1. The two-micron spectral characteristics of the Titanian haze derived from Cassini/VIMS solar occultation spectra.
- Author
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Sim, Chae Kyung, Kim, Sang Joon, Courtin, Régis, Sohn, Mirim, and Lee, Dong-Hun
- Subjects
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SPECTRUM analysis , *SOLAR system , *OCCULTATIONS (Astronomy) , *ABSORPTION spectra , *HYDROCARBON analysis ,TITANIAN atmosphere - Abstract
Abstract: Vertically-resolved spectral characteristics of the Titanian haze in the 2-μm wavelength range were derived from solar occultation spectra measured by Cassini/VIMS on January 15, 2006. At the various altitudes probed by the solar occultation measurements, we reproduced the observed spectra using a radiative transfer program including absorption by CH4 ro-vibrational bands, collision-induced absorption by N2–N2 pairs, and H2–N2 dimers, as well as absorption and scattering by the haze particles. The retrieved optical depth spectra (or τ-spectra) for the haze show marked variations in the 2.1–2.8μm range, with peaks near 2.30 and 2.35μm, and the relative amplitude of these peaks changing with altitude. The gross spectral shape of the τ-spectra is found similar to the typical 2-μm absorption spectra of the alkane group of hydrocarbon (C n H2n+2) ices. The τ-spectra retrieved at 2μm and those previously retrieved at 3μm by Kim et al. (2011) are simultaneously reproduced by combinations of 2- and 3-μm absorbance spectra of alkane ices such as CH4, C2H6, C5H12, C6H14, with the addition of a nitrile ice, CH3CN. These combinations are neither unique nor limited and need more fine-tuning to fit the detailed features of the τ-spectra. There is a need for additional laboratory measurements of absorbance and indices of refraction for a wider variety of hydrocarbon and nitrile ices in the temperature range relevant to Titan. [Copyright &y& Elsevier]
- Published
- 2013
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