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Strong Tidal Dissipation in Saturn and Constraints on Enceladus' Thermal State from Astrometry
Charnoz, Sébastien; Mathis, Stéphane; Tobie, Gabriel +8 more
Tidal interactions between Saturn and its satellites play a crucial role in both the orbital migration of the satellites and the heating of their interiors. Therefore, constraining the tidal dissipation of Saturn (here the ratio k 2/Q) opens the door to the past evolution of the whole system. If Saturn's tidal ratio can be determined at…
On the Migration of Jupiter and Saturn: Constraints from Linear Models of Secular Resonant Coupling with the Terrestrial Planets
Lin, D. N. C.; Agnor, Craig B.
We examine how the late divergent migration of Jupiter and Saturn may have perturbed the terrestrial planets. Using a modified secular model we have identified six secular resonances between the ν5 frequency of Jupiter and Saturn and the four apsidal eigenfrequencies of the terrestrial planets (g 1-4). We derive analytic uppe…
Isotopic Ratios in Titan's Methane: Measurements and Modeling
Irwin, P. G. J.; Teanby, N. A.; Flasar, F. M. +10 more
The existence of methane in Titan's atmosphere (~6% level at the surface) presents a unique enigma, as photochemical models predict that the current inventory will be entirely depleted by photochemistry in a timescale of ~20 Myr. In this paper, we examine the clues available from isotopic ratios (12C/13C and D/H) in Titan's m…
The 12C/13C Ratio on Titan from Cassini INMS Measurements and Implications for the Evolution of Methane
Nixon, Conor A.; Mousis, Olivier; Lunine, Jonathan I. +6 more
We have re-evaluated the Cassini Ion Neutral Mass Spectrometer (INMS) 12C/13C ratios in the upper atmosphere of Titan based on new calibration sensitivities and an improved model for the NH3 background in the 13CH4 mass channel. The INMS measurements extrapolated to the surface give a 12<…
Titan's Transport-driven Methane Cycle
Mitchell, Jonathan L.
The mechanisms behind the occurrence of large cloud outbursts and precipitation on Titan have been disputed. A global- and annual-mean estimate of surface fluxes indicated only 1% of the insolation, or ~0.04 W m-2, is exchanged as sensible and/or latent fluxes. Since these fluxes are responsible for driving atmospheric convection, it ha…
Elusive Ethylene Detected in Saturn's Northern Storm Region
Fletcher, L. N.; Irwin, P. G. J.; Achterberg, R. K. +9 more
The massive eruption at 40°N (planetographic latitude) on Saturn in 2010 December has produced significant and lasting effects in the northern hemisphere on temperature and species abundances. The northern storm region was observed on many occasions in 2011 by Cassini's Composite Infrared Spectrometer (CIRS). In 2011 May, temperatures in the strat…
Thermal and Chemical Structure Variations in Titan's Stratosphere during the Cassini Mission
Teanby, N. A.; Flasar, F. M.; Preka-Papadema, P. +12 more
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 ge…
Seasonal Disappearance of Far-infrared Haze in Titan's Stratosphere
Calcutt, S. B.; de Kok, R.; Flasar, F. M. +9 more
A far-infrared emission band attributed to volatile or refractory haze in Titan's stratosphere has been decreasing in intensity since Cassini's arrival in 2004. The 220 cm-1 feature, first seen by the Voyager Infrared Interferometer Spectrometer, has only been found in Titan's winter polar region. The emission peaks at about 140 km alti…
First Observation in the South of Titan's Far-infrared 220 cm-1 Cloud
Teanby, N. A.; Calcutt, S. B.; de Kok, R. +15 more
An emission feature at 220 cm-1 which has been attributed to a cloud of condensed material in Titan's winter stratosphere has been seen for the first time in the south. This feature had previously been found only at high northern latitudes during northern winter and spring. The material emitting at 220 cm-1, as yet unidentifi…
Cassini VIMS Observations Show Ethane is Present in Titan's Rainfall
Nicholson, Philip D.; Sotin, Christophe; Barnes, Jason W. +6 more
Observations obtained over two years by the Cassini Imaging Science Subsystem suggest that rain showers fall on the surface. Using measurements obtained by the Visual Infrared Mapping Spectrometer, we identify the main component of the rain to be ethane, with methane as an additional component. We observe five or six probable rainfall events, at l…