Research Interests

We aim to understand the formation and evolutionary processes of organic matter in asteroids and meteorites, and to generate new insights into the origins of life on the early Earth.

The Formation of Organic Matter in Space and the Origins of Life

A variety of organic compounds, including amino acids, have been discovered in carbonaceous chondrites and carbonaceous asteroids. These extraterrestrial materials may have served as a source of prebiotic molecules on the early Earth. These parent bodies formed from icy dust particles, after which the ice melted due to heat from the decay of radioactive nuclides, leading to aqueous alteration. In such aqueous environments, various chemical reactions could have occurred, resulting in the increasing complexity of molecules.

In our laboratory, we conduct hydrothermal reaction experiments and gamma-ray irradiation experiments to simulate the internal environments of these parent bodies, working to elucidate the processes of organic compound formation. To date, we have demonstrated that diverse organic compounds, including amino acids and sugars, can be generated from simple precursors such as ammonia, formaldehyde, and methanol.

In recent studies, we have gained new insights into the formation of deoxyribose—a component of DNA—and the influence of early chemical composition on the types and distribution of products. These findings suggest that small bodies, such as asteroids, may have served as important sites for organic molecule synthesis in the early solar system, offering a new perspective on the study of the origins of life.

Elucidating the Origin of Organic Matter in Meteorites through Nitrogen Chemistry and Microscopic Analysis

Carbonaceous chondrite meteorites contain a variety of organic compounds, including amino acids, most of which exist as insoluble organic matter (IOM). Among these, nitrogen-containing organic compounds, although present in smaller quantities than carbon, are of particular interest as key components linked to the precursor molecules of life. However, due to their low abundance and limitations in analytical techniques, their chemical state has not been fully elucidated.

In our laboratory, we are conducting detailed analyses of the chemical state of nitrogen-containing organic matter in carbonaceous chondrites and asteroid samples using high-sensitivity nitrogen K-edge X-ray absorption near edge structure (PFY N-XANES) analysis at the SPring-8 synchrotron facility. The results suggest that the relative abundances of N=C to N-C nitrogen reflects differences in the formation environments of the early solar system and subsequent alteration processes.

Furthermore, our laboratory is focusing on the analysis of organic matter in extraterrestrial materials at the microscopic scale. While bulk analysis of extracted organic matter has traditionally been the mainstream approach, meteorites exhibit internal heterogeneity resulting from differences in their formation and metamorphic processes. Therefore, we are using scanning transmission X-ray microscopy (STXM) to visualize the distribution of organic functional groups at the submicron scale and elucidate these microscopic heterogeneous structures.

These approaches are applied to the initial analysis of asteroid Ryugu samples collected by Hayabusa2 and asteroid Bennu samples collected by OSIRIS-REx.