In mankind"s never-ending search for life on other planets, Mars has always ranked among the most likely places to look, initially because of its nearness to the Earth and easily visible surface. Although astronomers have been searching for life on Mars since the 19th century, it was between 1960 and 1995 that the United States and the Soviet Union launched a total of 27 missions to Mars, with only nine actual successes. In a single, informative reference, "Mars" discusses the fundamental facts concerning this mysterious planet, including its mass, size, and atmosphere, as well as the various missions that helped planetary scientists document the geological history of Mars. This volume also describes Mars" seasons with their surface effects on the planet and how they have changed over time, as well as what is known and inferred about the composition and structure of the interior of Mars, including theories of planetary information, of an unusually iron-rich mantle, and of the planet"s paradoxically strong early magnetic field, which has now completely ended. Perfect for those interested in understanding the science and history behind the exploration of Mars, this volume opens the door to a whole new world of discovery.