Experimental Study of Erosion of Methane Ice by Energetic Ions and Some Considerations for Astrophysics
Abstract
The rate of erosion and polymerization of methane ice under bombardment by hydrogen and helium ions, relevant to surface processes on Pluto and possibly Charon and Triton, is studied experimentally as a function of ion energy and ice film thickness. For the thinnest films studied, erosion of the entire film is accomplished using MeV energy helium ions. Loss of both carbon and hydrogen is observed from thicker films, with the hydrogen-to-carbon content of the films decreasing with increasing irradiation exposures. The effective 'cross section' for initial hydrogen loss is about 5 x 10 to the -16th sq cm. After a total incident dose of MeV He ions greater than about 10 to the 15th/sq cm, the loss rates decrease significantly and the effective cross section is about 10 to the -17th sq cm. Thus, the state of ultimate polymerization of a pure methane film in an astrophysical particle environment will depend critically on the thickness of the ice layer as well as on the ion composition of the radiation environment.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1987
- DOI:
- 10.1086/165031
- Bibcode:
- 1987ApJ...313..910L
- Keywords:
-
- Erosion;
- Ion Irradiation;
- Methane;
- Satellite Surfaces;
- Solidified Gases;
- Abundance;
- Energetic Particles;
- Helium Ions;
- Planetary Surfaces;
- Thin Films;
- Lunar and Planetary Exploration;
- LABORATORY SPECTRA;
- PLANETS: ABUNDANCES;
- PLANETS: GENERAL