 After the encounter "Mariner 10" was in an orbit around the Sun such that for every one of its orbits Mercury made two, and the spacecraft and the planet would be able to meet again.This allowed the probe to pass by Mercury two additional times before completing the mission; these encounters were made on September 21, 1974, and March 16, 1975.However, since the same side of Mercury was illuminated during each of the flybys, at the conclusion of the mission "Mariner 10" had only photographed 45% of its surface.