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Io's atmosphere - Pressure control by regolith cold trapping and surface ventingA new model for the basal pressure of Io's atmosphere is developed. This model takes into account the previously ignored fact that much of Io's surface has very high porosity, typically about 90 pct. Such porosity allows efficient subsurface cold trapping of atmospheric gases which tends to keep ambient surface pressures very low. SO2 is the only gas identified on Io, and the basal pressures for atmospheric models are usually pegged to local surface temperature via the SO2 vapor pressure equilibrium curve. Near Io's subsolar point the pressure in equilibrium with a surface SO2 frost deposit is about 1/10,000,000th bar. Porous surface models of the type developed invoke equilibrium with the colder, subsurface permafrost (at about 3-cm depth) and yield pressures of about 1/10 to the 12th bar. The subsurface cold trapping model explains many but not all observations relevant to Io's atmosphere. The new subsurface cold trapping model and the earlier surface frost equilibrium model, when taken together, provide lower and upper limits, respectively, on the basal SO2 pressure of Io's atmosphere.
Document ID
19830052713
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Matson, D. L.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Nash, D. B.
(California Institute of Technology, Jet Propulsion Laboratory, Earth and Space Sciences Div., Pasadena CA, United States)
Date Acquired
August 11, 2013
Publication Date
June 1, 1983
Publication Information
Publication: Journal of Geophysical Research
Volume: 88
ISSN: 0148-0227
Subject Category
Lunar And Planetary Exploration
Accession Number
83A33931
Funding Number(s)
CONTRACT_GRANT: NAS7-100
Distribution Limits
Public
Copyright
Other

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