Vertical abundance profiles of hydrocarbons in Titan's atmosphere at 15° S and 80° N retrieved from Cassini/CIRS spectra

Vinatier, Sandrine; Bézard, Bruno; Fouchet, Thierry; Teanby, N. A.; deKok, Remco; Irwin, Patrick; Conrath, B. J.; Nixon, C. A.; Romani, P. N.; Flasar, F. M.

doi:10.1016/j.icarus.2006.10.031

Cited by 179 publications

(233 citation statements)

References 47 publications

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“…We do not use the flux at the first, deepest level as a constraint because the variation of the Planck function at deeper levels is fixed arbitrarily in the model to that of the first layer. To solve this system of n p−1 equations, we use a constrained linear inversion method described in Vinatier et al (2007) and based on Conrath et al (1998). The algorithm minimizes the quadratic difference (χ 2 ) between desired (σT 4 eff ) and calculated fluxes with the additional constraint that the solution temperature profile lies close to the reference profile.…”

Section: Discussionmentioning

confidence: 99%

Interpreting the photometry and spectroscopy of directly imaged planets: a new atmospheric model applied toβPictoris b and SPHERE observations

Baudino

Bézard

Boccaletti

et al. 2015

A&A

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Context. Since the end of 2013 a new generation of instruments optimized to image young giant planets around nearby stars directly is becoming available on 8-m class telescopes, both at Very Large Telescope and Gemini in the southern hemisphere. Beyond the achievement of high contrast and the discovery capability, these instruments are designed to obtain photometric and spectral information to characterize the atmospheres of these planets. Aims. We aim to interpret future photometric and spectral measurements from these instruments, in terms of physical parameters of the planets, with an atmospheric model using a minimal number of assumptions and parameters. Methods. We developed the Exoplanet Radiative-convective Equilibrium Model (Exo-REM) to analyze the photometric and spectroscopic data of directly imaged planets. The input parameters are a planet's surface gravity (g), effective temperature (T eff ), and elemental composition. The model predicts the equilibrium temperature profile and mixing ratio profiles of the most important gases. Opacity sources include the H 2 -He collision-induced absorption and molecular lines from eight compounds (including CH 4 updated with the Exomol line list). Absorption by iron and silicate cloud particles is added above the expected condensation levels with a fixed scale height and a given optical depth at some reference wavelength. Scattering was not included at this stage.Results. We applied Exo-REM to photometric and spectral observations of the planet β Pictoris b obtained in a series of near-infrared filters. We derived T eff = 1550 ± 150 K, log(g) = 3.5 ± 1, and radius R = 1.76 ± 0.24 R Jup (2σ error bars from photometric measurements). These values are comparable to those found in the literature, although with more conservative error bars, consistent with the model accuracy. We were able to reproduce, within error bars, the J-and H-band spectra of β Pictoris b. We finally investigated the precision to which the above parameters can be constrained from SPHERE measurements using different sets of near-infrared filters as well as low-resolution spectroscopy.

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Section: Discussionmentioning

confidence: 99%

Interpreting the photometry and spectroscopy of directly imaged planets: a new atmospheric model applied toβPictoris b and SPHERE observations

Baudino

Bézard

Boccaletti

et al. 2015

A&A

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“…Such processing could occur due to the action of charged particles or communication between the interior and the surface. Although a vast majority of the galactic cosmic rays (GCR) are stopped above the tropopause of Titan, a small flux of 26 and upper atmosphere, and Voyager H 2 observations. 34 (b) The model-generated mole fraction profile (solid line) and the saturation mole fraction profile (dashed line) for C 2 H 6 .…”

Section: Ethane Condensationmentioning

confidence: 99%

Titan’s Carbon Budget and the Case of the Missing Ethane

Wilson

Atreya

2009

J. Phys. Chem. A

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The retrieval of data from the Cassini-Huygens mission has revealed much about Titan's atmosphericsurface system and has precipitated more questions. One of these questions involves the lack of large reservoirs of ethane that were predicted by a variety of studies prior to the arrival of the Cassini-Huygens spacecraft. Using an updated and comprehensive photochemical model, we examine the nature of Titan's carbon budget, initiated by the destruction of methane, and the role that ethane condensation plays in this budget. Model results show that 40% of methane destruction results in ethane formation, with a net production rate of 2.7 × 10 9 molecules cm -2 s -1 , due primarily to acetylenic catalysis in Titan's stratosphere. This corresponds to a liquid ethane layer of several hundred meters over geologic time. However, episodic methane outgassing, subsurface sequestration, and chemical processing of Titan's surface are likely responsible for the limiting of ethane condensate on Titan's surface to less than 10 m globally averaged.

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“…This includes Titan's troposphere with its well defined tropopause at ∼44 km (112 mbar), the stratosphere with the stratopause located at ∼260−310 km (0.22−0.08 mbar; Fulchignoni et al 2005;Vinatier et al 2007), the mesosphere with the mesopause at ∼494 km (0.002 mbar; Fulchignoni et al 2005), and the thermosphere ranging up to ∼1300 km (1.4 × 10 −8 mbar).…”

Section: Atmospheric Parametersmentioning

confidence: 99%

HST observations of the limb polarization of Titan

Bazzon

Schmid

Buenzli

2014

A&A

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Context. Titan is an excellent test case for detailed studies of the scattering polarization from thick hazy atmospheres. Accurate scattering and polarization parameters have been provided by the in situ measurements of the Cassini-Huygens landing probe. For Earth-bound observations Titan can only be observed at a backscattering situation, where the disk-integrated polarization is close to zero. However, with resolved imaging polarimetry a second order polarization signal along the entire limb of Titan can be measured. Aims. We present the first limb polarization measurements of Titan, which are compared as a test to our limb polarization models. Methods. Previously unpublished imaging polarimetry from the HST archive is presented, which resolves the disk of Titan. We determine flux-weighted averages of the limb polarization and radial limb polarization profiles, and investigate the degradation and cancelation effects in the polarization signal due to the limited spatial resolution of our observations. Taking this into account we derive corrected values for the limb polarization in Titan. The results are compared with limb polarization models, using atmosphere and haze scattering parameters from the literature. Results. In the wavelength bands between 250 nm and 2 μm a strong limb polarization of about 2−7% is detected with a position angle perpendicular to the limb. The fractional polarization is highest around 1 μm. As a first approximation, the polarization seems to be equally strong along the entire limb. The comparison of our data with model calculations and the literature shows that the detected polarization is compatible with expectations from previous polarimetric observations taken with Voyager 2, Pioneer 11, and the Huygens probe. Conclusions. Our results indicate that ground-based monitoring measurements of the limb-polarization of Titan could be useful for investigating local haze properties and the impact of short-term and seasonal variations of the hazy atmosphere of Titan. Planets with hazy atmospheres similar to Titan are particularly good candidates for detection with the polarimetric mode of the upcoming planet finder instrument at the VLT. Therefore, a good knowledge of the polarization properties of Titan is also important for the search and investigation of extra-solar planets.

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Vertical abundance profiles of hydrocarbons in Titan's atmosphere at 15° S and 80° N retrieved from Cassini/CIRS spectra

Cited by 179 publications

References 47 publications

Interpreting the photometry and spectroscopy of directly imaged planets: a new atmospheric model applied toβPictoris b and SPHERE observations

Interpreting the photometry and spectroscopy of directly imaged planets: a new atmospheric model applied toβPictoris b and SPHERE observations

Titan’s Carbon Budget and the Case of the Missing Ethane

HST observations of the limb polarization of Titan

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