Using data from the Juno spacecraft’s Microwave Radiometer (MWR) instrument, researchers at NASA’s Jet Propulsion Laboratory have measured that Europa’s ice shell, covering its subsurface global ocean, is about 18 miles (29 kilometers) thick.
The result is based on data collected on September 29, 2022, when the Juno spacecraft flew within about 220 miles (360 kilometers) of Europa’s icy surface.
Steve Levin, Juno project scientist and co-investigator at NASA’s Jet Propulsion Laboratory, said in a statement on January 27, 2026:
The 18-mile estimate relates to the cold, rigid, conductive outer-layer of a pure water ice shell.
Levin added:
If an inner, slightly warmer convective layer also exists, which is possible, the total ice shell thickness would be even greater. If the ice shell contains a modest amount of dissolved salt, as suggested by some models, then our estimate of the shell thickness would be reduced by about 3 miles.
Juno’s measurements also ended a debate between thin and thick shell models, which had suggested the ice shell could be anywhere from less than half a mile to tens of miles thick.
Beyond Earth, Jupiter’s moon Europa is a top-priority target for studying habitability in our solar system.
However, the thick shell, as suggested by the MWR data, implies a longer route that oxygen and nutrients would have to travel to connect Europa’s surface with its subsurface ocean. This feature could reduce the potential habitability in the saltwater ocean beneath the ice shell.
Currently, NASA’s Europa Clipper and ESA’s JUICE (Jupiter Icy Moons Explorer) spacecraft are on their way to the Jovian system. We will gain new insights into Europa’s habitability when the two spacecraft reach there in 2030 and 2031, respectively.
The new research on Europa’s ice shell thickness was published in Nature Astronomy on December 17, 2025.
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