Basis

Basis is the largest moon orbiting the planet Threshold in the Soell system. The diameter of this moon is 23,848km (14,818 miles), double that that of Earth. The gravity meter is the same though. 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 Alpha Halo.

The atmosphere of the moon beholds a sundown-modeled appearance, with hazy clouds and an orange skyline.

Trivia

 * On Burial Mounds, you can see wreckage from Installation 04 falling into the atmosphere and burning up.
 * Originally, the level The Arbiter was suppose to take place on the moon Basis.
 * When Basis is seen in Halo: Combat Evolved, it is just a picture of Mars, tinted blue.