Hokkaido University

Kyoto University

Tokyo Institute of Technology

The University of Tokyo Graduate School of Science

Summary of Presentations

A research team led by Associate Professor Noriyuki Kawazaki and Professor Naoyoshi Yurimoto of the Graduate School of Science, Hokkaido University, Assistant Professor Toru Matsumoto of the Hakubi Center, Kyoto University, Professor Tetsuya Yokoyama of the Department of Earth and Planetary Science, Faculty of Science, UTokyo Organization for Planetary and Space Science, and Professor Shogo Tachibana of the Graduate School of Science, The University of Tokyo, has discovered many minerals that formed in the high-temperature environment of the early solar system in samples collected from the asteroid C-type Ryugyu by the Hayabusa2 asteroid probe of the Japan Aerospace Exploration Agency. The team, led by Professor Tetsuya Yokoyama and Professor Shogo Tachibana of the University of Tokyo's Graduate School of Science, discovered a number of minerals formed in the high-temperature environment of the early solar system in samples collected from the C-type asteroid Ryuguu by the Japan Aerospace Exploration Agency's Hayabusa2.

Hayabusa2's initial analysis had previously shown that Ryuguu is similar to an Ivena-type carbonaceous meteorite and is composed mainly of precipitates from aqueous solutions at low temperatures (about 40°C). The research team identified a number of new minerals from "Ryugu" and Ivna-type carbonaceous meteorites that formed in high-temperature environments (>1000°C), and analyzed 40 of these particles using an isotope microscope (secondary ion mass spectrometer) at Hokkaido University to determine their origin. As a result, the high-temperature minerals of "Ryugu" and Ivna-type carbonaceous meteorites were clearly divided into two types with different origins. The high-temperature minerals formed in the high-temperature environment of the inner solar system and were transported to the outer solar system, where they accumulated in the parent bodies of Ryuguu and Ivuna carbonaceous meteorites.

The ratio of the two types of high-temperature minerals was not only very different from that of ordinary carbonaceous meteorites, but also very similar to that of samples collected by NASA from Comet Wilde 2 during the Stardust mission in 2004. This indicates that the Ryugyu and Ivna-type carbonaceous meteorites formed in a region closer to the comet and farther from the Sun than the parent bodies of ordinary carbonaceous meteorites.

The research results were published online in Science Advances on Friday, December 16, 2022.

Figure: The current orbits of Lyugu and Comet Wilde 2 are different. However, the oxygen isotopic composition of the high-temperature minerals in the object suggests that the two were formed close to each other.

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