactor technique (Raducan et al., 2019). Images returned by space missions show that small asteroids have complex surface morphologies with heterogeneous distributions of fine regolith and large boulders (e.g., Watanabe et al., 2019). To properly decipher the crater imprints on asteroid surfaces, we carried out numerical investigations to understand the effect of surface material properties (i.e., friction, cohesion) and the presence of large boulders on cratering processes. Methods: We used a hybrid SPH-SSDEM framework to model the high-speed impact cratering (Zhang et al., 2021). The Smooth Particle Hydrodynamics (SPH) is used to simulate the initial shock propagation and fragmentation stage (Jutzi & Michel, 2015). The outcome is then transferred into a Soft-Sphere Discrete Element Method (SSDEM) code (Zhang et al., 2018), which solves the ejecta evolution and crater growth in the later stages. This modeling framework is capable of simulating impacts from the beginning to the later stages when all ejecta are settled down, allowing capturing the final morphology of the resulting crater. To make comparisons with the first impact experiment performed on an asteroid by the Hayabusa2 Small Carry-on Impactor (SCI; Arakawa et al., 2020), we conducted SCI-like cratering tests using the same impact condition (except using an impact angle of 0º) and Ryugu’s gravity field. The target is modeled as a 15-meter-radius granular bed held by a hemispherical ball. The particle-ball contact parameters are the same as those used for particle-particle contacts. Results: As the SCI cratering analyses show consistencies with a very low-strength scaling law (Arakawa et al., 2020), we considered modeling the surface properties with three types of low cohesion (i.e., 0 Pa, 0.01 Pa, and 0.1 Pa) and four types of low to moderate friction angles (20°, 25°, 30°, and 33°). The results show that, in a monotonic manner, the diameter and depth of the resulting crater and rim decrease with a larger friction or cohesion (Fig. 1). Compared with the crater morphology of the SCI impact (i.e., crater diameter 14.5 ± 0.8 m and depth ~2.3 m, rim diameter 17.6 ± 0.7 m and depth 0.4 m), the case with C = 0.1 Pa and
- Published
- 2021
21. Site selection for the Hayabusa2 artificial cratering and subsurface material sampling on Ryugu
- Author
-
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, and Yuichi Tsuda
- Subjects
Space and Planetary Science ,Astronomy and Astrophysics - Published
- 2022
22. Ryugu: A brand-new planetary sample returned from a C-type asteroid
- Author
-
Akiko Miyazaki, Hirotaka Sawada, Hiroshi Naraoka, Lionel Lourit, M. Nishimura, Koki Yumoto, Kentaro Hatakeda, Hajime Yano, Fuyuto Terui, Miwa Yoshitake, Takaaki Noguchi, Shizuho Furuya, Tatsuhiro Michikami, Masahiko Arakawa, Kasumi Yogata, Tatsuaki Okada, Hitoshi Ikeda, Ayako Iwamae, Yuzuru Karouji, Naoyuki Hirata, Hiroshi Takeuchi, Yuri Shimaki, Yayoi N. Miura, Takanao Saiki, Motoo Ito, Aurelie Moussi-Soffys, Koji Matsumoto, Kent Yoshikawa, Hiroki Senshu, Naoko Ogawa, Moe Matsuoka, Yuto Takei, Chikatoshi Honda, Naoya Sakatani, Rosario Brunetto, Hiroshi Kikuchi, Naru Hirata, Yuichiro Cho, Tasuku Hayashi, Kohei Kitazato, Kazuya Kumagai, Yuichi Tsuda, Satoru Nakazawa, Cedric Pilorget, Jean-Pierre Bibring, Yoshiaki Ishihara, Koji Wada, Hirotomo Noda, Satoshi Tanaka, Eizo Nakamura, Shota Kikuchi, Daiki Yamamoto, Hiromichi Soejima, Yuya Hitomi, Tetsuya Yamada, Rina Noguchi, Vincent Hamm, Lucie Riu, Takanobu Shimada, Seiji Sugita, Eri Tatsumi, Shogo Tachibana, Ryota Fukai, Manabu Yamada, Toru Yada, Masanao Abe, Makoto Yoshikawa, Trevor Ireland, Takahiro Iwata, T. Takahashi, Kazunori Ogawa, Damien Loizeau, Noriyuki Namiki, Akira Miura, Aiko Nakato, Katsura Kobayashi, Masaki Fujimoto, Atsushi Fujii, Kei Shirai, Rie Honda, Tomoki Nakamura, Chikako Hirose, Tomohiro Usui, Osamu Mori, Ryuji Okazaki, Yuya Mimasu, Kanako Sakamoto, Yasuhiro Yokota, Yoshinori Takano, Hisayoshi Yurimoto, Sei-ichiro Watanabe, Yuna Yabe, Go Ono, Guillaume Lequertier, Hikaru Yabuta, Tomokatsu Morota, Ryudo Tsukizaki, Masayuki Uesugi, Stefania Soldini, Satoshi Hosoda, Kentaro Uesugi, and Yukio Yamamoto
- Subjects
Asteroid ,Sample (graphics) ,Geology ,Astrobiology - Abstract
C-type asteroids are considered to be primitive small Solar-System bodies enriched in water and organics, providing clues for understanding the origin and evolution of the Solar System and the building blocks of life. C-type asteroid 162173 Ryugu has been characterized by remote sensing and on-asteroid measurements with Hayabusa2, but further studies are expected by direct analyses of returned samples. Here we describe the bulk sample mainly consisting of rugged and smooth particles of millimeter to submillimeter size, preserving physical and chemical properties as they were on the asteroid. The particle size distribution is found steeper than that of surface boulders11. Estimated grain densities of the samples have a peak around 1350 kg m-3, which is lower than that of meteorites suggests a high micro-porosity down to millimeter-scale, as estimated at centimeter-scale by thermal measurements. The extremely dark optical to near-infrared reflectance and the spectral profile with weak absorptions at 2.7 and 3.4 microns implying carbonaceous composition with indigenous aqueous alteration, respectively, match the global average of Ryugu, confirming the sample’s representativeness. Together with the absence of chondrule and Ca-Al-rich inclusion of larger than sub-mm, these features indicate Ryugu is most similar to CI chondrites but with darker, more porous and fragile characteristics.
