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- Jupiter\u2019s moon Io is highly volcanically active<\/strong>, with around 400 volcanoes on its surface.<\/li>\n
- On its most recent flyby of Io, NASA\u2019s Juno spacecraft<\/strong> detected the most intense volcanic activity ever seen on the Jovian moon.<\/li>\n
- The eruption likely left long-term signatures on Io<\/strong>, which Juno will investigate during an upcoming flyby.<\/li>\n<\/ul>\n
NASA published this original article on January 28, 2025. Edits by EarthSky.<\/p>\n
Extreme volcanic activity on Io<\/h3>\n
During a flyby of Jupiter\u2019s moon Io on December 27, 2024, NASA\u2019s Juno spacecraft discovered an astonishing volcanic hotspot in the moon\u2019s southern hemisphere. The hotspot is not only larger than Earth\u2019s Lake Superior (the largest freshwater lake in the world by surface area), but it also belches out eruptions with six times the total energy of all the world\u2019s power plants. Even by Io\u2019s intense standards \u2013 as the most volcanic celestial body in the solar system \u2013 its recent activity has been extreme.<\/p>\n
Juno\u2019s principal investigator Scott Bolton of the Southwest Research Institute in San Antonio, Texas, said: <\/p>\n
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The data from this latest flyby really blew our minds. This is the most powerful volcanic event ever recorded on the most volcanic world in our solar system; so that\u2019s really saying something.<\/p>\n<\/blockquote>\n
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![\"Half](\"https:\/\/earthsky.org\/upl\/2024\/01\/Io-raw-image-from-Juno-Dec-30-2023-e1704037084880-1.jpeg\")
The Juno spacecraft acquired this closeup image of Io on December 30, 2023. It\u00a0was its 57th perijove, or close flyby to Jupiter, since entering orbit around the giant planet on\u00a0July 4, 2016.\u00a0Some of the pockmarks are active volcanos. Image via NASA.<\/figcaption><\/figure>\n Io: A tormented, volcanic world<\/h3>\n
The source of Io\u2019s torment is Jupiter. Io is about the size of Earth\u2019s moon, and orbits extremely close to the mammoth gas giant. And it whips around Jupiter once every 42.5 hours in an elliptical (oval-shaped) orbit. As the distance to Jupiter varies, so does the planet\u2019s gravitational pull, which leads to the moon being relentlessly squeezed. <\/p>\n
The result: immense energy from frictional heating. This melts portions of Io\u2019s interior, resulting in a seemingly endless series of lava plumes and ash venting into its atmosphere from the estimated 400 volcanoes that riddle its surface.<\/p>\n
Juno\u2019s close flybys reveal volcanic activity on Io<\/h3>\n
The discovery of this recent activity comes courtesy of Juno\u2019s Jovian Infrared Auroral Mapper (JIRAM) instrument, contributed by the Italian Space Agency. Designed to capture the infrared light (which isn\u2019t visible to the human eye) emerging from deep inside Jupiter, JIRAM has probed the gas giant\u2019s weather layer, peering 30 to 45 miles (48 to 72 kilometers) below its cloud tops. But since NASA extended Juno\u2019s mission, the team has also used the instrument to study the moons Io, Europa, Ganymede, and Callisto.<\/p>\n
During its extended mission, Juno\u2019s trajectory passes by Io every other orbit, flying over the same part of the moon each time. Previously, the spacecraft made close flybys of Io in December 2023 and February 2024, getting within about 930 miles (1,500 kilometers) of its surface. The latest flyby took place on December 27, 2024, bringing the spacecraft within about 46,200 miles (74,400 kilometers) of the moon, with the infrared instrument trained on Io\u2019s southern hemisphere.<\/p>\n
![\"Red](\"https:\/\/earthsky.org\/upl\/2024\/12\/Io-volcanoes-infrared-Juno-July-5-2022.jpg\")
View larger. | Juno captured this stunning infrared view of Io and its many volcanoes on July 5, 2022. Image via NASA\/ JPL-Caltech\/ SwRI\/ ASI\/ INAF\/ JIRAM.<\/figcaption><\/figure>\n Io brings the heat<\/h3>\n
Alessandro Mura, a Juno co-investigator from the National Institute for Astrophysics in Rome, said: <\/p>\n
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JIRAM detected an event of extreme infrared radiance \u2014 a massive hotspot \u2014 in Io\u2019s southern hemisphere, so strong that it saturated our detector. However, we have evidence what we detected is actually a few closely spaced hotspots that emitted at the same time, suggestive of a subsurface vast magma chamber system. The data support that this is the most intense volcanic eruption ever recorded on Io.<\/p>\n<\/blockquote>\n
The JIRAM science team estimates the as-yet-unnamed feature spans 40,000 square miles (100,000 square kilometers). The previous record holder was Io\u2019s Loki Patera, a lava lake of about 7,700 square miles (20,000 square kilometers). The total power value of the new hotspot\u2019s radiance measured well above 80 trillion watts.<\/p>\n
![\"Three](\"https:\/\/earthsky.org\/upl\/2025\/01\/Io-juno-perijove-comparison.jpg\")
Images of Io captured in 2024 by the JunoCam imager aboard NASA\u2019s Juno show significant and visible surface changes (indicated by the arrows) near the Jovian moon\u2019s south pole. These changes occurred between the 66th and 68th perijove (the point during Juno\u2019s orbit when it is closest to Jupiter). Image via NASA\/ JPL-Caltech\/ SwRI\/ MSSS\/ Jason Perry.<\/figcaption><\/figure>\n Volcanic activity on Io leaves a mark<\/h3>\n
The feature was also captured by the mission\u2019s JunoCam visible light camera. The team compared JunoCam images from the two previous Io flybys with those the instrument collected on December 27. And while these most recent images are of lower resolution since Juno was farther away, the relative changes in surface coloring around the newly discovered hotspot are clear. Such changes in Io\u2019s surface are known to be associated with hotspots and volcanic activity.<\/p>\n
An eruption of this magnitude is likely to leave long-lived signatures. Other large eruptions on Io have created varied features, such as pyroclastic deposits (composed of rock fragments spewed out by a volcano), small lava flows that may be fed by fissures, and volcanic-plume deposits rich in sulfur and sulfur dioxide.<\/p>\n
Juno will use an upcoming, more distant flyby of Io on March 3 to look at the hotspot again and search for changes in the landscape. Earth-based observations of this region of the moon may also be possible.<\/p>\n
Bolton said:<\/p>\n
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While it is always great to witness events that rewrite the record books, this new hotspot can potentially do much more. The intriguing feature could improve our understanding of volcanism not only on Io but on other worlds as well.<\/p>\n<\/blockquote>\n
Bottom line: On its most recent flyby, the Juno spacecraft spotted intense volcanic activity on Io, one of Jupiter\u2019s moons. It was the most extreme volcanism ever seen on Io.<\/p>\n
Via NASA<\/p>\n
Read more: Io\u2019s raging volcanoes are self-powered<\/p>\n
Read more: Lava lakes on Io: Juno zooms in on Io\u2019s volcanoes<\/p>\n
<\/div>\n
\n - On its most recent flyby of Io, NASA\u2019s Juno spacecraft<\/strong> detected the most intense volcanic activity ever seen on the Jovian moon.<\/li>\n