Effect of Surface Roughness on X-Ray Fluorescence Emission from Planetary Surfaces

Laboratory experiments are being performed to understand X-ray fluorescence phenomena on regolith or rocky planetary surfaces, which occur on the day side of atmosphere-free planetary surfaces on Mercury, the moon, satellites, and asteroids. Our results are quite preliminary but show a clear tendency, dependent on the surface roughness with submillimeter scale, corresponding to the representative diameter of the Apollo lunar soils. This fact is considered important for remote-sensing X-ray fluorescence experiments to make a quantitative elemental analysis, and may be useful for estimation of average particle size of regolith layer from orbiting spacecraft in future planetary missions.