Mimas touch

Look: Saturn's "Death Star" moon might have an ocean beneath its surface

It could redefine what it means to be an ocean world.

NASA/JPL/Space Science Institute

Meet Mimas, the smallest of Saturn’s eight major moons.

Its dominant crater makes it look a bit like the infamous Death Star from Star Wars.

Originally, researchers thought Mimas was frozen to the core.

But a new report in the journal Icarus reveals that this moon’s external layer might just be a cover for an inner ocean.

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Not only would that make Mimas an ocean world, but it would mark the discovery of a new class of “stealth” ocean worlds.

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NASA/JPL-Caltech/Space Science Institute

What makes Mimas different from the rest of the ocean worlds is that it doesn’t have obvious features on its surface that point to the existence of liquid water.

NASA/JPL-Caltech

Another one of Saturn’s moons, Enceladus, is thought to have an inner ocean, too.

But it has obvious signs of geologic activity, such as geysers that shoot water vapor and salt spray hundreds of miles above the surface.

Instead, there was another giveaway that revealed Mimas’ potential for an ocean: its wobble.

Looking at data from NASA’s Cassini mission, researchers realized that Mimas has a strange oscillation pattern during its orbit — an indicator that it is geologically active.

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Water churning beneath its surface was the most likely explanation for the moon’s wobble.

Researchers modeled the heat and energy patterns that an active ocean would likely create inside Mimas.

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Tides in Mimas’ ocean — which would be created by Saturn’s gravitational pull — would have to generate enough heat to keep the water in a liquid state.

But they would also have to be contained enough for the moon’s surface to still have an icy shell.

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NASA / JPL-Caltech / Space Science Institute

Future surveys of Mimas could verify the heat models that researchers created for the study.

But for now, it seems that Saturn’s smallest major moon has the potential to change our definition of what life-hosting bodies can look like.

“Turns out Mimas’ surface was tricking us, and our new understanding has greatly expanded the definition of a potentially habitable world in our solar system and beyond.”

Alyssa Rhoden, study co-author, in a statement.

NASA / JPL-Caltech / Space Science Institute