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Science 1 October 2004:
Vol. 306. no. 5693, pp. 89 - 91
DOI: 10.1126/science.1101014
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Reports

Extinct 244Pu in Ancient Zircons

Grenville Turner,1* T. Mark Harrison,2,3 Greg Holland,1 Stephen J. Mojzsis,4 Jamie Gilmour1

We have found evidence, in the form of fissiogenic xenon isotopes, for in situ decay of 244Pu in individual 4.1- to 4.2-billion-year-old zircons from the Jack Hills region of Western Australia. Because of its short half-life, 82 million years, 244Pu was extinct within 600 million years of Earth's formation. Detrital zircons are the only known relics to have survived from this period, and a study of their Pu geochemistry will allow us to date ancient metamorphic events and determine the terrestrial Pu/U ratio for comparison with the solar ratio.

1 Department of Earth Sciences, University of Manchester, Manchester M13 9PL, UK.
2 Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia.
3 Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, USA.
4 Department of Geological Sciences, Center for Astrobiology, University of Colorado, Boulder, CO 80309–0399, USA.

* To whom correspondence should be addressed. E-mail: grenville.turner{at}man.ac.uk

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