Peak Oil on Saturn Moon: Hydrocarbons Possibly Running Out On Titan

Titan is the only other place in the solar system besides Earth that has stable liquid on its surface. Scientists think methane is at the heart of a cycle at Titan that is somewhat similar to the role of water in Earth's hydrological cycle -- causing rain, carving channels and evaporating from lakes. But the supply of the hydrocarbon methane at Titan could be coming to an end soon (on geological timescales), according to new research done by a team led by Christophe Sotin of NASA's Jet Propulsion Laboratory.

By tracking a part of the surface of Saturn's moon Titan over several years, NASA's Cassini mission has found a remarkable longevity to the hydrocarbon lakes on the moon's surface. Feeding these results into a model suggests a lowing down of the whole cycle that points at a loss of methane that is not replenished anymore.

This can be concluded due to the fact that the lakes seem remarkably consistent in size and shape over several years of data from Cassini's visual and infrared mapping spectrometer suggests that the lakes evaporate very slowly. Methane tends to evaporate quickly, so scientists think the lakes must be dominated by methane's sister hydrocarbon ethane, which evaporates more slowly.

The lakes are also not getting filled quickly, and scientists haven't seen more than the occasional outburst of hydrocarbon rain at the moon over the mission's eight-plus years in the Saturn system. This indicates that on Titan, the methane that is constantly being lost by breaking down to form ethane and other heavier molecules is not being replaced by fresh methane from the interior. The team suggests that the current load of methane at Titan may have come from some kind of gigantic outburst from the interior eons ago possibly after a huge impact. They think Titan's methane could run out in tens of millions of years.

So it will still last considerably longer than the large methane reservoirs on Earth, called natural gas down here. And long enough for humans to get to Titan and exploit the largest natural gas field of the solar system there, although at that point it will be only useful as rocket fuel.