This book aims at exploring several crucial issues related to the origin(s) and evolution of life in the Universe, starting from the only example of life known so far: terrestrial life. It is clear, though, that many of the circumstances that surrounded the emergence of life on Earth may have occurred, are occurring or will occur in other regions of our Galaxy or in other galaxies of our Universe. Therefore, the critical exploration of those conditions and the elaboration of models explaining the transition from the organic chemistry of the Universe to the biochemistry of terrestrial living forms are relevant at a much more global scale.

Just as with this volume, the field of astrobiology is by nature multidisciplinary. Astrophysicists, geologists, chemists, biologists, computer scientists and philosophers, as well as scientists working at the different interfaces between those disciplines, can all contribute to a better understanding of the processes and conditions that led to the emergence of life. The points of view and approaches of those different disciplines should not only superimpose, but also converge towards a unified explanation of the phenomenon of life in our Universe.

This book is an attempt to contribute to such an ambitious objective. It summarizes a series of lectures presented by selected speakers during two successive summer courses sponsored by the French Research Council (CNRS, Centre National de la Recherche Scientifique): Exobio'05 and Exobio'07, Ecole d'exobiologie du CNRS, which were respectively held in September 2005 and September 2007 in Propriano, Corsica (http://www.u-bordeaux1.fr/exobio07/).