Mariner 9 was the first U.S. spacecraft to orbit Mars, entering orbit on November 13, 1971.
The mission arrived during a global Martian dust storm, so its cameras initially saw little of the surface. As the storm cleared, Mariner 9 photographed volcanoes, canyons, channels, and polar features in unprecedented detail. It also mapped much of the planet from orbit.
Earlier Mariner missions had performed flybys. Mariner 4 provided the first close-up images of Mars in 1965, while Mariner 6 and Mariner 7 returned additional flyby data. Mariner 9 changed the mission model by repeatedly observing the planet from orbit.
The spacecraft operated for nearly a year before NASA shut it down in October 1972. It was later joined in Mars orbit by the Soviet Mars 2 and Mars 3 spacecraft.