Saturn's Moon Mimas: Signs of a Big, New Ocean Under the Ice Cover.

Astronomers have discovered strong evidence of a hidden ocean beneath the icy surface of Saturn's small moon, Mimas, which resembles the Death Star from 'Star Wars'. They found this by studying Mimas’ orbit and rotation, and concluded that an ocean 20 to 30 kilometers deep under the ice is more likely than a rocky core.

Mimas is small, only 400 kilometers in diameter, and doesn't show typical signs of having an ocean beneath its surface like cracks or geysers. "Mimas was probably the most unlikely place to look for a global ocean — and liquid water more generally," said co-author Valery Lainey, highlighting the surprise of this discovery.

The ocean inside Mimas could occupy half of its volume, but it's only a tiny fraction of the volume of Earth's oceans. Nonetheless, Mimas has a giant impact crater, making it look like the Death Star, and has attracted attention for its potential to harbor life.

Experts not involved in the study praised the discovery, suggesting that finding young oceans on small, icy moons like Mimas could shape our understanding of habitable worlds. The ocean is relatively young, estimated to be between 5 million and 15 million years old, and could have warmer waters at the sea floor.

The discovery of a young ocean on Mimas makes it an interesting subject for studying the origins of life. Mimas was discovered in 1789 and is named after a giant from Greek mythology, adding to its intrigue.