Saturn鈥檚 moon Mimas may have an unexpected ocean. This small satellite doesn鈥檛 look like any of the other ocean worlds that we have seen before, but measurements from NASA鈥檚 Cassini spacecraft hinted that it might have water underneath its icy surface, and calculations of its internal heat have now confirmed that this is possible.
Unlike most of the other moons that planetary scientists believe to carry oceans, Mimas shows no fracturing or evidence of melting on its surface. 鈥淲hen we look at a body like Mimas, it is a little, cold, dead rock,鈥� says at the Southwest Research Institute in Colorado. 鈥淚f you put Mimas in a gallery with a bunch of other icy moons, you would never look at it and say 鈥榦h, that one has an ocean鈥�.鈥�
What鈥檚 more, none of the accepted theoretical models of moon formation predict that Mimas could have an ocean today.
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But observations in 2014 of Mimas wobbling as it spun indicated that something is strange about its interior, and some researchers suspected that it could be water sloshing under an icy shell.
鈥淚 took one look at this as a person who studies ocean worlds and said: 鈥楾here ain鈥檛 no way 鈥� no way!鈥� So I set out to prove that Mimas can鈥檛 have an ocean,鈥� says Rhoden. 鈥淭he problem is, that鈥檚 not what we found.鈥�
She and her colleagues have now performed detailed simulations of how Mimas鈥檚 interior is stretched and heated by Saturn鈥檚 gravity and what that heating would do to an icy shell. They found that this heating could be enough to support a global liquid ocean buried beneath 24 to 29 kilometres of ice.
If Mimas has an ocean, there could be many of what the researchers call 鈥渟tealth鈥� ocean worlds. 鈥淭here are a lot of icy satellites in our solar system, and if Mimas could be an ocean world, any of them could be ocean worlds,鈥� says Rhoden. 鈥淭he more we understand the pathways by which we can form an ocean 鈥� or not 鈥� the more we鈥檙e going to learn about the habitats that are available in our solar system.鈥�
Icarus
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