Two Viking spacecraft were launched from the Earth in 1975 for the purpose of landing on Mars. The discovery by Mariner of river and lake beds on the surface rekindled visions of life on Mars, and the Viking craft were equipped with experiments to probe for bacterial life. The Viking craft consisted of orbiter and lander modules. The lander descended to the surface with the aid of a heat shield, a parachute, and retrorockets.
The orbiters were able to establish through spectroscopy that the residual polar caps were indeed water ice. The landers did not find evidence of life, but collected enormous amounts of data about soil and air composition. That air composition data was valuable later for identifying meteorites found in Antarctica as having come from Mars.
The Viking orbiter captured images of the two moons of Mars in 1977.
Solar System Illustration
Solar System Concepts