Mimas, the smallest moon in Saturn’s innermost group, bears resemblance to what is depicted in the “Star Wars” film. This moon has revealed the first clue that it could be a “hidden ocean world” after NASA’s Cassini spacecraft detected a peculiar wobble in its rotation.
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The camera onboard the Cassini spacecraft captured this image of Saturn’s moon Mimas on October 16, 2010, revealing the prominent Herschel Crater.
A study published on January 19, 2022, in the journal Icarus reveals that the observed oscillations may be the result of a trapped subsurface liquid ocean beneath the moon’s icy surface, with a diameter of 396 kilometers.
If true, researchers suggest that Mimas represents an entirely new type of world. The discovery of the moon’s secret ocean could imply the possibility of water and potentially sustainable life more abundant in our solar system than initially thought.
“If Mimas has an ocean, it represents a small, ‘hidden’ ocean world with a surface that doesn’t betray the existence of the ocean,” said Alyssa Rhoden, the lead author of the study and a planetary scientist at the Southwest Research Institute in San Antonio, Texas.
Internal water ocean worlds (IWOWs), such as Saturn’s moon Enceladus or Jupiter’s moon Europa, are not new concepts to scientists. However, the internal tidal processes tend to disrupt their surfaces, exhibiting other signs of geological activity. In contrast, Mimas, at first glance, appears to be merely a solid block of ice, Rhoden noted.
“Turns out, Mimas has been deceiving us, and our understanding has greatly expanded about a potentially habitable world within our solar system and beyond,” she added.
To investigate the possibility of an ocean hidden beneath Mimas’ frozen surface, researchers constructed a model to examine whether its gravitational interactions with Saturn could generate the necessary tidal forces to keep the moon’s interior warm, maintaining the water below at depths of 15 to 20 kilometers—an outer icy shell (24 to 31 kilometers thick) warm enough to remain in a liquid state.
By studying the potential support for an ocean on this moon, scientists can gain further insights into other potentially hidden ocean moons within our solar system, such as the moons of Uranus.