Voyager 2 was launched first, on August 20, 1977. On September 5, Voyager 1 followed its twin into space. Because of the constantly changing relationships among the planets, Voyager 1 arrived at Jupiter first, in March 1979. Voyager 2 made its closest pass on July 9, 1979.
Voyager 1 discovered that Jupiter was a ringed planet, like Saturn, but with rings that could not be seen from Earth. The Voyagers also imaged the Jovian moons Amalthea, Io, Europa, Ganymede and Callisto, revealing their surface features for the first time. Io seemed the most interesting from the Voyager data, with entirely unexpected active volcanoes continually resurfacing the moon.
With both spacecraft still operating very well, they were targeted slightly differently for their Saturn encounters. Voyager 1 was aimed to make a close approach to the second largest moon in the solar system, Titan. After this encounter, it would slowly leave the solar system without visiting any other planets. But JPL's navigators gave Voyager 2 a trajectory that would use Saturn's gravity to aim the spacecraft at Uranus, continuing the Grand Tour.
Voyager 1 reached Saturn in November 1979, with Voyager 2 following in August 1981. At Saturn, the two spacecraft discovered new rings, imaged moons that could not be seen from Earth and examined Saturn's atmosphere. Voyager 1's survey of Saturn's largest moon, Titan was somewhat disappointing. The moon's atmosphere was completely opaque, and Voyager's images revealed only a fuzzy orange ball. But the atmosphere was denser than Earth's, composed primarily of molecular nitrogen, with the orange color apparently coming from methane. Titan was so cold that methane seemed to act like water on Earth, cycling between solid and liquid forms on the surface, and liquid and gaseous forms in the atmosphere.
Jupiter's Great Red Spot, seen by Voyager 2 in July 1979. + Full image
Voyager 1 captured this view of Titan's thick haze layer in November 1980. + Full image
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