Titan May Hide a Water Ocean

The moon Titan is the largest of all about 60 natural satellites orbiting around Saturn. In fact, it is larger than the smallest planet in the solar system, Mercury. Also, Titan is the only moon in the solar system known to have a thick atmosphere around it, filled with organic molecules, precursors to the appearance and evolution of life. Its surface is covered with lakes of natural gas in quantities so large that a single lake of this type could power the industry of the whole North American continent for 300 years or more.

It is believed that, similarly to Earth's water precipitations, the weather on Titan is regulated by rains of natural gas. Cryovolcanoes that eject water and ammonia into its atmosphere are not an alien sight on Titan. Now researchers argue that there is enough evidence to suggest that Titan might be hiding an ocean of water deep underground, thus joining the select group of moons thought to hide water oceans: Ganymede, Callisto and Europa.

Cassini radar team researcher Ralph Lorenz says that "Models of heat flow in Titan's interior suggested years ago that Titan would likely have an internal water or ware-ammonia ocean." The main piece of evidence suggesting it is that the moon's surface seems to have drifted. The Cassini orbiter creates radar images of the moon's surface in little strips, thus, while trying to create a map of the surface using individual strips of images, some of them overlapped, although the coordinates associated to them were completely different.

What could cause this?

One of the explanations for the phenomenon is that, in fact, the atmosphere is so dense that it is affecting the spin rate, thus producing errors of reading because the orbiter is configured to make measurements in relation to a constant spin ratio. If this is true, then the atmosphere of Titan may produce, at some point in time, either an acceleration or a deceleration in the speed of rotation.

Lorentz said: "Titan's winds should spool up and spin down with the seasons, and because Titan's atmosphere is so massive and Titan is relatively small, the winds have a measurable impact on Titan's rotation. If you adjust the parameters of how Titan rotates very slightly, we could make the features on the maps match up."

Although the phenomenon might seem rather strange to me and you, the fact is that also the Earth suffers the influence of the atmosphere on the spin speed, but the change is so small that we hardly notice it. Earth's spin duration was approximated to vary with 1 millisecond a year, but because Titan is much smaller the effect could be severely amplified.

Water ocean

Further still, for the crust of Titan to move so quickly, it has to be supported on a liquid layer. The natural prediction is that it is most likely a liquid water ocean. Measuring about 5,150 kilometers in diameter, Titan may have an ocean between 100 to 200 kilometers deep, covered by a layer of ice 50 to 150 kilometers thick. The core is believed to be 3,000 to 3,400 kilometers in diameter, consisting of rock.

In addition to water, Titan's underground ocean may also contain some traces of ammonia and primitive organic molecules. "Whether life has ever evolved on Titan is another question, but whether it did or didn't, Titan can tell us about the chemical processes that ultimately lead to life," said Lorenz.

To test the theory, the Cassini orbiter will have to carry out magnetic and gravity measurements. Alternatively, Lorenz proposed that a seismometer to be set on the surface of Titan to measure the movements of the icy crust. Lorenz reveals that such an instrument could be sent to Titan by the end of 2017 by one of the two leading space agencies, the ESA and NASA.

False alarm?

The second and most likely explanation for the change in Titan's spin rotation, involves reoccurring wobbles in its orbit. It could take more than six year to make detailed observations to determine whether the spin of Titan is varying, thus to test the water ocean theory. "If there is the presence of an ocean there, with a pressure and the temperature very similar to Earth's oceans, the question of life is now open for Titan," said NASA Jet Propulsion Laboratory planetologist Christophe Sotin.



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