The Planet of Doubt Jupiter and Saturn and on the surface of Uranus itself. At the time "The Planet of Doubt" takes place at the turn of the 22nd century, the limited range of the spaceships ensures that Uranus can only be reached from the American base on Titan when Saturn reaches conjunction with Uranus, an event that occurs once every forty years. The Young expedition explored the planet's south pole in 2060; now Hammond takes his ship, the "Gaea", to the north pole. Finding an ocean at the north pole, Hammond sends the "Gaea" spiraling southeast until they reach land. They find the
Moons of Uranus of one or several small inner moons. The two innermost moons (Cordelia and Ophelia) are as shepherds of Uranus's ε ring, whereas the small moon Mab is a source of Uranus's outermost μ ring. There may be two additional small (2–7 km in radius) undiscovered shepherd moons located about 100 km exterior to Uranus' α and β rings. At 162 km, Puck is the largest of the inner moons of Uranus and the only one imaged by "Voyager 2" in any detail. Puck and Mab are the two outermost inner satellites of Uranus. All inner moons are dark objects; their