Image of Voyager spacecraft Courtesy of NASA/JPL

Unexpected discoveries made by the two Voyager spacecrafts during their visits to the four largest planets in our solar system have changed the field of space science.

Voyager 2 was launched on Aug. 20, 1977, followed by Voyager 1 on September 5, 1977. Both encountered Jupiter in 1979, returning photographs and information on its many moons. Scientists also learned about Jupiter's Great Red Spot and Io's volcanoes.

Voyagers 1 and 2 then continued to Saturn and its Rings. Voyager 2 then headed for Uranus and Neptune. It gave us our first close-up look at the two planets.

The Voyager missions discovered a total of 21 new moons. The two spacecrafts are very close to reaching interstellar space, where no spacecraft has ever been!