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Titan’s dunes made of hydrocarbons instead of silicates

Titan’s dunes made of hydrocarbons instead of silicates

NEW YORK: There are dark and large fields of sand dunes on the surface of Saturn’s moon Titan, and this week two scientific papers look at how they came to surface. Titan is one of the most interesting moons in our solar system. It is the only other body moreover Earth that has standing reservoirs of liquid on its surface, but the lakes and rivers of Titan are filled with methane and ethane, rather than water.
It has a thick atmosphere, about 1.5 times as dense as what we have on Earth. A person standing on the surface of Titan would encounter the same pressure as if they were standing at the bottom of a swimming pool on our planet.
And near the equator, scientists have discovered another mysterious feature – dark sand dunes the color of tar that stand hundreds of feet tall and stretch hundreds of miles in length.
Sand dunes have been found in just a few places throughout the solar system – on Venus, Mars, Earth and Titan – but Titan is the only moon where dunes have been discovered.
The sand that makes up Titan’s dunes is not made of silicates like the sands we find on Earth, however. Instead, scientists believe it is made of hydrocarbons, and may include particles of water ice.
Because of their different compositions, the sands of Titan are much less dense and more powdery than the sand on Earth. Combine that with Titan’s low gravity, which is just one-seventh of the gravity of Earth, and you get “sand” that is as light as freeze-dried coffee grains.
To understand how a 300-foot-tall dune of this material might form on this distant moon, a team of scientists tried to recreate the conditions of Titan in a wind tunnel in Arizona State University’s Planetary Aeolian Laboratory. The wind tunnel was originally built in the 1980s to recreate the surface of Venus, but has been now been refurbished as a Titan simulator.
The results of their experiment, published Monday in a Nature study, revealed that it would take winds of at least 3.2 mph to lift the sand and cause it to move across the moon’s surface.
That may not sound very strong, but it is 40% to 50% stronger than previous estimates, the scientists said.