Martian surface properties indicated by the opposition effect

Opposition measurements made by the Viking Orbiter television cameras in the Arabia, Syrtis Major, and Elysium Planitia regions have been combined with observations previously reported to provide a photometric comparison of these areas and several generic features. Radiative transfer expressions were used to derive average surface particle single-scattering albedos, phase functions, and porosities. Best functional fit to the data includes consideration of atmospheric scattering, two-particle populations, and surface roughness. Several findings include the ubiquitous presence of high-albedo, high-porosity surface particles; the absence of an opposition surge in the Syrtis Major region; and the largest surface roughness in the Chryse areas.