Most small moons tend to be old and geologically inactive. Explain why Enceladus appears to break that general rule

Question

What will be an ideal response?

Answer 1

The smaller moons of Saturn are icy worlds battered by impact craters, and you can suspect that they are cold and old. Small worlds lose their heat quickly, and with no internal heat, there is no geological activity to erase impact craters. A small, icy world covered with craters is exactly what you would expect in the outer solar system. Enceladus, however, is peculiar. Although it is small and icy, its surface is highly reflective, and some areas contain fewer craters than you would expect. In fact, some regions seem almost free of craters. Grooves and faults mark some regions of the little moon and suggest motion in the crust. These features should have been destroyed long ago by impact cratering, so you must suppose that the moon has been geologically active at some time since the end of the heavy bombardment at the conclusion of planet building. The water vents discovered at the south pole of Enceladus show the moon is still active.