- Published
- 2021
23. Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu—A spinning top–shaped rubble pile
- Author
-
Paul A. Abell, Eri Tatsumi, Makoto Yoshikawa, Yoshiaki Ishihara, Tomohiro Yamaguchi, Manabu Yamada, Go Ono, Moe Matsuoka, Yuto Takei, Yoshiyuki Tsuda, Sei-ichiro Watanabe, J. P. Bibring, Y. Yokota, Satoshi Tanaka, Kent Yoshikawa, Rina Noguchi, Kohei Kitazato, Goro Komatsu, Koji Wada, Yuri Shimaki, Masaki Fujimoto, Atsushi Fujii, Osamu Mori, Shota Kikuchi, Takahiro Iwata, Takanobu Shimada, H. Ikeda, Masahiko Arakawa, Noriyuki Namiki, Shingo Kameda, Na. Hirata, Robert Gaskell, Shogo Tachibana, Olivier S. Barnouin, T. Takahashi, Naoki Nishikawa, C. Honda, Fuyuto Terui, K. Ogawa, Masahiro Hayakawa, Chikako Hirose, Hikaru Yabuta, Naoya Sakatani, Masatoshi Hirabayashi, Daniel J. Scheeres, Yuichiro Cho, Kei Shirai, Masateru Ishiguro, Hiroshi Takeuchi, Yuya Mimasu, Christian Krause, Hideaki Miyamoto, Tomokatsu Morota, H. Suzuki, Toru Kouyama, Hirotaka Sawada, Tetsuharu Fuse, Ryodo Hemmi, Kosuke Yoshioka, Ryudo Tsukizaki, Yuichi Iijima, M. Ozaki, S. Sugita, Takanao Saiki, Tatsuaki Okada, Stefania Soldini, Ralf Jaumann, Satoru Nakazawa, Naru Hirata, Masanao Abe, Aurelie Moussi, T. M. Ho, A. S. French, Eric Palmer, Jay W. McMahon, Koji Matsumoto, Naoko Ogawa, Satoshi Hosoda, Yukio Yamamoto, T. Sugiyama, R. Honda, Tomoki Nakamura, Hiroki Senshu, Hajime Yano, Tatsuhiro Michikami, Patrick Michel, Hideaki Kikuchi, National Institute of Polar Research [Tokyo] (NiPR), Plasma Research Center, University of Tsukuba, Hiroshima University, Department of Natural History Sciences, Hokkaido University [Sapporo, Japan], Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency [Sagamihara] (JAXA), Institute of Ecology, Tallinn University-Tallinn University, Mitsubishi Research Institute, Inc., Graduate School of Science and Engineering, Tokyo Metropolitan University [Tokyo], Planetary Science Institute [Tucson] (PSI), Service d'hépato-gastro-entérologie [Hôpital Saint-Louis], Groupe Hospitalier Saint Louis - Lariboisière - Fernand Widal [Paris], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP), IHP Microelctronics, Tsukuba Space Center (TKSC), Japan Aerospace Exploration Agency [Tokyo] (JAXA), Department of Physics, Tokyo, Waseda University, Department of Applied Physics, The University of Tokyo, Seoul National University [Seoul] (SNU), Institute for Research on Earth Evolution [Yokosuka] (IFREE), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), National Institute of Advanced Industrial Science and Technology (AIST), Advanced Materials Institute and Department of Chemistry, Fukuoka University, Department of Applied Mathematics and Physics, Graduate school of Mathematics, Kyoto-Kyoyo University, Department of Environmental and Materials Engineering, Nagoya Institute, University of Electro-Communications [Tokyo] (UEC), Institute of Observational Research for Global Change, DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Graduate School of Science and Technology, Keio University, ANR: 15-IDEX-0001,UCA JEDI,Idex UCA JEDI(2015), Department of Earth and Planetary Sciences [Kobe], Kobe University, Institute for Sustainable Humanosphere (RISH), Kyoto University [Kyoto], Department of Geology and Geophysics, USDA Agricultural Research Service [Maricopa, AZ] (USDA), United States Department of Agriculture (USDA), Rikkyo University [Tokyo], Graduate School of Pharmaceutical Sciences, Tohoku, Tohoku University [Sendai], Biomécanique et génie biomédical (BIM), Centre National de la Recherche Scientifique (CNRS), Department of Physics, University of California [Irvine] (UCI), University of California-University of California, University of Alaska [Fairbanks] (UAF), Information Science Laboratory, Dept. of Electronics Engineering, University of Electro-Communication, DLR Institute of Planetary Research, German Aerospace Center (DLR), University of Potsdam, Department of Electronics and Electrical Engineering, Faculty of Science and Technology, Keio University, Hokkaido Information University, Université de Tsukuba = University of Tsukuba, Tallinn University, Tokyo Metropolitan University [Tokyo] (TMU), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Colorado [Boulder], Central Research Institute of Electrical Power Industry, Department of Physics [Tokyo], Department of Applied Physics, University of Fukui, University of Fukui, Tokyo Institute of Technology [Tokyo] (TITECH), and ANR-15-IDEX-0001,UCA JEDI,Idex UCA JEDI(2015)
- Subjects
Multidisciplinary ,010504 meteorology & atmospheric sciences ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,Rubble ,[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] ,Geometry ,engineering.material ,01 natural sciences ,Asteroid ,[SDU]Sciences of the Universe [physics] ,0103 physical sciences ,Homogeneity (physics) ,Cubic centimetre ,engineering ,Sample collection ,Asteroid Ryugu ,Pile ,010303 astronomy & astrophysics ,Spinning ,Slope stability analysis ,Geology ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences ,Hayabusa2 - Abstract
著者人数: 60名 (所属. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS): 渡邊, 誠一郎; 野口, 里奈; 嶌生, 有理; 吉川, 真; 菊地, 翔太; 橘, 省吾; 石原, 吉明; 坂谷, 尚哉; 竹内, 央; 岡田, 達明; 安部, 正真; 山本, 幸生; 田中, 智; 白井, 慶; 松岡, 萌; 横田, 康弘; 山口, 智宏; 尾川, 順子; 三桝, 裕也; 高橋, 忠輝; 竹井, 洋; 藤井, 淳; 岩田, 隆浩; 早川, 雅彦; 細田, 聡史; 森, 治; 澤田, 弘崇; 嶋田, 貴信; Soldini, Stefania; 矢野, 創; 月崎, 竜童; 尾崎, 正伸; 飯島, 祐一; 藤本, 正樹; 照井, 冬人; 佐伯, 孝尚; 中澤, 暁; 津田, 雄一), Accepted: 2019-03-07, 資料番号: SA1180386000
- Published
- 2019
24. Thermally altered subsurface material of asteroid (162173) Ryugu
- Author
-
Kent Yoshikawa, S. Sugita, M. Yoshikawa, Lucie Riu, S. Tanaka, R. Yamada, Takahiro Iwata, Hirotomo Noda, H. Ikeda, M. Abe, H. Suzuki, Takanao Saiki, Hiroshi Takeuchi, Yuichi Iijima, Y. Tsuda, C. Okamoto, Manabu Yamada, Naru Hirata, Masahiko Arakawa, Kazunori Ogawa, Francois Poulet, Shota Kikuchi, Satoru Nakazawa, Go Ono, Satoshi Hosoda, Atsushi Fujii, Osamu Mori, Tsuneo Matsunaga, N. Namiki, C. Honda, M. Ohtake, Rie Honda, K. Yamamoto, Hikaru Yabuta, Davide Perna, M. A. Barucci, Tomoki Nakamura, Driss Takir, Shingo Kameda, Kei Shirai, Yuto Takei, Hajime Yano, Masatoshi Matsuoka, Kosuke Yoshioka, D. L. Domingue, M. Ozaki, Kohei Kitazato, Eri Tatsumi, Kohji Tsumura, Yuichiro Cho, Tatsuaki Okada, Yusuke Nakauchi, Stefania Soldini, Tomohiro Yamaguchi, Rosario Brunetto, Mutsumi Komatsu, Toshihiko Kadono, Ralph E. Milliken, Masateru Ishiguro, A. Miura, Fumi Yoshida, Hiroki Senshu, T. Arai, Ryudo Tsukizaki, T. Mizuno, A. Galiano, Sei-ichiro Watanabe, Yukio Yamamoto, Faith Vilas, Tomokatsu Morota, Koji Matsumoto, Masahiro Hayakawa, J. P. Bibring, Y. Yokota, A. Higuchi, Shuji Matsuura, Naoko Ogawa, Aiko Nakato, Yuya Mimasu, Fuyuto Terui, Chikako Hirose, Yoshiaki Ishihara, Ernesto Palomba, Rina Noguchi, Shinsuke Abe, Takanobu Shimada, Shogo Tachibana, Takahito Osawa, Koji Wada, Y. Takagi, Yuri Shimaki, Takahiro Hiroi, Naoya Sakatani, Naruhisa Takato, C. Pilorget, H. Sawada, T. Takahashi, Toru Kouyama, H. Imamura, Institut d'astrophysique spatiale (IAS), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Materials science ,010504 meteorology & atmospheric sciences ,Mineralogy ,Astronomy and Astrophysics ,01 natural sciences ,Space weathering ,Parent body ,Planetary science ,Meteorite ,Impact crater ,13. Climate action ,Asteroid ,[SDU]Sciences of the Universe [physics] ,0103 physical sciences ,Thermal ,Absorption (electromagnetic radiation) ,010303 astronomy & astrophysics ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences - Abstract
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. Hayabusa2 created an artificial crater on Ryugu to analyse the subsurficial material of the asteroid. Results show that the subsurface is more hydrated than the surface. It experienced alteration processes that can be traced back to Ryugu’s parent body.
