For thousands of years humans have gazed at the night sky and wondered about the presence of life elsewhere, whether in our solar system or on some other blue planet or body around another star. Such thoughts have found their expression in fiction, scientific missions and religions worldwide. Philosophers and ordinary people have pondered the rise of life on our planet. Creation myths are fundamental to every civilization and culture, and reflect the profound resonance of the question of our origins. Today, astronomers have pushed back our understanding of the origins of the universe to within tiny fractions of microseconds of the big bang. However, science cannot, as yet, offer any complete definition of life, nor yet point to the exact time, conditions and mechanisms when organic matter first went from nonliving to living. Just 50 years ago, humans began to extend their presence into space, first with robots and then with humans. As this tentative expansion of our species into other worlds continues, basic questions remain unanswered about the long-term adaptation of living organisms to other environments. For example, we do not know what the effect will be of living for years on Mars, where the pull of gravity is about one-third that of Earth. Astrobiology addresses all these compelling mysteries by embracing the study of the origin, evolution, distribution and future of life in the universe.