著者
Eizo NAKAMURA Katsura KOBAYASHI Ryoji TANAKA Tak KUNIHIRO Hiroshi KITAGAWA Christian POTISZIL Tsutomu OTA Chie SAKAGUCHI Masahiro YAMANAKA Dilan M. RATNAYAKE Havishk TRIPATHI Rahul KUMAR Maya-Liliana AVRAMESCU Hidehisa TSUCHIDA Yusuke YACHI Hitoshi MIURA Masanao ABE Ryota FUKAI Shizuho FURUYA Kentaro HATAKEDA Tasuku HAYASHI Yuya HITOMI Kazuya KUMAGAI Akiko MIYAZAKI Aiko NAKATO Masahiro NISHIMURA Tatsuaki OKADA Hiromichi SOEJIMA Seiji SUGITA Ayako SUZUKI Tomohiro USUI Toru YADA Daiki YAMAMOTO Kasumi YOGATA Miwa YOSHITAKE Masahiko ARAKAWA Atsushi FUJII Masahiko HAYAKAWA Naoyuki HIRATA Naru HIRATA Rie HONDA Chikatoshi HONDA Satoshi HOSODA Yu-ichi IIJIMA Hitoshi IKEDA Masateru ISHIGURO Yoshiaki ISHIHARA Takahiro IWATA Kosuke KAWAHARA Shota KIKUCHI Kohei KITAZATO Koji MATSUMOTO Moe MATSUOKA Tatsuhiro MICHIKAMI Yuya MIMASU Akira MIURA Tomokatsu MOROTA Satoru NAKAZAWA Noriyuki NAMIKI Hirotomo NODA Rina NOGUCHI Naoko OGAWA Kazunori OGAWA Chisato OKAMOTO Go ONO Masanobu OZAKI Takanao SAIKI Naoya SAKATANI Hirotaka SAWADA Hiroki SENSHU Yuri SHIMAKI Kei SHIRAI Yuto TAKEI Hiroshi TAKEUCHI Satoshi TANAKA Eri TATSUMI Fuyuto TERUI Ryudo TSUKIZAKI Koji WADA Manabu YAMADA Tetsuya YAMADA Yukio YAMAMOTO Hajime YANO Yasuhiro YOKOTA Keisuke YOSHIHARA Makoto YOSHIKAWA Kent YOSHIKAWA Masaki FUJIMOTO Sei-ichiro WATANABE Yuichi TSUDA
出版者
The Japan Academy
雑誌
Proceedings of the Japan Academy, Series B (ISSN:03862208)
巻号頁・発行日
vol.98, no.6, pp.227-282, 2022-06-10 (Released:2022-06-10)
参考文献数
245
被引用文献数
1

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), <2.6 Myr after CAI formation. Subsequently, the Ryugu progenitor planetesimal was fragmented and evolved into the current asteroid Ryugu through sublimation.
著者
Masanao Abe Masatsugu Ooe
出版者
日本測地学会
雑誌
測地学会誌 (ISSN:00380830)
巻号頁・発行日
vol.47, no.1, pp.514-520, 2001-03-25 (Released:2010-09-07)
参考文献数
6

Tidal evolution of the earth-moon system was evaluated by estimating the change of dynamic responses of ocean and solid earth to the lunar and solar tidal force during the geological time. The effect of tide on the moon due to the earth was included in the evaluation. We obtained time variations of the orbital elements of the moon, the LOD (length of day) and obliquity of the spin axis of the earth. Our previous study suggested that the variation of LOD up to 600 million years before present estimated by paleontological studies is explained by temporal variation of the ocean continent distribution (Abe et al., 1997). In this study, we paid attention to discriminate how the continental distribution before 500 million years ago affects evaluation of the evolution process, using the continental distribution at 540 million years ago and 700-750 million years ago referred from Maruyama et al. (1997). After making investigations replacing the continental models used in the previous paper, it was suggested the results did not suffer so serious from ambiguity of continent models before about 1.5 billion yeas ago. This point leads us to understand that the small effect of the variation of continent models around these eras comes from the fact that the tidal frequency was remarkably far from the eigen-frequency of tidal response of the oceans. This also suggests that the earlier stage of the earth-moon system, than about 1.5 billion years ago, was possibly governed by mostly small and constant tidal response of the oceans and the comparable or larger effect of tides of the solid earth. Assuming the surface of the earth covered by whole ocean before 2.5 billion years ago, the time when earth-moon distance was very short is around 4.5 billion years ago and we can make almost clear the whole history of the earth-moon dynamical system due to tide after the moon was generated.