Thanks to NASA\u2019s Juno mission to the Jupiter system, we\u2019re getting our best looks ever at the gas giant\u2019s volcanic moon Io. Even as Juno provides our best views of the moon, it also deepens our existing questions. Only a dedicated mission to Io can answer those questions, and there are two proposed missions.<\/p>\n
<\/p>\n Io is well-known as the most geologically active world in the Solar System, and it\u2019s not even close. It has over 400 active volcanoes. Io is the closest moon to Jupiter, and the planet\u2019s powerful gravity is largely responsible for Io\u2019s volcanoes. As the planet pulls on Io, the friction creates tidal heating in the moon\u2019s interior. This creates magma and drives its volcanic eruptions. Sulphur compounds in the eruptions paint the moon\u2019s surface in shades of red, yellow, white, black, and green. <\/p>\n There\u2019s never been a dedicated mission to Io, only missions that captured images as they passed by, including Galileo, Voyager 1, Cassini, New Horizons, and Juno, NASA\u2019s current mission to Jupiter. But Io is intriguing and unique, and it can teach us a lot.<\/p>\n Planetary scientists want to know more about the moon\u2019s geological processes. Io is considered a high heat flux world, and scientists want to learn more about its tidal dissipation. Studying Io can also tell us more about primitive planetary bodies that were once more volcanic, which Earth likely was early in its history. <\/p>\n Io can also tell us more about volcanogenic atmospheres, which can play a vital role in shaping a planet\u2019s environment. This 2020 paper draws a link between Earth\u2019s volcanic activity and the Great Oxygenation Event, a critical period when oxygen accumulated in Earth\u2019s atmosphere. A better understanding of the link between volcanic activity and atmospheric evolution will help us better understand exoplanets and habitability.<\/p>\n Scientists know that the Galilean moons exchange material with Jupiter\u2019s atmosphere and magnetosphere. They also know that material ejected from Io\u2019s volcanoes can reach the surfaces of the other moons. Some of it can be turned into plasma by Jupiter\u2019s powerful magnetosphere, forming Io\u2019s plasma torus. They\u2019re curious about this mass exchange in the Jupiter system and how it\u2019s shaped the moons. <\/p>\n These are the reasons for a dedicated mission to Io.<\/p>\n In 2010, scientists at the University of Arizona and Johns Hopkins University\u2019s Applied Physics Laboratory first proposed the Io Volcano Observer (IVO) as part of NASA\u2019s Discovery Program. IVO was proposed as a low-cost mission to explore Jupiter\u2019s volcanic Moon. It was proposed again in 2015 and in 2019. In 2020, IVO was selected with two other missions for further study but ultimately lost out to the DAVINCI+ and VERITAS missions to Venus. <\/p>\n Now, there\u2019s another proposal for the Io Volcano Observer, but this time, it\u2019s under NASA\u2019s New Frontiers Program. The new proposal shows that the desire for an Io-focused mission won\u2019t go away. Instead, it\u2019s gaining steam.<\/p>\n In a new paper still subject to peer review, a group of mostly American scientists present their case for the New Frontiers IVO. It\u2019s titled \u201cComparing NASA Discovery and New Frontiers Class Mission Concepts for the Io Volcano Observer (IVO).\u201d The first author is Christopher Hamilton from the Lunar and Planetary Laboratory, University of Arizona.<\/p>\n The IVO NF would address our scientific questions by reaching three goals, according to the authors:<\/p>\n The original IVO proposal had the spacecraft encounter Io ten times in four years after reaching the moon in 2033. It would\u2019ve carried five instruments, with a sixth under consideration. The IVO would\u2019ve crossed Io from pole to pole, passing over the equator at an altitude of between 200 and 500 kilometres (124 and 310 miles.) <\/p>\n The closest approaches were carefully designed to give the spacecraft the best observations of the moon\u2019s magnetic field, gravity field, and libration amplitude. The approaches also would\u2019ve allowed for both sunlit and dark views of volcanoes, allowing the spacecraft to study the composition of lava. The polar perspective would\u2019ve provided new views of heat emanating from the moon that were unavailable to Galileo and unobservable from Earth. <\/p>\n The new IVO NF proposal maintains the polar orbit of the original IVO but improves it in several ways. Universe Today talked with lead author Christopher Hamilton about the new proposal. His remarks have been lightly edited for clarity.<\/p>\n The first change in the new proposal concerns the number of flybys, which would increase from 10 to 20. <\/p>\n \u201cBoth\u00a0IVO<\/em>\u00a0and\u00a0IVO-NF<\/em>\u00a0are great missions, but doubling the number of flybys more than doubles the scienctific return from an Io mission!\u201d<\/p>\n Christopher Hamilton, Lunar and Planetary Laboratory, University of Arizona.<\/cite><\/p><\/blockquote>\n<\/figure>\n \u201c10 flybys for the original Discovery-level IVO mission would fill important gaps in image coverage that remain unfilled after the Voyager and Galileo era,\u201d Hamilton said. So why double it?<\/p>\n \u201cThe new tour not only doubles the image coverage of Io\u2019s surface with high-resolution imaging but also enables more flybys of active volcanoes, like Loki, Loki Patera, and Pillian Patera,\u201d Hamilton said. \u201cThese are highly dynamic volcanic systems that include active lava lakes and explosive eruptions\u2014one pass over the volcanic systems is simply not enough to constrain their time-variability and eruption dynamics.