When we talk about colonising a planet like Mars, this usually involves 'Habs' or habitats that contain everything we need to live: like water, food and most importantly air. However, in movies, such as 'Man of Steel', they talk about Terraforming - using technology to change a planet's surface and atmosphere to make it suitable for life. Living in habitats seems like a temporary solution and one that is not very scaleable with population growth. Is it possible that we could eventually just change the atmosphere of a planet like Mars and make it similar to our own. Once we changed the atmosphere on Mars would it stay that way indefinitely?