New images from NASA\u2019s Juno spacecraft make Io\u2019s nature clear. It\u2019s the most volcanically active world in the Solar System, with more than 400 active volcanoes. Juno has performed multiple flybys of Io, and images from its latest one show an enormous hotspot near the moon\u2019s south pole. <\/p>\n
<\/p>\n Juno was sent to Jupiter to study the giant planet, but that primary mission ended, and NASA extended the mission. Currently, it is performing flybys of three of the Galilean moons: Ganymede, Europa, and Io. We\u2019ve reported on Juno\u2019s Io flybys previously. <\/p>\n In its latest flyby, the orbiter imaged a volcanic hotspot on the moon\u2019s south pole larger than Lake Superior. The images are from Juno\u2019s JIRAM (Jovian Infrared Auroral Mapper) instrument. According to NASA, the hot spot\u2019s eruptions are six times more energetic than all of Earth\u2019s power plants and its radiance measured well above 80 trillion watts.<\/p>\n \u201cThe data supports that this is the most intense volcanic eruption ever recorded on Io.\u201d<\/p>\n Alessandro Mura, Juno co-investigator, National Institute for Astrophysics in Rome<\/cite><\/p><\/blockquote>\n<\/figure>\n \u201cJuno had two really close flybys of Io during Juno\u2019s extended mission,\u201d said the mission\u2019s principal investigator, Scott Bolton of the Southwest Research Institute in San Antonio. \u201cAnd while each flyby provided data on the tormented moon that exceeded our expectations, the data from this latest \u2014 and more distant \u2014 flyby really blew our minds. This is the most powerful volcanic event ever recorded on the most volcanic world in our solar system \u2014 so that\u2019s really saying something,\u201d Bolton said in a NASA press release. <\/p>\n Io is volcanic because of tidal heating. Io is the innermost of Jupiter\u2019s four Galilean moons and is roughly the same size as Earth\u2019s Moon. However, it\u2019s very close to the much larger Jupiter, follows an elliptical orbit, and completes one every 42.5 hours. Jupiter is roughly 300 times more massive than Earth. That means that Jupiter dwarfs Io, and as the moon orbits the gas giant, the gas giant has its way with it. Jupiter stretches and pulls on the little moon, causing it to flex and change shape, creating internal heat. The other Galilean moons also contribute. <\/p>\n The heat is enough to melt the moon\u2019s interior into molten rock. The tidal flexing creates an endless series of plumes and ash that make the moon the most volcanically active body in the Solar System. The ash also paints the small moon\u2019s surface. <\/p>\n During its extended mission, Juno flies past Io on every other orbit, meaning the images can track any changes on the surface. During a previous flyby on February 3rd, 2024, Juno came within 1,500 km (930 mi) of the moon\u2019s surface.<\/p>\n During this latest flyby, it was much further away. It only got to within about 74,400 kilometres (46,200 mi) of the moon, and its JIRAM instrument was pointed at the south pole.<\/p>\n \u201cJIRAM detected an event of extreme infrared radiance \u2014 a massive hot spot \u2014 in Io\u2019s southern hemisphere so strong that it saturated our detector,\u201d said Alessandro Mura, a Juno co-investigator from the National Institute for Astrophysics in Rome. \u201cHowever, we have evidence what we detected is actually a few closely spaced hot spots that emitted at the same time, suggestive of a subsurface vast magma chamber system. The data supports that this is the most intense volcanic eruption ever recorded on Io.\u201d<\/p>\n This feature, which has yet to be named, dwarfs Loki Patera, the lake of lava detected in 2015 during a rare orbital alignment between Io and Europa. Loki Patera is 202 kilometres (126 mi) in diameter, covers 20,000 sq km (7,700 sq mi), and was the largest volcanic feature found on Io until these new observations revealed the hot spot in the south polar region. The new hot spot covers 100,000 sq km (40,000 sq mi). <\/p>\n Juno also captured images of the hot spot region with its JunoCam imager. Though the images were captured from different distances and are somewhat grainy, they still reveal surface colour changes near the south pole. Scientists know that these colour changes are associated with hot spots and volcanic activity. <\/p>\n Juno will fly by Io again on March 3rd. It will examine the hotspot again and try to discern any more surface changes. Massive eruptions like this one leave their mark on the surface, and these marks can be long-lived. The eruptions can leave behind pyroclastic deposits, lava flows, and sulphur-rich deposits from plumes that colour the moon\u2019s surface. It\u2019s also possible that Earth-based observations can probe the same region. <\/p>\n Scientists have unanswered questions about Io\u2019s extreme volcanic activity. They know tidal heating is the root cause, but they don\u2019t have a clear understanding of how the heat moves through Io\u2019s interior. They also don\u2019t know if the moon has a global, subsurface lava ocean, though some studies suggest it does. They also wonder about the relationship between the volcanoes and Jupiter\u2019s magnetosphere, where much of the material from the volcanoes goes. The long-term evolution of Io\u2019s volcanic activity is also shrouded in mystery. How has it changed over time?<\/p>\n Answers to these questions will also tell scientists about volcanism on other worlds. <\/p>\n \u201cWhile it is always great to witness events that rewrite the record books, this new hot spot can potentially do much more,\u201d said Bolton. \u201cThe intriguing feature could improve our understanding of volcanism not only on Io but on other worlds as well.\u201d<\/p>\n\n
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