Titan´s July flyby cancelled?

[Spaceman Spiff]

My colour composites didn't look anything like what symaski62 linked to - each composite had very different final tones, I guess because the relative gains are all wrong.

About that ice-cap thing: yes, now I can see the changes, and that they are clouds... but isn't it great that I can be wrong already because these raw images are made available so quickly!?

Would people agree that these clouds look like they're convective - I mean like tropical storms over Earth's equator?

I'm still hoping that there'll be some lakes around. I'm thinking now that maybe these south polar clouds rain a bit of methane, and that flows down that riverlike feature into the dark area which is a partly empty basin, but might have some small sea or lake in it. It seems to have patches that are a slightly lighter tone like , so it can't all be open liquid. Even so, I just read the JPL press release, and it says that they reckon the dark areas mean pure water ice and bright areas mean hydrocarbons mixed in, and there's no way to tell whether the dark areas are high or low yet.

I'm wondering if Titan's evolved on a bit, such that as the sun grew brighter, it's previous oceans of methane/ethane have evaporated into smog. Maybe clouds and rain now only form at the poles. That would mean Titan is the cryogenic equivalent of a hot desert planet!

OK, any chances of a specular reflection? Can't wait for the radar to get working!

Spiff.

[selden]

Aren't specular reflections just that --reflections of the sky with the liquid's surface as the mirror? So if the sun's image is spread out by the atmosphere, the specular reflections aren't going to be sharp, either. If the sky's an even glow, the liquid surfaces will be reflecting an even glow in all directions.

[Matt McIrvin]

symaski62 - is that image is made by combining the three filters found here? Have you done something to the images? Because when I combine them they don't look anything like that (the green image is very deteriorated in quality)

Symaski62's image was not taken by the ISS camera at all, but by the VIMS instrument, the imaging spectrometer. The colors represent relative abundances of different materials-- as I understand it, the big revelation is that the dark-colored areas on Titan have less organics, not more; they are probably not hydrocarbon seas but rather regions of water ice, whereas the light-colored material is organic.

[Matt McIrvin]

There could still be specular radar reflections even if visible and near-infrared light are highly diffused. The radar will be used on future, closer flybys, right?

Those clouds look convective to me, too, like a piled-up monster storm of some sort.

The Huygens probe's landing ellipse is mostly in one of the dark areas-- I'm starting to worry that those might be the least interesting places on Titan (sort of like the Galileo Jupiter probe's bad targeting luck). Things may look different in a few months, though.

[t00fri]

symaski62 - is that image is made by combining the three filters found here? Have you done something to the images? Because when I combine them they don't look anything like that (the green image is very deteriorated in quality)

Symaski62's image was not taken by the ISS camera at all, but by the VIMS instrument, the imaging spectrometer. The colors represent relative abundances of different materials-- as I understand it, the big revelation is that the dark-colored areas on Titan have less organics, not more; they are probably not hydrocarbon seas but rather regions of water ice, whereas the light-colored material is organic.

Right, that indeed seems to be the big surprise. Very intriguing, indeed. But why does water ice have such a low albedo (in the IR)? I did not know that before. Is this perhaps related to the low surface temperature of -180 degs C?

I am puzzled...but I am probably not alone...

Bye Fridger

[granthutchison]

But why does water ice have such a low albedo (in the IR)?

It'll depend on what waveband you're using, but all those dangling OH groups on the surface of water ice are powerful IR absorbers because of their various vibrational modes.

Grant

[Evil Dr Ganymede]

Symaski62's image was not taken by the ISS camera at all, but by the VIMS instrument, the imaging spectrometer. The colors represent relative abundances of different materials-- as I understand it, the big revelation is that the dark-colored areas on Titan have less organics, not more; they are probably not hydrocarbon seas but rather regions of water ice, whereas the light-colored material is organic.

Y'know, I bet you that when we see through the clouds clearly we're going to see something that looks like Ganymede. I reckon those dark areas are like the bright terrain on Ganymede - Titan's about the same size, same density, and generally same composition as Ganymede (OK, plus methane and ammonia and whatever the heck maintaining the atmosphere). I half fancy that the faint dark lines we can see in some of the images are similar to the smaller bright terrain bands that wind across Ganymede's surface through the older dark terrain.

Oh, and large craters will be rare I think. I reckon it'd be more like Venus than Ganymede or Callisto.

I don't have a clue whether those interpretations are true on not, but I'm showing my cards down now .

[Guest]

So the dark areas are water ice and the bright areas are hydrocarbons?

So might Xanadu actually be an ocean rather than a continent as previously assumed?

[Matt McIrvin]

So the dark areas are water ice and the bright areas are hydrocarbons?

So might Xanadu actually be an ocean rather than a continent as previously assumed?

I could be wrong about this, but the bright areas don't look liquid to me-- too much structure there. I'm thinking with Evil Dr. Ganymede that the whole visible surface we're seeing is basically dirty ices, not so different from the other large satellites of Saturn, or from Ganymede; maybe reshaped by tectonics of some sort. The linear structures really do look a lot like the marks on Ganymede or Dione, except for brightness differences (but that could just be from the part of the spectrum that we're using to see them).

But the mystery of what sustains the atmosphere's composition remains, and the methane-ethane lakes could be too small-scale to see so far, or under those clouds at the south pole... I suppose that's always how it is: you imagination can run riot over the parts you can't see.

[Matt McIrvin]

The linear structures really do look a lot like the marks on Ganymede or Dione, except for brightness differences (but that could just be from the part of the spectrum that we're using to see them).

...Another data point: We also know that those dark marks looked slightly darker through the Voyager orange filter, though it took a lot of digital trickery to extract that.

[symaski62]

SPACECRAFT - Cassini Orbiter Instruments - ISS

http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-iss.cfm

[granthutchison]

Symaski62: Qu'est-que vous voulez dire avec ces images?

Grant

[symaski62]

Symaski62: Qu'est-que vous voulez dire avec ces images?

Grant

ISS NAC: couleur , (rouge, vert, bleu) et (noir, blanc
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ISS WAC: noir et blanc

[Evil Dr Ganymede]

(though I can read French, I can't figure out how write this post in French, sorry!)

Actually, if you read the caption to the r/g/b images, those "colour" images were not taken by the ISS, they were taken by the Visual Infrared Mapping Spectrometer.

And remember, all of these images are essentially "black and white" - they're all greyscale images. It's only when you combine them (or tint them) that you get "colour".

[granthutchison]

Symaski62:
Ces images ne sont pas vraiment <<en couleur>>. Elles repr?sentent trois longueurs d'onde dans le spectre infrarouge.

Grant