sunset from behind the wire

sunset from behind the wire

Tuesday, March 28, 2017

Sticky World

A visitor from Space (think UFO and Illegal Space Alien who may or may not speak English as a second language) would doubtless find conditions on Earth to be different than they may have before they sent spies in and among us with human skins. Cars may not turn out to be the dominant life form with biological organisms seeing to their every need like parasites...etc. You get the point. The "take me to your leader" line doesn't work on a Ford pick up waiting patiently in line at Taco Bell.

This composite image shows an infrared view of Saturn's 
moon Titan from NASA's Cassini spacecraft, acquired during 
the mission's "T-114" flyby on Nov. 13, 2015. Credit: NASA/JPL
That also may be true of Saturn's largest moon, Titan, where the sands are "electrically charged." When the wind blows hard enough (approximately 15 mph), Titan's non-silicate granules get kicked up and start to hop in a motion referred to as saltation. As they collide, they become frictionally charged, like a balloon rubbing against your hair, and clump together in a way not observed for sand dune grains on Earth -- they become resistant to further motion. They maintain that charge for days or months at a time and attach to other hydrocarbon substances, much like packing peanuts used in shipping boxes here on Earth.

The findings have just been published in the journal Nature Geoscience. 
J. S. Méndez Harper, G. D. McDonald, J. Dufek, M. J. Malaska, D. M. Burr, A. G. Hayes, J. McAdams, J. J. Wray. Electrification of sand on Titan and its influence on sediment transport. Nature Geoscience, 2017; DOI: 10.1038/ngeo2921
"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 Josef Dufek, the Georgia Tech professor who co-led the study. "Any spacecraft that lands in regions of granular material on Titan is going to have a tough time staying clean. Think of putting a cat in a box of packing peanuts."

The electrification findings 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 Josh Méndez Harper, a Georgia Tech geophysics and electrical engineering doctoral student who is the paper's lead author. "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."

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 percent 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 2 to 5 percent didn't come out of the tumbler," said Méndez Harper. "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."

They don't hold together without water.
Earth sand does pick up electrical charge when it's moved, but the charges are smaller and dissipate quickly. That's one reason why you need water to keep sand together when building a sand castle. Not so with Titan.

"These non-silicate, granular materials can hold their electrostatic charges for days, weeks or months at a time under low-gravity conditions," said George McDonald, a graduate student in the School of Earth and Atmospheric Sciences who also co-authored the paper.

Visually, Titan is the object in the solar system most like Earth. Data gathered from multiple flybys by Cassini since 2005 have revealed large liquid lakes at the poles, as well as mountains, rivers and potentially volcanoes. However, instead of water-filled oceans and seas, they're composed of methane and ethane and are replenished by precipitation from hydrocarbon-filled clouds. Titan's surface pressure is a bit higher than our planet -- standing on Titan would feel similar to standing 15 feet underwater here on Earth.

"Titan's extreme physical environment requires scientists to think differently about what we've learned of Earth's granular dynamics," said Dufek. "Landforms are influenced by forces that aren't intuitive to us because those forces aren't so important on Earth. Titan is a strange, electrostatically sticky world."

12 comments:

  1. I'm not sure that Cher will appreciate her new digs on Titan, where the dirt actively seeks you out and then sticks to you for weeks/months. And then there's no water there to wash any of it off.

    But I suppose Cher will like it on Titan more than the intolerable planet that Donald Trump is messing up with all of his evil conservatism.

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    1. If Cher goes, I have a very long list including the great, near great, who should join her along with members of the elite, corrupt, lying, smug mainstream media who need to join with the exodus to chronicle it.

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  2. So, when Cher goes, will Oprah and Miley stick to her as they drown in the DNC lakes of methane?

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    1. Are you CERTAIN that Cher, Oprah and Miley are not from Titan originally - having emerged from the primordial oooooze?

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  3. I'm claustrophobic, so I think I will stay here and enjoy crawfish. Thank you, enjoyed this a lot.

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    1. JPL has designed a submarine (robotic) to explore the lakes of Titan. I have no idea if it will ever fly there. I pick up arcane bits of information like this and retain it - disturbing even to me.

      Sit on the porch, can fresh peaches, enjoy crawfish and the local fair. It's more fun than going to Titan would be.

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  4. Good read, but I had a thought. With hydrogen being 95% of Titans atmosphere, wouldn't we blow the moon to smithereens if we tried to land there (with our rocket propelled engines), or would there need to be be the third element of oxygen to ignite it? Inquiring minds want to know. I just know better than to get a lighter close to my bum after eating at Taco Bell.

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    1. I honestly don't know what percentage of the whole that hydrogen needs to be combustable without an oxidizer. On Earth there is plenty of oxygen. The surface of Titan is covered in methane hydrocarbon lakes but I think that you're in the same boat without oxygen, so the Taco Bell (run for the border) scenario may not work the same way. And with sticky sand covering your body and the space ship, it could get ugly...

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    2. Didn't the article say that Titan's atmosphere is over 98% nitrogen? OTOH, Jupiter has an abundance of molecular hydrogen, as well as massive lightning strikes, so H2 alone (pretty much, ignoring inert He) is apparently not enough.

      But it's all ridiculously cool: The universe is not only stranger than you think, it's stranger than you can think. (Or than I can think, at any rate.)

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    3. Fact Check: The atmospheric composition in the stratosphere is 98.4% nitrogen—the only dense, nitrogen-rich atmosphere in the Solar System aside from Earth's—with the remaining 1.6% composed of mostly of methane (1.4%) and hydrogen (0.1–0.2%).

      So there is no danger of sparking a cook-off. As you point out, Jupiter (a failed star) is rich with hydrogen.

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  5. Strange at best, fascinating that they've been able to 'duplicate' what they think happens!

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    1. You need to have your space troopers land on a "sticky world".

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