Firdousi crater. View of the Firdousi crater on the surface of the planet Mercury. Firdousi is a relatively fresh impact crater approximately 96 kilometres in diameter. Its abundant secondary craters dominate the surroundings, many of which have halos of high-reflectance, relatively blue ejecta material. Imaged by NASA's MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft, on 14th August 2011.