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Comment on the paper 'On the influx of small comets into the earth's upper atmosphere. II - Interpretation' by L. A. Frank, J. B. Sigwarth and J. D. CravenThe proposal by Frank et al. (1986) that clouds of small comets periodically inject large amounts of H2O into the upper atmospheres of the earth, Venus, and Mars is examined critically, with a focus on transport and disposal mechanisms invoked to account for the large H2O masses involved. It is argued that observed parameter values (such as mixing ratios, vertical wind velocities, and H escape flows) prohibit transport by eddy, molecular diffusion, vertical avection, or coherent movement. In a reply by Frank et al., these objections are discussed in terms of an overall description of the decelerataion and penetration of a cometary water cloud, and H2O concentrations and mixing mechanisms consistent with observed values for the earth are proposed. It is suggested that an increase in cometary H2O influx could lead to concentrations attaining the frost point and to formation of a global mesospheric cloud with significant climate effects. A lower H2O influx rate for Venus (consistent with observed H loss and atmospheric H2O concentration) and relatively rapid loading of the Mars surface and atmosphere with H2O ice and vapor (followed by brief warming periods with increased exospheric H2O outflow and surface flow of liquid H2O) are considered.
Document ID
19860059680
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Donahue, T. M.
(Michigan, University Ann Arbor, United States)
Date Acquired
August 12, 2013
Publication Date
June 1, 1986
Publication Information
Publication: Geophysical Research Letters
Volume: 13
ISSN: 0094-8276
Subject Category
Lunar And Planetary Exploration
Accession Number
86A44418
Funding Number(s)
CONTRACT_GRANT: NSF ATM-85-20653
CONTRACT_GRANT: NAG5-483
CONTRACT_GRANT: NGL-16-001-002
CONTRACT_GRANT: N00014-85-K-0404
Distribution Limits
Public
Copyright
Other

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