Japan Aerospace Exploration Agency (JAXA)

Hiroshima University, Yokohama National University, High Energy Accelerator Research Organization, Kyushu University,
Hokkaido University, Tohoku University, The University of Tokyo, Graduate School of Science

Summary of Presentations

The Solid Organic Matter Analysis Team led by Professor Hikaru Yabuta, Graduate School of Advanced Science and Engineering, Hiroshima University, has analyzed the Department of Chemistry, isotopic composition, and morphology of solid organic matter in the asteroid Ryuguu sample brought back to Earth by the asteroid probe Hayabusa2. The non-destructive analysis of the Asteroid Ryuguu sample (37 microparticles ranging in size from 200 to 900 μm) using various microspectroscopic techniques revealed that the types and proportions of chemical bonds comprising the organic matter in the sample were similar to those of the most primitive Ivnar-type carbonaceous chondrite meteorites (CI Group) and primitive Migay-type carbonaceous chondrites ( CM Group). Electron microscopic examination of them revealed nanometer-sized spherical organic matter and thinly spread irregularly shaped organic matter adjacent to or mixed with layered silicates and carbonates. Their coexistence with secondary minerals produced in Ryuguu's parent body is evidence that these organic materials also originated from reactions with liquid water in the parent body. The absence of graphite-like ordered structures in the organic matter of the Ryuguu samples means that the organic matter of the analyzed Ryuguu samples was not heated to high temperatures in the parent body interior or by the impact of the object.

In addition, the isotopic composition of the asteroid Ryuguu sample was measured, and areas of deuterium and nitrogen15 concentrations were detected. Such isotopic compositions are not found in terrestrial organic matter and are known to occur only in low-temperature environments of several tens of Kelvin (minus 200°C or lower). Therefore, the analyzed Ryuguu organics are indeed of extraterrestrial origin, and at least some of these organics were formed in cryogenic environments such as interstellar molecular clouds and outer protoplanetary disks.

Figure: Formation and evolution of solid organic matter during Ryuguu evolution. Credit: Modified from Yabuta et al. 2023

The following members from The University of Tokyo participated in this research project.

Shogo Tachibana	Professor, Department of Earth and Planetary Science, UTokyo Organization for Planetary and Space Science
Taiga Okumura	Assistant Professor, Department of Earth and Planetary Science
Yoshio Takahashi	Professor, Department of Earth and Planetary Science
Seiji Sugita	Professor, Department of Earth and Planetary Science
Tomokatsu Morota	Associate Professor, Department of Earth and Planetary Science
Shizumoe Furuya	Project Specialist, UTokyo Organization for Planetary and Space Science

For more information, please visit the website of the Japan Aerospace Exploration Agency (JAXA ).

Journals

Journal name	Science
Title of paper	Macromolecular organic matter in samples of the asteroid (162173) Ryugu
DOI number	10.1126/science.abn9057