Measurements of Same-Material Tribocharging in Granular Silica

The dusty regoliths that form the surface of many low-gravity airless bodies are frequently composed of dielectric granular materials that are subject to charge buildup and triboelectric exchange. Triboelectric charging, especially between particles of the same material, remains poorly understood, especially in the unique vacuum environment on the Moon and asteroids. In these environments, it influences natural processes like avalanching and dust lofting, and presents a serious hazard to spacecraft operations due to charge buildup on spacecraft and rover surfaces. Terrestrially, the ambient atmosphere and relative humidity of the environment in which charging occurs is known to dramatically influence charging behavior. We have developed an experiment to measure tribocharging of grains in a mixture containing arbitrary grain sizes, using high-speed videography and contained entirely within our vacuum chamber. We observe trends in the charging behavior that deviate dramatically from terrestrial experiments featuring grains charged in atmosphere. We present here the results of these experiments and their implications on our understanding of same-material tribocharging in both terrestrial and extraterrestrial applications. Improving our modeling of extraterrestrial regolith tribocharging in this way may allow for better dust and charge mitigation techniques and even the beneficiation and utilization of regolith as a natural resource via electrostatic extraction by size and material.