More than four decades have passed since a human first set foot on the Moon. Great strides have been made in our understanding of what is required to support an

As civil space policies and programs have evolved, the geopolitical environment has changed dramatically. Although the U.S. space program was originally driven

“Expansive and enlightening. . . . Impey packs his prose with wonderful anecdotes and weird factoids.”—New York Times Book Review Human exploration has be

Natural and human-induced changes in Earth's interior, land surface, biosphere, atmosphere, and oceans affect all aspects of life. Understanding these changes r