[Review of Lonely Planets: The Natural Philosophy of Alien Life by David Grinspoon.] Not many scientists have the reputation of being witty or entertaining, even when their subject matter is rich with possibility. But more and more scientists are allowing their Renaissance sides to emerge and publishing books explaining complex, scientific subjects and debates in lively prose. David Grinspoon, principal scientist in the Department of Space Studies at Boulder's Southwest Research Institute and an adjunct professor of Astrophysical and Planetary Sciences at the University of Colorado, is one of those. His first book, "Venus Revealed" (1997) explored Earth's erstwhile "twin"...