probes on a single rocket was both risky and expensive. Voyager was the first major space science project to be cancelled by the U.S. Congress.

Despite the cancellation, the planning and development of the Voyager Mars program was eventually carried out by NASA's Viking program in the mid-1970s. Cheaper and simpler than the Voyager Mars program (using the same Mariner 8/9 design for the orbiter, but with an automobile-sized lander with a very expensive microbiology lab), the Viking 1