A violent eruption observed on Io, the most volcanic body in the Solar System

Last fall, a major volcanic eruption took place on Io, the closest Galilean satellite to Jupiter.

Jeff Morgenthalerscientist at Planetary Science Institute (PSI), used the observatory Io Input/Output (IoIO), located near Benson, Arizona (USA), to monitor thevolcanic activity on Io since 2017. Observations show some activity almost every year, but the fall 2022 one is the strongest seen so far.

A coronagraph to see the gases of Io

Of Jupiter’s four largest satellites, Io is closest to the planet. The tidal effect of the orange giant and two other Galilean satellites, namely Europa and Ganymede, makes Io the most volcanic body in the Solar System. Indeed, when Ganymede travels one orbit, Europa travels two and Io travels four. This so-called Laplace resonance keeps Io’s orbital eccentricity slightly above zero (0.0041) and thus produces the main source of heat for its volcanic activity.

IoIO uses a coronagraphic technique to attenuate the light coming from Jupiter, in order to image the faint gas glow near the planet. Between July and September 2022, two of these gases became brighter: sodium and ionized sulfur. This event lasted until December. The ionized sulphur, which forms a donut-like structure around Jupiter called the plasma torus of Io, was surprisingly less bright during this eruption than in previous ones observed. For Morgenthaler, it could tell us something about the composition of the volcanic activity that produced the eruption or it could tell us that the torus is more efficient at shedding its material when more material is injected into it “.

Useful data for Juno’s flyby of Io

These observations have profound implications for the Juno mission. The probe, which has been orbiting Jupiter since 2016, flew past Europe on September 29, 2022, during the eruption, and it is provided that it passes about 1,500 kilometers from the surface of Io on December 30, 2023, just before its 57e perizene (passage of the probe as close as possible to Jupiter). Several Juno instruments are sensitive to changes in the plasma environment around Jupiter and Io that can be directly attributed to the type of volcanic activity observed by IoIO. Morgenthaler explains that ” the measurements of Juno could tell us if this volcanic eruption had a different composition from previous ones “.

Morgenthaler mentions that “ one of the exciting things about these observations is that they can be replicated by almost any small institute or ambitious amateur astronomer. Almost all of the parts used to build IoIO are available at a high-end camera store or telescope store “. Having one or more copies of IoIO running elsewhere would be very helpful in avoiding weather outages and could provide greater temporal coverage of Io’s highly dynamic Plasma Torus and Sodium Nebula each night. ” It would be great to see another IoIO go live before Juno hits Jupiter next December. concludes Morgenthaler.

Besides the Jovian Sodium Nebula, IoIO observes the sodium tail of Mercurybright comets and transiting extrasolar planets.

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