Voyager 2 obtained the best views of Saturn’s moon Enceladus in August 1981. The surface of Enceladus contains abundant evidence of a complex and active history. Portions of the satellite have numerous impact craters, implying great age, while other areas are almost entirely devoid of craters and are thus much younger. Several fractures are visible and some fractures are crosscut and offset by subsequent faults. Enceladus has a very bright surface, reflecting more than 90% of the incident sunlight, so that very little dark material (dust or rock) can be incorporated into the surface ice. All these observation indicate that this small satellite (only 500 kilometers or 300 miles in diameter) remained very active, while other saturnian satellites became thoroughly saturated with impact craters. The force behind this activity may be gravitationally driven tidal forces much like those responsible for the spectacular volcanos on Io.
Voyager 1 image (Press Release P-24308).