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
Climate of Uranus equinoxes. A similar periodic variation, with maxima at the solstices, has been noted in microwave measurements of the deep troposphere begun in the 1960s. Stratospheric temperature measurements beginning in the 1970s also showed maximum values near 1986 solstice. The majority of this variability is believed to occur due to changes in the viewing geometry. Uranus is an oblate spheroid, which causes its visible area to become larger when viewed from the poles. This explains in part its brighter appearance at solstices. Uranus is also known to exhibit strong meridional variations in albedo (see above). For instance, the south polar region