ABSTRACT
Astrobiology, the study of Life in the Universe, is more precisely the study of the origins, evolution, distribution and destiny of life in the whole universe. This very wide and interdisciplinary domain thus includes not only the search for extraterrestrial life, but also the study of the origin and evolution of life on our planet.1'3 Although obvious, it is essential to remember that the Earth is so far the only place we know where life is present and that terrestrial life is the only example we have. Searching for a second example requires some assumptions about what is life, what an extraterrestrial living system is made of and how it can be detected.4
