Scientists Say Mars Has Continents And Ocean Beds Resembling Earth

Two Harvard scientists have found that the dark areas of Mars rise six to nine miles above the brighter deserts, contradicting the standard theory that Mars is an almost smooth planet.

In the traditional view, the dark areas of Mars are considered lowlands, with bright sectors a mere mile or so higher. But Carl E. Sagan, assistant professor of Astronomy, and James B. Pollack of the Smithsonian Astrophysical Observatory, have reversed the roles of dark and light areas. And the highland, they say, are far more than a mile above "sea" level.

They also suggest that atmospheric pressure in the dusty lowlands is higher than previously believed -- high enough for a spacecraft to make a soft landing with a parachute instead of the more complex retro-rockets.

"Our new picture of Mars," Pollack said yesterday, "is much like the Earth without oceans." The dark areas are contintents, and the bright areas are dry ocean basins. There are differences, of course: Mars can support higher mountains because it has less gravity, and it overed with a thick layer of dust.

Mars has continents, Pollack continued, it must have geological activity, too. Just as on the Earth, there must be forces within the planet that have molded the surface, pushing the continents above the deserts.

This continent theory may destroy the idea that the place to look for life on Mars is in the dark regions. Because water boils at a lower temperature at lower pressures, there is little chance that water could ever exist in the liquid form in the low-pressure dark areas. In the light areas. Pollack suggested, liquid water might exist for an hour or two a day. That becomes a more likely place to look for life.

The classical reasons for suspecting that life is in the dark somes is ambignous, Pollack paid. It is known that dark areas become darker in the spring, while the polar caps are evaporating. So, the old 'theory goes, this must be increased vegetation.

"From this far away," Pollack mused, "it's easy to be ingenious." But there is no real basis for believing the darkness on Mars is vegetation. Sagan and Pollack suggest instead that in the spring, some dust is blown off the continents, sharpening the contrast between the dark high-lands and the surrounding bright deserts.

The findings are based on analysis of radar, infrared, and other observations of Mars, much of it conducted with the 85-foot radio telescope of the Jet Propulsion Laboratory.

No Shadows

Sagan and Pollack say the dark high-lands have escaped optical detection because their long, gentle slopes and relatively level tops preclude any shadows or reflection of sunlight.

The new mapping of light and dark solves at least one meteorological mystery. During violent dust storms, no dust ever gets into the dark areas. Sometimes dust comes right up to a dark area and appears to bounce back suddenly. This would be difficult to explain if the dark areas were lowlands, Pollack said. But it fits perfectly if the dark areas are high plateaus which turn away dust streams