REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Biology of the Universe and the Search for Extraterrestrial Life explores the origins of life through its chemistry and records in rocks and cells. Evidence dealing with the birth of the solar system and extraterrestrial life is presented. Ancient atmospheres and ancient surfaces are described, as are the effects of comets and meteorites. The structures of the important biological compunts are illustrated.