On the moon Io of Jupiter, a sizable volcanic eruption was found.

courtesy of Planetary Science Institute

Jovian sodium nebula in outburst as seen in an IoIO picture Jeff Morgenthaler, PSI, is indebted.

Using PSI's Io Input/Output observatory, Jeff Morgenthaler of the Planetary Science Institute observed a sizable volcanic eruption on Jupiter's moon Io (IoIO).

Since 2017, PSI Senior Scientist Morgenthaler has used IoIO, a satellite observatory in Benson, Arizona, to track Io's volcanic activity. Every year, according to the data, there is some form of eruption, although the biggest one thus yet was observed in the fall of 2022.

The tidal stresses that Io experiences from Jupiter and two of its other large satellites, Europa and Ganymede, make it the most volcanically active body in the Solar System. Io is the innermost of Jupiter's four large moons.

In order to image the weak gases close to the extremely brilliant planet, IoIO employs a coronagraphic approach that reduces the light coming from Jupiter. Between July and September 2022 and lasting until December 2022, two of these gases—sodium and ionised sulfur—started to brighten. Io plasma torus, a structure made of ionised sulphur that surrounds Jupiter and has previously been observed, but oddly not nearly as luminous in this outburst. This "may be telling us something about the nature of the volcanic activity that created the outburst or it might be telling us that the torus is more effective at removing material when more stuff is added," said Morgenthaler.

For NASA's Juno mission, which has been circling Jupiter since 2016, the observations have significant ramifications. During the outburst, Juno passed by Europa and is now slowly moving toward Io in preparation for a near encounter in December 2023. Several of Juno's instruments are capable of detecting changes in the plasma environment around Jupiter and Io that are closely related to the sort of volcanic activity seen by IoIO. If this volcanic eruption had a different composition from earlier ones, Juno measurements could be able to reveal that information, according to Morgenthaler.

Time history of the brightness of the Jovian sodium nebula at three different separations from Jupiter (top) and the Io plasma torus (bottom), revealing a number of small outbursts and one massive outburst in the fall of 2022. Jeff Morgenthaler, PSI, is indebted.

One of the fascinating aspects of these findings, according to Morgenthaler, is that practically any motivated amateur astronomer or student at a small institution may replicate them. "A high-end camera shop or telescope store has almost all of the parts needed to make IoIO."

The highly dynamic Io plasma torus and sodium nebula on Jupiter could potentially receive more time coverage each night if one or more copies of IoIO were running elsewhere. This would help avoid weather gaps. Another IoIO coming up before Juno visits Jupiter in December would be fantastic, added Morgenthaler.

The IoIO time sequence of singly ionised sulphur in the Io plasma torus demonstrates how the structure rotates in response to Jupiter's strong magnetic field, which, like Earth's, is not precisely aligned with the planet's axis of rotation. Jeff Morgenthaler, PSI, is indebted.

IoIO also monitors the sodium tail of Mercury, brilliant comets, and transiting extrasolar planets in addition to the Jovian sodium nebula.