MESSENGER The MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission is a scientific investigation of Mercury, the least explored of the terrestrial (rocky) planets. Understanding Mercury is crucial to developing a better understanding of how the planets in our Solar System formed and evolved. MESSENGER takes advantage of a clever mission design, lightweight materials, and miniaturization of electronics, all developed in the three decades since Mariner 10 flew past Mercury in 1974 and 1975. The compact orbiter, fortified against the searing conditions near the Sun, will investigate Mercury's characteristics and environment with a set of seven scientific instruments. It will provide the first images of the entire planet and collect detailed information on the composition of Mercury's crust, its geologic history, the nature of its thin atmosphere, and the makeup of its core and polar materials. Please Click here to learn more about the MESSENGER mission.