Topography of Mercury, MESSENGER image. During its four-year mission, the MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) spacecraft mapped the topography of Mercury's northern hemisphere. This relief map shows the lowest regions in purple, and the highest regions in red, with a maximum difference in elevation of around 10 kilometres. Among the prominent features visible here are the smooth northern volcanic plains. The low-lying craters near the north pole contain radar-bright materials, thought to be water ice. Image published in 2015.