The first spacecraft to orbit Mars had the bad luck to arrive at the planet during a massive 1971 dust storm that hid the entire surface. While it waited for the atmosphere to clear, the spacecraft turned its cameras on Phobos and Deimos and took the first close-up photographs of the Martian moons.
Mariner 9 would eventually return images of 80% of the planet's surface and show mission scientists a varied terrain that includes a volcano called Olympus Mons, which is three times as tall as Mount Everest, and geological features that may be ancient river channels.
Photo: Mariner 9 (NASA)
The first Mars orbiter gets a good look at the surface.
A series of missions finds astonishing features on the Red Planet.
The unmanned Mariner missions gradually revealed Mars's extreme landforms. Perhaps most impressive was Olympus Mons, a volcano three times the size of Mount Everest.
The probe sees Mars's moons, volcanoes.
Viewing parts of Mars missed by previous probes, Mariner 9 revealed three huge volcanoes and a massive canyon, now estimated to be 5 miles (8km) deep and over 1,800 miles (3,000km) long. The probe also took photographs of Mars's moons, Phobos and Deimos.
Mariner 9 (Mariner Mars '71 / Mariner-I) is a NASA space orbiter that helped in the exploration of Mars and was part of the Mariner program. Mariner 9 was launched toward Mars on May 30, 1971 from Cape Canaveral Air Force Station and reached the planet on November 14 of the same year, becoming the first spacecraft to orbit another planet — only narrowly beating Soviet Mars 2 and Mars 3, which both arrived within a month. After months of dust-storms it managed to send back clear pictures of the surface.
Mariner 9 returned 7329 images over the course of its mission, which concluded in October 1972.