Astrobiology is an exciting interdisciplinary field that seeks to answer one of the most important and profound questions: are we alone? In this volume, leading international experts explore the frontiers of astrobiology, investigating the latest research questions that will fascinate a wide interdisciplinary audience at all levels. What is the earliest evidence for life on Earth? Where are the most likely sites for life in the solar system? Could life have evolved elsewhere in the galaxy? What are the best strategies for detecting intelligent extraterrestrial life? How many habitable or Earth-like exoplanets are there? Progress in astrobiology over the past decade has been rapid and, with evidence accumulating that Mars once hosted standing bodies of liquid water, the discovery of over 500 exoplanets, and new insights into how life began on Earth, the scientific search for our origins and place in the cosmos continues.