How Mariner 9 became the first spacecraft to orbit Mars in 1971

On November 13, 1971, NASA’s Mariner 9 spacecraft achieved a major milestone by entering orbit around Mars. Before this mission, space agencies had only conducted brief flybys of the Red Planet. These earlier missions captured images of craters, leading some researchers to believe Mars resembled Earth’s moon.

Discovering the Giants of Mars

When Mariner 9 arrived, a massive global dust storm obscured the surface. The probe spotted strange structures piercing the clouds. As the dust cleared, cameras revealed these shapes were the summits of enormous volcanoes. The discoveries included Olympus Mons, which stands as the tallest volcano in the entire solar system. The spacecraft also mapped Valles Marineris, a giant canyon system stretching thousands of kilometers across the planet’s surface.

Beating Rivals and Mapping the Planet

The NASA mission narrowly beat a competing spacecraft from the Soviet Union to Martian orbit. Equipped with cameras and spectrometers, Mariner 9 mapped eighty-five percent of the Martian surface and captured thousands of photos. It also photographed the two small moons of Mars, Phobos and Deimos.

The End of the Mission

The spacecraft operated in orbit for nearly a year. By early 1972, the probe depleted its supply of gas used for controlling its orientation. Space agency operators officially shut down the mission later that year, leaving behind a legacy of groundbreaking planetary discovery.

• Mariner 9 was the first spacecraft to orbit Mars.
• It discovered Olympus Mons and Valles Marineris.
• The mission mapped 85 percent of the Martian surface.