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MAY 27, 1980

       NASA's Viking Lander 2, which completed its second winter on the surface of Mars before it quit operating in March 1980, again photographed the appearance of layer of frost or snow on the ground nearby.

       Stephen D. Wall and Kenneth L. Jones reported to the American Geophysical Union's spring 1980 meeting in Toronto today on results of their Martian frost studies.

       As happened during Viking's first winter on Mars, white condensate appeared on the ground very slowly, reaching its maximum thickness of few microns around winter solstice. Pictures show that the layer remained on the surface for about 250 Martian days.

       Wall and Jones said temperature data suggest that, although carbon dioxide is probably significant contributor to the layer, water ice also plays part. The distinction between frost and snow depends, they said, on the role of atmospheric dust in bringing the condensate to the surface. It may be possible to determine from more recent Lander 2 images whether dust was involved.

       Viking Lander 1 has also observed surface changes near its landing site. Two miniature landslides, slumps about 10 centimeters (four inches) across, have occurred, revealing that the Martian landscape is not static, but is constantly being shaped by the wind. No visible soil slumps predate the Viking 1 landing on July 20, 1976, suggesting that annual dust storms on Mars may be strong enough to obliterate the features.

       The Viking landers touched down on the surface of Mars in the summer of 1976, supported by two orbiters that served as relay stations and carried out scientific observations of their own. Viking Orbiter 2 and Viking Lander 2 are no longer active. Orbiter 1 is expected to continue operations into the summer of 1980, and the remaining lander is programmed to continue collecting and transmitting data to Earth through 1990.

       The Viking Project is managed for NASA by the Jet Propulsion Laboratory.

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