On this day in 1971, the Mariner 9 spacecraft was launched from Cape Canaveral Air Force Station, Florida. It would become the first spacecraft from Earth to orbit Mars (or any other planet). It arrived at Mars on November 14, 1971. The Soviets were also working on their own program, launching their two Mars-bound spacecraft even earlier in May, but both arrived at Mars after Mariner 9.
The Mariner 9 spacecraft successfully mapped 85 percent of the Martian surface and also sent back thousands of images detailing the Martian surface as well as the two Martian moon, Deimos and Phobos. NASA’s last contact with the spacecraft was on October 27, 1972. The spacecraft was expected to remain in orbit until 2020, when it would crash onto the Martian surface.
You can read more about the Mariner 9 mission here.