Molybdenum isotopic composition of individual presolar silicon carbide grains from the Murchison meteorite.
We report the isotopic composition of molybdenum in twenty-three presolar SiC grains from the Murchison meteorite which have been measured by resonant ionization mass spectrometry (RIMS). Relative to terrestrial abundance (and normalized to s-process-only {sup 96}Mo), the majority of the analyzed grains show strong depletions in the p-process isotopes {sup 92}Mo and {sup 94}Mo and the r-process isotope {sup 100}Mo. Sixteen of these grains have {delta}-values {le} 600% for these three isotopes. The observed isotopic patterns of Mo from mainstream SiC grains clearly reveal the signature of s-process nucleosynthesis. Three-isotope plots of all grain data ({delta}{sup i}Mo vs. {delta}{sup 92}Mo) show strong linear correlations with characteristic slopes. This finding suggests mixing of solar-like material and pure s-process material in the parent stars. Comparison with evolutionary calculations of nucleosynthesis and mixing in red giants suggests that low-mass thermally-pulsed symptotic giant branch (TP-AGB) stars are the most likely site for the observed s-process nucleosynthesis.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- National Aeronautics and Space Administration (NASA); ER
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 938150
- Report Number(s):
- ANL/CHM/JA-27599; GCACAK; TRN: US200906%%532
- Journal Information:
- Geochim. Cosmochim. Acta, Vol. 62, Issue 6 ; Mar. 1998; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- ENGLISH
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Molybdenum Isotopes in Presolar Silicon Carbide Grains: Details of s -process Nucleosynthesis in Parent Stars and Implications for r - and p -processes