On the 3rd, NASA’s Juno probe had a second close encounter with Io, Jupiter’s third largest moon and the most volcanic world in 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 pass, which complemented the mission’s first close approach on December 30, provided even more views of the moon’s hellscape.
Violent eruptions of sulfur and additional compounds from Io give the moon its orange, yellow, and blue hues. The process is similar to what happens around volcanoes in Hawaii or 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 the 4th, Juno’s latest images are ready for discovery. Bolton saw on the surface of Io what appears to be a double volcanic plume spewing into space — something Juno has never captured before. Other scientists are observing new lava flows and changes to familiar features seen on past space missions, such as the Galileo probe, which made several close approaches to 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 observations of Io. Unlike our own Moon, which remains frozen in time, Radebaugh said, “Io changes every day, every minute, every second.”
Images from the two close passes, during which the spacecraft came within about 1,500 km of Io, will be combined with previous snapshots taken by NASA of the Jovian moon. The goal, Bolton said, is to understand “what’s really behind the mechanism that drives all volcanoes, because they’re everywhere.”
This could be a global ocean of magma just beneath Io’s crust — or simply pockets of molten rock beneath the surface, like those that feed Earth’s volcanoes. It could take weeks, even months, before scientists start to find answers in the data.
This is the last close pass Juno will make of Io. But the mission will continue to perform more distant observations every 60 days, providing mission experts with an ever-changing picture of the moon as a whole.
This data will be equally valuable, according to Bolton.
“All the images are incredible,” he said. “We never really know what to expect.”