2023/03/06(Mon) 14:00 -16:00 五樓第一會議室 5F, 1st Meeting Room
Title
A cosmic cradle for water and organic molecules; spectro-microscopic analysis in Hayabusa2 project
Speaker
Dr. Takuji Ohigashi (Photon Factory, Institute of Materials Structure Sciences, High Energy Accelerator Research Organization (KEK))Abstract
Scanning transmission X-ray microscopy (STXM) is a synchrotron-based technique to acquire 2-dimensional X-ray absorption spectroscopy with high resolution down to 30 nm. Potential of STXM essentially depends on energy range of a light source, a synchrotron and a beamline. Use of soft X-ray region is quite powerful because a lot of absorption edges of light elements and transition metals are available. Furthermore, high transmittance of the X-rays enables STXM to perform special measurement techniques, such as 3-dimensional observation, in-situ/operand measurement and so on. Therefore, STXM is widely used in various fields, not only in physics and chemistry but also biology, medical science and material science. Planetary science and astrobiology are also one of them.
In 2014, a small spacecraft “Hayabusa2” was launched to a small asteroid “Ryugu”, 280 million km away from the Earth to collect some samples of the asteroid, pebbles and gasses, directly. In December 2020, the sample capsule of Hayabusa2 successfully retuned to the Earth with 5.4 g of the samples. The returned samples had neither contamination by terrestrial materials nor heat by entrance to atmosphere. Therefore, the returned samples are considered as “the purest extraterrestrial material on the Earth” and were distributed to 8 analytical teams. One of the teams, Phase 2 curation Kochi team, has discussed how to analyze the samples with maximum efficiency and developed a protocol, “coordinated micro/nano-analysis”, by designing special devices [1]. The protocol uses synchrotron-based X-ray computed tomography, a focused-ion beam apparatus, transmission electron microscopy, nano-secondary ion mass spectroscopy and STXM and the analyses are performed in order from non-destructive to destructive process. In the protocol, the STXM beamline BL4U in UVSOR Synchrotron (Okazaki, Japan)[2, 3] was successfully used to analyze localized organic materials in returned samples from Ryugu, which were not found in typical meteorites. In this talk, recent development of BL4U and its role in Hayabusa2 project will be talked [4].
[1] M. Ito, et al., Earth Plants Space, 72, (2020), 133.
[2] T. Ohigashi, et al., J. Phys.: Conf. Ser., 463, (2013), 012006.
[3] T. Ohigashi, et al., Rev. Sci. Instrum., 91, (2020), 103110.
[4] M. Ito, et al., Nat. Astron., 6, (2022), 1163-1171.
Language
演講語言 (Language): in English
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