Titan's Transforming Rainfall

The long-running Cassini orbital Saturn mission has revealed that there are hundreds of hydrocarbon lakes and seas located all over Saturn's moon Titan. Now new observations have led researchers to believe that they can explain, at least in-part, how methane rainfall replenishes these liquid landmarks.

A study recently published in the journal Icarus details how Titan's methane rainfall could be interacting with icy materials within underground reservoirs.

Olivier Mousis, a Cassini research associate at the University of Franche-Comté, France, suggests that these materials could be functioning much like aquifers, using the formation of clathrates to change the chemical composition of the rainfall into reservoirs of propane and ethane that work to feed the seas and lakes.

"We knew that a significant fraction of the lakes on Titan's surface might possibly be connected with hidden bodies of liquid beneath Titan's crust, but we just didn't know how they would interact," Mousis said in a statement. "Now, we have a better idea of what these hidden lakes or oceans could be like." (Scroll to read on...)

According to the study, clathrates are compounds that help water form a crystal structure with small cages that trap other substances like methane and ethane. On Titan, clathrates are expected to form when liquid hydrocarbons come into contact with ice, which makes up a great deal of the moon's surface.

Mousis and his team theorize that as long as these clathrates reach deep enough into the planet's crust, they should affect the methane reservoirs that are created by rain, slowly changing them into propane or ethane aquifers.

"Our study shows that the composition of Titan's underground liquid reservoirs can change significantly through their interaction with the icy subsurface, provided the reservoirs are cut off from the atmosphere for some period of time," added Mathieu Choukroun of NASA's Jet Propulsion Laboratory, one of three co-authors of the study.

The researchers conclude that lakes then fed by underground aquifers, and not by methane rain directly, would have different chemical compositions, making it easier to map the subsurface activity of the unusual moon.