US space agency NASA has celebrated the 40th anniversary of the first spacecraft landing on Mars.
Viking 1 was launched into space in 1975 and spent 10 months to reach the red planet. It finally landed on Mars in July 1976.
The Viking project took more than 65,000 images of the planet and collected overwhelming amounts of data. The main aim of the mission was to examine evidence of life on Mars.
The operation revealed chemical activities in the Martian soil, and provided a detailed map of the red planet's surface.