\u201d<\/p>\n Like Earth\u2019s Moon, Io is tidally locked to Jupiter, with one side more readily available for study than the Jupiter-facing side. But Jupiter\u2019s effect on Io is much stronger than Earth\u2019s effect on the Moon. \u201cHowever, tidal interactions between Jupiter and Io are much stronger, exciting tides in solid rock with an amplitude of about 100 m (328 feet), which is taller than the Statue of Liberty!\u201d Hamilton said. These tidal interactions drive Io\u2019s powerful volcanism. \u201cHowever, studies of the past decade have suggested that this heat has also melted a layer within Io to form a subsurface \u2018\u201d\u2018magma ocean,’\u201d Hamilton said.<\/p>\n The original IVO\u2019s ten orbits, with its magnetometer instrument, would have confirmed or excluded this hypothesis. The new proposal will carry an improved version of this instrument, and with more orbits, it could answer questions about Io\u2019s magma ocean. <\/p>\n \u201cIVO-NF would also carry a fluxgate magnetometer and with the repeat passes, carefully timed to measure Io\u2019s induced magnetic field at different times in its orbit, would greatly reduce the uncertainty in estimating a potential magma oceans depth,\u201d Hamilton said. The current uncertainty is \u00b110 km, but IVO NF would reduce it to \u00b13 km. This \u201cwould revolutionize our understanding of Io\u2019s interior and the links between tidal heating and volcanism,\u201d Hamilton told Universe Today.<\/p>\n \u201cBoth IVO and IVO-NF are great missions, but doubling the number of flybys more than doubles the scienctific return from an Io mission!\u201d Hamilton said. <\/p>\n IVO-NF would also approach Io much closer than the original IVO. The original mission called for an altitude of 200 and 500 kilometres (124 and 310 miles) above Io\u2019s surface. IVO-NF would begin its mission with high-altitude fly-bys, but as the mission progressed and objectives were reached, it would come much closer. <\/p>\n \u201cWith 20 flybys, IVO-NF can be more daring, flying closer to Io\u2019s surface and even flying through its volcanic plumes to determine the chemistry of its erupted products in unprecedented detail,\u201d Hamilton told Universe Today.<\/p>\n Initial flybys would be at about 200 km, \u201cbut as the mission progresses and Baseline objectives are achieved, we will be able to lower the altitude of later flybys over active volcanoes like Pele Patera,\u201d Hamilton said. <\/p>\n \u201cNonetheless, we would image and analyze these volcanoes first, making use of repeat coverage to further constrain the safety of the close approach, and take precautions like reorienting the spacecraft\u2019s solar panels so that they fly through the plume side-on rather than exposing the full cross-sectional area,\u201d Hamilton told Universe Today. \u201cPlume flythroughs for Io would also open the door to other sampling opportunities for plumes on Saturn\u2019s active moon, Enceladus.\u201d<\/p>\n \u201cThis may seem dangerous, but even at altitudes of 50 km, there would be very few particles,\u201d Hamilton said. But before the spacecraft comes that close, it\u2019ll use its Surface Dust Analyzer to understand the hazard. This instrument was added to the IVO-NF as a top priority. It will measure surface dust composition and the composition of nanograins in the volcanic plumes. Overall, it will give scientists a better understanding of Io\u2019s dust environment and inform them if it\u2019s safe to approach within 50 km. <\/p>\n According to Hamilton, we\u2019re experiencing a renaissance in exploring the Jovian system. <\/p>\n \u201cThis is an important time in Planetary Exploration, and exploration of the Jupiter System is undergoing a renaissance, with\u00a0Juno,\u00a0Europa Clipper, and\u00a0JUICE examining Jupiter, Europa, and Ganymede at the same time,\u201d Hamilton told Universe Today. Io is a critical part of Jupiter\u2019s moon system. It\u2019s at the heart of the orbital resonance configuration between Io, Europa, and Ganymede, and the resonance drives geological activity on all three moons, including volcanism, tectonic activity, and the formation of surface features. <\/p>\n \u201cJuno has filled some important gaps left after the end of the Galileo mission (1995\u20132003), but IVO and IVO-NF would be the first to have an instrument suite that is optimized specifically for Io,\u201d said Hamilton. <\/p>\n To the intellectually curious, everything in nature is worthy of study and deeper understanding. An extraordinary world like Io is certainly no exception, with everything it has to tell us about itself, its sibling moons, and even about the early Earth and Moon.<\/p>\n \u201cOur paper makes the case that Io is a priority target for exploration that should be considered in the next New Frontier Announcement of Opportunity,\u201d Hamilton told Universe Today. He acknowledges that the original IVO mission at the Discovery level is possible, but the IVO New Frontiers mission would accomplish a lot more and would more thoroughly address our outstanding questions about Io. <\/p>\n \u201cA larger mission to Io via New Frontiers would more than double the scientific return of the mission and would offer the best approach to understanding not just Io, but the Jupiter System as a whole, and the origins of high-heat flux worlds like the early Earth, early Moon, and other terrestrial planets in the Solar System and beyond,\u201d Hamilton concluded. <\/p>\n\n
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