Microspectroscopy is a potentially useful tool for planetary applications, as individual mineral grains can be targeted and measured in situ. A series of closely coupled experiments was designed to investigate and compare the laboratory measurement of optical properties of a peridotite sample in the macroscale and microscale. The Ronda peridotite consists largely of olivine with significant orthopyroxene and minor clinoproxene and serpentine. Microscopic transmission spectra of unmounted thin sections produce strong, well-defined absorption features in the near infrared, and band positions can be directly compared to macroscopic and microscopic reflectance spectra. For near-infrared reflectance, where photons are multiply scattered by different grains, measurement of a microscopic target means most photons are scattered out of the field of view and few photons return to the detector from the target area. This precludes most microspectroscopic reflectance measurements of small features in the near infrared. In the mid-infrared, where reflectance measurements involve only surface interactions, microspectroscopic measurements detect well-defined absorption features for most samples. Although the intensity of absorption features varies between grains, band positions are consistent with macroscopic diffuse reflectance and emittance measurements of bulk samples, and can be used to extract general chemical information such as iron/magnesium ratios of olivines.
