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dc.contributor.authorOkada, Tatsuakien_UK
dc.contributor.authorFukuhara, Tetsuyaen_UK
dc.contributor.authorTanaka, Satoshien_UK
dc.contributor.authorTaguchi, Makotoen_UK
dc.contributor.authorArai, Takehikoen_UK
dc.contributor.authorSenshu, Hirokien_UK
dc.contributor.authorSakatani, Naoyaen_UK
dc.contributor.authorShimaki, Yurien_UK
dc.contributor.authorDemura, Hirohideen_UK
dc.contributor.authorOgawa, Yoshikoen_UK
dc.contributor.authorSuko, Kentaroen_UK
dc.contributor.authorSekiguchi, Tomohikoen_UK
dc.contributor.authorKouyama, Toruen_UK
dc.contributor.authorTakita, Junen_UK
dc.contributor.authorHagermann, Axelen_UK
dc.description.abstractCarbonaceous (C-type) asteroids 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 chondrites 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) onboard the spacecraft Hayabusa2, 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 chondrites 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 effect. 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 chondrites. These results constrain the formation history of Ryugu: the asteroid must be a rubble pile formed from impact fragments of a parent body with microporosity 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 bodies.en_UK
dc.publisherSpringer Science and Business Media LLCen_UK
dc.relationOkada T, Fukuhara T, Tanaka S, Taguchi M, Arai T, Senshu H, Sakatani N, Shimaki Y, Demura H, Ogawa Y, Suko K, Sekiguchi T, Kouyama T, Takita J & Hagermann A (2020) Highly porous nature of a primitive asteroid revealed by thermal imaging. Nature, 579 (7800), p. 518–522.
dc.rightsThis item has been embargoed for a period. During the embargo please use the Request a Copy feature at the foot of the Repository record to request a copy directly from the author. You can only request a copy if you wish to use this work for your own research or private study. Publisher policy allows this work to be made available in this repository. Published in Nature by SpringerNature. The original publication is available at: Springer Nature company holds copyright, users may view, print, copy, download and text and data-mine the content, for the purposes of academic research, subject always to the full conditions of use. Any further use is subject to permission from Springer Nature. The conditions of use are not intended to override, should any national law grant further rights to any user.en_UK
dc.subjectAsteroids, comets and Kuiper belten_UK
dc.subjectEarly solar systemen_UK
dc.titleHighly porous nature of a primitive asteroid revealed by thermal imagingen_UK
dc.typeJournal Articleen_UK
dc.rights.embargoreason[Okada_et_al_Porous-Nature-of-Asteroid_accepted_15dec.pdf] Publisher requires embargo of 6 months after formal publication.en_UK
dc.type.statusAM - Accepted Manuscripten_UK
dc.contributor.funderSTFC Science & Technology Facilities Councilen_UK
dc.description.notesAdditional co-authors: Tsuneo Matsunaga, Takeshi Imamura, Takehiko Wada, Sunao Hasegawa, Jörn Helbert, Thomas G. Müller, Jens Biele, Matthias Grott, Maximilian Hamm, Marco Delbo, Naru Hirata, Naoyuki Hirata, Yukio Yamamoto, Seiji Sugita, Noriyuki Namiki, Kohei Kitazato, Masahiko Arakawa, Shogo Tachibana, Hitoshi Ikeda, Masateru Ishiguro, Koji Wada, Chikatoshi Honda, Rie Honda, Yoshiaki Ishihara, Koji Matsumoto, Moe Matsuoka, Tatsuhiro Michikami, Akira Miura, Tomokatsu Morota, Hirotomo Noda, Rina Noguchi, Kazunori Ogawa, Kei Shirai, Eri Tatsumi, Hikaru Yabuta, Yasuhiro Yokota, Manabu Yamada, Masanao Abe, Masahiko Hayakawa, Takahiro Iwata, Masanobu Ozaki, Hajime Yano, Satoshi Hosoda, Osamu Mori, Hirotaka Sawada, Takanobu Shimada, Hiroshi Takeuchi, Ryudo Tsukizaki, Atsushi Fujii, Chikako Hirose, Shota Kikuchi, Yuya Mimasu, Naoko Ogawa, Go Ono, Tadateru Takahashi, Yuto Takei, Tomohiro Yamaguchi, Kent Yoshikawa, Fuyuto Terui, Takanao Saiki, Satoru Nakazawa, Makoto Yoshikawa, Seiichiro Watanabe & Yuichi Tsuda Output Status: Forthcoming/Available Onlineen_UK
dc.contributor.affiliationJapan Aerospace Exploration Agencyen_UK
dc.contributor.affiliationRikkyo Universityen_UK
dc.contributor.affiliationJapan Aerospace Exploration Agencyen_UK
dc.contributor.affiliationRikkyo Universityen_UK
dc.contributor.affiliationAshikaga Universityen_UK
dc.contributor.affiliationChiba Institute of Technologyen_UK
dc.contributor.affiliationJapan Aerospace Exploration Agencyen_UK
dc.contributor.affiliationJapan Aerospace Exploration Agencyen_UK
dc.contributor.affiliationUniversity of Aizuen_UK
dc.contributor.affiliationUniversity of Aizuen_UK
dc.contributor.affiliationUniversity of Aizuen_UK
dc.contributor.affiliationHokkaido Universityen_UK
dc.contributor.affiliationNational Institute of Advanced Industrial Science and Technology (AIST)en_UK
dc.contributor.affiliationHokkaido Kitami Hokuto High Schoolen_UK
dc.contributor.affiliationBiological and Environmental Sciencesen_UK
dc.relation.funderprojectHagermann Consolidated Grants: Make or Break & Comets in the laboratoryen_UK
Appears in Collections:Biological and Environmental Sciences Journal Articles

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