Radar image of Mercury. This image dates from 1991 and was made with the Goldstone Solar System Radar (GSSR) system. Red areas are areas of high radar reflectivity, which can either be a result of difference in surface and near-surface composition, or it can be die to surface roughness. The north pole is the brightest region, an indication of the presence of significant amounts of water ice. A similar region has been detected at the south polar regions. The two other large reflective regions remain a mystery. The radar pulses were transmitted from Earth using the Goldstone Deep Space Communications Complex (GDSCC), with reflected data received by the Very Large Array (VLA).