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Tafoni are pits formed by non-uniform weathering in otherwise uniform rock. Two equations have been proposed for the rate of development of tafoni, both based on 2000-year-old outcrops from the coast of Japan. We have taken tafoni measurements from the Meteor Crater, Arizona, and vicinity that extend the equations back at least 50 000 years. As reported in earlier studies, we found pit depth to be the best tafone parameter to measure. The size of the pit decreases significantly with increasing inclination of the rock surface; however, the size of the pit can vary greatly for other reasons. In some cases the measurements are statistically significantly different between two stations taken from contiguous areas of similar inclination and aspect in an apparently homogeneous bed. It is clear, however, that over tens of thousands of years tafoni enlarge significantly. Our data are generally log-normal and all are markedly heteroscedastic. The 1991 equation proposed by Matsukura and Matsuoka does not fit our data. The 1996 equation proposed by Sunamura provides a better fit. We propose a sigmoidal equation D D b1 C e b2C b3/t where D is the depth, t is the age, and b1, b2 and b3 vary with lithology. This new equation fits our data far better than the earlier published equations.

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Dean Roden Chapman (1922-1995), an engineer and scientist at NASA Ames Research Center, was one of the founders of astronautics (rocket science). He used his laboratory to produce objects that are very similar to Australian tektites. There were two major questions about tektites in his day: did they come for the Earth or the Moon? And were they caused by meteor impacts or volcanic eruptions? Chapman came to believe that tektites were caused by meteor impacts on the Moon. He made many contributions to our understanding of tektites and was also one of the people who helped NASA get to the Moon. One percent of the Moon was covered with little glass spheres, but they are quite different from the tektites known on the Earth. The data from the Moon rocks was largely incompatible with the theory that terrestrial tektites are derived from the Moon. Chapman stopped publishing papers about tektites, but he remained interested in the subject for the rest of his life and believed that in the long run the lunar impact theory might become dominant again as new data was returned from the Moon. From our present understanding of tektites and the Moon, Chapman failed because he privileged the facts that he generated himself in his laboratory. He was not prepared to study the messy complexity of natural products. He was misled by the meteorite science traditions used in tektite science. He did not use appropriate statistical procedures, and because he was such a famous scientist in his own field the editors of two major journals in which he published did not properly assist him when he was working outside his area of major competence.