MARINER 10
Mariner 10 was the first space probe to visit Mercury. It was also the first probe to visit two planets—Venus and Mercury. Mariner 10 used the gravitational pull of Venus to swing it into a different orbit so it could continue on to Mercury. Between 1974 and 1975, Mariner's flight path took it past Mercury three times. The probe's primary mission was to obtain close-up views of Mercury.

Until Mariner 10, astronomers were not sure what Mercury really looked like because it is so close to the sun and is usually lost in solar glare. The probe passed within 203 kilometers of Mercury and took some 2,800 photographs. Most of Mercury's surface was revealed in full detail by Mariner's visit.

MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER)
The MESSENGER probe is a NASA spacecraft, launched August 3, 2004 to study the characteristics and environment of Mercury from orbit. It is only the second space probe to explore Mercury. MESSENGER is an orbital mission, and will spend over a year imaging the entire planet with drastically improved cameras from those used on the Mariner 10 flyby.