Titan's Alien Lakes: Explaining Confounding Formations

It's no secret that Titan is spotted with lakes and even seas of liquid methane. And while the seas of this moon have their own magic, it was the lakes that always had experts scratching their heads. Unlike with craters and glacial paths on Earth, the formation of lakes on Titan was a complete mystery, until now.

Thanks to extensive observations from the Cassini spacecraft - a join operation between NASA, the Italian Space Agency, and the European Space Agency (ESA) - scientists determined not-too-long-ago that the lakes of Saturn's most recognizable moon are not the products of pooling river-flow. Numerous and small, these lakes are instead depressions in Titan's surface that fill and empty of liquid hydrocarbons over the 30-year rain season it shares with its host planet. However, what remained unclear is how exactly those depressions got there in the first place.

For the most part, the depressions do not resemble impact craters - although how exactly an asteroid might affect Titan's intriguing surface remains unclear. Instead, experts have found strong evidence that Titan's lakes are reminiscent of what are known as karstic landforms on Earth.

These landforms were once thought unique to our Blue Planet, but there has always been a chance that other rainy worlds could experience the same phenomenon. It occurs when frequent rainfall and swells of "groundwater" (in Titan's case, its actually liquid methane and ethane) peculate through the weakest parts in a slab of rock. These weak points usually consists of 'chalky' dissolvable stone such as limestone and gypsum. It is theorized that large enough chunks of these rocks embedded in something far more solid could one day give way and become the lakes and sinkholes that speckle Titan. (Scroll to read on...)

"We compared the erosion rates of organics in liquid hydrocarbons on Titan with those of carbonate and evaporite minerals in liquid water on Earth," research lead Thomas Cornet, of the ESA, said in a statement. "We found that the dissolution process occurs on Titan some 30 times slower than on Earth due to the longer length of Titan's year and the fact it only rains during Titan summer. Nonetheless, we believe that dissolution is a major cause of landscape evolution on Titan and could be the origin of its lakes."

"Of course, there are a few uncertainties," he added.

Namely, experts are still uncertain of the exact composition of Titan's surface. However, this remains the best explanation they have, and is even consistent with predictions that there just hasn't been enough time for lakes to mar the naked surface of the mysterious moon's lower altitudes - as seen by Cassini last December.

"This is a great comparative study between our home planet and a dynamic world more than a billion kilometers away in the outer solar system," added Nicolas Altobelli, the ESA's Cassini project scientist.

Study results are detailed in full in the Journal of Geophysical Research, Planets.

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