The View from Mariner

A typical Southern California haze hung over Pasadena last week, but at the Jet Propulsion Laboratory there was much less concern about the local weather than about conditions on Mars, some 80 million miles away. As scientists monitored the pictures and scientific data being transmitted from Mariner 9, in its second week in orbit around the distant planet, Mars was still enshrouded in a raging dust storm. While apparently beginning to subside, the giant duster will probably obscure much of the surface for weeks to come. Faced with the growing possibility that the Martian skies will not clear up completely during Mariner's planned three-month photography mission, JPL controllers fed a new temporary "shooting script" into the spacecraft's onboard computer, thus enabling Mariner's twin TV cameras to look for holes in the cloud cover.

That improvisation quickly produced rewards. Mariner found an opening in the dust clouds near the south polar cap and managed to get another look at an area that had been marked by long, frost-covered ridge lines and craters during the flybys of Mariners 6 and 7 in 1969. To the surprise of scientists, the pictures showed that the ridge lines were no longer covered by frost, many craters had vanished entirely, and the surface was remarkably smooth. Said Astronomer Bradford Smith: "This whole area looks like it's been planed off." Some scientists speculated that the most logical explanation for the change was that the surface had been scoured by glaciers as the polar cap grew during Martian winters and then receded again.

Photographing Deimos. There was disagreement about the composition of the glaciers. Carl Sagan, director of Cornell University's Planetary Studies Lab, suggested that the glaciers are frozen carbon dioxide (dry ice), the major constituent of the polar cap. Smith felt that dry ice would not flow like a glacier. "The only thing that does," he said, "is water." Mariner's instruments did detect water vapor in the atmosphere above the south polar cap, suggesting that it had risen from the ice below. Those readings encouraged scientists who still hope to find some form of ife, however rudimentary, on the desolate Martian surface.

Taking its TV eyes off the planet for a while, Mariner demonstrated its versatility--and the skill of its terrestrial controllers--by spotting and photographing the outer Martian moonlet, Deimos, from a distance of more than 5,000 miles. Deimos, a tiny chunk of debris only 5 1/2 miles by 7 miles, seemed to be flattened in its northwest quadant, appearing to one JPL observer "like half an apple with a bite taken out of it." It also had unexplained light splotches and other surface features that may show up more clearly when JPL technicians use computers to enhance the photograph.

Mysterious Silence. Despite the storm, readings taken by Mariner's infrared spectrometer enabled JPL investigators to identify several earthlike minerals in the Martian crust, including quartz, granite and anorthocite. Those findings caused considerable excitement among the scientists. They indicated that Mars had at one point in its history undergone melting and that lighter elements had floated to the surface, later hardening into an earthlike crust. Included among the lighter elements are carbon compounds that were necessary for the development of life on earth. Said NASA Exobiologist Jerry Soffen, who is project scientist for the Viking program that will make a purposeful attempt to find life on Mars in 1976: "There can't be biological evolution if there is not geological differentiation."

Other findings reported by Mariner included atmospheric pressure and temperature readings, irregularities in the gravity field and a description of the bulge around Mars, which gives the planet 1.2 miles more girth at the equator than at the poles.

The Russians, for their part, continued to maintain a mysterious silence about the progress of their twin craft Mars 2 and Mars 3. Western scientists had expected Mars 2 to arrive at the red planet by week's end. Mars 3 five days later. As the days passed without any word from Moscow, there was growing concern that the first of the two Russian craft might have failed to go into orbit around Mars and sped by into distant space.

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