Terraforming on Mars. Illustration of Mars after it has been made habitable. Dwellings have been built (at centre and at right) on the fertile landscape. Lightning (at left) arches down from clouds which add to a newly-formed sea (lower frame). The process of making barren planets habitable is known as terraforming. Terraforming would involve changing Mars' atmosphere to make it breathable, adding fertilising chemicals to the soil and releasing water ice from below the surface. Terraforming is technically feasible but would be enormously expensive and take many centuries.