200 



SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS 



1932. — In the following year the Bedfords 

 returned to the Henbury craters planning to 

 search for large meteorites by digging in the 

 centers of the craters themselves. The}' exca- 

 vated four of the craters (nos. 10, 11, and 13 of 

 Dr. Alderman's list) and a nearby probable 

 crater not included in Alderman's study. In 

 crater no. 13 several pieces of nieteoritic iron, 

 totaling appro.ximately 80 kilograms, were 

 found at a depth of 2 meters below the floor. 



1937.— Five years later, .1. M. Rayner (1939) 

 and his associates carried out a magnetic survey 

 of the Henbury craters. Magnetic traverses 

 across 12 of the craters (all but no. 9 of Alder- 

 man's list) produced the definite result that no 

 large magnetic anomalies exist in the region 

 and therefore that no large meteoritic body can 

 be intact under the surface except at inipnib- 

 ably great depths. Within the cratei's 1(1 

 small local anomalies were discovered, the most 

 conspicuous being in craters nos. 5, 12, and 13. 

 The geophysical results strongly suggest that 

 these anomalies might be caused by small 

 masses of meteoritic iron buried at shallow 

 depths in the crater area. The cause of the 

 anomaly in crater 5 was found to be an 18- 

 kilogram meteorite. The causes of the anom- 

 alies in craters 12 and 13 apparently remain 

 there. Rayner found 16 other small anomalies, 

 half of them falling near the crater walls and the 

 other half falling at considerable distances from 

 the craters. These may indicate the existence 

 of pieces of meteoritic material buried at 

 shallow depths. 



1962.~The geologist C. H. Chao visited the 

 Henbiuy craters and looked for shatter cones 

 and other indications of impact. The results 

 have not yet been published. 



1963. — Meteoriticists E. P. Henderson and 

 Brian Mason carried out a search for meteorites 

 at the Henbmy craters; their results have not 

 yet been published. 



1963. — A very detailed geological map, as 

 well as a topographical study, of the main 

 craters (nos. 6,7, and 8) was constructed after a 

 prolonged studj' of the craters by D. J. Milton. 

 The results are not yet published. 



1963. — The author carried out a soil sm-vev 



of the ground surrounding the craters in an 

 attempt to establish the distribution of micro- 

 scopic meteoritic material around the craters 

 and to estimate the total mass of the original 

 meteorites. Results of this recent researcli 

 will be published later in these Contributions. 



The craters 



Table 1 lists all craters that have been either 

 definitely or tentatively identified and gives 

 data regarding tliem. In addition to the 13 

 craters described by Alderman there is a 

 f(uuteenth, excavated by Bedford and not 

 described in previous literature, and a fifteenth 

 iiliject, tentatively identified, as a result of my 

 inspection on the ground and from the air, 

 as a new small crater. I ha\c measured the 

 diametei's of all craters by means of aerial 

 photographs. The heights of the rims given 

 in the table are those estimated oil her by 

 Alderman (1932) or bv mvself. 



T.ABLE 1. 



-Diincn.'siuH.s of the 

 craters 



Ilenhunj meteorite 



» Doubtful. 



^ Location unknown. 



« Probable. 



