In 1976, the unmanned spacecraft Viking II landed on Mars and took the first pictures of the surface of Mars. Its twin, Viking I was the first to arrive on the surface of Mars on 20 Jul 1976. Each lander housed instruments that examined the physical and magnetic properties of the soil; analyzed the atmosphere and weather patterns of Mars; and determined any evidence of past or present life. Each Viking spacecraft, as launched inside the nose cone of a Titan Centaur rocket, 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's instruments studied the planet and its atmosphere, while the orbiter acted as a radio relay station for transmitting lander data.