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MAY 20, 1988

       Newly processed radar pictures of the surface of Venus show what may be geologically recent volcanic activity and impact cratering, including possible volcanic mountains and broad lava flows and fields like those which make up the Hawaiian Islands, JPL scientists have reported.

       Bright rings, seen in highland regions on Venus, are believed to be material thrown out from below the surface by volcanoes or by meteor impacts.

       The observations were published today in Science magazine by Drs. Raymond F. Jurgens, Martin F. Slade, and R. Stephen Saunders, radar and planetary scientists at JPL.

       The areas of intense radar brightness or reflectivity, nearly four times brighter than most of Venus, could be extremely dense volcanic rocks, or electrically conductive minerals like iron pyrite which would reflect microwaves, or combination of both. Dark spots, notably in the centers of craters, might be too mirror-smooth or too rough to scatter microwaves back to the angled radar.

       The JPL radar images, with resolution of less than mile, are the latest and best in long series taken using planetary radar antennas at the Goldstone, California complex of NASA's Deep Space Network. The DSN is generally used to track and control planetary spacecraft such as Voyager.

       The Goldstone radar was the first to make these high-resolution pictures near the equator of Venus, though similar radar observations around the planet's north pole were made by Soviet Venera spacecraft in 1983.

       The Goldstone data were the first to link the bright crater halo rings with the lowland patches. The irregular bright patches are much larger than most craters, up to hundreds of miles across, and may be volcanic flows and lava fields.

       The surface of Venus cannot be observed in the visible light spectrum because of thick clouds which enclose the planet. It has been scanned by Goldstone and other radar observatories such as Arecibo, in Puerto Rico, since the 1960s, but only small areas can be accurately mapped from Earth. U.S. and Soviet spacecraft have generated contour maps and images at various resolutions since the 1970s.

       The best detail will come in 1990 from NASA's Magellan spacecraft mission to Venus. The 100- to 200-yard resolution of Magellan's radar should show these formations clearly, and help scientists determine whether Venus, whose northern territories show many impact craters like the Moon, is also shaped by volcanoes and lava flows as are the Earth, Mars, and Jupiter's satellite Io.

       JPL's planetary radar studies are funded by NASA's Office of Space Science and Applications.

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