Basis
From Halopedia, the Halo wiki
Summary
Politically nonalligned, Basis is the largest moon orbiting Threshold. Installation 04 was positioned between Basis and Threshold. After Installation 04's destruction, the Covenant heretics built a makeshift camp on Basis, amid the wreckage from the Halo.
While often thought to be the location of the Gas Mine, this is in fact Threshold. Basis is, however, the location of the Halo 2 multiplayer level Burial Mounds
