Magnificent new views of volcanic moon Io and Jupiter by the Juno probe

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The Juno space probe has been exploring the Jovian system, comprising Jupiter and its rings and moons, for more than six years. Currently and for several more years, it will be the only probe capable of making flybys of the most active body in the solar system. On May 16, it made the closest flyby to date of the moon Io, capturing images that reveal a changing surface unlike any other similar object.

Three photographs of Io taken by the JunoCam instrument on the Juno space probe. Credits: NASA / SwRI / MSSS / Jason Perry

A volcanic world

Io is the closest of the so-called Galilean moons, those discovered by Galileo Galilei. Because of its small separation from Jupiter, it undergoes a phenomenon known as tidal coupling, i.e., it is always offering the same face towards the planet.

In turn, Jupiter's immense gravity exerts powerful tidal forces on the moon. This causes great internal heating, which explains the great volcanic activity on Io. Since the planet is literally melting it from within and squeezing out this magma.

Jupiter magnetosphere schematic
Diagram showing the magnetic field lines of Jupiter. A special connection between the planet and Ion descends on the environment, thanks to which material from volcanoes flows to Jupiter's poles and forms powerful auroras.

The exploration of Io is quite difficult, since it is submerged between the bands of radiation caused by Jupiter's powerful magnetic field. This poses a huge threat to the electrical circuits of ships that dare to approach such distances.. For this reason, the future Europa Clipper and JUICE will focus on the other three Galilean moons.

New images of Ío

In the so-called perijove or closest approach to Jupiter number 51, Juno made a flyby of Io of 35,500 kilometers (22,000 miles).. Using the JunoCam instrument, a camera focused on science outreach, several images of the moon and the planet were captured.


Credits: NASA / SwRI / MSSS / Jason Perry

Comparison of the surface of Io at two different times. On the left is the most recent photograph. Due to high volcanic activity, Io has processes of surface change at a rate unparalleled in the solar system.. In the northwestern zone, new flows of large proportions stand out.

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Along with the new photos of Io, NASA offered this composite of two images taken on December 14, 2022 (left) and March 1, 2023 (right). Where the overlapping red and white areas show the areas of highest volcanic activity.

Credits: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill

Io has large mountains, which are even visible from a great distance. Several of them reach 5 to 10 kilometers in height.. A slight elevation on the circumference of the moon is visible to the left.

In addition, a bright white spot stands out in the terminator area, i.e., the line that separates day and night. This may be mistakenly labeled as a volcanic ejection, but it is actually the tip of a mountain near Gauwa Patera illuminated by the Sun.

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Credits: NASA / SwRI / MSSS

Composition of three filters of the JunoCAm camera when it was at 102186.9 kilometers above Jupiter.. The image shows only the illuminated part of the planet and focuses on the northern hemisphere.

Weaving knowledge

This and future flybys will offer contributions to our understanding of the processes through which Io passes and how it interacts with Jupiter. In the middle of the year, even closer approaches to this peculiar world will be made by the only probe that will offer us this quality of images in at least two decades.

Francisco Andrés Forero Daza