THERMAL EMISSION CHARACTERISTICS OF MINERAL DUSTS

ABSTRACT The spectral thermal emission of micron size powders of andesite, basalt, augite, olivine, serpentine, granodiorite, obsidian, quartz, and a chondritic meteorite has been measured in the 7–14 micron wavelength region at a temperature of 250°C. The emission spectra of these materials, when ground to a particle size comparable with the best estimates of the particle size of the lunar surface material, showed no unique spectral characteristics which could be used to identify the mineral. Only at larger particle sizes did significant structure appear in the spectral emission curve. These results suggest that, if the particle size of the lunar surface material is as small as present estimates indicate, compositional mapping of the moon remote infrared sensing is not feasible. A theoretical treatment shows that the structure of the surface material - i.e., particle size, particle shape, and density of the medium, as well as its composition, will determine the infrared emission characteristics.