Seeking to reenergize Americans’ passion for the space program, the value of further exploration of the Moon, and the importance of human beings on the final frontier, Claude A. Piantadosi presents a rich history of American space exploration and its major achievements. He emphasizes the importance of reclaiming national command of our manned program and continuing our unmanned space missions, and he stresses the many adventures that still await us in the unfolding universe. Acknowledging space exploration’s practical and financial obstacles, Piantadosi challenges us to revitalize American leadership in space exploration in order to reap its scientific bounty. Piantadosi explains why space exploration, a captivating story of ambition, invention, and discovery, is also increasingly difficult and why space experts always seem to disagree. He argues that the future of the space program requires merging the practicalities of exploration with the constraints of human biology. Space science deals with the unknown, and the margin (and budget) for error is small. Lethal near-vacuum conditions, deadly cosmic radiation, microgravity, vast distances, and highly scattered resources remain immense physical problems. To forge ahead, America needs to develop affordable space transportation and flexible exploration strategies based in sound science. Piantadosi closes with suggestions for accomplishing these goals, combining his healthy skepticism as a scientist with an unshakable belief in space’s untapped—and wholly worthwhile—potential.