报告题目：Speciation of various elements on an asteroid Ryugu to estimate aqueous environment in the parent body using a key material, smectite
报告时间：2024年3月28日（周四） 15:30-17:00
报告地点：16 教 221 会议室
报告人：Yoshiro Takahashi 教授（日本东京大学）
Yoshiro Takahashi（高桥嘉夫）教授，东京大学理学院同位素科学中心主任、日本地球化学学会会长，分别于1992年、1994年和1997年获东京大学化学专业学士、硕士和博士学位，研究方向为地球化学、环境化学和放射性化学，长期从事地表关键元素循环、环境问题、行星科学、同步辐射等方面的研究。发表研究论文350余篇，Google scholar总引用15700余次，H-index为65。
报告简介：The parent body of the C-type asteroid Ryugu is thought to have been rich in volatile elements and abundant in liquid water, making it an important research target for the origin of water and organic matter on Earth. The water caused various alteration in the surrounding minerals, resulting in layered silicates such as smectite (saponite) and serpentinite being the main constituent minerals of the Ryugu (Nakamura et al., 2023). In this process, the organic matter of the Ryugu parent body also underwent chemical reactions, and a wide variety of organic matter was synthesized (Naraoka et al., 2023). It is particularly important to obtain information on the water environment during the aqueous alteration, as the products of chemical reactions of organic matter in water depend on the pH and redox potential (Eh) of the water. In this study, the speciation of various elements was carried out using scanning transmission X-ray microscopy (STXM) and bulk X-ray absorption near-edge structure (XANES) related to the aqueous environment in the Ryugu parent body. The speciation of these elements in smectite (saponite) is particularly important since the Fe oxidation state and chemical composition within the interlayer of the saponite can indicate the Eh-pH condition of the Ryugu water. In the presentation, the importance of analysis of smectite will be also highlighted, since the cation adsorption on the smectite is also important in environmental chemistry and resource chemistry in addition to the cosmochemical application.
