On the seventh anniversary of the Apollo 11 lunar landing, the Viking 1 lander, an unmanned U.S. planetary probe, becomes the first spacecraft to successfully land on the surface of Mars.

Viking 1 was launched on August 20, 1975, and arrived at Mars on June 19, 1976. The first month of its orbit was devoted to imaging the surface to find appropriate landing sites. On July 20, 1976, the Viking 1 lander separated from the orbiter, touched down on the Chryse Planitia region of Mars, and sent back the first close-up photographs of the rust-colored Martian surface.

In September 1976, Viking 2–launched only three weeks after Viking 1–entered into orbit around Mars, where it assisted Viking 1 in imaging the surface and also sent down a lander. During the dual Viking missions, the two orbiters imaged the entire surface of Mars at a resolution of 150 to 300 meters, and the two landers sent back more than 1,400 images of the planet’s surface.