Of Mars and the Moon

The geological record of the earth's beginnings has been largely obliterated by erosion, volcanic activity, earthquakes and even the shifting of continents. Thus, scientists have looked with increasing eagerness to other celestial bodies for clues as to how their own planet was formed. Last week they were rewarded with a new bonanza of evidence. It came in the form of the most remarkable photographs yet taken of the planet Mars and a trove of fresh data from the last two missions to the moon.

Vistas of the Red Planet

For weeks, Mariner 9's mission controllers at the Jet Propulsion Laboratory in Pasadena had fretted more about the weather on Mars than about meteorological events on earth. Finally, the giant dust storm that was partially blinding the orbiting spacecraft's television eyes subsided. In the past few days, almost every picture sent back by the robot has been, in the words of Astronomer Bradford Smith, truly "a gem," showing vistas of the red planet never before glimpsed by man.

The pictures have also evoked new mysteries. One frame reveals strange dark splotches that Cornell Astronomer Carl Sagan calls "leopard spots." He thinks that they may be areas where high winds have blown off some of the planet's lighter, more reflective dust cover. The same effect may create the seasonal "wave of darkening" that was once widely regarded as a sign of earth-like vegetation on Mars.

Another photograph shows long (up to 1,100 miles) canyon-like rilles --parallel features that may have started all the theories about Martian "canals." More likely, astronomers say, they are huge fractures in the Martian surface that occurred when internal forces lifted up a plateau region. Even more detailed evidence of the red planet's interior creaking and groaning came in a shot of the Nix Olympica region. There Mariner's cameras not only found the possible remains of an ancient Martian volcano but also revealed what may be finely textured lava flows on its slopes.

The photographs make it seem more likely than ever that the surface of Mars underwent violent changes as recently as a billion years ago. They also provide important new clues to the planet's present condition. Near the Martian south pole, Mariner 9's cameras photographed several "etch pits," basins up to ten miles in diameter that are similar to depressions found on earth in regions where subsurface ice or permafrost has melted, evaporated and caused cave-ins. If these Martian features were in fact caused by the presence of ice, it would mean that there may once have been more water on the planet than hitherto believed. Because water is essential for biological activity as man knows it, the discovery of ice on Mars would raise hopes of finding vestiges of some form of life there.

A Lunar Jamboree

In Houston, it was not Mars but the moon that was on the minds of nearly 700 scientists who gathered at the Manned Spacecraft Center for the third lunar science conference. For most, it was a highly profitable trip. The conferees exchanged reams of data from last year's flight of Apollo 14 and received more recent information from the instruments taken to the moon by the Apollo 15 astronauts. Among other things, the scientists were told that the moon, as measured by temperature probes placed in the lunar surface, seems to be giving off heat at twice the rate of the earth, though skeptics suggested that instrument malfunction may have caused the surprisingly high readings. The moon may also be racked by minor volcanic eruptions ("But her heartbeat is feeble indeed," cautioned Seismologist Gary Latham of Columbia University).

Though only indirect evidence has been found in lunar rocks, the moon apparently once had a magnetic field. Finally, the differences in composition between the lunar highlands and the moon's maria are somewhat similar to those between the earth's relatively lightweight continents and its denser deep-sea floor.

What does it all mean? For one thing, the evidence continues to refute the old theory that the moon's interior is cold and geologically inactive. More important, the findings hint that the moon, like the earth, probably was formed out of the collisions of countless chunks of primordial material. Shortly thereafter the newborn moon was rapidly heated, possibly by its radioactive elements, and underwent surface melting about 4.5 billion years ago. In contrast with delegates to previous "rock conferences," the experts assembled this year were unusually reticent about advancing new theories on the moon's evolution. Said Geochemist Paul Cast, chief lunar scientist at the Manned Spacecraft Center: "We have so much data to examine that the boys just aren't doing much speculating." Added NASA Geochemist Robin Brett: "The Apollo 15 material alone will keep us busy for about five years."

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