{"id":46464,"date":"2026-07-28T00:14:17","date_gmt":"2026-07-27T16:14:17","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/juno-reveals-surprising-subsurface-tempertures-at-io-remarkably-smooth-surface\/"},"modified":"2026-07-28T00:14:17","modified_gmt":"2026-07-27T16:14:17","slug":"juno-reveals-surprising-subsurface-tempertures-at-io-remarkably-smooth-surface","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/juno-reveals-surprising-subsurface-tempertures-at-io-remarkably-smooth-surface\/","title":{"rendered":"Juno reveals surprising subsurface tempertures at Io, remarkably smooth surface"},"content":{"rendered":"<p><!--[CDATA[<img loading=\"lazy\" width=\"1898\" height=\"1316\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2026\/07\/io-juno-oct-2023-e1785107357626.png\" class=\"attachment-full size-full wp-post-image\" alt=\"\" style=\"float:right; margin:0 0 10px 10px;\" decoding=\"async\" srcset=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2026\/07\/io-juno-oct-2023-e1785107357626.png 1898w, https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2026\/07\/io-juno-oct-2023-e1785107357626-350x243.png 350w, https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2026\/07\/io-juno-oct-2023-e1785107357626-505x350.png 505w, https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2026\/07\/io-juno-oct-2023-e1785107357626-768x533.png 768w, https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2026\/07\/io-juno-oct-2023-e1785107357626-1170x811.png 1170w\" sizes=\"(max-width: 1898px) 100vw, 1898px\" \/--><\/p>\n<p>Following two flybys of Jupiter\u2019s innermost Galilean moon Io, teams using data from NASA\u2019s Juno spacecraft have revealed the first measurements of the temperature below Io\u2019s surface. The flybys revealed substantial subsurface heating on the moon, as well as a surface that is extremely smooth and composed of low-density materials.<\/p>\n<p>Io is the most volcanically active celestial body in the solar system, a characteristic caused by the immense tidal forces from its parent planet. As Io orbits Jupiter, the planet\u2019s extreme gravity stretches and squeezes Io\u2019s surface, generating an internal heat output significantly greater than that of Earth\u2019s. However, until these new measurements, everything about Io\u2019s thermal nature was learned through infrared observations of its surface.<\/p>\n<p><span id=\"more-114340\"><\/span><\/p>\n<p>To make the subsurface temperature measurements, Juno used its Microwave Radiometer (MWR) instrument. Designed to make observations deep into Jupiter\u2019s thick atmosphere, the MWR is multi-wavelength, supporting radiation observations from 1.3 cm to 51 cm wavelengths (600 MHz to 22 GHz frequencies). MWR achieves these observations via six differently sized antennas mounted to the sides of Juno. The MWR has also conducted observations of Ganymede and Europa.<\/p>\n<p><img decoding=\"async\" width=\"100%\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2026\/07\/e1-pia26756-fig-excerpt-09.webp\"><\/p>\n<p id=\"caption-attachment-114345\" class=\"wp-caption-text\">MWR data map showing where heat is rising from Io\u2019s subsurface environment. The colors represent a temperature gradient across Io. (Credit: NASA\/JPL-Caltech\/SwRI\/USGS)<\/p>\n<p>\u201cThe Juno Microwave Radiometer directly observed Io\u2019s heat output by looking below the surface. The surprising discovery that we could see below a rocky moon\u2019s surface has important implications for studying Earth\u2019s volcanoes. Juno has taught us that if we look with an MWR-type instrument near a volcano on Earth, we might see a similar signature in the subsurface temperature gradient, providing new information on how terrestrial volcanoes work,\u201d said co-author and Juno principal investigator Scott Bolton of the Southwest Research Institute.<\/p>\n<aside class=\"penci-sidebar-content widget l2-info\">\n<h4 class=\"widget-title penci-border-arrow\"><span class=\"inner-arrow\">See Also<\/span><\/h4>\n<ul>\n<li>Juno Updates<\/li>\n<li>Space Science Section<\/li>\n<li>L2 Atlas V\/Juno Processing<\/li>\n<li>Click here to join L2<\/li>\n<\/ul>\n<\/aside>\n<p>The team, led by Shannon Brown of NASA\u2019s Jet Propulsion Laboratory, used Juno data from two flybys of Io: the first occurred on Dec. 30, 2023, and the second on Feb. 3, 2024. During both of these flybys, Juno came within approximately 1,500 km of Io\u2019s surface. MWR data revealed that temperatures dramatically increase just feet into the moon\u2019s surface.