Basis

Basis is the largest natural satellite orbiting the gas giant Threshold in the Soell system. Silvery-gray in color, the moon is 23848 km in diameter, nearly double the size of Earth. Halo Installation 04 was positioned in the Lagrange point between Basis and Threshold. After Installation 04's destruction, a group of Covenant defectors built a makeshift camp on Basis, amid the wreckage from Alpha Halo. Debris from Installation 04 often rained down on Basis, creating small craters on the moon's surface. During a skirmish over Threshold following the Battle of Installation 04, Cortana maneuvered John-117's GA-TL1 Longsword into the gravity well of the moon to slingshot the fighter around Basis to avoid Covenant attacks.

After the war, Spartan-IVs were sent in reconnaissance on Basis to survey the debris of Alpha Halo scattered across the moon's surface. They used the VECTOR-class Mjolnir armor for the first time.

Trivia

 * Originally, the level The Arbiter was supposed to take place on the moon Basis, instead of the gas mine over Threshold.
 * Basis's texture in Halo: Combat Evolved appears to be a color-graded image of Mars's surface.
 * 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 may result from the ash and smoke thrown up by the flaming wreckage of Installation 04.

List of appearances

 * Halo: The Fall of Reach
 * Halo: Combat Evolved
 * Halo: The Flood
 * Adjunct
 * Halo: First Strike
 * Halo 2
 * Halo: Evolutions - Essential Tales of the Halo Universe
 * The Mona Lisa
 * Halo: Combat Evolved Anniversary
 * Halo 2: Anniversary
 * Terminals
 * Halo: Escalation
 * Halo 5: Guardians