Titan's Atmospheric Temperatures, Winds, and Composition

Flasar, F. M.; Achterberg, R. K.; Conrath, B. J.; Gierasch, P. J.; Kunde, V. G.; Nixon, C. A.; Bjoraker, G. L.; Jennings, Donald E.; Romani, P. N.; Simon-Miller, A. A.; Bézard, Bruno; Coustenis, A.; Irwin, Patrick; Teanby, N. A.; Brasunas, J. C.; Pearl, J. C.; Segura, M.; Carlson, R.; Mamoutkine, A. A.; Schinder, P. J.; Barucci, A.; Courtin, R.; Fouchet, Thierry; Gautier, D.; Lellouch, E.; Marten, A.; Prangé, Renée; Vinatier, S.; Strobel, D. F.; Calcutt, S. B.; Read, P. L.; Taylor, F. W.; Bowles, N. E.; Samuelson, R. E.; Orton, Glenn S.; Spilker, L. J.; Owen, Tobias; Spencer, J. R.; Showalter, M. R.; Ferrari, C.; Abbas, M. M.; Raulin, F.; Edgington, S. G.; Ade, Peter A. R.; Wishnow, Ed

doi:10.1126/science.1111150

Cited by 318 publications

(270 citation statements)

References 29 publications

Supporting

Mentioning

244

Contrasting

Order By: Relevance

“…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 Observationssupporting

confidence: 49%

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

Bampasidis

Coustenis

Achterberg

et al. 2012

ApJ

Self Cite

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

Section: Context and Observationssupporting

confidence: 49%

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

Bampasidis

Coustenis

Achterberg

et al. 2012

ApJ

Self Cite

View full text Add to dashboard Cite

show abstract

“…15,57,58 Similarly, recent Cassini CIRS observations have also confirmed what was inferred from previous measurements, that C is substantially enriched in the atmosphere of Saturn. 59,60 In order to interpret these volatile enrichments, it has been proposed that the main volatile compounds initially existing in the solar nebula gas phase were essentially trapped by crystalline water ice in the form of clathrates or hydrates in the feeding zones of Jupiter and Saturn. 14,[17][18][19]24,26,27 These ices then agglomerated and formed planetesimals that were ultimately accreted by the forming Jupiter and Saturn.…”

Section: Volatile Enrichments In Saturnmentioning

confidence: 99%

Volatile inventories in clathrate hydrates formed in the primordial nebula

et al. 2010

View full text Add to dashboard Cite

Examination of ambient thermodynamic conditions suggest that clathrate hydrates could exist in the martian permafrost, on the surface and in the interior of Titan, as well as in other icy satellites. Clathrate hydrates probably formed in a significant fraction of planetesimals in the solar system. Thus, these crystalline solids may have been accreted in comets, in the forming giant planets and in their surrounding satellite systems. In this work, we use a statistical thermodynamic model to investigate the composition of clathrate hydrates that may have formed in the primordial nebula. In our approach, we consider the formation sequence of the different ices occurring during the cooling of the nebula, a reasonable idealization of the process by which volatiles are trapped in planetesimals. We then determine the fractional occupancies of guests in each clathrate hydrate formed at given temperature. The major ingredient of our model is the description of the guest-clathrate hydrate interaction by a spherically averaged Kihara potential with a nominal set of parameters, most of which being fitted on experimental equilibrium data. Our model allows us to find that Kr, Ar and N 2 can be efficiently encaged in clathrate hydrates formed at temperatures higher than ∼ 48.5 K in the primitive nebula, instead of forming pure condensates below 30 K. However, we find at the same time that the determination of the relative abundances of guest species incorporated in these clathrate hydrates strongly depends on the choice of the parameters of the Kihara potential and also on the adopted size of cages. Indeed, testing different potential parameters, we have noted that even minor dispersions between the different existing sets can lead to non-negligible variations in the determination of the volatiles trapped in clathrate hydrates formed in the primordial nebula. However, these variations are not found to be strong enough to reverse the relative abundances between the different volatiles in the clathrate hydrates themselves. On the other hand, if contraction or expansion of the cages due to temperature variations are imposed in our model, the Ar and Kr mole fractions can be modified up to several orders of magnitude in clathrate hydrates. Moreover, mole fractions of other molecules such as N 2 or CO are also subject to strong changes with the variation of the size of the cages. Our results may affect the predictions of the composition of the planetesimals formed in the outer solar system. In particular, the volatile abundances calculated in the giant planets atmospheres should be altered because these quantities are proportional to the mass of accreted and vaporized icy planetesimals. For similar reasons, the estimates of the volatile budgets accreted by icy satellites and comets may also be altered by our calculations. For instance, under some conditions, our calculations predict that the abundance of argon in the atmosphere of Titan should be higher than the value measured by Huygens. Moreover, the Ar abundance in comets...

show abstract

“…The 'vertical' derivative must be taken along cylinders parallel to the rotation axis because the vertical scale of Titan's atmosphere (figure 1) is not small compared with its 2575 km radius (e.g. Flasar et al 2005). (With thin atmospheres, one can recover the more familiar case in which one can use a vertical derivative v/vz with the substitution dzZdz s sin L 0 , where L 0 remains constant over the vertical integration.)…”

Section: Temperatures and Zonal Windsmentioning

confidence: 99%

“…The dashed portions of the profile are initial guesses. Adapted from Flasar et al (2005). Temperatures derived near 108 S (grey curve) from HASI (NASA Planetary Data System archive) during the entry phase (upper portion), in which accelerometer data were used to estimate mass densities, and the descent phase (lower portion), which had pressure and temperature sensor measurements.…”

Section: Temperatures and Zonal Windsmentioning

confidence: 99%

The structure and dynamics of Titan's middle atmosphere

Flasar

Achterberg

2008

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

Titan's middle atmosphere is characterized by cyclostrophic winds and strong seasonal modulation. Cassini CIRS observations, obtained in northern winter, indicate that the stratosphere near 1 mbar is warmest at low latitudes, with the South Pole a few degrees colder and the North Pole approximately 20 K colder. Associated with the cold northern temperatures are strong circumpolar winds with speeds as high as 190 m s K1 . Within this vortex, the mixing ratios of several organic gases are enhanced relative to those at low latitudes. Comparison with Voyager thermal infrared measurements, obtained 25 years ago in northern spring, suggests that the enhancement currently observed will increase as the winter progresses. The stratopause height increases from 0.1 mbar near the equator to 0.01 mbar near the North Pole, where it is the warmest part of the atmosphere, greater than 200 K. This implies subsidence at the pole, which is consistent with the enhanced organics observed. Condensate features, several still not identified, are also apparent in the infrared spectra at high northern latitudes. In many ways, the winter vortex observed on Titan, with cyclostrophic winds, resembles the polar winter vortices on the Earth, where the mean winds are geostrophic.

show abstract

Titan's Atmospheric Temperatures, Winds, and Composition

Cited by 318 publications

References 29 publications

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

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

Volatile inventories in clathrate hydrates formed in the primordial nebula

The structure and dynamics of Titan's middle atmosphere

Contact Info

Product

Resources

About