What is Mars? From the ancients to the present, we have imagined Mars repeatedly and studied it longingly. As scientific knowledge of Mars has changed, so has the cultural imagination of this celestial neighbors. The earth-centered beginnings of astronomy connected the blood-red planet with the God of War. The Copernican Revolution and a later, simple mistranslation from Italian supported fantastic visions of distant Mars as the abode of life variously bizarre, ideal, or malignant. In the work of H. G. Wells and Orson Welles, in books, films, radio, and television, Mars reflected not only...