Heavily irradiated grains and neon isotope anomalies in carbonaceous chondrites

High-voltage microscope observations of micron-sized grains extracted from a 22Ne-rich fraction of the Orgueil meteorite give strong experimental evidence for their heavy irradiation. It is further suggested that the excess of 22Ne measured in the same mineral separate can be explained by low-energy (<10 MeV) production by (p, a) reaction on 25Mg. A discussion of the astrophysical sites potentially responsible for the peculiar irradiation history of the meteoritic grains is presented