There's a Lake Superior-Sized Ocean Deep Under One of Saturn's Moons

Scientists have found a subsurface ocean of water on one of Saturn’s smallest moons—and it’s only a matter of time before someone proposes sending a robotized submarine to explore it.

Using measurements from NASA’s Cassini spacecraft, which has been orbiting Saturn and its moons for 10 years, researchers at CalTech and the Universita di Roma were able to determine that, near the moon Enceladus’ south pole, there’s an ocean of liquid water buried beneath at least 18 miles of ice that’s as large as Lake Superior.

“We detected this ocean by correlating gravity and topography,” Luciano Iess, lead author of a study explaining the study published in Science, told me. “Imaging shows a depression at the south pole, but the gravity there was not as small as we expected. There must be some denser material there which increased the gravity.”

That material, he thinks, is water, which is seven percent denser than ice. Combine that with the fact that geysers that shoot water vapor have been measured on Enceladus, and you’ve got good proof that there’s water deep under the surface.

Iess says that the water is likely salty and hovers somewhere near the freezing point of 0 degrees celsius, but it is certainly in a liquid state. The ocean might be as many as six miles deep.

“It’s a regional ocean that is rather deep,” he said.

Enceladus and Jupiter's moon, Europa, are the only two bodies in the outer solar system that have been confirmed to have water.

The question then becomes: What now?

Scientists have about exhausted the usefulness of Cassini’s ability to monitor Enceladus for water—its latest readings occurred during three flybys of the moon between 2010 and 2012. So, naturally, scientists are looking forward to what might be next. It’s not going to happen anytime soon, but Iess says that, eventually, a rover equipped with a submarine could be sent to explore the ocean.

“There’s such a large amount of interest in this small body, and certainly sooner or later we’ll go there with a penetrating submarine,” he said. “You could deploy a rover that could penetrate through this rather thick ice layer with heat. You can melt the ice and then by gravity, the submarine would get pushed down and would, sooner or later, end up in the ocean. It’s complicated, but that’s the target.”