The Moon is the Earth's only natural satellite, and one of two bodies (alongside Mars) to undergo extensive terraforming.
Colonization of the Moon began in the late 1970s and was carried out primarily by the United States supported by its European partners.
The Moon is habitable to human life. Its atmospheric pressure at sea level is 83% of Earth's, and due to the low Lunar gravity, the height of the atmosphere is approximately seven times that of Earth's. Several seas - flooded mares - exist on the surface, around which civilization on the Moon is centered.
The Moon is generally very arid and experiences high temperatures; however, there is still climatic variation.