Surficial textures of the Galilean satellites

Knowledge of the textural characteristics of planetary surfaces is one of the objectives of remote sensing observations. The comparison of accurate photometric measurements with scattering models yields estimates of the compaction state of the optically active portion of the regoliths of airless bodies. We have analysed as a function of solar phase angle the observations of the Galilean satellites of Jupiter obtained with the International Ultraviolet Explorer^1,2. By fitting the measurements to a shadowing model³, comparative descriptions of the microtextures of the optically active portion of the surfaces of the satellites are derived. Important differences among the satellites, and between leading and trailing hemispheres of individual satellites, result from the different processes of meteoritic bombardment, magnetospheric interaction and geological resurfacing that operate in the Jovian system. lo and Callisto have the most tenuous upper regoliths, whereas the surface of the leading side of Europa is the most compact.