NASA's Juno spacecraft has finished its most recent flyby of Jupiter's volcanic moon, Io. The spacecraft made two close approaches in the past month, obtaining images of the moon's extreme geological activity from just 1,500 kilometers away.

Io is one of Jupiter's "Galilean satellites" and was first discovered by astronomer Galileo Galilei himself back in 1610. At 3,642 kilometers in diameter, Io is the fourth largest moon of Jupiter. Its surface features towering mountains, expansive plains, and volcanic calderas.

But what really sets Io apart is that it hosts the most vigorously erupting volcanoes in the entire solar system. The volcanism is driven by intense tidal forces from the gravitational pull of Jupiter and neighboring moons. This generates substantial internal heating that frequently bursts out onto Io's surface.

"By observing Io over time, scientists can track the variability of volcanoes, the frequency of their eruption, brightness, and even whether they are isolated or grouped," said Scott Bolton, Juno's principal investigator at the Southwest Research Institute.

The recent Juno photos showcase volcanic plumes erupting from the surface. Over the past month, the spacecraft made two flybys to determine whether Io has a global subsurface magma ocean that feeds its prodigious lava flows.

Juno has been orbiting Jupiter since July 2016 to study the giant planet's atmosphere, magnetosphere, and interior structure. But the hardy spacecraft has also examined some of Jupiter's moons during its long mission.

"The goal is to determine whether there is an ocean of global magma beneath the surface of Io, feeding lava lakes and volcanic eruptions," said an expert familiar with the mission.

The new Io flybys provided closeup views of erupting volcanoes at a resolution impossible to match from Earth. After over seven years in operation, the successful Juno mission only has a few months left before its scheduled conclusion in September 2025. But in that time, we can expect new bursts of unforgettable images from deep in our solar system.