Saturn’s moon Mimas is covered in 20 mile thick ice, but astronomers now believe there is a ‘stealth ocean’ buried deep beneath its thick frozen surface.
Mimas, the closest of Saturn’s ‘large’ moons, has a diameter of 246 miles, and is the smallest astronomical body known to still be round in shape due to self-gravitation.
There are no hints of any liquid water, when looking at the moon in images and from observations, according to experts, but simulations by the Southwest Research Institute in Colorado, suggest there is one, deep underneath the blanket of ice.
Measurements taken by the NASA Cassini spacecraft in 2014 hinted there might be some water under the surface, but this hasn’t been corroborated until now.
In the new study, the team explored the size and formation predictions for the small moon, to determine that its internal heat would be enough to allow for flowing water.
Saturn’s moon Mimas is covered in 20 mile thick ice, but astronomers now believe there is an ‘stealth ocean’ buried deep beneath its thick frozen cover
Also known as Saturn I, due to it being the closest to the ringed world, Mimas has a total surface area slightly less than the land area of Spain.
That surface bears none of the fracturing, or evidence of melting that astronomers and planetary scientists would expect to see from a world with a hidden ocean.
‘When we look at a body like Mimas, it is a little, cold, dead rock,’ Alyssa Rhoden, lead author of this new study told New Scientist.
‘If you put Mimas in a gallery with a bunch of other icy moons, you would never look at it and say “oh, that one has an ocean”.’
As well as it baring no signs of having an ocean, none of the accepted theoretical models of moon formation suggest it should have an ocean.
However, observations from 2014, taken by Cassini, show the moon wobbling as it spins, suggesting something strange going on under the ice.
At the time researchers suggesting there was water under the icy shell, and so, since then astronomers have been attempting to see whether that is the case, and how it is possible.
Rhoden told New Scientist that researchers set out to prove that Mimas can’t have an ocean — because it seemed so unlikely.
The problem is, the scientist explained, that they did find evidence of an ocean, and findings backed up earlier observations from Cassini.
They performed simulations of how the interior is stretched and heated by Saturn’s gravity, and what that would do the an icy outer shell.
The heating was enough to support a global ocean of liquid water, as much as 18 miles below a thick crust of ice, deep enough not to crack the surface.
Cassini measurements of Mimas’ physical properties are either explained through a non-hydrostatic core, or a global liquid ocean as much as 20 miles below the ice.
A combination of tidal heating, caused by the pull of Saturn, played a bearing on the inner-world ocean developing, as well as its eccentricity and libration.
There are no hints of any liquid water, when looking at the moon in images and from observations, according to experts, but simulations by the Southwest Research Institute in Colorado, suggest there is one, deep underneath the blanket of ice
Measurements taken by the NASA Cassini spacecraft in 2015 hinted there might be some water under the surface, but this hasn’t been confirmed until now
‘An ocean within Mimas would be surprising, given the lack of comparable geologic activity to that observed on other ocean-bearing moons like Europa and Enceladus, and thus has important implications for the prevalence and identification of ocean worlds,’ the researchers wrote in a paper published in the journal Icarus.
‘We find that, using the most reasonable assumptions, Mimas would have the suggested ocean and ice shell thicknesses today.’
This would put it under the category of ‘stealth world’s’ — that is icy moons with an unexpected ocean buried beneath its surface.
‘There 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,’ Rhoden said.
‘The more we understand the pathways by which we can form an ocean, the more we’re going to learn about the habitats that are available in our solar system.’