Basis

Basis is the largest natural satellite orbiting the gas giant Threshold in the Soell system. The diameter of this moon is 23,848km (14,818 miles), double that of Earth. Basis has a gravitational pull equivalent to that of Earth. Installation 04 was positioned in the Lagrange point between Basis and Threshold. After Installation 04's destruction, the Covenant Heretics built a makeshift camp on Basis, amid the wreckage from Alpha Halo.

Trivia

 * On Burial Mounds, wreckage from Installation 04 can be seen falling into the atmosphere and burning up.
 * Originally, the level The Arbiter was supposed to take place on the moon Basis, instead of the Gas Mine on Threshold.
 * In the first cinematic of Halo: Combat Evolved, as the Pillar of Autumn is hit by several plasma torpedoes and the camera pivots around the Autumn, one can catch a glimpse of Basis.
 * When Basis is seen in Halo: Combat Evolved, the surface texture is just a picture of Mars, tinted blue.
 * The blue coloring of Basis when seen from space is puzzling, considering that from the surface it has a hazy orange or rust-colored atmosphere and terrain. The ruddy atmospheric coloration from the ground is most likely a result of the ash and smoke thrown up by the flaming wreckage of Installation 04.