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.

[scalbers]

I saw a talk given at the AGU conference last week mentioning that far infra-red spectral observations suggest that the atmospheric hazes probably have different composition than the traditional Titan tholins. More lab work will be helpful in comparing various compositions to the observations. This is related to post #79 I believe. Here is the abstract...

ABSTRACT FINAL ID: P33F-0
TITLE: Spectral and vertical distribution properties of Titan’s particulates from thermal-IR CIRS data: Physical Implications
SESSION TYPE: Oral
SESSION TITLE: P33F. Titan: An Earth-Like World II
AUTHORS (FIRST NAME, LAST NAME): Carrie M Anderson1, Robert Samuelson2, 1, Sandrine Vinatier3
INSTITUTIONS (ALL): 1. Solar System Exploration Divis, NASA---GSFC, Greenbelt, MD, United States.
2. Astronomy, University of Maryland, College Park, MD, United States.
3. LESIA , Observatoire de Paris-Meudon, Meudon , France.
Title of Team:
ABSTRACT BODY: Analyses of far-IR spectra between 20 and 560 cm-1 (500 and 18 μm) recorded by the Cassini Composite Infrared Spectrometer (CIRS) yield the spectral dependence and the vertical distribution of Titan’s photochemical aerosol and stratospheric ice clouds. Below the stratopause (~300 km) the aerosol appears to be incompletely mixed for the following reasons: 1) the altitude dependence of the aerosol mass absorption coefficient is larger at higher altitudes than at lower altitudes, 2) the aerosol scale height varies with altitude, which implies some kind of layering effect, and 3) the aerosol abundance varies with latitude.

The spectral shape of the aerosol opacity appears to be independent in altitude and latitude below the stratopause, even though inhomogeneities in the abundance appear to be prevalent throughout this altitude region. This implies that aerosol chemistry is restricted to altitude regions above the stratopause, where pressures are less than ~0.1 mbar. The aerosol exhibits an extremely broad emission feature with a spectral peak at 140 cm-1 (71 μm), which is not evident in laboratory simulated Titan aerosols (tholin) that are created at pressures greater than 0.1 mbar.

A strong broad emission feature centered roughly around 160 cm-1 corresponds very closely to those found in nitrile ice spectra. This feature is pervasive throughout the region from high northern to high southern latitudes. The inference of nitrile ices is consistent with the highly restricted altitude ranges over which these features are observed, and appear to be dominated by HCN and HC3N. At low and moderate latitudes these clouds are observed to be located between 60 and 100 km, whereas at high northern latitudes during northern winter these clouds are observed at altitudes between 150 and 165 km. The ubiquitous nature of these nitrile ice clouds is inconsistent with a simple meridional circulation concept, suggesting that the true dynamical situation is more complex.



KEYWORDS: [6281] PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS / Titan, [5405] PLANETARY SCIENCES: SOLID SURFACE PLANETS / Atmospheres, [5422] PLANETARY SCIENCES: SOLID SURFACE PLANETS / Ices.
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SPONSOR NAME: Carrie Anderson

Additional Details
Previously Presented Material: Most of the material was published in Icarus 212, 762-778 in 2011.

Contact Details
CONTACT (NAME ONLY): Carrie Anderson
CONTACT (E-MAIL ONLY): carrie.m.anderson@nasa.gov