<\/p>\n<p>\u201cThe instrument measured Io\u2019s thermal emission at depths ranging from a few inches down to tens of feet. Everywhere we looked, we found the temperature rising by more than 40 degrees Fahrenheit just several feet into the surface \u2014 a gradient far steeper than solar heating alone can explain,\u201d Brown said.<\/p>\n<p>Brown et al. have two theories for the sharp increase in temperatures just below the surface. The first theory suggests that Io has a conductive crust, allowing heat to steadily rise to the surface. The measured background heat flow within the crust \u2014 approximately one to three watts per square meter \u2014 equates to an energy release almost 30 times Earth\u2019s average across the entire moon, though localized measurements are far less energetic.<\/p>\n<p><img decoding=\"async\" width=\"100%\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2026\/07\/PIA26484large.jpg\"><\/p>\n<p id=\"caption-attachment-114344\" class=\"wp-caption-text\">Io imaged by Juno during its Dec. 30, 2023, flyby. (Credit: NASA\/JPL-Caltech\/SwRI\/MSSS\/Gerald Eichst\u00e4dt)<\/p>\n<p>The second theory suggests that cooling lava flows could be heating Io\u2019s subsurface environment. These lava flows, trapped under approximately nine to 11 meters of solid crust, are estimated to cover around 10% of Io\u2019s surface at any time.<\/p>\n<p>\u201cIo provides a unique window into learning how tidal heating works throughout the cosmos, a fundamental process that provides energy and heat to worlds that are far from their parent star. This process can not only create the most volcanic body in the solar system, in the case of Io, but also fuels the subsurface oceans on the moons of giant planets, such as Europa and Ganymede. Up until this point, we could only observe the heat escaping at the surface or through eruptions. Now we can characterize how the heat is moving from the interior toward the surface,\u201d Bolton said.<\/p>\n<p>Io\u2019s subsurface temperatures weren\u2019t the only thing revealed from Juno\u2019s flybys in 2023 and 2024.<\/p>\n<p>MWR data also showed that the moon\u2019s surface is remarkably smooth. While Io features many tall mountains, beneath them lay patches of smooth surface that stretch for 100 km or further. Brown et al. determined the smoothness of Io\u2019s surface by mapping how it reflects microwaves, a measurement made possible by Juno flying over overlapping regions at different angles.<\/p>\n<p><img decoding=\"async\" width=\"100%\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2026\/07\/e2-pia26757-io-mwr-footprint2.webp\"><\/p>\n<p id=\"caption-attachment-114346\" class=\"wp-caption-text\">Map highlighting where Juno\u2019s MWR instrument measured Io\u2019s surface. (Credit: NASA\/JPL-Caltech\/SwRI\/USGS)<\/p>\n<p>\u201cAway from its mountains, the surface is more like the Great Plains of North America, and even though Io is a rocky body, the surface material has a very low density \u2014 more like pumice or a fluffy volcanic ash than solid rock,\u201d Brown said.<\/p>\n<p>Juno, launched in August 2011, recently celebrated a decade at Jupiter, inserting itself into orbit around the planet on July 5, 2016. Launched as part of NASA\u2019s New Frontiers program, Juno completed its most recent pass of Jupiter, called \u201cperijoves,\u201d on July 5, 2026 \u2014 the 85th of its mission.<\/p>\n<p><em>(Lead image: Io imaged by Juno in October 2023. Credit: NASA\/JPL-Caltech\/SwRI\/MSSS\/Ted Stryk)<\/em><\/p>\n<p><img decoding=\"async\" width=\"100%\" src=\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2026\/06\/Hawaiian_Shirt_Promo_-_Web.webp\"><\/p>\n<p>The post Juno reveals surprising subsurface tempertures at Io, remarkably smooth surface appeared first on NASASpaceFlight.com.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Following two flybys of Jupiter\u2019s innermost Galilean moon Io, teams using data from NASA\u2019s Juno spacecraft have revealed the first measurements of the temperature below Io\u2019s surface. The flybys revealed substantial subsurface heating on the moon, as well as a surface that is extremely smooth and composed of low-density materials. Io is the most volcanically [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[],"class_list":["post-46464","post","type-post","status-publish","format-standard","hentry","category-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/46464"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=46464"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/46464\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=46464"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=46464"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=46464"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}