158 Al«mUAL REPORT SMITHSONIAN INSTITUTION, 1963 



in decaying provided the planet with a pulse of high temperature 

 followed by rapid cooling. Dr. Wood .spent most of the past fiscal year 

 at the Enrico Fermi Institute for Nuclear Studies, University of 

 Chicago, working with Dr. Edward Anders on meteorite research. 



Dr. F. Behn Riggs, Jr., completed his investigation " of the use of 

 an electron probe specially designed to use with very large meteorite 

 sections without enclosing the specimen in a vacuum chamber. Sev- 

 eral meteorites were studied with this instrument. 



To facilitate interpretation of metallurgical features of meteorites ^^ 

 Dr. Matthias F. Comerford (in cooperation with Prof. H. H. Uhlig 

 of M.I.T.) and Joseph I. Goldstein (in cooperation with Prof. R. E. 

 Ogilvie of M.I.T.) are pursuing separate investigations of diffusion 

 processes at the interface of two different si^ecimens of nickel-iron 

 alloy. The dependence of the interdiffusion coefficients upon both 

 temperature and pressure is being measured. Pressures up to 50,000 

 atmospheres are being used in these experiments. 



Dr. Wright and Dr. Paul W. Hodge are pursuing a project to 

 determine the amount and nature of extraterrestrial particles col- 

 lected by the earth. This investigation has been furthered through 

 collection, by diverse methods, of particles from a wide variety of 

 geographical locations. The collected particles were microscopically 

 examined and their chemical and physical properties determined. A 

 total of 761 particles of possible extraterrestrial origin have been 

 chemically analyzed with electron-probe teclmiques. The results are 

 proving useful in establishing the chemical criteria for cosmic origin. 



Cometary science. — Comets have frequently been investigated by 

 Smithsonian Observatory scientists. A basic understanding of their 

 composition, structure, and resultant phenomena promises to clarify 

 important aspects of the origin of the solar system. The relationship 

 of comets to meteor showers and the response of comets to solar 

 activity are likewise important topics. 



Currently, Dr. Whipple is directing liis attention to the problem 

 of the cometary nucleus as evidenced in the brightness and deteriora- 

 tion of the periodic comets. Starting from a combination of meteor 

 and cometary studies he is performing calculations to ascertain more 

 exactly the lifetime of a major comet such as Encke's, which has 

 contributed a great complex of Taurid meteors. He is seeking to 

 identify Comet Encke in ancient records in order to determine changes 

 in period and brightness levels in the ancient past — perhaps 2,500 

 years ago. This research employs studies of photographic meteor 

 orbits, theoretical calculations, and cooperation with historians. 



Published photographs of Comet Arend-Eoland, examined by Dr. 

 Richard B. South worth, combined with computed particle trajectories, 



See footnotes on p. 164. 



