Voyager's epic journey: How long would it take you? Click to watch Voyager 1 and 2's original mission was to explore Jupiter, Saturn, Uranus and Neptune. Launched in 1977, scientists did not imagine that the twin spacecraft would continue their journey for more than three and a half decades. The spacecraft reached Jupiter in 1979. Their fly-by enabled scientists to bolster our understanding of the planet's Great Red Spot; a series of intense storms. While passing Io, one of Jupiter's moons, Voyager had first sight of volcanic activity beyond Earth. Voyager 1 discovered that Saturn's atmosphere was almost entirely made of hydrogen and helium gas, making it the only planet less dense than water. The spacecraft was then diverted towards Titan, one of the planet's moons. After its fly-by of Saturn, Voyager 2 headed for Uranus and Neptune. Click to enlarge In January 1986, nine years after its launch, Voyager 2 came within 81,500km (50,600 miles) of Uranus, revealing unknown details of the planet's rings and taking pictures of 10 previously unseen moons. As it became clear that Voyager would travel beyond the outer planets to the farthest reaches of the Solar System, preparations were made to keep scientists in touch with the probes. As a result, the Deep Space Network upgraded its antennas during the 1980s. In 1989 Voyager 2 became the first spacecraft to observe Neptune. Like Jupiter, Saturn and Uranus before it, Neptune was also observed to be a giant planet made of gas. Voyager took striking images of Neptune's rings. Neptune was the final planet that Voyager visited. After passing Neptune, scientists turned Voyager 1's cameras back toward Earth. The result was a humbling image of our planet, taken from more than six billion kilometres (four billion miles) away - a picture that astronomer Carl Sagan referred to as "The Pale Blue Dot." Over the decades, since the mission's inception, Dr Ed Stone has coordinated the Voyagers' study of Jupiter, Saturn, Uranus, Neptune, the outer heliosphere and the search for the edge of interstellar space. You've reached Voyager 1's current location Voyager took 36 years to travel 18.7 billion km By John Walton, Helene Sears, Steven Connor, Josephine Lie, Christi Sodano, Tom Maslen, Steven Atherton and Martyn Rees