- Published
- 2021
25. High-Resolution Observations of Bright Boulders on Asteroid Ryugu: 1. Size Frequency Distribution and Morphology
- Author
-
Yosuhiro Yokota, Minami Aoki, Yuichi Iijima, Tomokatsu Morota, Yuichi Tsuda, Chisato Okamoto, H. Imamura, Koki Yumoto, Moe Matsuoka, Takahiro Hiroi, Manabu Yamada, Y. Takagi, Naoya Sakatani, Hajime Yano, Patrick Michel, Seiji Sugita, Kazuo Yoshioka, Stefan Schröder, Daniella DellaGiustina, Kei Shirai, Hidehiko Suzuki, Masahiko Arakawa, Deborah L. Domingue, Hirotaka Sawada, Tatsuhiro Michikami, Masahiko Hayakawa, Kazunori Ogawa, Satoru Nakazawa, Yuichiro Cho, Chikatoshi Honda, Chiho Sugimoto, Toru Kouyama, Eri Tatsumi, Rie Honda, Tomoki Nakamura, Shingo Kameda, Takanao Saiki, and Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France
- Subjects
Earth and Planetary Astrophysics (astro-ph.EP) ,010504 meteorology & atmospheric sciences ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Albedo ,01 natural sciences ,Power law ,Substrate (marine biology) ,Parent body ,Impact crater ,Space and Planetary Science ,Asteroid ,[SDU]Sciences of the Universe [physics] ,Clastic rock ,0103 physical sciences ,Breccia ,010303 astronomy & astrophysics ,Geology ,0105 earth and related environmental sciences ,Astrophysics - Earth and Planetary Astrophysics - Abstract
The near-Earth asteroid (162173) Ryugu displays a Cb-type average spectrum and a very low average normal albedo of 0.04. Although the majority of boulders on Ryugu have reflectance spectra and albedo similar to the Ryugu average, a small fraction of boulders exhibit anomalously high albedo and distinctively different spectra. A previous study (Tatsumi et al., 2021) based on the 2.7-km observations and a series of low-altitude (down to 68 m) descent observations conducted prior to the first touchdown have shown that the spectra of these anomalous boulders can be classified into two distinct groups corresponding to S and C type asteroids. The former originate most likely from an impactor that collided with Ryugu's parent body, whereas the latter may be from portions of Ryugu's parent body that experienced a different temperature history than experienced by the majority of boulder materials. In this study, we analyzed images captured after the first touchdown to determine the quantitative properties of these bright boulders on Ryugu. We measured the sizes of more than a thousand bright boulders and characterized the morphologic properties of the largest ones. Analyses revealed many properties of bright boulders important for the evolution of Ryugu and its parent body. The size-frequency distributions of S- and C-type bright boulders follow power laws. We obtained the ratios of the total volume and surface area of S-type bright boulders to those of average dark boulders on the Ryugu surface. Also, many of the bright boulders are embedded in a larger substrate boulder, suggesting that they have experienced mixing and conglomeration with darker fragments on the parent body, rather than gently landing on Ryugu during or after its formation by reaccumulation. This is consistent with the hypothesis that S-type bright boulders were likely mixed during and/or before a catastrophic disruption., Comment: 19 pages, 11 figures, 3 Tables, published in Icarus, 369, 15 November, 2021, 114529
- Published
- 2021
- Full Text
- View/download PDF
26. Mission Status of Hayabusa2, Science Highlights, and Outlook for Sample Analyses
- Author
-
Yuichi Tsuda, Masahiko Arakawa, Seiji Sugita, Makoto Yoshikawa, Noriyuki Namiki, Tomokatsu Morota, Rie Honda, Shogo Tachibana, Shingo Kameda, Sei-ichiro Watanabe, Satoshi Tanaka, Eri Tatsumi, Kohei Kitazato, Patrick Michel, Tatsuaki Okada, and Deborah L. Domingue
- Subjects
Medical education ,Geography ,Sample (statistics) - Abstract
JAXA’s Hayabusa2 is a sample-return mission was launched on Dec. 3, 2014 for bringing back first samples from a C-complex asteroid [1,2]. It arrived at asteroid Ryugu on June 27, 2018 and left for Earth on Nov. 13, 2019 after conducting global remote-sensing observations, two touchdown sampling operations, rover deployments, and an artificial impact experiment. We review our science results and update the mission status of Hayabusa2 in this presentation. The global observations revealed that Ryugu has a top-shaped body with very low density (1.19±0.02 g/cc) [3], spatially uniform Cb-type spectra without strong Fe-rich serpentine absorption at 0.7-um [4], and a weak but significant OH absorption at 2.7 um [5]. Based on these observations, we proposed that Ryugu materials may have experienced aqueous alteration and subsequent thermal metamorphism due to radiogenic heating [4]. However, other scenarios, such as impact-induced thermal metamorphism and extremely primitive carbonaceous materials before extensive alteration, were also considered because there were many new properties of Ryugu whose origins are unclear. Also, numerical calculations show that impact heating can raise the temperatures high enough to dehydrate serpentine at typical collision speed in the asteroid main belt [6]. Further analysis using high-resolution data obtained at low-altitude descents for both rehearsal and actual touchdown operations as well as the artificial impact experiment by small carryon impactor (SCI) and landers observations the Ryugu surface on allowed us to find out what caused the properties of Ryugu. For example, subtle but distinct latitudinal variation of spectral slope in optical wavelengths found in the initial observations [4] turned out be caused by solar heating or space weathering during orbital excursion toward the Sun and subsequent erosion of the equatorial ridge owing to slowdown in Ryugu’s spin rate [7]. The SCI impact created a very large (~17 m in crest diameter) crater consistent with gravity-controlled scaling showing that Ryugu surface has very low intra-boulder cohesion and the Ryugu surface is very young and well mixed [8]. Furthermore, the MASCOT lander also showed that typical boulders on Ryugu is not covered with a layer of fine regolith [9] and yet possess very low thermal inertia (282+93/-35 MKS) consistent with highly porous structure [10]. This value is consistent with the global values or Ryugu [4, 11], suggesting that the vast majority of boulders on Ryugu are very porous. However, thermal infrared imager (TIR) also found that Ryugu has a number of “dense boulders” with high thermal inertia (>600 MKS) consistent with typical carbonaceous chondrites, showing that Ryugu’s parent body must have had a large enough gravity and pressure to compress the constituent materials [11]. This observation supports that Ryugu originated from a large parent body, such as proto-Polana and proto-Eulalia, which are estimated to be ~100 km in diameter. Some of the dense boulders were also covered by multi-band images of optical navigation camera (ONC-T) and turned out to have C-type spectra with albedos much higher than the Ryugu average [12]. These spectra and albedos are similar to carbonaceous chondrites heated at low temperatures. Although the total mass of these high-albedo boulders on Ryugu is estimated to be very small (< 1%), the spectral and albedo varieties are much greater than the bulk Ryugu surface and approximately follow the dehydration track of carbonaceous chondrites [12]. These spectral match supports that Ryugu materials experienced aqueous alteration and subsequent thermal metamorphism. The dominance of a high-temperature component and scarcity of lower temperature components are consistent with radiogenic heating in a relatively large parent body because large bodies would have only thin low-temperature thermal skin and large volume of high-temperature interior. If radiogenic heating is really responsible for Ryugu’s moderate dehydration, this may place a very important constraint on the timing of the formation of Ryugu’s parent body. Because the radiogenic heat source for most meteorite parent bodies are likely extinct species, such as 26Al, the peak temperature is chiefly controlled by the timing of accretion [13]. Thus, high metamorphism temperatures (several hundred degrees in Celsius) of Ryugu’s bulk materials inferred from spectral comparison with laboratory heated CM and CI meteorites [4, 12] require Ryugu’s parent body formed early in the Solar System. Because Ryugu’s parent body contained substantial amount of water at the time of formation, it must have been formed outside the snowline. Thus, the birth place of Ryugu’s parent body would be a high-accretion-rate location outside the snowline. Recent high-precision measurements of stable isotopes of meteorites have found that there is a major dichotomy between carbonaceous chondrites (CCs) and some iron meteorites, which formed outside Jupiter’s orbit, and non-carbonaceous meteorites (NCs), which formed inside Jupiter’s orbit [e.g., 14]. If Ryugu belongs to CCs, then Ryugu materials could be form near Jupiter, where accretion could occur early. Thus, measurements of stable isotopes of elements, such as Cr, Ti and Mo, of Ryugu samples to be returned to Earth by the end of 2020 would be highly valuable for constraining the original locations of Polana or Eulalia, among the largest C-complex asteroids in the inner main belt. Acknowledgements: This study was supported by JSPS Core-to-Core program “International Network of Planetary Sciences”, CNES, and Univ. Co?te d’Azur. References: [1] Watanabe et al., SSR, 208, 3-16, 2017. [2] Tsuda et at., Acta Astronaut. 91, 356-363, 2013. [3] Watanabe et al., Science, 364, 268-272, 2019. [4] Sugita et al., Science, 364, eaaw0422, 2019. [5] Kitazato et al., Science, 364, 272-275, 2019. [6] Michel et al., Nature Comm., 11, 5184, 2020. [7] Morota et al., Science, 368, 654-659, 2020. [8] Akarawa et al. Science, 368, 67-671, 2020. [9] Jaumann et al. Science, 365, 817-820, 2019. [10] Grott et al., Nature Astron. 3, 971-976, 2019. [11] Okada et al., Nature, 579, 518-522, 2020. [12] Sugimoto et al. 51st LPSC, #1770, 2020. [13] Grimm and McSween, Science, 259, 653-655, 1993. [14] Kruijer et al., PNAS, 114, 6712-6716, 2017.
