The question of engineering lifeless planets so that they can support a terrestrial biota raises new and interesting questions in environmental ethics that involves extending our perspective from here on Earth. Whilst progress in natural science will ultimately decide whether terraforming can be done, it is to ethics that we must turn to ask whether it should be done. In this paper, three geocentric ethical theories, homocentrism, zoocentrism and biocentrism, are used to address the question of ecopoiesing or terraforming Mars. We conclude that none of them rule out such a venture as necessarily immoral. However, one can conceive of a cosmocentric ethic that extends the moral universe outwards from the Earth in which certain cosmic objects are accorded intrinsic worth due to their uniqueness. The permissibility of terraforming within an ethical framework such as this is less clear.