by 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 golden record is visible over his left shoulder. Credit – NASA/JPL Caltech
Steve Synnott never forgot the day Ed Stone let him name a moon. It was 1980 and Synnott was a member of the navigation team for the Voyager 1 and Voyager 2 spacecraft, which had just reconnected with Jupiter. Stone was the Voyager project scientist: NASA-speak as the program leader. During the Voyagers’ close pass of the Jovian system, one of the ships captured an image – and then several images – of a small object orbiting the giant planet at a speed it saw completing more than one revolution every Earth day. Size and velocity and height could only mean it was a moon.
However such a discovery did not mean that the likes of Synnott were allowed to present themselves in Stone’s office, so the young engineer waited until the project chief made one of his frequent trips on the Voyager bullpens, then he approached him and showed him. a letter he planned to send to the International Astronomical Union (IAU)—which catalogs new space objects and approves the object’s name. Synnott handed Stone a one-paragraph communication and waited while the senior scientist read it.
“Do you know its orbital period?” Stone asked when it was done, according to a conversation I had with Synnott when I was writing the book. Journey Over Selene.
“About 18 hours,” Synnott replied, handing Stone a page of calculations.
“To what extent?”
“About 60 miles.”
“Height?”
“One hundred and thirty-eight thousand.”
Stone reread the letter and then rescanned the calculations. “Well,” he said at last, with a smile, “looks like you got yourself a moon.”
Synnott came back, sent his letter to the IAU, and received a long reply, which included a list of mythological names he could choose for the moon. He settled on Thebe, a nymph of the Greek god Zeus and the Roman god Jupiter, and with that, the solar system only got a little bigger.
Stone—who died on June 9, 2024, at the age of 88 of undisclosed causes, after half a century as leader of the Voyager program—could be as generous as his moons. His Voyagers would eventually find 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 the Jovian moon Io. The Voyagers were launched in 1977, and are currently beyond the boundaries of the solar system itself, traveling in interstellar space – still doing science, still beaming back data, having outlived man who gave birth to a midwife on them and who flew them and saw them through most of them. great campaign, until he retired in 2022.
“Ed Stone was a tracker who was terrified of terrible things in space. He was a great friend to all who knew him, and a great mentor to me personally,” Nicola Fox, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington, said in an official statement. “Ed took humanity on a planetary journey around our solar system and beyond, sending NASA where no spacecraft had gone before.”
It was in 1966 that NASA astronomers, studying the orbits of the four outer planets, discovered, 13 years later, in 1979, that the worlds form a neat alignment, falling into a paradis once every 176 years that would allow one . a ship—or, better still, a pair of ships—to visit them all in one trip. That gave the space agency 11 years to design and build and launch the ships—to say nothing of getting them approved and funded in the first place. For the first six years of the project, things only moved along appropriately, so in 1972, NASA’s Jet Propulsion Laboratory (JPL), in Pasadena Calif., which was overseeing the mission, turned Voyager’s reins over to Stone, and then 36 years. -year old physicist. It was a smart choice and a calculated gamble.
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Stone joined Caltech, which co-manages JPL with NASA, in 1964, studying space radiation. He has worked on several NASA satellite missions, but has yet to hold a leadership position. NASA brass recognized his native smarts, however; even before joining Caltech, he collaborated 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 – helping find out why photography was done. film on board spacecraft was forever being fogged by the energetic storms. That talent was just what Voyager needed, but whether Stone had the leadership chips to run the program was unknown. It turned out that he did.
Stone helped fund and drive the engineering of the Voyager project, especially when he repeatedly told lawmakers and engineers that if NASA didn’t take advantage of planetary alignment now, it would have to wait. until 2153 for the next one. shot. Ultimately, both spacecraft would make it on time, with Voyager 2 leaving the Florida launch pad first, on August 20, 1977, and Voyager 1 – which was to fly slightly faster and on a slightly shorter path and therefore it will reach Jupiter first. September 5, 1977.
Even then, there was no guarantee that NASA’s budget would support visiting all four planets over a period of more than 10 years, and, officially, Jupiter and Saturn were the only worlds on the program travel for both spacecraft. With that being the case, Stone decided 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 up, putting it on track for a close flyby of Saturn’s moon Titan, a world covered in a thick vortex organic methane and ethane that have long interested scientists. But once it was committed to that route, the spacecraft would not have enough fuel on board to reverse course, so it would go up and out of the plane of the solar system.
Voyager 2, which also flew past Jupiter and Saturn, would continue to fly in the flat, able to make close approaches to Uranus and Neptune if the will and budget were there to allow the missions. While Stone nursed his spacecraft, NASA brass managed to get their budget, and eventually won funding to keep Voyager 2 flying. On January 28, 1986—incredibly, the same day the shuttle Challenger exploded—Voyager 2 flew by Uranus, studying the planet’s largest moons, discovering 11 new ones, and mapping its thin rings. On August 25, 1989, the ship flew by Neptune, discovering two new moons, five fine rings, and a deep-sized bruise in the atmosphere, known as the Great Dark Spot – a huge storm, where winds reach 1,000 miles per hour. He also discovered icy geysers on Neptune’s moon Triton. Voyager 2 is the only ship to visit both of those worlds.
Even then, the Voyagers weren’t finished—and neither was Stone. The spacecraft is powered by radioactive generators, capable of providing energy for 50 years or more, and, although they are transmitting back to Earth with a signal of less wattage than a refrigerator bulb, for they could continue their work, speeding to the edge of the sun. system – and then disappearing. Voyager 1 entered interstellar space on August 25, 2012, and is now more than 15 billion miles away. (24 billion km) from Earth. Voyager 2 left the solar system on November 5, 2018, and is more than 12.5 billion mi. (20 billion km) away. Both crafts continue to whisper hoarsely back to us.
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Stone would be distinguished by more than just the Voyagers. He was the director of JPL from 1991 to 2001, and was in charge when the Sojourner spacecraft – the first Mars rover – landed on the Red Planet in 1997. In all, he was the principal investigator on nine missions of NASA and co-investigator on five others. .
However, he is best known for the Voyagers. The golden record ships are famous – created by another lost space legend, Carl Sagan. If an alien civilization ever found the spacecraft and played the records on a simple turntable — the state of the universe when the ships were launched — they would see 119 pictures of our planet, as well as hear greetings in 55 languages, and 27 music selections, including Javanese, Japanese, Chinese and Peruvian music; samplings 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 quite young, Saturday Night Live announced that an alien civilization had intercepted the ships, played the records, and sent back a four-word message – one that would appear to lie-. up from that week’s cover of TIME magazine, shown by host Steve Martin. The four words were: “Send More Chuck Berry.”
History does not record whether Ed Stone was watching that night, but, in time, he probably saw the sketch and laughed. And then he returned to the post. The Voyagers were still flying, which meant he was still working. He kept at it for the last two years of his life. Now, his ships – interstellar explorers of the human species – sail on without him. Hello, Ed Stone.
Write to Jeffrey Kluger at jeffrey.kluger@time.com.
