Numerical investigation of the electrostatic dust transport around a lunar lander

Abstract

Since the Apollo era, lunar dust has been one of the major problems for lunar surface explorations, since these very abrasive and adhesive grains are harmful for both the instruments and the human beings. Normally, the lunar surface can get charged with an electric field of several V/m, which is not strong enough to launch the dust grains from the surface. However, the electric field may be enhanced when the solar wind and the sunlight are shadowed by an obstacle. Such a shadowing effect can be caused by either a natural topographic feature or a man-made object. Here we study the shadowing effect of a lunar lander with particle-in-cell simulations. It is found that the shadowed region is negatively charged, with a surface potential as low as −30 V and an electric field as large as 20 V/m. A local dust cloud is caused by the electrostatic dust transport around the lander, with a number density of about 104 m−3 at 1 m altitude and up to 105 m−3 near the surface. The surface potential is determined by the temperature of solar wind, but a higher temperature can bring a weaker electric field and a smaller dust cloud, due to the enhanced Debye length. The electrostatic dust transport favors a larger shadowed area, caused by either a larger solar zenith angle or a higher lander height. In addition, the dust transport favors a conductive lander surface, where the maximum dust density can reach 106 m−3. Our results are helpful for the future lunar explorations and have general implications in studying the dust environment of other airless bodies.