The Scope of Cosmochemistry

The cosmochemist has two basic tasks. The first is to determine the chemical composition of matter in the material universe. The form of this matter ranges from such mundane materials as terrestrial rocks to distant galaxies. The second task is to understand the reasons for the compositions that are found. While the first of these tasks is basically a matter of analytical chemistry, the second has important evolutionary aspects.

From a logical and historical point of view, cosmochemistry is an extension of the well-established discipline of geochemistry. Victor Goldschmidt, one of the pioneers of modern geochemistry, had a keen interest in abundances of the chemical elements in meteorites and the sun and stars. Goldschmidt (1937) was an early compiler of what became known as the cosmic abundances, in which the analyses of extraterrestrial sources played important roles.

The logical complement to the term geochemistry, in the astronomical domain, would be astrochemistry. This word is frequently in the literature, but typically with a more restricted meaning, such as the formation of molecules in cool interstellar clouds. Solar system astronomers have used terms such as planetary geology or lunar geochemistry rather than astrogeology or astrochemistry.

For many years, astronomers thought of cosmochemistry primarily in terms of the nuclear history of matter, and the search for a standard abundance distribution (SAD). The modern aspects of this work began with Goldschmidt, and were continued by Hans Suess and H. C. Urey (1956).