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Geochemical Journal, Vol. 48 (No. 6), pp. 571-587, 2014
doi:10.2343/geochemj.2.0350

Hayabusa2: Scientific importance of samples returned from C-type near-Earth asteroid (162173) 1999 JU3

S. Tachibana,1* M. Abe,2 M. Arakawa,3 M. Fujimoto,2 Y. Iijima,2 M. Ishiguro,4 K. Kitazato,5 N. Kobayashi,2 N. Namiki,6 T. Okada,2 R. Okazaki,7 H. Sawada,2 S. Sugita,8 Y. Takano,9 S. Tanaka,2 S. Watanabe,10 M. Yoshikawa,2 H. Kuninaka2 and the Hayabusa2 Project Team

1Department of Natural History Sciences, Hokkaido University, N10W8 Kita-ku, Sapporo, Hokkaido 060-0810, Japan
2Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 252-5210, Japan
3Kobe University, Kobe, Hyogo 657-8501 Japan
4Seoul National University, Gwanak-gu, Seoul 151-742, Korea
5University of Aizu, Aizuwakamatsu, Fukushima 965-8580, Japan
6National Astronomical Observatory of Japan, Oshu, Iwate 023-0861, Japan
7Kyushu University, Hakozaki, Fukuoka 812-8581, Japan
8The University of Tokyo, Kashiwa, Chiba 277-8561, Japan
9Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa 237-0061, Japan
10Nagoya University, Nagoya, Aichi 464-8601, Japan

(Received July 15, 2014; Accepted November 16, 2014)

Abstract: Hayabusa2 is an asteroid exploration mission to return surface samples of a near-Earth C-type asteroid (162173) 1999 JU3. Because asteroids are the evolved remnants of planetesimals that were the building blocks of planets, detailed observation by a spacecraft and analysis of the returned samples will provide direct evidence regarding planet formation and the dynamic evolution of the solar system. Moreover, C-type asteroids are expected to preserve the most pristine materials in the solar system, a mixture of minerals, ice, and organic matter that interact with each other. Space missions are the only way to obtain such pristine materials with geologic context and without terrestrial contamination.
Hayabusa2 will launch off in 2014, arrive at 1999 JU3 in mid-2018, and fully investigate and sample the asteroid at three different locations during its 18-month stay. The concept and design of the Hayabusa2 sampler are basically the same as that on-board Hayabusa, and impact sampling with a 5-g Ta bullet will be made at three locations of the asteroid. The sample container has three separate chambers inside to store samples obtained at different locations separately.
The spacecraft will return to Earth with samples in December 2020. Returned samples will be investigated by state-of-the-art analytical techniques in 2020 to understand the evolutionary history of the solar system from 4.56 Gyr ago to the present by combining results from laboratory examinations of the returned samples with remote-sensing datasets and comparing all results of observations of meteorites, interplanetary dust particles, and future returned samples.
Key words: returned sample, C-type asteroid, planetesimal, early solar system, organic matter


*Corresponding author E-mail: tachi@ep.sci.hokudai.ac.jp


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