It is only at the end of the world-among the glacial mountains, cleaving icebergs, and frigid waters of Antarctica-where Deb Gardner and Keller Sullivan feel at home. For the few blissful weeks they spend each year studying the habits of emperor and Ad�lie penguins, Deb and Keller can escape the frustrations and sorrows of their separate lives and find solace in their work and in each other. But Antarctica, like their fleeting romance, is tenuous,...