The Coon Butte Crater controversy

Abstract G. K. Gilbert's (1891) first assessment of the crater at Coon Butte, Arizona (now called Meteor Crater), was that it was caused by a meteorite impact. His classical paper The Moon's Face (1893) eloquently argued for the impact hypothesis to explain lunar craters. But by 1896 he had changed his mind on the Coon Butte Crater, as he could not find the “buried star,” even though several tons of meteoritic material had been found in the area. The steam explosion explanation, suggested to him by Willard D. Johnson and tentatively adopted by Gilbert, then became the accepted hypothesis for the origin of Coon Butte Crater among most geologists. In spite of a great deal of evidence for the impact idea, the steam explosion explanation, with the exception of a few notable individuals, took root in the geological community, much to the frustration of D. M. Barringer. The latter insisted on the existence of the “main mass” of the meteorite and spent a lifetime and fortune attempting to prove the impact origin of the crater by looking for the meteoritic body. He also had visions of a lucrative mining adventure. Barringer opposed G. P. Merrill, a distinguished scientist within the geological community, who supported the impact idea but explained the absence of a “main mass” of meteoritic material by its volatilization. The modem explanation for the creation of the crater is by shock waves produced from the dissipation of kinetic energy of the meteorite travelling at hypervelocity. Several reasons might explain the long delay in acceptance of the impact hypothesis: (1) in the absence of more evidence, the geological community naturally followed the lead of the much-admired Gilbert; (2) to the geologists, Barringer and his associates were outsiders, rich and respected men in other fields and in industry, but not in geology and therefore could be ignored; (3) Barringer was “ahead of his time,” and therefore could not expect much support from his contemporaries. The reasons were probably multiple and complex and may involve fundamental philosophical concepts. For example, as Eugene Shoemaker (1984) suggested, geologists were so imbued with Lyellian uniformitarianism that they could not accept a catastrophic explanation, i.e., the fall of an extra-terrestrial object causing the creation of a terrestrial feature. It is not clear, however, that any one answer explains the puzzle. The Coon Butte Crater controversy also tests two other ideas much touted by geologists, the principle of multiple working hypotheses and the idea of tolerance for unorthodoxy in science. Both concepts seemed to have failed the test.