Terraforming

Terraform is 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.

However, the term is also used interchangeably for the same process but for other species; the Ice Warriors attempted to terraform Earth in the early 21st century - the correct term should have been 'areform.' (DW: The Seeds of Death)

Similarly the Cthalctose also created a terraforming device which sparked the Agent Yellow crisis in the early 21st century, but to be pedantic neither of these examples are of genuine 'terraforming'. (NA: Eternity Weeps)

When Mitzi, the first cat to go into hyperspace, went into space, she landed on the planet Photris, which was also Terraformed. (DWA: The Cat Came Back)

However, by the 26th century Mars had been completely terraformed by humans to make it habitable, melting the icecaps and installing a gravity net provided for an Earth like planet (albeit with less gravity and more UV light). (NA: GodEngine, BNA: Beige Planet Mars)

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. (DW: The Doctor's Daughter)