MOON EXPLORATION

scientific study of the Moon conducted with unmanned and manned spacecraft. As the Moon is the closest celestial body to the Earth, it became the focus of early space exploration for both U.S. and Soviet scientists. On Sept. 12, 1959, the Soviet Union launched Luna 2, the first space probe to hit the Moon. A second unmanned probe, Luna 3, sent up on October 4 of the same year, photographed much of the Moon's far side from a distance of 4,300 miles (6,880 kilometres). From 1964 to 1968 the United States launched three series of lunar probes that collected a wealth of information and opened the way for the Apollo manned Moon landings. Three Ranger spacecraft, in 1964 and 1965, returned more than 17,000 pictures of the Moon before crash-landing into it. During the next two years five Lunar Orbiters circled the Moon and sent back nearly 2,000 high-resolution photographs of about 98 percent of the lunar surface. At about the same time, five Surveyor probes made soft landings on the Moon. They not only transmitted approximately 80,000 closeup photographs of the lunar terrain but also returned environmental data, including information about surface properties. Man's firsthand exploration of the Moon began on July 20, 1969, when the Apollo 11 landing craft carried astronauts Neil A. Armstrong and Edwin E. Aldrin to a desolate lunar plain known as the Sea of Tranquillity. U.S. astronauts made five other expeditions to the Moon from November 1969 to December 1972. In exploring various regions and landforms of the Moon, they took thousands of photographs, collected numerous samples of lunar rock and soil, and performed a wide array of scientific experiments, several of which were designed to reveal more about the Moon's internal structure. Although the Soviet Union never landed a manned spacecraft on the Moon, it placed robot vehicles (e.g., Lunikhod rover) on the lunar surface in 1970 and again in 1972. It also succeeded in recovering samples of lunar soil on other missions of that time. Whereas the United States turned its attention to interplanetary exploration with the completion of the Apollo Moon-landing program in 1972, the Soviet Union continued launching unmanned lunar probes until 1974.