Moon

Moon is the only natural satellite of Earth [Note 4] and the fifth largest satellite in the solar system. It is the largest natural satellite of a planet in the solar system in relation to the size of your principal, a quarter of Earth's diameter and 1 / 81 and its mass (Charon is proportionally large compared to Pluto, Pluto, but has been reclassified as a dwarf planet.) The Moon is the second densest satellite after Io. Is in synchronous rotation with the Earth, always showing the same face, the near side is marked with dark volcanic maria between the ancient highlands of brilliant bark and prominent impact craters. It is the brightest object in the sky after the Sun, although its surface is really very dark, with a reflection similar to that of coal. Its importance in the sky and its regular cycle of phases since ancient times have made the moon a great cultural influence on language, calendars, art and mythology. gravitational influence of the moon causes the ocean tides and longer minute of the day. current orbital distance of the Moon, about thirty times the diameter of Earth, it displayed nearly the same size in the sky as the sun, allowing it to cover the sun almost exactly in the total solar eclipses. 

The Moon is the only celestial body on which humans have landed. Although the program of the Soviet Union Luna was the first to reach the Moon with unmanned spacecraft in 1959, the U.S. NASA Apollo program achieved the only manned missions to date, starting with the first manned mission to the moon in orbit by Apollo 8 in 1968, and six manned moon landings between 1969 and 1972-the first was the Apollo 11. These missions returned more than 380 kg of lunar rocks, which have been used to develop a detailed understanding of the geological origins of the Moon (believed to have formed about 4. 5000 million years ago, in an event of great impact participation of the Earth), the formation of internal structure and its subsequent history.