The geologically active Enceladus
Space.com
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Cassini passed through the plume stretching up to 300 miles above Enceladus' surface in July. During that flyby, instruments aboard the spacecraft measured the plume's makeup and found water vapor and icy particles.
Credit: NASA/JPL/Space Science Institute
Also see CICLOPS for The Fountains of Enceladus.
Plenty of reasons for a new mission to the Saturnian system.