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Rapid accretion and early core formation on asteroids and the terrestrial planets from Hf-W chronometry
The timescales and mechanisms for the formation and chemical differentiation of the planets can be quantified using the radioactive decay of short-lived isotopes. Of these, the 182Hf-to-182W decay is ideally suited for dating core formation in planetary bodies. In an earlier study, the W isotope com...
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Published in: | Nature (London) 2002-08, Vol.418 (6901), p.952-955 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | The timescales and mechanisms for the formation and chemical
differentiation of the planets can be quantified using the radioactive decay of
short-lived isotopes. Of these, the
182Hf-to-182W decay is ideally suited for dating
core formation in planetary bodies. In an earlier
study, the W isotope composition of the Earth's mantle was
used to infer that core formation was late (≥60 million years
after the beginning of the Solar System) and that accretion was a protracted
process. The correct interpretation of Hf-W data
depends, however, on accurate knowledge of the initial abundance of
182Hf in the Solar System and the W isotope composition of
chondritic meteorites. Here we report Hf-W data for carbonaceous and H
chondrite meteorites that lead to timescales of accretion and core formation
significantly different from those calculated previously. The revised ages for Vesta, Mars and Earth indicate
rapid accretion, and show that the timescale for core formation decreases with
decreasing size of the planet. We conclude that core formation in the
terrestrial planets and the formation of the Moon must have occurred during the
first ∼30 million years of the life of the Solar System. |
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ISSN: | 0028-0836 1476-4687 |
DOI: | 10.1038/nature00982 |