[P-PS04] Small Solar System Bodies: A New Insight from Hayabusa2, OSIRIS-REx and Other Space Missions

[PPS04-P16] Assessing the irradiation effects by a synchrotron X-ray micro-computed tomography on the organic materials in carbonaceous chondrite: Examination at SPring-8 facility

*Haruna Sugahara¹, Yoshinori Takano², Toshihiro Yoshimura², Nanako O Ogawa², Naohiko Ohkouchi², Masayuki Uesugi³, Akira Tsuchiyama⁴, Hayabusa2 project team (1.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (ISAS/JAXA), 2.Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 3.Japan Synchrotron Radiation Research Institute, 4.Ritsumeikan University)

Keywords:Hayabusa2, Sample analysis, μCT, SPring-8, Organic materials, Carbonaceous chondrite

X-ray micro-computed tomography (μCT) using a synchrotron light source is a strong tool to reveal the three-dimensional (3D) structure of the small particle including its mineralogy and the textures. It was applied to the regolith particles on the asteroid Itokawa, which were returned by the Hayabusa spacecraft, and helped to understand the origin and the evolution of the particles [1]. The subsequent Hayabusa2 mission succeeded in returning the samples (> 5 gram for a twice touchdown [2]) from the carbonaceous-type asteroid Ryugu in December 2020. The μCT is planned as one of the initial analysis procedures of the Ryugu samples [3]. However, there is a concern about the effect of X-ray irradiation caused by μCT on the organic materials in the Ryugu samples. The organic materials are generally sensitive to X-ray irradiation due to potential alteration and/or degradation processes. Thus, we performed an assessment to examine the effect of the μCT procedure prior to the initial analysis. Friedrich et al. (2016) examined the effects of X-ray irradiation by μCT to amino acids in Murchison meteorite (CM2) at the GeoSoilEnviroCARS (GSECARS) facility at the Advanced Photon Source (APS), Argonne National Laboratory and reported that there was no significant effect observed for the abundance of the amino acids [4].

The purpose of the study is to investigate the potential effect on the soluble organic materials, inorganic ions, and bulk element profiles in a carbonaceous chondrite caused by the X-ray irradiation of μCT at the synchrotron SPring-8 [3]. We conducted the two sets of the irradiation experiments using a homogenized Murchison meteorites (CM2) powder. The one sample was irradiated with the typical condition as the usual μCT analysis. The total irradiation time was around 5 minutes. The second sample was irradiated for a longer time (8.5 hours) at the same energy. These irradiated samples and the non-irradiated control samples were investigated using several analytical techniques. We analyzed the concentration of the amino acids, which are labile but important target molecules in Ryugu samples. We also analyzed the soluble ion components using ion chromatograph and inductively coupled plasma-mass spectrometry (ICP-MS) and the bulk carbon and nitrogen abundances using an elemental analyzer connected to isotope ratio mass spectrometer (EA/IRMS). In this presentation, we will overview the present organic and inorganic assessments for the sampling process of the μCT description at SPring-8.



References:

[1] Tsuchiyama A. et al. (2011) Science, 336, 1125-1128.

[2] Tachibana S. et al. (2021) Abstract for the 52nd Lunar and Planetary Science Conference (LPSC).

[3] Tsuchiyama A. et al. (2020) Abstract for Spring-8 symposium 2020.

[4] Friedrich J. M. et al. (2016) Meteorit. Planet. Sci. 51, 429-437.