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Science 1 March 2002:
Vol. 295. no. 5560, pp. 1705 - 1708
DOI: 10.1126/science.1067400
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Reports

Niobium-Zirconium Chronometry and Early Solar System Development

Maria Schönbächler,1* Mark Rehkämper,1 Alex N. Halliday,1 Der-Chuen Lee,1 Michèle Bourot-Denise,3 Brigitte Zanda,34 Bodo Hattendorf,2 Detlef Günther2

Niobium-92 (92Nb) decays to zirconium-92 (92Zr) with a half-life of 36 million years and can be used to place constraints on the site of p-process nucleosynthesis and the timing of early solar system processes. Recent results have suggested that the initial 92Nb/93Nb of the solar system was high (>10-3). We report Nb-Zr internal isochrons for the ordinary chondrite Estacado (H6) and a clast of the mesosiderite Vaca Muerta, both of which define an initial 92Nb/93Nb ratio of ~10-5. Therefore, the solar system appears to have started with a ratio of <3 × 10-5, which implies that Earth's initial differentiation need not have been as protracted as recently suggested.

1 Institute of Isotope Geology and Mineral Resources,
2 Laboratory of Inorganic Chemistry, ETH Zürich, 8092 Zürich, Switzerland.
3 Museum national d'Histoire naturelle, 75005, Paris, France.
4 Rutgers University, Department of Geological Sciences, Wright Lab, Piscataway, NJ 08854-8066, USA.
*   To whom correspondence should be addressed. E-mail: maria{at}erdw.ethz.ch

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
An Overview of Isotopic Anomalies in Extraterrestrial Materials and Their Nucleosynthetic Heritage.
J. L. Birck (2004)
Reviews in Mineralogy and Geochemistry 55, 25-64
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The inner inner core of Earth.
D. L. Anderson (2002)
PNAS 99, 13966-13968
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