KG-348 is a Jovian Gas Giant, its outer layers largely comprising of molecular hydrogen, in the Zeta Reticuli region. After initial scientific surveys of its cloud layers, a rare mix of metallic gases were discovered, amidst the expected Helium-3, leading to further investigation and the heightened possibility of expanding Sevastopol Station, a station in orbit of the planet, into a fully-fledged atmosphere mining facility.
In 2137, Sevastopol's Gemini Exoplanet Solutions module was jettisoned from the station into the planet in an attempt to kill the Alien that was killing those aboard the station, who was sealed inside the module by Amanda Ripley. The plan worked, and the module presumably burned up in the gas giant's atmosphere, killing the Xenomorph.
Later, the Anesidora exploded next to the station, damaging the gravity stabilizers and causing the station to begin falling into KG-348. The station was ultimately destroyed when it burned up in the planet's atmosphere.