Substance

Substance is the name of the blue gas giant around which Installation 05 orbits. While not named during the game, the file containing the planet's graphics was found to be named "Substance." Similarly, there was a file called "Threshold and Basis" in Halo: Combat Evolved. It is unknown if there is a gas mine on Substance like Threshold, though it is probable. It may be similar to the planet Uranus due to it's color.