Where There's Hope There May Be Life

Hope that a future astronaut might some day find life on Mars faded deeper than ever into science fiction when Mariner 4 sent its remarkable snapshots across 135 million miles of space. The bleak, pocked surface of the red planet looked dead indeed. Because they saw no signs of erosion, space specialists from Caltech's Jet Propulsion Laboratories, who had directed the Mariner voyage, concluded that Mars probably never had any significant amount of life-supporting water. Though they were not quite ready to deny the possibility of Martian life, the JPL men seemed all but certain that what they could not see was not there.

Not so, claim more optimistic scientists after a second look at the Mariner photos. The JPL men assumed that the surface of Mars is as old as the surface of the moon, say Physicists Edward Anders of the University of Chicago and James R. Arnold of the University of California, San Diego. If that were so, the two men argue in the latest issue of Science, Mars would show many more craters than it appears to have. Assuming a fairly constant supply of crater-forming asteroids, Mars, which is far closer to the asteroid belt, would have been hit up to 25 times more often than the moon. There would be as many as 220 craters per 1,000,000 sq. km., not the meager 37 that have been observed.

In the same issue of Science, other researchers offer much the same conclusion. All of which suggests that other Martian craters, predating those that Mariner saw, formed and vanished eons ago. What happened to them? All the researchers agree that they must have been eroded away -- perhaps by swirling dust storms, perhaps by a flow of Martian water. "In any event," conclude Anders and Arnold, "the crater density on Mars no longer precludes the possibility that liquid water and a denser atmosphere were present on Mars during the first 3.5 billion years of its history." If there was water, there may have been life. And if Mars once supported some form of life, it still may.

Even the director of the Mariner 4 project is not yet willing to rule out the possibility. Says JPL's Dr. William H.Pickering: "The very fact of the infinite varieties of life on earth should preclude our jumping to the conclusion that there could be no life on Mars. The Mariner pictures make it a little more doubtful. But I still assume that there may be some life forms there, however rudimentary."

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