Addressing Unsolved Questions on Weathering of Surfaces in Space by Fast Solar Particles

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

This project seeks to advance the scientific understanding of the effect of bombardment of surfaces in space by fast charged particles (ions) from the Sun. Such effects include erosion as well as changes in both the chemical composition and the appearance. The studies will be done in the laboratory, in conditions similar to those existing in astronomical bodies without atmosphere. Examples of these bodies are the Moon and asteroids, which are the subject of planned human space missions. The results from the studies will advance science at the fundamental level but also will be applicable to new energy technologies; ion bombardment, for example, contaminates and limits the life of nuclear fusion reactors. The project results are also relevant to the studies of advanced materials; erosion by fast ions, for example, is of practical importance in the fabrication of high-temperature oxide superconductors and in thin dielectrics for use in microelectronics and photonics. The research will involve training of students and postdoctoral researchers in a unique set of experimental techniques. The study will be the most accurate to date in reproducing the effects of the wind ions on the surface of the Moon, asteroids and other airless bodies in the inner solar system. The laboratory studies will use ultrahigh vacuum, in situ chemical analysis, and mass-selected ion beams. We will examine samples of lunar soils, meteorites and simple minerals using multiple surface analysis techniques and optical spectroscopy. The basic phenomena to be studied quantitatively include sputtering (the ejection of atoms and molecules by energetic ions), changes in elemental and chemical composition, and changes in optical reflectance. The project will examine chemical reactions induced by implanted ions, including radiation-enhanced aqueous alteration, quantify the volatiles produced, and measure the magnitudes of sputter erosion and re-deposition. For the first time, the studies will use simultaneous irradiation with both protons and helium ions, to unveil synergistic effects; irradiation of samples coated with thin ice will simulate interfacial chemical reactions that may occur in asteroids; in situ examination of elemental and chemical composition, including surfaces of carbonaceous chondrites in meteoritic samples. The study on radiation-enhanced aqueous alteration is expected to aid interpretation of asteroid Ceres, a target of the current Dawn mission of NASA. The project will also involve graduate student training.