The goal of our Team is to explore key challenges in plasma-surface interactions at airless planetary bodies by exploiting the synergies between in-situ observations, computer simulations, and laboratory experiments to identify and understand the fundamental physical processes determining the global and local near-surface plasma environment.

Our solar system contains a wide range of airless planetary bodies, including the Moon, Mercury, asteroids, dormant comets, and the moons of Mars: Phobos, and Deimos. In-situ observations near the Moon, and remote-sensing measurements of many of these objects, led to the recognition that their surface properties and exosphere are strongly influenced by complex interactions between the dusty regolith, the solar wind plasma and UV radiation, with vastly different upstream and downstream plasma conditions as a consequence. The charging of small dust particles present in the near-surface environment may lead to their mobilization and transport, often making it difficult to analyze and interpret remote-sensing observations. For example, these processes have been suggested to be responsible for the lunar horizon glow and the formation of dust ponds on asteroids. The role of magnetic anomalies and their possible connection to lunar swirls (unusual albedo markings) remains especially enigmatic.

To address these issues, we propose to bring together a team of international experts and young scientists to merge observational, experimental and numerical modeling knowledge and expertise. Guided by existing space-based observations, our team will first identify key physical challenges that can be reproduced in a laboratory setting. We will exercise our numerical models to recreate these initial laboratory experimental results and build confidence that the codes correctly capture and predict the details of the plasma - surface interaction physics. As our numerical frameworks mature and successfully reproduce laboratory experiments with an increasing level of complexity, we will operate them to guide our analysis and interpretation of space-based observations. This is envisioned as an iterative process that converges on the identification of the most important physical processes that shape the surface properties of all airless bodies exposed to the solar wind environment. In contrast to earlier efforts, the maturity of the laboratory experiments will provide the vital link. In the lab one can simplify a real-life space scenario while being sure not to neglect essential physical processes, as they are inherently present.

The proposing group of scientists is expert in in-situ plasma measurements, surface spectroscopic measurements, and imaging. The existing laboratory experimental setups are readily available to generate flowing plasmas, UV radiation, surfaces with/without magnetic fields, and have full diagnostic capabilities. The group will also include experts on numerical studies of plasma kinetic processes using hybrid and full-particle methods. To conclude, the proposed project will greatly improve our understanding of fundamental surface-plasma interaction mechanisms with airless bodies. Although not driven by space exploration, our insights will be able to provide guidance for the development of better instrumentation for future robotic and human missions.

Our full proposal can be found here. The final team report can be found here.