Surface Charging of Jupiter's Moon Europa

Europa's surface is exposed to a constant flow of plasma from its ionosphere and Jupiter's magnetosphere. As these particles flow onto the surface, an electrostatic surface potential forms. We investigate the electrostatic charging of Europa's surface using 3D particle-in-cell simulations. We find that surface potentials on Europa vary from -14 to -52 V. The predicted surface potentials vary as a function of location on Europa, illumination conditions, plasma environment, and surface properties. We reveal that the ionosphere has a significant "dampening effect," limiting the formation of large negative surface potentials. Furthermore, we find that secondary emission is a key factor in determining the surface charge on Europa. We discuss how such potentials may be remotely detected by upcoming missions, such as Europa Clipper and JUICE. Our results may also be of use in the design of future missions to Europa's surface, such as landers and other robotic explorers.