Titan, Saturn’s largest moon, might not have an ocean after all

In the late 2000s, scientists studying data from NASA’s Cassini spacecraft concluded that Saturn’s moon Titan had a deep liquid ocean hidden beneath a thick shell of ice. That ocean was thought to be hundreds of kilometers deep and potentially capable of supporting early chemical processes related to life.

However, new research presented at a recent scientific meeting and published in Nature challenges this idea. The new study suggests that Titan is mostly frozen today and does not have a global underground ocean. Instead, it may contain smaller pockets of melted water scattered within its icy interior.

The original ocean idea came from measurements of Titan’s gravity and shape, which showed that Saturn’s pull causes strong tidal stretching, similar to but much larger than Earth’s tides. Scientists assumed this flexibility required a liquid ocean. But the new analysis shows that Titan gives off much more heat than expected if a large ocean were present.

Using updated models and Cassini data, researchers found that Titan’s behavior is better explained by a thick ice layer over a rocky core, with no global ocean. They propose that Titan’s ocean may have frozen tens to hundreds of millions of years ago, leaving behind melted regions within the ice. Some scientists remain skeptical, and future missions like NASA’s Dragonfly, scheduled to arrive in 2034, may help resolve the debate.

Source: Petricca, F., Vance, S.D., Parisi, M. et al. Titan’s strong tidal dissipation precludes a subsurface ocean. Nature 648, 556–561 (2025)