Simulation of Space Weathering on Asteroid Spectra through Hydrogen Ion Irradiation of Meteorites

Space weathering can be defined as the combination of physical and chemical changes that occur in material exposed to an interplanetary environment on the surface of airless bodies. This process results in alterations in material spectroscopic features. Eventually, it can lead to misinterpretation of remotely sensed data in the visible-near-infrared wavelength range. This study simulates the solar wind effect on asteroid spectra through low-energy 1 keV H+ irradiation of meteorite pressed-powder samples under three fluences, 2 x 10(17), 5 x 10(17), and 1 x 10(18) H+ cm(-2), and evaluates changes associated with reflectance spectra. The meteorites subjected to the study are Bjurbole (L/LL4), Avanhandava (H4), and Luotolax (howardite). The most prominent changes in all three meteorites are (1) a decrease of 550 nm reflectance, (2) reddening in the 1 mu m region, and (3) a monotonous decrease in absorption band strengths in Bjurbole. No significant changes were observed in the 2 mu m region. The results imply that at short timescales (10(2)-10(3) yr), radiation damage as amorphization and vesicle formation caused by low-energy solar wind is the dominant space weathering factor in all three meteorite compositions, causing spectral changes predominantly in the 1 mu m region.