Temperatures at Mercury's north pole. Enhanced colour composite image of the north polar region of Mercury, coloured according to the maximum biannual surface temperature, which ranges from greater than 400 Kelvin (red) to 50 Kelvin (purple). Sunlit areas reach the highest temperatures, whilst some craters have areas that remain in permanent shadow, where temperatures can be extremely low. Some craters at the poles have surface temperatures of less than 100K (-173 degrees C) contain stable water ice deposits. Imaged by the Mercury Dual Imaging System (MDIS) on NASA's MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft.