(ORDO NEWS) — The solar system may turn out to be an even colder place than we thought. A new analysis of one of Saturn’s moons shows it could have a liquid ocean. New in this regard is Mimas, a small moon with a large crater that gives it a more than passing resemblance to the Death Star from Star Wars.
The small, peculiar moon wobble detected by astronomers could be the result of a liquid interior ocean, according to a new study.
If so, then Mimas would join other solar system moons such as Europa and Enceladus in the “IWOWs” (inland water ocean worlds) category. But if so, then it will be an IWOW of the kind we have never seen before, which will expand our understanding of what is possible.
“Because the surface of Mimas is heavily cratered, we thought it was just a frozen block of ice,” says geophysicist Alyssa Roden of the Southwestern Research Institute.
IWOWs like Enceladus and Europa usually have cracks and other signs of geological activity. “It turns out that the surface of Mimas was deceiving us, and our new understanding has greatly expanded the definition of a potentially habitable world in our solar system and beyond.”
Here on Earth, life mostly depends on sunlight, but there are a few places where organisms can thrive in complete darkness.
At the bottom of the ocean is one such place, clustered around hydrothermal vents that release heat and nutrients from the Earth’s interior. Here, life does not rely on photosynthesis, but on chemosynthesis, using chemical reactions to synthesize food.
This became relevant to the search for extraterrestrial life when Jupiter’s moon Europa and Saturn’s moon Enceladus were found to have liquid oceans beneath their icy crust.
Geological activity in the depths of the moons, caused by tidal stretching and attraction caused by gravitational interactions with their respective planets, generates enough heat to keep the water below the surface from freezing.
However, Mimas does not seem to belong to this group of moons. It is closer to Saturn and has a more eccentric (elliptical) orbit than Enceladus, which means it should experience stronger tides, but its activity is much lower than that of Enceladus.
This led the scientists to conclude that Mimas is likely in a solid frozen state and therefore less prone to deformation.
However, the problem of its libration, or the physical “fluctuation” detected by the Cassini probe, remains unresolved. If Mimas is solid, it shouldn’t wobble like that.
The moon’s libration suggests that it either has a differentiated core or a liquid ocean – something that prevents the core from being rigidly attached to the surface, allowing the latter to shift.
Roden and her team wanted to explore the possibility of a liquid ocean. They needed to solve the problem of generating and dissipating enough heat from the interior of the moon to keep the water inside the moon liquid while still maintaining a very thick, frozen outer shell.
“Most of the time when we create these models, we have to fine-tune them to get what we’re seeing,” Roden explains. “This time, the evidence for the existence of an inland ocean simply follows from the most realistic scenarios for the stability of the ice shell and the observed librations.”
According to their models, the Mimas ice sheet is 24 to 31 kilometers (15 to 20 miles) thick, with a global ocean churning underneath. Since Mimas is only 396 kilometers (246 mi) in diameter, this is a comparatively large thickness; the ice shell of Enceladus is from 5 to 35 kilometers with a diameter of 513 kilometers.
The team also found that heat flow from the surface of Mimas is likely very sensitive to ice thickness in any given region. Future probes should be able to measure this directly, both on Mimas and other IWOWs.
Finally, models suggest that, in addition to a liquid ocean, Mimas also has a differentiated core. This contradicts our previous models of the evolution of Mimas, since the moon’s early differentiation should have resulted in its orbit being very different from today’s. This makes Mimas potentially very interesting for further study and research.
“While our results confirm the presence of a modern ocean on Mimas, it is difficult to reconcile the moon’s orbital and geological characteristics with our current understanding of its thermo orbital evolution,” says Rodin.
“Assessing Mimas’ status as an oceanic moon will test patterns of its formation and evolution. This will help us better understand the rings of Saturn and medium-sized moons, as well as the abundance of potentially habitable oceanic moons, especially on Uranus. Mimas is an interesting target for further study.”
Contact us: [email protected]