Could the world of our solar system arguably be home to one of the most fascinating discoveries, which could be hiding less water than previously believed? The answer to this question could lie in one of the most drastic re-assessments of past NASA data, which has challenged a long-held assumption about the Earth’s second-largest moon, Titan. For many years, it was assumed that with Titan and its massive tides affecting its parent body, Saturn, that the only thing enabling this high level of tides would be a massive amount of water beneath Titan’s surface.
Titan, which is even larger than the planet Mercury and is the only moon that has a dense atmosphere, was years ago of interest to planetary scientists owing to its Earth-like features in the form of rivers, lakes, and rainfall in its -179 degree environment composed of methane. The preliminary findings on the Cassini mission revealed that the icy surface of Titan was strongly influenced by the gravitational pull of Saturn during its orbit around it, which indicated that this moon also had oceans of water in it. However, a new study by Flavio Petricca of the Jet Propulsion Laboratory of NASA yielded a contrary conclusion.
The research team analyzed the Doppler shifts in both the X and Ka bands coming from the Cassini satellite, using the development of the phase compression algorithms based on the data developed during the Juno and InSight missions. The signal generated by the tide was filtered by the removal of the effects of mass redistribution caused by Titan’s atmosphere, and the pattern generated was a unique one: Titan is much less responsive to the pull of the gravitational force of Saturn than a world with a liquid interior would be. The Love number and the delay of 15 hours between the force of the Moon and the tide caused by it indicate an ice shell.
This slush mixture or ice close to freezing may have pockets of water, up to as much as 20°C. Simulations of the extreme pressure found on Titan in experiments conducted in Baptiste Journaux’s Cryo-Mineral Physics Lab for Planets confirmed predictions in the slush model regarding the existence of the disparity in water/ice properties at high presser.
However, it also alters our existing knowledge regarding the heating patterns of Titan. This tidal heating, caused by the rather eccentric orbits of the moon, which are a result of the effect of the gravitational forces of the Saturnian system, produces a mechanism of friction; however, the results of the simulation regarding the conduction of heat flow indicate the possibility of a loss of up to 10 terawatts of heat in the convection currents of the ice shell of Titan in a manner that does not produce a global ocean surrounding it. This led to the postulate that maybe due to the lack of radiative heating, its liquid water environment might very well be frozen up, and the melting process might still be possible in a local environment.
This process also fits into the models of evolution regarding the icy moons. However, the challenge was the accurate determination of the imaginary part of the tidal Love number, Im(k₂). This corresponds to the rate at which dissipation occurs. The rate at which dissipation occurs in Titan not only impacts the determination of the internal structure of Titan, but it also impacts the orbit. This dissipation works against the influence exerted by the dissipation occurring in the Saturnian system. This results in the re-determination of the Saturnian Q value, which is now estimated at 75.
This is lower than the previous one. The significance of this data, says Ula Jones, co-author of the study, “It expands the range of environments we might consider habitable.” This confirmed the importance of data archives when it comes to getting the most science bang for the buck, says Julie Castillo-Rogez, a planetary scientist at NASA’s Jet Propulsion Laboratory.
“It’s the gift that keeps giving,” Castillo-Rogez continues. But for those with more than a passing interest in space news, it’s essential to keep in mind that even the best-studied bodies of our solar system have had the biggest finds not hidden under the oceans but instead lie hidden under layers of ice. With this in mind and the new discovery of Titan and its characteristics regarding its subsurface ocean formation and implications of ocean world definitions as a whole, researchers are no longer thinking about “ocean worlds.” Instead, they are looking into other planets such as Europa and Enceladus that have a proven global ocean.
Additionally, as suggested above regarding Titan’s warm water pockets, this discovery opens up new and varied possibilities of habitability within the distant reaches of our solar system that are far greater than current thought. According to Castillo-Rogez: This research advance indicates the significance of nuclear propulsion and the challenges of solar propulsion and examining how nuclear propulsion can enhance the currently planned Dragonfly mission.
