It was the first spacecraft to orbit another planet and compile the first image of the Martian surface revealing tectonic plates, erosion and pitted craters fueling fascination of our red neighbor in the solar system.
NASA's Mariner 9 beat the Soviet Mars 2—which had an 11-day head start—to Mars, becoming the first spacecraft to orbit another planet. The orbiter mapped 85% of the Martian surface and sent back more than 7,000 pictures, including images of Olympus Mons, Valles Marineris, and Phobos and Deimos.