- Published
- 2020
27. The effect of 'MASCONS' Sphere Packing onto the Dynamical Environment around Rubble-Pile Asteroids: Application to Ryugu
- Author
-
Takanao Saiki, Koji Wada, Masahiko Arakawa, Hitoshi Ikeda, Yuichi Tsuda, and Stefania Soldini
- Subjects
Sphere packing ,Asteroid ,Rubble ,engineering ,Geometry ,engineering.material ,Pile ,Geology - Abstract
A sphere cluster (SPH-Mas) based gravity model allows a semi-analytic expression of the linearised equations around the equilibrium points. Depending on the sphere packing distribution, the SPH-Mas model can retrieve the same dynamical objects common to others gravity models (i.e. spherical harmonics and polyhedron) or for non-uniform density objects. This model has the advantage to define the same particles mesh distribution for both astrophysical and astrodynamics tools. The Hayabusa2’s Small Carry-on Impactor operation is used as a scenario to study the ejecta particle dynamics around an irregular body. The goNEAR (gravitational orbit Near Earth Asteroid Regions) tool was used to simulate the impact operation in a non-linear sense when the effect of the solar radiation pressure perturbation is taken into account for particles size of 10 cm, 5 cm, 1 cm and 1 mm in diameter. Introduction: In November 2019, the Japanese Hayabusa2 spacecraft completed an 18 months mission exploration around the asteroid Ryugu [1] and it is expected to return to Earth late this year (2020). JAXA’s Hayabusa2 and NASA’s OSIRIS-Rex missions [2] are contributing to answer fundamental questions related to the formation of our solar system and the origin of Life [3]. After a successful touchdown in March 2019, Japan has set a new first when in April 2019 the Hayabusa2 spacecraft deployed and activated the explosive Small Carry-on Impactor (SCI) to successfully form an artificial crater [4]. We propose a genearlised methodology to study the dynamics around Equilibrium Points (EPs) of irregular bodies with application to the asteroid Ryugu [5]. To the core of our study, we aim to gain a general insight on the dynamics around irregular shape bodies for studying the dynamics of ejecta particles. Moreover, we are looking into a generalised gravity model of celestial bodies that can be easily extended not only to any irregular shape bodies but also to arbitrary density distributions [5]. The selected generalised gravity model provides a mass distribution that can be used for both hydrodynamics impact simulations and orbital dynamics around EPs. Background: The mascons (“mas”s “con” centrations) has been mainly used for explaining the Lunar gravity anomalies originally detected in 1968 [6]. Conversely, Smooth Particles Hydrodynamics (SPH) codes are often used to simulate asteroid impact events and share the problem to handle the transition between a SPH simulation and N-body simulations [7]. Since the SPH and Mascons make use of the same mass conservation law and we are interested to interface the SPH simulations with the N-Body simulations, we will rename the selected gravity model as the SPH-Mascons (SPH-Mas) model. Figure 1: Sphere packing and the equilibrium points [5]. SPH-Mas Gravity Model: The gravity of an irregular shape body is modelled with a cluster of spheres, SPH-Mas. Each spherical particle contributes in the overall gravity field of the body. The exterior gravity potential of each sphere behaves as a single point mass. The potential of the irregular body is the result of the summation of each point mass’s potential that contributes to the overall potential field such that: (1) where mi (i = 1, ..., Nsph) is the mass of each SPH-Mas for a total of Nsph masses. r is the distance from the field point and the center of the asteroid. ri is the distance of each masses with respect to the center of the asteroid. The total mass of the asteroid is conserved and given by mb = ∑(i = 1,.., Nsph) mi. Figure 2: Shape model [1] and the equilibrium points. Sphere Packing: We consider Ryugu’s polyhedron model published in [1] as our “high fidelity” gravity model. We distribute the SPH-Mas within the asteroid shape such that we can approximate Ryugu’s “high fidelity” gravity field. For the scope of testing our semi-analytic formula, we compared a uniform sphere packing approach with a random packing approach for different numbers of SPH-Mas. Fig. 1 shows the comparison between the uniform distribution in the left panel and the random distribution in the right panel for Nsph = 19, 58, 1,605 and 1,406,146. By comparing the location of the EPs between Fig 1 and Fig 2, it is clear that under the assumption of uniform density polyhedron, the uniform sphere packing is preferable to the random sphere packing even for the case of Nsph major to the order of million spheres. Indeed, the random sphere packing does not necessarily preserve the geometry of the EPs that affects the ejecta dynamics. Effect of SPH-Mas Packing onto Particles Dynamics: The derived semi-analytical formula based on an SPH-Mas gravity model is a direct function of the sphere packing distribution (density), their position (ri) and the asteroid’s spin axis angular velocity (7.6 h for Ryugu) which allows to find families of periodic orbits for ejecta particles around an non-uniform irregular shaped asteroid as shown in Fig 3. Fate of Ryugu’s Ejecta: We made use of goNEAR tool to simulate the dynamics of 10 cm, 5 cm, 1 cm and 1mm in diameter size particles under the effect of the solar radiation pressure perturbation. In the numerical experiment, few particles seemed to survive in orbit for diameter of 5–10 cm (Fig 4). The search for evidence of particles in Ryugu orbit is still unconfirmed however the stability of EPs can be linked to long survival particles in orbit. Figure 3: Family of periodic orbits as function of sphere packing [5]. Figure 4: SCI’s ejecta dynamics with the goNEAR tool [5]. References: [1] Watanabe et al. (2019) Science, 364, 268–272. [2] Lauretta et al. (2015) Meteoritics & Planet. Sci., 50, 834–849. [3] Sugita et al. (2019) Science, 364, 6437. [4] Arakawa et al. (2019) Science, under review [5] Soldini et al, (2019) PSS, (2020) 180 [6] Melosh et al., (2013) Science, 340,1552–1555 [7] Ballouz et al., (2018) 49th LPSC.
- Published
- 2020
28. An artificial impact on the asteroid (162173) Ryugu formed a crater in the gravity-dominated regime
- Author
-
Yuya Mimasu, Yasuhiro Yokota, Satoru Nakazawa, Hajime Hayakawa, Akira Miura, T. Takahashi, Naoya Sakatani, Sei-ichiro Watanabe, Satoshi Tanaka, Osamu Mori, Yuri Shimaki, Tatsuaki Okada, Martin Jutzi, Stefania Soldini, Shota Kikuchi, Yuichiro Cho, Tomohiro Yamaguchi, Kent Yoshikawa, Hirotaka Sawada, Hajime Yano, Masahiro Hayakawa, Ryudo Tsukizaki, Toshihiko Kadono, H. Imamura, Kei Shirai, Atsushi Fujii, M. Ozaki, Rie Honda, Seiji Sugita, Moe Matsuoka, Yuto Takei, P. Michel, Go Ono, Tomokatsu Morota, Kohei Kitazato, Takanao Saiki, Chikako Hirose, C. Honda, Naoko Ogawa, Fuyuto Terui, Naru Hirata, Ko Ishibashi, Koji Wada, Rina Noguchi, Takanobu Shimada, Shogo Tachibana, Y. Takagi, Shingo Kameda, Masanao Abe, Noriyuki Namiki, Manabu Yamada, Yuichi Tsuda, Eri Tatsumi, Takahiro Iwata, Kazunori Ogawa, Yuichi Iijima, Hiroshi Takeuchi, C. Okamoto, H. Ikeda, Toru Kouyama, S. Kimura, Tomoaki Toda, Kosuke Yoshioka, Masahiko Arakawa, Makoto Yoshikawa, Yukio Yamamoto, Satoshi Hosoda, Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency [Sagamihara] (JAXA), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Gravity (chemistry) ,Multidisciplinary ,010504 meteorology & atmospheric sciences ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] ,Geophysics ,01 natural sciences ,Deposition (aerosol physics) ,Impact crater ,13. Climate action ,Asteroid ,[SDU]Sciences of the Universe [physics] ,0103 physical sciences ,Surface strength ,Ejecta ,010303 astronomy & astrophysics ,Geology ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences - Abstract
