Saturn’s dead moon star may be a ‘hidden’ oceanographer in disguise – IGN
Saturn’s innermost moon Mimas may be hiding a vast subsurface ocean locked away beneath its icy surface, according to the findings of a new study.
Mimas is just one of Saturn’s eclectic family of 63 confirmed moons, which come in a dizzying array of shapes and sizes, from the squeeze-wracked shape of Enceladus to the distorted hyperion cluster, which has a density far less than that of water.
What makes Mimas unique — other than the fact that it orbits much closer to Saturn’s cloud surface than any other major moon — is the extensive impact scar known as Herschel Crater, which dominates its etched features.
The circular appearance given by an 80-mile (130 km) wide wound has led many to call it the moon of Saturn’s Death Star, a reference to the famous battles from Star Wars.
Now, a new study published in the journal Geophysical Research Letters has found evidence to suggest that Mimas isn’t really a (normal) moon, but rather a hidden ocean world in disguise.
Towards the end of its nearly 20-year mission, instruments aboard NASA’s Cassini spacecraft detected a subtle wobbling in Mimas’ natural rotation. This unexpected discovery suggests that Mimus’ hosted a strangely elongated rocky core, or, more likely, that its icy mantle obscures a hidden ocean beneath the surface.
These theories prompted the authors of the new study to take a closer look at the violent impact that shaped Mimas’ Herschel Crater in order to see if they could reconcile that violent event with an internal setting.
The team reconstructed its creation using advanced computer modeling software, and discovered that the presence of a subsurface ocean did indeed help explain the crater’s shape and depth, along with the moon’s general lack of surface fractures.
However, the models also showed that Mimas’ icy outer shell would have to be at least 34 miles (55 km) thick in order to survive the impact. Any thinner, and that area of the ice crust would have been obliterated by the massive energy generated by the strike.
Since the thickness of Mimas’ icy outer shell is presently estimated to be 19 miles (30 km) deep at most, this result indicates that the young moon has experienced a significant warming since the impact, which has led to a decrease in the thickness of the ice.
The team also noted that while their findings support the possibility of an ocean on Mimas, the moon could still be completely frozen at present and at the point of impact. In this scenario, the strange properties of Mimas’ orbit must result from the shape of the moon’s core.
“Mimas seemed like an unlikely candidate, with its icy surface dotted with craters that feature a giant impact crater that makes the young moon look a lot like the Death Star from Star Wars,” said Dr. Alyssa Roden of the Southwest Research Institute. One of the authors of the new study.
“If Mimas has an ocean, it represents a new class of ‘ghost’ small ocean worlds with surfaces that do not betray the presence of the ocean.”
The scientists note that future uncrewed missions to the Saturnian system will be valuable in unlocking the secrets of Mimas’ evolution, and that the Moon “may be the first example of a new pathway for the formation of potentially habitable ocean worlds.”
Image credit: NASA/JPL/SSI
Anthony is a freelance contributor covering science and video game news for IGN. He has more than eight years of experience covering breaking developments in multiple scientific fields and there is absolutely no time to fool you. Follow him on Twitter @BeardConGamer
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