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| Titel |
Anomalous emission at 3.28 μm in the Titan upper atmosphere |
| VerfasserIn |
B. M. Dinelli, A. Adriani, M. López-Puertas, M. L. Moriconi, M. García-Comas, A. Coradini, E. D'Aversa, G. Filacchione, F. Tosi |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022849
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| Zusammenfassung |
| Earliest Cassini VIMS limb observations of Titan taken in October 26th, 2004 show a strong
methane non-LTE limb emission at high atmospheric altitudes. During that pass at Titan,
VIMS vertical resolution was about 110 km and the analyzed spectral interval corresponds
to the methane emission band centered around 3.33 micron. A detailed analysis
of the radiances versus altitudes shows an anomalous emission above 900 km at
wavelengths close to the methane R branch (3.28 micron). The nature of such emission
is under investigation. Different spectral databases and codes have been used for
calculating the expected CH4 non-LTE limb emissions. The “anomalous” emission could
not be reproduced using all the known CH4 bands. Its spectral position hints at a
molecule containing C-H or C-N bonds. A lot of molecules and ions observed in
Titan’s atmosphere have been tested unsuccessfully. Benzene (C6H6), the phenyl
radical (C6H5) or other aromatic species, given their spectral features and modeled
abundances in the upper atmosphere, could be candidates for such emission. We
choose the observation on Oct. 26th, 2004 for its very good signal to noise ratio
and because of the favorable illumination (low phase angle) of the atmosphere as
seen from the Cassini spacecraft. Other observations also show the same feature. |
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