The structure of Titan’s atmosphere from Cassini radio occultations: Occultations from the Prime and Equinox missions

Schinder, P. J.; Flasar, F. M.; Marouf, E. A.; French, R. G.; McGhee, C. A.; Kliore, A. J.; Rappaport, N. J.; Barbinis, E.; Fleischman, D.; Anabtawi, A.

doi:10.1016/j.icarus.2012.10.021

Cited by 62 publications

(41 citation statements)

References 41 publications

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“…That result, 93.65±0.25 K, agrees within the error with our measurements in 2004-2006 (L s = 313°). Between 2005 and 2013 the temperature at the Huygens touchdown latitude had decreased by about 1 K. Our measurements also agree with near-surface temperatures reported by Schinder et al (2011Schinder et al ( , 2012 from Cassini radio occultations. Their 10 reported ingress and egress surface temperatures, near the same latitudes and dates, were on average 0.25 K lower than CIRS with a standard deviation of 0.45 K.…”

Section: Resultssupporting

confidence: 90%

“…The model is based on the temperature profile measured in situ at 0-147 km altitude by the Huygens Atmospheric Structure Instrument (HASI) on the Huygens descent probe (Fulchignoni et al 2005). Modifications were applied to the HASI profile to account for latitude dependences and seasonal variations in temperature found by CIRS and Cassini radio occultations (Coustenis et al 2007(Coustenis et al , 2010(Coustenis et al , 2013(Coustenis et al , 2015Achterberg et al 2008Achterberg et al , 2011Schinder et al 2011Schinder et al , 2012Bampasidis et al 2012). At latitudes greater than about 60°the stratospheric temperature had a minimum in winter near 120 km.…”

Section: Discussionmentioning

confidence: 99%

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Surface Temperatures on Titan During Northern Winter and Spring

Jennings

Cottini

Nixon

et al. 2016

ApJL

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Meridional brightness temperatures were measured on the surface of Titan during the 2004-2014 portion of the Cassini mission by the Composite Infrared Spectrometer. Temperatures mapped from pole to pole during five twoyear periods show a marked seasonal dependence. The surface temperature near the south pole over this time decreased by 2 K from 91.7±0.3 to 89.7±0.5 K while at the north pole the temperature increased by 1 K from 90.7±0.5 to 91.5±0.2 K. The latitude of maximum temperature moved from 19 S to 16 N, tracking the subsolar latitude. As the latitude changed, the maximum temperature remained constant at 93.65±0.15 K. In 2010 our temperatures repeated the north-south symmetry seen by Voyager one Titan year earlier in 1980. Early in the mission, temperatures at all latitudes had agreed with GCM predictions, but by 2014 temperatures in the north were lower than modeled by 1 K. The temperature rise in the north may be delayed by cooling of sea surfaces and moist ground brought on by seasonal methane precipitation and evaporation.

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Section: Resultssupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Surface Temperatures on Titan During Northern Winter and Spring

Jennings

Cottini

Nixon

et al. 2016

ApJL

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“…For Titan, there are still difficulties in retrieving the meridional distribution of temperature in the lower atmosphere (e.g., troposphere) with the Cassini/CIRS observations, even though the meridional distribution of temperature in the upper atmosphere (e.g., stratosphere and mesosphere) have been obtained (Achterberg et al, 2008;Flasar et al, 2005). The observations from the Huygens probe and the Cassini radio occultation provided vertical profiles of temperature in Titan's troposphere (Fulchignoni et al, 2005;Schinder et al, 2012), but these observations have a limited coverage of latitude. Therefore, the method of determining the effective pressure levels for the emitted power by the meridional comparison between the emitted power and the atmospheric temperature, which works for Jupiter and Saturn (Li et al, 2010(Li et al, , 2012, does not work for Titan because of the lack of the meridional profiles of tropospheric temperature.…”

Section: Resultsmentioning

confidence: 99%

Seasonal Variations of Titan's Brightness

Creecy

Jiang

et al. 2019

Geophysical Research Letters

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The absolute brightness of astronomical bodies can be represented by the emitted power, which plays important roles in their radiated energy budgets. The Cassini observations include three seasons of Titan, which provides an unprecedented opportunity to examine the seasonal variations of Titan's emitted power. Our analyses show that Titan's emitted power displays different seasonal behaviors between the Northern Hemisphere and the Southern Hemisphere. The global-average emitted power decreased by 6.8 ± 0.4% during the Cassini period (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017). Such a temporal variation represents the magnitude of the seasonal cycle of Titan's emitted power, which is at least one order of magnitude stronger than the seasonal variation of Earth's emitted power (<0.5%). More importantly, the~6.8% decrease of the emitted power is much smaller than the~18.6% decrease of the solar flux from the change of Sun-Titan distance, implying a significantly dynamical energy budget on Titan.Key Points:• The seasonal variations of Titan's emitted power are examined for the first time. • The seasonal cycle of the global-average emitted power is at least one order of magnitude stronger on Titan than on Earth. • The comparison of seasonal cycle between emitted power and solar flux suggests a significantly dynamical energy budget on Titan.

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“…Assuming a solid hydrocarbon land surface with dielectric constant between 2 and 2.4 sets an upper limit of T phys =92.5 K, while a similar constraint on sea surface limits the lowest T phys = 91.5 K. Extrapolating CIRS temperature measurements to 2013 yields T phys =92+/− 0.8 K. A GCM [ Tokano , ] predicts mostly slightly higher values. The radio occultation observation of T phys = 90.6 K on T31 provides a useful lower bound, as Titan has likely warmed roughly slightly more than 2 K since [ Schinder et al ., ]. The center of the plausible range would seem to be closer to the value for a methane sea than ethane.…”

Section: Discussionmentioning

confidence: 99%

“…A global climate model (GCM) due to Tokano [] predicts slightly higher values for most scenarios, but permanent haze in the polar atmosphere could lead to a much colder 89 K surface. A radio occultation observation of T phys =90.6 K on T31 provides a useful lower bound, as Titan has likely warmed roughly slightly more than 2 K since [ Schinder et al ., ]. Our experiment provides no evidence for the presence of significant evaporative cooling of the sea.…”

Section: Discussionmentioning

confidence: 99%

Surface of Ligeia Mare, Titan, from Cassini altimeter and radiometer analysis

Zebker

Hayes

Janssen

et al. 2014

Geophysical Research Letters

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Cassini radar observations of the surface of Ligeia Mare collected during the 23 May 2013 (T91)Cassini flyby show that it is extremely smooth, likely to be mostly methane in composition, and exhibits no surface wave activity. The radar parameters were tuned for nadir-looking geometry of liquid surfaces, using experience from Cassini's only comparable observation, of Ontario Lacus on 21 December 2008 (T49), and also include coincident radiometric observations. Radar echoes from both passes show very strong specular radar reflections and limit surface height variations to 1 mm rms. The surface physical temperature at 80°N is 92 +/À 0.5 K if the sea is liquid hydrocarbon and the land is solid hydrocarbon, essentially the same as Cassini CIRS measurements. Furthermore, radiometry measurements over the surrounding terrain suggest dielectric constants from 2.2 to 2.4, arguing against significant surface water ice unless it is extremely porous.

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The structure of Titan’s atmosphere from Cassini radio occultations: Occultations from the Prime and Equinox missions

Cited by 62 publications

References 41 publications

Surface Temperatures on Titan During Northern Winter and Spring

Surface Temperatures on Titan During Northern Winter and Spring

Seasonal Variations of Titan's Brightness

Surface of Ligeia Mare, Titan, from Cassini altimeter and radiometer analysis

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