Astronomers have uncovered increasing evidence that one of Saturn’s smallest moons, named Mimas, has a global ocean beneath its icy surface. This is a significant revelation in the overall search for water on other planets, as water is an essential building block for all life, further fueling the potential for discovering habitable worlds in deep space.
Scientists used to think Mimas was just a big ice chunk before NASA went on their Cassini mission orbiting Saturn, and its 146 moons, from 2004 to 2017.
Mimas was first discovered in 1789 by English astronomer William Herschel, and was first photographed in 1980 using the Voyager probes. Mimas is covered in craters, with the largest one being 80 miles across.
Through the Cassini mission, astronomers found that the moon takes around 22 hours to orbit Saturn, and is about 115,000 miles from Saturn. Data also showed that Mimas’ rotation and orbital motion is triggered by the moon’s interior.
According to reports, in 2014 European researchers determined that the core of Mimas is either rigid, elongated, rocky, or has a subsurface ocean causing its rotation and motion. Observatoire de Paris astronomer Dr. Valéry Lainey and his colleagues analyzed the orbital motion data to get a clearer conclusion, and their findings were published Wednesday in the journal Nature.
Through this study, the team was able to determine that the moon’s spin and orbital motion didn’t match up with the theory that Mimas had a rocky core, and instead, the evolution of its orbit suggests an internal ocean that shaped its motion, Lainey explained.
“This discovery adds Mimas to an exclusive club of moons with internal oceans, including Enceladus and Europa, but with a unique difference: its ocean is remarkably young, estimated to be only 5 (million) to 15 million years old,” said study co author Dr. Nick Cooper.
The team was able to determine the origin and age of Mimas’ ocean by analyzing how the moon responded to Saturn’s gravitational forces.
“Internal heating must come from the tides raised by Saturn on Mimas. These tidal effects have induced friction inside the satellite, providing heat,” Lainey said.
The study stated that they suspect the ocean is around 12 to 19 miles below the moon’s ice exterior. Astronomically speaking the ocean is very young, which means there wouldn’t be any outward signs of activity on the surface.
This discovery is a huge moment for science in general, as it could shift the ways in which astronomers think about moons in our solar system.
“If Mimas hides a global ocean, this means that liquid water could lie almost anywhere. We already have serious candidates for global oceans (on moons such as) Callisto, Dione and Triton,” Lainey said.
“The existence of a recently formed liquid water ocean makes Mimas a prime candidate for study, for researchers investigating the origin of life,” Cooper said.
“It may be time to observe other seemingly quiet moons across the solar system that could be hiding conditions that can support life,” the study authors said.
“Lainey and colleagues’ findings will motivate a thorough examination of mid-sized icy moons throughout the Solar System,” wrote Drs. Matija Ćuk and Alyssa Rose Rhoden in an article that accompanied the study.
Rhoden has also written research about a “stealth” ocean on Mimas.
“Basically, the difference between our 2022 paper and this new paper is that we found an ocean could not be ruled out by Mimas’ geology, whereas they are actually detecting the signature of the ocean within Mimas’ orbit. It is the strongest evidence we have, so far, that Mimas really does have an ocean today,” Rhoden said.
“Mimas certainly demonstrates that moons with old surfaces can be hiding young oceans, which is pretty exciting. I do think we can speculate as to moons having developed oceans much more recently than we often assume,” Rhoden said.
Eric Mastrota is a Contributing Editor at The National Digest based in New York. A graduate of SUNY New Paltz, he reports on world news, culture, and lifestyle. You can reach him at firstname.lastname@example.org.