NASA’s Juno spacecraft is embarking on an exciting mission as it approaches Jupiter’s volcanic moon, Io, on Tuesday, May 16. This upcoming flyby will mark the closest encounter with Io to date, as Juno will soar at an altitude of approximately 22,060 miles (35,500 kilometers). Following this remarkable event, Juno will proceed to explore the gas giant itself. Currently in its third year of the extended mission, Juno aims to investigate Jupiter’s interior. Additionally, the spacecraft will delve into the ring system housing some of the gas giant’s inner moons.
Juno has already accomplished an impressive feat of performing 50 flybys of Jupiter while collecting valuable data during close encounters with three out of the four Galilean moons. These include the icy worlds Europa and Ganymede, as well as the fiery Io.
Scott Bolton, the Juno principal investigator from the Southwest Research Institute in San Antonio, explains that Io stands as the most volcanically active celestial body in our solar system. By observing Io during multiple passes, scientists can monitor the varying behavior of its volcanoes. This includes tracking the frequency of eruptions, the intensity and temperature of volcanic activity, whether the eruptions occur individually or in clusters, and any changes in the lava flow patterns.
With its primary mission focused on Jupiter, Juno’s extensive array of sensors has offered valuable insights into the planet’s moons as well. Alongside the JunoCam visible light imager, the spacecraft’s JIRAM (Jovian InfraRed Auroral Mapper), SRU (Stellar Reference Unit), and MWR (Microwave Radiometer) instruments will be dedicated to studying Io’s volcanoes. These investigations aim to unravel the intricate interplay between volcanic eruptions and Jupiter’s powerful magnetosphere and captivating auroras.
Io, slightly larger than Earth’s moon, endures a perpetual state of turmoil due to the relentless gravitational tugs from not only Jupiter, the largest planet in our solar system, but also its neighboring Galilean siblings, Europa and Ganymede. These gravitational interactions subject Io to continuous stretching and squeezing, processes closely associated with the eruption of lava from its numerous volcanoes.
“We are embarking on an incredible phase of Juno’s mission as we approach Io with each successive orbit. This 51st orbit is set to provide us with our closest and most detailed view yet of this fascinatingly tortured moon,” Bolton expressed. He further added, “Our upcoming flybys in July and October will bring us even closer, building up to our remarkable twin flyby encounters with Io in December of this year and February of next year. During those encounters, we will come within a mere 1,500 kilometers of its surface. These flybys are granting us breathtaking perspectives of Io’s volcanic activity, and the anticipated data is sure to be extraordinary.”
A ‘half-century’ at Jupiter
During its flybys of Jupiter, Juno has ventured remarkably close to the planet’s cloud tops, reaching distances as near as approximately 2,100 miles (3,400 kilometers). Approaching Jupiter from its northern pole and departing from its southern regions during these flybys, Juno strategically employs its instruments to delve beneath the veiling cloud cover, diligently scrutinizing Jupiter’s interior, auroras, structure, atmosphere, and magnetosphere. These investigations aim to unravel the planet’s origins and provide a deeper understanding of its intricate dynamics.
Juno has been faithfully orbiting Jupiter for over 2,505 Earth days, traversing a staggering distance of 510 million miles (820 million kilometers) since its arrival on July 4, 2016. The initial scientific flyby occurred a mere 53 days later, and the spacecraft continued with that orbital period until it encountered Ganymede on June 7, 2021, which subsequently reduced its orbital period to 43 days. The subsequent flyby of Europa on September 29, 2022, further reduced the orbital period to 38 days. Following the upcoming flybys of Io on May 16 and July 31, Juno’s orbital period will stabilize at 32 days.
Matthew Johnson, the acting project manager of Juno from NASA’s Jet Propulsion Laboratory in Southern California, highlighted that Io is merely one of the celestial bodies continually under the scrutiny of Juno during its extended mission. In addition to dynamically adjusting its orbit to enable novel perspectives of Jupiter and flying at low altitudes over the planet’s nightside, the spacecraft will skillfully navigate through the intricate spaces between some of Jupiter’s rings. These ventures aim to unlock insights into the origin and composition of these enigmatic rings, enriching our knowledge of Jupiter’s captivating system.