Samarium-146 in the Early Solar System: Evidence from Neodymium in the Allende Meteorite

Science  02 Dec 1983:
Vol. 222, Issue 4627, pp. 1015-1018
DOI: 10.1126/science.222.4627.1015


A carbon-chromite fraction from the Allende C3V chondrite shows strikingly large isotopic enrichments of neodymium-142 (0.47 percent) and neodymium- 143 (36 percent). Both apparently formed by alpha decay of samarium-146 and samarium-147 (half-lives 1.03 x 108 and 1.06 x 1011 years), but the isotopic enrichment was greatly magnified by recoil of residual nuclei into a carbon film surrounding the samarium-bearing grains. These data provide an improved estimate of the original abundance of extinct samarium-146 in the early solar system [146Sm/144Sm = (4.5 ± 0.5) x 10-3], higher than predicted by some models of pprocess nucleosynthesis. It may be possible to use this isotopic pair as a chronometer of the early solar system.

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