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 11 2010, 05:51 AM
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
Enter the mechanism
Over the next several graphics, I will detail the formation mechanism for many of the predicted Titan organic species. I will show the dominant pathway based on rate information found in Krasnopolsy, V.A. Icarus 201 (2009) 226-256. "A photochemical model of Titan's atmosphere and ionsosphere". doi: 10.1016/j/icarus.2008.12.038. Happily, this article is publicly available and can be downloaded freely here: http://pagesperso.lcp.u-psud.fr/pernot/ISS...snopolsky09.pdf I will be referencing the reaction Id number in the Krasnopolsky model (detailed in Tables 3-5) as well as the reaction rate. For the numbers, E9 is huge amounts, E8 is much, E7 is some, E6 is a little, E5 and below is “not so much”. The average altitude of greatest rate for the reaction is also shown. Remember that other reactions can be using up this intermediate as well, so this doesn’t necessarily mean that this is where the greatest production occurs. Generally the hardcore ion-neutral chemisty is way up high, while the gentle haze-surface-catalyzed radical association reactions occur down low. These schemes and mechanisms will start with the hydrocarbons first, and the nitriles next. This will be somewhat organized from most prevalent, to least prevalent. But key intermediates will be introduced before their products. So if you want to see how an intermediate got made, scroll upwards. The ultimate start point for everything will be UV photons + CH4 or UV photons + N2. First up is ethane (C2H6)... -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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