Astrobiology is an expanding multidisciplinary scientific research field. It touches upon some very old questions about where we come from, about the possibilities for life, and about the prospects for humanity. As a scientific multidisciplinary field, it focuses upon the origin, evolution and future of life. Formal definitions of ‘astrobiology’ (including the definition used in the White Paper that follows) tend to cite these matters. Astrobiology does not, however, simply repeat familiar ways of looking at our origins and life’s evolution and future. Its newness is genuinely new. An exploration of the practices of a contemporary astrobiologist and of someone like the ancient poet Lucretius, speculating about these same matters but separated by two millennia of time, would show many differences. The most obvious difference is that astrobiology, unlike even the most remarkable examples of early speculation, brings a scientific rigour to longstanding questions about life, allowing them to be posed in new ways, in the light of a large body of discoveries across a range of scientific disciplines.