How can life begin? How common is it elsewhere in the Universe? Written and edited by planetary scientists and astrobiologists, this textbook is an introduction to the origin and nature of life, the habitable environments in our Solar System and the search for exoplanets. This new edition has been thoroughly revised to take into account the latest developments in this field. It now covers arsenic-tolerant extremophiles, burgeoning successes in exoplanet detection, results of the Cassini-Huygens mission to Titan and a re-examination of the habitability of Mars. Ideal for introductory courses on the subject, the textbook is also suitable for self-study. It highlights important concepts and techniques in boxed summaries. There are questions and answers throughout the text, as well as exercises with full solutions. Online resources include electronic versions of figures from the book, example assignments and suggested answers and links to websites containing relevant video clips and news stories.