Mariner 4 first photographed the far side of Mars during a close flyby.
NASA’s Mariner 4 passed Mars on July 14, 1965, becoming the first spacecraft to fly past the planet successfully and return close-up photographs. It transmitted 21 images covering a small portion of the surface, including terrain that had never been seen from Earth.
The pictures showed a heavily cratered landscape and challenged popular expectations of canals, vegetation, or an Earth-like surface. Mariner 4 also measured the Martian atmosphere and magnetic environment during the encounter.
Mariner 4 was a flyby spacecraft, not an orbiter. Mariner 9 later became the first spacecraft to orbit Mars and map the planet globally. Later missions revealed that the cratered regions photographed by Mariner 4 were not representative of every Martian landscape.