Mariner 10
March 16, 1975

 

View of Mercury's surface

View of Mercury's surface

 

Mariner 10 flies by Mercury a third and final time. Passing 327 kilometers (203 miles) above the planet, its mapping mission is complete. By mapping about half the planet, the mission shows a cratered surface and a faint, mostly helium atmosphere.

As of 2002, Mariner 10 is the only spacecraft to conduct flybys of Mercury.