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Science 29 July 1983:
Vol. 221. no. 4609, pp. 453 - 455
DOI: 10.1126/science.221.4609.453
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Articles

Uranus: Variability of the Microwave Spectrum

S. GULKIS 1, E. T. OLSEN 1, M. J. KLEIN 1, and T. J. THOMPSON 2

1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena 91109
2 Ball Aerospace Systems Division, Western Laboratories, Huntington Beach, California 92647

Radio astronomical observations of Uranus show that the radio emission spectrum is evolving in time. Ammonia vapor must be depleted in the Uranian atmosphere as Gulkis and his co-workers previously suggested. Since 1965, ammonia either has been decreasing in time or is a decreasing function of latitude, or both, provided that the radio emission is atmospheric in origin. If Uranus has an observable low-emissivity "surface," these trends may be reversed. The microwave observations made in 1965, at the time when the spin axis of Uranus was nearly perpendicular to the sun-Uranus line, are consistent with an atmospheric opacity profile that would be produced by saturated ammonia vapor in a predominantly hydrogen atmosphere. At the present time, when the spin axis of Uranus is nearly aligned with the sun-Uranus line, the measurements require an opacity that would be produced by saturated water vapor. A large thermal gradient between the pole and equator is ruled out.

Submitted on December 27, 1982
Revised on April 18, 1983


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Uranus: microwave images.
W. Jaffe, G. Berge, T Owen, and J Caldwell (1984)
Science 225, 619-621
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