This colourful view of Mercury was produced by assembling thousands of images of its surface taken by NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, which has been in orbit round the planet for two years (CERN Courier April 2012 p15). Before MESSENGER, more than half of the planet was a complete mystery. This image (and the one of the opposite side) completes the 100% coverage of the planet. The colours are not what Mercury would look like to the human eye but enhance the chemical, mineralogical and physical differences between the rocks that make up its surface. The giant Caloris basin is the large circular, tan-coloured feature to the upper right. Created by the impact of a comet or asteroid during the Solar System’s early years, it was subsequently flooded with lava from volcanic activity. Younger impact craters are surrounded by rays of ejected material appearing light blue or white.