In the summer of 1977 the twin Voyager spacecraft would embark on a remarkable ‘Grand Tour' of the Solar System.
They would visit the outer planets and capture images of worlds that had never been seen in such detail before, but the journey was only possible thanks to a scenario that occurs every 175 years.
NASA knew that rocket power could only get a spacecraft to Jupiter and no further, but in the mid 1960’s they discovered that in just over a decade later the outer planets would be aligned in such a way that the craft would receive a gravitational slingshot from each one allowing them to get as far as Neptune, some 4.5 billion km from Earth.
In August and September of 1977 Voyager 1 and 2 were launched, reaching their first destination of Jupiter in the spring and summer of 1979. They sent back spectacular images of Jupiter’s turbulent atmosphere and confirmed that the great red spot was indeed an enormous storm.
The craft then turned their attention to Jupiter’s moons, discovering that Io was volcanically active, that Europa had a frozen surface of water ice possibly covering an ocean of warm water, and that Ganymede was larger than the planet Mercury.
Voyager 1 and 2 arrived at Saturn a year apart, in June of 1980 and August of 1981. Scientists at NASA were bombarded with incredible images of Saturn’s rings sent by the twin spacecraft. They were discovered to be more complex than previously thought, with strange spokes of dust emanating from them that came and went, some rings were held in place by tiny shepherd moons while others were intertwined.
Saturn’s other moons were also surprising, some are scarred with huge craters more than a quarter of their size, it was evident that enormous collisions had taken place in the past and maybe some moons had been shattered completely. This led to some speculation that Saturn’s rings were made of debris from destroyed moons.
Most surprising of all was Titan, the Voyagers discovered that the moon was shrouded in a thick, orange, nitrogen based atmosphere, but unfortunately they didn’t possess the necessary equipment to peer through the clouds.
Saturn signaled the end of planetary exploration for Voyager 1 as its trajectory sent it out of the solar system, but Voyager 2 continued on to Uranus and Neptune, and is still the only spacecraft to have ever visited those planets.
Voyager 2 made one last amazing discovery before it too sped into the vastness of interstellar space. The images it sent back of Neptune’s largest moon Triton showed that it was geologically active, with plumes of nitrogen gas erupting from its surface, it was the last thing NASA scientists had expected at around 4.5 billion km from the sun.
After Voyager’s incredible discoveries our understanding of the solar system had to be re-written. Their achievements stretched the capabilities of mankind to the absolute limit and radically changed our perception of what was possible in the solar system. Incredibly both spacecraft still function and send back data to this day.
