Goals: Like its predecessor Mariner 3, Mariner 4 was designed to snap a series of photos of Mars after an eight month journey studying interplanetary space. The spacecraft was also equipped to study the Martian atmosphere as it flew past.
Accomplishments: Mariner 4 was one of the great successes of the early American space program. The spacecraft sent back 21 black and white images of the Martian surface -- the first pictures taken of another planet from space. The spacecraft found that Mars was a battered, cold and barren world. Scientists learned they would need retro rockets in addition to parachutes to safely deliver a spacecraft through the planet's thin atmosphere to the surface. Mariner 4 also found Mars' weak radiation belt.