Titan's Hidden Ocean

Author:  Prakash Sheila

Date:  April 2008

Recent data from the Cassini-Huygens mission has revealed a drift in various geological features on Titan's surface, indicating that the moon may harbor an ocean under its thick layer of ice. This would make Titan the fourth satellite in our solar system, after Europa, Ganymede, and Enceladus, to be a potential reservoir for water.

Titan, Saturn's largest moon, has been the subject of scientific interest since 1980, when images from Voyager 1 indicated a dense atmosphere composed mostly of nitrogen. Titan also has rich deposits of liquid methane and hydrocarbons on its surface. These compounds are present en masse on Earth, making Titan a possible biosphere for life. The presence of an ocean would complete this picture.

"Titan is a really unique world in our solar system," said Ralph Lorenz, the leader of the study and a planetary scientist in the Applied Physics Laboratory at Johns Hopkins University, "A world where there's both water and lots of organic material is a very powerful combination that promises to tell us about the chemical evolution that leads to life.''

The first images from Cassini-Huygens were sent back in 2004. Images of Titan collected at that time revealed a largely solid surface spotted with dunes, channels, lakes and cryovolcanos. Three years later, Cassini-Huygens sent back more of these images for a second time. The updated images revealed a drift in these features, indicating liquid movement below.

The findings were published in the March 21 issue of Science. In the paper, Lorenz and colleagues reported that recent observational data from the mission is consistent with models predicting an ammonia-rich ocean on Titan.

A key discovery supporting this conclusion is the revelation that Titan's orbit is not synchronous. Scientists have long postulated that Titan is in synchronous rotation – that is, it always presents the same face to Saturn. Lorenz point out that the rotation period difference from synchronous spin is consistent with other observed characteristics of Titan only if the satellite's crust is separated from its core by an internal body of liquid form.

Titan is a rich and dynamic satellite with many profound similarities to Earth. The discovery of a liquid ocean on Titan could propel the satellite's status as one of the forerunners in the race to discover life in our solar system.

Written by Sheila Prakash

Reviewed by Yanguang Ou

Published by Pooja Ghatalia.