[X] My Assistant

[Juramike]

On the other hand, the dunes 20km away must have been formed under dry conditions, but
that doesnt make them dry now...

Those far-away dunes have been really bugging me. Why don't they overlap over the Huygens landing site?

The VIMS data indicates that there is a blue-brown dark region (with more ice) as well as a darker brown dark zone in the Equatorial Sand seas. The darker brown material seems to correlate well with the dune material. The bluer material seems to be closer to the "coasts".

If the winds are easily marching around the dune material, why don't they cover up the blue-brown dark material?

Is it because:

a) The blue brown dark material is topographically higher, kind of like an alluvial fan or slight continental edge? (Earth analog: Glacial Lake Bonneville in the Great Basin of Nevada)

b) The wind shadow of the raised "islands" make the dunes wrap around these areas.

c) Periodic dampening (either by stream runoff and soaking in to the depths of the Equatorial Sand Seas or stream runoff followed by evaporation) causes the creeping dune material to not build up.

d) Major runoffs wash away any dunes that try to form too close to the "brightlands".

e) Some other reason.

[Juramike at scientific conference in LA this week. Juramike hotel and computer have slow viscous dial-up - no can check SAR images.]

Has anybody seen cat-scratch dune features close to brightlands areas without rivers?

Has anybody seen cat-scratch dune features close to a major outflow rivers near the "brightlands" in RADAR images? Do they seem further away than "normal" ?

Are there any areas of blue-brown dark material that also have cat scratches in RADAR images?

Does anyone know if really detailed altimiter data exists across any sections of the Equatorial Sand Seas? (even the basin area near Huygens landing site would be great - is the 20 km distant cat scratch area lower?)

Are Equatorial Sand Seas flat or do they have a beveled edge along the sides? (like the mountains in Great Basin area)


Could there be three terrain types in the Equatorial Sand Seas: dune material, blue-brown dark material (presumably outwash), and another hidden layer we haven't seen yet by VIMS buried under either the dune material or the outwash material?

-Mike

[volcanopele]

I suspect it is a combination of some of these factors. We know b plays a role based on the RADAR coverage of some of the smaller faculae show dune draping, creating stream-lined forms. In ISS and VIMS data, we see this wind-shadow as either intermediate albedo or dark blue material, almost always on the east side of bright terrain. These areas likely consist of runoff from the bright terrain with gravel or larger grain sizes. The sand-sized particles have all been picked up by the wind and blown into the ergs.

Altimetry data shows the dune fields to be VERY flat with the individual pulses showing both the tops and bottoms of the dunes. Bright faculae were found to be up to 500 meters above the surrounding erg.

The dune fields in central Adiri aren't close to any large river.

[Juramike]

Since the wind shadow seems to extend to the E, what happens on the west side (windward) of bright highlands near large streams?

Do the dunes march up into the river deposit area?
Or is the continental outlflow able to push back the dune area and keep it at bay (pun intended)?

Does VIMS show blue dark area at this margin, or is it brown dark?

-Mike

[Juramike]

Alkali blum occurs in heavily salted lake beds, such as Lake Powell and Lake Mead. As the water is drawn by capillary action through cracks in the mud, the mineral salts are deposited in frost-like structure that follows the cracks. Experienced 4-wheelers know to avoid driving on blum because it means the water table is less than a foot below the surface.

Very interesting idea.

I would picture an multicomponent organic residue left by dissolved organics after the volatiles have evaporated as being a globby, waxy, kinda smooth mess instead of like needle-sharp salt crystals. But I have no idea if acetonitrile (for example) could be easily fractionally recrystallized from other organics and what form it take. [I've recrystallized compounds from acetonitrile, but have never tried to recrystallized acetonitrile itself - this would make a fun lab experiment at -78 C].

I'd imagine a hydrocarbon residue "organic pan" would be smooth and therefore radar dark.

But it might show up by VIMS. It might leave a different spectral signature or stain.

I wonder if there are any spurious VIMS stains in the Equatorial Sand Seas, assuming they are not covered up by dune fields?

Would these be located close to the brightlands, due to runoff? Or way out in the middle areas of the Equatorial Sand Seas?

-Mike

[ngunn]

Can you see the sea???
http://saturn.jpl.nasa.gov/multimedia/imag...9/N00081037.jpg
I'd have expected it to be on the terminator around 10 or 11 o'clock.

[ngunn]

New (well, newly processed) on Ciclops:
http://ciclops.org/view.php?id=2883

[Guest_Sunspot_*]

But what happened to the RADAR views? Maybe they are waiting and intend to hold a press briefing.

[Olvegg]

I fear they're waiting for next flyby to release results from all three at once.

[Exploitcorporati...]

A fragment of one of the recent swaths (T28?) was included in the Titan Flagship Study and captures the south shore of the Lake Superior-sized sea seen at the tail of the T25 pass. The channels are really spectacular...

[volcanopele]

Good catch! (you are not by any chance on a certain IRC channel are you?)

[Exploitcorporati...]

No, sadly I can't seem to get IRC to work properly. I stumbled across it in the OPAG thread. Did a little double-take at first.

[JRehling]

The channels are really spectacular...

It looks to me like the channels cut into a floodplain between the lowest and highest liquifer levels. Which is not remotely surprising itself, except that the channels proceed almost parallel to the shoreline in that area. Whereas with, say, the Earth's own Caspian Sea, the rivers flowing in tend to be perpendicular to the shoreline.

http://www.iranchamber.com/geography/artic...a_satellite.jpg

(don't confuse national borders with rivers!)

...befitting a naive model in which the lake is the lowest level in the region, with the topography increasing gradually and monotonically with distance from the lake, and the channel paths following the direction of that slope to a fair approximation.

That says something interesting about the relationship between Titan's topography and fluid-borne erosion. The channels seem to "bull" their way through terrain which is not generally eroded towards a level plain on larger scales. In other words, the terrain is at least somehow more like Greece than it is like southern Russia.

[Phil Stooke]

Here's a higher res grab of the new section.

I don't think the channel geometry is at all unusual. Any bit of random relief near the shoreline will divert a channel.

Phil

[Guest_Sunspot_*]

They should use Radar on all the passes.

[volcanopele]

I'm sure VIMS, INMS, Radio bistatic, and gravity teams would be thrilled with that prospect...