1976: On 3 September 1976, the unmanned US spacecraft Viking II landed on Mars and took its first pictures of the surface.
Its twin, Viking I, had been the first to arrive on the surface of Mars on 20 July 1976. Each lander housed instruments that examined the physical and magnetic properties of the soil, analysed the atmosphere and weather patterns of Mars with the aim of determining any evidence of past or present life.
Each Viking spacecraft was made of two parts: an orbiter and a lander. The orbiter's initial job was to survey the planet for a suitable landing site. Later, the orbiter studied the planet and its atmosphere, and acted as a radio relay station for transmitting lander data.