Voyager 1’s Jupiter Flyby Rewrote the Book on the Solar System’s Giant

On Wednesday, Nov. 18, NASA’s Voyager 1 spacecraft will reach a new distance milestone: 16.09 billion miles (25.89 billion kilometers) from Earth. That separation is so immense that light takes 24 hours to travel between the probe and our planet.

Although the achievement will be marked on Earth, Voyager 1 will experience its “light-day” in darkness. Mission scientists switched off the spacecraft’s camera in 1990, shortly after it captured the iconic “Pale Blue Dot” and “Solar System Family Portrait” images beyond Neptune’s orbit. Even so, Voyager 1 had already returned tens of thousands of images of our cosmic neighborhood, and some of them fundamentally changed how scientists understood the outer planets.

One of the most important parts of that legacy is Voyager 1’s encounter with Jupiter. From January to April 1979, the probe studied the solar system’s largest planet and several of its giant moons at close range, reaching a minimum distance of 174,000 miles (280,000 kilometers) in March 1979, according to NASA. As it approached, Voyager photographed the gas giant every 96 seconds, producing a remarkable time-lapse record of Jupiter’s turbulent atmosphere.

The observations revealed distinct bands in Jupiter’s atmosphere rotating at different speeds and in different directions, like a cosmic Rubik’s Cube being twisted by an unseen hand. Clouds raced past like conveyor belts while enormous, planet-sized storms swirled through the Jovian atmosphere.

Voyager’s time-lapse film covers about 60 full days on Jupiter — roughly one month on Earth, since a Jupiter day lasts about 10 Earth hours. It provided the most comprehensive, high-resolution view of the planet up to that point and built substantially on data from NASA’s Pioneer 10 and 11 Jupiter probes, which had launched half a decade earlier. The results showed that Jupiter’s atmosphere was far more dynamic than astronomers had realized.

Just before its closest approach, Voyager spotted something extraordinary: Jupiter has a thin, faint ring system. Made primarily of dust, the rings became visible only when Voyager viewed Jupiter backlit by the Sun. No telescope had ever seen them before, but ground-based observatories soon confirmed their existence, and Voyager 2 captured even clearer images of the rings when it reached Jupiter in July 1979.

Scientists now know that all four outer planets — Jupiter, Saturn, Uranus and Neptune — have rings. Today, researchers suspect that Jupiter’s dusty rings are partly replenished by volcanic eruptions on the planet’s volatile moon Io.

That discovery is also tied to Voyager. During a close approach to Io, the spacecraft witnessed the first volcanic eruption ever observed on a world beyond Earth. The observation demonstrated that moons, not only planets, can be geologically active. In this image, a giant volcano called Loki Patera — the largest volcano on Io, estimated at about 125 miles (200 kilometers) wide — sends material into space.

Taken together, these observations showed that Jupiter and its moons form a far more dynamic, complicated and chaotic system than anyone had recognized. The close-up views also turned distant worlds from points of light into fully realized places — worlds to explore, map and eventually visit. This week, China’s space agency announced its intention to send a lander to Jupiter’s moon Callisto in the first-ever landing mission to the Jovian system.

Voyager 1’s work continues in interstellar space, which it officially reached in 2012. With its camera off, the probe studies the radiation environment of space using magnetic field and plasma detectors — the last two of its 10 science instruments still receiving power. Scientists expect the legendary spacecraft to run out of power in the 2030s.

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