Data from NASA’s Cassini mission to Saturn initially suggested that Titan could possess a vast subterranean ocean of liquid water. However, when University of Washington scientist Baptiste Journeau and his team created models of a moon with an ocean, the findings did not align with the physical characteristics indicated by the data. What we likely observe instead resembles Arctic sea ice and aquifers, rather than an expansive ocean akin to those on Earth.
This composite image presents an infrared view of Titan. In this depiction, blue signifies wavelengths centered at 1.3 microns, green at 2.0 microns, and red at 5.0 microns. While visible wavelengths only reveal Titan’s hazy atmosphere, the near-infrared wavelengths enable Cassini’s vision to penetrate the haze, showcasing the moon’s surface. This perspective primarily focuses on the terrain in Titan’s hemisphere facing Saturn. Image credit: NASA / JPL-Caltech / Space Science Institute.
The Cassini mission, which commenced in 1997 and spanned nearly 20 years, yielded extensive data about Saturn and its 274 moons.
Titan is the only celestial body outside Earth known to feature liquid on its surface.
Temperatures on Titan hover around -183 degrees Celsius (-297 degrees Fahrenheit). Rather than water, liquid methane forms lakes and precipitates as rain.
As Titan orbits Saturn in an elliptical pattern, scientists noted the moon stretching or contracting based on its position relative to Saturn.
In 2008, they hypothesized that Titan must harbor a massive ocean beneath its crust to explain such notable deformation.
“The extent of deformation is influenced by Titan’s internal structure,” Journeau explains.
“When Saturn’s gravity acts on a deep ocean, it can bend the crust even more; however, if Titan is entirely frozen, the deformation would be less pronounced.”
“The deformations detected during the initial analysis of Cassini mission data might align with a global ocean scenario, but we now understand that there is more complexity involved.”
Schematic representation of Titan’s internal structure as revealed by Petricca et al.. Image credit: Petricca et al., doi: 10.1038/s41586-025-09818-x.
In this new study, Dr. Journeau and his co-authors introduce an additional layer of detail: timing.
Titan’s shape alteration lags Saturn’s peak gravitational influence by approximately 15 hours.
Similar to stirring honey with a spoon, manipulating a thick and viscous substance demands more energy compared to liquid water.
By measuring this delay, scientists were able to ascertain how much energy was required to alter Titan’s shape, facilitating inferences about its internal viscosity.
The energy loss, or dissipation, observed on Titan greatly exceeded what researchers anticipated in a global ocean framework.
“No one expected such significant energy dissipation to take place within Titan,” stated Dr. Flavio Petricca, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory.
“This provided definitive evidence that Titan’s interior differs from our previous analyses.”
Consequently, the scientists proposed a model characterized by a greater presence of slush and significantly reduced quantities of liquid water.
This slush is sufficiently thick to explain the delay, yet still contains water, enabling Titan to deform under gravitational forces.
“Titan’s water layer is so dense and the pressure so great that it alters the physics of the water,” Journeau remarks.
“Water and ice behave differently compared to seawater on Earth.”
This study is published in today’s issue of Nature.
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F. Petricca et al. 2025. The dissipation of Titan’s powerful tidal forces prevents the formation of underground oceans. Nature 648, 556-561; doi: 10.1038/s41586-025-09818-x
Source: www.sci.news
