The Mariner Program was a series of space missions launched by NASA in the 1960s to explore the planet Mars and the Venus. These missions aimed to gather important data about the atmospheres, surfaces, and potential for life on these neighboring planets. The program included several spacecraft, with Mariner 4 being the first to successfully fly by Mars in 1965, sending back the first images of its surface. The success of the Mariner Program laid the groundwork for future planetary exploration. It provided valuable insights that helped scientists understand the characteristics of Mars and Venus, influencing later missions like the Viking landers and the Mars Rover missions.