Hidden ocean of Mimas is growing in size

Saturn’s moon Mimas may have a growing subsurface ocean. This is stated in an article published in the journal Geophysical Research Letters by researchers from the Southwest Research Institute (SwRI).

“Invisible” Ocean

The diameter of Mimas is 400 km, it occupies the twentieth place in the list of the largest moons of the planets. Until recently, this icy moon was mostly known for the distinctive 139-kilometer impact crater Herschel, giving it a visual resemblance to the Death Star from Star Wars.

Mimas. Source: NASA/JPL-Caltech/Space Science Institute

But in early 2022, SwRI scientists discovered signs that an ocean might be hiding under the surface of Mimas. This is indicated by the characteristic “rocking” of the moon, indicating that a layer of liquid water is hidden in its depths at a depth of 30 km.

At the same time, visually Mimas is completely different from the oceanic world. Unlike Europa, its surface is covered with many ancient craters and there are no faults and geysers on it, as on Enceladus. Therefore, scientists have suggested that Mimas is a new class of small “invisible” water worlds, which surface does not betray the existence of the ocean.

The growth of the Mimas Ocean

To test their conclusions, the researchers resorted to the help of computer simulations. They have confirmed that the body has a water layer. Moreover, it seems that the ocean is gradually increasing in size. This, in particular, is indicated by the Herschel crater. The simulation showed that at the moment of formation, the thickness of the Mimas ice shell had to be at least 55 km, otherwise it would simply have been destroyed at the moment of impact. 

Possible variants of the internal structure of Mimas. Source: NASA/JPL/SSI/SwRI

Scientists also considered the possibility that Mimas did not have an ocean at all during the collision, and it formed later. However, some details of Herschel’s structure indicated that there was still some kind of water layer in the interior of the moon. If the researchers’ conclusions are correct, this means that over the past billions of years, the Mimas ocean has increased in size, and its ice shell has thinned.

According to https://phys.org

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