The North Pole of Enceladus during the October 30th, 2015 Cassini Flyby (NASA/ESA/ASI)

Since 2004, the Cassini spacecraft has been in orbit around Saturn. The robot probe (a joint effort of NASA, ESA, and the Italian space agency) received the most press when it launched a flying saucer lander onto Saturn’s planet-like moon Titan, but it is still out there doing amazing work. Last week, while I was busy writing about Halloween themes, the probe made its closest pass yet to Saturn’s ice moon, Enceladus. Enceladus is only 500 kilometers in diameter and it is coated in ice, but it is of great interest to scientists because ice plumes venting from the moon’s south pole seem to indicate a large polar subsurface ocean of liquid water. Warmed above freezing by tidal flux, this ocean beneath the ice probably has a thickness of around 10 km.

View of Enceladus’ south pole…