242 ANNUAL REPORT SMITHSONIAN INSTITUTION, 195 7 



layed rumbling, caused by its breaking up in the lower atmosphere, it 

 is called a detonating bolide. For these larger bodies the atmosphere 

 is less effective as a shield, so that sizable pieces of these celestial 

 cannonballs survive the atmospheric friction and fall to the ground. 

 These fragments we call meteorites, which we collect and preserve 

 in our museums as our only tangible samples of the great universe 

 that exists beyond the earth's atmosphere. Perhaps we are fortunate 

 that this sampling rate is so low ; otherwise more of us would suffer 

 the rare and undesirable experience of Mrs. Hodges in Alabama, 

 who, on November 30, 1955, was injured when a meteorite penetrated 

 her house and struck her on the hip. 



The collection of meteorites in the Smithsonian Institution is one 

 of the largest and most valuable in the world. These rare specimens 

 are continuously used by scientists in their attempts not only to 

 discover the origin and history of the meteorites themselves, but also 

 to understand the general laws of supervelocity ballistics involved 

 in the meteor's course through the earth's atmosphere. (See pi. 1.) 



For bodies even larger than the average meteorite, the earth's 

 atmosphere finally ceases to be an effective barrier. Thus irons or 

 stones weighing hundreds of tons or more are affected scarcely at all 

 in falling through the earth's atmosphere. They plow into the 

 ground at supersonic speeds and explode, to produce immense craters. 

 These explosions are literally like those made by huge bombs because 

 of the enormous kinetic energy of the meteorite. The extremely 

 rapid motion endows each pound of the meteorite with much more 

 energy than that contained in a pound of the most powerful chemical 

 explosive. This energy is instantly released when the earth's surface 

 stops the meteorite. A crater-forming meteorite of atomic-bomb 

 energy fell in the general region of Vladivostok in 1947 and produced 

 a great many craters over a large area of ground. In 1908 an even 

 larger fall, of greater than H-bomb energy, occurred near Pultusk 

 in Siberia. It leveled the trees radially from the point of impact 

 for some 50 miles. 



No huge craters have been formed by meteorites in historic times, 

 but the great Barringer meteor crater in Arizona, now some 600 feet 

 deep and nearly a mile across, represents the greatest of such celes- 

 tial visitations in the United States (see Nininger, 1952). The 

 largest meteorite crater in the world is probably the one in the New 

 Quebec (Ungava) area in Canada and is nearly 3 miles in diameter. 

 The crater is now an almost perfectly round bowl, partially filled 

 with water to form a beautiful lake, standing unique in a great 

 area of granite that was once covered by glaciers. 



The geological evidence proves that even more powerful celestial 

 bombing has been directed toward the earth in past geological periods 



