Messaline

Messaline was a planet colonized by humans and Hath.

Structure
Messaline was an Earth-like planet with a similar atmospheric composition, with a roughly 80:20 ratio of nitrogen and oxygen and high ozone levels. The main differences were the occasional radiation spikes on the surface and the lack of native life.

The surface of the planet, before terraforming, was cold and rocky with the occasional tar pit. (DW: The Doctor's Daughter)

Colonization
Messaline was colonized by humans and Hath in July 6012 of the New Byzantine Calendar. It was a barren world, so terraformation was planned to occur there to make the planet hospitable for the two species. However, when the mission commander died, there was a power vacuum. This power vacuum resulted in the two species taking part in a seven-day battle, although approximately 140 generations passed during the course of it. (DW: The Doctor's Daughter)

There was an outbreak of pacifism among the humans in the Eastern Zone, three generations before the Tenth Doctor's arrival.

Terraforming
When the Tenth Doctor destroyed the terraforming device and released the terraforming gases into the air, a peace was formed between the two races as they realized what the battle actually was about. The colonization of the planet continued as planned, and subsequently its terrain was transformed with the earlier release of gas from the terraforming device. (DW: The Doctor's Daughter)

Messaline