Deciphering the evolution of the early Solar System from returned samples and meteorites

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Apr. 21, 2026 | Aerospace Project Research Associate, ISAS people

WADA Sohei / Astromaterials Science Research Grp.

This article introduces the research conducted by Aerospace Project Research Associates working at the Institute of Space and Astronautical Science (ISAS). The Aerospace Project Research Associate Program is a human resource development program for early-career researchers, designed to help them refine and advance their own research through participation in JAXA projects and related activities. At ISAS, the program is operated with a strong emphasis on this perspective of researcher development.

Research Summary

Our Astromaterials Science Research Group operates the Extraterrestrial Sample Curation Center, which manages the samples brought back from asteroids by Hayabusa, Hayabusa2, and NASA’s OSIRIS-REx mission, and is commonly known as Curation (https://curation.isas.jaxa.jp/en/). To prevent contamination of these valuable samples, we use high-vacuum or nitrogen-atmosphere clean chambers to carefully handle each individual particle. We record basic information such as appearance and weight, register this data in a database, and prepare the Catalogue of Extraterrestrial Samples that can be viewed and explored by researchers around the world. Based on research proposals that use this catalogue, we distribute samples to researchers in Japan and abroad. The samples to be returned by the upcoming Martian Moons eXploration (MMX) mission, scheduled for launch in JFY 2026, will also be managed in Curation. In addition, Curation conducts research on Solar System materials using returned samples and meteorites in our collection, as well as research on the development of analytical techniques.

My research interests are in how our Solar System came to be. I’m particularly interested in two stages of Solar System evolution: first, the early stage, the birth of the Solar System, up to the formation of planets, and second, the surface evolution of airless bodies, such as asteroids. For the first theme, I studied Ca-Al-rich Inclusions (CAIs) in meteorites (Fig. 1). CAIs are the oldest solids in the Solar System, formed 4.567 billion years ago in the high-temperature region near the young Sun. By analyzing CAIs, we can investigate the environment of the early Solar System. Using a secondary ion mass spectrometry*1, I measured the oxygen isotopic compositions and formation ages of constituent minerals of CAIs. These analyses demonstrated that 16O-rich and 16O-poor nebular gas coexisted in the protoplanetary disk*2 for several hundred thousand years. For the second theme, I studied gas-rich meteorites, which contain abundant noble gases that were implanted by the solar wind (SW) that streams from the Sun. These meteorites are thought to derive from regolith (a lose top layer of material) on their airless, asteroid parent bodies. Thus, the distribution of SW noble gases within gas-rich meteorites would allow us to investigate the surface evolution history of their parent asteroids. To achieve this, I developed a helium-isotope imaging technique using secondary neutral mass spectrometry*3. Using this method, I successfully visualized the distribution of SW-4He in gas-rich meteorites (Fig. 2).

Fig.1
Fig. 1. Ca-Al-rich inclusion from Northwest Africa 8613 meteorite (Wada et al. 2020 GCA. DOI: 10.1016/j.gca.2020.08.004)
Fig.2
Fig. 2. SW-4He distribution in Northwest Africa 801 meteorite (Wada et al. 2026 MaPS. DOI: 10.1111/maps.70161)

I am currently developing a method to analyze the valence state (similar to the effective electric charge of an atom) of titanium in CAI minerals using a soft X-ray emission spectrometer (Fig. 3). The valence state of titanium varies depending on the redox conditions (i.e., H2/H2O ratio of nebular gas) at formation, making it a key tracer of the physicochemical (physical and chemical conditions) environment of the protoplanetary disk. Analyses of returned samples have recently revealed that CAIs are present not only in meteorites but also in the samples from asteroids Ryugu and Bennu returned by Hayabsua2 and OSIRIS-REx. However, their abundances and sizes in returned samples tend to be lower compared with meteorites. Therefore, to decipher the evolution of the early Solar System from returned samples, it is essential to develop microscale analytical techniques for determining the valence state of titanium. I think being a member of the curation group has the great advantage of having the returned samples and meteorite samples that we are measuring close at hand, so I am able to carry out efficient development by trial and error in experiments and by sharing information with the people involved.

Fig.3
Fig. 3. Soft X-ray emission spectrometer at ASRG

Terminologies

  • *1 Secondary ion mass spectrometry (SIMS): SIMS is a technique for analyzing the constituents of the sample surface. When primary ions irradiate the sample surface, atoms near the surface are ionized and ejected into vacuum as secondary ions (sputtering). Mass spectrometry is used to analyze the secondary ions, thereby enabling a qualitative and quantitative analysis of the constituents of the sample.
  • *2 Protoplanetary disk: A disk of gas and dust that formed around the proto-Sun at the birth of the Solar System. It is within this disk that the planets eventually formed.
  • *3 Secondary neutral mass spectrometry (SNMS): When primary ions irradiate the sample surface, various particles such as neutrals and ions are sputtered. Among the sputtered particles, ions constitute less than 10%, with the majority being neutrals. SNMS is a technique that performs mass spectrometry by post-ionizing these neutrals. The instrument used in this study (LIMAS) performs post-ionization by irradiating neutrals with laser pulses.

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