Mariner 9

Mariner 9 (Mariner Mars '71 / Mariner-I) was a robotic space probe that contributed greatly to the exploration of Mars and was part of the NASA Mariner program. Mariner 9 became the first spacecraft to orbit another planet – only narrowly beating the Soviet probes Mars 2 (launched May 19) and Mars 3 (launched May 28), which both arrived at Mars only weeks later.