AAAS in Denver

Dr. Harvey Harlow Nininger has made Denver the meteorite capital of the U. S. Curator of meteorites at Colorado Museum of Natural History, professor of geology and meteoritics at University of Denver, he is the most persistent and energetic chaser of meteorites in the land, possessor of the world's largest private meteorite collection and probably the only scientist anywhere who spends all his working time hunting, studying, writing or talking about fragments of the cosmos from outer space. Last week some 800 members of the American Association for the Advancement of Science assembled in Denver for their summer meeting, and one of the sectional conferences was that of the Society for Research on Meteorites, of which Dr. Nininger is secretary. He had been waiting for this occasion and he was much in evidence--slim, dark, bespectacled, lecturing in a deep, pleasant voice, pointing a bamboo fishing pole at his lantern slides. He gave three talks, introduced two of the other speakers.

Most meteors or "shooting stars" are entirely consumed by the burning friction of their swift flight through the atmosphere. Meteorites are bodies which are big enough to survive their flaming passage and land on earth. Meteoriticist Nininger was born 50 years ago in Kansas, in which a greater number of important meteorite finds have been made than in any other U. S. State. He started his scientific career, however, as a biologist. One night in 1923, while he was a biology professor at McPherson College in Kansas, he saw a shooting star so bright that he was sure some of it must have reached earth. The idea so excited him that he chucked biology for star-chasing forthwith.

Meteorites fall in showers and Harvey Nininger by last week had got his hands on specimens from 77 different meteoritic falls. He pays what he considers a fair price to landowners on whose property meteorites are discovered, whether they are aware or not of the scientific value of the prize. His usual price is $1 per Ib., but he may pay much more than that for unusually fine specimens. He has supplied meteorites to the Smithsonian Institution, Harvard University, Chicago's Field Museum, Manhattan's American Museum, museums in Mexico, England, France, Czechoslovakia.

One of Dr. Nininger's troubles is that most people who see a brilliant fireball are so excited that their subsequent testimony Is likely to be highly inaccurate. He himself has learned to sight meteor paths with extraordinary precision. On one occasion he sighted a fireball, marked out its probable course by drawing a line on a map. This line passed through the very field in which the meteorite, a splendid 820-pounder, was located a month later.

Last week Dr. Nininger learnedly described operations on a meteoritic site in Kiowa County. Kansas, which he believes to be the world's first complete excavation of a meteorite crater. Some 300,000 separate fragments were recovered there, ranging from 85 Ib. down to tiny grains. Assistant Secretary of the Society for Research on Meteorites is Dr. Nininger's wife, Addie Delp Nininger.

Dr. William Donald Urry of Massachusetts Institute of Technology read a paper on the ages of iron meteorites. Ages are measured in the same way as those of terrestrial rocks; by the amount of decomposition of radioactive material. "A very young iron meteorite," said Dr. Urry, "is 100,000,000 years old. The oldest is 2,900,000,000 years old." The last figure is just within the upper limit commonly given by geologists for the age of the earth and the solar system. Dr. Urry believes that iron meteorites are the debris of planets which have broken up within the last 100,000,000 years.

Other highlights of the Denver meeting:

Dry Mars, Despite the spreading of the frosty polar caps of Mars in winter and the darkening of the "canals" in summer (possible evidence of vegetation), astronomers have long been convinced that there is very little water on the "red planet." The amount of water vapor in the Martian atmosphere appears to be less than 5% of that on earth. It is difficult to measure the planet's water by spectrographic means because of spectrum lines caused by vapor in the Earth's air. Last spring Astronomers Walter Sydney Adams and Theodore Dunham Jr. of Mt. Wilson Observatory had a good chance to finesse this difficulty. Mars was then approaching Earth at about 13 mi. per second. When a source of light is approaching the observer, the spectrum lines are shifted to the right of their normal position. Thus Martian vapor lines would have been separated from those of Earth. The astronomers armed the 100-in. telescope with a 9-ft. spectral grating, but no Martian vapor lines showed up. They concluded that the planet's atmosphere is very nearly bone-dry.

Mystery Particle. Newest and most mysterious particle in the collection of atomic physics is the little thing discovered in cloud-chambers last spring by Drs. Jabez Curry Street & Edward Carl Stevenson of Harvard and by Dr. Carl David Anderson of California Institute of Technology (TIME, May 10). It does not con-form--as did the positive electron-- to any mathematical predictions. Not much is known about it except that it is heavier than an electron, lighter than a proton, possessed of high penetrating power. In Denver last week Dr. Street announced that it may be positive as well as negative, that in his opinion it is not a messenger from outer space but originates about ten miles up in the stratosphere, as the result of an impact delivered by a cosmic ray particle. What it is that gives birth to the new particle when struck is a matter of conjecture.

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