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volcanopele
post Aug 4 2010, 12:20 AM
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The post on Zal Patera is now online:

http://www.gishbartimes.org/2010/08/io-vol...f-week-zal.html

Along with a commentary about how Io doesn't smell that bad...

http://www.gishbartimes.org/2010/08/volcan...not-smelly.html


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nprev
post Aug 4 2010, 12:39 AM
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Good stuff, VP. You might also point out that nowhere in the Solar System smells even a millionth as bad as Titan probably does... laugh.gif


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ugordan
post Aug 4 2010, 12:48 AM
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If you're thinking about methane in particular, nope - odorless.

Io might not smell bad, but if I recall SO2 is pretty aggressive stuff to the nostrils. Stings just like large concentrations of CO2 do.


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nprev
post Aug 4 2010, 01:16 AM
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I was actually thinking of complex organics like mercaptans (sp?) & other such nasties.

Still, Io undoubtedly has a few traces of H2S here & there...that'll definitely get your attention!


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Juramike
post Aug 4 2010, 02:08 AM
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Here is a handy reference regarding elemental sulfur and planetary geology:
http://ntrs.nasa.gov/archive/nasa/casi.ntr..._1982025583.pdf

And of course, to keep the pure sulfur allotropes apart:
http://en.wikipedia.org/wiki/Allotropes_of_sulfur

(I've used S8 before, and it was stinky, but this may have been due to trace impurities generated during the reaction.)


In general, sulfur and thiol compounds do stink. Each has there own, uhhhh, particular characteristic aroma. The really high molecular weight ones don't volatilize. Naphthyl-thiol is stink free, but benzene thiol will stink quite nicely - enough to clear a lab.

Amines can also stink (fishy odor)

Pyridines also stink (dead seaweed odor, you get used to it, but it will cause impotence).

Acrylonitrile (a significant component on Titan) will bring tears to your eyes. It is a lachrymator.
(Yours truly evacuated a lab accidentally with the similar compound acrolein. It took me 3 hours to quit crying.)

Your best bang for your buck for smell factor comes with isocyanides and phosphines. Those are just plain vile.
They have a unique smell all to their own. It is hard to describe, but once you've smelled it, you'll respect it. Spills of those materials are enough to evacuate a building (they are also pretty toxic.)

But in general, smell is difficult to talk about on Io. Your nasal receptors detect things that have diffused to it, and absorbed onto the receptor itself (a pseudoaqueous environment). If you ever smelled Io directly, you'd be dead (no pressure). If you brought Io stuff back to Earth and put it in a lab, it would be able to react with ambient oxygen and water to generate trace compounds (such as volatile sulfides) that your nose would likely find offensive. The critical thing is that you would be need to expose Io stuff to a new aqueous and oxygen-rich environment in order to smell it.


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volcanopele
post Aug 4 2010, 02:26 AM
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The first link is a great little publication. Actually have an original hard copy of it smile.gif

Certainly my article pertaining particularly to the compounds that were found by Moullet et al., SO2, SO, and NaCl (and we can add S2/S8 to this discussion as well, though it wasn't part of their study). And of those molecules, none smell like rotten eggs, but at worst smell like burnt matches (not the best smell, but not horrendous either). But you have a good point, in order to smell anything on Io (or Titan or Mars), you would have to bring it into an alien environment, which could produce compounds like hydrogen sulfide, which does smell quite bad.

Anyways, the main point I wanted to get across with my article was the terrible re-reporting of the space.com article, focusing more on the line about how bad Io might smell, and less about the results of the paper the space.com article was reporting on. I can understand trying to connect these findings with a broad audience, but the approach taken by space.com and others was poor. For example, why not emphasize the discovery of sodium chloride in Io's atmosphere? "Gaseous table salt found in the atmosphere of Jupiter's Moon Io"? "Jupiter's moon sulfurous with a dash of salt"?


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brellis
post Aug 4 2010, 03:08 AM
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Is it possible for something to 'stink' at such low temperatures? Disclaimer: my freezer has occasionally emitted some god-awful emittances! huh.gif
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volcanopele
post Aug 19 2010, 11:18 AM
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Bjorn has touched on this earlier and has his own webpage on it, but I thought I would try my hand at creating a true color image of Io using Galileo imagery. I go into much more detail on my blog, but basically I used the ground-based spectra of Io to determine correction factors for combining Galileo violet and green filter images to synthesize an appropriate blue filter. Bjorn used the Voyager blue filter as a guide, whereas I tried to create something that was a little closer to the violet image but using the BL1 filter on Cassini as a guide. No images of Io in that filter are available, I just used the effective wavelength as something I felt was a best-case blue filter.

