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 Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science

nachricht NASA's fermi finds possible dark matter ties in andromeda galaxy
22.02.2017 | NASA/Goddard Space Flight Center

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Microhotplates for a smart gas sensor

22.02.2017 | Power and Electrical Engineering

Scientists unlock ability to generate new sensory hair cells

22.02.2017 | Life Sciences

Prediction: More gas-giants will be found orbiting Sun-like stars

22.02.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>