Novelists have “It was a dark and stormy night.” For planetary scientists, the equivalent cliche is, “We expect to be surprised.” The story of every new space mission seems to begin that way. No matter how intensely researchers study some solar-system object, no matter how they muster the best resources available on Earth, they are inevitably caught off-guard when they get to study it up close for the first time. And no matter how worn and familiar that cliche may sound, it also rings true e