Open AccessSimulating the one‐dimensional structure of Titan's upper atmosphere: 3. Mechanisms determining methane escape
Author(s) -
Bell Jared M.,
Bougher Stephen W.,
Waite J. Hunter,
Ridley Aaron J.,
Magee Brian A.,
Mandt Kathleen E.,
Westlake Joseph,
DeJong Anna D.,
BarNun Akiva,
Jacovi Ronen,
Toth Gabor,
De La Haye Virginie,
Gell David,
Fletcher Gregory
Publication year - 2011
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010je003639
Subject(s) - titan (rocket family) , methane , magnetosphere , ionosphere , thermosphere , physics , atmosphere of titan , atmosphere (unit) , ion , atmospheric sciences , altitude (triangle) , spectrometer , mixing ratio , mass spectrometry , astrobiology , plasma , atomic physics , computational physics , geophysics , meteorology , chemistry , nuclear physics , optics , organic chemistry , geometry , mathematics , quantum mechanics
This investigation extends the work presented by Bell et al. (2010a, 2010b). Using the one‐dimensional (1‐D) configuration of the Titan Global Ionosphere‐Thermosphere Model (T‐GITM), we quantify the relative importance of the different dynamical and chemical mechanisms that determine the CH 4 escape rates calculated by T‐GITM. Moreover, we consider the implications of updated Huygens Gas Chromatograph Mass Spectrometer (GCMS) determinations of both the 40 Ar mixing ratios and 15 N/ 14 N isotopic ratios in work by Niemann et al. (2010). Combining the GCMS constraints in the lower atmosphere with the Ion Neutral Mass Spectrometer (INMS) measurements in work by Magee et al. (2009), our simulation results suggest that the optimal CH 4 homopause altitude is located at 1000 km. Using this homopause altitude, we conclude that topside escape rates of 1.0 × 10 10 CH 4 m −2 s −1 (referred to the surface) are sufficient to reproduce the INMS methane measurements in work by Magee et al. (2009). These escape rates of methane are consistent with the upper limits to methane escape (1.11 × 10 11 CH 4 m −2 s −1 ) established by both the Cassini Plasma Spectrometer (CAPS) and Magnetosphere Imaging Instrument (MIMI) measurements of Carbon‐group ions in the near Titan magnetosphere.