Laboratory Study of Dust Mobilization on Airless Planetary Bodies in the Solar Wind Plasma

Dust charging, and the subsequent mobilization and transport, have been suggested to explain a number of unresolved and unusual features observed on airless planetary surfaces. These processes are also critical for understanding and mitigating potential dust hazards to human and robotic exploration on the lunar surface. A patched charge model (PCM), developed from recent laboratory and theoretical studies, shows that secondary electrons and/or photoelectrons absorbed inside microcavities between dust particles on the surface of airless bodies can accumulate unexpectedly large negative charges, causing dust mobilization and lofting due to strong repulsive forces. Complementary to previous work with secondary electrons induced by an electron beam and/or photoelectrons induced by ultraviolet (UV) radiation, here we present dust mobilization due to ion-induced secondary electrons in a simulated solar wind plasma with the energies of nitrogen ions in the range of 100-1000 eV. It is shown that dust mobility is correlated with the secondary electron emission that is determined by the energy- and material-dependent emission yield, as well as the electrostatic potential profile developed above the surface. Our results provide a new charging mechanism by the solar wind plasma based on the PCM, which is expected to play an important role in dust mobilization in permanently shadowed regions, where the solar wind ions can be diverted onto areas that are not accessible to UV radiation.