During its flyby, Voyager 1 sent back imagery of Jupiter that surpassed anything astronomers had seen before, revealing the Great Red Spot's complex storm structure and, days later, the first evidence of active volcanoes on the moon Io. The data fundamentally reshaped scientific understanding of the outer solar system's largest planet and its moons.
On March 5, 1979, Voyager 1 swept past Jupiter, and the imagery streaming back to Earth showed a planet far more dynamic than anyone expected. Scientists saw the Great Red Spot, a storm observed for centuries, in unprecedented detail, and that the moon Io hosted active volcanoes spewing sulfur across its surface, the first confirmed volcanic activity found anywhere beyond Earth.
The spacecraft also revealed a faint ring system around Jupiter, previously unknown, and captured intricate cloud bands shifting and churning with a violence that dwarfed any storm on Earth. Each new image forced planetary scientists to revise their models of gas giant atmospheres.
Voyager 1's Jupiter data set the stage for its sister craft Voyager 2's own flyby later that year, and for both spacecraft's eventual encounters with Saturn. Decades later, Voyager 1 would go on to become the first human-made object to leave the solar system entirely, but its 1979 portraits of Jupiter remain some of the mission's most scientifically consequential achievements.