Lakes on Saturn's Moon, Titan, May be Similar to Sinkholes on Earth

Scientists have uncovered some mysterious lakes on Saturn's moon, Titan. Now, they've taken a closer look at what causes the depressions on the surface and how they become filled with liquid hydrocarbons.

Apart from Earth, Titan is the only world in our solar system that's known to possess surface lakes and seas. These bodies of liquid have been spotted by NASA's Cassini spacecraft. However, at Titan's frigid surface temperatures (which are about minus 292 degrees Fahrenheit), liquid methane and ethane rather than water dominate Titan's hydrocarbon equivalent of Earth's water.

In this case, Cassini has identified two forms of methane- and ethane-filled depressions that create distinctive features near Titan's poles. There are vast seas several hundred miles across and up to several hundred feet deep, fed by branching, river-like channels. There are also several, shallower lakes with rounded edges and steep walls that are generally found in flat areas.

The lakes normally fill up with rainfall and from liquids feeding them underground rather than by rivers.  In order to find out how these depressions form, though, the researchers turned to Earth.

The scientists found that Titan's lakes are similar to what are known as karstic landforms on Earth. These are terrestrial landscapes that result from erosion of dissolvable rocks, such as limestone and gypsum, in groundwater and rainfall percolating through rocks. Over time, this leads to features like sinkholes and caves in humid climates, and salt-pans where the climate is more arid.

It takes about 50 million years to create a 300-foot depression at Titan's polar region. This is consistent with the age of the moon's surface.

"Of course, there are a few uncertainties: The composition of Titan's surface is not that well constrained, and neither are the long-term precipitation patterns, but our calculations are still consistent with the features we see today on Titan's relatively youthful billion-year-old surface," said Thomas Cornet, one of the researchers, in a news release.

The findings reveal a bit more about Titan, and show exactly what kind of processes help shape this world.

The findings are published in the Journal of Geophysical Research: Planets.

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