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Published: December 1969

First Explorers on the Moon

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What the Moon Rocks Tell Us

By Kenneth F. Weaver
Ektachrome by Neil A. Armstrong, NASA

This article was originally published in the December 1969 issue of the magazine.

“When we opened that first box of moon rocks, the hushed, expectant atmosphere in the Lunar Receiving Laboratory was, I imagine, like that in a medieval monastery as the monks awaited the arrival of a fragment of the True Cross.”

Such keen anticipation, as described by Dr. Robin Brett, a NASA geologist on the team that first examined the lunar samples, is understandable. These were the most sought after, the most eagerly awaited, of all specimens in the history of science. Moreover, as some 500 scientists have labored in recent months to make every conceivable kind of test on them, the moon rocks and soil have become the most intensely studied of all scientific specimens.

At first glance, when the box was opened, the excitement hardly seemed warranted. On that historic moment on July 26, scientists clad in surgeons’ gowns and caps, and carrying gas masks for use in case they should be exposed to any moon dust, crowded together to peer intently through a glass port in the lab’s high-vacuum chamber. From the opposite side of the stainless-steel chamber, a technician working through stiff gloves raised the lid of the sample box and laid back the Teflon bag inside.

“What we saw,” wryly recalls one observer, “was not much different from a bag of charcoal. The rocks were so covered with dark-gray dust that no one could tell a thing about them.”

But later, when the dust was cleaned off and the minerals could be clearly seen, the rocks began to tell their story. It was a story full of surprises. It revealed that no one had been totally right in his ideas of the moon, and it raised more questions than it answered.

Sometime in January, the lunar scientists will gather to report the story of the first moon samples in formal detail. Meanwhile, here are the preliminary highlights, based on interviews with a number of scientists:

  • Moon dust holds no threat to life on earth. The samples show no fossil life, no living organisms, and no organic material (except minute traces believed to be almost entirely contamination from the rock boxes or the lunar laboratory). To test for pathogens, or disease-causing agents, biologists inoculated 200 germ-free mice with finely ground particles of lunar material. These mice had been bred in a completely sterile environment and lacked almost all immunity to disease. Yet they showed no ill effects whatever. This and other experiments indicate that the rock sample containers were no Pandora’s boxes after all, despite early qualms.
  • The age of the Sea of Tranquillity appears to be extremely great—almost as old as the moon itself—to the surprise of many geologists. These rocks, dated by the rate at which radioactive potassium has been converted into argon, seem to have crystallized in their present form about three billion years ago. (The moon, like the rest of the solar system, is estimated to have been formed about 4.6 billion years ago.)
  • High temperatures—higher than 2,200 degrees F.—attended the birth of these rocks. The material filling the Sea of Tranquillity is igneous (fire-formed), and was once molten, but whether it erupted from volcanic fires below the surface or was melted by cataclysmic impacts of meteorites is not settled.
  • The moon is virtually paved with bits of glass, much of it in irregular fragments. Glass makes up fully half of the moon-soil sample brought back to earth. About 5 percent of the glass consists of delicate globules and teardrops that show beautiful shades of brown, green, wine-red, and lemon.
  • Erosion processes that may be like sandblasting have rounded and smoothed the surfaces of rocks. Most of the specimens show tiny glass-rimmed pits or glassy splotches. Is this from a continual rain of meteorites? The explanation is still not clear, says Dr. Paul W. Gast of the Lamont-Doherty Geological Observatory, chairman of the group of scientists in charge of distribution of the moon samples. But the rocks and soil show abundant evidence of impact shock.
  • Any question of surface water in the Sea of Tranquillity at any time since the rocks were first exposed may be dismissed. The rocks are now extremely dry and show no evidence of rounding by water. Moreover, their mineral makeup indicates that the liquid from which the rocks crystallized had negligible amounts of water chemically bound within it.
  • Moon stuff from the Sea of Tranquillity resembles earthly basalt, yet there are no earth rocks just like it. It does have the same constituents—notably oxygen, silicon, iron, aluminum, titanium, calcium, and magnesium—but the proportions are different. For example, Dr. S. Ross Taylor of the Australian National University burned bits of the lunar dust in an electric arc; a white halo around the flame immediately betrayed the presence of titanium. Lunar basalt seems to be rich in this and other refractory elements—those with high melting points—and is at the same time relatively poor in the more volatile elements with low melting points, such as sodium and potassium.

As new samples come back from succeeding Apollo flights—eight more are scheduled after Apollo 12—scientists will have their hands full comparing the maria with one another, and the maria materials with those from the highlands.

Even the historic Apollo 11 samples will probably not all go on museum shelves for a long time. As Dr. Taylor says, “The moon rocks are different enough from earth rocks to keep us busy for years.”

Kenneth F. Weaver was Assistant Editor of the magazine at the time when this article was published.
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