Research Article

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

Science  08 Apr 2005:
Vol. 308, Issue 5719, pp. 223-227
DOI: 10.1126/science.1108140

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Abstract

The canonical initial 26Al/27Al ratio of 4.5 × 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.

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