DISCOVERY AND ANALYSIS OF MINOR ABSORPTION-BANDS IN S-ASTEROID VISIBLE REFLECTANCE SPECTRA

Two minor absorption bands in the visible range of the S-class asteroi d reflectance spectra have been discovered. The CCD reflectance spectr a of 10 S asteroids were deconvolved using the modified Gaussian model , and 9 of them are shown to have two minor absorption bands centered around 0.60 and 0.67 mu m in wavelength. Among the tested common geolo gic minerals, the obtained absorption-band centers and widths of the S asteroids were most consistent with those of oxidized Fe-Ni metal and spinel-group minerals. These results are consistent with the idea tha t the S asteroids are made of stony-iron-like material and the recent identification of two spinel-bearing S asteroids based on the comparis on of the 1- and 2-mu m band strengths. Because both oxidized iron com pounds and spinel-group minerals have spectral features very different from the S-asteroid ones in a wider wavelength region, they must be a t most minor constituents in the S-asteroid surface regoliths. (C) 199 6 Academic Press,Inc.