Edward C. Stone, the visionary physicist who sent NASA’s Voyager spacecraft to circle the rings around our solar system’s outer planets and for the first time ventured to uncover interstellar mysteries, died Sunday at his home 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 20 years later to oversee Voyager missions 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, Florida. Almost five decades later, they continue their journeys deep into space and are 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 professor of physics at Caltech. He became the public face of the double launch project in 1977.
Taking advantage of the gravitational convergence of four planets, which occurs only once every 176 years, the spacecraft flew past Jupiter, Saturn, Uranus and Neptune.
The probe produced the first high-resolution images of 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 The New York Times in 2002. “But we didn’t appreciate how many discoveries there would be.”
In 2012, Voyager 1 became the first man-made object to cross the heliopause boundary, where the violent solar wind of subatomic particles succumbs to the force of other suns. Today, Voyager 1 is estimated to be 15 billion miles from Earth and traveling at 38,000 mph, according to NASA. Voyager 2 crossed the line into interstellar space in 2018.
“These two spacecraft will be Earth’s ambassadors to the stars and will orbit 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 on the Mars Pathfinder mission and its wheeled rover Sojourner; the Galileo space probe’s orbital mission 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 Research in Astronomy, which built and operated the WM Keck Observatory in Hawaii.
In 2014, he became the founding executive director of the Thirty Meter Telescope International Observatory, also in Hawaii. He held this position until 2022, when he retired as Voyager’s chief scientist.
In a statement, Caltech President Thomas F. Rosenbaum identified Dr. Stone for “a brilliant scientist, formidable leader and gifted interpreter 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. he owned a small construction business and his mother, Ferne Elizabeth (Baber) Stone, kept its books.
“Our father was a construction superintendent who liked 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 earned an associate of arts degree in physics from Burlington Junior College (now Southeastern Community College) and earned a master’s degree and Ph.D. 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 school, news that the Soviets had launched a satellite focused his fascination with physics on space exploration and, in particular, cosmic rays, particles that come from stars and travel through space at warp speed.
Dr. Inspired by his doctoral advisor John A. Simpson, Stone conducted his first experiments with cosmic rays 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 Department of Physics, Mathematics, and Astronomy, a position he held from 1983 to 1988, he helped found the Gravitational-Wave Observatory laser interferometer, which later detected ripples in space and time called gravitational waves.
Norman Haynes, who was Voyager’s chief project manager for years, once said that Dr. Stone “revolutionized the world of project science” with his scientific expertise and management skills.
In 1990 Dr. Stone acknowledged the irony of his signature project—that for all his discoveries, he would not see its conclusion until he died.
“I had so much fun on Voyager,” he told The New York Times Magazine, “that even if I never saw the edge of the solar system, I would do it all over again.”
Dr. Stone ended up witnessing the twins’ departure from the solar system—twice.
“I keep asking myself why there is so much public interest in space,” he said. “It’s just basic science after all. The answer is that it gives us a sense of the future. When we stop discovering new things out there, the concept of the future changes. The universe reminds us that there is more to be done, that life will continue to evolve. It gives us direction, an arrow in time.”