America's first robotic planetary exploration missions were designed only to fly by the planet or orbit around it. They would serve as scouts for future more ambitious missions by more sophisticated spacecraft. Mariner 4 was the first to target Mars.
NASA began its methodical examination of Mars with the launch of Mariner 4 in November 1964. Although Mariner 4 was the first spacecraft to have Mars as its destination, it was the fourth of its kind to be used for planetary exploration in a flyby mode. Flying for seven and a half months and reaching Mars on July 14, 1965, Mariner 4 flew by at an altitude of 6,118 miles. Mariner 4 was able to send back 18 usable pictures, the first time for humans to see Mars unobstructed by Earth's atmosphere. While these pictures were astounding, they weren't sufficient to satisfy our curiosity.
Photo. The Mariner 4 spacecraft. Courtesy of NASA, JPL.
Mission to Mars. An educational site created for the ThinkQuest contest.