Luciano Iess: Liquid ocean on Saturn’s moon Titan

Cassini spacecraft observation of “tides” in the solid surface of Titan suggest that this large moon of the planet Saturn has an ocean below ground.

Scientists have long suspected that Saturn’s largest moon, called Titan, might have a liquid ocean beneath its surface. New analysis of data from NASA’s Cassini spacecraft now has lead to the “almost inescapable” conclusion that, indeed, Saturn’s moon Titan likely harbors a layer of liquid water under its ice shell. This finding appeared in the June 28, 2012 issue of the journal Science. EarthSky spoke to planetary scientist Luciano Iess of Sapienza University in Rome, Italy, who led the discovery team. He said:

The main finding is that underneath the external icy crust of Titan, there is an underneath ocean. There is a liquid layer. The study was carried out by studying, essentially, the tides on Titan.

This artist’s concept shows a possible scenario for the internal structure of Titan, as suggested by data from NASA’s Cassini spacecraft. Scientists have been trying to determine what is under Titan’s organic-rich atmosphere and icy crust. Image credit: A. Tavani

Unlike the tides familiar to beach-goers on Earth, the tides on Titan are up and down movements of the surface ice. Earth also undergoes measurable land tides, caused by our nearby moon. If Titan were made entirely of stiff rock and ice, the scientists say, the gravitational attraction of Saturn would cause “tides” on Titan’s solid surface about three feet (one meter) in height. Instead, according too the estimates of Iess and his team, Titan’s tides are as large as about 30 feet (10 meters) – 10 times larger than anticipated.

The height of these moving bulges, or tides, suggests Titan is not made entirely of solid rocky material. That is why, scientists believe, there must be liquid water beneath Titan’s surface.

The height of the land tides on Titan let Iess’ team estimate the amount of water in Titan’s underground ocean. Iess said there could be more than 10 times all the water of Earth. Because Titan’s surface is mostly made of water ice, which is abundant in moons of the outer solar system, scientists infer Titan’s ocean is likely mostly liquid water. Otherwise, Iess said, little is known about the underground ocean on Titan.

On Earth, water means life. Does the presence of an underground ocean on Titan indicate there is life on this moon of Saturn? Dr. Iess said:

We have discovered water. We don’t have to expect that this water contains life. It may or may not. I’m personally rather skeptical, but this is a matter of judgment, which may not be too scientific after all.

Saturn’s largest moon, Titan, as seen by the Cassini spacecraft. When we gaze at the moon with the eye, we see only the upper layers of its dense atmosphere. But many mysteries lie beneath.

The Cassini spacecraft made it possible to measure the height of the tides of solid ice on Saturn’s moon Titan. Cassini has been orbiting Saturn, and winding among the ringed planet’s moons, since 2004.

Bottom line: Cassini spacecraft observation of land tides in the solid surface of Titan suggest that this large moon of the planet Saturn has an ocean of liquid water below its icy surface. Planetary scientist Luciano Iess of Sapienza University in Rome, Italy led the discovery team. The team made their announcement in late June 2012.

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