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 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 supposed to take place on the moon Basis, instead of Threshold.
 * In the first cinematic of Halo: CE, as the Pillar of Autumn was hit by several Plasma Torpedoes and the camera pivots around the Pillar, you can catch a glimpse of the blue moon Basis.
 * When Basis is seen in Halo: Combat Evolved, it is just a picture of Mars, tinted blue.
 * Despite having a much larger mass the gravity on Basis is about the same as Earth's.