Juno Spacecraft Measures Thickness of Europa's Ice Shell

NASA's solar-powered Juno spacecraft provides new insights into the icy crust of Jupiter's moon Europa.

Jan. 27, 2026 at 2:31pm

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Results from NASA's Juno mission have provided a new measurement of the thickness of the ice shell encasing Jupiter's moon Europa. Using the spacecraft's Microwave Radiometer (MWR), scientists determined that the ice shell averages about 18 miles (29 kilometers) thick in the region observed during Juno's 2022 flyby of Europa. This is the first measurement to discriminate between thin and thick shell models for Europa's ice.

Why it matters

Understanding the thickness and characteristics of Europa's ice shell is crucial for investigating the moon's potential habitability. The ingredients for life may exist in the saltwater ocean beneath the ice, and the ice shell's properties provide important clues about the internal workings of this high-priority science target.

The details

The Juno measurement using the MWR instrument found that the cold, rigid, conductive outer layer of Europa's pure water ice shell is about 18 miles thick. If a slightly warmer, convective inner layer also exists, the total ice shell thickness would be even greater. The data also revealed the presence of small-scale 'scatterers' such as cracks, pores, and voids in the near-surface ice, which are unlikely to provide a significant pathway for oxygen and nutrients to reach the subsurface ocean.

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

The players

Juno

NASA's solar-powered spacecraft that is investigating Jupiter and its moons.

Steve Levin

Juno project scientist and co-investigator from NASA's Jet Propulsion Laboratory.

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, scheduled to arrive in 2030.

Juice (JUpiter ICy moons Explorer)

The European Space Agency's upcoming mission to the Jovian system, scheduled 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

The Europa Clipper mission will arrive at Jupiter's moon Europa in 2030, while the ESA's Juice mission will arrive the following year. These upcoming missions will provide additional data and insights to further understand the characteristics of Europa's ice shell and its potential for habitability.

The takeaway

The new measurements from Juno's Microwave Radiometer provide crucial information about the thickness and structure of Europa's ice shell, which is a key factor in determining the moon's potential to host a subsurface ocean and habitable environment. This data will help guide the upcoming Europa Clipper and Juice missions as they investigate this high-priority science target in the Jovian system.