Mars BeckonsBy: John Noble Wilford The astronomer Percival Lowell envisioned a world threaded by canals and peopled by ancient, intelligent beings. The Viking spacecraft showed us a seemingly sterile planet with a salmon pink sky and sub Antarctic temperatures. In this swiftly paced and authoritative book, a Pulitzer Prize winning science writer traverses the vast physical and cognitive distances between Earth and Marsand between Lowells Mars and Vikingswhile