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Science 27 October 1989:
Vol. 246. no. 4929, pp. 506 - 509
DOI: 10.1126/science.246.4929.506
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Articles

The Nature of the Near-Infrared Features on the Venus Night Side

D. CRISP 1, W. M. SINTON 2, K. -W. HODAPP 2, B. RAGENT 3, F. GERBAULT 4, J. H. GOEBEL 5, R. G. PROBST 6, D. A. ALLEN 7, K. PIERCE 8, and K. R. STAPELFELDT 8

1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109.
2 Institute for Astronomy, University of Hawaii, Honolulu, HI 96822.
3 San Jose State University Foundation, San Jose, CA 95192.
4 Sterling Software, National Aeronautics and Space Administration (NASA), Ames Research Center, Moffett Field, CA 94035.
5 NASA Ames Research Center, Moffett Field, CA 94035.
6 Kitt Peak National Observatory, Tucson, AZ 85726.
7 Anglo-Australian Observatory, Epping, NSW, Australia.
8 California Institute of Technology, Pasadena, CA 91125.

Near-infrared images of the Venus night side show bright contrast features that move from east to west, in the direction of the cloud-top atmospheric superrotation. Recently acquired images of the Venus night side along with earlier spectroscopic observations allow identification of the mechanisms that produce these features, their level of formation, and the wind velocities at those levels. The features are detectable only at wavelengths near 1.74 and 2.3 micrometers, in narrow atmospheric windows between the CO2 and H2O bands. The brightest features have brightness temperatures near 480 Kelvin, whereas the darkest features are more than 50 Kelvin cooler. Several factors suggest that this radiation is emitted by hot gases at altitudes below 35 kilometers in the Venus atmosphere. The feature contrasts are produced as this thermal radiation passes through a higher, cooler, atmospheric layer that has horizontal variations in transparency. The 6.5-day east-west rotation period of the features indicates that equatorial wind speeds are near 70 meters per second in this upper layer. Similar wind speeds have been measured by entry probes and balloons at altitudes between 50 and 55 kilometers in the middle cloud layer. The bright features indicate that there are partial clearings in this cloud deck. The presence of these clearings could decrease the efficiency of the atmospheric greenhouse that maintains the high surface temperatures on Venus.

Submitted on May 24, 1989
Accepted on September 15, 1989


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Images from Galileo of the Venus Cloud Deck.
M. J. S. Belton, M. J. S. BELTON, P. J. GIERASCH, M. D. SMITH, P. HELFENSTEIN, P. J. SCHINDER, J. B. POLLACK, K. A. RAGES, A. P. INGERSOLL, K. P. KLAASEN, et al. (1991)
Science 253, 1531-1536
   Abstract »    PDF »
Ground-Based Near-Infrared Imaging Observations of Venus During the Galileo Encounter.
D. Crisp, D. CRISP, S. MCMULDROCH, S. K. STEPHENS, W. M. SINTON, B. RAGENT, K. -W. HODAPP, R. G. PROBST, L. R. DOYLE, D. A. ALLEN, et al. (1991)
Science 253, 1538-1541
   Abstract »    PDF »
Galileo Infrared Imaging Spectroscopy Measurements at Venus.
R. W. Carlson, R. W. CARLSON, K. H. BAINES, TH. ENCRENAZ, F. W. TAYLOR, P. DROSSART, L. W. KAMP, J. B. POLLACK, E. LELLOUCH, A. D. COLLARD, et al. (1991)
Science 253, 1541-1548
   Abstract »    PDF »
The Galileo Venus Encounter.
T. V. JOHNSON, C. M. YEATES, R. YOUNG, and J. DUNNE (1991)
Science 253, 1516-1518
   Abstract »    PDF »
The dark side of Venus: near-infrared images and spectra from the Anglo-Australian observatory.
D Crisp, D. Allen, D. Grinspoon, and J. Pollack (1991)
Science 253, 1263-1266
   Abstract »    PDF »
Spectroscopic Observations of Bright and Dark Emission Features on the Night Side of Venus.
J. F. BELL III, D. CRISP, P. G. LUCEY, T. A. OZOROSKI, W. M. SINTON, S. C. WILLIS, and B. A. CAMPBELL (1991)
Science 252, 1293-1296
   Abstract »    PDF »


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