Search Publications
Formation and distribution of benzene on Titan
Yelle, R. V.; Vuitton, V.; Cui, J.
We present a study of the formation and distribution of benzene (C6H6) on Titan. Analysis of the Cassini Mass Spectrometer (INMS) measurements of benzene densities on 12 Titan passes shows that the benzene signal exhibits an unusual time dependence, peaking ~20 s after closest approach, rather than at closest approach. We sho…
Methane escape from Titan's atmosphere
Yelle, R. V.; Cui, J.; Müller-Wodarg, I. C. F.
Measurements of the mole fractions of CH4 and 40Ar by the Ion Neutral Mass Spectrometer on the Cassini orbiter are analyzed to determine the rate of vertical mixing in Titan's atmosphere and the escape flux of CH4. Analysis of the 40Ar data indicates an eddy mixing rate of 2-5 × 107 cm2
Large-scale spring deposits on Mars?
van Gasselt, Stephan; Neukum, Gerhard; Hauber, Ernst +5 more
We present a large-scale spring hypothesis for the formation of various enigmatic light-toned deposits (LTDs) on Mars. Layered to massive LTDs occur extensively in Valles Marineris, chaotic terrains, and several large craters, in particular, those located in Arabia Terra. Most of these deposits are not easily explained with either a single process…
Horizontal structures and dynamics of Titan's thermosphere
Waite, J. H.; Yelle, R. V.; Cui, J. +1 more
The Cassini Ion Neutral Mass Spectrometer (INMS) measures densities of gases including N2 and CH4 in situ in Titan's upper atmosphere. We have used data from 13 targeted flybys of Titan (T5-T32) to construct an empirical model that describes the mean state of the thermosphere in the northern hemisphere, giving the N2
Distribution and escape of molecular hydrogen in Titan's thermosphere and exosphere
Yelle, R. V.; Volk, K.; Cui, J.
We present an in-depth study of the distribution and escape of molecular hydrogen (H2) on Titan, based on the global average H2 distribution at altitudes between 1000 and 6000 km, extracted from a large sample of Cassini/Ion and Neutral Mass Spectrometer (INMS) measurements. Below Titan's exobase, the observed H2 d…
HDO and H2O vertical distributions and isotopic ratio in the Venus mesosphere by Solar Occultation at Infrared spectrometer on board Venus Express
Montmessin, F.; Fedorova, A.; Korablev, O. +8 more
Vertical distributions of the molecular density and mixing ratios of H2O and HDO in the Venus mesosphere have been obtained using Solar Occultation at Infrared (SOIR), a high-resolution (with λ/δλ ~ 20,000) echelle spectrometer on Venus Express. The atmosphere is sounded in solar occultation in the range of altitudes from 65 to 130 km. …
The drying of Titan's dunes: Titan's methane hydrology and its impact on atmospheric circulation
Mitchell, Jonathan L.
We explore the effect of a finite reservoir of methane on Titan's atmospheric circulation, precipitation patterns, and surface methane content. We develop a soil model that accounts for the methane cycle in the surface-atmosphere system, and we implement this surface model in a two-dimensional model of the Titan's atmosphere. Seasonal oscillations…
Venus surface thermal emission at 1 µm in VIRTIS imaging observations: Evidence for variation of crust and mantle differentiation conditions
Erard, S.; Drossart, P.; Piccioni, G. +4 more
The Venus Express spacecraft images the nightside thermal emissions using the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS). At 1.02, 1.10, and 1.18 µm, thermal emission from the surface is observed. The signal is attenuated by scattering and absorption in the dense atmosphere. The measured flux at the top of the atmosphere is p…
A latitudinal survey of CO, OCS, H2O, and SO2 in the lower atmosphere of Venus: Spectroscopic studies using VIRTIS-H
Drossart, P.; Piccioni, G.; Bézard, B. +3 more
The high-resolution channel (R $\simeq$ 2000) of the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument (VIRTIS-H) aboard Venus Express has provided numerous spectra of the nightside infrared thermal emission in the 2.3-µm window. Mixing ratios of various minor species in the 30-40 km range could therefore be inferred usin…
Monte Carlo model of electron transport for the calculation of Mars dayglow emissions
Leblanc, F.; Gérard, J. -C.; Shematovich, V. I. +3 more
A model of the photoelectron collision-induced component of the Mars dayglow using recent cross sections and solar flux is described. The calculation of the photoelectron source of excitation is based on a stochastic solution of the Boltzmann equation using the direct simulation Monte Carlo method. The neutral atmosphere is taken from outputs of a…