Saturn’s Death Star Moon May Be a ‘Stealth’ Ocean World in Disguise

Saturn’s innermost moon Mimas may be hiding a vast underground ocean locked beneath its icy surface, according to the results of a new study.

Mimas is just one of 63 confirmed moons in Saturn’s eclectic family, which come in a dizzying array of shapes and sizes, from the stress-broken shape of Enceladus to the warped mass of Hyperion, which has a significantly higher density. lower than water.

What makes Mimas unique – beyond the fact that it orbits closer to the surface of Saturn’s clouds than any other large moon – is the large impact scar known as Herschel Crater, which dominates its faint features.

The cyclopean view afforded by the 80-mile (130 km) wide scar has led many to call it Saturn’s Death Star Moon, a reference to the iconic battle station from Star Wars.

View from NASA’s Cassini Probe

Now, a new study published in the journal Geophysical Research Letters has found evidence to suggest that Mimas is not really a (normal) moon, but rather a hidden oceanic world in disguise.

Near the end of its nearly 20-year mission, instruments aboard NASA’s Cassini spacecraft detected a subtle wobble in Mimas’ natural rotation. This unexpected discovery suggested either that Mimus was host to a strangely elongated rocky core or, more likely, that its icy shell covered a hidden ocean beneath the surface.

These theories led the authors of the new study to take a closer look at the violent impact that shaped Mimas’ Herschel Crater to see if they could reconcile that violent event with the presence of an internal ocean.

The team reconstructed its creation using advanced computer modeling software and found that the presence of a subsurface ocean did help explain the crater’s shape and depth, along with the moon’s general lack of surface fractures.

However, the models also showed that Mima’s icy outer shell must have been at least 34 miles (55 km) thick to survive the impact. Any thinner and that region of the ice shell would have been obliterated by the incredible energy delivered by the impact.

Since the present-day thickness of Mimas’ icy outer shell is estimated to be at most 19 miles (30 km) deep, this finding suggests that the small moon has undergone significant heating since the impact, leading to a of ice thickness.

The team also notes that, while their findings support the possibility that an ocean may exist on Mimas, it is still possible that the moon was completely frozen both today and at the point of impact. In that scenario, the strange characteristics of Mimas’ orbit must result from the shape of the moon’s core.

“Mimas seemed like an unlikely candidate, with its icy, heavily cratered surface marked by a giant impact crater that makes the small moon look a lot like the Death Star from Star Wars,” said Dr. Alyssa Rhoden of the Southwest Research Institute, who was one of the authors of the new study.

“If Mimas has an ocean, it represents a new class of small ‘hidden’ oceanic worlds with surfaces that don’t betray the existence of an ocean.”

The scientists note that future unmanned missions to the Saturnian system would be valuable in uncovering the secrets of Mimas’ evolution, and that the moon “may be the first example of a new pathway for the formation of potentially habitable oceanic worlds.”

Image credit: NASA/JPL/SSI

Anthony is a freelance contributor covering science and video game news for IGN. He has over eight years of experience covering groundbreaking developments in multiple scientific fields and has absolutely no time for your shenanigans. Follow him on Twitter @BeardConGamer