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Titan Review article
rlorenz
post Dec 14 2007, 05:02 PM
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This just out. Not earth-shattering, but colorful - maybe handy as an up-to-date
Titan intro

http://www.jhuapl.edu/techdigest/td2702/lorenz.pdf
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Webscientist
post Dec 16 2007, 08:12 PM
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I bought in 2004 "Lifting Titan's Veil".It's of course the reference for Titan and I will reread it very soon to compare with what we know now ( presented in Titan revealed).

I'm fascinated by the radar images of the lakes in your Titan review.Unfortunately, the radar images don't give any indication on the appearance of the liquid.Does it appear dark, orange, blue... from a human eye?

Some dark and uniform patches located on the "white snow" of Iapetus made me think they were pools of hydrocarbons, similar to what we might find on Titan. Do you think that the idea is relevant?
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rlorenz
post Dec 17 2007, 01:37 PM
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QUOTE (Webscientist @ Dec 16 2007, 03:12 PM) *
I'm fascinated by the radar images of the lakes in your Titan review.Unfortunately, the radar images don't give any indication on the appearance of the liquid.Does it appear dark, orange, blue... from a human eye?

Some dark and uniform patches located on the "white snow" of Iapetus made me think they were pools of hydrocarbons, similar to what we might find on Titan. Do you think that the idea is relevant?


Lakes - get asked this a lot. Dunno. Probably like one of those 'Random_City at night' postcards - black.
Since the lakes are at the poles, its often nighttime. Sun and saturnshine is always low on the horizon, never
high in the sky, and only red light filters down to the ground. If you brought your own white light with you,
depends. Pure methane would look blueish - like Neptune - because of the methane absorptions in red. But
if there is a lot of reddish tholin suspended in it, maybe brownish (wine-dark sea?). So mostly black

White snow - even stuff like benzene (for example) at liquid nitrogen temperatures is white. I think
maybe anthracene is yellow (maybe Juramike can explain how things get dark/colored?). Soot of course is
black. I don't think we can rule out any of these of Titan (or Iapetus, for that matter..)
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Juramike
post Dec 17 2007, 08:34 PM
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QUOTE (rlorenz @ Dec 17 2007, 08:37 AM) *
White snow - even stuff like benzene (for example) at liquid nitrogen temperatures is white. I think
maybe anthracene is yellow (maybe Juramike can explain how things get dark/colored?).


Sure - I'll take a stab at it.

For organic molecules, things with molecular pi-orbital systems will absorb UV light. The electrons in the pi-systems get pushed up to an excited state. The UV photon goes in and excites the pi-cloud, then goes zipping off in another direction. Other photons just pass right through. Net result: UV gets absorbed.

The more extended and conjugated the pi-system, the lower the energy UV photons that can get absorbed.

Benzene has a UV peak absorbance at 210 nm. It looks white to our eyes, but is really absorbing some UV light. Put a bit of benzene on a phosphorescent silica background, and hit it with a UV light at 210 nm, and you'll see the black spot where the light didn't get through to the phosphorescent background. (At 254 nm the absorbance is kinda weak.)

(Chemists use this trick every day when monitoring reactions by TLC (thin layer chromatography). The bulk of compounds synthesized have extended aromatic or heteroaromatic rings. When there's no UV absorbance, like in aliphatic molecules, then chemists have to "do the dip" in order to stain the TLC using a reactive stain. [Still other chemists inject reaction crudes directly into the LCMS and clog up the instrument for everybody esle - these are bad chemists])

The more extended the pi-system, the lower the energy gap between the occupied and unoccupied pi-orbitals. Fusing aromatic rings together, or sticking certain functional groups in conjugation with the aromatic pi-system, all cause a shift to longer wavelengths. (Carboxyl, alkene, oxy, thio, halo - stuff like that), So things like napthyl, and anthracene (more and more benzenes in a line) make the maximum aborbance longer.

If you shift the UV absorbance into longer wavelengths, eventually you start absorbing in the visible spectrum. Remove blue light, and things look more yellow.

So the more extended the pi-system in a molecule, the yellower it looks.

Aside from the wavelength shift, there is also the effect of changing the extinction coefficient with certain functional groups, this can really amplify the absorbance exponentially. Check out the bathochromic shift (longer wavelength) and extinction coefficient jump for anthracene:

Benzene - lamba max = 255 nm (extinction coeff = 230) [much bigger absorbance hump near 210]
Naphthalene - lambda max = 314 (extinction coeff = 250)
Anthracene - lambda max = 380 (extinction coeff = 9000)

[In my advisor's group in graduate school, there was a guy in the next lab making large molecules resembling C60. As the aromatic system got larger, the compounds went from yellow, to an intense brick red. The guy's name was Rudiger Faust, and I strongly recommend his book "World Records in Chemistry" as a gift for anyone with even a slight hint of chem nerd in them.]

