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Edward Stone: 50 Years at NASA ends, but his brainchild Voyager’s Project goes on

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Stone’s remarkable tenure on NASA’s longest-operating mission spans decades of historic discoveries and firsts.

Edward Stone has retired as the project scientist for NASA’s Voyager mission a half-century after taking on the role. Stone accepted scientific leadership of the historic mission in 1972, five years before the launch of its two spacecraft, Voyager 1 and Voyager 2. Under his guidance, the Voyagers explored the four giant planets and became the first human-made objects to reach interstellar space, the region between the stars containing material generated by the death of nearby stars.

Until now, Stone was the only person to have served as project scientist for Voyager, maintaining his position even while serving as director of NASA’s Jet Propulsion Laboratory in Southern California from 1991 to 2001. JPL manages the Voyager mission for NASA. Stone retired from JPL in 2001 but continued to serve as the mission’s project scientist.

“It has been an honor and a joy to serve as the Voyager project scientist for 50 years,” Stone said. “The spacecraft have succeeded beyond expectation, and I have cherished the opportunity to work with so many talented and dedicated people on this mission. It has been a remarkable journey, and I’m thankful to everyone around the world who has followed Voyager and joined us on this adventure.”

Edward Stone

Edward Stone, second from left, and other members of the Voyager team pose with a model of the spacecraft in 1977, the year the twin probes launched. Credit: NASA/JPL-Caltech

Linda Spilker will succeed Stone as Voyager’s project scientist as the twin probes continue to explore interstellar space. Spilker was a member of the Voyager science team during the mission’s flybys of Jupiter, Saturn, Uranus, and Neptune. She later became project scientist for NASA’s now-retired Cassini mission to Saturn, and rejoined Voyager as deputy project scientist in 2021.

Jamie Rankin, a research scientist at Princeton University and a member of the Voyager science steering group, has been appointed deputy project scientist for the mission. Rankin received her Ph.D. in 2018 from Caltech, where Stone served as her advisor. Her research combines data from Voyager and other missions in NASA’s heliophysics fleet.

The twin Voyager spacecraft launched in 1977, on a mission to explore Jupiter and Saturn, ultimately revealing never-before-seen features of those planets and their moons. Voyager 1 continued its journey out of the solar system, while Voyager 2 continued on to Uranus and Neptune – and remains the only spacecraft to have visited the ice giants.

Edward Stone

Edward Stone, left, talks to reporters at a news conference to announce findings from Voyager 2’s flyby of Uranus in 1986. Credit: NASA/JPL-Caltech

Following this “grand tour” of the outer planets, the Voyager Interstellar Mission began. The goal was to exit the heliosphere – a protective bubble created by the Sun’s magnetic field and outward flow of solar wind (charged particles from the Sun). Voyager 1 crossed the boundary of the heliosphere and entered interstellar space in 2012, followed by Voyager 2 (traveling slower and in a different direction) in 2018. Today, as part of NASA’s longest-running mission, both spacecraft continue to illuminate the interplay between our Sun, and the particles and magnetic fields in interstellar space.

“Ed likes to say that Voyager is a mission of discovery, and it certainly is,” said Suzanne Dodd, Voyager project manager. “From the flybys of the outer planets in the 1970s and ’80s, to the heliopause crossing and current travels through interstellar space, Voyager never ceases to surprise and amaze us. All those milestones and successes are due to Ed’s exceptional scientific leadership and his keen ability to share his excitement about these discoveries to the world.”

Among the many honors bestowed on him, Stone has been a member of the National Academy of Sciences since 1984. He was awarded the National Medal of Science from President George H.W. Bush in 1991. When Stone was interviewed on the late-night TV show “The Colbert Report” in 2013, NASA arranged for host Stephen Colbert to present him with the NASA Distinguished Public Service Medal, the agency’s highest honor for a nongovernment individual. In 2019, he received the Shaw Prize in Astronomy from the Shaw Foundation in Hong Kong for his work on the Voyager mission.

