Edward C. Stone, the visionary physicist who sent NASA’s Voyager spacecraft to run rings around our solar system’s outer planets and, for the first time, venture beyond to uncover interstellar mysteries, died Sunday at home his in Pasadena, California. 88.
His death was confirmed by his daughter Susan C. Stone.
Inspired by the launch of the Soviet Sputnik satellite in 1957, while a college student, Dr. Stone went on to oversee the Voyager missions 20 years later for the Jet Propulsion Laboratory, which the California Institute of Technology manages for NASA.
The twin spacecraft Voyager 1 and Voyager 2 were launched separately in the summer of 1977 from Cape Canaveral, Fla. Almost five decades later, they are continuing their journeys deep into space and still collecting data.
Dr. Stone was the program’s chief project scientist for 50 years, beginning in 1972, when he was a 36-year-old physics professor at Caltech. He became the public face of the project with the double launch in 1977.
Taking advantage of a gravitational convergence of the four planets that occurs only once every 176 years, the spacecraft zoomed past Jupiter, Saturn, Uranus and Neptune.
The spacecraft produced the first high-resolution images of the four planets, the rings of Jupiter, Uranus and Neptune, lightning on Jupiter, and lava lakes that revealed active volcanoes on Jupiter’s moon Io.
“We were on a mission of discovery,” said Dr. Stone told the New York Times in 2002. “But we didn’t appreciate how many revelations there would be.”
In 2012, Voyager 1 became the first man-made object to cross the heliopause boundary, where the strong solar wind of subatomic particles is subjected to the force of other suns. Today, Voyager 1 is estimated to be 15 billion miles from Earth and traveling at a speed of 38,000 mph, according to NASA. Voyager 2 crossed the border into interstellar space in 2018.
“The two spacecraft will be Earth’s ambassadors to the stars, circling the Milky Way for billions of years,” Dr. Stone.
His leadership of the Voyager project earned him the National Medal of Science in 1991 from President George HW Bush.
As director of the Jet Propulsion Laboratory in Pasadena from 1991 to 2001, Dr. Stone oversaw the Mars Pathfinder mission and its wheeled Sojourner rover; the orbiting mission of the Galileo space probe to Jupiter; the launch of the Cassini spacecraft to Saturn and its rings and moons, a joint project involving NASA, the European Space Agency and the Italian space agency; and a new class of Earth science satellites.
Dr. Stone also served, from the late 1980s to the 1990s, as chairman of the California Association for Astronomical Research, which built and operated the WM Keck Observatory in Hawaii.
In 2014, he became the founding executive director of the Thirty Meter International Telescope Observatory, also in Hawaii. He held that position until 2022, when he retired as Voyager’s chief scientist.
In a statement, Thomas F. Rosenbaum, president of Caltech, called Dr. Stone “a great scientist, a formidable leader and a gifted exhibitor of discoveries.”
Edward Carroll Stone Jr. was born on January 23, 1936, in Knoxville, Iowa, southeast of Des Moines, and grew up near Burlington, on the banks of the Mississippi River. His father, Edward Sr., owned a small construction company and his mother, Ferne Elizabeth (Baber) Stone, kept her books.
“Our father was a construction supervisor who loved to learn new things and explain how they worked,” wrote Dr. Stone when he was awarded the 2019 Shaw Prize in Astronomy for his work on the Voyager missions.
He received a bachelor of arts degree in physics from Burlington Junior College (now Southeastern Community College) and earned a master’s degree and a doctorate from the University of Chicago.
Dr. Stone married Alice Trabue Wickliffe in 1962. She died in 2023. Besides his daughter Susan, he is survived by another daughter, Janet Stone; and two grandchildren.
Shortly after he began graduate studies, news that the Soviets had launched a satellite focused his fascination with physics on the exploration of space and, in particular, cosmic rays, particles that come from stars and travel through the universe at warp speed.
Inspired by doctoral advisor John A. Simpson, Dr. Stone conducted his first cosmic ray experiments in 1961 while working on Discover 36, an Air Force spy satellite.
He joined the Caltech faculty in 1964. As chairman of the university’s Division of Physics, Mathematics, and Astronomy, a role he held from 1983 to 1988, he helped establish the Laser Interferometer Gravitational-Wave Observatory, the who later discovered ripples in space and time called gravitational waves.
Norman Haynes, who for years was Voyager’s general project manager, once said that Dr. Stone, because of his scientific expertise and management skills, “revolutionized the world of project science”.
In 1990, Dr. Stone acknowledged the irony in his signature project—that even with all his breakthroughs, he wouldn’t see its completion before he died.
“I’ve had so much fun on Voyager,” he told The New York Times Magazine, “that even if I never see the edge of the solar system, I’d do it all over again.”
Dr. Stone eventually witnessed the twin starships leave the solar system—twice.
“I keep wondering why there is so much public interest in space,” he said. “At the end of the day, it’s just basic science. The answer is that it provides us with a sense of the future. When we stop discovering new things there, the concept of the future will change. Space reminds us that there is something left to do, that life will continue to evolve. Give us direction, an arrow in time.”