New research may have solved the mystery of what causes the depressions that form hydrocarbon lakes on the surface of Saturn's moon Titan.
Data from the joint NASA and European Space Agency (ESA) Cassini mission suggests the moon's surface dissolves in a process similar to the one that causes sinkholes on Earth, NASA's Jet Propulsion Laboratory reported.
Cassini has identified two types of methane- and ethane-filled depressions the make up a network of oceans, branching river-like channels, and smaller lakes; Cassini has also observed a number of empty depressions. The lakes are not believed to be connected to the other bodies of liquid, and exactly how the depressions came about in the first place has remained poorly understood.
To solve the mystery, a team of researchers turned to our own planet. The team determined Titan's lakes are similar to what are known as karstic landforms on Earth. These landscapes are caused by the erosion of dissolvable rock in rainfall and groundwater. This phenomenon eventually leads to features such as sinkholes, and the researchers believed something similar is happening on Titan. They determined it would take about 50 million years to create a 300-foot depression in Titan's rainy polar region.
"We compared the erosion rates of organics in liquid hydrocarbons on Titan with those of carbonate and evaporite minerals in liquid water on Earth," said Thomas Cornet of the European Space Agency. "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."
The scientists also calculated how long it would take to form these lake depressions at lower latitudes with lighter rainfall, and determined, and found the 375 million-year timescale in consistent with the lack of depressions in these regions.
"By comparing Titan's surface features with examples on Earth and applying a few simple calculations, we have found similar land-shaping processes that could be operating under very different climate and chemical regimes," said Nicolas Altobelli, ESA's Cassini project scientist. "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."
The research was recently published in the Journal of Geophysical Research, Planets.