It does NOT take very much polymeric aromatic impurity to make things look highly colored. (Extreme case being black).

Most reactions always give a little black or highly colored aromatic goo that needs to be purified away. In my experience most reaction mixtures or slightly impure products (when things go good) always seem yellow. It's a rare and special day when someone gets a blue or green color in their reaction or product. (And we usually stand around and go "Pretty!")

Titan's surface and lakes are most likely highly colored. (Remember that black is a color).

-Mike


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Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Posts in this topic
- rlorenz   Titan Review article   Dec 14 2007, 05:02 PM
- - ugordan   QUOTE "Figure 1. A false-color composite of C...   Dec 14 2007, 05:13 PM
- - volcanopele   Well, I guess the secret is out. The ISS camera i...   Dec 14 2007, 05:42 PM
- - djellison   I assume the D is for Danger? Doug   Dec 14 2007, 06:02 PM
- - remcook   Yeah that Space Station also makes its appearance ...   Dec 14 2007, 06:07 PM
- - rlorenz   Hmm. So nice of you all to speak in such glowing t...   Dec 16 2007, 03:57 PM
|- - ngunn   Great article, thanks for sharing it here. In advo...   Dec 17 2007, 10:06 AM
|- - rlorenz   QUOTE (ngunn @ Dec 17 2007, 05:06 AM) Gre...   Dec 17 2007, 01:43 PM
|- - ngunn   QUOTE (rlorenz @ Dec 17 2007, 01:43 PM) ...   Dec 17 2007, 03:19 PM
|- - dburt   QUOTE (ngunn @ Dec 17 2007, 08:19 AM) How...   Dec 17 2007, 08:04 PM
- - djellison   Hand on heart - I've been keeping it ready for...   Dec 16 2007, 04:29 PM
- - Mongo   You know that we're just teasing. I personall...   Dec 16 2007, 04:30 PM
- - Floyd   Ralph, I really enjoyed the article--keep up the e...   Dec 16 2007, 05:21 PM
- - nprev   Great article, Ralph; certainly a call to arms for...   Dec 16 2007, 06:45 PM
- - Rob Pinnegar   Nice article. I picked up a few things from it tha...   Dec 16 2007, 06:54 PM
- - Webscientist   I bought in 2004 "Lifting Titan's Veil...   Dec 16 2007, 08:12 PM
|- - rlorenz   QUOTE (Webscientist @ Dec 16 2007, 03:12 ...   Dec 17 2007, 01:37 PM
|- - vjkane   QUOTE (rlorenz @ Dec 17 2007, 01:37 PM) P...   Dec 17 2007, 04:53 PM
||- - Mongo   QUOTE (vjkane @ Dec 17 2007, 04:53 PM) In...   Dec 17 2007, 06:46 PM
|||- - rlorenz   (we identified the same 5 terrain types as possibl...   Dec 18 2007, 12:22 AM
|||- - Mongo   QUOTE (rlorenz @ Dec 18 2007, 12:22 AM) (...   Dec 18 2007, 12:58 AM
|||- - rlorenz   QUOTE (Mongo @ Dec 17 2007, 07:58 PM) ......   Dec 18 2007, 01:59 PM
||||- - dvandorn   QUOTE (rlorenz @ Dec 18 2007, 07:59 AM) Y...   Dec 18 2007, 06:31 PM
|||||- - rlorenz   QUOTE (dvandorn @ Dec 18 2007, 01:31 PM) ...   Dec 18 2007, 08:16 PM
|||||- - dvandorn   QUOTE (rlorenz @ Dec 18 2007, 02:16 PM) A...   Dec 18 2007, 08:42 PM
||||- - NMRguy   QUOTE (rlorenz @ Dec 18 2007, 02:59 PM) O...   Dec 19 2007, 01:14 PM
||||- - rlorenz   QUOTE (NMRguy @ Dec 19 2007, 08:14 AM) So...   Dec 19 2007, 02:35 PM
||||- - ngunn   QUOTE (rlorenz @ Dec 19 2007, 02:35 PM) A...   Dec 19 2007, 02:57 PM
||||- - JRehling   A purely equatorial orbit would preclude RADAR obe...   Dec 19 2007, 10:24 PM
|||- - vjkane   QUOTE (Mongo @ Dec 18 2007, 12:58 AM) The...   Dec 18 2007, 05:05 PM
