Cosmic‐ray exposure age and heliocentric distance of the parent body of the Rumuruti chondrite PRE 95410

1Tomoya Obase,1Daisuke Nakashima,1Tomoki Nakamura,2,3Keisuke Nagao
Meteoritics & Planetary Science (in Press) Link to Article []
1Division of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University, Aoba, Sendai, Miyagi, 980‐8578 Japan
2Geochemical Research Center, Graduate School of Science, University of Tokyo, Hongo, Bunkyo, Tokyo, 113‐0033 Japan
3Division of Polar Earth‐System Sciences, Korea Polar Research Institute, 26 Songdomirae‐ro, Yeonsu‐gu, Incheon, 21990 Korea
Published by arrangement with John Wiley & Sons

We measured concentrations and isotopic ratios of noble gases in the Rumuruti (R) chondrite Mount Prestrud (PRE) 95410, a regolith breccia exhibiting dark/light structures. The meteorite contains solar and cosmogenic noble gases. Based on the solar and cosmogenic noble gas compositions, we calculated a heliocentric distance of its parent body, a cosmic‐ray exposure age on the parent body regolith (parent body exposure age), and a cosmic‐ray exposure age in interplanetary space (space exposure age) of the meteorite. Assuming a constant solar wind flux, the estimated heliocentric distance was smaller than 1.4 ± 0.3 au, suggesting inward migration from the asteroid belt regions where the parent body formed. The largest known Mars Trojan 5261 Eureka is a potential parent body of PRE 95410. Alternatively, it is possible that the solar wind flux at the time of the parent body exposure was higher by a factor of 2–3 compared to the lunar regolith exposure. In this case, the estimated heliocentric distance is within the asteroid belt region. The parent body exposure age is longer than 19.1 Ma. This result indicates frequent impact events on the parent body like that recorded for other solar‐gas‐rich meteorites. Assuming single‐stage exposure after an ejection event from the parent body, the space exposure age is 11.0 ± 1.1 Ma, which is close to the peak of ~10 Ma in the exposure age distribution for the solar‐gas‐free R chondrites.


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