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Mass spectrometric measurements of the neutral gas composition of the thermosphere and exosphere of VenusThe neutral gas composition and density in the thermosphere of Venus is being measured with a quadrupole mass spectrometer on the Pioneer Venus orbiter. Data are obtained near periapsis once per day approximately 150-250 km above the surface. The principal gases in the thermosphere are CO2, CO, N2, O, N, and He. Atomic oxygen is the major constituent above 155 km on the dayside and also on the nightside up to 180 km when helium becomes the major constituent. The average values of CO2, CO, N2, O, and N remain nearly constant during day and night, but an abrupt change occurs across the terminator from a high dayside value to a low nightside value. The helium density varies in the opposite way, and a distinct bulge was observed at night near the morning terminator. The data have been used as the basis of an empirical model. Large orbit to orbit variations in densities were also observed on the nightside, suggesting perhaps strong turbulent motion in the atmosphere below. Kinetic temperatures inferred from scale heights are approximately 285 K on the dayside and 110 K at night. The average global temperature obtained from the model is 199 K.
Document ID
19810042393
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Niemann, H. B.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Kasprzak, W. T.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Hedin, A. E.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Spencer, N. W.
(NASA Goddard Space Flight Center Laboratory for Planetary Atmospheres, Greenbelt, Md., United States)
Hunten, D. M.
(Arizona, University Tucson, Ariz., United States)
Date Acquired
August 11, 2013
Publication Date
December 30, 1980
Publication Information
Publication: Journal of Geophysical Research
Volume: 85
Subject Category
Lunar And Planetary Exploration
Accession Number
81A26797
Distribution Limits
Public
Copyright
Other

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