Temperature variations in Titan's upper atmosphere: Impact on Cassini/Huygens

Abstract

Abstract. Temperature variations of Titan's upper atmosphere due to the plasma interaction of the satellite with Saturn's magnetosphere and Titan's high altitude monomer haze particles can imply an offset of up to ±30 K from currently estimated model profiles. We incorporated these temperature uncertainties as an offset into the recently published Vervack et al. (2004) (Icarus, Vol. 170, engineering model and derive extreme case (i.e. minimum and maximum profiles) temperature, pressure, and density profiles. We simulated the Huygens probe hypersonic entry trajectory and obtain, as expected, deviations of the probe trajectory for the extreme atmosphere models compared to the simulation based on the nominal one. These deviations are very similar to the ones obtained with the standard Yelle et al. (1997) (ESA SP-1177) profiles. We could confirm that the difference in aerodynamic drag is of an order of magnitude that can be measured by the probe science accelerometer. They represent an important means for the reconstruction of Titan's upper atmospheric properties. Furthermore, we simulated a Cassini low Titan flyby trajectory. No major trajectory deviations were found. The atmospheric torques due to aerodynamic drag, however, are twice as high for our high temperature profile as the ones obtained with the Yelle maximum profile and more than 5 times higher than the worst case estimations from the Cassini project. We propose to use the Cassini atmospheric torque measurements during its low flybys to derive the atmospheric drag and to reconstruct Titan's upper atmosphere density, pressure, and temperature. The results could then be compared to the reconstructed profiles obtained from Huygens probe measurements. This would help to validate the probe measurements and decrease the error bars.

Chemistry in Acetonitrile–Water Films Induced by Slow (<15 eV) Electrons: Application to the Earth and Space Chemistry

“…25 The present outcomes may, for instance, potentially contribute to a better comprehension of the chemistry occurring in the troposphere of Titan. Indeed, at this altitude (∼60 km), the temperature meets the high density of the secondary electrons and molecules, 57,58 and methanol may possibly be formed according to the gas chromatography− mass spectrometry (GC−MS) spectra of the lower (<130 km) atmosphere that exhibit peaks in the m/z 26−33 amu range. 59 This information may also increase the knowledge on the chemistry of the Earth's atmosphere.…”