Enceladus is the sixth-largest moon of
Saturn. It is about 500 kilometers in diameter, about a tenth of that
of Saturn's largest moon, Titan. Enceladus is mostly covered by fresh,
clean ice, making it one of the most reflective bodies of the Solar
System.
For decades, scientists didn’t know why Enceladus was the brightest
world in the solar system, or how it related to Saturn’s E ring.
Cassini found that both the fresh coating on its surface, and icy
material in the E ring originate from vents connected to a global
subsurface saltwater ocean that might host hydrothermal vents.