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). 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. Basis was the location of the Halo 2 multiplayer level Burial Mounds. The atmosphere 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 atmoshpere and burning up.
 * Originally, the level The Arbiter was suppose to take place on the moon Basis.
 * When Basis is seen from Halo CE, it is just a picture of Mars, tinted blue.
 * Basis has a diameter almost double that of Earth, and yet the gravity on Burial Mounds is almost exactly the same.