Chapter 39 - Enceladus

Abstract

Enceladus is a small icy moon of Saturn that is geologically active, with an uncratered, tectonized region at the south pole characterized by excess thermal emission and geysers of salty ice grains, water vapor, and organic compounds. Enceladus may undergo cycles of activity and dormancy. The activity likely derives from tidally driven opening and closing of cracks, allowing warm, water-filled fractures to periodically become exposed to vacuum, thus generating eruptive plumes. It possesses a regional sea beneath the south polar terrain (SPT), but probably not a global ocean. Its shell may be undergoing convection locally beneath the SPT, but not globally. At earlier times, other parts of Enceladus' surface were probably undergoing processes similar to what we see at the SPT today. Because it possesses liquid water, an energy source and organic molecules, and because its geysers are likely sourced in the regional sea below, Enceladus is home to a potentially habitable environment, the most accessible in the solar system.