Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published October 27, 1989 | public
Journal Article

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


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 CO_2 and H_2O 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.

Additional Information

© 1989 American Association for the Advancement of Science. 24 May 1989; Accepted 15 September 1989. We thank K. Baines, M. McKelvey, J. Hester, C. Beichman, T. Soiffer, K. Matthews, J. Lugten, J. Malliard, H. Larson, and others for assisting with our 1988 observing program. We also thank H. Brinton for his encouragement and support. This work was funded in part by grants from the National Aeronautics and Space Administration (NASA) Planetary Astronomy and Planetary Atmospheres Programs to the NASA Ames Research Center and the Jet Propulsion Laboratory (JPL), California Institute of Technology, and grant NGL 12-001-057 to the University of Hawaii. The infrared array used in Hawaii was the product of work by the JPL Infrared Technology Group in support of the Spaceborne Imaging Spectrometer Project Office, under funding from the NASA Office of Space Science and Applications. Contribution 4756 from the Division of Geological and Planetary Sciences, California Institute of technology.

Additional details

August 19, 2023
October 19, 2023