Ed Stone, the scientist who guided NASA’s groundbreaking Voyager mission to the outer planets for 50 years and who led the Jet Propulsion Laboratory in landing its first rover on Mars, died Tuesday. He was 88 years old.
A physicist who moved into space exploration, Stone played a leading role in NASA’s missions to Mars, Jupiter, Saturn, Uranus and Neptune. The discoveries made under his leadership revolutionized scientists’ understanding of the solar system and fueled humanity’s ambition to explore distant worlds.
Carolyn Porco, who worked on imaging on JPL’s Voyager and Cassini missions, called Stone “a thoroughly charming man” who was “as close to perfect as a project scientist could ever be “.
“When two science teams were fighting over a space resource and Ed had to choose between the two, even the guy who lost would walk away thinking, ‘Well, if that’s what Ed decided, then this must be the right answer,’” Porco said via email Tuesday. “I feel lucky to have known Ed. And like many people today, I am very sad to hear of his departure. »
Stone was a 36-year-old physics professor at Caltech in 1972 when he was asked to become chief scientist for a bold project to send two 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 job.
“I hesitated because I was a fairly young teacher at the time. I still had a lot of research to do,” he recalled 40 years later.
He took it anyway, and from the mission’s first encounter with Jupiter in 1979 until its final flyby of Neptune in 1989, Stone became the scientific face of the Voyager mission. He guided the scientific agenda and helped the public make sense of groundbreaking images and data not only from Jupiter, Saturn, Uranus and Neptune, but also from 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 spotted six previously unseen moons around Saturn and found evidence of the solar system’s largest ocean on Jupiter’s moon Europa, as well as geysers on Neptune’s moon Triton.
“It seemed that everywhere we looked, when we encountered these planets and their moons, we were surprised,” Stone told the Los Angeles Times in 2011. “We were discovering things we had never imagined, gaining a deeper understanding. clear view of the environment in which the Earth was a part. of. I can close my eyes and remember every moment. »
The Voyager 1 spacecraft became the first artificial object to reach interstellar space in 2012, and Voyager 2 followed suit in 2018.
Stone, pictured with a model of the Voyager spacecraft, said discovering the volcanoes on Io was one of the highlights of the mission.
(NASA)
The twin probes continue to send weekly communications to Earth from interstellar space. Stone retired in 2022 on the mission’s 50th anniversary.
“A part of Ed lives in the two Voyager spaceships. The fingerprints of his dedication and enthusiastic leadership are permeated throughout 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 not his only one.
He was principal investigator on nine NASA missions and 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 at La Cañada Flintridge in 1991, a position he held for a decade.
It was a time 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 the head of the agency when Mars Pathfinder delivered the Sojourner rover to the Red Planet. It was the first time humans placed a robotic rover on the surface of another planet.
Throughout his tenure at JPL, Stone continued to work and teach at Caltech, even teaching physics to freshmen during some of Voyager’s long cruises between planets.
He also served as chairman of the board of directors of the California Assn. for Astronomy Research, responsible for the construction and operation of the 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 company’s books.
The eldest of two brothers, Stone was drawn to science from an early age. Under the watchful eye of his father, he learned to take apart and reassemble all kinds of technology, from radios to cars.
“I always wanted to know why something happens this way and not that way,” Stone told 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 graduate school, news broke in 1957 that the former Soviet Union had launched Sputnik, the world’s first artificial satellite.
“Just like that, because of the Cold War and our need to match Sputnik, a whole new realm opened up,” he said.
Stone built a device to measure the intensity of energetic solar particles above the atmosphere that hitched a ride into space aboard an Air Force satellite in 1961. Unfortunately, the transmitter of the spacecraft did not work, so only a very limited amount of data was sent back to Earth. . However, this was still enough to indicate that the particle intensity was lower than expected.
Despite the transmitter problem, Stone said the project is exciting. “We were taking the first steps into a whole new area of research and exploration,” he said. “We were right in the beginning.”
He joined the Caltech faculty in 1964 and created more space experiments, this time for NASA.
Stone’s particular area of interest was cosmic rays – high-speed atomic nuclei that can come from explosive events on the sun or violent events beyond the solar system.
One of his cosmic ray experiments was among Voyager’s 11 major experiments.
Ed Stone in 2011, about a year before Voyager 1 entered interstellar space.
(Al Seib/Los Angeles Times)
His 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 for treating everyone – from the greatest scientists to graduate students – with respect.
Voyager team scientist Thomas Donahue put it this way: “Over the years, Ed Stone has proven himself remarkably adept at keeping a group of prima donnas on track. »
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 came with a $1.2 million prize. In 2012, his hometown of Burlington, Iowa named its new middle school after him.
“It’s truly an honor because it comes from the community where my journey of exploration began,” Stone said. said 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 on Jupiter’s moon Io.
“Finding a moon that is 100 times more volcanically active than the entire Earth is really quite striking,” he said. “And it was typical of what Voyager was going to do during the rest of its journey through the outer solar system.
“Time and time again, we found that nature was far 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, deceased in December. The couple is survived by their two daughters, Susan and Janet Stone, and two grandsons.