Optical constants of Titan’s stratospheric aerosols in the 70–1500cm−1 spectral range constrained by Cassini/CIRS observations

Vinatier, S.; Rannou, P.; Anderson, C. M.; Bézard, Bruno; Kok, Remco de; Samuelson, R. E.

doi:10.1016/j.icarus.2012.02.009

Cited by 87 publications

(83 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In spite of the limited spectral resolution, the haze integrated opacity exhibits distinct spectral bands centred at 700, 750, 780, 1390, and 1450 cm −1 . Interestingly, similar spectral A89, page 6 of 9 features are also observed in Titan's stratosphere (Vinatier et al 2012) and will be discussed in Sect. 4.2.…”

Section: Retrieval Of Aerosol Opacity Profilessupporting

confidence: 57%

“…• N and at low latitudes, are shown as purple and blue lines (Vinatier et al 2012). compute synthetic spectra with a high confidence level. Instead, in order to evaluate these aliasing effects on the haze retrievals, we perform test retrievals assuming lower radiances (by 5, 10, or 15% depending on wavenumber) than the calibrated ones in the range 1440-1480 cm −1 .…”

Section: Retrieval Of Aerosol Opacity Profilesmentioning

confidence: 99%

See 1 more Smart Citation

Stratospheric benzene and hydrocarbon aerosols detected in Saturn’s auroral regions

Guerlet

Fouchet

Vinatier

et al. 2015

A&A

View full text Add to dashboard Cite

Context. Saturn's polar upper atmosphere exhibits significant auroral activity; however, its impact on stratospheric chemistry (i.e. the production of benzene and heavier hydrocarbons) and thermal structure remains poorly documented. Aims. We aim to bring new constraints on the benzene distribution in Saturn's stratosphere, to characterize polar aerosols (their vertical distribution, composition, thermal infrared optical properties), and to quantify the aerosols' radiative impact on the thermal structure. Methods. Infrared spectra acquired by the Composite Infrared Spectrometer (CIRS) on board Cassini in limb viewing geometry are analysed to derive benzene column abundances and aerosol opacity profiles over the 3 to 0.1 mbar pressure range. The spectral dependency of the haze opacity is assessed in the ranges 680-900 and 1360-1440 cm −1 . Then, a radiative climate model is used to compute equilibrium temperature profiles, with and without haze, given the haze properties derived from CIRS measurements. Results. On Saturn's auroral region (80• S), benzene is found to be slightly enhanced compared to its equatorial and mid-latitude values. This contrasts with the Moses & Greathouse (2005, J. Geophys. Res., 110, 9007) photochemical model, which predicts a benzene abundance 50 times lower at 80• S than at the equator. This advocates for the inclusion of ion-related reactions in Saturn's chemical models. The polar stratosphere is also enriched in aerosols, with spectral signatures consistent with vibration modes assigned to aromatic and aliphatic hydrocarbons, and presenting similarities with the signatures observed in Titan's stratosphere. The aerosol mass loading at 80• S is estimated to be 1−4 × 10 −5 g cm −2 , an order of magnitude less than on Jupiter, which is consistent with the order of magnitude weaker auroral power at Saturn. We estimate that this polar haze warms the middle stratosphere by 6 K in summer and cools the upper stratosphere by 5 K in winter. Hence, aerosols linked with auroral activity can partly account for the warm polar hood observed in Saturn's summer stratosphere.

show abstract

Section: Retrieval Of Aerosol Opacity Profilessupporting

confidence: 57%

Section: Retrieval Of Aerosol Opacity Profilesmentioning

confidence: 99%

Stratospheric benzene and hydrocarbon aerosols detected in Saturn’s auroral regions

Guerlet

Fouchet

Vinatier

et al. 2015

A&A

View full text Add to dashboard Cite

show abstract

“…We therefore first derive the C 2 H 2 abundance that fits the Q-branch and then adjust the fit in the wings of the band to infer the other mixing ratios of the weaker species in the 620-780 cm −1 region. In order to model the continuum observed in the spectra, we have used the haze dependence as reported in Vinatier et al (2012a) giving the aerosol refractive index from CIRS spectra in the far-and mid-infrared regions near 15 • S and 20 • S, adjusted to match the level of radiance observed in between the molecular bands in our selections. Figure 1 shows an example of fits obtained in the FP3 (600-1000 cm −1 ) region and in the FP4 (1100-1500 cm −1 ) region.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, the changes in the circulation affect the distribution of aerosols (Vinatier et al 2012a), which in turn affect the thermal structure.…”

Section: Temperature Evolution Of Titan's Stratosphere During the Casmentioning

confidence: 99%

THERMAL AND CHEMICAL STRUCTURE VARIATIONS IN TITAN'S STRATOSPHERE DURING THECASSINIMISSION

Bampasidis

Coustenis

Achterberg

et al. 2012

ApJ

View full text Add to dashboard Cite

We have developed a line-by-line Atmospheric Radiative Transfer for Titan code that includes the most recent laboratory spectroscopic data and haze descriptions relative to Titan's stratosphere. We use this code to model Cassini Composite Infrared Spectrometer data taken during the numerous Titan flybys from 2006 to 2012 at surface-intercepting geometry in the 600-1500 cm −1 range for latitudes from 50 • S to 50 • N. We report variations in temperature and chemical composition in the stratosphere during the Cassini mission, before and after the Northern Spring Equinox (NSE). We find indication for a weakening of the temperature gradient with warming of the stratosphere and cooling of the lower mesosphere. In addition, we infer precise concentrations for the trace gases and their main isotopologues and find that the chemical composition in Titan's stratosphere varies significantly with latitude during the 6 years investigated here, with increased mixing ratios toward the northern latitudes. In particular, we monitor and quantify the amplitude of a maximum enhancement of several gases observed at northern latitudes up to 50 • N around mid-2009, at the time of the NSE. We find that this rise is followed by a rapid decrease in chemical inventory in 2010 probably due to a weakening north polar vortex with reduced lateral mixing across the vortex boundary.

show abstract

“…Since this pioneering study, it has been a spectroscopic challenge to confirm the actual composition of tholins in the atmosphere of Titan. The spectral features of the organic haze could not be properly extractable from Titan's infrared spectra without discretion, 4,5 which are complicated by strong mid-infrared thermal emissions and near-infrared absorptions of methane together with higher order hydrocarbons and nitriles. 6,7 Such discretion could be also taken in the near-infrared windows (1.08-1.11, 1.24-1.29, 2.0-2.1 µm), where Titan's atmosphere is relatively transparent 8 for unknown spectral influences of surface materials at the dawn of the Cassini mission.…”

Section: Introductionmentioning

confidence: 99%

Simulating the 3.4-Micron Feature of Titan's Haze

Kim

Ennis²,

Kim³

2013

Bulletin of the Korean Chemical Society

View full text Add to dashboard Cite

Optical constants of Titan’s stratospheric aerosols in the 70–1500cm−1 spectral range constrained by Cassini/CIRS observations

Cited by 87 publications

References 34 publications

Stratospheric benzene and hydrocarbon aerosols detected in Saturn’s auroral regions

Stratospheric benzene and hydrocarbon aerosols detected in Saturn’s auroral regions

THERMAL AND CHEMICAL STRUCTURE VARIATIONS IN TITAN'S STRATOSPHERE DURING THECASSINIMISSION

Simulating the 3.4-Micron Feature of Titan's Haze

Contact Info

Product

Resources

About