Astronomy
Tidal Heating and the Subsurface Ocean of Enceladus
Quick fact
Enceladus's subsurface ocean is kept liquid by tidal heating, not by the Sun. This heat also powers the geysers that shoot water vapor and ice grains into space from the south pole.
Why this is interesting
A tiny moon of Saturn, barely 500 kilometers across, is one of the most promising places to look for life beyond Earth. How can such a small world keep a liquid ocean inside its frozen shell?