Analysis of Cassini/CIRS limb spectra of Titan acquired during the nominal mission

Vinatier, S.; Bézard, Bruno; Nixon, C. A.; Mamoutkine, A. A.; Carlson, R.; Jennings, Donald E.; Guandique, E.; Teanby, N. A.; Bjoraker, G. L.; Flasar, F. M.; Kunde, V. G.

doi:10.1016/j.icarus.2009.08.013

Cited by 180 publications

(202 citation statements)

References 37 publications

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“…Latitudinal variations in Titan's stratospheric thermal and chemical structure have been reported in the past from Cassini data acquired by the Composite Infrared Spectrometer (CIRS) (Flasar et al 2005;Teanby et al 2006;Coustenis et al 2007Coustenis et al , 2008Coustenis et al , 2010de Kok et al 2007;Teanby et al , 2008Teanby et al , 2009aVinatier et al 2007Vinatier et al , 2010Nixon et al 2008a;Achterberg et al 2008Achterberg et al , 2011. Here, we explore the thermal and chemical evolution discernible within the timeframe from 2006 to 2012, thus complementing and refining previous reports from earlier stages of the mission.…”

Section: Context and Observationsmentioning

confidence: 56%

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

Bampasidis

Coustenis

Achterberg

et al. 2012

ApJ

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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.

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Section: Context and Observationsmentioning

confidence: 56%

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

Bampasidis

Coustenis

Achterberg

et al. 2012

ApJ

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“…This model includes continuum opacities from collisioninduced absorption of N 2 -CH 4 pairs and uses the thermal profile from Huygens probe measurements (Fulchignoni et al 2005) combined with CIRS measurements (Vinatier et al 2010). Molecular lines of CO, HCN, and CH 4 and their isotopes are included, as are the HIFI and SPIRE observations.…”

Section: Callisto Ganymede and Titanmentioning

confidence: 99%

Far-infrared photometric observations of the outer planets and satellites withHerschel-PACS

Müller

Balog

Nielbock

et al. 2016

A&A

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We present all Herschel-PACS photometer observations of Mars, Saturn, Uranus, Neptune, Callisto, Ganymede, and Titan. All measurements were carefully inspected for quality problems, were reduced in a (semi-)standard way, and were calibrated. The derived flux densities are tied to the standard PACS photometer response calibration, which is based on repeated measurements of five fiducial stars. The overall absolute flux uncertainty is dominated by the estimated 5% model uncertainty of the stellar models in the PACS wavelength range between 60 and 210 µm. A comparison with the corresponding planet and satellite models shows excellent agreement for Uranus, Neptune, and Titan, well within the specified 5%. Callisto is brighter than our model predictions by about 4−8%, Ganymede by about 14−21%. We discuss possible reasons for the model offsets. The measurements of these very bright point-like sources, together with observations of stars and asteroids, demonstrate the high reliability of the PACS photometer observations and the linear behavior of the PACS bolometer source fluxes over more than four orders of magnitude (from mJy levels up to more than 1000 Jy). Our results show the great potential of using the observed solar system targets for cross-calibration purposes with other ground-based, airborne, and space-based instruments and projects. At the same time, the PACS results will lead to improved model solutions for future calibration applications.

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“…The thermal profile used for our computation is a combination of (i) the temperatures measured by Huygens/HASI (Fulchignoni et al 2005) in the troposphere at altitudes between 0-140 km; (ii) the disk-averaged Cassini/CIRS stratospheric temperatures (Vinatier et al 2010) at altitudes between 140-500 km; (iii) the Cassini/INMS retrieved temperatures (i.e. 155 K as average, de La Haye et al (2007)) at altitudes between 1000-1500 km; and (iv) a decreasing temperature from 165 K to 155 K at altitudes between 500 and 1000 km.…”

Section: Model Descriptionmentioning

confidence: 99%

A time-dependent photochemical model for Titan’s atmosphere and the origin of H₂O

Lara

Lellouch

González

et al. 2014

A&A

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Context. Titan's stratosphere contains oxygen compounds (CO, CO 2 , and H 2 O), implying an external source of oxygen whose nature is still uncertain. Recent observations from the Herschel Space Observatory using the HIFI and PACS instruments and the Cassini/CIRS, as well as steady-state photochemical modeling indicate that the amounts of CO 2 and H 2 O in Titan's stratosphere may imply inconsistent values of the OH/H 2 O input flux, and that the oxygen source is time-variable. Aims. We attempt to reconcile the H 2 O and CO 2 observed profiles in Titan's atmosphere by using an updated photochemical scheme and developing several time-dependent scenarios for the influx/evolution of oxygen species. Methods. We use a time-dependent photochemical model of Titan's atmosphere to calculate effective lifetimes and the response of Titan's oxygen compounds to changes in the oxygen input flux. Two variants for the C-H-O chemical network are considered. We investigate a time-variable Enceladus source and the evolution of material delivered by a cometary impact. Results. We find that the effective lifetime of H 2 O in Titan's atmosphere is only a factor of six shorter than that of CO 2 and exceeds 10 yr below 200 km. A time-variable Enceladus source, involving a decrease by a factor of 5-20 in the OH/H 2 O flux over the last few centuries, shows promise in explaining the relative CO 2 /H 2 O profiles. However, if the previous measurements from the Herschel Space Observatory are representative of Titan's atmospheric water, an additional H 2 O loss to the haze term is needed to bring the model in full agreement with the data. In an alternate situation, CO 2 production following a cometary impact that occurred at least 220-300 yr ago can in principle explain the CO 2 "excess" in Titan's stratosphere, but this scenario is highly unlikely, given the estimates of the impact rate at Titan.

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Analysis of Cassini/CIRS limb spectra of Titan acquired during the nominal mission

Cited by 180 publications

References 37 publications

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

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

Far-infrared photometric observations of the outer planets and satellites withHerschel-PACS

A time-dependent photochemical model for Titan’s atmosphere and the origin of H₂O

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Analysis of Cassini/CIRS limb spectra of Titan acquired during the nominal mission

Cited by 180 publications

References 37 publications

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

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

Far-infrared photometric observations of the outer planets and satellites withHerschel-PACS

A time-dependent photochemical model for Titan’s atmosphere and the origin of H2O

Contact Info

Product

Resources

About

A time-dependent photochemical model for Titan’s atmosphere and the origin of H₂O