The twin Voyager 1 and 2 spacecraft continue exploring where nothing from Earth has flown before. In the 25th year after their 1977 launches, they each are much farther away from Earth and the Sun than Pluto is and approaching the boundary region -- the heliopause -- where the Sun's dominance of the environment ends and interstellar space begins. Voyager 1, more than twice as distant as Pluto, is farther from Earth than any other human-made object and speeding outward at more than 17 kilometers per second (38,000 miles per hour). Both spacecraft are still sending scientific information about their surroundings through the Deep Space Network (DSN).

Interstellar Mission (Click on the image for a larger view)

The primary mission was the exploration of Jupiter and Saturn. After making a string of discoveries there -- such as active volcanoes on Jupiter's moon Io and intricacies of Saturn's rings -- the mission was extended. Voyager 2 went on to explore Uranus and Neptune, and is still the only spacecraft to have visited those outer planets. The adventurers' current mission, the Voyager Interstellar Mission (VIM), will explore the outermost edge of the Sun's domain. And beyond.