by Mary Caperton Morton Monday, March 9, 2015
Saturn’s largest moon, Titan, is covered with extensive fields of sand dunes around its equator. From a distance, the wind-swept landscape looks similar to those seen on Earth, Mars and Venus, but new research suggests that dune formation on Titan may require different conditions than previously thought.
Computer models of sand dunes are based on observations recorded in the field on Earth and in wind-tunnel experiments, but whether these models are accurate for other planets is unknown. Previous work focusing specifically on Titan’s dunes failed to identify wind patterns that could have built the dunes, or to resolve a timescale for their formation. Two new modeling studies, both based on images captured by the Cassini spacecraft, suggest that, to form, Titan’s dunes require higher wind speeds sustained over much longer timescales than would be expected for dunes on Earth.
The first study, led by Devon Burr of the University of Tennessee at Knoxville and published in Nature, indicates that only rare strong westerly winds control dune movement, rather than the easterly winds thought to be most common on Titan. A second study, led by Ryan Ewing at Texas A&M University and published in Nature Geoscience, calculated that dune crests would have taken roughly 3,000 Saturn years — equivalent to about 88,000 Earth years — or longer to form. This timescale exceeds those of diurnal, seasonal, or tidal wind cycles, which have previously been suggested as drivers for the dune patterns seen on Titan.
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