Mihaly Horanyi
University of Colorado, Boulder
The Apollo missions showed that dust on the lunar surface severely affects the operation of instruments and poses a risk to the health and safety of the astronauts operating in or outside their habitats. A critical element driving the behavior of lunar dust is its interaction with UV radiation and the plasma environment leading to electrostatic charging, mobilization, and transport even without, or in combination with, the mechanical interactions due to the movement of rovers or the astronauts. Recent laboratory studies have indicated that the cohesion, charging, and mobilization of dust particles are largely driven by processes that are occurring at the scale of the dust particles. To address these issues, we propose the development of a framework of numerical models that couple the microphysics of grain-scaled (microns) processes with the self-consistent solution of the near-surface plasma environment (meters) to investigate dust charging behavior and dust transport phenomena. Our proposed plasma modeling framework covers seven orders of magnitude in length and time scales. On the smallest micrometer scales, we extend an in-house test-particle code specifically developed for the investigation of electric field structures and micro-cavity charging, adding also the functionality to simulate the behavior of a large set of dust particles with irregular shapes. On the system scales, we expand an electrostatic particle-in-cell code to include multiple and composite surfaces that are built using the electric field output from the test-particle model. Coupling both codes enables us to better understand the role that the micro-cavities forming between individual regolith particles have on their charging and mobilization. The proposed modeling framework will be tested and verified using the precise experimental parameters of the ongoing laboratory efforts of NASA SSERVI’s Institute for Modeling Plasmas, Atmospheres, and Cosmic Dust (IMPACT) at the University of Colorado Boulder. The proposed close collaboration builds confidence for extrapolating the modeling work to parameter ranges not attainable through experiments but expected to characterize the lunar surface and its evolution in a variety of operational scenarios.