Mariner 4 was the first successful American flyby mission to Mars. The purpose of the probe was to conduct close-up scientific observations of the planet, and transmit them back to Earth. At the same time the instrumentation of the vehicle was designed to permit for the analisys of interplanetary space between the orbits of Mars and the Earth.
Although the scientific data collected by Mariner 4 contributed to the advancement of the exploration of Mars, one of the most important things accomplished by this mission was to dispel many of the myths surrounding the red planet. Close-up pictures from Mariner 4 dispelled the 19th century myth of a extinct advanced civilization on Mars. These pictures also revealed that the canals seen by Percival Lowell in 1890 were mere optical illusions. These pictures, although they represented only 1% of the Martian surface, showed scientists the barren and cratered landscape of Mars. Although the major purpose of this spacecraft, which was launched on November 28, 1964, was to photograph the red planet, this probe had another role after its original mission was over.
When the craft returned to the vicinity of the Earth in 1967, engineers used it to further develop the existing telemetry technology. Until the end of its operational life on December 20, 1967, Mariner 4 aided in the development of better telemetry systems for future spacecraft.