[X] My Assistant

[ngunn]

Kraken Mare should be near the extreme right of this image. I've been staring at it pretty hard but can't be sure I'm seeing anything. Can anybody find a way to pull the lake out of these latest images?

http://saturn.jpl.nasa.gov/multimedia/imag...4/N00120245.jpg

[Juramike]

http://saturn.jpl.nasa.gov/multimedia/imag...4/N00120245.jpg

Oh baby! The equatorial section in the image is the part of Titan I've been really waiting to see!

Lookit all them complex cool-o shapes!

[volcanopele]

Meh, we've seen this area before at higher resolution last year

I'll be looking for Kraken Mare in a bit, I'll let you know if I find it. Keep in mind that it is pretty close to the terminator AND the limb up there, so it may not be visible in those compressed, 8-bit jpegs.

[ugordan]

This is the most I can get out of the terminator region:



It holds promise for the original raw data.

[ngunn]

Thanks Gordan. I think I can make a couple of dubious identifications of the shoreline there but too uncertain to be worth noting. I look forward to the professional version VP.

[alexiton]

crypto defogged & reweighted N00120245 + Closeup:

http://i225.photobucket.com/albums/dd78/al...dball3small.jpg

[Juramike]

crypto defogged & reweighted N00120245 + Closeup:

http://i225.photobucket.com/albums/dd78/al...dball3small.jpg

That dark region to the north still looks like it's darker than it should be.

Odd.

[ngunn]

The simulated view in 'looking ahead' shows that the follow-up images from 21st September are from a better angle for lake viewing. Not yet on the raw image page last time I looked, but I'm keeping fingers crossed.

[ngunn]

Gordan, now we have the images from 21-22 September with the lake showing clearly would there be any chance of a commparison image to set beside your last one in post 4? I want to try viewing both as 3D and see if Kraken Mare matches any faint features on the 20 September view.

[ugordan]

There'd be no use in 3D as the moon rotates in addition to the phase angle changing. I forgot the exact procedure I used on the Sep 20th images so can't repeat it, but here's a (better IMO) shot at the Sep 22th images:



September 25, very low phase:

[ngunn]

Nice - thanks. It's clear from the 20/22 comparison that the two rightmost extremities of Kraken Mare are (just) discernible in the earlier view. You'd be surprised at what I try to do cross-eye 3D with sometimes but you're right, that pair is giving me too much of a headache.

[ugordan]

Cloudy weather up in the north, September 30 images:

[volcanopele]

I had just about given up hope for seeing clouds, but there they are. These seem to be in the same 56 deg. North range as other streak clouds seen in the north.

[tedstryk]

Ugordan, excellent work. What might be neat is to merge these images with color images (in other words, color data from true or close to true color imaging with a grayscale that is a mix of these processed images and the grayscale data from the color image. It wouldn't be "true," but it would give it a Titan-ish feel).

[ngunn]

I had just about given up hope for seeing clouds

I wonder if you could clarify something for me? Ciclops 'looking ahead' for rev 85 mentioned looking for changes at Kraken Mare. Did that mean clouds, or something else?

[ugordan]

Here's a fudge job of a MT1 (atmospheric) filter with the processed Sep 22 view colored to resemble what an "enhanced" natural color view of the surface would be. Since the dark ground regions are visible only in the red filter, they appear greenish in natural colors as other filters only let through the brighter haze color:



Compare to actual enhancements of natural color images I did with calibrated data:
http://www.flickr.com/photos/ugordan/82044...57594305164185/
http://www.flickr.com/photos/ugordan/81921...57594305164185/

(Note in the second image above you can actually hint at the surface without additional enhancements)

[volcanopele]

These observations were primarily designed to monitor clouds on Titan. Obviously, only this latest one appears to actually show clouds. One thing that could also be done with these images is to also look for surface changes. One features I am particularly look at is Kraken Mare. That should not be taken to mean that we have seen changes there, but given the resolution of these images and the regions they cover, Kraken Mare seems to be the best candidate to at least take a look. As far as I can tell, I can't see any changes.

[tedstryk]

Cool!

[Juramike]

http://www.flickr.com/photos/ugordan/81921...57594305164185/

Very cool!

In Gordan's image above he notes a bright spot S of Adiri ("the 8 o'clock position cloud").
This picture was taken December 14, 2004.

You can see another bright spot in about the same location in an image taken June 14, 2007 in PIA08995. At the time, it was noted as most likely to be a cloud (Equatorial Sand Seas thread, post 180)

Two bright spots, three years apart. It's either a particularly bright spot on the surface, or there is another cloud-forming region in this area.

(That's really neat how Gordan is able to extract info from those pictures. Nice dig!)

-Mike

[titanicrivers]

"Two bright spots, three years apart. It's either a particularly bright spot on the surface, or there is another cloud-forming region in this area."

Looks like the mid-southern latitude clouds are persistent! More Cassini views of the 12-2004 clouds are shown in the first two images below; Roe et.al. at Caltech using Keck clearly imaged clouds at that latitude 2 months earlier in 2004. (right image)

[Juramike]

Interesting. Maybe there is a southern highland S of Adiri that makes a topographic bump after all...

I'll speculate on it now, and if SAR RADAR or Altimetry provides actual evidence I'll get to do my happy dance.

-Mike

[titanicrivers]

"I'll speculate on it now, and if SAR RADAR or Altimetry provides actual evidence I'll get to do my happy dance".

Roe et al speculate in their article in Science ‘Titan's mid-latitude clouds’ http://www.lowell.edu/~hroe/titanmidlat2005/index.html what they think is generating the clouds. Makes interesting reading!.

[titanicrivers]

[quote name='Juramike' date='Oct 4 2008, 04:52 PM' post='127741']
Interesting. Maybe there is a southern highland S of Adiri that makes a topographic bump after all...

I'll speculate on it now, and if SAR RADAR or Altimetry provides actual evidence I'll get to do my happy dance.

If one looks at the Cloud appearance map in Roe, A below, and relates it to Cassini images B (a Sept. 20th image) through E below, one 'topographic bump' is close to the region of possible Titan mountain ranges. SAR (last image) didn't quite cover the possible range imaged by VIMS. Image C actually shows an elongated cloud in the region.

[volcanopele]

What bump? Elba Facula? The bright spot in the middle of eastern Aztlan? That really isn't all THAT bright actually. More than likely it is probably pretty flat, though ISS saw so channels toward the edge of Elba. They are certainly not bright like the streaks seen by ISS and VIMS to the south east (my bet is still that those streaks are actually fresh fractures, not mountains, but we shall see

[ngunn]

What a beauty!

http://saturn.jpl.nasa.gov/multimedia/imag...ails170165.html

[ugordan]

What a beauty!

Indeed! Looking forward to a calibrated product. In the meantime, a stack of a few frames and some enhancement:

[Juramike]

It's really subtle, but I tried to enhance two effects I've suspected from an earlier image.

* a brighter ring extending inwards a few hundred km around the large mare. (lake effect fog or frost condensing out and bringing down bright schizzle deposits?)
* that north temperate black stain is much darker than it should be (compare to equatorial zone at same distance from limb).

I inverted ugordan's image and enhanced contrast. So the bright ring looks dark, and the black stain is white.


(The calibrated product will be very interesting...but this is really neat to think about for now.)

-Mike

[ngunn]

Mike, I'm sure we've discussed ISS-bright rings around lakes before. Was it Ontario Lacus? I can't recall if any consensus was reached back then.

Regarding the 'stain', I think I know which area you mean but I'm not absolutely sure. Looking at the Titan map I don't see any dark patches exceptionally far north from the latitude range occupied by 'sand sea' areas generally - nothing sticks out in the temperate zone (other than those spectacular long 'rivers' that I have privately named Volga, Ob, Yenisei, and Lena).

Attached thumbnail(s)

 

[Juramike]

The Ontario Lacus bright line seems to be a "bathtub ring" that is possibly the foreshore area of the lake. IIRC, (I'd have to dig into the Barnes et al VIMS article) it had different spectral characteristics. Many of the northern lakes seem to have a similar RADAR-bright ring. (Which I fondly refer to as "crusty crud" - I picture the Titan equivalent of the salt formations at Devils Golfcourse, Death Valley [image here]). Also IIRC, most of these crusty zones seem to be pretty well defined, so you could imagine it's outer boundary being the high-fluid mark.

The bright region around this big lake seems much more diffuse at the outer zones. And also seems not to follow the shoreline (topography) so tightly. I think this might be something different.

I'll try to make a better contrast-enhanced image.

-Mike

[ngunn]

I think I see what you mean - it shows up too on the Npolar map I've just edited into my last post. It seems brightest and most extensive on the east side of the lake, which would make sense if it is weather-related. But then we're talking about a huge region. I note also that the brighter area still has albedo variations within it, suggesting that if the brightening is due to a surface covering it's not very thick or continuous.

[Juramike]

(I had fun with this.)

Here is an inverted, contrast-enhanced and pschycedelicopseudocolorized version of Ugordan's Titan image:


And a graphic showing the Ugordan-processed image side-by-side with the 'Electric Titan' version indicating putative bright diffuse ring (yellow arrow) and the putative darker north temperate darker stain (purple arrow) with the electric. Both features are really subtle (I'm still learning this whole contrast-enhancement thing), but someone else might be able to do a better job.


-Mike

[ugordan]

I wouldn't be over-interpreting that image if I were you. It's a quick enhancement with high pass filtering that could have caused brightening around dark edges.

[Juramike]

Good point. I'd also add that atmospheric effects could be a major factor. (If there is high methane humidity/fog/haze other funky effects around the lake, what will this do?)

Similar trick (no contrast enhancement) done with PIA08399 (October 2007 Titan Map) crop of the big northern sea area. I assume this is calibrated - but not corrected for Titan's atmosphere.
(Color levels selected to best show contrast):



-Mike

[ngunn]

Ok, that 'dark stain' is at about 25 degrees N. Plenty of other dunefields at that latitude - what's special about this one?

[lyford]

This thread is starting to look like the end sequence of 2001!

Not that that's a bad thing.....

[Juramike]

Ok, that 'dark stain' is at about 25 degrees N. Plenty of other dunefields at that latitude - what's special about this one?

"It just seems funky"

To my eyes, it just appears darker than most of the other other mid-latitude dark zones. It also streaks upward to the NE in the direction you'd expect the prevaing wind vector to go.

Most of the mid-latitude dune fields have a reasonably well defined border (altough deeply incised) on the Eastern side. This one seems much more diffuse.
Compare it's aspect with the dune/temperate region area in NE Shangri-La.
Then compare with the diffuse dark pattern near Omacatl Macula or (better) Elpis Macula.

To me, (and I could be way wrong) the 'dark stain at [25N,280W]' looks like dark was deposited onto bright, rather than bright deposited onto dark.

In other areas, the temperate zone bright dark boundary is distinct, but fades in contrast going away from the Equator. To me that implies that the dunes sands are less mobile than the temperate/polar deposition.

In my model, atmospheric deposition only occurs where condensation happens "somewhere" in the atmospheric column. The equatorial zones are dry, no condensation, no deposition, bright-dark contrast maintained. The temperate zones have condensation happening at some level in the atmospheric column, condensation agglomerates organic fallout, deposition occurs (maybe as dry organic flakes), and the bright/dark contrast gradient is obscured, or faded.

So while the dark brown dune sands are mobile on a reasonable geologic timescale, the organic deposition occurs faster, obscuring the dune shoreline in the temperate regions. At least this scenario fits the ISS and RADAR observations (and the crater distribution, too).

The exceptions to this are Elpis Macula, Omacatl Macula, that dark stain in S Senkyo, and (maybe) this 'dark stain at [25N,280W]'.

-Mike

[ngunn]

Thanks for taking the trouble to explain that Mike. I sometimes lose track of the chain of reasoning that underlies your identification of something as anomalous! I wonder if there are any better resolution images of that area planned.

[ugordan]

October 11 very low phase view with all frames stacked:



The brighter part at the north might be a cloud or it might be a processing artifact. I'm inclined to think it's the former.

[Decepticon]

WOW! Good stuff!

What programs did you use to stack it?

[ugordan]

Just Photoshop.

[ngunn]

Clouds again today, I think, but I'll wait for Gordan.

I never expected sich a Titan bonanza these last few weeks. I'd resigned myself to a long lean time between Titan flybys - how wrong I was!

[ugordan]

Your wish is my command... October 15 sequence:



Clouds and a hint of Hotei Arcus at the limb to the left.

[titanicrivers]

[quote name='ugordan' date='Oct 16 2008, 05:28 AM' post='128779']
Your wish is my command... October 15 sequence:

Here's another sequence from the October 14th Titan images. In this animated view Cassini imaging filters and Titan's North Polar (NP) atmospheric phenomena are highlighted.

[ngunn]

Could it be that the methane clouds appear over areas from which the polar hood has just retreated? This could explain a (temporary?) longitude bias without any relation to surface features. We don't see a polar hood shadow on the surface, but maybe that's because the wavelengths we're observing the surface in are not typical of the whole spectrum. It would be the integrated flux that would do the evaporating.

[titanicrivers]

"We don't see a polar hood shadow on the surface, but maybe that's because the wavelengths we're observing the surface in are not typical of the whole spectrum. It would be the integrated flux that would do the evaporating."

I wonder if ISS doesn't see topographic or atmospheric shading on Titan due to the higher atmospheric scattering at 938 nm, the wavelength ISS uses to see the surface.

[ngunn]

Another nice global view of Titan today. Staring hard I can just make Kraken Mare appear near the limb at the 2 o'clock position, but then I can make it appear in your average patch of dirty wallpaper. Gordan-o-vision should settle the matter.

[ugordan]

I don't see it. It's too far on the limb to see. Mind you, this is pretty dodgy processing so someone else might be able to pull out more details.

[ngunn]

I agree. There is a suggestive darker patch on the limb at the right end of that bright streak in your image but no unambiguous shoreline shapes. Probably too oblique a view as you say. (Or maybe it's partly covered by clouds - as we keep watching we should see that happen eventually.)

[volcanopele]

Yeah, that's Kraken Mare.

[ngunn]

Thanks for the confirmation.

The land may vary more;
But whatever the truth may be -
The liquid comes ashore,
And the people look at the sea.

[ngunn]

A question:

Why would a lake be (marginally) visible that close to the limb when dark dune areas appear not to be? Thinking of the dunes as matt black and the lake as shiny black I'd expect the former to be more, not less, visible in that lighting geometry. Indeed it's surprising that anything's visible that close to the limb unless it's in some way affecting the apparent brightness of the haze above it.

[volcanopele]

Maybe they don't show up as well in Ugordan's rendition, but yes, dark equatorial terrain can often be seen right up to the "limb". The contrast and resolution is well...quite poor out that far, but you can make them out. In this image, we see a dark blog...thing about where Kraken Mare should be, but we certainly can't make out anything beyond that.

[ngunn]

Aah, right. But I'm still left wondering how a lake looking dark when right on the limb fits with the idea of specular reflection from a liquid surface. Looking over calm water on Earth you notice that out near the horizon it pretty much matches the sky.

[ngunn]

Following the same line of thought - it might be interesting to use the polarising filters when taking oblique shots of Kraken Mare. Are there any plans to try this (or has it been done already)?

[ngunn]

Aha - at last I've found a picture of mudflats with no birds! And this one happens to illustrate perfectly what I'm talking about here. It comes from this article: http://en.wikipedia.org/wiki/Brewster_angle

Attached thumbnail(s)

 

[ngunn]

Just to continue this little conversation with myself here's another picture comparison. It's two views out of my lab window taken about an hour ago under a completely overcast sky. The only difference is the orientation of the polaroid filter.

Attached thumbnail(s)