When the first moon rocks were returned to Houston's Lunar Receiving Laboratory 10 years ago, scientists fully expected they would reveal a lifeless history that started and stopped when the moon was formed.
Nothing could have been further from the truth. It was indeed without life, water and oxygen. But the 842 pounds of the moon that 12 Apollo astronauts collected at six different places showed without doubt that the moon had suffered a tumultuous past. The rocks showed that the moon formed hot 4.6 billion years ago and stayed hot for at least 500 million years. Next, they showed that the moon was struck by asteroids, some the size of Rhode Island, for 200 million years and then oozed molten lava for another 800 million years before finally starting to cool down 3 billion years ago.
The facts of the moon's early life brought scientists to the inescapable conclusion that the Earth underwent the same kind of tortured history, a long-held theory that could never have been substantialed without the moon rocks.
The oldest rocks found on Earth date back 3.8 billion years; Earth's air and water had long erased the earlier 800 million years of our history. Not so with the moon, whose lack of air and water preserved its rocks in what is almost primeval form. Events as old at 4.2 billion years can still be read in the lunar rocks brought home by the Apollo Astronauts, thus filling in 400 million years of missing solar system history.
"There's no amount of money we could have spent here on Earth, no matter how far we drilled into the Earth, to find this out," said Dr. Bruce Murray, director of the Jet Propulsion Laboratory in Asadena and an early lunar expert. "We could never get the information we got back about the Earth from these lunar samples."
Put simply, the moon rocks revolutionized cosmologic thought. No longer is there any doubt that the entire solar system suffered the white heat of creation for the first 500 million years, then a shorter period of catastrophic collision and a longer period of volcanism brought on by radio-active rock decay.
While it sounds straightforward, awareness of this chain of events has changed the course of planetary science.Taught at a handful of schools 10 years ago, planetary science departments have spread to a dozen, including Harvard University, MIT, CAL Tech, Minnesota, Chicago, The University of Arizona and the State University of New York.
The Viking missions to Mars were changed by the moon rocks. The two recent Voyager excursions by Jupiter were influenced enormously -- both spacecraft were ordered to look long and hard at the four large moons of Jupiter because of what science learned from the moon rocks.
More important, the moon rocks changed the earthbound science of geology. The biggest increase in attendance at the annual Lunar Science Symposium has come from corporations like Kennecott Copper and International Nickel, whose geologists travel to Houston every year to hear more about the unraveling story of the moon rocks. Prospecting geologists now search for oil, gold, silver and other metals based on what they have learned about the distribution of minerals on the moon.
One of the largest sources of nickel anywhere in the world lies in the Sudbury Basin in Ontario, which was probably formed by a meteorite impact millions of years ago. The question: Did the meteorite bring the nickel from space or did the impact cause later volcanism that brought the nickel out from the Earth's interior? The answer could be crucial to exploration and exploitation of the basin.
"The moon rocks have made people think differently than they did 10 years ago," said Harold Masursky of the U.S. Geological Survey, a pioneer in the study of the moon. "There is far more emphasis on the study of the earliest stages of the earth's formation."
The Apollo astronauts brought back 2,000 moon rocks, which have since been cut up into 60,000 individual samples. No fewer than 12,000 samples are under study right now in 85 laboratories in the United States, Canada, Germany, France, Japan, Australia and India.
Many of the remaining 48,000 fragments have been examined as many as five times by an estimated 2,000 scientists around the world, including some in the Soviet Union. Most rocks are returned to Houston's Lunar Receiving Laboratory after they have been studied. An exception is the six samples given to the Soviet Union, which in exchange gave the United States traces of three samples its robot spacecraft dug out of the lunar soil.
In all their travels from laboratory to laboratory, only one lunar sample has been lost. That was a one-ounce fragment lost in the theft of a mail bag on its way to the State University of New York at Stony Brook in 1970. As far as anybody knows, the thief threw away the rock, not knowing what it was.
Before the moon rocks were brought to Earth, almost nothing was known about the moon except for its size, shape and color. Scientists learned quickly from the rocks why the moon's dark seas are black. The seas are lava lakes that began to pour out from the lunar interior about 4 billion years ago and then stopped flowing about 3 billion years ago.
"Until the rocks came back, we'd been looking through a glass darkly," said Dr. Gerald Wasserberg of the California Institute of Technology. "Nobody thought the moon had a heat engine, and when we found that it did, nobody could believe it had a heat engine that could be turned off. That discovery changed everything."
Among the many surprises revealed by the moon rocks is the fact that the moon formed about 100 million years after the Earth and at a higher temperature. Another surprise was the fossil magnetism present in almost all the moon rocks, even though the moon possesses no dynamo today to give its rocks any magnetism.
"What I'd been told years ago was that if a planet was dynamic enough to have an internal dynamo, it will never lose it," said the U.S. Geological Survey's Masursky. "Well, dammit, that thing ran down, the moon had a dynamo and lost it."
Despite all the things the moon rocks taught scientists they left unanswered the question of whether the moon was once a piece of the Earth or formed separately only to be caught by the Earth's gravitational pull. Even the fact that the moon may be younger than the Earth doesn't answer that question, which may be debated until the end of time.