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 directed for 10 years starting in 1991. His daughter Susan Stone said that his health was deteriorating, but the cause of death was not yet known.
Dr. Stone launched his career as a physicist 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 — while he was a graduate student at the University of Chicago in 1957.
Over the next six decades, he designed some of the first scientific instruments for American satellites; oversaw construction of the WM Keck Observatory, which had the world’s two largest optical telescopes when it was completed in Hawaii in the mid-1990s; and led the creation of LIGO, a billion-dollar physics experiment that in 2015 produced the first direct observations of gravitational waves, ripples in space-time that had eluded scientists for years.
He is best known for serving as project scientist – and, less formally, chief spokesperson – for Voyager 1 and 2. Launched two weeks apart in 1977, five years after Dr. Stone was hired for the mission, the twin probes brought back fascinating discoveries. 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, returning to the origins of the project. “But we didn’t appreciate the scale of the discoveries that there would be.”
Both spacecraft visited Jupiter and Saturn, with Voyager 2 continuing on 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 into interstellar space, farther than any other man-made object in the universe. In addition to cameras and scientific instruments, they each carry a celestial message in a bottle: a gold-plated disc, designed with the help of astronomer Carl Sagan, containing sounds and images that would introduce potential aliens to the diversity of life on Earth. .
“It was a wonderful idea,” Dr. Stone told the Los Angeles Times in 2011, reflecting on the disk’s inclusion as Voyager 1 prepared to enter interstellar space. “At the time, though, just getting to Saturn was what I was focused on.”
Beginning in 1979, probes took the first close-up images of Europa, one of Jupiter’s moons, revealing the cracked and fractured surface of a frozen world that “looked like an ice floe,” as the Dr. Stone. They studied Saturn’s vast ring system; found evidence of a thick atmosphere rich in organic compounds on Saturn’s moon Titan; followed by 1,000 mph winds gusting across Neptune’s surface; and discovered five-mile-high geysers rising from the icy surface of Neptune’s largest moon, Triton.
One of the mission’s most striking early discoveries was the revelation of volcanic activity on Jupiter’s moon Io. It was the first time active ash-spewing volcanoes had been discovered outside of Earth, and it surprised scientists who thought the Moon would be much like Earth’s: inert, cratered, cold and dead.
“Time and time again, we found that nature was much more inventive than our models,” Dr. Stone told a Caltech interviewer.
As Voyager passed the outer planets, Dr. Stone appeared on the evening news and gave frequent interviews. While supervising 11 investigative teams and some 200 researchers, he was credited with accelerating the pace at which the team’s scientists announced their discoveries, leading daily meetings in which he sought to identify the most fascinating discoveries of the group, then working with the researchers to help make the material accessible to the general public.
“He was like this machine,” his former boss Norman Haynes, who served for three years as executive director of the Voyager project, told the New York Times in 1990. “You would wind it up and zoom in!” He spent all day getting things done.
Astronomer Bradford A. Smith, who led the team interpreting 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 never achieved by NASA” – a praise that resonated. by many 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 two or three people who made Voyager rock.”
The success of Voyager helped bring Dr. Stone to greater prominence, leading to his appointment as head of the Jet Propulsion Laboratory, or JPL, a renowned planetary science center run for NASA by Caltech. The laboratory faced budget cuts in the wake 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 lab tribute noted that Dr. Stone was the rare scientist involved in the mission that went furthest from the sun – Voyager – as well as the mission that came closest to the sun: the Parker Solar Probe, who flew over the crown. , the upper atmosphere of the Sun, in 2021.
“I keep wondering why the public is so interested in space,” Dr. Stone told the New York Times before taking up his position at JPL. “After all, it’s just basic science. The answer is that it gives us a sense of the future. When we stop discovering new things, the conception of the future will change. Space reminds us that there is still something to do, that life will continue to evolve. It gives us a direction, an arrow in time.
The oldest of two sons, Edward Carroll Stone Jr. was born in Knoxville, Iowa, on January 23, 1936. 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 his transistor apart and put it back together.
“I always wanted to know why something happens this way and not that way,” Dr. Stone recalls. “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 received a master’s degree in 1959 and a doctorate in physics in 1964. He had then married Alice Wickliffe, a fellow UChicago student. She died in December. Survivors include their two daughters, Susan and Janet Stone, and their two grandsons.
With his doctorate in hand, Dr. Stone joined with one of his former colleagues at the University of Chicago, Rochus “Robbie” Vogt, to help launch a space physics program at Caltech. He was named a full professor in 1976 and chaired the university’s division of physics, mathematics and astronomy in the mid-1980s, around the same time he began work on the Keck, a complex of twin 10 meter telescopes located near the summit of Mauna Kea in 1976. 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 was halted following protests from Native Hawaiians and other critics who opposed development of the site.
Colleagues described Dr. Stone as shy and determined, with little interest outside of physics. “My work is my relaxation,” he liked to say. He continued to work on Voyager for decades, juggling his teaching and research duties while garnering honors including the National Medal of Science in 1991 and the Shaw Prize in Astronomy in 2019, before retiring from the mission in 2022.
By that time, the probes had already traveled well beyond the orbits of Neptune and Pluto. Voyager 1, the more distant of the two, is now more than 25 billion miles from Earth and is still operational although engineers have had to find workarounds for computer chip malfunctions and other problems. communication. The spacecraft and its twin will eventually run out of power, although Dr. Stone proudly noted that the probes will “keep working forever,” drifting through the cosmos with their golden cargo and silent instruments.
“As far as what happens to me, nature will do what it wants, I understand,” he told the Los Angeles Times in 2011. “Even if I’m not here, we will continue to explore , to understand the science. I am optimistic about this.