Edward C. Stone, the visionary physicist who orbited NASA's Voyager spacecraft around the outer planets of our solar system and first went beyond to unlock interstellar mysteries beyond our own solar system, died Sunday at his home in Pasadena, California. He was 88.
His death was confirmed by his daughter, Susan C. Stone.
As a college student, Dr. Stone was inspired by the launch of the Soviet artificial satellite Sputnik in 1957, and 20 years later he oversaw the Voyager program at the Jet Propulsion Laboratory, managed for NASA by the California Institute of Technology.
The twin probes, Voyager 1 and Voyager 2, launched separately from Cape Canaveral, Florida, in the summer of 1977. Nearly 50 years later, they continue to travel deep into space and collect data.
Dr. Stone served as the program's chief project scientist for 50 years, beginning in 1972 when he was a professor of physics at Caltech at age 36. He became the public face of the project during the 1977 double launch.
Taking advantage of the gravitational convergence of the four planets, which occurs only once every 176 years, the spacecraft passed Jupiter, Saturn, Uranus and Neptune.
The spacecraft took the first high-resolution images of four planets, Jupiter, Uranus, the rings of Neptune, Jupiter's lightning, and lava lakes revealing active volcanoes on Jupiter's moon Io.
“We were on a mission of discovery,” Dr. Stone told The New York Times in 2002. “But we didn't realize how much there would be to discover.”
In 2012, Voyager 1 became the first man-made object to cross the heliopause, where the intense solar wind of subatomic particles succumbs to the force of the other sun. According to NASA, Voyager 1 is currently estimated to be 15 billion miles from Earth and traveling at 38,000 miles per hour. Voyager 2 crossed the boundary of interstellar space in 2018.
“These two ships will orbit the Milky Way for billions of years and will be Earth's ambassadors to the stars,” Dr Stone once said.
For his leadership of the Voyager missions, he received the National Medal of Science from President George H. W. Bush in 1991.
Dr. Stone served as director of the Jet Propulsion Laboratory in Pasadena from 1991 to 2001, overseeing the Mars Pathfinder mission and its wheeled Sojourner rover, the Galileo space probe's mission to orbit Jupiter, and the launch of the Cassini spacecraft to Saturn and its rings and moons, a joint project of NASA, the European Space Agency and the Italian Space Agency, as well as a new class of Earth science satellites.
Dr. Stone also served as president of the California Astronomical Research Association, which helped build and operate the W. M. Keck Observatory in Hawaii in the late 1980s and 1990s.
In 2014, he became the first executive director of the Thirty Meter International Telescope Observatory in Hawaii, a role he will hold until his retirement as Voyager's chief scientist in 2022.
Caltech President Thomas F. Rosenbaum, in a statement, called Dr. Stone “a great scientist, a brilliant leader and a 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 Mississippi River. His father, Edward Sr., owned a small construction company, and his mother, Fern Elizabeth (Baber) Stone, was the company's bookkeeper.
“Our father was a construction foreman who loved learning new things and explaining how they worked,” Dr Stone wrote when he received the 2019 Shaw Prize in Astronomy for his work on the Voyager missions.
He earned an associate's degree in physics from Burlington Junior College (now Southeastern Community College) and a master's and doctorate from the University of Chicago.
Dr. Stone married Alice Trabue Wickliffe in 1962. She passed away in 2023. In addition to his daughter Susan, he is survived by another daughter, Janet Stone, and two grandchildren.
Shortly after beginning his graduate studies, he heard news that the Soviet Union had launched a satellite and sparked his interest in space exploration, particularly the physics of cosmic rays, particles that emanate from stars and travel through space at warp speed.
Inspired by his doctoral supervisor, John A. Simpson, Dr. Stone conducted his first cosmic ray experiments in 1961 while developing the Air Force spy satellite Discover 36.
He joined the faculty at Caltech in 1964. From 1983 to 1988, he served as chair of the physics, mathematics, and astronomy departments at the university, and helped found the Laser Interferometer Gravitational-Wave Observatory, which later detected ripples in space-time called gravitational waves.
Norman Haynes, Voyager's long-time overall project manager, 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: despite all his discoveries, he would not see its conclusion until his death.
“I had a great time on Voyager,” he told The New York Times Magazine, “and I'd love to do it again, even if we never saw the edge of the solar system.”
Dr. Stone ended up witnessing the twin ships leave the solar system twice.
“I always ask myself why people are so interested in space,” he said. “After all, it's just fundamental science. The answer is that space gives us a sense of the future. When we stop discovering new things in space, our concept of the future changes. Space reminds us that there is still work to be done, that life continues to evolve. Space gives us direction, it gives us the arrow of time.”