Effects of Crystal Orientation and Temperature on Space Irradiation of Silicates

Abstract Space irradiation plays a crucial role in surface weathering and hydration processes of airless bodies in the solar system. Despite extensive laboratory studies, the impact of crystal orientation and temperature on these irradiation processes remains poorly understood. In this study, we conducted hydrogen-implantation experiments on olivine crystals, controlling both crystal orientation and temperature. Our results reveal that the amount and depth of implanted hydrogen depend on the crystal orientation. Olivine exhibits the largest resistance to ion irradiation along the [100] direction, resulting in a thinner damaged region (∼180–200 nm) and subsurface vesicle formation. In contrast, the [010] and [001] orientations allow deeper damage (∼200–210 nm) accompanied by fracturing. Additionally, increasing temperatures from 25°C to 200°C promote the saturation and retention of implanted hydrogen. However, above a critical temperature (∼200°C for olivine), hydrogen levels stabilize, and no further increase is observed. These findings highlight the critical role of crystal orientation and temperature in the irradiation process, providing important constraints for numerical models simulating the effects of space irradiation on rocky bodies.