Enceladus, a small moon orbiting Saturn, has a watery ocean beneath its frozen surface, according to an analysis of data from NASA's Cassini spacecraft.

By Amina Khan

Saturn’s icy moon Enceladus has earned a certain amount of attention for its waterworks show — it was caught squirting plumes of mineral-rich water out of “tiger stripe” cracks near its south pole in 2005. Scientists thought that could be a sign of a liquid ocean beneath its frozen shell, but couldn’t be sure. Now, using data from NASA’s Cassini spacecraft, they have found gravitational evidence that a vast sea the size of Lake Superior could extend out from around the southern pole.

The discovery, described in the journal Science, lends support to the idea that this tiny world is one of the few places in our own solar system that could be potentially friendly to life.

At just 313 miles across, Enceladus is a frozen dirtball that’s too small to stay warm, so how could it have liquid water beneath the surface? The answer lies in its strange gravitational love triangle with ringed gas giant Saturn and Dione, another moon. Dione also tugs on Enceladus’s orbit, stretching its path around Saturn from a circle to an ellipse. The gravitational pull from these two bodies also squeezes and stretches the moon itself, and all that kneading from this tidal distortion heats Enceladus, melting some of the water ice under the surface.

Anyway, that’s the theory. The search for this subsurface ocean warmed up after scientists discovered plumes of mineral-rich water vapor squirting out of cracks near the south pole. But they couldn’t be sure it was coming from liquid water below, rather than from the ice at the surface.

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