ISTANBUL

Saturn’s small, cratered moon, Mimas, may secretly harbor a young subsurface ocean -- a finding that could reshape how scientists define ocean worlds in the solar system, new research suggested.

“When we look at Mimas, we don’t see any of the things that we’re accustomed to seeing in an ocean world,” Alyssa Rhoden, a planetary scientist at the Southwest Research Institute (SwRI) in the US state of Colorado, said at the Europlanet Science Congress-Division for Planetary Sciences meeting last month, according to Space.com.

Despite its unbroken, heavily cratered surface, new thermal and orbital models indicate liquid water may lie beneath 12 - 19 miles (20 - 30 kilometers) of ice.

Data from NASA’s Cassini spacecraft first hinted at the possibility of an internal ocean, but recent modeling strengthens the case.

Rhoden’s team found that changes in Mimas’ orbit likely generated internal heat through gravitational “tides,” melting portions of the icy shell within the past 10 to 15 million years -- a blink in geological time.

“It would be hard, but may be doable,” Rhoden said of detecting the hidden sea with a future orbiter.

Meanwhile, Rhoden’s SwRI colleague Adeene Denton analyzed Herschel Crater, Mimas’ most striking feature, to further constrain the moon’s history.

“Mimas needs to be right on the tipping point,” Denton told Space.com. Her findings, published in Earth and Planetary Science Letters, suggest the crater formed as the subsurface began melting -- when the ice was soft but not yet liquid.

Together, the studies paint an unexpected picture of the tiny moon once dismissed as frozen solid. As Denton put it, “All of these things are now building a coherent narrative about Mimas as a young ocean world.”