Our pale blue dot - Voyager spacecraft exploration mission
Last month, scientists at NASA’s Voyager spacecraft mission control predicted that the Voyager 1 spacecraft, launched in September 1977 to explore Jupiter and Saturn, would shortly leave our solar system altogether and so become the first man-made object to reach interstellar space.
Voyager 1 and its sister ship Voyager 2, which launched a few weeks earlier, have made some extraordinary observations during their 36 year and 18 billion kilometre missions, but are perhaps best known for each carrying a so-called golden record containing sounds and images selected to portray the diversity of life and culture on Earth.
The record is in fact a 30cm gold-plated copper disk encased in a protective aluminium jacket, together with a cartridge and a needle. Instructions engraved onto the record in pictorial symbols explain the origin of the spacecraft and indicate how the record is to be played. The 115 images are encoded in analogue form and depict Earth, our solar system, different human ethnic groups, a variety of Earth’s flora and fauna, as well as pictures of our transport and infrastructure. The remainder of the record is in audio (designed to be played at 16-2/3 revolutions per minute, no digital mp3 files back then) and contains recordings of different languages, animal sounds and music. Much like the Roman wooden writing tablets found at Vindolander, close to Hadrian’s wall in Northumberland, tell us so much about life in Britain 2,000 years ago, the Voyager message will help inform any extra-terrestrial scrap metal merchants and miners where there might be rich pickings.
As the late Carl Sagan, who chaired the committee that decided what message to send to space noted at the time, ‘The spacecraft will be encountered and the record played only if there are advanced spacefaring civilisations in interstellar space. But the launching of this bottle into the cosmic ocean says something very hopeful about life on this planet’. Very hopeful indeed, given that Voyager 1 is not expected to come close to another planetary system for at least 40,000 years, by which time life on Earth could be as extinct as Roman Britain.
But perhaps the most profound legacy of the two Voyager missions is more immediate and closer to home. Back in 1990, as the spacecraft passed beyond the orbit of Neptune, a young imaging scientist named Carolyn Porco persuaded NASA management to use precious mission time to turn Voyager to face back towards Earth and in doing so captured the famous Pale Blue Dot image, a mere 10 pixels within the overall image of our solar system beamed back, but a powerful reflection of just how small and fragile Earth is. This is it. There is no lifeboat, and we had better take care of it.
Carolyn Porco is now the leader of the imaging team on the Cassini mission launched in 1997 to explore Saturn and its moons. On 19 July 2013, in a repeat of the Voyager exercise, the Cassini cameras were turned to image Saturn and its entire ring system during the planet’s eclipse of the Sun. As Porco noted on her blog just before the picture was taken, ‘In the lower right, among the outer diffuse rings that encircle Saturn, will be a small speck of blue light with all of us on it’. I hope you were all smiling for the camera.