Emission spectra of particulate silicates under simulated lunar conditions

Infrared spectra have been acquired under simulated lunar conditions that demonstrate that, contrary to popular belief, features of high spectral contrast are available for small-particle-size samples. The spectral information occurs in the form of emission maxima that are associated with the principal Christiansen frequencies, and these maxima are diagnostic of gross composition. The features represent a 5 to 30% effect, depending on particle size and composition. The effect is explained in terms of the sharp thermal gradients produced close to the surface under lunar conditions.