12: Our Messengers To The Cosmos
The totality of Voyager mission firsts and successes cannot be summarized easily. Launched in 1977, by 1989 Voyager-2 had already explored Neptune, the last planet in our solar system. James Green wrote an excellent summary of their achievements —
- Only spacecraft to visit Uranus and Neptune (Voyager 2) and first to image the rings of Jupiter, Uranus & Neptune
- First spacecraft to discover active volcanoes beyond Earth (Io) and multiple moons of the four outer planets: 3 new moons at Jupiter, four at Saturn, 11 at Uranus and 5 at Neptune
- First detection of lightning on a planet other than Earth (at Jupiter) and first suggestion of ocean beyond Earth (beneath the icy crust at Europa)
With troubles brewing elsewhere in NASA’s space programs, including the Challenger disaster, the Voyager missions continued to provide hope and encouragement to everyone.
Perhaps the most consequential image taken was when Voyager-1 looked back and took a snap of our Solar System. This family portrait was taken at a distance of 6 billion kms on Valentines Day 1990. One of them was dubbed the ‘Pale Blue Dot’, as Earth appears barely the size of a pixel. Behind the vastness of space, the fragility of our world is immensely clear. Carl Sagan was best at giving words to these emotions.
Our posturing, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.
This also marked the last time Voyagers got to use their camera as they would no longer fly close to any other astronomical object. It made more sense to save energy for other instruments as the Voyager mission went on.
Originally built to only last 5 years and visit 2 planets, these spacecrafts had already gone beyond our wildest expectations. And even though they showed signs of tiredness from their long journey, our workhorses were not done. Enough power and instrumentation capabilities were left to give them a new purpose. This purpose was to keep crossing scientific & physical boundaries.
Our Sun generates a tremendous amount of energy in the form of solar winds, which acts like a protective shield around the solar system. In Dec 2004, Voyager-1 crossed an interesting region of space called the termination shock, where this solar bubble encounters interstellar wind and heats up. This turbulent outer layer of the Sun’s bubble is called Heliosheath. In 2007, Voyager-2 also crossed the termination shock.
With their unprecedented speed, it was only a matter of time they went beyond Sun’s grasp. In 2012, Voyager-1 became the first human made object to reach true interstellar space. Voyager-2 achieved this feat in 2018. They were able to collect fascinating data, including detecting the full intensity of cosmic rays and making the first measurement of the interstellar magnetic field. Ultimately, helping us understand our protective shield better.
The two spacecrafts are expected to keep sending valuable data back as they ride through the cosmic ocean.
What happens when their fuel finally does run out? Well, not much really. Space is big so we don’t expect them to hit anything. And even without power, the probes are well insulated. A more interesting question is what if they get close to an intelligent species after we are long gone? For that exact purpose the spacecrafts carry a 12-inch gold-plated copper disk called the golden record. These records, similar to any other gramophone record, contain sounds and images of our planet. Not of one country or religion, but the entire planet.
The team that put this record together had to take care of representing the uniqueness of our beautiful planet Earth.
Given this monumental task, what this team was able to achieve is nothing short of a masterpiece. They captured — Earth’s natural sounds, such as those made by surf, wind, and thunder. Animal sounds, including the songs of birds, whales and dolphins. Music from various cultures, spoken greetings in fifty-nine languages and drawings depicting the human body and relative position of our Sun. Millennia from now, some other species will rediscover us.
The contents of this masterpiece were selected for NASA by a committee chaired by Carl Sagan. He also best summarized this effort -
“The launching of this bottle into the cosmic ocean says something very hopeful about life on this planet”.
The story of Voyagers is not complete without talking about the humans that built and operated it. It was their curiosity and imagination that guided the spacecrafts through their billion mile journey. Chief among this group is Ed Stone, who is the only person to serve as the chief scientist for Voyager missions. In 2022 the world celebrated the twin spacecrafts’ 45th anniversary. This is also the year Ed Stone decided to retire. He’ll forever be known as the person who led humanity into the interstellar age.
It’s like we sent our school science lab project on a multi-year journey around the solar system and they recorded as much information as possible. Then, as a faithful friend, sent all the data back to us. Ultimately, helping us to understand our own backyard better. They also paved the way for future missions to study a single planet in greater detail.
So next time when someone asks you why invest in space programs, hopefully the story of the Voyagers will inspire you to look beyond their monetary significance. For me the story of Voyager has become a story about us. Our willingness to cross boundaries, our ability to imagine and build new things, our capacity for working together and our innate desire to know more.