Tallon IV Incident
"Planet Tallon IV, formerly a Chozo colony, was struck by a stellar object 50 years ago. Object was later determined to contain large quantities of Phazon. The Chozo were able to stave off the spread of Phazon, at the cost of many Chozo lives. The survivors abandoned the planet, fleeing to an unknown location. Decades later, Hunter Samus Aran responded to a distress call in the sector and discovered a Space Pirate Phazon mining station there. Aran eliminated both the pirate and Phazon threat from the planet, though not without cost."