164 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1964 



systems have been established at sites along the coast of North 

 Carolina. These receivers, together with a transmitter and receiver 

 on an ocean-going vessel, can make measurements of the ionization 

 of artificial meteors simultaneously with the optical observations. Dr. 

 Richard E. McCrosky is responsible for analysis of the optical data, 

 and Drs. Hawkins and Southworth, for the radar data. 



The entire 16-station Prairie Meteorite Network ^ has been in full 

 operation since early May 1964. Dr. McCrosky is principal investi- 

 gator. During the first months of operation the network obtained 

 double-station photographs of two extremely bright objects. With 

 magnitudes of the order of —12 and —15, both these meteors far 

 exceed in luminosity any object on which data have previously been 

 acquired. Their analysis is expected to yield interesting results. In 

 each case, unfortunately, the terminal mass was judged to be too 

 small to justify a search for the meteorite. 



Dr. Cook has continued work ^ with Dr. Peter M. Millman of the 

 National Research Council, Ottawa, and Dr. Ian Halliday of the 

 Dominion Observatory, Ottawa, on three Perseid meteor spectra ob- 

 tained at the Springhill Meteor Observatory at Springhill, Ontario, 

 in 1957. Dr. Cook has also worked on the physics of meteors to 

 generate a criterion for the mode of ablation, i.e., to determine whether 

 vaporization does or does not occur and then to seek observational 

 evidence for the action of this criterion. 



During its long life the earth's surface has been hit many times by 

 large meteorites, which have produced craters. Only a limited num- 

 ber of these have been recognized and studied. It is clear that appro- 

 priate effort can extend this number significantly, and the Observatory 

 has been involved in occasional studies of craters or possible craters. 

 Dr. Paul W. Hodge visited the Henbury Meteorite Craters and the 

 Boxhole Crater in Australia to study the meteoritic debris in the 

 soil surrounding them. 



A field party ^ made up of Ursula B. Marvin, T. C. Marvin, and 

 Walter A. Munn spent 16 days in August 1963 mapping and collecting 

 samples at the site of an unusual craterlike formation in the San Luis 

 Valley, Colo., to test the possibility that it could have resulted from 

 the impact of a small meteorite or comet. The plane-table map shows 

 that the "crater" is not a bowl-shaped depression in the landscape, 

 but that the rim is a positive feature surrounding a floor that is 

 concordant with the slope of the alluvial fan on which it lies. The 

 search through the samples for meteorite strippings, nickel-iron 

 spherules, or such impact products as glass or shock-produced silica 

 minerals has not been completed, but results to date are negative. 



See footnotes, p. 177. 



