Atmospheric Chemistry of Titan Options

[Juramike]

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.

[Juramike]

A recent DPS abstract discusses some possibilities for Titan chemistry:

Horst et al. DPS Meeting 42 (2010) Abstract 36.20 "Formation Of Amino Acids And Nucleotide Bases In A Titan Atmosphere Simulation Experiment".
Direct link to abstract here.

One of the elements missing from all the above reactions is oxygen. There is not that much of it freely available in Titan's atmosphere. It is either in the form of H2O, from icy meteor infall, or from CO, or CO2. The 1 Gyr surface flux for CO2 varies between 10-100 cm for CO2 (high value in the Wilson and Atreya model), while the H2O surface flux (from meteors) is between 10 cm and lower (high value in the Raulin 1989 model). [A big Menrva crater splat may have caused actual water rain on Titan for a brief period according to an abstract a few years ago.]

The authors simulated Titan atmospheric conditions using N2, CH4, and CO2 and used a plasma discharge and generated molecules that incorporated oxygen. The abstract states that the following compounds were detected by GCMS (I'm assuming a direct injection of sample without a laboratory hydrolysis step before analysis.):
Amino acids glycine and alanine (presumably both enantiomers) were detected (but not H2NCH2CH2COOH?).
Also detected were the pyrimidine heterocycles cytosine, uracil, and thymine (but not orotic acid?)
As well as the fused heterocyclic imidazo-pyrimidine adenine (but not guanine?)

A slightly hyberbolic space.com article is here.

The key questions to relate this work are:
What was the overall yield of these compounds? Are we talking tiny trace amounts or significant geologically relevant surface deposits?
How doest this fit into the atmospheric models? Are these major pathways or minor chemical pathways?
How well does the PAMPRE experiment simulate Titan atmospheric tholins? (although PAMPRE is probably the best game in town for tholin simulation experiments)
How well does the simulated atmosphere reflect conditions in the upper atmosphere of Titan? At the critical formation zone? (Where is that for these pathways?)
And from a chemistry point of view, what are the electronic step-by-step mechanisms that make these?