Ed Stone, the scientist who led NASA's breakthrough Voyager mission to the outer planets for 50 years and led the Jet Propulsion Laboratory when it landed its first rover on Mars, died Tuesday. He was 88.
A physicist who got his start on the ground floor of space exploration, Stone played a leading role in NASA missions to Mars, Jupiter, Saturn, Uranus and Neptune. The discoveries made under his watch revolutionized scientists' understanding of the solar system and fueled humanity's ambition to explore distant worlds.
Carolyn Porco, who worked on imaging during JPL's Voyager and Cassini missions, called Stone “a thoroughly nice man” who was “as perfect as a project scientist could ever be.”
“When two science teams were arguing about a spacecraft, and Ed had to choose between the two, even the guy who lost walked away thinking, 'If this is what Ed decided, then it must be the right answer. '' Porco said by email on Tuesday. “I feel blessed to have known Ed. And like many people today, I am very sad to know that he is gone.
Stone was a 36-year-old physics professor at Caltech when he was asked in 1972 to serve as chief scientist for a daring plan to send a pair of spacecraft to explore the solar system's four giant planets for the first time.
It was the opportunity of a lifetime, but he wasn't sure he wanted the gig.
“I hesitated because I was still a fairly young professor at the time. I still had a lot of research I wanted to do,” he recalled 40 years later.
He took it anyway, and from the mission's first encounter with Jupiter in 1979 to its final flyby of Neptune in 1989, Stone became the scientific face of the Voyager mission. He led the scientific agenda and helped the public make sense of revolutionary images and data not only of Jupiter, Saturn, Uranus and Neptune, but also of many of their fascinating moons.
Stone and his more than 200 scientific collaborators were the first to discover lightning on Jupiter and volcanoes on its moon Io. They saw six never-before-seen moons around Saturn and found evidence of the largest ocean in the solar system on Jupiter's moon Europa, as well as geysers on Neptune's moon Triton.
“It seemed like everywhere we looked we were surprised to see those planets and their moons,” Stone told the Los Angeles Times in 2011. by. I can close my eyes and still remember every part of it.
The Voyager 1 spacecraft became the first man-made object to reach interstellar space in 2012, and Voyager 2 followed in 2018.
Stone, pictured with a model of the Voyager spacecraft, said the discovery of volcanoes on Io was a highlight of the mission.
(NASA)
The twin probes continue to send weekly communications from interstellar space to Earth. Stone retired in 2022, to mark the mission's 50th anniversary.
“Part of Ed lives on in the two Voyager spacecraft. The fingerprints of his dedication and keen leadership are woven into the Voyager mission,” said Linda Spilker, who joined the mission in 1977 and succeeded him as project scientist.
The Voyager mission was Stone's crowning achievement, but certainly not his only one.
He was a principal investigator on nine NASA missions and a co-investigator on five others, including several satellites designed to study cosmic rays, the solar wind and Earth's magnetic field.
He became director of the Jet propulsion laboratory in La Cañada Flintridge in 1991, a role he held for ten years.
It was an era of cost cutting at NASA, but Stone still managed to launch Galileo's five-year mission to Jupiter and send the Cassini spacecraft to Saturn. He was also at the helm of the agency when Mars Pathfinder delivered the Sojourner rover to the Red Planet. It was the first time humans placed a robot on the surface of another planet.
During his tenure at JPL, Stone continued to work and teach at Caltech, even teaching freshman physics during some of Voyager's long cruise times between planets.
He also served as chairman of the board of directors of the California Assn. for Research in Astronomy, which is responsible for its construction and operation WM Keck Observatory and its two 10-meter telescopes on Mauna Kea, Hawaii.
Edward Carroll Stone Jr. was born in Iowa on January 23, 1936 and grew up in Burlington, where his father ran a small construction company and his mother kept the business books.
Stone, the eldest of two brothers, was drawn to science from an early age. Under his father's watchful eye, he learned to take apart and reassemble all types of technology, from radios to cars.
“I was always interested in learning why something is that way and not that way,” Stone says said an interviewer in 2018. “I wanted to understand, measure and observe.”
After studying physics at Burlington Junior College, he received his master's and doctorate degrees from the University of Chicago. Shortly after he began his studies, news broke in 1957 that the former Soviet Union had launched Sputnik, the world's first artificial satellite.
“Just like that, the Cold War and our need to rival Sputnik absolutely opened up a whole new realm,” he said.
Stone has built a device to measure the intensity of solar energetic particles above the atmosphere that took a ride into space in 1961 aboard an Air Force satellite. Unfortunately, the spacecraft's transmitter was not working, so only a very limited amount of data was sent back to Earth. However, it was still enough to indicate that the intensity of the particles was lower than expected.
Despite the channel outage, Stone said the project was exciting. “We are taking the first steps into a whole new area of research and exploration,” he said. “We were right in the beginning.”
He joined the faculty at Caltech in 1964 and created more space experiments, this time for NASA.
Stone's special area of interest was cosmic rays — fast atomic nuclei that can come from explosive events on the sun or from violent events outside the solar system.
One of his cosmic ray experiments was part of the eleven major Voyager experiments.
Ed Stone in 2011, about a year before Voyager 1 entered interstellar space.
(Al Seib / Los Angeles Times)
Colleagues praised Stone for his leadership of the Voyager science team.
“He was a great hero, a giant among men,” Porco said, adding that Stone was known to treat everyone — from top scientists to graduate students — with respect.
Voyager team scientist Thomas Donahue put it this way, “Ed Stone has proven remarkably adept at keeping a bunch of prima donnas on track over the years.”
Stone was elected to the National Academy of Sciences in 1984 and received the National Medal of Science from President George HW Bush in 1991 in recognition of his leadership of the Voyager mission. He won the Shaw Prize for Astronomy in 2019, an honor that comes with a $1.2 million reward. In 2012, his hometown called Burlington, Iowa, the new one secondary school after him.
“This is truly an honor because it comes from the community where my journey of discovery began,” said Stone told a local newspaper.
Decades after Voyager's launch, he was asked to select his favorite moment of the mission. He chose the discovery of volcanoes Jupiter's moon Io.
“To find a moon that is volcanically 100 times more active than the entire Earth is really quite striking,” he said. “And this was typical of what Voyager would do on the rest of its journey through the outer solar system.
“Time and time again, we discovered that nature was much more inventive than our models,” he said.
His wife Alice, whom he met on a blind date at the University of Chicago and married in 1962, died in December. The couple is survived by their two daughters, Susan and Janet Stone, and two grandsons.
