Earth has many satellites orbiting it, but the only significant natural satellite that orbits the Earth is the moon. The Union of Concerned Scientists (UCS) maintains a listing of all man-made satellites orbiting the Earth, which includes more than 1,000 operating satellites.
More than 500 of these man-made satellites are operated by the United States, with more than 100 also coming from Russia and China. The UCS Satellite Database is a free and comprehensive database that allows people to find information about the various satellites including altitude and mission. Users are able to find answers to popular questions, such as the number of satellites a given country has in orbit and their specific usage.
The moon is Earth's only significant natural satellite, and it is believed to be approximately 4.5 billion years old. When seen from Earth, the moon's surface looks bright with darker patches. The lighter patches are rugged terrain and marked with circular meteorite impact craters called lunar highlands. These lunar highlands are made up of anorthosite and polymict breccia rock. The other darker regions areas of the moon are naturally smooth and contain lunar maria, which is a type of sea that does not contain water.