Studies of particles for extraterrestrial origin: 1. Chemical analyses of 118 particles

Dust particles of probable or known extraterrestrial origin were gathered, for the purpose of comparison, from a number of sources, including the stratosphere, 750-year-old Greenland ice, 55-year-old antarctic ice, the antarctic atmosphere, a New Mexico mountaintop, glacial ice caves, and the place of fall of the Siberian Sikhote-Alin meteorite shower. Out of the wide variety of types of particles in these samples, 118 representative particles were subjected to detailed chemical analysis by the electron-beam microanalyzer technique. The Fe/Ni ratios of 5 particles point undoubtedly to their meteoritic origin. From their high Fe/Si ratio some 35 others are thought to be extraterrestrial A few objects are identified from their compositions as being of obvious terrestrial origin. The cosmic influx of dust on the earth's surface is computed to be more than 105 tons per year.