Ed Stone, former director of JPL and project scientist for the Voyager mission, in front of a mock-up of one of the Voyager spacecraft. The gold plate is visible over his left shoulder. Credit – NASA/JPL Caltech
STeve Synnott never forgot the day Ed Stone made him name a moon. It was 1980, and Synnott was a member of the navigation team of the Voyager 1 and Voyager 2 spacecraft, which had just explored Jupiter. Stone was the Voyager project scientist: NASA spokesperson as head of the program. During the Voyagers’ brief passage through the Jovian system, one of the ships captured an image — and then several images — of a small object zooming around the giant planet at a speed that caused it to complete more than one revolution every Earth day. Its size, speed and height could only mean it was a moon.
Even such a momentous discovery didn’t mean the likes of Synnott had to leave to simply present themselves at Stone’s office, so the young engineer waited until the project chief was taking one of his frequent walks through the Voyager bullpens, then approached him and showed up him seeing a letter he planned to send to the International Astronomical Union (IAU), which catalogs new space objects and approves the name an object will bear. Synnott handed Stone the one-paragraph message and waited while the senior scientist read it.
“Do you know its orbital period?” Stone asked when he was done, according to a conversation I had with Synnott while I was writing the book Travel beyond Selene.
“About 18 hours,” Synnott replied, handing Stone a page of calculations.
“His size?”
“About 60 miles.”
“Height?”
“One hundred and thirty-eight thousand miles.”
Stone reread the letter and then rescanned the calculations. “Well,” he finally said with a smile, “it looks like you found a moon.”
Synnott beamed back, sent his letter to the IAU and eventually received a response, including a list of mythological names he could choose for the moon. He settled on Thebes, a nymph of the Greek god Zeus and the Roman god Jupiter, and with that the solar system expanded just a little bit.
Stone – who died of unknown causes on June 9, 2024 at the age of 88, after half a century as head of the Voyager program – could afford to be so generous with his moons. His Voyagers would eventually discover 48 of them, orbiting the four gas giants – Jupiter, Saturn, Uranus and Neptune – as well as previously unknown rings or partial rings around Jupiter, Uranus and Neptune, and volcanoes on Jupiter’s moon Io. The Voyagers were launched in 1977 and are currently beyond the boundaries of the solar system itself. They travel through interstellar space – still doing science, still sending back data, surviving the man who redeemed them and let them fly and helped them through most of their lives. great campaign, until his retirement in 2022.
“Ed Stone was a pioneer who dared mighty things in space. He was a dear friend to all who knew him, and a valued mentor to me personally,” said Nicola Fox, associate administrator of the Science Mission Directorate at NASA Headquarters in Washington, in an official statement. “Ed took humanity on a planetary tour of our solar system and beyond, sending NASA to places no spacecraft had gone before.”
It was in 1966 that NASA astronomers, studying the orbits of the four outer planets, discovered that thirteen years later, in 1979, the worlds would line up neatly and enter a once-in-176-year parade that a single ship – or better yet, a few ships – to visit them all at once. That gave the space agency eleven years to invent, build and launch the ships — not to mention get approval and funding for them. Things were uneventful for the first six years of the project, so NASA’s Jet Propulsion Laboratory (JPL), in Pasadena, California, which oversaw the mission, turned over the reins of Voyager to Stone in 1972, and then to a 36 year old. year old physicist. It was both a smart choice and a calculated gamble.
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Stone had joined Caltech, which operates JPL along with NASA, in 1964, where he studied space radiation. He worked on several NASA satellite missions, but had not yet held a leadership position. However, the NASA brass recognized his innate intelligence; Even before joining Caltech, he worked with the Department of Defense to design a spy satellite that both photographed Earth and, as a research bonus, measured the solar wind (the stream of charged particles flowing from the sun) to help determine why photographic film aboard spacecraft was forever fogged by the energetic storms. That kind of talent was exactly what Voyager needed, but whether Stone had the leadership skills to lead the program was unknown. It turns out he did.
