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New analysis reveals erosional history of Titan, Saturn’s largest moon

Thursday, August 2, 2012
New analysis reveals erosional history of Titan, Saturn’s largest moon
Since 2004, NASA’s Cassini-Huygens spacecraft has been peering through the hazy atmosphere of Saturn’s largest moon, Titan, and delivering images back to Earth. This has given scientists the opportunity to study the landscape of Titan for the first time ever.

CIFAR Scholar Taylor Perron, with colleagues at MIT and University of Tennessee, has now analyzed the radar images and noticed a few unusual patterns on the moon’s surface. Methane rivers have carved and shaped the landscape over millions of years. Titan also has a smooth surface, with an unusually small number of craters. The research team asked, ‘could the rivers have caused enough erosion to erase other craters, or did some other process do most of the resurfacing?’

The team investigated the role of river erosion in smoothing or resurfacing Titan’s terrain. They studied regions on Titan where river networks are common, and found that some rivers had caused very little erosion of the landscape – less than 10% of the initial height of the topography – suggesting other geological processes were probably responsible for the reshaping. But, there were some areas where more erosion may have occurred. Future research will be needed better understand these regional differences.

The paper is now in press, and will soon be published in the Journal of Geophysical Research. We talked to Dr. Perron to find out why he is excited about these new findings from Titan.

Why are you interested in studying river networks and erosion on Titan?

Titan appears to be the only body in the solar system, other than Earth, where rivers are currently carving into the surface. We have many examples of rivers on Earth, but they all formed under the same gravity and with the same fluid – water. Titan's rivers formed under a different gravity and atmospheric pressure than Earth's, and at different temperatures. The combination of liquid methane/ethane eroding into ice on Titan is completely foreign to us, and yet we see landscapes that are surprisingly similar to those of Earth. So, we want to understand how they formed. Titan is an experimental setting that is larger than what any laboratory could produce, and the experiment has already been carried out for us over geologic time.

What kinds of questions do you hope to answer by studying the landscape of Titan?

We want to understand the extent to which rivers have modified Titan's surface. Titan has few impact craters relative to other icy moons, such as Jupiter's moons Ganymede and Callisto, which tells us that something has renewed its surface. We want to know whether erosion by rivers might have been responsible.

We also want to know how active Titan's rivers are, and by extension what the weather is like at Titan's surface. Do the rivers flow all the time, or only occasionally, during heavy rainstorms? And how long has this been going on? Is it a recent phenomenon, or has Titan's surface had river networks for most of its history?

How do you see your findings from Titan being used by scientists?

It isn't feasible to do controlled experiments with rivers that span many kilometers and millions of years, but Titan has done it for us, under exotic conditions. This gives us a fantastic chance to test the theories for describing and predicting the form of rivers that we have developed on Earth.

I also hope our findings will help our colleagues understand the other geologic mechanisms that have shaped Titan's surface. And perhaps this will help us plan the next spacecraft mission there, by showing us where to look for the most active rivers.

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