Stardust in Antarctic micrometeorites |
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Authors: | Toru YADA Christine FLOSS Frank J. STADERMANN Ernst ZINNER Tomoki NAKAMURA Takaaki NOGUCHI A. Scott LEA |
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Affiliation: | 1. Laboratory for Space Sciences and Physics Department, CB 1105, Washington University, Saint Louis, Missouri 63130, USA;2. Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, Sagamihara, Kanagawa 229‐8510, Japan;3. Department of Earth and Planetary Science, Graduate School of Science, Kyushu University, Hakozaki, Fukuoka 812‐8581, Japan;4. Department of Materialogical and Biological Sciences, Ibaraki University, Mito, Ibaraki 310‐8512, Japan;5. Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, USA |
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Abstract: | Abstract— We report the discovery of presolar silicate, oxide (hibonite), and (possibly) SiC grains in four Antarctic micrometeorites (AMMs). The oxygen isotopic compositions of the eighteen presolar silicate (and one oxide) grains found are similar those observed previously in primitive meteorites and interplanetary dust particles, and indicate origins in oxygen‐rich red giant or asymptotic giant branch stars, or in supernovae. Four grains with anomalous C isotopic compositions were also detected. 12C/13C as well as Si ratios are similar to those of mainstream SiC grains; the N isotopic composition of one grain is also consistent with a mainstream SiC classification. Presolar silicate grains were found in three of the seven AMMs studied, and are heterogeneously distributed within these micrometeorites. Fourteen of the 18 presolar silicate grains and 3 of the 4 C‐anomalous grains were found within one AMM, T98G8. Presolar silicate‐bearing micrometeorites contain crystalline silicates that give sharp X‐ray diffractions and do not contain magnesiowüstite, which forms mainly through the decomposition of phyllosilicates and carbonates. The occurrence of this mineral in AMMs without presolar silicates suggests that secondary parent body processes probably determine the presence or absence of presolar silicates in Antarctic micrometeorites. |
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