¹Ryota Fukai, ²Yusuke Takeda, ^3,4Yuki Masuda, ^4,5Daiki Yamamoto, ⁶Yasuhiro Iba, ⁶Shintaro Sasaki, ⁶Shin Ikegami, ⁷Aya Kubota,⁸Reo Sato, ^1,8Tomohiro Usui
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116648]
¹Astromaterial Science Research Group, Japan Aerospace Exploration Agency
²Scattering and Imaging Division, Japan Synchrotron Radiation Research Institute
³Department of Earth and Planetary Sciences, Institute of Science Tokyo
⁴Centre for Star and Planet Formation, Globe Institute, University of Copenhagen
⁵Department of Earth and Planetary Sciences, Kyushu University
⁶Department of Earth and Planetary Sciences, Hokkaido University
⁷Research Institute for Geo-Resources and Environment, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology
⁸Department of Earth and Planetary Science, The University of Tokyo
Copyright Elsevier

The evolution associated with coagulation/fragmentation processes of dust to planetesimals in the protosolar disk is the critical phase of planet formation in the Solar System. The meteoritic components, such as calcium‑aluminum-rich inclusions (CAIs), will provide essential constraints on the coagulation/fragmentation process in the early stage of the disk. We applied the bright-field grinding tomography method to an Allende meteorite (CV3) slab to visualize the coarse-grained CAIs (CG-CAIs) in a colorized 3D model with high spatial resolution. We found four mm-scale CG-CAIs that experienced deformation and/or fragmentation processes within ~1.8 × 103 mm3 Allende slab. An angular-shaped CG-CAI’s surface showed the anisotropy of red-gray and white sides, which suggests that the fragmentation results in the loss of the primitive Wark-Lovering rim. We also found a vesicular-shaped CG-CAI, which indicates that the fracturing and complex formation process of this CG-CAI likely proceeded prior to the accretion of the Wark-Lovering rim. Our observations reveal that the fragmentation of Allende CAIs occurred during the parent body accretion stage and also in the protosolar disk.

¹Elias Wölfer, ¹Christoph Burkhardt, ²Francis Nimmo, ¹Thorsten Kleine
Earth and Planetary Science Letters 663, 119435 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2025.119435]
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
²Department of Earth and Planetary Sciences, University of California Santa Cruz, 1156 High St, Santa Cruz, CA 95064, USA
Copyright Elsevier

The bulk silicate Earth (BSE) is depleted in moderately volatile elements, indicating Earth formed from a mixture of volatile-rich and -poor materials. To better constrain the origin and nature of Earth’s volatile-rich building blocks, we determined the mass-dependent isotope compositions of Ge in carbonaceous (CC) and enstatite chondrites. We find that, similar to other moderately volatile elements, the Ge isotope variations among the chondrites reflect mixing between volatile-rich, isotopically heavy matrix and volatile-poor, isotopically light chondrules. The Ge isotope composition of the BSE is within the chondritic range and can be accounted for as a ∼2:1 mixture of CI and enstatite chondrite-derived Ge. This mixing ratio appears to be distinct from the ∼1:2 ratio inferred for Zn, reflecting the different geochemical behavior of Ge (siderophile) and Zn (lithophile), and suggesting the late-stage addition of volatile-rich CC materials to Earth. On dynamical grounds it has been argued that Earth accreted CC material through a few Moon-sized embryos, in which case the Ge isotope results imply that these objects were volatile-rich, presumably because they were either undifferentiated or accreted volatile-rich objects themselves before being accreted by Earth.