IANSMar 28, 2017 15:34:38 IST
The particles that cover the surface of Saturn's largest moon, Titan, are "electrically charged", show results of an experiment. The findings, published in the journal Nature Geoscience, may help explain an odd phenomenon — prevailing winds on Titan blow from east to west across the moon's surface, but sandy dunes nearly 300 feet tall seem to form in the opposite direction. "These electrostatic forces increase frictional thresholds," said the lead author of the study, Josh Mendez Harper from Georgia Institute of Technology (Georgia Tech) in the US.
"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," Mendez Harper said. To test particle flow under Titan-like conditions, the researchers built a small experiment in a modified pressure vessel in their Georgia Tech lab. They inserted grains of naphthalene and biphenyl — two toxic, carbon and hydrogen bearing compounds believed to exist on Titan's surface — into a small cylinder.
Then they rotated the tube for 20 minutes in a dry, pure nitrogen environment. Titan's atmosphere is composed of 98 per cent nitrogen. Afterwards, they measured the electric properties of each grain as it tumbled out of the tube. "All of the particles charged well, and about two to five per cent didn't come out of the tumbler," Mendez Harper said. "They clung to the inside and stuck together. When we did the same experiment with sand and volcanic ash using Earth-like conditions, all of it came out. Nothing stuck," Mendez Harper explained.
The Earth sand does pick up electrical charge when it is moved, but the charges are smaller and dissipate quickly. That is one reason why you need water to keep sand together when building a sand castle. Not so with Titan, according to the study. "These non-silicate, granular materials can hold their electrostatic charges for days, weeks or months at a time under low-gravity conditions," co-author George McDonald from Georgia Tech said.