Data from NASA's Cassini
spacecraft indicates that Saturn's moon Titan likely harbors a layer of liquid water under its ice shell. Researchers say they noticed a large amount of squeezing and stretching as the moon orbited Saturn. They deduced that if Titan were composed entirely of stiff rock, the gravitational attraction of Saturn would cause bulges (called solid tides) on the moon of about 1 meter in height. Cassini data shows Saturn creates solid tides approximately 10 meters in height, which suggests Titan is not made entirely of solid rocky material.
Luciano Iess, lead author of the paper published here
and a Cassini team member at the Sapienza University of Rome, Italy, says, "Cassini's detection of large tides on Titan leads to the almost inescapable conclusion that there is a hidden ocean at depth. The search for water is an important goal in solar system exploration, and now we've spotted another place where it is abundant."
Titan takes just 16 days to orbit Saturn. Scientists were able to study the moon's shape at different parts of its orbit. Because Titan is not spherical but slightly elongated like a football, its long axis grew when it was closer to Saturn. Eight days later, when Titan was farther from Saturn, it became less elongated and more nearly round. Cassini measured the gravitational effect of that squeeze and pull.
This artist's concept animation shows the solid tides on Titan raised by Saturn's gravity, as detected by NASA's Cassini spacecraft. Take a look:
a Q&A with sstudy lead author Luciano Iess (LI) and a co-author, planetary scientist Jonathan Lunine (JL) of Cornell, about the Titan subsurface ocean discovery.
Image: A. Tavani