Titan at 3 microns: Newly identified spectral features and an improved analysis of haze opacity

Spectral characteristics of the Titanian haze at 1−5 micron fromCassini/VIMS solar occultation data

“…;Smith et al 1949). The type and structure of this band are the same as those of the C 2 H 6 band at 2.94 μm, which were previously established for an analysis of high-resolution (R ∼ 20 000) spectra of Titan (Seo et al 2009). This 2.94 μm band was simply shifted to 4.3 μm and assigned the appropriate band intensity (Pierson et al 1956); such a simple procedure may be justified for the analysis of low spectral resolution data such as the VIMS data.…”

“…In this work, we adopted such a k-distribution (Karkoschka & Tomasko 2010). For the synthetic spectra in the 2−3.8 μm interval, we adopted results from our previous works (Kim et al 2005;Seo et al 2009;Kim et al 2011;Sim et al 2013). In addition to weak absorption from CH 4 and its isotopes, absorption from minor species, such as C 2 H 2 , HCN, CO 2 , and CO is expected to occur between 3.8 and 5 μm (Baines et al 2006).…”

“…The radiative transfer code includes the radiative and collisional excitation and de-excitation of the above molecules, and the effects of anisotropic scattering (in the two-stream approximation) and absorption by haze particles. The haze optical depth (τ λ ) is treated as the only adjustable parameter -with some constraints based on the DISR Huygens probe investigation (Tomasko et al 2008) -to be determined by model comparison with the VIMS data, as previously described (Kim et al 2011;Sim et al 2013;Seo et al 2009). We also took into account the refractive attenuation of light from dense atmospheric layers at the lowest altitudes, as discussed previously by Bellucci et al (2009).…”

High-resolution 3-μm spectra of Jupiter: Latitudinal spectral variations influenced by molecules, clouds, and haze

“…Recent high-resolution 2.9-3.5-lm spectra of Saturn (J.H. Kim et al, 2006) and Titan (Geballe et al, 2003;Seo et al, 2009) have revealed lines of CH 4 , C 2 H 2 , C 2 H 6 in both objects, CH 3 D and HCN in Titan, and PH 3 in Saturn spectra and led to advances in understanding of the structures of the atmospheres of those objects from their tropospheres to their stratospheres, leading us to expect that similar observations of Jupiter would be fruitful. Surprisingly, high-resolution spectra of Jupiter in the same wavelength range have not been available, although Jupiter is brighter than Saturn and Titan.…”

“…In order to identify in detail the contributors to the observed spectra as well as to study the atmospheric structure, we update and modify a radiative transfer program, which has been firmly established during the Saturn and Titan spectral analyses (J.H. Kim et al, 2006;Geballe et al, 2003;Seo et al, 2009) and construct synthetic spectra, which include ro-vibrational line-by-line contributions of CH 4 , CH 3 D, 14 NH 3 , 15 NH 3 , C 2 H 2 , C 2 H 6 , HCN, and PH 3 . Comparisons of the observed and synthetic spectra allow us not only to test existing models but to present updated vertical mixing ratio distributions of these molecules, especially high-altitude mixing ratios for C 2 H 2 and C 2 H 6 , as well as updated 3-lm opacity distributions of clouds and haze particles.…”