Joint Press Release
Shogo Tachibana, Professor, Department of Earth and Planetary Science, Space and Planetary Science Organization

Moe Matsuoka, a researcher at the National Institute of Advanced Industrial Science and Technology (AIST) and Toru Kouyama, a team leader, National Institute of Advanced Industrial Science and Technology, in collaboration with Prof. Tomoki Nakamura, Tohoku University; Kana Amano, Japan Society for the Promotion of Science Research Fellow, Tohoku University; Dr. Takahito Osawa, Research Director, Japan Atomic Energy Agency; Prof. Shogo Tachibana, University of Tokyo; Prof. Hiroshi Naraoka and Associate Prof. Takashi Okazaki, Kyushu University, etc. and other researchers, conducted a direct comparison between the data obtained by the asteroid probe Hayabusa2 from the sky over the surface of the asteroid Ryugu and the data obtained by measuring samples collected and brought back (sample return) from Ryugu without exposing them to the Earth’s atmosphere.

As a result, we found that while the observed data from Ryugu’s surface and the sample return data agree well, there is a clear difference in the absorption of hydroxy groups (-OH), which is the key to determine the presence of water. In order to clarify the cause of this difference, experiments and data analysis of primitive meteorites similar to Ryugu, which are rich in hydrous silicates, revealed that Ryugu’s surface (about 1/100 mm) has been altered (space weathering) by exposure to cosmic rays and dust, resulting in partial loss of water.

This research result, which was only possible through a combination of remote observation from the spacecraft and analysis of collected samples, is one of the landmark results that demonstrate the importance of sample return in planetary exploration. The details of the study were published in Communications Earth & Environment on September 27, 2023 (JST).

For more information, please refer to the following

Graduate School of Science web: https://www.s.u-tokyo.ac.jp/ja/press/10047/
Publication URL: https://www.nature.com/articles/s43247-023-00991-3

Tomo-e Gozen camera (https://tomoe.mtk.ioa.s.u-tokyo.ac.jp) on the 1.05 m Kiso Schmidt telescope, Univ. Tokyo, successfully filmed the OSIRIS-REx spacecraft and the Sample Return Capsule!

Joint Press Release
Shogo Tachibana (Professor, Department of Earth and Planetary Science, Japan Aerospace Exploration Agency)

Japan Agency for Marine-Earth Science and Technology (JAMSTEC; President: Hiroyuki Yamato) The international collaborative research group led by Dr. Toshihiro Yoshimura, Deputy Senior Researcher, and Dr. Yoshinori Takano, Senior Researcher, at the Biogeochemistry Research Center, and Prof. Hiroshi Naraoka, Graduate School of Science, Kyushu University, is a joint research group with the Graduate School of Science, The University of Tokyo, National Institute of Advanced Industrial Science and Technology (AIST), Horiba Advanced Techno Co. The group, together with researchers from the Graduate School of Science at the University of Tokyo, National Institute of Advanced Industrial Science and Technology, Horiba Techno, Horiba Techno Service, Thermo Fisher Scientific Japan Group, Hokkaido University, and Tokyo Institute of Technology, conducted precise chemical analysis of soluble components in samples from the asteroid Ryugu to determine their composition, content, etc. The results of the analysis are shown in Table 1. The composition and content of the soluble components were clarified.

Asteroid Ryugu is one of the primordial bodies that retain the chemical composition of the entire solar system before the birth of the Earth. The initial analysis of Hayabusa2 has revealed various properties, contents, and history of the asteroid, but the material information of ionic components among soluble components has remained unknown.

In this study, soluble components were extracted from samples of the asteroid Ryugu and precisely analyzed at the inorganic and organic molecular levels. The results showed that hydrothermal extracts, which reflect the most soluble components, are very rich in sodium ions (Na+). Sodium ions act as electrolytes that stabilize the surface charge of minerals and organic matter, and some are thought to precipitate as sodium salts (Salt) by binding with organic molecules and other substances. Various organosulfur molecules were also found in the extract. It is thought that the chemical state of the organic sulfur molecules in the water on the asteroid Ryugu changed, resulting in the chemical evolution of a wide variety of organosulfur molecules.

This finding is important not only for unraveling the material evolution of the early solar system, but also for answering the major question of how they led to the chemical processes that ultimately led to the birth of life.

The results were published in the scientific journal Nature Communications on September 18, 2023 (JST).

For more information, please refer to the following

Graduate School of Science web: https://www.s.u-tokyo.ac.jp/ja/press/10021/
Publication URL: https://www.nature.com/articles/s41467-023-40871-0

On Monday, August 7, 2023, students from Nada Junior High School and Nada Senior High School visited UTOPS. We gave them a mock lecture about the Hayabusa2 exploration and the rock brought back from the asteroid Ryugu.

On Friday, August 4, 2023, students from Komatsu High School in Ishikawa, Japan, visited UTOPS. We gave a mock lecture on the Hayabusa2 exploration and the rock brought back from the asteroid Ryugu.

On August 1 (Tue.) and 2 (Wed.), 2023, we held an astronomy lab for students from Matsumoto Fukashi High School in Nagano Prefecture and Kariya High School in Aichi Prefecture. The students estimated the distance to galaxies from photographs of galaxies and used the recession velocity of those galaxies to determine the age of the Universe.

Joint Press Release
Shogo Tachibana (Professor, Department of Earth and Planetary Science)
Takeshi Iizuka (Associate Professor, Department of Earth and Planetary Science)

A research team led by Associate Professor Wataru Fujiya of the Graduate School of Science and Engineering, Ibaraki University, Associate Professor Noriyuki Kawazaki and Professor Hisayoshi Yurimoto of the Graduate School of Science, Hokkaido University, Professor Tetsuya Yokoyama of the Department of Earth and Planetary Science, Graduate School of Science, Tokyo Institute of Technology, and Professor Shogo Tachibana of the Graduate School of Science, University of Tokyo, has analyzed samples from the asteroid Ryugu samples recovered by the Hayabusa2 spacecraft, and have elucidated the evolution of oxygen concentrations and gas molecular species present on Ryugu.

In this study, we examined the abundance ratios of carbon and oxygen isotopes in the carbonate minerals (calcite and dolomite) in Ryugu’s samples. The results showed that the isotope ratios of both carbon and oxygen in calcite varied greatly among the different particles, while those in mafic calcite varied little. These results suggest that calcite formed early in the alteration process at Ryugu, when temperatures and oxygen concentrations were rising and the fraction of gas species was changing, while the calcite was formed at higher temperatures and with a relatively high fraction of carbon dioxide in the gas, while the system was in equilibrium.

Such isotopic compositions of carbonate minerals have not been reported in previous meteorite studies. This suggests that Ryugu and its meteorite parent bodies were composed of different materials and evolved in unique environments.

The results were published online in Nature Geoscience on Wednesday, July 10, 2023.

For more information, please see

Graduate School of Science web: https://www.s.u-tokyo.ac.jp/ja/info/8544/
Publication URL: https://www.nature.com/articles/s41561-023-01226-y