I post the image here, but I have the nice, pretty charts and graphs (yes, I have finally re-learned how to properly use Excel's chart mechanic, stupid Microsoft and their ribbon instead of a menu...)

http://www.gishbartimes.org/2010/08/exposi...rue-colors.html

Attached Image


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ugordan
post Aug 19 2010, 05:40 PM
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Nice experiment. You bring up a good point about the name of the Voyager "blue" filter, I would just point out that it's actually the "green" filter that's more orange than green, making many of the old Jupiter shots look greenish among other things.

Do you have that visible spectra in tabular form? I'd love to run that through my code to see what color it produces. I threw all your Io Galileo composites through my CIE XYZ linear interpolation code to see how it'd turn out a while back. Here's that same shot (assuming the filters sampled the discrete 665, 559 and 413 nm wavelengths):

Attached Image


Having the actual surface spectra might make for a more accurate interpolation, especially that knee at ~520 nm. Looks like the visible spectrum could be well approximated with two or three linear segments.

While playing around with Phoenix surface images, I found out that simple channel mixing to get average wavelength works pretty good for most cases, but just doesn't cut it for objects with strong spectral slopes (and hence strong colors) - surface, calibration chips etc. It was only once I gave up on that and interpolated the spectra through 3 (or more) filters and integrated that through the tristimulus values did I get results really close to Mark Lemmon's surface shots. One thing is that a strong red hue translates into a darkening of the blue channel in sRGB gamut which is something just not accounted for with channel mixing.


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volcanopele
post Aug 19 2010, 08:26 PM
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Would correcting my images using your code be affected by the fact that I've already corrected for the sun's varying flux at different wavelengths? The pixel values are derived from the calibrated I/F values, with each filter being stretched to 8-bit 0 (black sky) to 255 (brightest 'valid' point in the red filter image).

The visual spectra are located at http://web.archive.org/web/20031209213618/....edu/index.html . The data is under Images and Spectra, and there are tables for the leading and trailing hemisphere.


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4th rock from th...
post Aug 19 2010, 09:24 PM
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Nice results. Both of your processed images are consistent, with the Ugordan version having a more natural gamma (in my subjective opinion).


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machi
post Aug 19 2010, 09:44 PM
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Volcanopele:
I like your image. It's unbelievable clarified. Ugordan's version looks too much bright on LCD monitor of my net computer, so I must take a second look on my old CRT monitor, which has much better display.


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ugordan
post Aug 19 2010, 10:22 PM
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QUOTE (volcanopele @ Aug 19 2010, 10:26 PM) *
Would correcting my images using your code be affected by the fact that I've already corrected for the sun's varying flux at different wavelengths?

No, in fact it assumes I/F data. It needs to be I/F if you want icy bodies turning out white in sRGB which is the way I prefer.

QUOTE
The visual spectra are located at http://web.archive.org/web/20031209213618/....edu/index.html . The data is under Images and Spectra, and there are tables for the leading and trailing hemisphere.

Thanks. Here's what that gives for Io's leading hemisphere. Left is gamma correct, right is everyone's preferred look. I make no claims on accuracy or correctness of my code.
Attached Image
FWIW, the other 3 moons' hue looks similarly yellowish with Europa being most pale yellow (leading hemisphere at least). I would also add that since these are very low phase spectra by nature (ground obs), the colors will always look subtler than typical for spacecraft which can get much higher phase imagery. That can be seen in that Galileo mosaic as well - compare to the other, higher phase version of your composite I posted in the Galileo Imagery thread.


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volcanopele
post Aug 19 2010, 10:46 PM
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Well, I'm willing to give any correction factors you recommend based on your calculations.


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ugordan
post Aug 19 2010, 11:27 PM
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You prefer the contrast of a non gamma-correct display so I don't know if there's an easy way out. Take for example the color in the palette at right above. You can create that disk-averaged hue out of your composite by mixing R=0.9R+0.1B and B=0.65B+0.35G. It's completely unscientific and this does preserve grey areas as grey, but as you can see the disc as a whole will appear overly green. However, if you were to average the entire visible surface and brighten the resulting color you'd see it matches the above palette color. That's the side effect of greatly stretched contrast and color in that representation - many greatly different colors which when averaged still give a "correct" hue. There likely are other such combinations.

If you want to make it visually appear at least close to that yellow color, I think you'll have to actually change level balance at which point grey terrain will no longer remain grey, but you will retain the high contrast representation of surface features.


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