Titan’s surface and atmosphere from Cassini/VIMS data with updated methane opacity

Hirtzig, M.; Coustenis, A.; Drossart, P.; Bézard, Bruno; Lellouch, E.; Bérgh, C. de; Rodríguez, S.; Campargue, A.; Boudon, Vincent; Schmitt, Bernard

doi:10.1016/j.icarus.2013.05.033

Cited by 101 publications

(140 citation statements)

References 78 publications

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“…These effects vary in space and time. Radiative transfer models attempt to account for known atmospheric constituents on Titan's measured reflectance, yet many spectral features remain partly or wholly unexplained (Griffith et al, 2003;Coustenis et al, 2006;Hirtzig et al, 2013). For these reasons, and despite the http://dx.doi.org/10.1016/j.icarus.2014.08.045 0019-1035/Ó 2014 Elsevier Inc. All rights reserved.…”

Section: Introductionmentioning

confidence: 99%

“…Griffith et al (2012) applied a radiative transfer model based on the doubling and adding method, with constraints on gas and aerosol opacities in the wavelength range 0.85-1.6 lm derived from the Huygens probe's near-IR spectrometer. However, the derived surface albedos are poorly constrained at longer wavelengths, and are in apparent disagreement with models using improved methane line parameters (Hirtzig et al, 2013). Properly accounting for atmospheric effects in deriving Titan's surface reflectance in the near-infrared has thus proven challenging, given both the inherent complexity of rigorous radiative transfer models, and the lack of data on individual line profiles for the array of molecules present in Titan's atmosphere under realistic thermodynamic conditions (McCord et al, 2006.…”

Section: Introductionmentioning

confidence: 99%

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Titan’s surface composition and atmospheric transmission with solar occultation measurements by Cassini VIMS

Hayne

McCord

Sotin

2014

Icarus

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Titan’s surface composition and atmospheric transmission with solar occultation measurements by Cassini VIMS

Hayne

McCord

Sotin

2014

Icarus

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“…This is the case for relatively transparent spectral windows, such as the methane windows in Titan between 1.3 and 5 µm (e.g. Hirtzig et al 2013) or nearinfrared windows observed on Venus' night side between 1 and 2.3 µm (e.g. Fedorova et al 2015).…”

Section: Discussionmentioning

confidence: 99%

Toward the Analysis of JWST Exoplanet Spectra: Identifying Troublesome Model Parameters

Baudino

Mollière

Venot

et al. 2017

ApJ

120

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Given the forthcoming launch of the James Webb Space Telescope (JWST) which will allow observing exoplanet atmospheres with unprecedented signal-over-noise ratio, spectral coverage and spatial resolution, the uncertainties in the atmosphere modelling used to interpret the data need to be assessed. As the first step, we compare three independent 1D radiative-convective models: ATMO, Exo-REM and petitCODE. We identify differences in physical and chemical processes taken into account thanks to a benchmark protocol we developed. We study the impact of these differences on the analysis of observable spectra. We show the importance of selecting carefully relevant molecular linelists to compute the atmospheric opacity. Indeed, differences between spectra calculated with Hitran and ExoMol exceed the expected uncertainties of future JWST observations. We also show the limitation in the precision of the models due to uncertainties on alkali and molecule lineshape, which induce spectral effects also larger than the expected JWST uncertainties. We compare two chemical models, Exo-REM and Venot Chemical Code, which do not lead to significant differences in the emission or transmission spectra. We discuss the observational consequences of using equilibrium or out-of-equilibrium chemistry and the major impact of phosphine, detectable with the JWST.Each of the models has benefited from the benchmarking activity and has been updated. The protocol developed in this paper and the online results can constitute a test case for other models.

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“…In order to evaluate whether solid C 2 H 2 at the surface of Titan contributes significantly to the 1.55 μm spectral feature of VIMS spectra, we used a plane-parallel radiative transfer (RT) model that takes into account the absorptions from atmospheric major gases, including atmospheric C 2 H 2 and the scattering by haze particles in a comprehensive scheme (adapted from Hirtzig et al 2013).…”

Section: Proof Of Concept For the Detectability Of C 2 H 2 At The Surmentioning

confidence: 99%

“…Those calculations were performed with the nominal model for the atmospheric gases (validated in previous studies; de Bergh et al 2012;Hirtzig et al 2013) and aerosols with zero incidence and emergence angles. The atmospheric gases and aerosol content have been fixed to the reference values measured by the Descent Imager-Spectral Radiometer (DISR) above the Huygens landing site (Tomasko et al 2008).…”

Section: Proof Of Concept For the Detectability Of C 2 H 2 At The Surmentioning

confidence: 99%

Acetylene on Titan’s Surface

Singh

McCord

Combe

et al. 2016

ApJ

Self Cite

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Titan's atmosphere is opaque in the near-infrared due to gaseous absorptions, mainly by methane, and scattering by aerosols, except in a few "transparency windows." Thus, the composition of Titan's surface remains difficult to access from space and is still poorly constrained. Photochemical models suggest that most of the organic compounds formed in the atmosphere are heavy enough to condense and build up at the surface in liquid and solid states over geological timescales. Acetylene (C 2 H 2 ) net production in the atmosphere is predicted to be larger than any other compound and C 2 H 2 has been speculated to exist on the surface of Titan. C 2 H 2 was detected as a trace gas sublimated/evaporated from the surface using the Gas Chromatograph Mass Spectrometer after the landing of the Huygens probe. Here we show evidence of C 2 H 2 on the surface of Titan by detecting absorption bands at 1.55 and 4.93 μm using the Cassini Visual and Infrared Mapping Spectrometer at three different equatorial areas-Tui Regio, eastern Shangri La, and Fensal-Aztlan/Quivira. We found that C 2 H 2 is preferentially detected in lowalbedo areas, such as sand dunes and near the Huygens landing site. The specific location of the C 2 H 2 detections suggests that C 2 H 2 is mobilized by surface processes, such as surface weathering by liquids through dissolution/ evaporation processes.

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Titan’s surface and atmosphere from Cassini/VIMS data with updated methane opacity

Cited by 101 publications

References 78 publications

Titan’s surface composition and atmospheric transmission with solar occultation measurements by Cassini VIMS

Titan’s surface composition and atmospheric transmission with solar occultation measurements by Cassini VIMS

Toward the Analysis of JWST Exoplanet Spectra: Identifying Troublesome Model Parameters

Acetylene on Titan’s Surface

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