By March 1979, Voyager 1 was a day away from its closest approach to Jupiter. Readings from Pioneer 10 and 11 had hinted at solid matter near the planet's equator, so the Voyager imaging team argued for a single photograph aimed at the right spot. Mission managers had doubts, but they approved it. The exposure of 11 minutes and 12 seconds showed a faint band of light: a ring too thin and dim to have been seen from Earth. The find upended the idea that Saturn's grand rings were unique among the planets.
The photograph almost didn't happen. Members of the Voyager imaging team, among them Raymond Heacock, Edward Stone and Bradford Smith, noticed puzzling particle readings that Pioneer 10 and 11 had picked up near Jupiter's equator. They proposed searching for a ring. Team managers doubted anything was there and agreed to only one exposure. On March 4, 1979, Voyager 1 found the ring right where the team had predicted.
The image itself looks like a mistake. Because the spacecraft was moving during the exposure of more than 11 minutes, the background stars came out as jagged zigzags. Across them runs a thin, pale streak, the first photographic evidence of Jupiter's rings.
Once astronomers in Hawaii knew what to look for, they confirmed the ring from the ground with a telescope whose mirror measured just 2.2 meters across. It was a telling lesson: scientists had failed to see the ring partly because their theories said it shouldn't exist. Together with the discovery of rings around Uranus in 1977, Voyager's finding suggested that rings are common among the giant planets.
Key people: Edward C. Stone, Bradford A. Smith, Raymond L. Heacock