In the final days of summer in 1977, twin spacecrafts left Earth to explore the solar system. For more than a year, Voyager 1 and 2 quietly navigated space, winding their way through the asteroid belt beyond Mars and toward their first target, Jupiter. Then in early 1979, as though someone removed the cap from a fire hydrant, a stream of information burst back toward Earth. Voyager 1 started transmitting photos of Jupiter daily, the views unlike anything seen before. Every day, the gas planet would get bigger and the details crisper. “Jupiter and its largest moons are places now, not objects,” a New York Times journalist wrote in March 1979. Each new photo seemed more remarkable, more breathtaking, more pioneering than the last.
Carolyn Porco remembers watching Voyager images flashing on monitors that hung all over the Jet Propulsion Laboratory, even in the cafeteria, and feeling “almost overwhelmed with the newness of it all, the thrill.” The fire hydrant was still roaring in the early 1980s, when Porco joined the Voyager mission’s imaging team.
Porco was hired for her expertise on Saturn’s rings, the topic of her doctoral thesis at the California Institute of Technology. The year the Voyager spacecraft launched, astronomers on the ground discovered that Uranus had rings, too. Voyager 2 was on track for an encounter with the planet in 1986, and the team had needed specialists in planetary rings.
“I felt like someone just grabbed me by the hand and dragged me aboard a train destined for the most magnificent adventure ever conducted,” Porco said.
And what a scenic ride it was.
Together, Voyagers 1 and 2 returned photos of swirling storms on Jupiter, rows of ringlets around Saturn, the bluish haze of Uranus, and the Great Dark Spot on Neptune. The spacecraft photographed the planets’ moons, too, revealing icy cracks on Europa, a volcanic plume on Io, and intricate terrain on Triton. Voyager carried humanity’s eye deeper into the solar system than previous spacecraft had gone and made a proper introduction. The making of the mission and the tour of the outer planets have been chronicled in the documentary The Farthest, which aired this week on PBS and can be streamed online.
“No matter how you measure it, whether you measure the amount of mass or you measure the number of bodies, most of our solar system exists out beyond the orbits of the asteroids,” she said. “So we could not have claimed to know our own solar system until Voyager had toured the giant planets.”
Porco remembers fondly the peak of the Voyager mission, when it felt like scientists and engineers were learning something new every day. Engineers would gather around monitors at JPL and stare at the latest images, or pass around hard copies. Eventually, they’d gather their thoughts and give press conferences, where the photos would be shown and shared with journalists. “The public didn’t see those images until they were either shown on television or they were printed in magazines or newspapers,” Porco said.
Today, images of other planets in the solar system are uploaded online soon after the data returns to Earth, where they can be viewed by millions of people. The immediate dissemination of these photographs is a good thing, Porco said, but she misses the camaraderie that permeated JPL during the Voyager days. Porco leads the imaging team of the Cassini mission around Saturn, and doesn’t receive new images in a room full of people. “Images would come down, I’d be sitting in my office all alone,” she said.
That’s the thing about uncovering new worlds—you can only do it once. While Cassini provides dazzling views of Saturn, far better than anything the Voyager mission could have sent back, the photographs don’t shock as they did 40 years ago. The thrill of discovery isn’t quite the same.
“It’ll never happen like this again because we’ve been to all the planets and we’ve been to comets,” Porco said. “We’ve been all over the solar system now. We’ll never again have the kind of encounters that we had with Voyager, because we know too much now.”
It's true, we won't have those encounters—in our own solar system. To replicate Voyager’s wonders, we'll have to go somewhere else.