Saturn has some famous moons, like Enceladus (a plume-spewing moon of mystery) and Titan (the intriguing target of NASA’s future Dragonfly mission). But what about dainty Mimas, a moon that’s mostly known for its resemblance to the Star Wars Death Star?
Turns out it might be hiding an ocean.
A study published in the journal Icarus lays out evidence that suggests Mimas has liquid deep under its icy surface. “If Mimas has an ocean, it represents a new class of small, ‘stealth’ ocean worlds with surfaces that do not betray the ocean’s existence,” said lead author Alyssa Rhoden in a Southwest Research Institute (SwRI) statement on Wednesday. Mimas might look quiet, but NASA’s now-defunct Saturn-studying Cassini spacecraft “identified a curious libration, or oscillation, in the moon’s rotation, which often points to a geologically active body able to support an internal ocean,” SwRI said.
The libration spotted by Cassini suggests Mimas’s interior is warm enough for a liquid ocean, but not so warm it compromises the moon’s thick shell of ice.
The researchers calculate that ice shell could be up to 19 miles (31 kilometers) thick. There’s a nifty acronym for interior water ocean worlds: IWOWs. Known IWOWs include Enceladus, Titan and Jupiter’s fascinating moon Europa. These places are particularly interesting because they may be habitable for microbial life.
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