|||- - Mongo   QUOTE (vjkane @ Dec 18 2007, 05:05 PM) So...   Dec 18 2007, 05:55 PM
||||- - vjkane   QUOTE (Mongo @ Dec 18 2007, 05:55 PM) So ...   Dec 18 2007, 07:42 PM
||||- - rlorenz   QUOTE (Mongo @ Dec 18 2007, 12:55 PM) So ...   Dec 18 2007, 08:13 PM
||||- - Mongo   QUOTE (rlorenz @ Dec 18 2007, 08:13 PM) Y...   Dec 18 2007, 08:59 PM
||||- - ngunn   QUOTE (rlorenz @ Dec 18 2007, 08:13 PM) Y...   Dec 18 2007, 10:24 PM
||||- - vjkane   QUOTE (rlorenz @ Dec 18 2007, 08:13 PM) Y...   Dec 18 2007, 11:58 PM
|||- - tty   QUOTE (vjkane @ Dec 18 2007, 06:05 PM) Le...   Dec 18 2007, 10:09 PM
||- - rlorenz   QUOTE (vjkane @ Dec 17 2007, 11:53 AM) In...   Dec 18 2007, 12:33 AM
|- - Juramike   QUOTE (rlorenz @ Dec 17 2007, 08:37 AM) W...   Dec 17 2007, 08:34 PM
|- - rlorenz   QUOTE (Juramike @ Dec 17 2007, 03:34 PM) ...   Dec 18 2007, 12:24 AM
|- - Juramike   QUOTE (rlorenz @ Dec 17 2007, 07:24 PM) ....   Dec 18 2007, 04:26 AM
- - JRehling   Great synopsis. The points regarding the diversity...   Dec 16 2007, 11:08 PM
- - Stu   Great intro to the wonders and mysteries of Titan,...   Dec 16 2007, 11:55 PM
- - scalbers   Or could we suggest elements of the Vega Venus mis...   Dec 17 2007, 07:30 PM
|- - vjkane   QUOTE (scalbers @ Dec 17 2007, 07:30 PM) ...   Dec 17 2007, 07:46 PM
- - nprev   ...Mike, you just freakin' amaze me sometimes....   Dec 17 2007, 08:58 PM
- - djellison   And bonus points if it involves anything on Youtub...   Dec 18 2007, 12:29 AM
- - ngunn   Fascinating, Mike. But you've got me wondering...   Dec 18 2007, 11:40 AM
- - NMRguy   QUOTE (rlorenz @ Dec 19 2007, 03:35 PM) W...   Dec 19 2007, 03:14 PM
- - ngunn   Spot on, as usual. But why is it that I find Titan...   Dec 19 2007, 10:38 PM
|- - vjkane   QUOTE (ngunn @ Dec 19 2007, 10:38 PM) Spo...   Dec 20 2007, 01:17 AM
|- - ugordan   QUOTE (vjkane @ Dec 20 2007, 02:17 AM) My...   Dec 20 2007, 08:34 AM
- - djellison   It's simple. The Enceladus plumes are indeed, ...   Dec 20 2007, 08:52 AM
- - belleraphon1   Nature is rarely simple. Too soon to declare Ence...   Dec 20 2007, 12:50 PM
- - Matt   Worldlets.....well put, I like it; I only wish I...   Dec 27 2007, 10:12 PM
|- - nprev   QUOTE (Matt @ Dec 27 2007, 02:12 PM) I kn...   Dec 27 2007, 10:41 PM
|- - belleraphon1   QUOTE (nprev @ Dec 27 2007, 05:41 PM) Tit...   Dec 28 2007, 02:40 PM
|- - vjkane   QUOTE (belleraphon1 @ Dec 28 2007, 02:40 ...   Dec 28 2007, 06:43 PM
|- - lyford   QUOTE (vjkane @ Dec 28 2007, 10:43 AM) I ...   Dec 28 2007, 08:39 PM
- - nprev   Well, I was less than clear (again) in what I mean...   Dec 28 2007, 03:31 PM
|- - ugordan   QUOTE (nprev @ Dec 28 2007, 04:31 PM) ......   Dec 28 2007, 04:12 PM
||- - belleraphon1   QUOTE (ugordan @ Dec 28 2007, 11:12 AM) W...   Dec 28 2007, 09:00 PM
|- - JRehling   I think the key question, which may come down more...   Dec 28 2007, 08:40 PM
|- - vjkane   John, as usual, nails the subject, at least as I s...   Dec 28 2007, 09:34 PM
- - nprev   The strategy I envision is sort of a "one-not...   Dec 28 2007, 05:28 PM
- - vjkane   QUOTE (nprev @ Dec 28 2007, 05:28 PM) The...   Dec 28 2007, 06:37 PM
- - nprev   QUOTE (vjkane @ Dec 28 2007, 10:37 AM) I ...   Dec 28 2007, 08:33 PM


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