Scientific and Technical Aerospace Reports Volume 38 July 28, 2000

20000064708 Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA USA
Photochemistry of Saturn’s Atmosphere, 1, Hydrocarbon Chemistry and Comparisons with ISO Observations
Moses, Julianne I., Lunar and Planetary Inst., USA; Bezard, Bruno, Observatoire de Paris-Meudon, France; Lellouch, Emmanuel,
Observatoire de Paris-Meudon, France; Gladstone, G. Randall, Southwest Research Inst., USA; Feuchtgruber, Helmut, Max-
Planck-Inst. fuer Extraterrestrische Physik, Germany; Allen, Mark, Jet Propulsion Lab., California Inst. of Tech., USA; Icarus;
2000; ISSN 0019-1035; Volume I43, pp. 244-298; In English
Contract(s)/Grant(s): NASw-4574; NAG5-6915
Report No.(s): LPI-Contrib-982; Copyright; Avail: Issuing Activity
To investigate the details of hydrocarbon photochemistry on Saturn, we have developed a one-dimensional diurnally averaged
model that couples hydrocarbon and oxygen photochemistry, molecular and eddy diffusion, radiative transfer, and condensation.
The model results are compared with observations from the Infrared Space Observatory (ISO) to place tighter constraints
on molecular abundances, to better define Saturn’s eddy diffusion coefficient profile, and to identify important chemical schemes
that control the abundances of the observable hydrocarbons in Saturn’s upper atmosphere. From the ISO observations, we determine
that the column 12 densities of CH3, CH3C2H, and C4H2 above 10 mbar are 4 (sup +2) (sub -1.5) x 10 (exp 13) cm (sup
-2), (1.1 plus or minus 0.3) x 10 (exp 15) cm (exp -2), and (1.2 plus or minus 0.3) x 10 (exp 14) cm (sup -2), respectively. The
observed ISO emission features also indicate C2H2 mixing ratios of 1.2 (sup +0.9) (sub -0.6) x 10 (exp -6) at 0.3 mbar and (2.7
plus or minus 0.8) x 10 (exp -7) at 1.4 mbar, and a C2H6 mixing ratio of (9 plus or minus 2.5) x 10 (exp -6) at 0.5 mbar. Upper
limits are provided for C2H4, CH2CCH2, C3H8, and C6H2 sensitivity of the model results to variations in the eddy diffusion
coefficient profile, the solar flux, the CH4 photolysis branching ratios, the atomic hydrogen influx, and key reaction rates are discussed
in detail. We find that C4H2 and CH3C2H are particularly good tracers of important chemical processes and physical conditions
in Saturn’s upper atmosphere, and C2H6 is a good tracer of the eddy diffusion coefficient in Saturn’s lower stratosphere.
The eddy diffusion coefficient must be smaller than approximately 3 x 10 (exp 4) sq cm s (sup -1) at pressures greater than 1 mbar
in order to reproduce the C2H6 abundance inferred from ISO observations. The eddy diffusion coefficients in the upper stratosphere
could be constrained by observations of CH3 radicals if the low-temperature chemistry of CH3 were better understood.
We also discuss the implications of our modeling for aerosol formation in Saturn’s lower stratosphere-diacetylene, butane, and
water condense between approximately 1 and 300 mbar in our model and will dominate stratospheric haze formation at nonauroral
latitudes. Our photochemical models will be useful for planning observational sequences and for analyzing data from the upcoming
Cassini mission.
Author
Saturn (Planet); Saturn Atmosphere; Photochemical Reactions; Upper Atmosphere; Infrared Astronomy; Mathematical Models
20000064716 NASA Kennedy Space Center, Cocoa Beach, FL USA
Titan III Mars Observer Press Showing at the PHSF
Aug. 13, 1992; In English; Videotape: 2 min. 30 sec. playing time, in color, no sound
Report No.(s): NONP-NASA-VT-2000081554; No Copyright; Avail: CASI; B01, Videotape-Beta; V01, Videotape-VHS
Live footage of the Titan 3 Mars Observer is shown at the Payload Hazardous Servicing Facility (PHSF). The Mars Observer
is a NASA mission to study the surface, atmosphere, interior and magnetic field of Mars from Martian orbit.
CASI
Mars Observer; Payloads; Titan 3 Launch Vehicle
20000065630 NASA Kennedy Space Center, Cocoa Beach, FL USA
Mars Observer Press Conference
Aug. 25, 1993; In English; Videotape: 18 min. 5 sec. playing time, in color, with sound
Report No.(s): NONP-NASA-VT-2000081551; No Copyright; Avail: CASI; B02, Videotape-Beta; V02, Videotape-VHS
Footage shows Bob MacMillin, NASA’s Public Information Office, as he introduces the Mars Observer Project Manager,
Glen Cunningham. Glen is shown addressing the current status of the Mars Observer communication system, the inability of
NASA to establish contact, and the action that is currently being taken to establish contact with the spacecraft. Glen is also seen
answering questions from both the audience as well as other NASA Centers.
CASI
Conferences; Mars Observer
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