[X] My Assistant

[belleraphon1]

All...

the latest CHARM presentation details the longitudunal dunes on Titan.

http://saturn.jpl.nasa.gov/multimedia/prod...HARM_Lorenz.pdf

Slide 4 shows that Titan albedo features are buried in the old Voyager data. Neat.
Slides 11 is a great reprojection of DISR.
Several slides with great Earth SIR-C and CASSINI Titan dune comparisons.
Slide 41 shows a section of T21 with dunes that I do not believe has been released as yet.
Slide 42 dune orientations....
Slide 44 showing calculated paths for Titan balloon probes (data taken fron the dune orientations acting as weather vanes).

Very cool...

Doug.... I was not sure which Titan thread to place this in so I created one. Move it where it makes sense.

Craig

[Juramike]

Ewing et al Planetary Dunes Workshop (2008) Abstract 7031. “Three-dimensional characterization and morphological dynamics of gypsum sand dunes at White Sands National Monument using airborne LiDAR.”
I also found this handy reference on dunes: http://www.nps.gov/archive/whsa/Sand%20Dune%20Geology.htm

Ewing et al. correlated the dune shape with the topography left behind by several lakeshores. They found that “at the change in slope of each shoreline the dunes have sharper crests, more defects more narrowly shaped crests, and minimal interdune areas.”

If I understand this correctly, it should be possible to interpret the bottom topography of Titan’s sand seas by examining at the interdune area.



The graphic above is loosely based on Figure 1 in the Geology reference and is in reference to topographic change in the averaged downwind direction.
At wind goes over a steep slope, it drops speed and will lose energy needed to bounce along the saltating particles. The spoil area thus accumulates sand grains. I would assume that funky wind patterns (rotors, turbulence, etc.) would cause a very confusing dune pattern. In addition, it should dump sand everywhere, thus causing a smaller interdune area.

As wind is forced up a steep slope, it should increase speed (saltating particles cause friction and cause winds at the interface to be slower – mixing it with above interface winds should dramatically speed things up.). Increased speed means more energy to make saltating particles bounce longer, and stronger. This should sweep particles from lower friction-interdune areas. The result should be larger interdune areas.



To the W of the Evil Eye feature of W Quivira one can see a partial rim of wider interdune areas. This is a negative image, so dunes are bright and the interdune area is dark. This partial rim could correspond to an area where slopes are increasing (or where sand supply is limited).



Also in the T25 RADAR Swath, the region directly north of Sotra Facula has an interesting dune pattern. This is also a negative image so the dunes are bright and the interdune areas are dark. Here the dunes are initially few and far between in the dark-blue ice sand margin, most likely due to low sand supply. Moving to the E the pattern is nice and regular, then goes chaotic along a boundary running roughly NW-SE. The dune pattern changes away from linear dunes and almost appears as transverse dunes. This change would be consistent with a wind shadow effect (caused by a steep drop at the boundary indicated in blue) removing one of the wind vectors in this area. The dunes get confused and align with a more constant wind coming from the NW (which is also parallel to the putative gradient drop). This is consistent with a broad shelf off the land mass W of Quivira.

-Mike