小惑星リュウグウの微粒子を分析したところ、驚くべき結果が得られた(Analysis of particles of the asteroid Ryugu delivers surprising results)

2022-09-22 フランクフルト大学

The asteroid Ryugu from a distance of 20 kilometres, photographed by the Hayabusa 2 space probe. Photo credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu and AIST

＜関連情報＞

• https://aktuelles.uni-frankfurt.de/englisch/analysis-of-particles-of-the-asteroid-ryugu-delivers-surprising-results/
• https://www.science.org/doi/10.1126/science.abn8671

炭素質小惑星リュウグウの形成と進化。リターンサンプルからの直接証拠 Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples

T. Nakamura,M. Matsumoto,K. Amano,Y. Enokido,M. E. Zolensky,T. Mikouchi,H. Genda,S. Tanaka,M. Y. Zolotov,K. Kurosawa,S. Wakita,R. Hyodo,H. Nagano,D. Nakashima,Y. Takahashi,Y. Fujioka,M. Kikuiri,E. Kagawa,M. Matsuoka,A. J. Brearley,A. Tsuchiyama,M. Uesugi,J. Matsuno,Y. Kimura,M. Sato,R. E. Milliken,E. Tatsumi,S. Sugita,T. Hiroi,K. Kitazato,D. Brownlee,D. J. Joswiak,M. Takahashi,K. Ninomiya,T. Takahashi,T. Osawa,K. Terada,F. E. Brenker,B. J. Tkalcec,L. Vincze,R. Brunetto,A. Aléon-Toppani,Q. H. S. Chan,M. Roskosz,J.-C. Viennet,P. Beck,E. E. Alp,T. Michikami,Y. Nagaashi,T. Tsuji,Y. Ino,J. Martinez,J. Han,A. Dolocan,R. J. Bodnar,M. Tanaka,H. Yoshida,K. Sugiyama,A. J. King,K. Fukushi,H. Suga,S. Yamashita,T. Kawai,K. Inoue,A. Nakato,T. Noguchi,F. Vilas,A. R. Hendrix,C. Jaramillo,Correa,D. L. Domingue,G. Dominguez,Z. Gainsforth,C. Engrand,J. Duprat,S. S. Russell,E. Bonato,C. Ma,T. Kawamoto,T. Wada,S. Watanabe,R. Endo,S. Enju,L. Riu,S. Rubino,P. Tack,S. Takeshita,Y. Takeichi,A. Takeuchi,A. Takigawa,D. Takir,T. Tanigaki,A. Taniguchi,K. Tsukamoto,T. Yagi,S. Yamada,K. Yamamoto,Y. Yamashita,M. Yasutake,K. Uesugi,I. Umegaki,I. Chiu,T. Ishizaki,S. Okumura,E. Palomba,C. Pilorget,S. M. Potin,A. Alasli,S. Anada,Y. Araki,N. Sakatani,C. Schultz,O. Sekizawa,S. D. Sitzman,K. Sugiura,M. Sun,E. Dartois,E. De Pauw,Z. Dionnet,Z. Djouadi,G. Falkenberg,R. Fujita,T. Fukuma,I. R. Gearba,K. Hagiya,M. Y. Hu,T. Kato,T. Kawamura,M. Kimura,M. K. Kubo,F. Langenhorst,C. Lantz,B. Lavina,M. Lindner,J. Zhao,B. Vekemans,D. Baklouti,B. Bazi,F. Borondics,S. Nagasawa,G. Nishiyama,K. Nitta,J. Mathurin,T. Matsumoto,I. Mitsukawa,H. Miura,A. Miyake,Y. Miyake,H. Yurimoto,R. Okazaki,H. Yabuta,H. Naraoka,K. Sakamoto,S. Tachibana,H. C. Connolly Jr.,D. S. Lauretta,M. Yoshitake,M. Yoshikawa,K. Yoshikawa,K. Yoshihara,Y. Yokota,K. Yogata,H. Yano,Y. Yamamoto,D. Yamamoto,M. Yamada,T. Yamada,T. Yada,K. Wada,T. Usui,R. Tsukizaki,F. Terui,H. Takeuchi,Y. Takei,A. Iwamae,H. Soejima,K. Shirai,Y. Shimaki,H. Senshu,H. Sawada,T. Saiki,M. Ozaki,G. Ono,T. Okada,N. Ogawa,K. Ogawa,R. Noguchi,H. Noda,M. Nishimura,N. Namiki,S. Nakazawa,T. Morota,A. Miyazaki,A. Miura,Y. Mimasu,K. Matsumoto,K. Kumagai,T. Kouyama,S. Kikuchi,K. Kawahara,S. Kameda,T. Iwata,Y. Ishihara,M. Ishiguro,H. Ikeda,S. Hosoda,R. Honda,C. Honda,Y. Hitomi,N. Hirata,N. Hirata,T. Hayashi,M. Hayakawa,K. Hatakeda,S. Furuya,R. Fukai,A. Fujii,Y. Cho,M. Arakawa,M. Abe,S. Watanabe,Y. Tsuda
Science  Published:22 Sep 2022
DOI: 10.1126/science.abn8671

Abstract

Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed seventeen Ryugu samples measuring 1-8 mm. CO₂-bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and Ca, Al-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed by aqueous alteration reactions at low temperature, high pH, and water/rock ratios < 1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate Ryugu’s parent body formed ~ 2 million years after the beginning of Solar System formation.