Launched on May 30, 1971 and reached Mars on November 14, 1971. It was the first spacecraft from earth to go into orbit around another planet. Mariner 9 took over 7000 pictures of the planet and studied what the atmosphere and surface was composed of as well as Mars gravity and typography. It also took close up pictures of Mars’ moons Phobos and Deimos.
Launched on November 28, 1964, Mariner 4 was the first spacecraft to fly by Mars (flyby on July 14, 1965). It also provided us with the first close up look at the planet. The mission confirmed that Mars has a thin atmosphere composed largely by carbon dioxide.
American astronomer William W. Campbell was the first to question the common belief that there was an Earth like atmosphere on Mars. By comparing the spectrum of Mars and the Earth’s moon he saw they were identical. Thus concluding that the atmosphere of Mars was much like that of our moon. Only in 1925 were Campbell’s results verified by the American astronomer Walter S. Adams.