Blowing a crater in asteroid Ryugu The Hayabusa2 spacecraft was designed to collect samples from the nearby asteroid (162173) Ryugu and return them to Earth for laboratory analysis. Arakawa et al. describe how the spacecraft's Small Carry-on Impactor was fired into the asteroid's surface, producing an artificial impact crater. Analysis of the resulting plume of ejecta, recorded by a remote camera, sets an upper limit on the strength of the rubble-pile surface. The crater has a semicircular shape, probably due to a large boulder buried close to the impact location. The crater exposed material from Ryugu's subsurface, which has not been subjected to space weathering, that is suitable for collection by Hayabusa2. Science , this issue p. 67
- Published
- 2020
29. Thermal conductivity of lunar regolith simulant JSC-1A under vacuum
- Author
-
Masahiko Arakawa, Kazunori Ogawa, Satoshi Tanaka, and Naoya Sakatani
- Subjects
Materials science ,010504 meteorology & atmospheric sciences ,Planetary surface ,Lunar regolith simulant ,Experimental techniques ,Hydrostatic pressure ,Mineralogy ,Astronomy and Astrophysics ,01 natural sciences ,Regolith ,Grain size ,Thermal conductivity ,Space and Planetary Science ,Asteroid ,0103 physical sciences ,Particle-size distribution ,Moon, surface ,Regoliths ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
Accepted: 2018-02-19, 資料番号: SA1180026000
- Published
- 2018
30. Highly porous nature of a primitive asteroid revealed by thermal imaging
- Author
-
Masanao Abe, Takahiro Iwata, Jens Biele, Kazunori Ogawa, Moe Matsuoka, Yuto Takei, Axel Hagermann, Kent Yoshikawa, Yuichi Tsuda, Takeshi Imamura, Eri Tatsumi, Sei-ichiro Watanabe, Masahiko Arakawa, Kohei Kitazato, Koji Wada, Tomohiro Yamaguchi, Kentaro Suko, Matthias Grott, Tomokatsu Morota, Masateru Ishiguro, Osamu Mori, Ryudo Tsukizaki, Hirotomo Noda, Satoshi Tanaka, Fuyuto Terui, T. Takahashi, Tomohiko Sekiguchi, Kei Shirai, Shota Kikuchi, Masanobu Ozaki, Rie Honda, Hajime Yano, Satoshi Hosoda, Hirohide Demura, Jun Takita, Thomas G. Müller, Hirotaka Sawada, Noriyuki Namiki, Toru Kouyama, Tatsuaki Okada, Yuya Mimasu, Tatsuhiro Michikami, Masahiko Hayakawa, Seiji Sugita, Atsushi Fujii, Tetsuya Fukuhara, Takanao Saiki, Yasuhiro Yokota, Hitoshi Ikeda, Go Ono, Yuri Shimaki, Takehiko Wada, Makoto Yoshikawa, Hikaru Yabuta, Hiroshi Takeuchi, Takehiko Arai, Tsuneo Matsunaga, Hiroki Senshu, Naru Hirata, Yoshiko Ogawa, Chikatoshi Honda, Jörn Helbert, Marco Delbo, Koji Matsumoto, Naoya Sakatani, Naoko Ogawa, Yoshiaki Ishihara, Naoyuki Hirata, Rina Noguchi, Takanobu Shimada, Shogo Tachibana, Chikako Hirose, Maximilian Hamm, Sunao Hasegawa, Manabu Yamada, Yukio Yamamoto, Makoto Taguchi, Satoru Nakazawa, Akira Miura, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Multidisciplinary ,010504 meteorology & atmospheric sciences ,[PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] ,Philosophy ,Ryuku ,Hayabusa ,01 natural sciences ,Regolith ,13. Climate action ,0103 physical sciences ,Highly porous ,Thermisches Infrarot ,010303 astronomy & astrophysics ,Humanities ,0105 earth and related environmental sciences ,Asteroiden - Abstract
International audience; 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 bodies1
- Published
- 2019
31. Dispersion and shattering strength of rocky and frozen planetesimals studied by laboratory experiments and numerical simulations
- Author
-
Masato Nakamura, Minami Yasui, Martin Jutzi, Masahiko Arakawa, Sunao Hasegawa, and Masashi Okazaki
- Subjects
Planetesimal ,Gypsum ,Materials science ,Catastrophic disruption ,530 Physics ,520 Astronomy ,Astronomy and Astrophysics ,Escape velocity ,Radius ,Mechanics ,engineering.material ,620 Engineering ,Impact strength ,Asteroids ,Effective mass (solid-state physics) ,Space and Planetary Science ,engineering ,Planetesimals ,Dispersion (water waves) ,Porosity ,Water content - Abstract
We have developed a method to investigate the whole mass–velocity distribution of impact fragments generated by catastrophic disruption of simulated planetesimals. Flash X-ray radiography including 12 iron particles for tracers was used to visualize the interior of the target, and the velocity distribution of the whole target was estimated by using the velocities of the tracers measured by X-ray images. High-velocity impact experiments in the laboratory and numerical simulations were conducted for four types of targets simulating rocky and frozen planetesimals at various specific energies, Q. These targets consisted of frozen clays with three different water contents ranging from 25 to 45 wt% and porous gypsum with a porosity of 51%. The shattering strength, QS⁎, and the mass–velocity distribution (MVD) were studied for these targets. The QS⁎ of the frozen clays varied by a factor of 3–4 times, depending on the water content, and the QS⁎ for porous gypsum was almost the same as that for the frozen clays with lower water contents. The numerical impact simulations led to slightly different QS⁎ and MVD values for the frozen clay targets, possibly because of the partly ductile behavior of these samples. The MVDs resulting from the porous gypsum targets were well reproduced in the simulations. The cumulative mass of fragments with an ejection velocity slower than a specific velocity was examined to introduce a median velocity, v⁎, charactering the mass–velocity distribution. The v⁎ is defined as the velocity at which the cumulative mass corresponds to a half of the original target mass in the distribution. The v⁎ values of the frozen clays were described by the empirical equation v∗ = e Qγ with almost the same e and γ, irrespective of the water content, but the v⁎ of porous gypsum was about 1/3 that of the frozen clays. These experimental results were well reproduced by the numerical simulations for both frozen clays and porous gypsum targets. The dispersion strength, QD⁎, could be derived by comparing v⁎ with the escape velocity, vesc, of a target body with an effective mass, M, and radius, R. From this, a semi-theoretical equation showing the dispersion strength was derived: Q D ∗ = 1 e 2 GM R 1 / 2 1 / γ . Numerical simulations of catastrophic disruptions including self-gravity were conducted to directly determine QD⁎ at large scale. These calculations showed that the effective mass of the target body, which is used in the computation of vesc = v⁎, should be a half of the original target mass, M = Mtarget /2. Our results suggest that this approach for computing the semi-theoretical dispersion strength is suitable for bodies larger than ~10 km.
- Published
- 2021
32. Tensile strength and elastic properties of fine-grained ice aggregates: Implications for crater formation on small icy bodies
- Author
-
Yuri Shimaki and Masahiko Arakawa
- Subjects
Empirical equations ,Ultrasonic pulse velocity ,Impact crater ,Space and Planetary Science ,Filling factor ,Ultimate tensile strength ,Uniaxial tension ,Astronomy and Astrophysics ,Composite material ,Snow - Abstract
The mechanical and elastic properties of ice aggregates are important in the physics of avalanches and crater formation on icy bodies, such as icy satellites and cometary nuclei. Here we conducted uniaxial tensile tests and elastic-wave velocity measurements on artificial fine-grained ice aggregates (snow) to infer the potential for crater formation on small icy bodies. The uniaxial tensile tests on the artificial snow with filling factors ( f ) in the 0.30–0.59 range at −15 °C demonstrate that the tensile strength ( Y t ) depends on its filling factor; we obtained the empirical equation Y t = 1 0 3 . 5 f 3 . 5 (in kPa) based on our results, which is consistent with the upper limit of natural snow’s tensile strength. The compressional- and shear-wave velocities of artificial snow with f ≥ 0.4 were measured via the ultrasonic pulse velocity method. The elastic-wave velocities decrease linearly with decreasing f values. Our calculations for the Young’s moduli of the artificial snow from the elastic-wave velocity measurements are 10–40 times higher than those from the tensile tests, which indicate the rate-dependent properties of the fine-grained ice aggregates. We propose a tensile strength estimation of a cometary surface via an artificial impact based on our results and a crater-scaling law in the strength-dominated regime.
