In search of a seltzer sea

Saturn's mysterious moon Enceladus-which floats just beyond the giant planet's icy belt of rings-appears to be home to a vast subterranean ocean of seltzer water. The dark deeps of this warm, fizzy sea may be home to alien pelagic creatures, both large and small. But there's a long way to go before plunging into the depths of this alien ocean.

According to Dennis Matson of NASA's Jet Propulsion Laboratory, evidence of the moon's ocean started mounting back in 2005 when NASA's Cassini robot spacecraft zipped past Enceladus.

"Geophysicists expected this little world to be a lump of ice, cold, dead, and uninteresting," Matson said during a recent NASA news briefing announcing the discovery of the alien exolunar sea. "Boy, were we surprised!"

The big surprise came when Cassini radioed back digital photographs of several weird, icy jets of water vapor-the jest were exhaling sparkling icy particles and gobs of organic compounds. Matson said all this stuff was being blown out through geyser like vents in huge fissures along Enceladus' frozen, crater pocked and billiard ball-like surface. The beautiful blue fissures are now called tiger stripes (see photo).

Matson said that after examining images and related data, NASA scientists concluded that pockets of liquid water-with temperatures hovering at or just above the freezing point-were the only possible reason for the geysers. However, scientists expected to find signatures of salt water, but the salt was missing from the data.

"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," according to NASA's Dauna Coulter. "But in 2009 Cassini's cosmic dust analyzer located the missing salt-in a surprising place."

Matson continued: "It wasn't in the plume gasses where we'd been looking for it. 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."

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