Atmospheric Chemistry of Titan |
Atmospheric Chemistry of Titan |
May 2 2010, 03:38 AM
Post
#1
|
||
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/
|
|
|
||
Jun 6 2010, 07:58 PM
Post
#2
|
|
Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
Article in press: Strobel, D.F. Icarus (2010) Article-in-press. "Molecular hydrogen in Titan's atmosphere: Implications of the measured tropospheric and thermospheric mole fractions." doi: 10.1016/j.icarus.2010.03.003
If I understood this correctly, the models for H2 flux don't match up to the observations. This paper attempts to "follow the hydrogen" and do some atomic accounting to see how well the hydrogen matches up to models. H2 is made by a lot of the atmospheric chemistry processes. (All those H. radicals and H2 on the back side of the equations.) Much of it escapes from Titan off the top of the atmosphere. But according to the author, an equivalent amount goes down and away onto Titan's surface. (6.6E27 H2 s-1 escape vs. 2.9E27 H2 s-1 down to surface and away : I'm assuming the units are actual molecules - thus 10600 moles of H2 escapes Titan every second.) One interesting possibility the authors raise is that the H2 is sucked up into surface (or subsurface) reactions with heavier organics that then regenerate ("crack") CH4. Even with this, the overall atmospheric escape of H2 still ensures that methane will eventually be converted to heavier organics. Key quote: "...either the observations are not consistent with each other or that our understanding of CH4 and H2 photochemistry is flawed and needs some revision." Since a lot of the molecular production rates for other species are bouncing around by orders of magnitude (I'll post a table soon) from one model to the next, it is not surprising that the hydrogen production rate is also not-so-well constrained. Titan chemistry is complicated. -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
|
|
|
Lo-Fi Version | Time is now: 26th September 2024 - 04:48 PM |
RULES AND GUIDELINES Please read the Forum Rules and Guidelines before posting. IMAGE COPYRIGHT |
OPINIONS AND MODERATION Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators. |
SUPPORT THE FORUM Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member. |