Recent microwave measurements from NASA’s Juno spacecraft indicate that Europa’s icy shell could extend nearly 29 kilometers (18 miles) deep, significantly altering planetary scientists’ understanding of how this intriguing moon facilitates the exchange of vital chemicals between its hidden ocean and surface.
Artist’s concept showing a cross-section of Europa’s icy shell. Image credit: NASA / JPL-Caltech / SwRI / Koji Kuramura / Gerald Eichstädt.
Europa has captivated planetary scientists for over 40 years.
The question of whether Jupiter’s icy moons can support life has sparked extensive debate among researchers.
Interest in Europa’s potential habitability surged when NASA’s Galileo spacecraft revealed an ocean of saline water beneath its icy crust, complemented by surface cracks.
On September 29, 2022, NASA’s Juno spacecraft flew by Europa at an altitude of 360 km (220 miles).
During this flyby, Juno’s Microwave Radiometer (MWR), which is primarily designed to analyze Jupiter’s atmosphere, gathered brightness temperature data at various depths within Europa’s icy crust.
Juno project scientist Steve Levin and his team utilized this MWR data to conclude that the icy shell averages approximately 29 kilometers in thickness.
“The estimated thickness of 29 km pertains to the cold, dense, electrically conductive outer layer of Europa’s water ice shell,” Dr. Levin stated.
“If a slightly warmer convective layer exists beneath, the total thickness could be even greater.”
“Conversely, if the ice shell contains a moderate amount of dissolved salts, as some models suggest, the thickness could decrease by around 5 km (3 miles).”
“A thicker shell implies that oxygen and nutrients have longer distances to travel to connect Europa’s surface with its subsurface ocean, as indicated by the MWR data.”
Understanding this exchange process is crucial for future studies on Europa’s habitability.
Furthermore, MWR data shed light on the composition of Europa’s subsurface ice.
This technology uncovered “scatterers,” irregularities such as cracks, pores, and voids that scatter microwaves reflected off the ice.
These scatterers, estimated to be only a few inches in diameter, are believed to extend hundreds of feet below the surface.
The small size and shallow depth of these features suggest they are unlikely to serve as significant pathways for transporting oxygen and nutrients from the surface to the salty ocean beneath.
“The thickness of the ice shell, along with the presence of cracks and pores, adds complexity to our understanding of Europa’s potential for habitability,” remarked Scott Bolton, Ph.D., Juno’s principal investigator at the Southwest Research Institute.
“These findings provide essential context for NASA’s Europa Clipper and ESA’s Juice missions, both en route to the Jupiter system.”
“The Europa Clipper is expected to arrive in 2030, followed by Juice the next year.”
The team’s new results were published in the Journal on December 17, 2025, in Nature Astronomy.
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S.M. Levin et al. 2026. Characterization of Europa’s ice thickness and subsurface structure using the Juno microwave radiometer. Nat Astron 10, 84-91; doi: 10.1038/s41550-025-02718-0
Source: www.sci.news
