Where did we come from? Are we alone? Where are we going? These are the questions that define the field of astrobiology. New discoveries about life on Earth, the increasing numbers of extrasolar planets being identified, and the technologies being developed to locate and characterize Earth-like planets around other stars are continually challenging our views of nature and our connection to the rest of the universe. In this book, philosophers, historians, ethicists, and theologians provide the perspectives of their fields on the research and discoveries of astrobiology. A valuable resource for graduate students and researchers, the book provides an introduction to astrobiology, and explores subjects such as the implications of current origin of life research, the possible discovery of extraterrestrial microbial life, and the possibility of altering the environment of Mars.