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Webb space Telescope Captures Clearest View of Neptune’s Rings, Unusual Moon ‘Triton’

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NASA’s James Webb Space Telescope shows off its capabilities closer to home with its first image of Neptune. Not only has Webb captured the clearest view of this distant planet’s rings in more than 30 years, but its cameras reveal the ice giant in a whole new light.

Most striking in Webb’s new image is the crisp view of the planet’s rings – some of which have not been detected since NASA’s Voyager 2 became the first spacecraft to observe Neptune during its flyby in 1989. In addition to several bright, narrow rings, the Webb image clearly shows Neptune’s fainter dust bands.

“It has been three decades since we last saw these faint, dusty rings, and this is the first time we’ve seen them in the infrared,” notes Heidi Hammel, a Neptune system expert and interdisciplinary scientist for Webb. Webb’s extremely stable and precise image quality permits these very faint rings to be detected so close to Neptune.

Neptune has fascinated researchers since its discovery in 1846. Located 30 times farther from the Sun than Earth, Neptune orbits in the remote, dark region of the outer solar system. At that extreme distance, the Sun is so small and faint that high noon on Neptune is similar to a dim twilight on Earth.

Webb’s Near-Infrared Camera (NIRCam) images objects in the near-infrared range from 0.6 to 5 microns, so Neptune does not appear blue to Webb. In fact, the methane gas so strongly absorbs red and infrared light that the planet is quite dark at these near-infrared wavelengths, except where high-altitude clouds are present. Such methane-ice clouds are prominent as bright streaks and spots, which reflect sunlight before it is absorbed by methane gas.
Credits: NASA, ESA, CSA, STScI

This planet is characterized as an ice giant due to the chemical make-up of its interior. Compared to the gas giants, Jupiter and Saturn, Neptune is much richer in elements heavier than hydrogen and helium. This is readily apparent in Neptune’s signature blue appearance in Hubble Space Telescope images at visible wavelengths, caused by small amounts of gaseous methane.

Webb’s Near-Infrared Camera (NIRCam) images objects in the near-infrared range from 0.6 to 5 microns, so Neptune does not appear blue to Webb. In fact, the methane gas so strongly absorbs red and infrared light that the planet is quite dark at these near-infrared wavelengths, except where high-altitude clouds are present. Such methane-ice clouds are prominent as bright streaks and spots, which reflect sunlight before it is absorbed by methane gas. Images from other observatories, including the Hubble Space Telescope and the W.M. Keck Observatory, have recorded these rapidly evolving cloud features over the years.

More subtly, a thin line of brightness circling the planet’s equator could be a visual signature of global atmospheric circulation that powers Neptune’s winds and storms. The atmosphere descends and warms at the equator, and thus glows at infrared wavelengths more than the surrounding, cooler gases.

Neptune’s 164-year orbit means its northern pole, at the top of this image, is just out of view for astronomers, but the Webb images hint at an intriguing brightness in that area. A previously-known vortex at the southern pole is evident in Webb’s view, but for the first time Webb has revealed a continuous band of high-latitude clouds surrounding it.

What do we see in Webb’s latest image of the ice giant Neptune? Webb captured seven of Neptune’s 14 known moons: Galatea, Naiad, Thalassa, Despina, Proteus, Larissa, and Triton. Neptune’s large and unusual moon, Triton, dominates this Webb portrait of Neptune as a very bright point of light sporting the signature diffraction spikes seen in many of Webb’s images.
Credits: NASA, ESA, CSA, STScI

Webb also captured seven of Neptune’s 14 known moons. Dominating this Webb portrait of Neptune is a very bright point of light sporting the signature diffraction spikes seen in many of Webb’s images, but this is not a star. Rather, this is Neptune’s large and unusual moon, Triton.

Covered in a frozen sheen of condensed nitrogen, Triton reflects an average of 70 percent of the sunlight that hits it. It far outshines Neptune in this image because the planet’s atmosphere is darkened by methane absorption at these near-infrared wavelengths. Triton orbits Neptune in an unusual backward (retrograde) orbit, leading astronomers to speculate that this moon was originally a Kuiper belt object that was gravitationally captured by Neptune. Additional Webb studies of both Triton and Neptune are planned in the coming year.