Nasa’s cassini orbiter discovers coarse, flat dun landscapes on saturn’s moon titan that are reminiscent of terrestrial forests

Sand duns not only characterize the face of the sahara or the desert gobi – they also extend to the earth’s neighbors mars and venus in certain regions of coarse flats. Recent images of saturn’s moon titan taken by the radar imager of nasa’s cassini research orbiter now prove that sandy desert areas also enrich the landscape on saturn’s moon titan. In "science" (5. May 2006), the researchers are particularly impressed by the dune fields that dominate the coarse, near-aquatorial areas of saturn’s moon. However, it is still completely unclear how they were created and what they are made of exactly.

Nearly 1.5 billion kilometers from earth, a man-made earthly envoy with full diplomatic powers is on a delicate mission. Although the second most powerful planet in the solar system has warmly welcomed him and accepted him into the family of the 47 other satellites known so far. But the accredited newcomer is by no means immune to cosmic immunity.

The wustensatellite

Image from nasa’s cassini orbiter (26. October 2004). Image resolution: two to four kilometers per pixel

For even nasa’s cassini spacecraft is not immune to the prevailing harsh cosmic climate on the ringed planet saturn, where vast quantities of dust and myriad chunks of ice and rock of various kinds have made the orbit unsafe for thousands of years "immune". Nevertheless, cassini’s instruments are still working at full speed today, and continue to provide researchers with new data material – as the powerful radar instrument of the cassini spacecraft did once again in october 2005.

Sand dunes of water ice crystals?

As an international team of scientists led by ralph lorenz of the lunar and planetary laboratory at the university of arizona (tucson/arizona) reported in today’s ie of the u.S. Journal science (5), the planet is the second most powerful satellite in the solar system. May 2006, bd. 312, s. 724-727), the earthly "nasa ambassador" cassini discovered in october of the last year on the coarse saturn moon titan a far stretched sandy dunenlandschaft, which have many characteristics with the sahara, the namib desert in nambia (africa) and the coarse arab desert, the rub al khali in saudi arabia in common. "In terms of geometry, length and width, the dunes resemble those we know from the namib desert and the rub al khali. They show patterns and topographic structures that have direct parallels with terrestrial desert regions," explains nicholas lancaster, who is one of the world’s leading experts on sand dunes, in an accompanying article in "science" (5). May 2006, bd. 312, s. 702).

Huygens image during landing approach from eight kilometers high

In the images taken by the cassini radar imager, huge sand crusts with long dune ridges can be seen near the aquator, towering up to 150 meters and hundreds of kilometers long. The longest sand dune ridge extends over an area 1500 by 200 kilometers coarse. Although the chemical composition of the surface material of the sand dunes is unknown, the researchers suspect that they are composed either of organic material based on methane – or simply of water ice crystals.

Coarse sand grains

The presence of sand dunes on titan suggests geological processes that favor the formation of sand-sized grains: particles that are at least 100 to 300 micrometers in coarseness, the researchers write in science. Thus the titanic sand grains were allowed to be about three times thicker in comparison to the terrestrial fine and medium sand. Since the sand duns are roughly arranged in an east-west direction, researchers suspect that they were formed by easterly winds.

The wustensatellite

Titan – the desert satellite: cassini radar image of desert-like structures with dark ridges near the aquator of saturn’s satellite

In order to demand the material, the wind on titan needs to blow only weakly because of the low gravity of the moon. For the transport of the sand grains, a wind speed of about ten to seventy millimeters per second was sufficient, which can also be attributed to the low gravity of the moon.

Back with balloon?

The presence of the deposits indicates a dry area without vegetation structures or coarser areas of lakes or other fluids. Otherwise, the researchers around ralph lorenz ame, the granular material would have been caught by it.

The desert satellite

Radar image of the namib desert in namibia (africa); taken by the u.S. Spacecraft endeavour on 9. April1994

Since the sand craters were located exactly in those dark areas around the titan equator where oceans had been suspected until recently, it is finally clear that there were no oceans with liquid methane, at least in this region, the scientists report in "science"

It is bizarre. The images of saturn’s moon look like radar images of namibia or arabia. It is exciting that cassini’s radar, which was designed primarily to study titan’s surface, tells us so much about the wind patterns there. This information will be helpful when we visit titan again in the future, perhaps by balloon.

Ralph lorenz on space.Com

Geologically active satellite

Researchers have known that titan is a geologically active satellite since esa’s huygens spacecraft landed on 14. January 2005. Thanks to the bits and bytes that esa’s lander radioed to earth during its nearly four-hour operational phase, titan revealed itself to be a celestial body with a dynamic atmosphere and a vibrant history. Because in the course of its history, the surface of the moon has been subjected to enormous, earth-shattering geological processes that have caused major changes.

These dynamics are clearly reflected in the huygens images, which show intricate surface structures indicative of wind action, tectonic processes, and fluvial processes. They also show some circular shapes which could be impact craters and flux-like structures. And since cassini-huygens, planetary scientists also know that titan is a windy satellite: in the lower atmosphere at a height of eight kilometers, winds whip around it at a speed of five to six meters per second – in its troposphere, the "air masses" even whip around at a speed of no less than 34 meters per second.

The wustensatellite

Picture from huygens video "a view from huygens – jan. 14, 2005"

Months earlier, the nasa orbiter’s radar system had detected faint indications of the transport of light material on the surface of saturn’s moon, suggesting wind activity. On the pictures nasa and esa scientists recognized only dark stripes and diffuse patterns, which were not very informative. With the cassini images of october 2005, however, they could improve the resolution by a factor of 300 and thus prove that titan, at least at the aquator, is a genuine desert satellite is.

Nasa and esa published a few hours ago two very interesting videos/animations of the huygens landing in january 2005: nasa, esa

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