Saturn’s Moon Titan Has Electrically-Charged, 'Sticky' Sand
"If you grabbed piles of grains and built a sand castle on Titan, it would perhaps stay together for weeks due to their electrostatic properties."
Titan imaged in infrared. Image: NASA/JPL/University of Arizona/University of Idaho
Titan, Saturn's largest moon, is one of the weirdest places in the solar system, and that's a competitive category. Veiled in a thick nitrogen-rich atmosphere, the moon is home to liquid methane oceans, mountain ranges that may contain massive cryovolcanoes, and the now-defunct Huygens lander, which Saturn's long-lived Cassini orbiter dropped off in 2005.
Given its reputation as a world of active and bizarre phenomena, it should come as no surprise that scientists now think Titan might also be covered with electric sands. According to new research published Monday in Nature Geoscience, tiny non-silicate particles on the moon's surface could become electrically charged by frictional energy generated by collisions with each other at wind speeds surpassing 15 miles per hour.
These electrified particles may maintain their charge for weeks or even months at a time, which would significantly impact the surrounding sand grains and hydrocarbon compounds. This process, known as triboelectrification, has also been observed on Earth, but Titan's low-gravity environment likely enhances the effect. Bound together by electrostatic chains, Titan's sands may be much more cohesive and resistant to being picked up and scattered by the moon's winds.
"If you grabbed piles of grains and built a sand castle on Titan, it would perhaps stay together for weeks due to their electrostatic properties," said study co-lead Josef Dufek, a professor and geophysicist at Georgia Tech, in a statement.
"Any spacecraft that lands in regions of granular material on Titan is going to have a tough time staying clean," he added. "Think of putting a cat in a box of packing peanuts."
Long-lived sand castles on alien moons, and carefully packaged cats? Those are quality visual metaphors for understanding the dynamics at play on Titan's electro-sticky surface. Of course, in order to definitively confirm the new theory, we would need to chuck another lander over to Titan to build said robust sand castles. But Dufek and his colleagues did the next best thing by simulating the moon's environment in their Georgia Tech laboratory.
The team inserted grains of naphthalene and biphenyl, compounds that are likely to exist on Titan, into a modified tumbler device and rotated them for 20 minutes in a nitrogen-rich environment. The electric charge of the material was then measured as the grains were sifted out, which confirmed that these compounds do become electrified in Titan-like surroundings. Some of the grains even stuck to the side of the cylinder, demonstrating the sticky quality that would make Titan such a promising world for sand castle enthusiasts.
The team's findings may help contextualize some of Titan's most perplexing features, including regions of sand dunes that appear to be sculpted in the opposite direction of the moon's east-west prevailing winds. Lead author Josh Méndez Harper, a geophysics and electrical engineering doctoral student at Georgia Tech, suggests that clustered sands may be responsible for this mysterious phenomenon.
"These electrostatic forces increase frictional thresholds," Méndez Harper said in a statement. "This makes the grains so sticky and cohesive that only heavy winds can move them. The prevailing winds aren't strong enough to shape the dunes."
It goes to show that you should never underestimate the sheer oddness of the Titanian landscape. Just when you think you have a handle on this cloudy world, an even weirder development arises. It will be hard to top Titan's electric beaches, but no doubt this moon will find a way.
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