Mimas, Saturn’s mysterious-looking moon is quite deceitful.
A crater measuring 80 miles across dominates the small moon, giving it the appearance of Star Wars Death Star — which is a space station with a planet-destroying weapon. Mimas is a chunk of ice.
Other moons, such as Saturn’s Enceladus or Jupiter’s Europa have cracked surfaces. These telltale plumes, which shoot from the ground and are strong evidence of sub-surface oceans, also exist. Mimas doesn’t show any signs of an ocean.
Alyssa Rhoden (a planetary scientist who studies ocean worlds) said that Enceladus, Europa, and Enceladus clearly show an engine. It’s impossible for Mimas to be an ocean world if you look at it.
Or so Rhoden believed. The appearances can be deceiving.
Rhoden, her coauthor, and a new article in the planetary science journal Icarus describe how they discovered evidence of an ocean under Mimas’ icy shell. It may not be an ice chunk frozen on the moon after all.
Mimas has an attribute that may allow it to have an ocean. It orbits Saturn in a highly eccentric orbit, which means it is pulled and stretched by the planet’s powerful gravitational force. Then it orbits further away. Each orbit takes only 22 hours and 36 seconds. This process is called “tidal warming” and it creates enormous amounts of heat on ocean worlds such as Europa.
This reality was in mind when Rhoden, a principal scientist at Southwest Research Institute and a science organization, continued to investigate an earlier observation that showed a small wobble in Mimas orbit around Saturn. This wobble could be caused by an icy sea that is sloshing within Mimas. Could tidal heating possibly have created a sea by melting enough ice in Mimas? If this is true, then there wouldn’t have been too much heat (that would melt the icy shell) or too little heat (then it would freeze).
Researchers calculated that if Mimas had an ocean large enough to cause its wobble, then the water would be found beneath an icy shell between 14 and 20 miles thick. Computer simulations were used to simulate how heating from tidal heating would affect the ice at Mimas. It showed an ocean of ice under 14 to 20 miles.
Rhoden stated, “We came up exactly with the right number.”
Rhoden insists that this is not nearly enough evidence to prove that Mimas harbors an ocean. With the available information, there is now strong evidence that there could be an ocean there.