Researchers suggest a global ocean lies 15 miles beneath the surface of Saturn’s “Death Star” moon, Mimas—a shocking discovery that could redefine what a habitable world looks like
Saturn’s smallest moon, called Mimas, may have a hidden ocean buried deep beneath its frozen surface, according to new research published Wednesday in the journal Nature. Though moons with global oceans have been sighted in the solar system before, the idea that water could be lurking under Mimas’ crust was unexpected.
“It’s quite a surprise,” says Valery Lainey, an astronomer at the Paris Observatory and lead author of the study, to the Guardian’s Ian Sample. “If you look at the surface of Mimas, there’s nothing that betrays a subsurface ocean. It’s the most unlikely candidate by far.”
Nicknamed the “Death Star moon” due to its massive surface crater that makes it resemble the Star Wars space station, Mimas has a thick, icy crust and a dilapidated, crater-ridden surface. One of at least 146 moons orbiting Saturn, Mimas is notable for its unusual motion: The planet-facing side of the moon rocks back and forth during orbit. This movement, called libration, led astronomers to two possible explanations: Mimas either has a frozen, oblong core, or it is harboring a subsurface ocean.