Life in the Universe - Its Origins and Limits Contemplating the beauty of the deep skies on a dark moonless night, in the countryside away from the luminous contamination of civilisation, who has not thought about the possibility of life elsewhere in the Universe? This question, recurrent throughout the history of our civilisation, has had different answers according to the context in which was asked, giving rise to many different myths and beliefs. This very simple thought carries implicitly a long list of related questions: Is our planet the only one in the whole Universe with life? And if this is the case, why and how did life originate on Earth? Or, if life is universal, existing in other parts of the Universe, is it possible that life originated elsewhere and was later transported to Earth - the "Panspermia hypothesis"? Is life a cosmic imperative and only requieres convenient conditions for it to begin? Could life exist, based on components entirely different from those used here on our Blue Planet....? And what about the origins of life? How come that life is apparently able to adapt to extreme conditions - of which we find more and more examples here on Earth? Most of the questions in this endless chain have no adequate answer (yet). Thanks to the impressive progress of scientific and technical knowledge in recent times, a systematic study is now underway to try to answer the vital question: are we alone? But what is life? However, before we ask this most basic question, we need a definition of life. Until now, a clear definition has been elusive. We now know much about the living organisms on Earth and the conditions that are needed for them to exist, but the combined knowledge we have gained so far is still not sufficient to answer this apparently simple question.