Photos: Voyagers: Strange visitors to other planets

Voyager 2 launched on August 20, 1977, and Voyager 1 followed on September 5, 1977, for what was originally a five-year mission to study Jupiter and Saturn. Their duties were extended to include the first visits to Uranus and Neptune. Now, still working after 30 years, Voyager 1 is the first man-made object to reach interstellar space and Voyager 2 is not far behind.

This gallery will explore some of the Voyagers' most important scientific discoveries and take a look at the message they carry to any alien life forms they may encounter.

Voyager 2 was Earth's first visitor to Neptune and its Great Dark Spot.