His death was announced by the California Institute of Technology, where he was professor emeritus of physics, and by NASA’s Jet Propulsion Laboratory, which he headed for ten years from 1991. His daughter Susan Stone said his health was deteriorating, but the cause of death was not yet known.
Dr. Stone began his career in physics at the dawn of the Space Age, turning his attention to the cosmos after the Soviet Union launched Sputnik — a shiny metal ball that became the world’s first artificial satellite — when he was a graduate student at the University of Chicago in 1957.
Over the next sixty years he designed some of the first scientific instruments for American satellites; oversaw the construction of the WM Keck Observatory, which had the two largest optical telescopes in the world when it was completed in Hawaii in the mid-1990s; and led the creation of LIGO, a billion-dollar physics experiment that in 2015 made the first direct observations of gravitational waves, ripples in spacetime that had eluded scientists for years.
He remained best known as project scientist – and, less officially, chief spokesperson – for Voyager 1 and 2. The twin probes were launched two weeks apart in 1977, five years after Dr. Stone was hired for the mission. photos of the giant outer planets and their moons, as well as a wealth of data about the solar system.
“We were on a mission of discovery,” he told the New York Times in 2002, looking back on the project’s origins. “But we didn’t realize how many discoveries would happen.”
Both spacecraft visited Jupiter and Saturn, while Voyager 2 continued to Uranus and Neptune, aided by a rare alignment of the outer planets that occurs once every 176 years. The one-ton probes now travel through interstellar space, farther than any other man-made object in the universe. Along with cameras and scientific instruments, they each carry a heavenly message-in-a-bottle: a gold-plated record, devised with the help of astronomer Carl Sagan, containing sounds and images that introduce potential aliens to the diversity of life on earth. .
“It was a wonderful idea,” said Dr. Stone in 2011 to the Los Angeles Times, reflecting on the record’s recording as Voyager 1 prepared to enter interstellar space. “At the time, however, I was focused on reaching Saturn.”
Starting in 1979, the probes took the first close-up images of Europa, one of Jupiter’s moons, revealing the cracked, broken surface of a frozen world that “looked like a pack of ice,” as Dr. Stone put it. They studied Saturn’s massive ring system; found evidence of a thick atmosphere rich in organic compounds on Saturn’s moon Titan; tracked 1,000 mph wind gusts on Neptune’s surface; and discovered five mile-high geysers erupting from the icy surface of Neptune’s largest moon, Triton.
One of the mission’s most striking early findings was the revelation of volcanic activity on Jupiter’s moon Io. It was the first time active, ash-spewing volcanoes had been discovered outside Earth, and it surprised scientists who assumed the moon would be much like Earth’s: inert, cratered, cold and dead.
“Time and time again, we discovered that nature was far more inventive than our models,” said Dr. Stone to a Caltech interviewer.
As Voyager passed over the outer planets, Dr. Stone on the nightly news and gave regular interviews. While he oversaw eleven research teams and some two hundred researchers, he was credited with accelerating the pace at which the team’s scientists announced their findings, leading daily meetings in which he sought to identify the group’s most fascinating findings , and then work with researchers to make the material accessible to a general audience.
“It looked like this machine,” his former boss Norman Haynes, who was Voyager’s general project director for three years, told the New York Times in 1990. “You’d wind him up and zoom him!” He was running around all day trying to get things done.”
Astronomer Bradford A. Smith, who led the team that interpreted Voyager’s photos, told the newspaper in 2002 that the flood of images and data returned by the probes made Voyager “the most successful mission NASA has conducted.” – praise that has been echoed by numerous scientists over the years.
“What we know about the outer planets is a direct result of Ed Stone’s contribution,” A. Thomas Young, former director of NASA’s Goddard Space Flight Center, once said. “He was one of the two or three people who made Voyager so excited.”
The success of Voyager made Dr. Stone rose to wider prominence, leading to his appointment as head of the Jet Propulsion Laboratory, or JPL, a legendary planetary science center operated for NASA by Caltech. The laboratory faced budget cuts in the aftermath of the Cold War, although Dr. Stone still managed to work on high-profile missions, including Mars Pathfinder, which landed the Sojourner rover on Mars in 1997; the Galileo spacecraft, which orbited Jupiter for eight years; and Cassini, which orbited Saturn for 13 years.
A tribute from the laboratory noted that Dr. Stone was the rare scientist involved in the furthest mission from the Sun – Voyager – as well as the closest mission to the Sun – the Parker Solar Probe, which flew through the corona. , the Sun’s upper atmosphere, in 2021.
“I keep asking myself why there is so much public interest in space travel,” said Dr. Stone told the New York Times before taking over at JPL. “At the end of the day, it’s just basic science. The answer is that it gives us a sense of the future. If we stop discovering new things, the concept of the future will change. Space reminds us that there is still something to be done, that life will continue to evolve. It gives us direction, an arrow in time.”
The eldest of two sons, Edward Carroll Stone Jr., was born on January 23, 1936 in Knoxville, Iowa. He grew up in Burlington, Iowa, where his father ran a small construction company that his mother helped manage. His parents supported his early fascination with science, including his efforts to take apart and reassemble his transistor radio.
“I was always interested in why something is that way and not that way,” recalls Dr. Stone himself. “I wanted to understand, measure and observe.”
After graduating from Burlington Junior College (now Southeastern Community College) in 1956, he enrolled at the University of Chicago, where he earned a master’s degree in 1959 and a doctorate in physics in 1964. By then he had married Alice Wickliffe, a fellow UChicago student. She died in December. Survivors include their two daughters, Susan and Janet Stone, and two grandsons.
With his doctorate in hand, Dr. Stone joined one of his former UChicago colleagues, Rochus “Robbie” Vogt, in helping launch a space physics program at Caltech. He was appointed professor in 1976 and chaired the university’s physics, mathematics and astronomy department in the mid-1980s, around the same time he began work on the Keck, a complex of two 10-meter telescopes near the top of Mauna Kea in Hawaii.
His work on the project led him to champion the proposed Thirty Meter Telescope, an even larger observatory that scientists hoped to build nearby. Construction has been halted due to protests from Native Hawaiians and other critics opposed to development on the site.
Colleagues described Dr. Stone as shy and determined, with few interests outside physics. “My work is my relaxation,” he liked to say. He continued to work on Voyager for decades, combining teaching and research duties, while collecting awards such as the National Medal of Science in 1991 and the Shaw Prize in Astronomy in 2019, before retiring from the mission in 2022.
By then, the probes had already traveled far beyond the orbits of Neptune and Pluto. Voyager 1, the more distant of the two, is now more than 15 billion miles from Earth and is still operational, even though engineers have had to figure out solutions to faulty computer chips and other communications problems. The spacecraft and its twin will eventually run out of power, although Dr. Stone proudly noted that the probes will “go on forever,” drifting through the cosmos with their golden payload and silent instruments.
“As far as I’m concerned, nature will have its way, I understand that,” he told the Los Angeles Times in 2011. “Even if I’m not here, we’ll keep exploring and figuring out the science. I am optimistic about that.”