UNITED STATES: NASA’s Juno spacecraft is gearing up for an exciting encounter as it approaches Jupiter’s volcanic moon, Io, on Tuesday, May 16. This flyby will mark the closest encounter with Io to date, with Juno passing at an altitude of approximately 22,060 miles (35,500 kilometres). As Juno enters the third year of its extended mission to explore Jupiter’s interior, it will also venture into the ring system where several of the gas giant’s inner moons reside.
With 50 previous flybys of Jupiter under its belt, Juno has already collected valuable data during close encounters with three of Jupiter’s four Galilean moons: Europa, Ganymede, and now fiery Io. Io is known as the most volcanic celestial body in our solar system, making it an intriguing target for scientific study. By observing Io over multiple passes, scientists hope to gain insights into the behaviour of its volcanoes, including eruption frequency, brightness, temperature, and the evolving shape of its lava flows.
Scott Bolton, the Juno principal investigator from the Southwest Research Institute in San Antonio, emphasizes the significance of studying Io over time: “We may observe it over time on several passes to see how the volcanoes evolve, including how frequently they erupt, how bright and hot they are, whether or not they are connected to a group or erupt on their own, and whether or not the shape of the lava flow changes.”
Io, slightly larger than Earth’s moon, experiences constant gravitational pulls from both Jupiter and its neighbouring moons, Europa and Ganymede. These gravitational forces subject Io to continuous stretching and squeezing, contributing to the frequent volcanic eruptions observed on its surface.
While Juno’s primary mission focuses on studying Jupiter, its advanced sensors, including JunoCam, JIRAM (Jovian InfraRed Auroral Mapper), SRU (Stellar Reference Unit), and MWR (Microwave Radiometer), have provided a wealth of data on Jupiter’s moons. During this flyby, these instruments will specifically investigate Io’s volcanoes to understand how volcanic activity interacts with Jupiter’s powerful magnetosphere and auroras.
Scott Bolton further reveals Juno’s future plans for Io: “Before our twin flyby rendezvous with Io in December this year and February next year, when we fly within 1,500 km of the surface, we will be even closer thanks to our future flybys in July and October. Each of these flybys offers awe-inspiring images of this incredible moon’s volcanic activity. It should be incredible data.”
Juno has spent over 2,505 Earth days orbiting Jupiter and has travelled more than 510 million miles (820 million kilometres). Since its arrival at Jupiter on July 4, 2016, the spacecraft has continuously expanded our understanding of the gas giant. Juno’s recent flyby of Ganymede on June 7, 2021, reduced its orbital period to 43 days. Subsequent flybys of Europa and Io will further refine the spacecraft’s orbit, eventually settling at a fixed 32-day orbital period.
Matthew Johnson, Juno’s acting project manager at NASA’s Jet Propulsion Laboratory, highlights the mission’s broader scope: “Io is only one of the celestial bodies that Juno is continuing to study throughout this long journey. In addition to continuously altering its orbit to provide new views of Jupiter and flying close to the planet’s nightside, the spacecraft will thread a needle between some of Jupiter’s rings to gain further insight into their formation and makeup.”
NASA’s Jet Propulsion Laboratory in Pasadena, California, manages the Juno mission on behalf of the principal investigator, Scott J. Bolton, from the Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, overseen by the agency’s Science Mission Directorate in Washington and managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama. The spacecraft was constructed and is operated by Lockheed Martin Space in Denver.
As Juno inches closer to Io, scientists eagerly await the treasure trove of data that will shed light on the mysteries of this volcanic moon and deepen our understanding of Jupiter’s complex system.