Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Research Offers Explanation for Titan Sand Dune Mystery

10.12.2014

Titan, Saturn's largest moon, is a peculiar place. Unlike any other moon in our solar system, it has a dense atmosphere.

 Thanks to imagery from NASA’s Cassini spacecraft, we also know that Titan has rivers and lakes made of ethane and methane, as well as windswept sand dunes that are dozens of yards high, more than a mile wide and hundreds of miles long. What scientists have not known is how they were created, because current data suggested that Titan’s winds were not strong enough to form the dunes spotted by Cassini.


Image credit: NASA/JPL - upper photo; NASA/JSC - lower photo

Cassini radar sees sand dunes on Saturn's giant moon Titan (upper photo) that are sculpted like Namibian sand dunes on Earth (lower photo). The bright features in the upper radar photo are not clouds but topographic features among the dunes.

A team of researchers has now shown that winds on Titan must blow 50 percent faster than previously thought in order to move that sand. This discovery may explain how the dunes were formed and could inform observations made on other planetary bodies. The findings are published in the current edition of the journal Nature.

Scientists were amazed by the first radar images of Titan returned by the Cassini spacecraft a decade ago. The images showed never-before-seen dunes created by particles not previously known to have existed.

"It was surprising that Titan had particles the size of grains of sand—we still don’t understand their source—and that it had winds strong enough to move them," said Devon Burr, an associate professor in the Earth and Planetary Sciences Department at the University of Tennessee, Knoxville, and lead author of the paper. "Before seeing the images, we thought that the winds were likely too light to accomplish this movement."

The biggest mystery, however, was the shape of the dunes. The Cassini data showed that the predominant winds that shaped the dunes blew from east to west. However, the streamlined appearance of the dunes around features like mountains and craters indicated they were created by winds moving in exactly the opposite direction.

“Until now, there’s been a big mystery as to why most winds on Titan blow from the east, yet the dunes appear to form from westerly winds,” said Nathan Bridges, planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland and a co-author of the paper.

To solve that mystery, Burr and her team dedicated six years to refurbishing and modifying a defunct NASA high-pressure wind tunnel to recreate Titan's surface conditions. To reproduce the Titan environment at Earth temperatures (much higher than Titan’s), they pressurized the wind tunnel to 12.5 atmospheres (equivalent to being about 385 feet underwater) that correctly simulated wind physics at Titan’s pressure of 1.4 bars (similar to 13 feet underwater) [CORRECTED DEC 9 2014 APL].

To account for the very low gravity and density of sand on Titan, and given the uncertainties in the actual materials on the moon, they used 24 different substances, including very low weight particles such as hollow glass spheres and walnut shells. Two years were spent running the experiments, modeling the results, and calibrating the models to match the observations. These adjustments were made to find the best simulation of Titan’s dense atmosphere.

"Our models started with previous wind speed models, but we had to keep tweaking them to match the wind tunnel data," said Burr. "We discovered that movement of sand on Titan's surface needed a wind speed that was higher than what previous models suggested."

When the researchers zeroed in on the most accurate model, they discovered that the minimum wind speed on Titan has to be about 50 percent faster than previously thought to move the moon’s sands.

The discovery of the higher threshold wind offers an explanation for the shape of the dunes, too. "If the predominant winds are light and blow east to west, then they are not strong enough to move sand," said Burr. "But a rare event may cause the winds to reverse momentarily and strengthen."

According to atmospheric models, the wind reverses twice during a Saturn year (which is equal to about 30 Earth years). This reversal happens when the sun crosses over the equator, causing the atmosphere—and subsequently the winds—to shift. Burr theorizes that it is only during this brief time of fast winds blowing from the west that the dunes are shaped. "The high wind speed might have gone undetected by Cassini because it happens so infrequently," she said. The team’s finding also validates the use of older models for bodies with thin atmospheres, like comets and asteroids.

Bridges emphasizes that “were it not for these experiments, we never would have determined that the wind speeds necessary to move sand on Titan predicted by previously published models were too low. Our results, reconciled with the recalibrated models, explain why dunes on Titan can only move under rare gusts from westerly winds.”

This research was supported by grants from NASA's Planetary Geology and Geophysics Program and the Outer Planets Research Program. A new grant will now allow the team to examine Titan's winds during different climates on Titan, as well as the effect of electrostatic forces on the sand movement.

Burr’s team includes UT Earth and Planetary Sciences Assistant Professor Josh Emery as well as colleagues from Johns Hopkins APL, SETI Institute, Arizona State University, and the University of California, Davis.

Media contacts:

Whitney Heins, University of Tennessee, Knoxville (865-974-5460, wheins@utk.edu)

Geoffrey Brown, Johns Hopkins Applied Physics Laboratory (240-228-5618, Geoffrey.Brown@jhuapl.edu)

Geoffrey Brown | newswise

Further reports about: Applied Physics Cassini Dune Earth Hopkins Johns Hopkins Laboratory Mystery Titan Titan’s particles wind speed wind tunnel

More articles from Physics and Astronomy:

nachricht Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory

nachricht SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>