Second in size only to Jupiter, bigger than a thousand Earths but light enough to float in water, home of cushing gravity and delicate, seemingly impossible rings, it dazzles and attracts us: Saturn.

Earth groans under the rule of fundamentalist political regimes. Crisis after crisis has given authoritarians the upper hand. Freedom and opportunity exist in space, for those with the nerve and skill to run the risks.

Now the governments of Earth are encouraging many of their most incorrigible dissidents to join a great ark on a one-way expedition, twice Jupiter’s distance from the Sun, to Saturn, the ringed planet that baffled Galileo and has fascinated astronomers ever since.

But humans will be human, on Earth or in the heavens — so amid the idealism permeating Space Habitat Goddard are many individuals with long-term schemes, each awaiting the right moment. And hidden from them is the greatest secret of all, the real purpose of this expedition, known to only a few…