In Metroid lore, Star Colony K-2L was a colony that mined afloraltite crystals, which created the energy used to power caravans between planets; it was used in the ignition module of all spacefaring vessels. Samus Aran’s parents lived on the colony, though it is unknown if she was born there. Samus’ father, Rod Aran, was the chief at the colony, and directed the operations.
According to Metroid Prime’s guidebook, K-2L neighbors FS-176 (more commonly known as Zebes, the Chozo home-world). This is disputed, though, because Yoshio Sakamoto (the guy that has overseen the development of every Metroid game, essentially the guy who dictates what is and isn’t canon) has said that the Metroid Prime series isn’t canon, so much as it is just an independent story. That being said, fans typically include the Prime series in any timelines because they supposedly add to the continuity and lore. (Metroid has good enough continuity as it is though, so take from that what you want.)
One fateful day, the Chozo showed up at the colony and asked for all the afloraltite. They didn't say why they needed it, or for how long; they simply said that it was very important and time-critical, and that they'd eventually return it. The Chozo were generally recognizeed to be a charitable and altruistic race; however, the colony politely refused. Just as the Chozo were leaving, the Space Pirates attacked, to steal all the Afloraltite. They killed everyone. Rod Aran managed to stowaway on the transport that was carrying all the afloraltite, and discharged a weapon into the crystals, which caused the shuttle to explode (killing him and all the space-pirates aboard in the process, as well as destroying the afloraltite.)
The Chozo took Samus as they escaped, and she was raised the rest of her life on Zebes, the Chozo homeworld. She was 3 years old. This all occurred presumably shortly after Galactic Year 2000, though who the hell knows what constitutes a galactic year.