Io: Galileo evidence for major variations in regolith properties

Galileo SSI images taken at different times early in the Jupiter orbital tour show striking, widespread changes in Io's color and albedo patterns that result from observing the satellite's surface at different lighting and viewing geometries. Such changes indicate significant variations in the photometric or light-scattering behavior of the Ionian surface from region to region, and thereby provide strong evidence for major lateral variations in regolith properties. In particular, the regolith particles in Io's bright equatorial band appear to be larger than, or have a higher density of internal scatterers than, those in the satellite's higher-latitude regions. Such heterogeneity is not surprising on Io, given the rapid rate of volcanic resurfacing.