Saturn, the beautiful ringed planet, has over sixty moons. The most interesting are Titan and Enceladus. NASA is sending its Dragonfly mission to take a look at the surprisingly Earth-like giant moon Titan, which has liquid hydrocarbon lakes. Meanwhile, scientists recently revealed that they think there could be a whale’s worth of biomatter in a warm saltwater ocean under the icy crust of Enceladus. NASA might send Orbilander in the late 2030s to take a closer look.
Planetary scientists don’t care about Mimas, Saturn’s smallest moon. Sure, its massive Herschel crater might make it look like the “Death Star” space station from Star Wars, but it’s long been presumed to be a dead, lifeless world.
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It turns out that what makes it look a bit like an armed space station is also evidence that it may be an ocean world capable of supporting life.
Scientists at the Southwest Research Institute in San Antonio, Texas have unveiled evidence that Mimas could generate the right amount of heat to support a liquid ocean under its surface.
Published in the Geophysical Research Letters journal this week, the new research came about from an examination of the moon’s Herschel crater. Simulations showed that the structure of the impact basin and the lack of tectonics are compatible with a thinning ice shell and a geologically young ocean.
The first evidence for an ocean below the cratered surface of Mimas came close to the end of NASA’s flagship Cassini mission to Saturn, which ceased in 2017. It found an oscillation in Mimas’ rotation that suggests a geologically active body able to support an internal ocean. “Mimas seemed like an unlikely candidate, with its icy, heavily cratered surface marked by one giant impact crater,” said second author Dr. Alyssa Rhoden, a specialist in the geophysics of icy satellites, at SwRI. “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.”
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The paper suggest that since the then-frozen Mimas was struck by whatever caused its Herschel crater it’s been warming and expanding.
If Mimas is an ocean world, it doesn’t look like one, so this changes how planetary scientists should think about Saturn’s many mid-sized moons. It also means, say the authors, that potentially habitable ocean moons may exist at Uranus—where NASA may soon send a mission.