Information that isotopic measurements provide about space and the cosmos

Chemistry Department, Brookhaven National Laboratory, Upton, L. I., New York, U.S.A., U.S.A..

Abstract

The study of the isotopic abundances of the rare gases helium, neon and argon in iron meteorites has lead to the conclusion that the rare gases are produced mainly by the action of the cosmic rays with the meteorites. The high energy cosmic ray particles produce nuclear spallation reactions with the elements composing the meteorites. By comparing the cosmic ray produced radioactive isotopes of different half-lives such as ³H, ³⁷A, ³⁹A, ³⁶C1, ²⁶Al, ¹⁰Be and ⁴⁰K it is possible to investigate the constancy of cosmic rays in time and space. The measurements indicate that during the last 500,000 years there has been no greater than a ten percent change in the intensity of cosmic rays, and that cosmic rays near the earth have about the same intensity as cosmic rays in the asteroidal belt some 450 million kilometers further from the sun. In addition there is evidence that indicates that some of the meteorites have undergone collisions in space previous to being captured by the earth.