Astronomers find evidence of ocean world beneath surface of Saturn's tiny 'Death Star' moon

The appearance of one of Saturn's smallest moons lends it the nickname "Death Star," but astronomers say new evidence suggests the world is, in fact, home to an ingredient vital for life: water.

And lots of it.

Observations made possible by NASA's Saturn-probing Cassini spacecraft led to the discovery that a vast liquid ocean is teeming beneath the icy exterior of Mimas.

A French-led team found evidence to suggest that the ocean formed 5 million to 15 million years ago on Mimas – relatively new compared to the ancient ocean moons Enceladus and Europa. The findings, published Wednesday in the journal Nature, would make the tiny moon a prime location for astronomers to study the origins of life in the solar system.

"Its heavily cratered surface gave no hint of the hidden ocean beneath," co-author Nick Cooper of Queen Mary University of London said in a statement. "This discovery adds Mimas to an exclusive club of moons with internal oceans."

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Scientists turn to Cassini spacecraft to make Mimas observations

The scientists made their findings by studying data from the Cassini spacecraft, which observed Saturn and its moons for more than a decade before burning up in the planet's atmosphere in 2017.

Changes in the orbit and rotation of Mimas revealed that an ocean lurking up to 18 miles beneath the frozen crust was more likely than an elongated rocky core, the researchers discovered. Analysis of Mimas' tidal interactions with Saturn led the team to further conclude the ocean's relatively young age.

Mimas' neighboring moon, Enceladus, is famous for its water-spouting geysers that offer tangible clues to its subterranean saltwater ocean, according to NASA.

But at first glance, Mimas doesn't resemble a world capable of harboring a vast body of liquid, making for quite an unexpected revelation.

"The major finding here is the discovery of habitability conditions on a solar system object which we would never, never expect to have liquid water," Valéry Lainey, the French astronomer who led the team of researchers from Observatoire de Paris, told "It's really astonishing."

Further study of moon could aid in search for life

One of the smallest of Saturn's 146 estimated moons, Mimas was discovered in 1789 by English astronomer William Herschel and named after a giant in Greek mythology.

Despite being just 250 miles in diameter, Mimas is home to the second-largest impact crater of any moon in the solar system. At 80 miles wide, the giant crater named after Herschel stretches a third of the way across the face of the moon, spawning its comparison to the famous Death Star space station in the fictional "Star Wars" universe.

The heavily cratered moon lacks the tell-tale signs of subterranean ocean activity such as fractures and geysers that exist on Enceladus and Jupiter’s Europa.

The ocean would be too young to mark the moon’s surface, but lurking beneath would be a subterranean ocean with freezing temperatures giving way to warmer waters closer to the seafloor, researchers said.

The discovery of Mimas' young ocean is proof, the study's authors say, that even small, seemingly inactive moons can harbor hidden life-supporting conditions. The researchers hope their findings lead to further exploration and study of the small moon.

“The existence of a recently formed liquid-water ocean makes Mimas a prime candidate for study for researchers investigating the origin of life," Cooper said.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at

This article originally appeared on USA TODAY: Saturn's 'Death Star' moon Mimas may harbor ocean beneath its surface