Wikipedia There is more information available on this subject at Terraforming on the English Wikipedia.

Terraforming is the process in which a planet is changed or "formed" to suit the needs of those terraforming the planet. It normally involves inserting plants and/or flora, introducing new minerals or substances, or other changes to fulfill the required goals for the planet in question. It can take up to several centuries to fully terraform an Earth-sized planet, or even slightly larger. The UNSC uses terraforming processes to convert potential colonies into environments suitable for human habitation.[1] The UNSC Odyssey was the first UNSC ship to carry terraforming gear out of the Sol system.

The UNSC uses devices known as "Atmospheric Processors" to change a planet's atmosphere towards sustainability, but human terraforming technology has its limits. Completely uninhabitable planets cannot be rebuilt, which often results in the UNSC seeking already habitable planets. Understandably, these are extremely few and far between, which results in some colonies being extremely remote.[2] Still, the UNSC has several methods to terraform worlds, including a spallation-heavy process where another mantle is laid over the planet's natural one. This process is known to trap helium-3 into the second, artificial mantle. At least the colony world Verge was known to have required this type of terraforming.[3] After the Human-Covenant war, humanity began to re-terraform their colony worlds glassed by the Covenant during the conflict, possibly including Reach, which had been mostly glassed, but at least one area remained untouched by 2589 as evident by the fact that SPARTAN-B312's helmet remained unaltered in the time since their death in 2552.[4]

The Flood terraform their habitats through natural processes, converting the atmosphere[5] and using local biomass to spread itself until it can form a Flood Hive. Beginning as small spores, these eventually grow into larger clumps of biomass, which convert the areas atmosphere to what is presumably optimal for Flood expansion, and have been known to infect large areas, ranging from areas of Installation 05, to the planetoid High Charity.[6]



  1. Halo: Ghosts of Onyx
  2. Halo: Contact Harvest, chapter 1, page 32
  3. Halo: Evolutions - Essential Tales of the Halo Universe, Blunt Instruments, page 194
  4. Halo: Reach campaign level Lone Wolf
  5. Halo: Combat Evolved, The Library: 343 Guilty Spark: "Your environment suit will serve you well when the Flood begin to alter the atmosphere - you are a good planner!"
  6. Halo 2, level High Charity