August 27, 2009

Alternate Titan dune origin theory offered

U.S. scientists have developed an alternate theory for the origin of linear dunes on the surface of Titan, Saturn's largest moon, similar to ones on Earth.

Louisiana State University Professor Patrick Hesp and U.S. Geological Survey scientist David Rubin said they examined the linear -- or longitudinal -- dunes stretching across the surface of China's Qaidam Basin, finding them composed of sand and some salt and silt.

The scientists said the latter two elements make the dunes cohesive or sticky, leading to a change in dune form from transverse to linear, even though wind speed and direction do not change. Typically, they said, transverse dunes are formed by winds from a narrow directional range, while longitudinal or linear dunes are formed by winds from two obliquely opposing directions.

Hesp and Rubin said their findings offer an alternative interpretation of similar dunes found on Titan. They suggest that if the giant linear dunes on Titan are also formed from cohesive sediment, then they, too, could be formed by single-direction winds. That contradicts earlier studies that assumed the sediments were loose and interpreted the Titan dunes' shape as evidence of winds coming from alternating directions.

Hesp and Rubin said if their theory is correct, hypotheses regarding the composition, origin and other factors involving Titan's sediment will have to be reassessed.

The study appears in the online edition of the journal Nature Geoscience.