Hiroshi Hidaka¹ and Shigekazu Yoneda²

¹Department of Earth and Planetary Systems Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
²Department of Science and Engineering, National Museum of Nature and Science, Tsukuba 305-0005, Japan

The idea that solar system materials were irradiated by solar cosmic rays from the early Sun has long been suggested, but is still questionable. In this study, Sr, Ba, Ce, Nd, Sm, and Gd isotopic compositions of sequential acid leachates from the Kapoeta meteorite (howardite) were determined to find systematic and correlated variations in their isotopic abundances of proton-rich nuclei, leading to an understanding of the irradiation condition by cosmic rays. Significantly large excesses of proton-rich isotopes (p-isotopes), ⁸⁴Sr,¹³⁰Ba, ¹³²Ba, ¹³⁶Ce, ¹³⁸Ce, and ¹⁴⁴Sm, were observed, particularly in the first chemical separate, which possibly leached out of the very shallow layer within a few ?m from the surface of regolith grains in the sample. The results reveal the production of p-isotopes through the interaction of solar cosmic rays with the superficial region of the regolith grains before the formation of the Kapoeta meteorite parent body, suggesting strong activity in the early Sun

Reference
Hidaka H and Yoneda S (2014) Isotopic Excesses of Proton-rich Nuclei Related to Space Weathering Observed in a Gas-rich Meteorite Kapoeta. The Astrophysical Journal 786:138.
[doi:10.1088/0004-637X/786/2/138]

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