Venus Thermosphere and Exosphere: First Satellite Drag Measurements of an Extraterrestrial Atmosphere

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Science  23 Feb 1979:
Vol. 203, Issue 4382, pp. 772-774
DOI: 10.1126/science.203.4382.772


Atmospheric drag measurements obtained from the study of the orbital decay of Pioneer Venus 1 indicate that atomic oxygen predominates in the Venus atmosphere above 160 kilometers. Drag measurements give evidence that conditions characteristic of a planetary thermosphere disappear near sundown, with inferred exospheric temperatures sharply dropping from approximately 300 K to less than 150 K. Observed denisities are generally lower than given by theoretical models.