Word: lunar
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Dates: during 1970-1979
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...Pasadena, Calif. The pictures showed that Mercury's craters are much flatter and thinner-rimmed than the moon's and resemble giant pie pans-an indication that they may have been worn down by some yet-to-be-identified erosional process. Like most of their lunar counterparts, Mercury's craters were apparently created by impacts of asteroid-size chunks of material rather than by volcanic eruptions. Indeed, one crater, about 25 miles across, was blasted out of the rim of a 60-mile-wide crater by an impact that threw off raylike splashes of debris...
...Buzz Aldrin landed on the Sea of Tranquility, many questions about the moon remain unanswered. Indeed, some scientists feel that they may never completely learn the origin and history of the earth's immediate neighbor. Yet as a result of painstaking analysis of the 838 Ibs. of lunar rocks and the wealth of data collected by six Apollo crews, a fundamental understanding of the moon as well as of the early years of the earth is now finally beginning to emerge...
Scientists generally agree that the moon was created some 4.6 billion years ago, during the birth throes of the solar system. In fact, one of the most significant findings disclosed at last month's fifth annual lunar-science conference in Houston was a report by scientists from the California Institute of Technology that a rock collected by the Apollo 17 astronauts during the final moon voyage apparently traces back to that awesome event. It first cooled off and solidified some 4.6 billion years ago, making it older than any specimen previously found on the moon or earth...
Tiny Pebbles. At the time of the formation of the rock, the moon had just been created, possibly by the accretion of debris in orbit around the earth. As the debris-drawn by lunar gravity and ranging in size from tiny pebbles to huge boulders many miles across-crashed into the enlarging moon, it eventually generated enough heat to turn the lunar surface into a sea of molten lava. Slowly, as the bombardment lessened, the lava cooled and hardened into a crust that was then cratered by the impact of the remaining debris. When the rain of rocks eventually ended...
...young earth probably under went a similar period of bombardment and volcanic eruptions. But about 4 billion years ago, the histories of the earth and moon veered sharply apart. While the weak lunar gravity could not prevent the volcanic gases from escaping into space, the more massive earth held on to its volcanic vapors; it also was better able to retain its internal heat. The atmosphere and seas were formed, creating conditions for the first stirrings of life. Eventually, winds, water and mountain-building eradicated or covered virtually all geological traces of the planet's violent beginnings. In contrast...