Could the Death Star Moon Have an Ocean?

NASA/Jet Propulsion Laboratory

People know the Saturnian moon Mimas for one thing: The enormous crater that makes it look like the Death Star. In every other regard, Mimas appears to be a cold, dead, icy rock with pretty much nothing going on. The surface has been dead for billions of years. It's a far cry from moons like Europa or its neighbor Enceladus, both of which sport young, smooth surfaces courtesy of subsurface oceans. We've even seen the cryovolcanism on Enceladus. 

However, there is evidence that Mimas also harbors a subsurface ocean, despite all appearances to the contrary. It all comes back to that massive crater, Herschel. If Mimas had a completely icy shell around its core, an impact of that size would have completely shattered the crust. Obviously, that's not the case. However, the physics do work out if Mimas had a subsurface ocean when the impact occurred. Not only that, but the icy shell around the ocean may be thinning, shrinking from 34 miles thick during the Herschel impact to 19 miles today.

If we are able to confirm a subsurface ocean on Mimas, that would excellent news for the prospects of finding life in our solar system. Beyond the obvious of "hey, here's one more place we could look," there are a lot of moons like Mimas floating around, especially around Neptune. If Mimas has an ocean, there's no reason not to believe other moons like it wouldn't have them as well. There could be a dozen moons with secret oceans in the solar system, which is just that many more places we could find life. Let's just hope that, if Mimas does have life floating around, they don't convert the moon into a fully operational battle station.