A new study published online in the journal Nature on December 8, conducted in a NASA improvised wind tunnel, has shown how sand dunes form on Titan, the largest moon of Saturn.
The study was also conducted to find out why the dunes appear to be formed in a direction opposite to that of Titan's prevailing winds.
Titan is believed to be the only body in our solar system other than Venus, Earth and Mars to have wind-blown dunes on its surface.
Titan's massive dunes, some of them hundreds of feet high and hundreds of miles in length, have a thick atmosphere and dense hydrocarbon lakes filled with methane and ethane.
The scientists have been studying the mechanism of formation of these gigantic, undulating mounds for decades.
Dunes are formed when the wind picks up loose particles from the ground and drives them to hop, or saltate, downwind.
A key part of understanding dunes is to identify the threshold wind speed that causes dune particles to start to move.
Geologists have found threshold speeds for sand and dust under various conditions on Earth, Mars and Venus. But for Titan, with its bizarre conditions, this remained unknown.
Using data gathered from the Cassini orbiter, the NASA researchers have found that the dunes are composed of hydrocarbons, and may possibly include particles of water ice that are coated with these organic materials. On Earth and Mars, sand dunes are composed largely of silicates.
The researchers, led by Devon Burr, a planetary scientist at the University of Tennessee who formerly worked at the SETI (Search for Extra-Terrestrial Intelligence) Institute, used a high-pressure wind tunnel to simulate the wind conditions on Titan.
They found that the wind speed necessary for creating hydrocarbon-laden sand dunes on the moon was about 50% higher than previous estimates.
A separate study on the correlation between the dune patterns and climate cycles on Titan also claimed that the shift in winds could be a result of a shift in long-term climate cycles associated with variations in Saturn's orbit.
The study found that as a result of shifting winds, dunes on Titan could have taken nearly 3,000 Saturn years, or nearly 90,000 Earth years to form.
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