Earth

From Wikitroid, the Metroid wiki

Earth is a planet mentioned in the Metroid series but never seen. It is where Humans originated from. It is sometimes speculated by fans to be the capital of the Galactic Federation. Earth is located in the Solar system. One of Earth's colonies is K-2L.

Planets in the Metroid Series
Note: Bolded Planets were visited by Samus Aran
FS-176 System
Bilium | Oormine II | Twin Tabula | Zebes | Tallon IV
Tetra Galaxy
Alinos | Arcterra
Federation Solar System
Bryyo | Norion | Elysia
SR 388 System
SR388 | UCB 1
Other
Aether | Bes III | Cylosis | Daiban | Earth | Jigrad
Jovia XII | K-2L | Mondreus | Naishii | Phaaze
Pirate Homeworld | Tivus | Vho | Wotan VII | UCB 3