Mars has always held a special interest because of the possibility that life may have existed there, and its water history is crucial to understanding its geology, climatology, and biology. Moreover, recent studies in molecular phylogeny suggest that volcanic hot springs, which may have been common in early Mars, are also the most likely point of origin for life on Earth. In this book, Dr. Carr explores the history of water on Mars, including evidence that liquid water was once abundant at the planet's surface; ways in which the climate might have changed to accommodate liquid water; and what...