NASA’s Juno Takes Temperature of Jupiter’s Fiery Moon Io

5 min read Preparations for Next Moonwalk Simulations Underway (and Underwater) TThe north polar region of Jupiter’s volcanic moon Io was captured by NASA’s Juno during the spacecraft’s 57th close pass of the gas giant on Dec. 30, 2023. Data from that flyby and one on Feb.

3, 2024, is helping scientists understand Io’s interior. Image data: NASA/JPL-Caltech/SwRI/MSSS Image processing by Gerald Eichstädt Lee esta historia en español aquí .  NASA’s Juno mission has provided the first measurements of the temperature below the surface of Jupiter’s moon Io, revealing significant heating within the shallow subsurface of the most volcanically active world in the solar system.

Collected during two close flybys, the data also shows that most of Io’s surface is remarkably smooth and composed of material of very low density. Published Wednesday in the Journal of Geophysical Research: Planets, these findings break new observational ground for both fiery and icy worlds beyond our planet. Io’s extreme volcanism is powered by tidal heating.

The moon is constantly stretched and squeezed by Jupiter’s immense gravity as it travels its slightly elliptical orbit, generating internal heat output many times greater than Earth’s. Until now, virtually everything known about that heat came from infrared observations, which sense only the temperature of the top surface. The latest findings are derived from data collected by the spacecraft’s Microwave Radiometer (MWR) instrument.

“The Juno Microwave Radiometer directly observed Io’s heat output by looking below the surface,” said Scott Bolton, study coauthor and Juno’s principal investigator at Southwest Research Institute in San Antonio. “The surprising discovery that we could see below a rocky moon’s surface has important implications for studying Earth’s volcanoes. ” This map represents data captured by the Microwave Radiometer instrument aboard NASA’s Juno, indicating heat rising from just beneath the surface of Jupiter’s moon Io.

The colors illustrate a distinct temperature gradient across the moon, with the most extreme, localized heat output in red. NASA/JPL-Caltech/SwRI/USGS Fire, ice Juno’s Microwave Radiometer was designed by Bolton to peer beneath Jupiter’s cloud tops to investigate the dynamics and composition of the gas giant’s deep atmosphere. 3 to 51 centimeters).

During the mission’s extended phase , the MWR instrument has provided the opportunity to observe three of the planet’s Galilean moons: Ganymede, Europa, and Io. “The technique is novel in that each wavelength explores different depths, providing a new way to characterize the deep atmosphere of giant planets and the subsurface crusts of icy and rocky moons,” said Bolton. ” During flybys on Dec.

30, 2023, and Feb. 3, 2024, the solar-powered Juno spacecraft came within about 930 miles (1,500 kilometers) of the moon’s surface. “The instrument measured Io’s 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 — a gradient far steeper than solar heating alone can explain,” said Shannon Brown, the paper’s lead author at NASA’s Jet Propulsion Laboratory in Southern California. The data suggests two possible explanations. First, heat could be rising steadily through a conductive crust.

While this background heat flow — measured at 1 to 3 watts per square meter — is relatively gentle on a local scale (roughly equivalent to a small nightlight glowing under every square yard), across the entire moon it represents a release of energy up to 30 times Earth’s average. Alternatively, the signal could be coming from cooling lava flows, capped by roughly 30 to 35 feet (9 to 11 meters) of solidified crust, that cover about 10% of the moon’s surface at any given time. “Io 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,” said Bolton.

“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. ” This graphic illustrates the areas of Io sampled by the Microwave Radiometer instrument aboard NASA’s Juno spacecraft during two close flybys of the Jovian moon.

NASA/JPL-Caltech/SwRI/USGS Great plains of Io Another big insight gained from the two flybys is just how smooth Io is. Prior to the recent findings, the moon was known for its tall mountains, but the MWR indicates that apart from this visible topography, the surface features expansive smooth patches that stretch for 60 miles (100 kilometers) or more. Because Juno flew by overlapping regions of Io at different angles, the team was able to map how the surface reflects microwaves, much like an airline passenger might see the ocean flash with sunlight only at specific angles.

“Away 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 — more like pumice or a fluffy volcanic ash than solid rock,” said Brown. More about Juno A division of Caltech in Pasadena, California, JPL manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest Research Institute. Juno is part of NASA’s New Frontiers Program, which is managed at the agency’s Marshall Space Flight Center in Huntsville, Alabama, for the NASA’s Science Mission Directorate in Washington.

Lockheed Martin Space in Denver built and operates the spacecraft. org   2026-050 Share Details Last Updated Jul 22, 2026 Related Terms Juno Io Jet Propulsion Laboratory Jupiter Planetary Science Explore More 2 min read Mapping Io’s Hidden Heat With NASA’s Juno Description This graphic illustrates the areas of Jupiter’s moon Io sampled by the Microwave Radiometer… Article 15 hours ago 2 min read NASA’s Juno Peers Beneath Io’s Surface Description This map represents data captured by the Microwave Radiometer (MWR) aboard NASA’s Juno spacecraft,… Article 15 hours ago 5 min read US-India Satellite Delivers Data, Reveals ‘Hummingbird’ in Antarctica Article 1 day ago Keep Exploring Discover Related Topics Jupiter: Exploration Juno NASA’s Juno spacecraft has explored Jupiter, its moons, and rings since 2016, gathering breakthrough science and breathtaking imagery.