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Nature11 July 2002

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Meteoric nanodiamonds: Stardust memories

A Nature paper in 1987 reported the discovery of tiny grains of
presolar diamond in meteorites. These 'nanodiamonds' are regarded as the most abundant form of presolar material or 'stardust'. But the isotopic evidence supporting their origins, principally the presence of exotic xenon, is
ambiguous. If nanodiamonds are presolar they should be more abundant in comets than in asteroids, as more presolar material should survive further from the Sun. Now a comparison of the Murchison and Orgueil meteorites with interplanetary dust particles collected in the stratosphere suggests that nanodiamonds are conspicuously depleted in cometary material. This may mean that some or most nanodiamonds are not presolar at all, but formed in the early Solar System.

letters to nature
Possible in situ formation of meteoritic nanodiamonds in the early Solar System
Z. R. DAI, J. P. BRADLEY, D. J. JOSWIAK, D. E. BROWNLEE, H. G. M. HILL & M. J. GENGE
Nature 418, 157–159 (2002); doi:10.1038/nature00897
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