Exploration of the Moon invention of the telescope, an increasing number of people began to recognise the Moon as a sphere, though many believed that it was "perfectly smooth". In 1609, Galileo Galilei drew one of the first telescopic drawings of the Moon in his book and noted that it was not smooth but had mountains and craters. Later in the 17th century, Giovanni Battista Riccioli and Francesco Maria Grimaldi drew a map of the Moon and gave many craters the names they still have today. On maps, the dark parts of the Moon's surface were called "maria" (singular "mare") or seas, and the
Craters of the Moon National Monument and Preserve aside a large part of it——as Craters of the Moon National Wilderness, protecting that part under the National Wilderness Preservation System. From 1969 to 1972, NASA visited the real Moon through the Apollo program and found that its surface does not closely resemble this part of Idaho. NASA astronauts discovered that real Moon craters were almost all created by meteorites while their namesakes on Earth were created by volcanic eruptions. Apollo astronauts performed part of their training at Craters of the Moon Lava Field by learning to look for and collect good rock specimens in an unfamiliar and harsh environment.