NeptuneThe unmanned space probe Voyager 2, almost exactly 12 years after leaving Earth, visits its last planet in the solar system, Neptune. Since mission planners have no further targets for Voyager, they have a free hand in picking its final destinations. An extremely close trajectory over Neptune’s north pole, bringing Voyager 2 within 18,000 miles of the cloudtops of the solar system’s windiest planet, deflects Voyager downward behind Neptune for a close look at its large moon, Triton. Six new moons are discovered, and the “ring arcs” that astronomers have theorized for years turn out to be complete rings made of extremely dark material. After the surprisingly featureless face of Uranus, Neptune proves to be unexpectedly active, with a large dark storm dominating its atmosphere.