Mars has been visible in the night sky for thousands of years, but it is only recently that humans have begun to learn what the planet is really like. Early astronomers, believing they could see man-made canals through their telescopes, suggested that Mars was home to intelligent life. Was this true at one point in the planet's history—and could it support life in the future? Through detailed graphic organizers and full-color photographs, this volume examines what scientists know about life on Mars as well as what they seek to find out.