Preface

Life in space, whether strange beings on distant worlds, or an expansion of our own species into the Solar System and beyond, is a very exciting idea. Humankind may currently stand on the verge of major discoveries and exciting progress in both areas. The discoveries of possibly life-related artefacts in a Martian meteorite, in a subsurface ocean on Europa, Titan or Enceladus, and in the atmospheres of extrasolar planets, for example, show how close we are to finding out at last whether the life that teems on our own planet is unique. Some increasingly sophisticated space missions are currently under way, such as Cassini, which has been exploring the Saturnian system and Titan, the Earth-like moon, since 2004; others are in preparation, such as the Mars Sample Return and the Jupiter Icy Moons Explorer missions. Plans to return to Venus, Mars, the Moon and Titan, to orbit Europa and to place giant planet-seeking telescopes in space are thus on the table. These and other advances promise rapid progress in the coming years.

This is a book that deals with possible habitats in our Solar System and beyond. We will define which places might be harbouring past, present or future life, or can be considered as ‘habitable’ in the sense that human life could survive, adapt or continue to evolve therein. The book will include a necessarily brief but pertinent definition of life as we know it on Earth and review it as a phenomenon, considering its origins, properties and potential; we will combine a discussion of present knowledge with informed speculation, bounded by scientific realism but using non-technical language. We will briefly review the origin of life in the Universe, the reasons for thinking it may be unique and reasons, in contrast, for believing it could be commonplace. We will also offer some thoughts on its destiny and on scientific discoveries yet to be made in areas we can barely apprehend at present. The main goal is to update the reader on the current situation in our Solar System and beyond, in terms of exploration for traces of past or present life and of the existence of conditions for habitable worlds. We also aim to provide and provoke thoughts about our distant horizons in this respect.