  A hard difficulty in Astrobiology is the precise definition of what life is.
All living beings have a cellular structure, so it is not possible to have a
broader concept of life hence the search for extraterrestrial life is
restricted to extraterrestrial cells. Earth is an astronomical rarity because
it is difficult for a planet to present liquid water on the surface. Two
antagonistic bioethical principles arise: planetary protection and
terraforming. Planetary protection is based on the fear of interplanetary
cross-infection and possible ecological damages caused by alien living beings.
Terraforming is the intention of modifying the environmental conditions of the
neighbouring planets in such a way that human colonisation would be possible.
The synthesis of this antagonism is ecopoiesis, a concept related to the
creation of new ecosystems in other planets. Since all the multicellular
biodiversity requires oxygen to survive, only extremophile microorganisms could
survive in other planets. So, it could be carried out a simulation of a
meteorite by taking to other planets portions of the terrestrial permafrost, or
ocean or soil, so that if a single species could grow, a new ecosystem would
start, as well as a new Natural History. As a conclusion, ecopoiesis should be
the bioethical principle to guide practices and research in Astrobiology.
