Do Methane Rivers on Titan Obey the Same Rules as Those on Earth?

Recent evidence from the Huygens Probe of the Cassini Mission suggests that Titan, the largest moon orbiting Saturn, is a world where rivers of liquid methane sculpt channels in continents of ice.

Surface images even show gravel-sized pieces of water ice that resemble rounded stones lying in a dry riverbed on Earth.

Gary Parker, the W.H. Johnson Professor of Geology and a professor of civil and environmental engineering, has collected data from rivers all over the world. Using that data, he has calculated what should be key similarities and key differences between river networks on Earth and Titan.

"The idea that rivers of methane moving chunks of ice on Titan ought to obey the same rules as rivers on Earth is not what you would assume at first," said Gary Parker, the W. H. Johnson Professor of Geology and a professor of civil and environmental engineering at the University of Illinois at Urbana-Champaign.

There are only three parameters that differ significantly between Earth and Titan, Parker said. First is the acceleration due to gravity, on Titan it is about one-seventh the value on Earth. Second is the viscosity of flowing fluid, the viscosity of liquid methane on Titan is about one-fifth that of water on Earth. Third is the submerged specific gravity of sediment, the value on Titan is about two-thirds of that on Earth.

"What this means is that for the same discharge of liquid methane as to water, the channel characteristics on Titan should be remarkably similar to those on Earth," Parker said.

"However, because of the smaller acceleration due to gravity, channel slopes on Titan should be wider, deeper and less steep than those on Earth."

The Huygens Atmospheric Structure Instrument has also revealed strong turbulence in the upper atmosphere, a second ionospheric layer and possible lightning.

HASI provided measurements from an altitude of 1400 km down to the surface of the physical characteristics of the atmosphere and surface, such as temperature and density profiles, electrical conductivity, and surface structure. The Huygens SSP made measurements just above and on the surface of Titan.

Very little was known about the surface of Titan because it is hidden by a thick 'haze', initial speculation was that the surface was covered by a deep hydrocarbon ocean, but infrared and radar measurements showed definite albedo contrasts, possibly consistent with lakes, but not with a global ocean.