When NASA's Juno orbiter swooped close to a Jupiter moon, it saw a pair of volcanic plumes spurting material into space, something the robotic spacecraft hadn't captured before. 

The plumes rise high above Io, Jupiter's third-largest moon. It's the most volcanically active world in our solar system, where astronomers believe hundreds of volcanoes spew fountains that reach dozens of miles high. The spacecraft took the snapshot in February, its final closeup tour of Ioat a range of 2,400 miles away. 

This last hurrah didn't disappoint. Scientists are just beginning to pore over the close encounter's data, revealing new information about the moon's volcanic processes, said Scott Bolton, Juno's principal investigator at the Southwest Research Institute in a statement.

Andrea Luck, based in Scotland, processed the raw data to enhance its clarity (shown above). The plumes, visible along Io's limb, are either blasting out of two vents from one enormous volcano or two separate-but-snug volcanoes. 

Junohas been orbiting Jupiterfor more than seven years. During its primary mission, the spacecraft collected data on the gas giant's atmosphere and interior. Among its discoveries was a finding that the planet's atmospheric weather layer extends way beyond its clouds. 

After completing 35 orbits, the spacecraft transitioned to studying the entire system around Jupiter, including its dust rings and many moons. This extended mission will continue for another year or until the spacecraft dies. Juno will eventually burn up in Jupiter's atmosphere as its trajectory around the planet erodes. Relax, though: NASA says the orbiter is not at risk of crashing into and contaminating Jupiter's moons, some of which may be habitable worlds. 

The spacecraft has an instrument, dubbed JunoCam, designed to take closeup photos of Jupiter and engage the public. The science team invites amateur astronomers to process the camera's raw data and crowdsources what to focus on next. 

JunoCam isn't the only instrument giving scientists fresh insights into Io's volcanoes. The Jovian Infrared Auroral Mapper, or JIRAM, has also been observing the moon in infrared light. Researchers just published a new paperbased on the Italian instrument's findings in the journal Nature Communications Earth and Environment.

Galileo Galilei discovered Ioin 1610, but it took many centuries before NASA's Voyager 1spacecraft first spotted a volcanic eruption on it. With the help of Juno, scientists are beginning to understand the mechanisms driving that activity. 

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The whole surface of Io, about the size of Earth's moon, is covered in molten silicate lava lakes. These lakes are contained in caldera-like features — large basins formed when volcanoes erupt and collapse, said Alessandro Mura, the paper's lead author, in a statement.

The researchers think the moon teems with vast lakes of lava, wherein magma rises and recedes. The lava crust breaks against the lake's steep walls, forming a ring similar to what happens in Hawaiian lava lakes. The tall barriers may be what's preventing the magma from spilling all over Io's surface.

But there's another idea that can't be ruled out: Magma could be welling up in the middle of the lake, spreading out, then forming a crust that sinks along the lake's rim, exposing lava.