Word: potassium
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Dates: during 1960-1969
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...surprisingly, one of the few jubilant scientists in Houston last week was Geochemist Oliver Schaeffer, who led the team that calculated the age of the lunar material. He used potassium-argon dating, a method based on the rate at which radioactive potassium decays into argon (it takes 1.3 billion years for half the potassium to decay); as time passes, the ratio between the potassium and argon in a specimen changes at a known rate, thus revealing the approximate age of the sample. If there is any error at all, Schaeffer explains, he has underestimated the age of the rocks, because...
...addition to the argon that resulted from potassium decay, Schaeffer found an abundance of solar argon-and of helium and neon-that has collected during eons of bombardment by the sun. These particles were lodged only in the surface of the rocks, where they had remained undisturbed for hundreds of millions of years-more evidence that the moon's exterior has not undergone any recent upheavals...
Chemical analysis of the samples may also help determine whether lunar material was ever hot enough to have melted, or whether it has been relatively cool almost from the first. Moon specimens strikingly lacking in volatile elements such as potassium and arsenic could indicate that these substances had been expelled by high temperatures?and would support the theory of a volcanic moon. Those who believe that meteors gave the moon its cratered surface might still argue, however, that the volcanism had occurred only in areas struck?and heated?by huge meteors. Studies of the crystal size and average density...
...bigger than a pack of cigarettes, the arsonists' bombs are expertly fashioned from a minuscule penlight battery, a wristwatch, a flashlight bulb and incendiary chemicals (potassium chlorate and potassium permanganate) that can be bought at local drug stores. Often tucked under a pile of fabrics in a crowded store, the minibombs are timed to flare after closing hour. In one day, four fires did $810,000 worth of damage to stores owned by U.S. merchants; unexploded devices have been found in the bathroom of a girls' school and, two weeks ago, at a U.S. Selective Service office...
...year-old potsherd to a 19th century vase. The technique employs the radiation-measuring devices used at most atomic reactors and in hospital radiotherapy departments. It is based on the fact that most mineral substances buried in the earth absorb the natural radiation given off by uranium, potassium and thorium in the earth. The rate of radiation has been relatively constant in historical times, but all absorbed radiation is released when the substance is heated...