Spectral alteration of the Meteorite Epinal (H5) induced by heavy ion irradiation: a simulation of space weathering effects on near-Earth asteroids

We present results obtained for Epinal (H5), an ordinary chondrite meteorite, irradiated with 60 keV At++ ions, simulating solar wind heavy particle irradiation. Bidirectional reflectance spectra (0.3-2.67 mu m) measured after irradiating Epinal samples with different ion fluences exhibit a progressive reddening that is similar to the spread of spectra observed for S-type near-Earth asteroids. The timescales for inducing the same effects in space as those obtained in laboratory are estimated to be 10(4)-10(6) yr. These results suggest irradiation by heavy ions may be a very efficient weathering process in near-Earth space. (c) 2004 Elsevier Inc. All rights reserved.