- Published
- 2021
33. Resurfacing processes on asteroid (162173) Ryugu caused by an artificial impact of Hayabusa2's Small Carry-on Impactor
- Author
-
Kazuo Yoshioka, Naoyuki Hirata, Kazunori Ogawa, Rie Honda, Yuichi Tsuda, Kei Shirai, Chisato Okamoto, Moe Matsuoka, Takanao Saiki, Hirotaka Sawada, Shingo Kameda, Hidehiko Suzuki, Ko Ishibashi, Masahiko Arakawa, Eri Tatsumi, Yuri Shimaki, Yu ichi Iijima, Manabu Yamada, H. Imamura, Seiji Sugita, Y. Takagi, Hajime Yano, Naru Hirata, Minami Yasui, Yasuhiro Yokota, Masahiko Hayakawa, Toru Kouyama, Naoya Sakatani, Chikatoshi Honda, Yuichiro Cho, Toshihiko Kadono, Koji Wada, Satoru Nakazawa, and Tomokatsu Morota
- Subjects
010504 meteorology & atmospheric sciences ,Astronomy and Astrophysics ,Radius ,Surface gravity ,01 natural sciences ,Seismic wave ,Acceleration ,Impact crater ,Space and Planetary Science ,Asteroid ,0103 physical sciences ,Ejecta blanket ,Ejecta ,010303 astronomy & astrophysics ,Geology ,Seismology ,0105 earth and related environmental sciences - Abstract
The resurfacing process on Ryugu accompanying the artificial impact crater formation by Hayabusa2's Small Carry-on Impactor (SCI) was studied by comparing pre- and post-impact images of this region captured by an optical navigation camera. Three different aspects of the resurfacing process were examined: the crater rim profiles, the motion of boulders and the appearance of new boulders, and the motion vectors of Ryugu's surface around the SCI crater. The averaged crater rim height, h, was derived as follows: h = hr exp [−(r/Rrim − 1)/λrim], where Rrim is the SCI crater rim radius of 8.8 m, the fitted parameter, hr, is 0.475 m, and the λrim is 0.245. The ejecta blanket thickness of the SCI crater was thinner than that estimated from both the observation of natural craters and the crater formation theory. However, this discrepancy of the ejecta blanket thickness was resolved by taking into account the new boulders appearing in the post-impact images in the volume. The motion of the discovered boulders could be classified by its mechanisms as follows: a dragging motion created by excavation flow during the crater formation, a pushing motion created by falling-back ejecta, a dragging motion created by the slight motion of the Okamoto boulder, and a motion caused by seismic shaking induced by the SCI impact itself. The seismic shaking caused boulders to move farther than 3 cm from the original site in most of the region within 15 m distance from the SCI crater center, where the maximum acceleration of the impact induced seismic waves 7 times larger than the surface gravity of Ryugu based on the laboratory experiments (Matsue et al. [2020] Icarus, 338, 113520), and the evidence of the seismic shaking for boulders with a movement of >3 cm was detected in about 10% of the boulders in the region between 15 m and 30 m from the crater center, which region was inferred to experience acceleration larger than the Ryugu's surface gravity based on previous laboratory experiments (Matsue et al. [2020] Icarus, 338, 113520).
- Published
- 2021
34. Impacts may provide heat for aqueous alteration and organic solid formation on asteroid parent bodies
- Author
-
Ryohei Hashimoto, Minami Yasui, Masahiko Arakawa, Kazunori Ogawa, and Taku Tazawa
- Subjects
Materials science ,010504 meteorology & atmospheric sciences ,Astronomical unit ,Radius ,Thermal diffusivity ,01 natural sciences ,Astrobiology ,law.invention ,Impact crater ,Asteroid ,Thermocouple ,law ,0103 physical sciences ,Light-gas gun ,General Earth and Planetary Sciences ,010303 astronomy & astrophysics ,Radioactive decay ,0105 earth and related environmental sciences ,General Environmental Science - Abstract
Chemical reactions on asteroid parent bodies, such as aqueous alteration and the formation of organic solids, require a heat source. Radioactive decay in the interiors of these bodies is generally considered the most important heat source, but impact-generated heating is also likely to play a role. Here we present high-velocity impact cratering experiments using thermocouples embedded in the target material to directly measure the spatial and temporal evolution of temperature throughout each impact experiment. We find that the maximum temperature below the crater floor scales with the distance from the impact point, while the duration of temperature rise is scaled by the thermal diffusion time. We use numerical modelling to suggest that, at distances within 2 astronomical units, impacts producing craters of >20 km radius can facilitate aqueous alteration in the material below the crater, while those which produce craters of 1 km radius can support organic solid formation. Impact heating on asteroid parent bodies may be sufficient to facilitate aqueous alteration and the generation of solid organic material in the region below the impact crater floor, according to direct experiments using a two-stage light gas gun.
- Published
- 2021
35. Drag on a body moving through snow
- Author
-
Gaku MATSUMOTO, Masahiko ARAKAWA, and Norikazu MAENO
- Published
- 2017
36. Performance of Hayabusa2 DCAM3-D Camera for Short-Range Imaging of SCI and Ejecta Curtain Generated from the Artificial Impact Crater Formed on Asteroid 162137 Ryugu (1999 JU 3 $\mbox{JU}_{3}$ )
- Author
-
K. Shirai, Masahiko Arakawa, Kazunori Ogawa, Rie Honda, Y. Ikeda, Naoya Sakatani, Koji Wada, and Ko Ishibashi
- Subjects
010504 meteorology & atmospheric sciences ,Spacecraft ,business.industry ,Astronomy and Astrophysics ,01 natural sciences ,Optics ,Planetary science ,Impact crater ,Space and Planetary Science ,Asteroid ,0103 physical sciences ,Radiance ,Calibration ,Image sensor ,Ejecta ,business ,010303 astronomy & astrophysics ,Geology ,0105 earth and related environmental sciences ,Remote sensing - Abstract
Deployable Camera 3-D (DCAM3-D) is a small high-resolution camera equipped on Deployable Camera 3 (DCAM3), one of the Hayabusa2 instruments. Hayabusa2 will explore asteroid 162137 Ryugu (1999 JU3) and conduct an impact experiment using a liner shooting device called Small Carry-on Impactor (SCI). DCAM3 will be detached from the Hayabusa2 spacecraft and observe the impact experiment. The purposes of the observation are to know the impact conditions, to estimate the surface structure of asteroid Ryugu, and to understand the physics of impact phenomena on low-gravity bodies. DCAM3-D requires high imaging performance because it has to image and detect multiple targets of different scale and radiance, i.e., the faint SCI before the shot from 1-km distance, the bright ejecta generated by the impact, and the asteroid. In this paper we report the evaluation of the performance of the CMOS imaging sensor and the optical system of DCAM3-D. We also describe the calibration of DCAM3-D. We confirmed that the imaging performance of DCAM3-D satisfies the required values to achieve the purposes of the observation.
- Published
- 2016
37. The Small Carry-on Impactor (SCI) and the Hayabusa2 Impact Experiment
- Author
-
Y. Takagi, Hajime Yano, Masahiko Hayakawa, Takanao Saiki, Koji Wada, Kei Shirai, H. Imamura, Chisato Okamoto, and Masahiko Arakawa
- Subjects
Shaped charge ,010504 meteorology & atmospheric sciences ,Explosive material ,01 natural sciences ,Artificial crater ,Astrobiology ,Small carry-on impactor ,Sample return mission ,Impact crater ,0103 physical sciences ,Aerospace engineering ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,Scientific instrument ,Impact experiment ,business.industry ,Asteroid exploration ,Astronomy and Astrophysics ,Regolith ,Space and Planetary Science ,Asteroid ,business ,Guidance system ,Geology ,Hayabusa2 - Abstract
Accepted: 2016-10-03, 資料番号: SA1160287000
- Published
- 2016
38. Experimental study concerning the oblique impact of low- and high-density projectiles on sedimentary rocks
- Author
-
Erine Taguchi, Sayaka Tsujido, Yasunari Koumoto, Shunya Harada, Ko Ishibashi, Akiko M. Nakamura, Sunao Hasegawa, Masahiko Arakawa, Makoto Tabata, Ayako I. Suzuki, Hideki Tamura, Kosuke Kurosawa, Yoichi Fujita, Masato Kiuchi, Seiji Sugita, Sae Shigaki, Tomomi Omura, Eri Matsumoto, Toshihiko Kadono, and Takayuki Hirai
- Subjects
010504 meteorology & atmospheric sciences ,Projectile ,Astronomy and Astrophysics ,Geometry ,01 natural sciences ,Brittleness ,Impact crater ,Volume (thermodynamics) ,Meteorite ,Space and Planetary Science ,0103 physical sciences ,Sedimentary rock ,Hydraulic diameter ,010303 astronomy & astrophysics ,Scaling ,Geology ,0105 earth and related environmental sciences - Abstract
We conducted four sets of impact experiments using sedimentary rock targets and three different kinds of projectiles at a variety of impact angles in order to examine how the density of a projectile affects the dimensions of a crater as the angle of impact decreases, the threshold angle for the formation of elliptical craters, and the threshold angle for the formation of pits. The crater profiles, crater volume, equivalent diameter, length, width, depth, and ellipticity of each set were carefully measured to be used in comparison with small craters that formed on the weak rocky surfaces of planetary bodies. The results indicate that the crater volume, equivalent diameter, width, and depth decrease with the impact angle, while the length of the crater within a set does not decrease monotonically with impact angle. This trend in crater length is consistent with the results of previous studies. Although craters formed at higher impact angles have a central pit, the pit becomes unclear and eventually disappears as the impact angle decreases. A larger threshold angle is required for the formation of pits at slower impact velocity than at higher impact velocity. Our results suggest that the presence of a central pit is indicative of impacts at higher angles and/or higher velocity. The ratio of the volume of craters resulting from oblique impacts to that of craters formed by normal impacts was proportional to the power of the sine of the impact angle. The power index was found to range between 1.46 and 2.20, with an average of 1.57. Comparison of the averaged power index to the power index of the π-group crater scaling rules, it is experimentally suggested that the hypothesis indicating that the vertical velocity component controls crater formation is plausible on a brittle target. The threshold angles for the formation of elliptical craters for three different kind of projectiles were almost consistent with those obtained in previous studies. Our results strongly suggested that the threshold angle for the formation of elliptical craters for high-density impactor, such as iron meteorites, are higher than for rocky impactors. We then obtained a relationship between the threshold angle for the formation of pits and the cratering efficiency. It is revealed that the threshold angle for the formation of pits is greater than the threshold angle for the formation of elliptical craters, when the cratering efficiency is in the range 7–30. A well-developed pit-spall structure in the crater may be used to indicate both, the impact angle and the vertical component of the impact velocity.
