On Saturday, NASA’s Juno orbiter got a second close-up with Io, Jupiter’s third-largest moon and the most volcanic world of our solar system.
The Juno spacecraft, which arrived at the gas giant in 2016, is on an extended mission to explore Jupiter’s rings and moons. Its latest flyby, which complemented the mission’s first close approach on Dec. 30, yielded even more views of the moon’s hellish landscape.
Io’s violent expulsions of sulfur and additional compounds give the moon its orange, yellow and blue hues. The process is similar to what happens around the volcanoes of Hawaii or the geysers in Yellowstone National Park, according to Scott Bolton, a physicist at the Southwest Research Institute who leads the Juno mission. “That must be what Io is like — on steroids,” he said. He added that it probably smells like those places, too.
Released on Sunday, the most recent shots of Juno are already ripe for discovery. Dr. Bolton saw on the surface of Io what appears to be a double volcanic plume spewing into space — something that Juno has never caught before. Other scientists are noticing new lava flows and changes to familiar features spotted in past space missions like the Galileo probe, which made numerous close flybys of Io in the 1990s and 2000s.
“That’s the beauty of Io,” said Jani Radebaugh, a planetary scientist at Brigham Young University who is not part of the Juno mission, but collaborates with the team on Io observations. Unlike our own moon, which remains frozen in time, Dr. Radebaugh said, “Io changes every day, every minute, every second.”
Images from the twin flybys, during which the spacecraft came within about 930 miles of Io, will be combined with previous snapshots NASA had captured of the Jovian moon. The goal, Dr. Bolton said, is to understand “what’s really behind the engine that’s driving all the volcanoes, because they’re all over the place.”
That might be a global magma ocean just beneath Io’s crust — or merely pockets of molten rock under the surface, like the ones that fuel Earth’s volcanoes. It could be weeks, even months, before scientists begin to find answers in the data.
This is the last close flyby that Juno will make of Io. But the mission will continue to conduct more distant observations every 60 days, giving mission specialists a picture of the ever-changing moon as a whole.
That data will be just as valuable, according to Dr. Bolton.
“All of the images are amazing,” he said. “We never really know what to expect.”
