Silicate Mixtures Under Simulated Lunar Environment with Applications to Diviner Lunar Radiometer

Remote sensing is a primary source of information about planetary surfaces, thus it is imperative that we are able to quantitatively interpret remote spectral data. Because remote sensing relies in part on comparison to laboratory data, we must also understand how environmental conditions affect spectral features, and impact our interpretation of remote sensing data. Differences in environmental conditions become especially important when comparing laboratory data measured on Earth to remote sensing data from airless bodies, such as the Moon and asteroids. Without an atmosphere, these planetary surfaces experience extreme temperature gradients within the upper 100's of microns of regolith. These temperature gradients result in the measurement of regolith at multiple temperatures with each observation, which complicates the analysis of mid-infrared spectral data. Therefore, we must measure minerals and regolith samples under environmental conditions similar to those of the target bodies. Here, we describe measurements of minerals and mixtures of minerals under a simulated lunar environment, and examine effects on regolith spectra. These effects largely consist of shifts in the Christiansen Feature (CF) and increases in the depths of Reststrahlen bands. Our work shows that the CF shifts both under the simulated lunar environment, and due to particle size fraction of the sample. We also convolve our laboratory spectra to the Diviner Lunar Radiometer bandpasses to assess our ability to identify spectral variation within this lunar mid-infrared dataset. This work contributes to our interpretation of spectra of mineral mixtures. The dominance of fine particulates on the lunar surface prevents the typical treatment of mid-infrared spectra as a linear combination of the mineral constituents. Applying this work to Diviner data will help us to quantitatively interpret the mineralogy of the lunar surface.