Nice animation zooming in on the icy moon Enceladus. Scientists did not originally consider the possibility of tectonic activity on the small moons of the outer solar system. The spectacular volcanoes of Io were guessed at shortly before the 1979 Voyager I flyby. But Io is about the size of Earth’s moon, and is tugged at by bodies similar in size to our moon (Europa and Ganymede) at distances similar to the earth-moon distance. In retrospect, volcanoes were a logical consequence of Io’s orbital dynamics.
But what happened or is happening on Enceladus?