- Published
- 2021
39. Recovery of entire shocked samples in a range of pressure from ~100 GPa to Hugoniot elastic limit
- Author
-
Tadashi Kondo, Toshihiko Kadono, Yoichiro Hironaka, Keisuke Shigemori, T. Sakaiya, Masahiko Arakawa, Keita Nagaki, and Kosuke Kurosawa
- Subjects
Earth and Planetary Astrophysics (astro-ph.EP) ,Diffraction ,Materials science ,010504 meteorology & atmospheric sciences ,Opacity ,Scanning electron microscope ,Analytical chemistry ,FOS: Physical sciences ,Electron ,Laser ,01 natural sciences ,law.invention ,Shock (mechanics) ,Crystal ,Geophysics ,Space and Planetary Science ,law ,0103 physical sciences ,010303 astronomy & astrophysics ,Quartz ,Astrophysics - Earth and Planetary Astrophysics ,0105 earth and related environmental sciences - Abstract
We carried out laser shock experiments and wholly recovered shocked olivine and quartz samples. We investigated the petrographic features based on optical micrographs of sliced samples and found that each recovered sample comprises three regions, I (optically dark), II (opaque) and III (transparent). Scanning electron microscopy combined with electron back-scattered diffraction shows that there are no crystal features in the region I; the materials in the region I have once melted. Moreover, numerical calculations performed with the iSALE shock physics code suggest that the boundary between regions II and III corresponds to Hugoniot Elastic Limit (HEL). Thus, we succeeded in the recovery of the entire shocked samples experienced over a wide range of pressures from HEL (~ 10 GPa) to melting pressure (~ 100 GPa) in a hierarchical order., 53 pages, 11 figures, 4 tables, accepted for publication in Meteoritics and Planetary Science
- Published
- 2016
40. Compressional stress effect on thermal conductivity of powdered materials: Measurements and their implication to lunar regolith
- Author
-
Satoshi Tanaka, Naoya Sakatani, Yuichi Iijima, Kazunori Ogawa, and Masahiko Arakawa
- Subjects
Materials science ,010504 meteorology & atmospheric sciences ,Lunar regolith simulant ,Experimental techniques ,Astronomy and Astrophysics ,Context (language use) ,Conductivity ,Thermal conduction ,01 natural sciences ,Regolith ,Thermal conductivity ,Space and Planetary Science ,0103 physical sciences ,Moon, surface ,Radiative transfer ,Regoliths ,Composite material ,010303 astronomy & astrophysics ,Electrical conductor ,0105 earth and related environmental sciences - Abstract
Accepted: 2015-12-09, 資料番号: SA1150218000
- Published
- 2016
41. Ejecta velocity distribution of impact craters formed on quartz sand: Effect of projectile density on crater scaling law
- Author
-
Minami Yasui, Sayaka Tsujido, Masahiko Arakawa, and Ayako I. Suzuki
- Subjects
Physics ,Point source ,Projectile ,Impact processes ,Asteroids, surfaces ,Astronomy and Astrophysics ,Geometry ,Radius ,Gravitational acceleration ,law.invention ,Classical mechanics ,Impact crater ,Space and Planetary Science ,law ,Light-gas gun ,Regoliths ,Ejecta ,Quartz ,Cratering - Abstract
Accepted: 2015-08-27, 資料番号: SA1150176000
- Published
- 2015
42. Impact Experiment on Asteroid (162173) Ryugu: Structure beneath the Impact Point Revealed by In Situ Observations of the Ejecta Curtain
- Author
-
Seiji Sugita, Kazunori Ogawa, Toshihiko Kadono, Rie Honda, Ko Ishibashi, Masahiko Arakawa, Kei Shirai, Hirotaka Sawada, Naoya Sakatani, Koji Wada, and Yuri Shimaki
- Subjects
In situ ,Physics ,Planetary science ,Space and Planetary Science ,Asteroid ,Astronomy and Astrophysics ,Point (geometry) ,Ejecta ,Astrobiology - Published
- 2020
43. Measurements of seismic waves induced by high-velocity impacts: Implications for seismic shaking surrounding impact craters on asteroids
- Author
-
Kazuma Matsue, Minami Yasui, Sunao Hasegawa, and Masahiko Arakawa
- Subjects
010504 meteorology & atmospheric sciences ,Projectile ,Experimental techniques ,Impact processes ,Astronomy and Astrophysics ,Radius ,Kinetic energy ,01 natural sciences ,Regolith ,Asteroids ,Seismic wave ,Acceleration ,Impact crater ,Asteroids surfaces ,Space and Planetary Science ,Asteroid ,0103 physical sciences ,010303 astronomy & astrophysics ,Geology ,Seismology ,Cratering ,0105 earth and related environmental sciences - Abstract
On asteroids, impact-induced seismic shaking is an important geological process related to the modifications of the surface features that are due to the movement of regolith grains on the asteroid surface. Mass movements caused by seismic shaking (e.g., landslides and crater erasures) were recently observed by several spacecrafts. To elucidate the seismic shaking areas induced by impacts on asteroids, it is necessary to determine the excitation and the decay processes of impact-induced seismic waves. Here we conducted impact cratering experiments using 500-μm quartz sand to simulate an asteroid surface at the Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA). We used 4.75-mm- and 2-mm-diameter projectiles with density from 14.9 to 1.2 g cm−3; the impact velocity ranged from 7 to 0.2 km s−1. We measured the acceleration waveform by using three to five accelerometers setting on the target surface, and we examined three parameters characterizing the impact-induced seismic wave with varying distances from the impact point: the propagation velocity (Vprop), the maximum acceleration (gmax), and the half period of the first upward peak (Thalf). The Vprop was obtained to be 52.4 ± 7.2 m s−1, regardless of the impact velocity and the projectile properties, and the Thalf slightly depended on the impact velocity as v i 0.14 but was independent of the projectile properties. The gmax had a close relationship with the distance from the impact point normalized by the crater rim radius, x/Rrim, regardless of the impact velocity and the projectile properties. The obtained empirical equation was shown as gmax = 102.21(x/Rrim)−3.18. By using the empirical equations we obtained herein, we observed that the seismic energy normalized by the kinetic energy of a projectile, Es/Ek, decreased with the increase of the normalized distance, x/Rrim. We also estimated the area of impact-induced seismic shaking on an idealized small (500 m in diameter) body at the impact velocity of 5 km s−1.
