Atmospheric Chemistry of Titan |
Atmospheric Chemistry of Titan |
May 2 2010, 03:38 AM
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
Here is a "Benzene-O-Vision" graphic showing the amount of benzene and phenyl radicals at high altitudes on Titan. This is based on detections of benzene and phenyl radical (which recombined in the sample chamber to make benzene) using the INMS instrument during closest approach. The numbers are normalized to constant pressure altitude, roughly 1000 km.
The data was taken from Table 1 in: Vuitton et al, Journal of Geophysical Research 113 (2008) E05007. "Formation and distribution of benzene on Titan". doi: 10.1029/2007JE002997 [EDIT 5/24/10: Article freely available here] and overlaid on a map of Titan. The authors mentioned that the errors in these measurements are 20%. These detections are well above the detached haze layer. Most are at the same sun azimuth angle. (T23 observation had the lowest angle.) Assuming that the temporal difference is minimal (each dot is from a different flyby), there doesn't appear to be an obvious correlation with latitude. This graphic does show that benzene is present even waaaay up in the thermosphere and ionosphere. -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Jun 4 2010, 10:49 PM
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
The low temperatures at the surface and lower atmosphere (<100 km) will hinder most thermal reactions we would consider easy at terrestrial temperatures.
But up high, the high energy photons + the thicker atmosphere at high altitude with methane make for a lot of really high-energy exotic chemistry. The really fun stuff happens above 200 km altitude. There's a peak at about 300-400 km, and another peak about 800 km, as different processes have their preferred altitudes. So the fun stuff happens up high, then the products condense out around 130 km, then stays inert down to the surface. [Some of the fun intermediates could get trapped and embedded in haze particles that make it down to the surface. (I'm guessin' that is the crux of the Lunine et al. abstract). Even at low temperatures, a carbenium ion thrown in solution with some unsaturated compounds might do some reacting.] Aside from all this, one really important point is that photochemistry can occur near 0 K. So while ground-state (thermal) chemistry might be difficult at low temperatures, once you've photoexcited something, even at very low temperatures, you can do exciting (!) things. [Earths ozone layer protects us from these photons by absorbing the light and cycling through oxygen species.] So even in the cold haze decks of Titan, as long as UV can penetrate, it will do stuff. -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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