“What we’ve done is put forth a strong case for an ocean,” study coauthor David Stevenson, a professor of planetary science at CalTech, told The New York Times.
Stevenson and his colleagues noted that Enceladus’s gravity was weaker at its south pole, likely because of a depression in the underlying rock. But the gravity was somewhat higher than they would expect from an empty depression covered by the moon’s planet-wide ice sheet. “Then you say, ‘A-ha, there must be compensation,’” Stevenson told the Times. “Something more dense under the ice. The natural candidate is water.”
Apparently, the gravitational forces that Enceladus experiences as it orbits Saturn and interacts with a neighboring moon, Dione, create friction and heat that melts some of its icy coat to produce liquid water.
Researchers had previously detected sodium and potassium salts on the moon and determined that methane and ammonia were present in the plumes of water vapor that occasionally spew from its south pole. Add liquid water to this mix, and Enceladus may be a good place to look for living organisms, according to Leicester University mathematician Nikolai Brilliantov, who wasn’t involved with the research. “There are definitely regions on Enceladus where the conditions are such that life could exist. You have liquid water, you have chemicals and you have heat. And that is enough for life,” Brilliantov, who in 2008 proposed the theory that a liquid ocean underlies the jets of water squirting from Enceladus, told The Guardian. “To my mind, this is the best place we can expect to find life elsewhere in the solar system.”