The Mariner program was a program of spacecraft launched by NASA between 1963 and 1973. The spacecraft studied the planets Mars, Venus and Mercury. There were 10 spacecraft in the Mariner programme, named Mariners 1-10. Seven were successful but three were lost. The program included spacecraft doing things that spacecraft had never done before. These things included the first planetary fly-by, the first pictures from another planet, the first planetary orbiter, and the first gravity assist maneuver. Other spacecraft in the Mariner program were planned but they were changed into other spacecraft with different names. For example, Mariner 11 and Mariner 12 were planned but changed into Voyager 1 and Voyager 2.