NASA’s Juno Peers Beneath Io’s Surface: Subsurface Heat Map Reveals Hidden Volcanism
NASA's Juno mission has unveiled a new map of Jupiter's moon Io, using microwave radiometry to peer beneath its crust. The data reveal two major subsurface heat sources, one coinciding with an active lava flow, providing unprecedented insight into Io's internal volcanic engine.
NASA’s Juno Peers Beneath Io’s Surface: Subsurface Heat Map Reveals Hidden Volcanism
NASA’s Juno spacecraft has delivered a groundbreaking view of Jupiter’s volcanic moon Io—not from above, but from beneath its surface. Using its Microwave Radiometer (MWR), Juno has mapped the heat rising from Io’s shallow crust, revealing two massive subsurface hot spots that hint at the moon’s intense internal activity.
The Microwave Radiometer: Seeing Through the Crust
Unlike infrared instruments that only capture surface temperatures, Juno’s MWR uses low-frequency microwaves—specifically at 0.6 and 1.25 gigahertz—to penetrate between 2 and 6 meters (roughly 6 to 20 feet) into Io’s crust. This allows scientists to measure heat stored just beneath the surface, offering a new perspective on the moon’s geology.
The map (shown below) uses color coding to represent temperature gradients: red indicates the hottest subsurface areas, yellow intermediate, and green the coolest.
Two Major Hot Spots: A Tale of Internal Fire
The most striking feature is a large red anomaly in the upper left, between 60 and 120 degrees west longitude. Here, subsurface temperatures are 10 to 20 Kelvin (18 to 36 degrees Fahrenheit) warmer than surrounding areas. This region aligns perfectly with the Zal Montes Patera complex, where Juno’s Stellar Reference Unit previously detected an active lava flow.
A second significant heat source appears near the equator, stretching from 0 to 50 degrees west longitude. Together, these anomalies indicate substantial internal heating within the upper tens of meters of Io’s crust—likely driven by tidal forces from Jupiter.
Temperature Gradient: From Fiery Equator to Frigid Pole
Beyond the hot spots, the map reveals a clear latitudinal gradient. Yellow zones denote intermediate temperatures that warm to about -190°F (-123°C, or 150 Kelvin) near the equator. Green areas at higher northern latitudes are the coolest, dropping to roughly -298°F (-183°C, or 90 Kelvin) near the pole.
This contrast underscores how Io’s internal heat is concentrated in specific volcanic regions rather than being uniformly distributed.
Mission and Science Team
NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, manages the Juno mission for principal investigator Scott Bolton of the Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama. The MWR instrument was built by JPL, while Lockheed Martin Space in Denver built and operates the spacecraft.
For more information about Juno, visit NASA’s Juno page.
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