- Published
- 2020
44. Effects of oblique impacts on the impact strength of porous gypsum and glass spheres: Implications for the collisional disruption of planetesimals in thermal evolution
- Author
-
Masahiko Arakawa, Kazuma Matsue, Minami Yasui, Shota Takano, and Yusaku Yoshida
- Subjects
Total internal reflection ,Materials science ,Gypsum ,010504 meteorology & atmospheric sciences ,Projectile ,Collisional physics ,Impact processes ,Astronomy and Astrophysics ,Izod impact strength test ,engineering.material ,01 natural sciences ,Space and Planetary Science ,visual_art ,0103 physical sciences ,visual_art.visual_art_medium ,engineering ,Specific energy ,SPHERES ,Composite material ,Polycarbonate ,Planetesimals ,Porosity ,010303 astronomy & astrophysics ,Planetary formation ,0105 earth and related environmental sciences - Abstract
We conducted oblique impact experiments for porous gypsum spheres and glass spheres simulating primitive and consolidated rocky planetesimals, respectively, and we determined the effects of the impact angle on the impact strength of these rocky planetesimals. The targets were a porous gypsum sphere with a porosity of 50% and a glass sphere without porosity. A spherical polycarbonate projectile impacted the target at 2–7 km s−1 at an impact angle, θ, ranging from 90° (head-on collision) to 10° (grazing collision) by using a two-stage light-gas gun at Kobe University, Japan. The impact strength obtained at a head-on collision was 1330 J kg−1 for the porous gypsum target and 1090 J kg−1 for the glass target, and these values increased markedly with the decrease of the impact angle when the impact angle was smaller than a critical angle, θc; the obtained θc values were 30° for the porous gypsum target and 55° for the glass target. The normalized largest fragment mass (ml/Mt) showed a good correlation with an effective specific energy (Qeff = Qsin2θ); the subsequent empirical equation was m l / M t = 10 2.02 Q eff 0.76 for the porous gypsum target and m l / M t = 10 4.66 Q eff 1.68 at ml/Mt m l / M t = 10 0.12 Q eff 0.08 at ml/Mt >0.75 for the glass target. Based on our experimental results, we successfully introduce the effects of an oblique impact on the degree of disruption for primitive and consolidated rocky planetesimals. Our findings demonstrate that in a strength-dominated regime, the catastrophic disruption can occur over a wide range of impact angles (30°–90°) irrespective of the target materials, when the specific energy at the collision is about four times larger than the impact strength.
- Published
- 2020
45. Crater-ray Formation by Impact-Induced Ejecta Particles
- Author
-
Koji Wada, Satoru Yamamoto, Seiji Sugita, Junichi Haruyama, Masahiko Arakawa, Ayako I. Suzuki, Toshihiko Kadono, Akiko M. Nakamura, and Noriko K. Mitani
- Subjects
Physics ,Lunar craters ,Characteristic length ,Impact processes ,Collisional physics ,Inelastic collision ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Granular material ,Impact crater ,Space and Planetary Science ,Planet ,Moon, surface ,Astrophysics::Earth and Planetary Astrophysics ,Ejecta ,Cratering - Abstract
Accepted: 2014-11-24, 資料番号: SA1004981000
- Published
- 2015
46. System Configuration and Operation Plan of Hayabusa2 DCAM3-D Camera System for Scientific Observation During SCI Impact Experiment
- Author
-
Kazunori Ogawa, Kei Shirai, Hirotaka Sawada, Masahiko Arakawa, Rie Honda, Koji Wada, Ko Ishibashi, Yu-ichi Iijima, Naoya Sakatani, Satoru Nakazawa, and Hajime Hayakawa
- Subjects
010504 meteorology & atmospheric sciences ,0103 physical sciences ,010303 astronomy & astrophysics ,01 natural sciences ,0105 earth and related environmental sciences - Published
- 2017
47. Impacts experiments onto heterogeneous targets simulating impact breccia: Implications for impact strength of asteroids and formation of the asteroid families
- Author
-
Masahiko Arakawa and Jacek Leliwa-Kopystynski
- Subjects
Space and Planetary Science ,Asteroid ,Breccia ,Compaction ,Specific energy ,Astronomy and Astrophysics ,Izod impact strength test ,Petrology ,Laboratory results ,Collision ,Geology ,Astrobiology - Abstract
A series of impact experiments onto solid decimeter-sized cylinders made of porous gypsum admixed with approximately 1 cm-sized pebbles have been performed. The target densities and their heterogeneous structures could be representative of those of the asteroids Ida, Eros and many others, because asteroid sub-surface could be the consolidated boulders made by self-compaction and/or by impact compaction. Impact velocities in the experiments ranged from 2.0 km/s to 6.7 km/s (collision velocity in the asteroid main belt is approximately 5 km/s). It was found that the slope of the cumulative number distribution of post-impact fragments strongly depends on the specific energy of the impact. The presence of pebbles strongly influences the impact strength of the target as well as the size distribution of the post-impact fragments. Results of the experiments presented here are aimed at identifying the analogy between the laboratory results and the damage of small asteroids or their catastrophic disruption after impacts.
- Published
- 2014
48. Impact strength of small icy bodies that experienced multiple collisions
- Author
-
Ryo Hayama, Minami Yasui, and Masahiko Arakawa
- Subjects
Physics ,Solar System ,Projectile ,Astronomy and Astrophysics ,Izod impact strength test ,Single impact ,Atmospheric sciences ,law.invention ,Ejection velocity ,Impact crater ,Space and Planetary Science ,law ,Light-gas gun ,Energy density ,Atomic physics - Abstract
Frequent collisions are common for small bodies in the Solar System, and the cumulative damage to these bodies is thought to significantly affect their evolution. It is important to study the effects of multiple impacts such as the number of impacts on the impact strength and the ejection velocity of impact fragments. Here we conducted multiple-impact experiments using a polycrystalline water ice target, varying the number of impacts from 1 to 10 times. An ice cylindrical projectile was impacted at 84–502 m s −1 by using a single-stage gas gun in a cold room between −10 and −15 °C. The impact strength of the ice target that experienced a single impact and multiple impacts is expressed by the total energy density applied to the same target, Σ Q , and this value was observed to be 77.6 J kg −1 . The number of fine impact fragments at a fragment mass normalized by an initial target mass, m / M t0 ∼ 10 −6 , n m , had a good correlation with the single energy density at each shot, Q j , and the relationship was shown to be n m = 10 1.02 ± 0.22 · Q j 1.31 ± 0.12 . We also estimated the cumulative damage of icy bodies as a total energy density accumulated by past impacts, according to the crater scaling laws proposed by Housen et al. (Housen, K.R., Schmidt, R.M., Holsapple, K.A. [1983]. J. Geophys. Res. 88, 2485–2499) of ice and the crater size distributions observed on Phoebe, a saturnian icy satellite. We found that the cumulative damage of Phoebe depended significantly on the impact speed of the impactor that formed the craters on Phoebe; and the cumulative damage was about one-third of the impact strength Σ Q * at 500 m s −1 whereas it was almost zero at 3.2 km s −1 .
- Published
- 2014
49. High-Velocity Impact Phenomena in the Solar System Related to the Origin and Evolution of Planets
- Author
-
Yuri Shimaki, Masahiko Arakawa, and Minami Yasui
- Subjects
Planetesimal ,Solar System ,Scaling law ,Impact crater ,Planet ,Asteroid ,High velocity ,General Materials Science ,General Chemistry ,Condensed Matter Physics ,Geology ,Astrobiology - Published
- 2014
50. A formation mechanism for concentric ridges in ejecta surrounding impact craters in a layer of fine glass beads
- Author
-
Satoru Yamamoto, Masahiko Arakawa, Ayako I. Suzuki, Toshihiko Kadono, Akiko M. Nakamura, and Koji Wada
- Subjects
geography ,geography.geographical_feature_category ,Atmospheric pressure ,Projectile ,Astronomy and Astrophysics ,Mechanics ,Wake ,Impact crater ,Space and Planetary Science ,Drag ,Ridge ,Ejecta ,Geology ,Ambient pressure - Abstract
Ejecta patterns are experimentally examined around craters formed in a layer of glass beads by vertical impacts at low velocities. The diameters of the constituent glass beads of three different targets range 53–63 μm, 90–106 μm, and 355–500 μm. The impact velocities and ambient pressures range from a few to 240 m s−1 and from 500 Pa to the atmospheric pressure, respectively. Various ejecta patterns are observed around craters and are classified into two major classes based on whether they have concentric ridges or not. We propose a possible formation model for the ridges in which the wake created by a projectile as it passes through the atmosphere causes the crater rim to collapse: The model can explain the observation that the degree of collapse of the resultant crater rim depends on the impact velocity and ambient pressure. Using the ratio between the hydrodynamic drag of the airflow induced by the wake and the gravitational force of the degraded part of the rim, we calculate the critical conditions of the impact velocity and ambient pressure necessary for the wake to erode the rim. The conditions turn out to be roughly consistent with the boundary between the two morphological classes. As a result, it is possible that the projectile wake triggers the collapse of the crater rim, leading to a ground-hugging flow that settles to form the distal ridge observed in this study. This mechanism may play a role in producing ejecta morphologies on planetary bodies with atmosphere.
- Published
- 2013
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.