Yes, even years ago one could notice the darker character near the south pole in low-res images that helped set the stage for the unfolding mysteries. In some cases it seems to me to be due to rougher more chaotic terrain having more shadows (particularly with low sun angles). I suppose the albedo of the surface might differ a bit as well, either due to the bluish ice regions or possibly other coloring agents? Along Mosul Sulci there is a dark strip in B&W imagery that shows up as bluish in the "Great Southern Land" released mosaic.

The Frothy Faithful (and Frigid Faithful model too, I think) both explain a deposition of crystalline ice near the vents.
Check out:
Fortes Icarus 191 (2007) 743-748. “Metasomatic clathrate xenoliths as a possible source for the south polar plumes of Enceladus.” doi: 10.1016/j.icarus.2007.06.013 (Pay-for article, abstract available here).

If I understood the model correctly, here’s how the Frothy Faithful model works:
1) Volatiles produced by hydrothermal activity at rock-ice interface.
2) Volatile gases move around in solution by circulating hot magmatic fluids (hot water).
3) Gassy fluids contact ice, clathrates formed and emplaced.
4) Melts move the clathrate chunks to higher levels in the crust.
5) Above a certain point, clathrates no longer stable, they break down and release gases. (Crustal depths of 20 km or so.)
6) Gas pressure drives water magma and chunks upward.
7) Clathrate breakdown cools water magma gently and produces crystalline ice at depth.
8) Spray of gasses and ice crystals shoots out in a narrow jet (like out the barrel of a rifle), not in an umbrella-like plume.
9) Crystalline ice snows around the the vents
(I think the Frigid Faithful model might also allow slow crystallization of water at depth.)

So the pretty blue ice is consistent with both the Frigid Faithful and Frothy Faithful

Also according to the article, the Frothy Faithful model predicts "vigorous 'plucking' of the conduit walls" to rip up and throw the blocky debris found near the vents. The coarsest stuff (cryoclastic materials) will be closest to the vent/fractures. That could also make the stripes appear bluish, as the CICLOPS caption mentions.

-Mike

Interesting Mike, maybe worth stopping by the library. And here's another related abstract/paper:

http://www.sciencedirect.com/science?_ob=A...482747265f6c06a

"These results suggest recent geological activity at the “tiger stripe” cracks and an intriguing atmospheric environment over the south pole where amorphous ice is produced either through intense radiative bombardment, flash-freezing of cryovolcanic liquid, or rapid condensation of water vapor particles on icy microspherules or on the surface of Enceladus."

Creating natural-color looking imagery from IR/G/UV should be fairly straightforward, the moon is not a very colorful place and it would basically boil down to finding the right channel mix and saturation level to match the tiger stripe colors. The slight problem is we don't have a good high resolution shot of the stripes taken in RGB color for reference. We're stuck with distant imagery that doesn't resolve the sulci very well.

For a first iteration it would suffice to take IR3(or better IR1)/GRN/UV3 images and just desaturate them in Photoshop by say 50 units. That would leave them at roughly the "natural" amount of saturation, only the blue hue would possibly be slightly off in realistic color. Then again, blue is blue is blue - it's all subjective anyway...

Thanks for that link!
The companion paper behind it is also very interesting:
http://www.sciencedirect.com/science?_ob=A...3d30810dc34335f


"Our measurements show that the particle diameter of water ice increases toward younger tectonically altered surface units with the largest particles exposed in relatively “fresh” surface material. The smallest particles were generally found in old densely cratered terrains. The largest particles ([ca.] 0.2 mm) are concentrated in the so called “tiger stripes” at the south pole. In general, the particle diameters are strongly correlated with geologic features and surface ages, indicating a stratigraphic evolution of the surface that is caused by cryovolcanic resurfacing and impact gardening."

Ice chunks coughing out of the vents, snow everywhere else...

-Mike

The color has a lot to do with phase angle. In full-disc images, Europa, for example, seems to have a bluer limb in "true color" imagery, so red is absorbed more when it has to double back through the ice. Note that even though this effect is seen over global scales (because only over global scales on a sphere does the angle of incidence change), it may be taking place in extremely tiny scales -- whether the light penetrates one times epsilon or two times epsilon before it reflects back. Finely granulated surfaces equalizes the situation, because each tiny granule is its own spheroid, whether near the center of the disc or the limb.

Fallout from Enceladus's jets ought to land without any gas between the particles. I would assume that they would eventually fuse pretty thoroughly to the surface, although with Enceladus's weak gravity, tiny ice particles may flow pretty slowly.

Has anyone heard how long it will take for the CIRS data to be released? I remember for the march flyby it being about a month, has there been any hints whether it will be the same length of time? If I was six I'd be shouting 'are we nearly there yet?'. I'd really like to know which mechanism for the plumes the temperature data supports. I do appreciate it takes time to get these things right, and they need to be right before they get released, but if anyone has a time frame for it it might help control my inner child!

Thought I'd revisit the question (perhaps to VP) of how these nifty mosaics are constructed as I may be able to add the color info from this (and similar mosaics) into my Enceladus map. In the caption it mentions an orthographic projection so I assume it means viewing from an infinite distance. I also assume the triaxial shape of Enceladus was taken into account in doing the mapping. Is this mosaic however shown reprojected onto a sphere, or onto the ellipsoid?

Overall I'm past the halfway point in renavigating my entire Enceladus map. I'm also adding in several B&W images from the Rev 80 flyby.

That's the latest,

Steve

I was off at a wedding during the Enceladus flyby, got sidetracked by the frantic preparations for the flight out of Calgary, and only just now got around to going through this thread (and checking out the pictures).

Wow. You go away for a couple of months and everything changes. That's Cassini for you.

Thought I'd share this "work in progress" version of my Enceladus map. The entire map has been renavigated and 5 images from the August encounter are included to help show the south polar regions at high resolution. Color information has been added from the "Great Southern Lands" mosaic. The full-res map is at http://laps.noaa.gov/albers/sos/sos.html#ENCELADUS. Shown below is a quarter-res version:

Click to view attachment

Here are a few of the items I'm continuing to look at to try and improve the map:

1) adjust the navigation on the "frame 4" image over the south pole from the August encounter as some mismatches are evident

2) adjust image brightnesses to reduce some of the obvious seams

3) extend coverage of the August imagery over Mosul Sulci

4) attempt to reproject some of the other released color mosaics onto a cylindrical projection so I can utilize the color info. This appears to be a non-trivial exercise for some or the mosaics, compared with the "Great Southern Lands".

That's the latest,

Steve

We have now released some information on the temperatures we saw in the August 11th encounter- see the latest Cassini news release. It took us a while, because we had some calibration issues with data from that flyby, but we're now comfortable saying that observed temperatures along the part of Damascus Sulcus that we saw in detail were in the 160 - 167 K range. Temperatures could be hotter elsewhere, of course, and we also can't rule out tiny areas at higher temperatures in the regions where we did look.

The press release also says a bit about the magnetometer results from the August flyby, in addition to looking forward to the October flybys.

OK, please settle down in the back seat now

John.

Thanks John S and every one working on Cassini, I will now sit quietly and enjoy my goodies!

Raw images are now available.
http://pds-imaging.jpl.nasa.gov/data/cassi...ter/coiss_2047/