Ed Stone, the scientist who oversaw the Jet Propulsion Laboratory’s first rover landing on Mars and headed NASA’s historic Voyager mission to the outer planets for 50 years, passed away on Tuesday. He was eighty-eight.
Being a physicist, Stone was involved in NASA missions to Mars, Jupiter, Saturn, Uranus, and Neptune from the very beginning. His oversight oversaw findings that transformed science’s knowledge of the solar system and stoked people’s desire to visit far-off planets.
As “as close to perfect as a project scientist could ever be,” Stone was described as “a thoroughly lovely man” by Carolyn Porco, who worked on imaging for JPL’s Voyager and Cassini missions.
“When two science teams were in contention over some spacecraft resource, and Ed had to decide between the two, even the guy who lost went away thinking, ‘Well, if this is what Ed has decided, then it must be the right answer,'” Porco said by email Tuesday. “I feel blessed to have known Ed. And like many people today, I’m very sad to know he’s gone.”
In 1972, Stone, a 36-year-old professor of physics at Caltech, was asked to take on the role of principal scientist for a bold plan to launch two spacecraft to investigate the solar system’s four big planets for the first time.
Even though it was a once-in-a-lifetime opportunity, he wasn’t sure he wanted the job.
“I hesitated because I was a fairly young professor at that point. I still had a lot of research I wanted to do,” he recalled 40 years later.
Nevertheless, Stone accepted it, and from the mission’s initial encounter with Jupiter in 1979 to its last flyby of Neptune in 1989, Stone served as the project’s scientific spokesperson. In addition to directing the scientific agenda, he assisted the general public in understanding cutting-edge photos and information from several of Jupiter, Saturn, Uranus, and Neptune’s intriguing moons.
Lightning on Jupiter and volcanoes on its moon Io were originally discovered by Stone and his more than 200 scientific collaborators. They discovered evidence of the largest ocean in the solar system on Jupiter’s moon Europa and geysers on Neptune’s moon Triton, in addition to spotting six previously undiscovered moons surrounding Saturn.
“It seemed like everywhere we looked, as we encountered those planets and their moons, we were surprised,” Stone told the Los Angeles Times in 2011. “We were finding things we never imagined, gaining a clearer understanding of the environment Earth was part of. I can close my eyes and still remember every part of it.”
In 2012, the Voyager 1 spacecraft became the first artificial object to enter interstellar space, and in 2018, Voyager 2 did the same.
Every week, the two probes continue to communicate with Earth from interstellar space. Marking the mission’s 50th anniversary, Stone retired in 2022.
“Ed’s legacy endures in the two Voyager spacecraft. His commitment to excellence and astute leadership are evident throughout the Voyager mission, according to Linda Spilker, who joined the mission in 1977 and took over as project scientist.
While the Voyager mission was Stone’s greatest accomplishment, it was by no means his only one.
He served as co-investigator on five NASA missions and primary investigator on nine of them, which included many satellites aimed at examining the Earth’s magnetic field, solar wind, and cosmic rays.
In 1991, he was appointed head of the Jet Propulsion Laboratory located in La Cañada Flintridge, a position he maintained for ten years.
Even though NASA was trying to save costs, Stone was still able to send the Cassini spacecraft to Saturn and begin Galileo’s five-year journey to Jupiter. Additionally, he led the organization when Mars Pathfinder sent the Sojourner rover to the Red Planet. It was the first time robotic rovers have been placed on the surface of another planet by humans.
Even during some of Voyager’s protracted planet-hopping cruises, Stone continued to work and teach at Caltech while he was employed at JPL. He even taught freshmen physics there.
The California Association for Research in Astronomy, which is in charge of constructing and managing the W.M. Keck Observatory and its two 10-meter telescopes on Mauna Kea, Hawaii, also had him as chairman of its board.
Edward Carroll Stone Jr. was raised in Burlington, Iowa, where his mother maintained the company’s finances and his father operated a small construction company. He was born in Iowa on January 23, 1936.
Stone, the older of two brothers, has always been drawn to science. He learnt how to disassemble and repair many kinds of equipment, including cars and radios, under his father’s careful supervision.
In an interview in 2018, Stone stated, “I was always interested in learning about why something is this way and not that way.” “My goals were to comprehend, quantify, and observe.”
He attended Burlington Junior College to study physics before attending the University of Chicago to earn his master’s and PhD. The world’s first artificial satellite, Sputnik, was launched by the former Soviet Union in 1957, not long after he started his PhD studies.
“Just like that, because of the Cold War and our need to match Sputnik, a whole new realm opened up,” he stated.
In 1961, Stone developed a tool to gauge the strength of solar energetic particles above the atmosphere, which was carried into space by an Air Force satellite. Sadly, the spacecraft’s transmitter malfunctioned, resulting in the return of relatively little data to Earth. It was still sufficient, though, to show that the particle intensity was lower than anticipated.
Stone said the endeavour was exciting despite the transmitter malfunction. He declared, “We were embarking on a completely new field of study and investigation.” “We were there from the start.”
In 1964, he became a faculty member at Caltech and continued to develop space experiments, this time for NASA.
Cosmic rays, which are fast-moving atomic nuclei that can come from powerful extrasolar events or solar explosions, were Stone’s special area of interest.
Among the eleven principal Voyager experiments was one of his cosmic-ray investigations.
Stone’s leadership of the Voyager science team was commended by colleagues.
“He was a great hero, a giant among men,” stated Porco, who also mentioned that Stone was well-known for treating everyone with respect, even graduate students and prominent scientists.
In the words of Thomas Donahue, a team scientist on Voyager, “Ed Stone has proven to be remarkably adept at keeping a bunch of prima donnas on track over the years.”
In 1984, Stone was elected to the National Academy of Sciences, and in 1991, President George H.W. Bush awarded him the National Medal of Science in appreciation of his leadership during the Voyager mission. He was the recipient of the $1.2-million Shaw Prize in Astronomy in 2019. 2012 saw the naming of Burlington, Iowa, his hometown, as the site of a new middle school.
Stone told a local newspaper, “This is truly an honour because it comes from the community where my exploration journey began.”
He was asked to choose his favourite mission moment from Voyager decades after the spacecraft’s launch. He went with the finding of volcanoes on Io, Jupiter’s moon.
“Finding a moon that’s 100 times more active volcanically than the entire Earth, it’s quite striking,” he said. “And this was typical of what Voyager was going to do on the rest of its journey through the outer solar system.
“Time after time, we found that nature was much more inventive than our models,” he said.
He married Alice in 1962 after they first met on a blind date at the University of Chicago. Alice passed away in December. Their two daughters, Susan and Janet Stone, as well as their two grandsons, survive the couple.
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