HR: 14:20h
AN: P43B-03    [Abstracts]
TI: Results From the Gas Chromatograph Mass Spectrometer (GCMS) Experiment on the Cassini-Huygens Probe
AU: * Niemann, H B
EM: Hasso.B.Niemann@nasa.gov
AF: NASA Goddard Space Flight Center, Atmospheric Experiments Lab, Greenbelt, MD 20771 United States
AU: Atreya, S K
EM: atreya@umich.edu
AF: University of Michigan, University of Michigan, Ann Arbor, MI 48109 United States
AU: Bauer, S J
EM: siegfried.bauer@kfunigraz.ac.at
AF: Institute for Meteorology and Geophysics, University of Graz , Graz, A-8010 Austria
AU: Carignan, G R
EM: carignan@engin.umich.edu
AF: University of Michigan, University of Michigan, Ann Arbor, MI 48109 United States
AU: Demick-Montelara, J E
EM: jdemick@pop900.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Atmospheric Experiments Lab, Greenbelt, MD 20771 United States
AU: Frost, R L
EM: frost@cbse.uab.edu
AF: University of Alabama, CBSE 100 1530 Third Avenue South , Birmingham, AL 35294 United States
AU: Gautier, D
EM: daniel.gautier@obspm.fr
AF: LESIA, Observatoire de Paris-Meudon, Meudon Cedex, F-92195 France
AU: Haberman, J A
EM: john.a.haberman@nasa.gov
AF: NASA Goddard Space Flight Center, Atmospheric Experiments Lab, Greenbelt, MD 20771 United States
AU: Harpold, D N
EM: Dan.N.Harpold@nasa.gov
AF: NASA Goddard Space Flight Center, Atmospheric Experiments Lab, Greenbelt, MD 20771 United States
AU: Hunten, D M
EM: dhunten@lpl.arizona.edu
AF: Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85716 United States
AU: Israel, G
EM: guy.israel@aerov.jussieu.fr
AF: Service d'A‚ronomie du CNRS, BP. 3 , VerriŠres le Buisson, F-91371 France
AU: Lunine, J I
EM: jlunine@lpl.arizona.edu
AF: Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85716 United States
AU: Kasprzak, W T
EM: Wayne.T.Kasprzak@nasa.gov
AF: NASA Goddard Space Flight Center, Atmospheric Experiments Lab, Greenbelt, MD 20771 United States
AU: Owen, T C
EM: owen@ifa.hawaii.edu
AF: Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 United States
AU: Paulkovich, M
EM: michael@perfect11.com
AF: NASA Goddard Space Flight Center, Atmospheric Experiments Lab, Greenbelt, MD 20771 United States
AU: Raulin, F C
EM: raulin@lisa.univ-paris12.fr
AF: LISA, Universit‚ Paris 12 et Paris 7 Avenue du g‚n‚ral de Gaulle, Creteil Cedex, F-94010 France
AU: Raaen, E
EM: eric.raaen.1@gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Atmospheric Experiments Lab, Greenbelt, MD 20771 United States
AU: Way, S H
EM: sway@pop900.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Atmospheric Experiments Lab, Greenbelt, MD 20771 United States
AB: The GCMS was part of the instrument complement on the Cassini-Huygens Probe to measure in situ the chemical composition of the atmosphere of Titan during the probe descent and to support the Aerosol Collector Pyrolyser (ACP) experiment by serving as detector for the pyrolization products. The instrument consisted of a quadrupole mass filter with secondary electron multiplier detectors, and a gas sampling system providing continuous direct atmospheric composition measurements and batch sampling through three gas chromatographic (GC) columns. The gas inlet was heated to prevent condensation, and served to evaporate surface constituents after impact. Data were collected from an altitude of 146 km to ground impact. The Probe and the GCMS survived impact and collected data for 1 hour and 9 minutes on the surface. Mass spectra were collected during descent and on the ground over a range of m/z from 2 to 141. Eight gas chromatograph samples were taken during the descent and two on the ground. The major constituents of the lower atmosphere were confirmed to be N₂ and CH₄. The methane mole fraction was fairly uniform in the stratosphere. It began to increase monotonically below 32 km altitude, reaching a plateau at about 8 km at a mixing level near saturation. After surface impact a steep increase of the methane signal was observed, suggesting evaporation of surface condensed methane due to heating by the sample inlet heater. The presence of Argon 40 was confirmed at (4.32±0.1) ×10^-5 mole fraction. 36Ar was detected at a mole fraction of (2.8±0.3)x10^-7. The other primordial noble gases were below 10^-8 mixing ratio. The isotope ratios of ¹²C/¹³C, ¹⁴N/¹⁵N and D/H were determined to be 82.3±1, 183±5, and (2.3 ±0.5)x10^-4 respectively. Altitude profiles were measured for carbon dioxide, ethane, and cyanogen, which were also evaporating from the surface. Isotope ratios for the major carbon and nitrogen isotopes were computed from methane and molecular nitrogen measurements.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0325 Evolution of the atmosphere (1610, 8125)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005