Elevated areas on Saturn’s moon, Titan, may be tips of large icebergs pushing up on the moon’s rigid shell, which new research indicates could be much thicker than previously thought. The icebergs are believed to be floating on an underlying ocean 50 to 200 kilometers below.
Titan’s ocean could possibly support alien life.
Planetary scientists arrived at the iceberg theory because of odd gravitational measurements obtained by NASA’s Cassini spacecraft.
"Normally, if you fly over a mountain, you expect to see an increase in gravity due to the extra mass of the mountain," said Francis Nimmo
, a Cassini scientist who participated in a study published August 29 in the journal Nature
. "On Titan, when you fly over a mountain, the gravity gets lower. That's a very odd observation."
One possible explanation, according to the study, is that Titan’s topographical bumps are offset by a deeper “root” that overwhelms the gravitational effect of the bump. The root could act like an iceberg extending below the ice shell into an ocean underneath. Cassini would detect less gravity wherever there is a big chunk of ice instead of water because ice is less dense than water.
"It's like a big beach ball under the ice sheet pushing up on it, and the only way to keep it submerged is if the ice sheet is strong," said Douglas Hemingway, the paper's lead author and a Cassini team associate. "If large roots under the ice shell are the explanation, this means that Titan's ice shell must have a very thick rigid layer."
Titan is of great interest to scientists because it is the only moon in the solar system known to have clouds and a mysterious, thick, planet-like atmosphere. The moon is also believed to have stable lakes of liquid methane and ethane.
Here's a short video of Huygens' descent onto the surface of Titan: