[X] My Assistant

[Stu]

With an hour or so to kill before heading out to work I thought I'd have a play about with the images of the "lakes". Having read that it might be possible to enhance these or future images to bring out more details - maybe even waves - I just started playing about with contrast and brightness, seeing what popped out... and just doing that shows detail and some features within the "lakes" which I'm interested in people's comments on.

Titan lake

Now, before anyone tells me off for my "playing about" and points out, rightly, that you can't just take these raw images and pull info out without a LOT of work, please bear in mind I KNOW all that, okay? I'm no Nix or Nirgal or Horton, and I'm not suggesting this means anything, I'm just curious what I might have seen. I know the features might just be imaging artefacts, but... oh, just take a look and see what you think. I'm just pushing the ball down the hill here, not making any claims. I would be interested to hear what others think tho.

Sticking my neck out here, to me it looks like the "drainage channel" on the lower right hand side actually continues into the "lake" for quite a way, maybe even flowing beneath an "island" of some sort. Other things look like they're in there too, but I'm just wondering if the "lake" is actually very shallow and we can see channels on its floor...

Features?

...but heck, what do I know...

[Guest_Richard Trigaux_*]

The electromagnetic properties of hydrocarbons (at ambient temp, but at low temp it must not be very different) are about 2-3 for epsilon zero, and 1 for mu zero. I don't remember the formula to derive the wave velocity in this, but it may be a square root, giving a velocity in the 200 000km/s, which is also the velocity in cables insulated with materials like polyethylene. This makes an optical refraction ration about that of special glass like crystal. This is not very high, and we can assume that, when the radar wave meets a methane-ethane surface, a fairly part of it penetrates into the liquid, provided that the surface is calm, with no waves, probably a common condition on Titan. (Eventually a patch appearing dark one day and clearer another time would be a tell tale evidence of waves, and thus of liquid). After, the radar wave can penetrate deeply into the liquid, which probably contains little particules to absorb it. If it contains, the patch will appear much darker. After, the reflection on the bottom gives an image of it, that the radar can get. We can imagine the result with a lagoon and no waves: features on the bottom are visible at depths of more than 10m. And methane is much more transparent to radar waves (similar bodies like polyethylene are used as insulators in high frequency cables, and even as wave guides).

So we can figure that methane lakes would appear as darker patches. But Huygens seemingly landed into one such patch, and it was not liquid. So it is difficult to infer that all dark patches are liquid.

Seeing the bottom of lakes is likely too. deep lakes should appear completely black.

About the geometric features on the image, they are very difficult to interpret. They more or less ressembgle features seen on earth wet polar regions, where, by some process, repeated frost and thaw create many circular lakes. But this interpretation don't hold much on Titan. This region indeed look like a swamp, and, as in certain Earth swamps, we observe many sub-circular features which could be mud diapirs.

[Bjorn Jonsson]

Interestingly, extreme processing in an attempt to reveal details within the dark areas ('lakes') reveals that they appear different:


This is the big lake previously discussed. Some details are visible, for example I'm sure the 'channel' extending from the lake's lower right and into its central area is a real feature. Compare this with the following:


This is the fairly big 'lake' in the upper left corner of the original T16 swath. Interestingly, no details are visible within this lake. It may also be of interest that this lake appears a bit darker than the big one in the unprocessed original image. From the discussion above this could mean it is deeper (if this is a lake), wetter/smoother/more muddy (if this is not a lake) or this could be a processing artifact and not a real difference.

These images were smoothed a bit with a median filter, then greatly sharpened and then smoothed a bit with a median filter.

Here's my version of the image. The vertical stripes, which are imaging artifacts, have been removed by using a Fourier transform.

I would be very interested in knowing which software you used to get rid of the stripes with a Fourier transform. The Cassini ISS images contain noise (stripes) which is hard to get rid of and annoying in some cases.

Finally I should note that I'm attaching these images in PNG format and not JPG. PNG files are sometimes smaller than decent/high quality JPG files for high-contrast, high-frequency scenes like these. Also they are losslessly compressed, unlike JPGs.