SECRETARY'S REPORT 165 



The tentative conclusions are that the feature is probably not an 

 impact site but an uncommon type of sand-dune formation. 



Tektites, their distribution, and possible associated impactites and 

 earth craters pose interesting questions. Are tektites terrestrial or 

 extraterrestrial in origin ? If they are terrestrial, are there associated 

 impact craters? Dr. Whipple has suggested that a large crater, on 

 the order of 15 miles in diameter, may exist in the Far East area of 

 tektite-strewn fields. Therefore Don W. Famsworth has begun a 

 map search for such an impact structure. He has so far examined 

 nearly 1,000 topographic maps of Sumatra, Java, Borneo, and nearby 

 islands. Maps showing depth to ocean bottom have been examined 

 and contoured. Search for an impact crater continues as maps be- 

 come available. 



Very small particles striking the high atmosphere are stopped by 

 atmospheric drag before they are destroyed. Larger bodies may 

 fragment or ablate on striking the atmosphere, generating many 

 smaller particles. Hence a rain of small particles from outside the 

 earth is constantly falling through the atmosphere to the surface. 

 The identification and analysis of these particles is a challenging 

 problem. 



The use of radio isotope techniques offers one means to identify 

 material as extraterrestrial. For this purpose Dr. Edward L. Fire- 

 man, working with Chester C. Langway of the Army Cold Regions 

 Research Laboratories, has collected and analyzed dust from melted 

 snow deep within the Greenland ice sheet. Results from this study 

 indicate that the exposure age of silicates in dust is less than 10,000 

 years.® 



Mrs. Ursula B. Marvin has made comparative studies of the miner- 

 alogy, chemical composition, and physical properties of black spher- 

 ules from the Greenland ice cap and industrial black spherules 

 produced by welding operations.^" Results showed that weld spatter 

 sometimes duplicates a type of black spherule, consisting of iron oxide 

 (magnetite) with less than 1 percent of manganese, that is found in 

 the Greenland ice and has been reported from many other environ- 

 ments where researchers have sought extraterrestrial dust. The most 

 common weld spatter, however, is metallic iron or nickel-iron that can 

 be distinguished from cosmic dust by a high content of chromium. 

 This work was done in collaboration with Mr. Langway. 



Collections of small particles have also been made on Observatory 

 collectors flown on a U-2 at high altitudes by the U.S. Air Force, 

 and on a B-52 by the NASA Flight Research Center, both at Edwards 

 Air Force Base, California. These collections have been analyzed by 

 Dr. Frances Wright and Dr. Hodge. They have also examined 



See footnotes, p. 177. 



