THE EFFECTS OF FINE PARTICULATES ON THERMAL INFRARED EMISSIVITY SPECTRA: IMPLICATIONS FOR SOLAR SYSTEM AIRLESS BODIES
Here we present TIR emissivity laboratory measurements of (1) a suite of samples that have been ground and sieved to a range of particle size fractions (fine to coarse), (2) physical mixtures of the finest and coarsest particle size fraction of each sample measured and (3) physical mixtures of all of the particle size fractions combined in proportions expected in the regolith of airless bodies. Samples in this study include San Carlos olivine, Allende (CV3), and Murchison (CM2). We made thermal infrared emissivity measurements under simulated airless body environment (SAE) conditions using the Planetary Analogue Surface Chamber for Asteroid and Lunar Environments (PASCALE) at the University of Oxford.
Initial results for the physical mixtures of San Carlos olivine and Allende suggests that only 5 vol.% fine particulates are needed to start obscuring the spectral signatures of the coarse particulates. As increasing amounts of fines are added to the physical mixtures, we observe a reduction in the contrast of the fundamental vibration bands and an increase in contrast in transparent regions of the spectra. These laboratory measurements will better enable current observations of boulder-rich asteroids Bennu and Ryugu, and future observations of the Moon at higher spatial resolutions by L-CIRiS and Lunar Trailblazer.