Meteorite-asteroid spectral comparison: The effects of comminution, melting, and recrystallization

Abstract

Laboratory results from a simulation of the possible effects of spectral alteration on reflectance of the optical surface of ordinary chondrite parent bodies is presented. Diffuse reflectance spectra from 0.3 to 2.6 μm were obtained for three chondritic meteorites. To simulate possible regolith processes the samples were comminuted to finer grain sizes, and the effect of communution on their reflectance spectra was measured. Following comminution, the samples were melted, recrystallized, recomminuted, and remeasured. These laboratory alterations produced a decrease in absorption band depths at 0.95 μm, and melting and recrystallization produced a significant drop in albedo. A reddening of the continuum, as previously reported for CM meteorites upon comminution and for lunar samples upon vitrification, also occurred for OC meteorites to a minor extent. Thus, although it was found that spectral characteristics could each be significantly changed by these procedures, no set of procedures was able to simultaneously affect all relevant parameters in such a way as to improve the match between ordinary chondritic meteorites and S-class asteroids. These results are consistent with what is known of the physical aspects of asteroid regolith evolution and also with the existence of several currently satisfactory spectral matches between meteorites and asteroid spectral classes.