Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Titan’s Seas Are Sand

05.05.2006


Until a couple of years ago, scientists thought the dark equatorial regions of Titan might be liquid oceans.

New radar evidence shows they are seas -- but seas of sand dunes like those in the Arabian or Namibian Deserts, a University of Arizona member of the Cassini radar team and colleagues report in Science (May 5).

Radar images taken when the Cassini spacecraft flew by Titan last October show dunes 330 feet (100 meters) high that run parallel to each other for hundreds of miles at Titan’s equator. One dune field runs more than 930 miles (1500 km) long, said Ralph Lorenz of UA’s Lunar and Planetary Laboratory.



"It’s bizarre," Lorenz said. "These images from a moon of Saturn look just like radar images of Namibia or Arabia. Titan’s atmosphere is thicker than Earth’s, its gravity is lower, its sand is certainly different -- everything is different except for the physical process that forms the dunes and resulting landscape."

Ten years ago, scientists believed that Saturn’s moon Titan is too far from the sun to have solar-driven surface winds powerful enough to sculpt sand dunes. They also theorized that the dark regions at Titan’s equator might be liquid ethane oceans that would trap sand.

But researchers have since learned that Saturn’s powerful gravity creates significant tides in Titan’s atmosphere. Saturn’s tidal effect on Titan is roughly 400 times greater than our moon’s tidal pull on Earth.

As first seen in circulation models a couple of years ago, Lorenz said, "Tides apparently dominate the near-surface winds because they’re so strong throughout the atmosphere, top to bottom. Solar-driven winds are strong only high up."

The dunes seen by Cassini radar are a particular linear or longitudinal type that is characteristic of dunes formed by winds blowing from different directions. The tides cause wind to change direction as they drive winds toward the equator, Lorenz said.

And when the tidal wind combines with Titan’s west-to-east zonal wind, as the radar images show, it creates dunes aligned nearly west-east except near mountains that influence local wind direction.

"When we saw these dunes in radar it started to make sense," he said. "If you look at the dunes, you see tidal winds might be blowing sand around the moon several times and working it into dunes at the equator. It’s possible that tidal winds are carrying dark sediments from higher latitudes to the equator, forming Titan’s dark belt."

The researchers’ model of Titan suggests tides can create surface winds that reach about one mile per hour (a half-meter per second). "Even though this is a very gentle wind, this is enough to blow grains along the ground in Titan’s thick atmosphere and low gravity," Lorenz said. Titan’s sand is a little coarser but less dense than typical sand on Earth or Mars. "These grains might resemble coffee grounds."

The variable tidal wind combines with Titan’s west-to-east zonal wind to create surface winds that average about one mile per hour (a half meter per second). Average wind speed is a bit deceptive, because sand dunes wouldn’t form on Earth or Mars at their average wind speeds.

Whether the grains are made of organic solids, water ice, or a mixture of both is a mystery. Cassini’s Visual and Infrared Mapping Spectrometer, led by UA’s Robert Brown, may get results on sand dune composition.

How the sand formed is another peculiar story.

Sand may have formed when liquid methane rain eroded particles from ice bedrock. Researchers previously thought that it doesn’t rain enough on Titan to erode much bedrock, but they thought in terms of average rainfall.

Observations and models of Titan show that clouds and rain are rare. That means that individual storms could be large and still yield a low average rainfall, Lorenz explained.

When the UA-led Descent Imager/Spectral Radiometer (DISR) team produced images taken during the Huygens probe landing on Titan in January 2005, the world saw gullies, streambeds and canyons in the landscape. These same features on Titan have been seen with radar.

These features show that when it does rain on Titan, it rains in very energetic events, just as it does in the Arizona desert, Lorenz said.

Energetic rain that triggers flash floods may be a mechanism for making sand, he added.

Alternatively, the sand may come from organic solids produced by photochemical reactions in Titan’s atmosphere.

"It’s exciting that the radar, which is mainly to study the surface of Titan, is telling us so much about how winds on Titan work," Lorenz said. "This will be important information for when we return to Titan in the future, perhaps with a balloon."

An international group of scientists are co-authors on the Science article, "The Sand Seas of Titan: Cassini Observations of Longitudinal Dunes." They are from the Jet Propulsion Laboratory, California Institute of Technology, U.S. Geological Survey - Flagstaff, Planetary Science Institute, Wheeling Jesuit College, Proxemy Research of Bowie, Md., Stanford University, Goddard Institute for Space Studies, Observatoire de Paris, International Research School of Planetary Sciences, Universita’ d’Annunzio, Facolt di Ingegneria, Universit La Sapienza, Politecnico di Bari and Agenzia Spaziale Italiana. Jani Radebaugh and Jonathan Lunine of UA’s Lunar and Planetary Laboratory are among the co-authors.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL.

Lori Stiles | University of Arizona
Further information:
http://www.lpl.arizona.edu/~rlorenz
http://www.nasa.gov/cassini
http://saturn.jpl.nasa.gov

More articles from Physics and Astronomy:

nachricht Further Improvement of Qubit Lifetime for Quantum Computers
09.12.2016 | Forschungszentrum Jülich

nachricht Electron highway inside crystal
09.12.2016 | Julius-Maximilians-Universität Würzburg

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: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>