Saturn’s small moon, Mimas, has an unpredictable ocean beneath a layer of ice

While searching for places that could potentially harbor life in our solar system, astronomers are increasingly interested in several moons of large gas giant planets. Saturn’s moon Enceladus and Jupiter’s moon Europa, for example, are both prime targets for habitability research because despite their distance from the sun, they are thought to host oceans of liquid water beneath thick layers of icy crust. Now, a new moon may be included in this ranking, as researchers have found evidence of an ocean beneath the icy layers of Saturn’s small moon, Mimas.

This finding is surprising because Mimas is much smaller and younger than other icy moons known to have subsurface oceans. “Mimas is a small moon, only about 400 kilometers in diameter, and its heavily cratered surface does not suggest a hidden ocean beneath it,” said one of the researchers, Nick Cooper from Queen Mary University of London, in a statement. statement. “This discovery adds Mimas to the exclusive group of moons that have internal oceans, including Enceladus and Europa, but with a unique difference: its oceans are very young, estimated to be only 5 (million) to 15 million years old.”

Illustration of Mimas orbiting Saturn. Frédéric Durillon, Studio Animea | Observatory de Paris – PSL, IMCCE

Evidence for the existence of the Mimas ocean comes from the way it orbits and rotates, according to data from NASA’s Cassini mission. The moon’s movement is influenced by its interior, and researchers observed its rocking motion, called libration, caused by Saturn’s gravity. The way it moves may be caused by a rock core or an internal ocean and, previously, scientists were unsure which explanation was correct.

But new research suggests that the best explanation for the moon’s movement is the existence of an ocean beneath 10 miles to 20 miles of ice, and that this ocean appeared relatively recently.

“The presence of a newly formed ocean of liquid water makes Mimas a prime candidate for study, for researchers investigating the origins of life,” Cooper said. This also means that even moons that appear inactive from the surface can harbor oceans, expanding the number of potentially habitable places.

“The idea that relatively small icy moons could harbor young oceans is inspiring, as is the possibility that transformation processes have occurred even in the recent history of these moons,” astronomers Matija Ćuk and Alyssa Rose Rhoden wrote in a study. accompanying article. “Mimas also has an important lesson to teach scientists: intuition is good for generating hypotheses, but not enough for drawing conclusions. The Solar System will always have surprises, and researchers must be open enough to new ideas and unexpected possibilities to recognize them.”

This research was published in the journal Natural.

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