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Updated: Jul 17, 2026

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Published on: July 2, 2012
Niobium-zirconium chronometry and early solar system development
Maria Schönbächler1, Mark Rehkämper, Alex N Halliday
1Institute of Isotope Geology and Mineral Resources, ETH Zürich, 8092 Zürich, Switzerland. maria@erdw.ethz.ch
Niobium-92 (92Nb) decay provides insights into early solar system processes. New research indicates the initial solar system 92Nb/93Nb ratio was low (<3 x 10(-5)), challenging previous high estimates and impacting models of planetary differentiation.
Area of Science:
- Cosmochemistry
- Nuclear Astrophysics
- Planetary Science
Background:
- Niobium-92 (92Nb) decay to Zirconium-92 (92Zr) with a 36-million-year half-life offers a chronometer for nucleosynthesis and early solar system events.
- Previous studies suggested a high initial abundance of 92Nb/93Nb in the solar system, potentially exceeding 10(-3).
Purpose of the Study:
- To determine the initial 92Nb/93Nb ratio of the solar system.
- To re-evaluate the implications for the timing of Earth's initial differentiation.
Main Methods:
- Analysis of Niobium-Zirconium (Nb-Zr) internal isochrons.
- Utilizing meteorite samples: ordinary chondrite Estacado (H6) and mesosiderite Vaca Muerta.
Main Results:
- Nb-Zr isochrons from both Estacado and Vaca Muerta consistently yield an initial 92Nb/93Nb ratio of approximately 10(-5).
- This implies the initial solar system ratio was less than 3 x 10(-5).
Conclusions:
- The solar system's initial 92Nb/93Nb ratio was significantly lower than previously proposed.
- This lower ratio suggests that Earth's initial differentiation may not have required an extended period, as some models had indicated.
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