23 Jul 2012
NASA's Cassini radar images show river networks draining into lakes in Titan's northern polar region. CREDIT: NASA/JPL/USGS

The thick and hazy atmosphere of Titan, Saturn's largest moon, may hide a geological past similar to erosion seen on Earth according to a new study. 

Researchers from the Massachusetts Institute of Technology (MIT) in Cambridge and the University of Tennessee at Knoxville studied images of Titan taken from the Cassini spacecraft and have investigated the erosion of its terrain over millions of years by rivers of liquid methane.

Their findings showed that is some areas, the network of rivers caused little erosion, possibly implying that erosion was occurring slowly or that something more recent has altered the ancient riverbeds and landforms.

"It's a surface that should have eroded much more than what we're seeing, if the river networks have been active for a long time," according to co-author Taylor Perron, an assistant professor at MIT.   "It raises some very interesting questions about what has been happening on Titan in the last billion years."

Titan's Past Exposed

Titan is estimated to be four billion years old, roughly the same age as the rest of the solar system.  The atmosphere of titan is made up of methane and nitrogen, which creates an orange thick haze that prevents astronomers from seeing the surface, at least until 2004.  In 2004, NASA's Cassini spacecraft was able to pierce through the clouds and took radar imagery.  Cassini still flies past Titan as it orbits Saturn.

From the radar images, scientists can see that Titan's icy terrain was carved by rivers of liquid methane over millions of years.  This process is similar to how rivers on Earth carve out our continents.  Even though Titans current landscape is well documented, much of its geologic past is a mystery.

Instead of being littered with craters like most moons in the solar system, Titan's surface is smooth.  If you judge the age based on surface features, you would think it is only 100 million to 1 billion years old.  Of course this isn't the reality.

Researchers used Earth's features and processes to explain Titan's smooth surface.  "We don't have many impact craters on Earth," Perron stated.  "People flock to them because they're so few and one explanation is that Earth's continents are always eroding or being covered with sediment.  That may be the case on Titan too," he elaborated.

Using Earth for Clues

Similar to the processes on Earth, things like tectonic plate motion, icy lava eruptions, erosion, and sedimentation may have been factors on Titan.

Determining which processes are the cause is tricky because the radar images don't give details on elevation and depth.

Scientists are comparing imagery from Earth with that of Titan to help find some clues.

"It's a weirdly Earth-like place, even with this exotic combination of materials and temperatures," Perron said, elaborating that "So you can still say something definitive about the erosion.  It's the same physics."

The detailed study results will be published in an upcoming issue of the Journal of Geophysical Research-Planets.

Source:  Space.com


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