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A strange little moon orbiting near Saturn has just revealed its biggest mystery: a hidden ocean beneath its cratered surface.
Mimas is less than 198 kilometers (123 miles) wide, too small to be perfectly round, and its icy shell is covered in deep scars caused by objects colliding with it. Its most prominent impact crater, Herschel, extends across a third of its face, earning it the nickname the Death Star in homage to the Empire’s gigantic space station in Star Wars. The moon is so modest that scientists believed it was the least likely place to look for a subsurface ocean, and yet an analysis of Mimas’s orbital motion revealed an ocean 12 to 18 miles (20 to 30 kilometers) beneath it. its icy layer.
The discovery is detailed in a study published on Wednesday in the magazine Nature. Using data from the Cassini space probe, which orbited Saturn from 2004 to 2017, the scientists behind the new study looked at subtle changes in Mimas’ orbit. Based on its motion and spin as it orbits Saturn, the data suggests that Mimas hosts a recently formed ocean that is still evolving.
The ocean is estimated to be between 5 and 15 million years old. By comparison, the internal ocean of Saturn’s moon Enceladus formed about a billion years ago, while Jupiter’s moon Europa has hosted an ocean for nearly 4 billion years.
Related article: A guide to the supernatural oceans of our solar system
Mimas now joins Enceladus and Europa, as well as Saturn’s moon Titan and Jupiter’s Ganymede, on the list of icy ocean worlds in the solar system, but there could be more out there. Moons that are made primarily of ice are heated by tides, which melt the ice internally while the outer layer freezes to form a covering crust. This elite list of moons constitutes the leading candidates for life in the solar system, with liquid water being a prerequisite for life on Earth.
“The existence of a newly formed liquid water ocean makes Mimas an ideal candidate for study by researchers investigating the origin of life,” said Nick Cooper, co-author of the study and researcher at the Faculty’s Astronomy Unit. of Physical and Chemical Sciences at Queen Mary University of London, said in a statement.
According to the study’s simulations, the Mimas ocean reached its current depth recently, that is, less than 2 or 3 million years ago. That time span could mean that life may not have had a chance to form yet, offering a rare early glimpse into habitable conditions in the solar system.
Mars may be a hotspot for the search for habitability outside of Earth, as it most closely resembles our home planet, but the solar system’s icy moons are really the place to be when it comes to exploring extraterrestrial life. . Luckily, the JUICE mission is on its way to study Jupiter’s icy moons, looking for signs of habitability. Since Cassini plunged to its death in Saturn’s atmosphere, there are plans in the works to send another spacecraft to the ringed planet and its moons, namely Enceladus, but we’ll have to wait a little longer for them to get the green light.
In the meantime, we can ponder what kind of life may exist on Saturn’s disfigured moon.
Further: Saturn’s moon Enceladus is yielding a key ingredient for life