A new spectral parameter to detect olivines and pyroxenes: application to ordinary chondrites.

The meteorites are an important resource in order to understand the composition of the asteroids of the Solar System. The most common meteorites are the ordinary chondrites and they are thought to come from S-type asteroids. These meteorites are usually characterized based on their VNIR (from visible to near infrared) spectra, thanks to the presence of two strong absorption bands located at 1 and 2 µm (called BI and BII, repectively). Ordinary chondrites are silicate dominated, and their two main absorp-tion bands are due to the presence of pyroxenes and olivines (Adams, 1974; Cloutis, et al., 1986; Cloutis, et al., 2015). OCs are subdivided on the basis of chemistry into three groups, the H, L and LL chondrites, for high total iron, low total iron and low total iron plus low metallic iron, respectively (Grady, 2014). To retrieve information about aster-oids composition from their VNIR spectra, a com-parison with meteorites spectra is necessary. The comparison is based on appropriate spectral param-eters specifically defined and calibrated on the basis of meteorites’ composition. This calibration implies that the composition of a set of meteorites (e.g., OCs) is known (e.g., through XRD), and that its variations can be associated to variations in the spectral parameters. In Dunn, et al., 2010 and Cloutis, et al., 1986, the parameter used for the calibration of OCs are the band center at 1 µm (BCI), the band center at 2 µm (BCII), the band area ratio (BAR) and reflectance values at defined wavelengths. The relationships found were then used on remote spectra of asteroids to retrieve their composition.