A Fizzy Ocean on Enceladus


For years researchers have been debating whether Enceladus, a tiny moon floating just outside Saturn’s rings, is home to a vast underground ocean. Is it wet, or not? Now, new evidence is tipping the scales. Not only does Enceladus likely have an ocean, that ocean is probably fizzy like a soft drink and could be friendly to microbial life.

The story begins in 2005 when NASA’s Cassini probe flew past Enceladus for a close encounter.

"Geophysicists expected this little world to be a lump of ice, cold, dead, and uninteresting," says Dennis Matson of NASA’s Jet Propulsion Laboratory. "Boy, were we surprised!"


Many researchers viewed the icy jets as proof of a large subterranean body of water. Near-surface pockets of liquid water with temperatures near 32 degrees Fahrenheit could explain the watery plumes. But there were problems with this theory. For one thing, where was the salt?

In initial flybys, Cassini’s instruments detected carbon, hydrogen, oxygen, nitrogen, and various hydrocarbons in the plume gasses. But there were none of the elements of salt that ocean water should contain.

A close-up view of a Tiger stripe on Enceladus obtained by Cassini in 2008. Does a fizzy ocean lie underneath? Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA

In 2009 Cassini’s cosmic dust analyzer located the missing salt – in a surprising place.

"It wasn’t in the plume gasses where we’d been looking for it," says Matson. "Instead, sodium and potassium salts and carbonates were locked up in the plumes’ icy particles.* And the source of these substances has to be an ocean. Stuff dissolved in an ocean is similar to the contents of these grains."

The latest Cassini observations presented another intriguing discovery: thermal measurements revealed fissures with temperatures as high as minus 120 degrees F (190 Kelvin).







Another mystery remains: "Where’s the heat coming from on this tiny body?" wonders Larry Esposito of the University of Colorado. "We think tidal heating could be contributing."

Saturn’s powerful tides actually cause the shape of Enceladus to change slightly as it orbits. Flexing motions in the moon’s interior generate heat–like the heat you feel in a paperclip when you rapidly bend it back and forth. In this model, internal friction powers volcanic activity, which warms and melts the ice.


No one knows for sure what’s going on under the ice, but it seems this little moon has quite a story to tell: erupting jets, an underground ocean, the possibility for life.