In the 1960s, intent on demonstrating the superiority of our military-industrial complex to the Soviet Union, we funded the space program to reach the moon. In the 1970s and 1980s, we began to justify space expenditures by touting Teflon pans, super metal alloys, and miniaturized ro-botics. Now a new rationale for planetary exploration has emerged-environmentalism. The more we know about other worlds, say space enthusiasts, the better we can tackle the environmental dilemmas that beset our own planet.

So argues planetary scientist David Harry Grinspoon of the University of Colorado at Boulder, in Venus Re-vealed: A New Look Below the Clouds of Our Mysterious Twin Planet, the first book to explain the findings of the Magellan mission. Expertly guiding the reader beneath the clouds that have long hidden Venus from earthbound eyes, Grinspoon celebrates Magellan and other spacecraft voyages that have increased our understanding of our sister planet's geology, climate, and atmosphere. At the same time, he acknowledges that these insights may not play well with a taxpaying public facing declining schools, disintegrating inner cities, overpopulation, and many other social ills. So throughout the book, Grinspoon emphasizes how missions like Magellan may lead to practical solutions to problems here on earth, such as ozone depletion, global warming, and acid rain.