Postcards from Another World

Scientists mull over a colorful scrapbook from Mars

On June 19, 1976, an alien vessel, hurtling toward Mars, blasted its remaining rocket engine and moved into an elliptical orbit. It was the first of twin Viking spacecraft, each with an orbiter and a lander, launched by NASA to help satisfy man's curiosity about the possibilities of life on the planet. The Viking I orbiter's immediate chore was to survey the Martian surface and transmit pictures of potential landing sites. Once the lander was safely down (on July 20, 1976), the orbiter began snapping away at its aerial photographic study.

More than two years later, space scientists are still analyzing the Viking data and pictures. There is no consensus yet on the possible presence of life. But the pictures themselves are masterworks of unearthly beauty. This week many will be unveiled for the first time, and the data thoroughly discussed, at the Second International Colloquium on Mars at the California Institute of Technology.

The picture above shows the planet's great northern volcano, Olympus Mons, the largest known to man. Its multiringed crater measures some 50 miles across and towers 15 miles above a base that stretches for some 375 miles, roughly the distance between San Francisco and Los Angeles. The volcano was observed from a height of 5,000 miles on a Martian morning in midsummer. The clouds rimming the volcano are seasonal, limited to spring and summer; scientists postulate that they may be formed when ice condenses from the atmosphere as it cools while moving up the crater's flanks. Hovering beyond, at the upper left corner of the photograph, is a "cloud train," a common formation on the downwind side of mountains.

The Olympus Mons picture is actually not a single photo but a mosaic of small ones. Mechanical shutters on the Viking cameras snap a stream of images that are broken into their constituent colors by a series of filters. Eventually an electronic beam scans the resulting image, translates it into tiny electrical impulses (8.7 million per photo) and sends them to earth.

For now, scientists will have to be satisfied with pictures of the mysterious Red Planet, rather than an eyewitness view; NASA's dream of sending man to Mars has been dashed by earthly budget cuts. At the 145th national meeting of the American Association for the Advancement of Science last week in Houston, Edward C. Ezell, a space historian, argued that the manned-flight blueprints at least be kept for future generations. Some day, he said sadly, "the dreamer quality of science" will be restored.

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