A thorough reanalysis of data collected more than a decade ago indicates that Titan, Saturn’s largest moon, does not possess a vast ocean beneath its icy surface, as was previously suggested.
Instead, beneath its icy exterior, there are layers of ice, muddy tunnels, and pockets of meltwater near the rocky core, all according to a study led by NASA and the University of Washington.
The study and its protagonists
The research, published in Nature, was led by NASA with the collaboration of Baptiste Journaux, assistant professor of Earth and space sciences at the University of Washington, and Ula Jones, a graduate student from his lab.
Journaux is part of the team for NASA’s upcoming Dragonfly mission to Titan, scheduled for launch in 2028. The data obtained in this study will be key to guiding the mission, which seeks to definitively answer whether there is liquid water inside the moon and eventually find evidence of extraterrestrial life.
Cassini and the initial ocean hypothesis
Data from the Cassini mission, which orbited Saturn between 1997 and 2017, led researchers to suspect the existence of a large underground ocean on Titan. The deformation observed on the moon during its elliptical orbit around Saturn seemed compatible with a deep ocean that allowed the crust to flex under the planet’s gravitational pull.
However, when modeling the moon with a global ocean, the results did not match the physical properties described by the data. A more detailed analysis revealed a different and more complex scenario.
Synchronization and viscosity: the key to the finding
The new study introduced an additional level of analysis: the synchronization of Titan’s shape change. Researchers observed that the moon’s deformation occurred about 15 hours after Saturn’s peak gravitational pull.
This delay, similar to the effort of moving honey instead of water, indicated that Titan’s interior is much more viscous than expected. The amount of energy dissipated was much greater than predicted in the global ocean scenario.
“No one expected such strong energy dissipation inside Titan. That was the irrefutable proof that the interior is different from what was inferred from previous analyses,” explained Flavio Petricca, postdoctoral researcher at NASA’s Jet Propulsion Laboratory and lead author of the study.
An interior of slush and water pockets
The proposed model presents an interior composed mainly of thick slush, with less liquid water than expected. This mixture explains the observed delay in deformation but still contains enough water to allow Titan to transform under gravitational attraction.
Petricca reached this conclusion by measuring the frequency of radio waves from Cassini during Titan flybys, while Journaux provided data on thermodynamics of water and minerals under extreme pressure, simulated in his planetary cryomineral physics lab at the University of Washington.
Implications for the search for life
Although the idea of a global ocean fueled the search for life on Titan, the new findings could increase the chances of finding simple organisms. Analyses suggest that freshwater pockets inside could reach temperatures of up to 20 °C, with nutrients concentrated in small volumes, facilitating microorganism growth.
“Instead of an open ocean like Earth’s, we are probably seeing something more akin to sea ice or Arctic aquifers,” explained Journaux.
While it is unlikely to find fish swimming in muddy channels, life on Titan could resemble Earth’s polar ecosystems, adapted to extreme conditions.
The reanalysis of Cassini data redefines our understanding of Titan: there would not be a global ocean beneath its surface, but a complex interior of ice, slush, and water pockets. This finding does not rule out the possibility of life but opens new perspectives on how it could develop in extreme environments.
The Dragonfly mission, scheduled for 2028, will be key to confirming these hypotheses and bringing us closer to a definitive answer about one of the most fascinating worlds in the solar system.
