The two-part Viking 1 spacecraft reached Mars orbit 50 years ago. A few days later, the images it returned of the proposed Viking 1 landing site were met with both elation and shock.

Mars as viewed by Viking 1's cameras did not look like the planet Mariner 9 saw. The Viking 1 Lander's proposed landing site, chosen after years of debate, lay on the floor of what looked like a deeply incised river bed. America's first Mars landing—scheduled for July 4, 1976, America's Bicentennial—would have to be delayed so a less risky landing spot could be found.

📷 This mosaic of Mars is a compilation of images captured by the Viking Orbiter 1. The center of the scene shows the entire Valles Marineris canyon system.