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Published February 15, 1978 | Published
Journal Article Open

Calcium Isotopic anomalies in the Allende meteorite


We report isotopic anomalies in Ca which were found in two Ca-Al-rich inclusions of the Allende meteorite. These inclusions previously had been shown to contain special anomalies for Mg and O which were attributed to fractionation and unknown nuclear effects. The Ca data, when corrected for mass fractionation by using ^(40)Ca/^(44)Ca as a standard show nonlinear isotopic effects in ^(48)Ca of + 13.5 per mil and in ^(42)Ca of +1.7 per mil for one sample. The second sample shows a ^(48)Ca depletion of - 2.9 per mil, but all other Isotopes are normal. Samples with large excesses in ^(26)Mg show no Ca anomalies. The effects demonstrate that isotopic anomalies exist for higher-atomic-number refractory elements in solar-system materials and do not appear to be readily explainable by a simple model. The correlation of O, Mg, and Ca results on the same inclusions requires the addition and preservation in the solar system of components from diverse nucleosynthetic sources. Observed anomalous Mg. and Ca compositions for coexisting mineral phases are uniform within each inclusion, and require initial isotopic homogeneity within an inclusion but the preservation of wide variations between inclusions. Assumming formation of these inclusions by condensation from a gaseous part of the solar nebula, this Implies Isotopic heterogeneity on a scale of 10-10^2 km within the nebula.

Additional Information

© 1978 American Astronomical Society. Received 1977 October 14; accepted 1977 November 10. In 1973 October the authors met in conference with W. A. Fowler, T. A. Tombrello, J. C. Huneke, and S. E. Woosley in the Lauritsen Library of the Kellogg Radiation Laboratory to discuss candidates for identifying exotic nuclear components in early solar-system "condensates" which were then known to have an excess of 16O. That discussion plus the interest expressed by S. Woosley gave support to the endeavors reported here and aided the junior author in persuading the senior author to again pursue this work. We wish to acknowledge our debt to W. A. Russell for freely making available his knowledge of Ca and its isotopes. We have benefited from the interchange of both samples and ideas with R. N. Clayton. We thank H. Nagasawa for generously offering sample EKl-4-1. S. Epstein kindly provided us with his O analysis of sample WA. We would like to acknowledge the pleasure of sharing our excitement in real time with Dick Feynmann, who, as always, improved our own understanding in the process. This work was supported by NSF grant PHY 76-83685 and NASA grant NGL 05-002-188.

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Published - 1978ApJ___220L__21L.pdf


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