Science: Changing the Lunar Image

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Technicians were swarming around Launch Complex 39A at Cape Kennedy last week getting ready for the month-end lift-off of Apollo 14. But all the attention at Houston's Manned Spacecraft Center was still focused on the scientific byproducts of man's last successful moon landing. After painstakingly analyzing the 75.6 Ibs. of rock and debris hauled back from the edge of the Ocean of Storms by the Apollo 12 astronauts more than a year ago, 714 scientists gathered for NASA's second major moon-rock conference. The moon, they agreed, is not a cold, unchanging conglomerate of material, as originally suspected by some theorists. It is apparently still warm inside, has been geologically active and may even be undergoing small surface changes.

Crustal "Kreep." Perhaps the most direct evidence for this modern image of the ancient moon was the discovery of tiny, glassy bits of material in the Apollo 12 soil. Until a few weeks ago, lunar scientists had identified only fragments of lunar surface material, scraps of the moon's churned-up "topsoil." But Paul Gast, chief lunar scientist of the Manned Spacecraft Center, and other investigators seemed convinced that in the Apollo 12 samples they have now found chips from the moon's original underlying crust, which were apparently tossed up by the impact of a large meteorite.

Gast dubbed the suspected crust material "kreep," an acronym based on its unusually rich concentration of potassium (chemical symbol: K), rare-earth elements and phosphorus (P). The high concentration of these elements, in addition to large percentages of uranium, helped convince scientists that kreep originated during a melting process that would have produced a lunar crust. Kreep also has remarkable chemical and physical similarities to a 3-oz. lemon-size Apollo rock that Caltech's Gerald J. Wasserburg had previously calculated to be 4.4 billion years old, or about a billion years older than most of the other Apollo 11 and 12 rocks.

If there is indeed a lunar crust, the moon, like the earth, must have gone through a process of geological evolution known as differentiation. This would mean that the moon was once hot and fluid enough to have separated into layers of different density and chemical composition, the heavier metals sinking toward the lunar center, the lighter ones forming the crust.

Another indication that the moon is differentiated came from data radioed back to earth by the magnetometer left behind by the Apollo 12 astronauts. The magnetometer measures changes in the magnetic field induced in the moon by the solar wind, the charged particles that stream outward from the sun. Because the magnetometer's readings also offer clues to the moon's internal electrical conductivity and temperature, they enabled Dr. Charles Sonett of NASA's Ames Research Center to make an educated guess about the structure of the lunar interior.