'Astrobiology' is a brand new field of science, encompassing research into the origins and limits of life on our own planet, and where life might exist beyond the Earth. But what actually is 'life' and how did it emerge on our own world? What are the most extreme conditions terrestrial life can tolerate? And which other planets and moons in our solar system, or even alien worlds we've now discovered orbiting distant stars, may harbour ET? Astrobiology attempts to address one of the most profound questions asked: are we alone...? The implications for society are profound either way, and the terrestrial and space exploration involved holds great public appeal: astrobiology is a great field for engaging the public with current science.