An article published in the journal “Geophysical Research Letters” reports the most accurate map created so far of the volcanoes of Io, one of the planet Jupiter’s Galilean moons. A team of researchers led by Francesca Zambon of the Italian National Institute of Astrophysics used data collected by the Juno space probe’s JIRAM instrument in a NASA mission that also sees the collaboration of the Italian Space Agency regarding JIRAM. The surveys made it possible to identify 242 volcanic hot spots, 23 of which had not been previously detected. The new hot spots were identified mainly in the polar regions, an achievement possible thanks to Juno’s orbit.
Io is the most geologically active body in the solar system. This activity takes the form of volcanic eruptions and is caused by gravitational forces acting on Io from Jupiter but also from the other Galilean moons. The Juno space probe, which entered Jupiter’s orbit on July 4, 2016, is conducting close-up surveys that mainly concern the biggest planet in the solar system but its course is programmed so that it can fly by some of its moons.
The image (Courtesy F. Zambon et al. / Geophysical Research Letters. All rights reserved) shows a set of what are called super images that show Io’s volcanic hot spots at different times when this moon was subject to observations. The super images are generated by averaging multiple contiguous observations by the JIRAM (Jovian InfraRed Auroral Mapper) instrument. This is a technique used to reduce the risk of false positives.
Other NASA space probes offered images of volcanoes on Io in previous decades: Voyager 1 in 1979 and the Galileo mission between 1995 and 2003. They made it possible to understand that there were a few hundred volcanoes on Io and that many of them had practically constant activity.
The data collected by the Juno space probe’s JIRAM instrument made it possible to add new volcanic hot spots to the already existing catalog but don’t include all the known ones. Of the already known hot spots, JIRAM detected 82% of the strongest ones and about half of those of intermediate strength and the weakest ones. According to Francesca Zambon, this could mean that JIRAM’s resolution isn’t sufficient to detect weak hot spots, or that their activity dropped or stopped.
The Juno space probe’s mission is scheduled to continue until September 2025 and during that time, more observations of Io will be conducted. In particular, the closest Io flyby is scheduled for December 30, 2023, with a minimum distance of about 4,800 kilometers. New detections will help create a more detailed and up-to-date map of Io’s volcanoes to better understand its geological processes and internal structure.
