Modeling asteroid surfaces from observations and irradiation experiments: The case of 832 Karin

We define a new approach to model asteroidal space weathering. We started from recent results of ion irradiation experiments (60-400 keV) of meteorites and silicates to give an accurate description of space weathering, and we included its effects in the Shkuratov model. We found that the reddening and darkening process (in the range 0.3-2.5 mu m) does not significantly affect the position or relative intensities of the mafic silicate absorption features and it mainly affects the continuum of reflectance spectra. This continuum is parameterized by a C-S coefficient, which is strongly related with the number of displacements per unit area (damage parameter); we consequently obtained an exposure time curve, and corresponding astrophysical timescales. We applied this new description of space weathering to model observed spectra of Asteroid 832 Karin, in the 0.4-2.4 mu m spectral region. The obtained exposure time is slightly lower than the age of the impact and collisional breakup which originated the Karin asteroidal family, i.e., about 5.75 x 10(6) years. (c) 2006 Elsevier Inc. All rights reserved.