PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011

FOR RELEASE FRIDAY, APRIL 26

       Magellan scientists at NASA's Jet Propulsion Laboratory are studying the surface features on Venus caused by wind in that planet's dense atmosphere, Project Scientist Steve Saunders said today.

       The movement of dust and sand is an important geological process on planets with atmospheres, he said. The surface pressure of Venus' atmosphere is 90 times that of Earth's.

       Soviet landers and the U.S. Pioneer probes measured wind speeds near the surface of Venus at 2 to 4 miles per hour (1 to 2 meters per second).

       Based on theory and lab experiments, that wind speed is very close to the speed required to move sand grains on Venus, Saunders said. Accumulations of blown sand and dust can blanket large regions and produce visible patterns in the Magellan radar images, he said.

       "The most prominent wind features in the Magellan images of Venus are wind streaks," he said. "Streaks form in the lee of topographic obstacles by the deposition or removal of sand and dust and can be used as indicators of the direction of the most intense winds."

       Many large impact craters on Venus have nearby wind streaks which may have been caused by the violent winds generated during the impact event or that may be the result of a slower process of subsequent wind movement of the fine impact debris.

       Magellan has mapped more than 78 percent of the planet and by the time the primary mission cycle ends May 15, will have mapped about 84 percent, project officials said.

       Project Manager Tony Spear said a newly adopted strategy to protect the spacecraft from the heat of direct sunlight has been successful in cooling the spacecraft.

       Magellan has been growing warmer as a result of changes in the geometry of Venus, Earth and the sun and the time the spacecraft spends broadside to the sun. A strategy, called "two hide" which results in slightly shorter imaging swaths, protects the spacecraft by hiding it behind the large antenna, and by turning the solar panels away for periods of time to reduce reflection.

       The Magellan Project is managed by JPL for NASA's Office of Space Science and Applications.

Editors: Two Magellan radar images illustrating the news release are now available at the JPL Public Information Office.


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4/25/91 JJD
#1372