This book is dedicated to my colleagues, whose unceasing efforts led to a resurgence of interest in the planet Mercury and eventually to reconsideration of return missions to Mercury despite the challenges. I would particularly like to recognize those who supported, encouraged, reviewed, and/or provided material to support our efforts, particularly, Susan McKenna Lawlor, who provided a great deal of initial input for the chapters on Mercury’s atmosphere and magnetosphere, as well as Steven Curtis, Rosemary Killen, Martha Leake, Faith Vilas, Ann Sprague, Barbara Giles, Clark Chapman, Joe Nuth, Jim Slavin, Bob Strom, Pontus Brandt, Norman Ness, Drew Potter, Mark Robinson, Ron Lepping, and Bill Smyth. I would also like especially to thank the staff of the NASA Goddard Space Flight Center library and the Café 10 for providing supportive environments.