Stone helped secure the funding and direct the engineering for the Voyager project, not least by repeatedly pointing out to lawmakers and engineers alike that if NASA did not take advantage of the planetary alignment now, it would have to wait until 2153 would have to wait for the next one. shot. Ultimately, both spacecraft would lift off on time, with Voyager 2 being the first to leave the Florida launch pad on August 20, 1977, and Voyager 1 – which would fly slightly faster and on a slightly shorter trajectory and thus be the first to reach Jupiter – on the 20 August 1977. September 5, 1977.
Even then, there was no guarantee that NASA’s budget would support a visit to all four planets over the course of more than a decade, and officially Jupiter and Saturn were the only worlds on the route for either spacecraft. That being the case, Stone made the decision to effectively throw away one of his ships. When Voyager 1 reached Saturn, it changed its trajectory so that it would swing under the ringed planet and then fly upward, putting it on course to fly close to Saturn’s giant moon Titan, a world covered in a thick haze of organic methane and ethane that has long fascinated scientists. But once the spacecraft ended up on that route, it wouldn’t have enough fuel on board to change course, so it would fly up and out of the plane of the solar system.
Voyager 2, which also passed by Jupiter and Saturn, would remain in the plains and could make a close approach to Uranus and Neptune if the will and the wallets were there to make the missions possible. While Stone tended his spacecraft, NASA managed the budget and ultimately won funding to keep Voyager 2 flying. On January 28, 1986 (poignantly, the same day the shuttle Challenger exploded), Voyager 2 passed by Uranus, studied the planet’s largest moons, discovered eleven new moons and mapped its thin rings. On August 25, 1989, the ship flew past Neptune and discovered two new moons, five fine rings and an Earth-sized blue spot in the atmosphere known as the Great Dark Spot: a gigantic storm with winds of 1,000 miles per hour. It also discovered icy geysers on the Neptunian moon Triton. Voyager 2 remains the only ship to visit these two worlds.
Even then, the Voyagers weren’t done, and neither was Stone. The spacecraft is powered by radiothermal generators that can provide energy for fifty years or more, and although they transmit back to Earth with a signal that has less wattage than a refrigerator light bulb, they could continue their work and quickly reach the edge of the solar energy to fly. system – and then shut down. Voyager 1 entered interstellar space on August 25, 2012 and is now more than 16 billion miles away. (24 billion km) from Earth. Voyager 2 left the solar system on November 5, 2018 and is over 20.5 billion kilometers long. (20 billion km) far away. Both vessels continue to whisper hoarsely back to us.
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Stone would distinguish himself for more than just the Voyagers. He was director of JPL from 1991 to 2001 and was at the helm when the Sojourner spacecraft – the first Mars rover – landed on the Red Planet in 1997. In total, he was a principal investigator on nine NASA missions and a co-investigator on five others. .
However, it is the Voyagers for which he is best known. The ships are famous for their gold plates, created by another lost space legend, Carl Sagan. If an alien civilization were to ever find the spacecraft and play the records on a simple turntable – the state of Earth’s technology at the time the ships were launched – they would see 119 pictures of our planet and hear greetings in 55 languages, and 27 music selections, including Javanese, Japanese, Chinese and Peruvian music; samples of Bach, Mozart and Beethoven; as well as ‘Johnny B. Goode’ by Chuck Berry and ‘Melancholy Blues’ by Louie Armstrong and his Hot Seven Band.
In 1978, when the Voyagers were still new and Stone was still relatively young, Saturday Night Live announced that an alien civilization had intercepted the ships, played the records and sent back a four-word message—a message that would appear on a fake -message. on the cover of that week’s TIME magazine, which featured host Steve Martin. The four words were: “Send more Chuck Berry.”
History does not record whether Ed Stone was watching that night, but over time he probably saw the sketch and laughed. And then he returned to work. The Voyagers were still flying, which meant he was still working. He continued with it throughout, except for the last two years of his life. Now his ships – interstellar emissaries of the human species – sail on without him. Godspeed, Ed Stone.
Write to Jeffrey Kluger at jeffrey.kluger@time.com.