Titan’s hydrocarbon lakes, seen here in radar images, boast life-friendly chemistry (Image: NASA/JPL)

Saturn’s frigid moon Titan may be friendlier to life than previously thought. New calculations suggest Titan’s hydrocarbon lakes are loaded with acetylene, a chemical some scientists say could serve as food for cold-resistant organisms.

At about -180 °Celsius, Titan’s surface is far too cold for liquid water. But two pairs of scientists proposed in 2005 that alien organisms might live instead in bodies of liquid hydrocarbons on the frigid moon. They suggested such organisms could eat acetylene that falls to the surface after forming in the atmosphere, combining it with hydrogen to gain energy.

Since then, Cassini has spotted dozens of lakes on Titan’s surface, thought to be made of a mixture of liquid ethane and methane. But since no probe has directly sampled them, no one knows how much acetylene they might contain.


An estimate made in 1989 suggested bodies of liquid hydrocarbons on Titan would contain a few parts in 10,000 of acetylene.

But an updated estimate based on data from the Cassini-Huygens mission to Saturn now suggests the lakes contain much more food for any hungry alien life-forms that might be present. The new calculations were made by a team of scientists led by Daniel Cordier of the Ecole Nationale Supérieure de Chimie de Renne, France.

Right temperature

Data from the Cassini spacecraft and the Huygens probe, which parachuted to Titan’s surface in 2005, helped Cordier’s team re-calculate the lakes’ likely composition. This depends on factors like a lake’s temperature, which affects how easily chemicals will dissolve in it, and the rate various chemicals are produced in the atmosphere and rain onto the surface.

The team found that acetylene would be hundreds of times as abundant as the previous estimate, making up one part in 100 of the lake’s content.

“Having about a per cent of acetylene is potentially interesting from the life point of view,” says team member Jonathan Lunine of the University of Arizona in Tucson. The idea of acetylene-eating organisms on Titan is “highly speculative” but intriguing, he says.

Separate layers

“I think the results are very exciting and further support the possibility for life on Titan,” says Dirk Schulze-Makuch of Washington State University in Pullman, one of the scientists who proposed the possibility of acetylene-eating life in 2005. “Titan should be one of the two top targets for future astrobiology missions, the other being Mars.”

But Tetsuya Tokano, a Titan researcher at the University of Cologne in Germany, says the exact amount of acetylene may be less important than other properties of the lakes that remain unknown, such as the existence of currents to keep them well-mixed.

Tokano pointed out in a recent study that without mixing, hydrogen and acetylene would stay in separate layers of the lakes, limiting reactions between them that might otherwise power exotic organisms.

Journal reference: Astrophysical Journal Letters (in press)