Arizona State University | Planetary Aeolian Laboratory | 2014 Dec 08
Saturn's largest moon, Titan, is one of the few solar system bodies – and the only planetary moon – known to have fields of wind-blown dunes on its surface. (The others are Venus, Earth and Mars.)
- [url=http://photojournal.jpl.nasa.gov/catalog/PIA11802][b][i]At the Edge of Titan's Dunes[/i][/b][/url] - [b][i]Credit: NASA/JPL-Caltech/ASI[/i][/b] [i]Lines of dunes crawl across the surface of Titan in a radar image showing dunes as dark. Experiments at ASU's wind tunnel indicate the dune particles move only under winds that blow stronger than scientists previously thought.[/i]
New research, using experimental results from the high-pressure wind tunnel at Arizona State University's Planetary Aeolian Laboratory, has found that previous estimates of how fast winds need to blow to move sand-size particles around on Titan are about 40 percent too low. ...
Saturn and Titan orbit about ten times farther from the sun than Earth. Scientists got their first detailed information about Titan when the Cassini/Huygens orbiter and lander arrived in 2004. The short-lived Huygens lander took photos when it reached the surface and as it was descending through Titan's dense, smoggy atmosphere, which has 1.4 times greater pressure than Earth's. These images, plus studies using instruments on the Cassini orbiter, revealed that Titan's geological features include mountains, craters, river channels, lakes of ethane, methane and propane – and dunes.
Dunes begin to form when the wind picks up loose particles from the ground and drives them to hop, or saltate, downwind. A key part of understanding dunes is to identify the threshold wind speed that causes dune particles to start to move. Geologists have found threshold speeds for sand and dust under various conditions on Earth, Mars and Venus. But for Titan, with its bizarre conditions, this remained unknown.
On Titan, where the surface temperature is negative 290 degrees Fahrenheit, even "sand" is probably unlike sand on Earth, Mars or Venus. From the Cassini observations and other data, scientists think it is composed of small particles of solid hydrocarbons (or ice wrapped in hydrocarbons), with a density about one-third that of terrestrial sand. In addition, Titan's gravity is low, roughly one-seventh that on Earth. Combined with the particles' low density, this gives them a weight of only about four percent that of terrestrial sand, or roughly as light as freeze-dried coffee grains. ...
Answers Blowing in the Titan Wind
SETI Institute | 2014 Dec 08
Higher-than-predicted saltation threshold wind speeds on Titan - Devon M. Burr et al
- Nature (online 08 Dec 2014) DOI: 10.1038/nature14088