Pay Dirt from the Moon

Pay Dirt from the Moon The crew of Apollo 11, the first men on the moon, brought back only 481 Ibs. of lunar rocks and dust. But even that small sampling from the Sea of Tranquillity has been enough to keep 142 scientists in the U.S., Canada, Japan, Australia and Western Europe fully occupied in their laboratories since late last summer. In Houston last week, at a symposium sponsored by NASA, the lunar investigators finally took time out from their work to report on what they had learned so far. Their findings add a vast store of fresh knowledge about the earth's nearest celestial neighbor, but leave unanswered most of the puzzling questions about the moon's origin and evolution.

Hot v. Cold. One of the more surprising revelations at the symposium was the age difference between the dust and the rocks found at Tranquillity Base. Using dating methods based on the decay of radioactive elements, scientists determined that, although the dust particles were 4.6 billion years old --the apparent age of the moon itself --most of the rocks were about 1 billion years younger. How could there be such a huge age gap between material picked up only a few feet apart? "This is a major puzzle," says Rice University Geologist Dieter Heymann. One small rock fragment, though, was considerably older than the others: 4.44 billion years. Caltech Geologist G. J. Wasserburg, who calculated its age, believes that still older rocks dating back to the very creation of the moon will probably be found in the unexplored lunar highlands.

Examination of the lunar rocks also established that catastrophic events rocked the moon about a billion years after its creation. "There were definitely lava flows 3.65 billion years ago," says Wasserburg. Scientists are still uncertain whether the lava rose from a hot lunar interior or was created by heat from the impact of huge meteorites. If the melting was indeed caused by meteors, a similar process might have occurred on the nearby earth. This could explain why scientists have been unable to find any terrestrial rocks older than 3.6 billion years--although the earth, too, is believed to be 4.6 billion years old.

Making Tracks. There were also some smaller surprises. Examining the lunar material with scanning electron microscopes, scientists observed that even the tiniest granules were cratered by micrometeorite bombardment. They also saw miniaturized versions of the larger glassy spheres spotted and collected by the Apollo astronauts; they were apparently formed by splashes of hot debris from meteorite impacts. Several scientists showed electron micrographs of pyroxenes (a mineral also found on earth) that had crystallized in a remarkable candy-stripe pattern. The investigators also saw tiny tracks produced in the rocks by the bombardment of cosmic ray and solar particles. Made millions and even billions of years ago, these markings are permanent records of the sun's activity. From them, scientists may learn, for example, if the earth's ice ages were in fact caused by long periods of reduced solar output.

Gold and Rubies. The Tranquillity Base rocks yielded small traces of at least three new minerals unlike any on earth--all of which contained iron. Remembering the man who launched the Apollo program, some scientists suggested naming one of the new minerals Kennedyite. Scientists were also intrigued by traces of gold and rubies. But the University of Chicago's Edward Anders quickly cooled off any ideas of lunar prospecting. "The amount," he said, "is much too small to finance the space program."

Little excitement was stirred by the reports that carbon and even amino acids --the building blocks of protein--had been found in the Sea of Tranquillity samples. Scientists pointed out that at least some of the carbon had probably come from meteorites and that the rock samples may well have been contaminated with amino acids during laboratory examinations. "It can be inferred," said Harvard Biologist Elso Barghoorn, that the top layer of the moon "has never possessed life and is inimical to life."

Despite some similarities of composition and age, the Apollo findings make the moon seem less and less like the earth. No rumblings have been detected in its interior; the chemicals and minerals found on the lunar surface are significantly different from those of the earth. Columbia University Geochemist Paul Cast called the moon "a cinder --dehydrated and formed at a high temperature so that it has lost its water, if indeed it ever had very much." The disparities are so great that most scientists have now all but abandoned the theory that the moon was torn from the earth.

Then how was the moon created? Scientists think that significant evidence may lie in the lunar highlands, which apparently have changed little since the moon was born. The quest for such evidence will begin when Apollo 13 sets down in a highland area near the crater Fra Mauro. The setdown will not be as soon as originally planned. Partly because of criticism by scientists that they did not have enough time for research and planning between moon flights, the space agency last week deferred the scheduled March 12 mission until April 11.

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