Terraforming

Terraforming is the process in which the terrain, climate and atmosphere of a planet is altered to suit the needs of those colonizing 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, depending on the degree of terraforming that is needed.

Human
Humanity uses terraforming processes to convert potential colonies into environments suitable for habitation. Modern humans first began to utilize terraforming technology during the colonization of the Sol system in the 22nd century, transforming many of the system's formerly inhospitable worlds into environments suited for human life. The colony ship Odyssey was the first ship to carry terraforming gear out of Sol in 2362.

The UNSC uses devices known as atmospheric processors to push a planet's atmosphere towards a more tolerable composition, but human terraforming technology has its limits. Many planets are so inhospitable that they cannot be terraformed, 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. The UNSC has used several methods to terraform worlds, such as bombarding a planet with asteroids to lay a new mantle and crust over the planet's natural one. This process is known to trap helium-3 into the second, artificial mantle. The colony world Verge was known to have required this type of terraforming. Similarly, some terraforming involves bombarding the planet with large ice chunks to establish a presence of water on the planetary surface and in the atmosphere. Such a process was used in terraforming the colony of Biko, with a large quarry established on the ice moon of Seoba to mine the ice needed for the operation, before launching it into Biko's gravity well via the use of a mass driver.

The UNSC often avoids establishing colonies on volcanically active worlds, as they are considered to be more difficult to terraform. Some species, such as Draco III's native naeori, were able to survive the UNSC's terraforming process by hiding deep below the surface of the planet's oceans. On certain colony worlds, such as Eridanus II, the local climate is artificially controlled to consistently maintain a pleasant weather.

After the Human-Covenant War, humanity began to re-terraform their colony worlds glassed by the Covenant during the conflict, including Reach. While initial assessments for re-terraforming made by the Assembly in 2530 indicated that restoring a glassed world would take from 110 to over 300 years, Reach had been at least partially restored by 2589, in only 37 years.

Covenant
The Covenant terraformed certain worlds solely to produce plasma to fuel their large-scale industry, engulfing said planets in perpetual violent thunderstorms; one planet engineered in such manner is Ealen IV.

The Flood
The Flood terraform their habitats through natural processes, converting the atmosphere 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 and covering entire worlds during the Forerunner-Flood war, generating enormous collectives known as Key Minds from the biomass gathered on the planet.

Human

 * Sol system
 * Venus - Failed terraforming project
 * Mars - Fully terraformed
 * Europa - Fully terraformed
 * Ganymede - Partially terraformed
 * Epsilon Eridani system
 * Reach - Reterraformed after glassing during the Fall of Reach
 * Draco system
 * Draco III - Terraformed
 * Kolaqoa system
 * Biko - Terraformed
 * Unknown systems
 * Verge - Terraformed

Covenant

 * Ealen system
 * Ealen IV - Harvested for plasma
 * Unknown systems
 * Verge - Harvested for plasma

List of appearances

 * Halo: The Fall of Reach
 * Halo: Combat Evolved
 * Halo 2
 * Halo: Ghosts of Onyx
 * Halo: Contact Harvest
 * Halo Legends
 * Origins
 * Halo: Evolutions - Essential Tales of the Halo Universe
 * Blunt Instruments
 * Halo: Reach
 * Data pads
 * Halo: Combat Evolved Anniversary
 * Terminals
 * Halo: Escalation
 * Halo 2: Anniversary
 * Halo: New Blood
 * Halo 5: Guardians
 * Halo: Silent Storm
 * Halo: Shadows of Reach