May 12, 2025

【Research Highlights】 Tomography of the oldest solar system materials: particles experienced destruction in the protoplanetary disk

Micron- to millimeter-sized particles that existed in the solar system 4.6 billion years ago are thought to be the building blocks of planets, and studying them is key to understanding how such a large number of planets formed in the solar system. While it is widely believed that such particles grew through accretion into planet-sized bodies, recent theoretical studies have also predicted that destructive collisions may have inhibited their growth. However, direct evidence from meteorites had been lacking.

To investigate possible evidence of such destruction, we focused on calcium-aluminum-rich inclusions (CAIs)—some of the earliest solids to form in the solar system—and applied a novel technique called abrasive tomography to visualize them in 3D. The resulting reconstructions revealed that CAIs exhibit diverse shapes and surface color patterns, indicating that they had been fractured after formation (Fig.).

Our method reconstructs 3D models of meteorite cross sections photographed using a digital camera, yielding images with colors close to what we see with the naked eye. It also achieves micrometer-scale resolution, successfully capturing both morphology and internal structures. This approach is expected to serve as a useful reference for future non-destructive observations of return samples.

(Fig.) Particles such as those enclosed in the meteorite experienced fragmentation in the protoplanetary disk of the early solar system. The figure combines a conceptual illustration of this process with actual tomographic images (bottom).

＜From the first author – Dr. Fukai＞
This study began in 2020 through a collaboration with Hokkaido University via the Tansa-X program (Space Exploration Innovation Hub). We also benefited from SEM-EDS data provided by ASRG, which supported the interpretation of our tomography results. We feel both the satisfaction of having applied an original approach to a fundamental scientific question, and the excitement of venturing into a new research domain.

Specially-appointed Assistant Professor
Dr. Ryota Fukai

Original article:

Journal：  Icarus
Title：  The bright-field grinding tomography of coarse-grained calcium‑aluminum-rich inclusions in the Allende meteorite
Author：  Fukai, R. et al.
DOI：  10.1016/j.icarus.2025.116648
URL：  https://doi.org/10.1016/j.icarus.2025.116648
Available online：  May 12, 2025