NASA’s Juno spacecraft will fly by Jupiter’s volcanic moon Io on Tuesday, May 16, and then the gas giant itself shortly thereafter. The flyby of the Jovian moon will be the closest yet, at an altitude of about 22,060 miles (35,500 kilometers). Now in the third year of its extended mission to explore Jupiter’s interior, the solar-powered probe will also explore the ring system, home to some of the gas giant’s inner moons.
To date, Juno has made 50 flybys of Jupiter and has also collected data during close encounters with three of the four Galilean moons – the icy worlds Europa and Ganymede and the fiery Io.
“Io is the most volcanic celestial body known in our solar system,” said Scott Bolton, Juno’s principal investigator at the Southwest Research Institute in San Antonio. “By observing over time on multiple flybys, we can see how volcanoes vary how often they erupt, how bright and hot they are, whether they are associated with a group or solo, and whether the shape of the lava flow changes. “
Slightly larger than Earth’s moon, Io is a world in constant torment. Not only the largest planet in the solar system is eternally pulling on it gravitationally, but also its Galilean siblings – Europa and the largest moon in the solar system, Ganymede. As a result, Io is constantly being stretched and compressed, actions associated with the formation of lava that can be seen erupting from many volcanoes.
While Juno was designed to study Jupiter, its numerous sensors also provided a wealth of data about the planet’s moons. Along with its JunoCam visible-light imager, the JIRAM (Jovian InfraRed Auroral Mapper), SRU (Stellar Reference Unit) and MWR (Microwave Radiometer) probes will study Io’s volcanoes and how volcanic eruptions interact with Jupiter’s powerful magnetosphere and auroras.
We are entering another amazing part of the Juno mission as we gradually approach Io. This 51st orbit will give us the closest look yet at this tortured moon,” Bolton said. “Our upcoming flybys in July and October will bring us even closer, leading up to our double flyby of Io in December this year and February next year, when we will fly within 1,500 kilometers of its surface. All of these flybys provide spectacular views of the volcanic activity of this amazing moon. The data should be amazing.”
“Half a century” on Jupiter
During its flybys of Jupiter, Juno approached low above the planet’s cloud tops — to within about 2,100 miles (3,400 kilometers). During these flybys, the probe approaches the planet via the north pole and exits via the south, using its instruments to probe beneath obscuring clouds, studying Jupiter’s interior and auroras to learn more about the planet’s origins, structure, atmosphere and magnetosphere.
Juno has been orbiting Jupiter for more than 2,505 Earth days and has flown over 510 million miles (820 million kilometers). The spacecraft arrived at Jupiter on July 4, 2016. The first science flyby occurred 53 days later, and the probe continued with this orbital period until the Ganymede flyby on June 7, 2021, reducing its orbital period to 43 days. A flyby of Europa on September 29, 2022 reduced the orbital period to 38 days. After two more flybys of Io, on May 16 and July 31, Juno’s orbital period will remain fixed at 32 days.
“Io is just one of the celestial bodies that continues to come under Juno’s microscope during this extended mission,” said Juno Acting Project Manager Matthew Johnson of NASA’s Jet Propulsion Laboratory in Southern California. “In addition to constantly changing our orbit to allow new perspectives of Jupiter and flying low over the night side of the planet, the probe will also thread a needle through some of Jupiter’s rings to learn more about their origin and composition.”