Earth

Earth (also known as Terra or Sol c) is the original homeworld of the humans. It is a terrestrial planet in the Solar System, and one of the few worlds in the Milky Way Galaxy where sentient life has evolved naturally. It was also the only body in the Solar System capable of harboring life for over 3 billion years until the terraformation of both its moon, Luna, and its sister planet, Mars in the 2100s A.D. Other terrestrial planets/moons in the system, such as Mercury, Venus, Ceres, Europa, Titan, & the Pluto-Charon pair, among others, could not feasibly be re-purposed, and as such, any colonies had to be heavily climate-controlled and isolated from the environment.