Astronomers studying Mimas, one of Saturn's smaller moons, say it's likely hiding a giant ocean beneath its crust.
Using data gathered from the Cassini probe, which studied Saturn and its moons for more than ten years, researchers in France concluded that Mimas probably has a liquid ocean somewhere between 12 and 18 miles down beneath the crust, instead of a rocky core.
Mimas, which is known for an enormous impact crater, is about 250 miles wide. Earth's moon is almost ten times larger.
An underground ocean would make up about half of Mimas' volume, but it would only be equivalent to 1.2% to 1.4% of the liquid water oceans present on Earth.
The ocean is thought to have an overall temperature right around the freezing point of water.
The ocean is thought to be between 5 million and 15 million years old. That's young, geologically speaking, and could explain why Mimas' external crust doesn't show any geysers like those we see caused by the underground ocean on Saturn's moon Enceladus.
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Astronomers believe the presence of such an ocean makes Mimas an excellent place to study the conditions that may give rise to life in the solar system.
"Mimas was probably the most unlikely place to look for a global ocean — and liquid water more generally," co-author Valery Lainey of the Paris Observatory wrote in an email to The Associated Press. "So that looks like a potential habitable world. But nobody knows how much time is needed for life to arise."
