CAPE CANAVERAL, Fla. (AP) — Astronomers have found the best evidence yet of a vast, young ocean beneath the icy exterior of Saturn’s Death Star lookalike mini moon.

The French-led team analyzed changes in Mimas’ orbit and rotation and reported Wednesday that a hidden ocean 12 to 18 miles (20 to 30 kilometers) beneath the frozen crust was more likely than an elongated rocky core. The scientists based their findings on observations by NASA’s Cassini spacecraft, which observed Saturn and its more than 140 moons for more than a decade before diving through the ringed planet’s atmosphere in 2017 and burning up.

Barely 250 miles (400 kilometers) in diameter, the heavily cratered moon lacks the fractures and geysers — typical signs of subsurface activity — of Saturn’s Enceladus and Jupiter’s Europa.

“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 said in an email. “So that looks like a potential habitable world. But nobody knows how much time is needed for life to arise.”