According to NASA’s Juno mission data, Europa’s average conductive ice shell measures 29 kilometers thick, providing new constraints on the subsurface ocean’s potential habitability. This measurement evaluates whether useful chemistry can travel between the hidden global sea, the rocky seafloor below, and the heavily irradiated surface far above.
Juno Microwave Radiometer Measurements of Europa
NASA’s Juno spacecraft gathered temperature data at different depths using its Microwave Radiometer (MWR) during a September 29, 2022, flyby. According to findings published in Nature Astronomy by lead researcher Steve Levin, the instrument collected 129 measurements across six frequency channels during a pass within roughly 360 kilometers of the Jovian moon.
Rather than sending a direct radar pulse through the ice, the MWR instrument analyzed microwave radiation emitted by the ice itself. Lower frequencies carried data from deeper layers depending on opacity and temperature. The team modeled brightness temperature changes alongside reflected radio emissions from Jupiter’s radiation belts to determine the vertical temperature gradient. According to NASA, this analysis produced a central estimate of a 29-kilometer conductive ice shell.
Pro Tip: When evaluating planetary ice measurements, remember that models often assume pure water ice and uniform structures, meaning regional geology like ridged plains can alter local shell thickness.
Statistical Uncertainties and Model Assumptions
Researchers reported a formal uncertainty of plus or minus 10 kilometers for the 29-kilometer measurement. According to the study authors, this broader range accounts for unmodelled surface changes that could mimic ice thickness signals in the microwave data.
The baseline model assumes pure water ice without a warmer convective layer beneath the rigid lid. According to NASA, incorporating dissolved salt—similar to compounds evaluated in Europa models—could make the ice more opaque and reduce the thickness estimate by about 5 kilometers. Conversely, a warmer, slowly overturning convective layer underneath could increase the total solid barrier thickness between the surface and the subsurface ocean.
Comparisons Between Europa’s Water Volume and Earth
Europa has a diameter of 3,120 kilometers, making it smaller than Earth’s Moon. Yet, according to NASA’s Europa overview, its hidden global ocean spans roughly 60 to 150 kilometers deep and may hold more than twice as much water as all of Earth’s oceans combined.
While Earth’s oceans average under 4 kilometers deep and face interruption by continents, Europa’s liquid layer is globally continuous. Direct visual confirmation of the ocean remains absent. Instead, independent clues support its existence, notably the induced magnetic response measured by NASA’s Galileo spacecraft as Jupiter’s magnetic field swept past the moon.
Implications for Surface-ocean Chemical Exchange
A thick ice shell complicates the delivery of chemical energy and oxidants produced by Jupiter’s radiation on the surface down to the rocky seafloor. Juno’s microwave data identified shallow scatterers—such as cracks, pores, or voids—with a characteristic vertical scale of about 219 meters. According to the study authors, these shallow features extend only hundreds of meters deep and cannot independently serve as open pipes connecting the surface to the ocean.
A separate study published in Nature Astronomy on July 23, 2026, by Lujendra Ojha, Ankit Barik, and Jacob Buffo, examined fluid and thermal simulations to test direct water exchange. Their models indicated that ascending water from the deep ocean freezes too quickly within narrow dykes to deliver large volumes of liquid, suggesting that local melting within the shell may power any shallow liquid reservoirs rather than direct ocean transport.
Did You Know? Saturn’s moon Enceladus actively vents subsurface water into space, allowing flyby spacecraft to sample its ocean directly, whereas Europa’s thick ice shell keeps its hidden sea heavily concealed.
Upcoming Investigations by the Europa Clipper Mission
Launched on October 14, 2024, NASA’s Europa Clipper is scheduled to reach the Jovian system in April 2030. According to mission parameters, the spacecraft will perform about 50 close flybys using radar, cameras, spectrometers, and magnetic instruments to characterize the ice shell and interior.
The REASON radar instrument will specifically probe internal structures and search for liquid pockets within the ice. While Juno’s data establishes a 29-kilometer baseline estimate, Clipper’s targeted flybys will map regional thickness variations and test models of how Europa deforms under Jupiter’s gravitational pull.
Frequently Asked Questions
How thick is Europa’s ice shell according to Juno?
According to NASA and the study published in Nature Astronomy, Juno’s microwave data produced a central estimate of 29 plus or minus 10 kilometers for the average conductive ice shell in the observed region.
Does Europa have more water than Earth?
According to NASA’s Europa overview, the moon’s hidden global ocean may contain more than twice the combined volume of all Earth’s oceans.
Will NASA’s Europa Clipper drill through the ice?
No. According to mission objectives, Europa Clipper will not land or drill; instead, it will conduct approximately 50 close flybys to study the ice shell, composition, and geology remotely.
Can surface chemicals reach Europa’s ocean easily?
According to recent studies, a 29-kilometer ice shell and rapid freezing in narrow fractures make direct fluid transport from the surface to the deep ocean highly challenging.
Explore More: Want to stay updated on deep-space exploration and ocean worlds? Subscribe to our newsletter for regular mission updates, or check out our latest analysis on planetary habitability.
Related reading