Terraforming

Terraform was a term used to describe the artificial altering of a planet's atmosphere and biology to create a world more suitable for human life. The word comes from 'Terra' meaning Earth.

Examples of Terraforming
When Mitzi, the first cat to go into hyperspace, went into space, she landed on the planet Photris, which was terraformed. (DWS: The Cat Came Back)

In late 25th century Planet Hollywood was terraformed a consortium of entertainment businesses. (NSA: Peacemaker)

By the 26th century Mars had been completely terraformed by humans to make it habitable. They melted the icecaps and installed a gravity to make an Earth-like planet (albeit with less gravity and more UV light). (NA: GodEngine, BNA: Beige Planet Mars) The Monk tried to help the Ice Warriors revert the changes, but was unsuccessful. (BFA: The Resurrection of Mars)

Before the 40th century, Io was terraformed to be used as the headquarters of the Galactic Federation. (NA: Legacy)

During the Second Great and Bountiful Human Empire, Agelaos was terraformed. (NSA: The Story of Martha: The Weeping)

In the 49th century Alfava Metraxis was terraformed. (DW: The Time of Angels)

The Source was a legendary creation myth for the people on the planet Messaline. The Doctor, Donna Noble, Martha Jones, and the Doctor's daughter Jenny discovered it was a terraforming device. The Doctor released the device to trigger the terraforming of Messaline in 6012. (DW: The Doctor's Daughter)

After Earth and Mars became uninhabitable, Pluto was terraformed by the Usurians. (DW: The Sun Makers)

Shanquis was terraformed using human technology. Even after the humans died out, the terraforming devices could be activated by spoken English. (CC: Bernice Summerfield and the Criminal Code)

Osphogus had been terraformed. It was still inhabitable 5,000 years later. (BFA: The One Doctor)

Similar Processes
Technically, terraforming was the transformation of a planet to a more Earth-like form, but other species had similar processes to adapt planets to a form more like their own homeplanet.

Theoretical Monsters: A Credibility Test referenced the Kalekani, a species who used a terraforming virus that converted land into flat grassland, effectively turning it into a golfcourse. Fitz Kreiner believed they were made up. (EDA: Interference - Book One)

In 1864, the Cei sent a terraforming device to Earth so that it could be used as an outpost. (BBCR: The Runaway Train)

In 1997, the Ice Warriors planned to wipe out the humans and terraform (more specifically, aresform) Earth, but they were unsuccessful. (NA: The Dying Days)

The Cthalctose created a terraforming device, called the Genesis of Cthalctose, which sparked the Agent Yellow crisis in 2003. (NA: Eternity Weeps)

Torchwood Three speculated that the Vandrogonite Visualiser was intended to be used as a terraforming device. (TWN: Pack Animals)

The Ice Warriors attempted to terraform Earth again in the early 21st century using a Martian fungus. (DW: The Seeds of Death)

In the 22nd century, the Daleks terraformed Antalin to resemble Skaro. (EDA: War of the Daleks)

The Daleks were somehow able to terraform Jupiter, turning it from a gas giant to a planet that humans could survive on. (BFDE: Dalek War: Chapter Two, Dalek War: Chapter Three)

Terraforming Technology and Companies

 * Geo-forming was like terraforming, but much faster. (BFDE: The Survivors)
 * WorldCorp and PlanetScape were both Human terraforming companies. (EDA: Dark Progeny)
 * Nooma was artificially created to test terraforming technology by the Aapex Corporation. (MA: Speed of Flight)
 * A Terran Federation ship carried terraforming equipment. The Sontarans took the ship and planned to use it to create cloning planets. (DWM: Pureblood)