The probes were originally meant to visit just Jupiter and Saturn, but NASA scientists decided to extend the mission to include other planets after receiving stunning images and other data from the two gas giants.

Voyager 2seen above as it launches from the Kennedy Space Flight Center in Florida on August 20, 1977is still the only spacecraft to have visited Uranus and Neptune.

Today both Voyager probes are still going strong and are speeding toward the outer reaches of the solar system to explore what lies beyond our sun's sphere of influence. Now about 10 billion miles (16 billion kilometers) from the sun, Voyager 1 is farther from Earth than any other humanmade object.

Get highlights of the discoveries made so far by the Voyager mission, and find out what scientists hope the craft will teach us about our solar system's final frontier.

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