The electric sands of Titan

Date:

Share post:

Experiments led by researchers at the Georgia Institute of Technology suggest the particles that cover the surface of Saturn’s largest moon, Titan, 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 electric sands of Titan
An artist’s rendering of the surface of Titan, a moon of Saturn 
[Credit: iPhoto Stock, manjik]

“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.”

The electric sands of Titan

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.”

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.

The electric sands of Titan
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]

“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 the moon 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.”

The findings have just been published in the journal Nature Geoscience.

Author: Jason Maderer | Source: Georgia Institute of Technology [March 27, 2017]

ADVERTISEMENT

spot_img

Related articles

NuSTAR finds new clues to ‘chameleon supernova’

"We're made of star stuff," astronomer Carl Sagan famously said. Nuclear reactions that happened in ancient stars generated...

Scientific research will help to understand the origin of life in the universe

Scientists from Samara University and several universities in the USA have proposed and experimentally confirmed new fundamental chemical...

Scientists discover new exoplanet with an atmosphere ripe for study

An international group of collaborators, including scientists from NASA's Jet Propulsion Laboratory and The University of New Mexico,...

NASA scientis simulates sunsets on other worlds

Have you ever wondered what a sunset on Uranus might look like? As you can see in the...

Using Earth’s history to inform the search for life on exoplanets

UC Riverside is leading one of the NASA Astrobiology Program's eight new research teams tackling questions about the...

Shedding light on galaxies’ rotation secrets

The dichotomy concerns the so-called angular momentum (per unit mass), that in physics is a measure of size...

NASA’s Voyager 2 probe enters interstellar space

For the second time in history, a human-made object has reached the space between the stars. NASA's Voyager...

Galaxies are running out of gas

The Universe forms fewer stars than it used to, and a CSIRO study has now shown why -...