Mariner 8 (Mariner H)

Designed to be the first American spacecraft to study the Red Planet from a Martian orbit, Mariner 8 (also called Mariner H) fell victim to a malfunction in the stage's flight-control system shortly after launch.

However, Mariner 9, the second of the pair of spacecraft created under NASA's Mariner Mars 71 project, successfully took on Mariner 8's objective to map 70 percent of the Martian surface.