NASA's Juno Measures Thickness Of Europa's Ice Shell

Juno's microwave radiometer provides new insights into the icy crust of Jupiter's moon Europa.

Jan. 28, 2026 at 12:55am

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Data from NASA's Juno mission has provided new insights into the thickness and subsurface structure of the icy shell encasing Jupiter's moon Europa. Using the spacecraft's Microwave Radiometer (MWR), mission scientists determined that the shell averages about 18 miles (29 kilometers) thick in the region observed during Juno's 2022 flyby of Europa. The Juno measurement is the first to discriminate between thin and thick shell models that have suggested the ice shell is anywhere from less than half a mile to tens of miles thick.

Why it matters

Uncovering a variety of characteristics of Europa's ice shell, including its thickness, provides crucial pieces of the puzzle for understanding the moon's internal workings and the potential for the existence of a habitable environment. The thick shell implies a longer route that oxygen and nutrients would have to travel to connect Europa's surface with its subsurface ocean, which may be relevant to future studies of Europa's habitability.

The details

The MWR data also provides new insights into the makeup of the ice just below Europa's surface, revealing the presence of "scatterers" - irregularities in the near-surface ice such as cracks, pores, and voids that scatter the instrument's microwaves reflecting off the ice. These scatterers are estimated to be no bigger than a few inches in diameter and appear to extend to depths of hundreds of feet below Europa's surface, suggesting they are unlikely to be a significant pathway for oxygen and nutrients to travel from Europa's surface to its salty ocean.

  • On Sept. 29, 2022, Juno came within about 220 miles (360 kilometers) of Europa's frozen surface.
  • The new estimate on the ice thickness in the near-surface icy crust was published on Dec. 17 in the journal Nature Astronomy.

The players

Juno

NASA's solar-powered spacecraft that has provided new insights into the thickness and subsurface structure of the icy shell encasing Jupiter's moon Europa.

Steve Levin

Juno project scientist and co-investigator from NASA's Jet Propulsion Laboratory in Southern California, which manages the mission.

Scott Bolton

Principal investigator of Juno from the Southwest Research Institute in San Antonio.

Europa Clipper

NASA's upcoming mission to Jupiter's moon Europa, set to arrive in 2030.

Juice (JUpiter ICy moons Explorer)

The European Space Agency's upcoming mission to the Jovian system, set to arrive in 2031.

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What they’re saying

“The 18-mile estimate relates to the cold, rigid, conductive outer-layer of a pure water ice shell. 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.”

— Steve Levin, Juno project scientist and co-investigator

“How thick the ice shell is and the existence of cracks or pores within the ice shell are part of the complex puzzle for understanding Europa's potential habitability. They provide critical context for NASA's Europa Clipper and the ESA (European Space Agency) Juice (JUpiter ICy moons Explorer) spacecraft - both of which are on their way to the Jovian system.”

— Scott Bolton, Principal investigator of Juno

What’s next

Europa Clipper will arrive at Jupiter's moon Europa in 2030, while Juice will arrive the year after. These upcoming missions will provide further insights into the characteristics of Europa's ice shell and its potential for habitability.

The takeaway

The new measurements from Juno's microwave radiometer have provided the first clear distinction between thin and thick models of Europa's ice shell, offering crucial data to understand the moon's internal structure and potential for hosting a habitable environment in its subsurface ocean.