Irradiation of Condensed Gases by Fast Ions: Physical Mechanisms and Astrophysical Implications

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There are numerous examples of astrophysical phenomena where knowledge of the effect of bombardment of ices by charged particles is crucial. Cosmic ray particles in the Galaxy modify gases and organics which are condensed on the mantles of interstellar ice grains. Ions in the solar wind and from solar flares, which bombarded ice grains and icy materials in the early stages of the evolution of the Solar System, altered the chemical nature of those materials which then accreted to form objects such as comets. Bombardment by plasma ions in the magnetospheres of the outer planets can alter the spectral characteristics of the surfaces of the satellites and rings of these planets. With this grant, Drs. Johnson and Boring, at the University of Virginia, in collaboration with colleagues at AT&T Bell Laboratories will continue their laboratory study of the changes produced in the spectral and chemical properties of icy surfaces when bombarded by energetic, charged particles. The experimental results will be used to understand the spectral alteration of icy grains and the production of large molecules in the interstellar medium, the modification of the surfaces of the satellites and rings of the outer planets, and the effect of long term ion bombardment on cometary debris and pre-cometary materials.