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Originally published in Science Express on 3 March 2005
Science 8 April 2005:
Vol. 308. no. 5719, pp. 223 - 227
DOI: 10.1126/science.1108140
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Research Articles

Supra-Canonical 26Al/27Al and the Residence Time of CAIs in the Solar Protoplanetary Disk

Edward D. Young,1,2* Justin I. Simon,2 Albert Galy,3 Sara S. Russell,4 Eric Tonui,2 Oscar Lovera2

The canonical initial 26Al/27Al ratio of 4.5 x 10-5 has been a fiducial marker for the beginning of the solar system. Laser ablation and whole-rock multiple-collector inductively coupled plasma-source mass spectrometry magnesium isotope analyses of calcium- and aluminum-rich inclusions (CAIs) from CV3 meteorites demonstrate that some CAIs had initial 26Al/27Al values at least 25% greater than canonical and that the canonical initial 26Al/27Al cannot mark the beginning of solar system formation. Using rates of Mg diffusion in minerals, we find that the canonical initial 26Al/27Al is instead the culmination of thousands of brief high-temperature events incurred by CAIs during a 105-year residence time in the solar protoplanetary disk.

1 Institute of Geophysics and Planetary Physics
2 Department of Earth and Space Sciences, University of California–Los Angeles, Los Angeles, CA 90095, USA.
3 Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK.
4 The Natural History Museum, London SW7 5BD, UK.

* To whom correspondence should be addressed. E-mail: eyoung{at}ess.ucla.edu

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