New observations from the James Webb Space Telescope (JWST) are painting a new picture of Jupiter’s moon Europa and revealing the hidden chemistry of the icy moon’s interior.
For decades, scientists pictured Europa’s frozen surface as a still, silent shell. But the new observations reveal that it’s actually a dynamic world that’s far from frozen in time.
“We think that the surface is fairly porous and warm enough in some areas to allow the ice to recrystallize rapidly,” Richard Cartwright, a spectroscopist at Johns Hopkins University’s Applied Physics Laboratory and lead author of the new study, said in a statement.
Perhaps even more exciting is what this surface activity reveals about Europa’s subsurface ocean. The presence of geologic activity and ongoing cycling between the subsurface and surface make “chaos terrains” — highly disrupted regions where blocks of ice seem to have broken off, drifted and refrozen — especially valuable as potential windows into Europa’s interior.
The study focused on two regions in Europa’s southern hemisphere: Tara Regio and Powys Regio. Tara Regio, in particular, stands out as one of the moon’s most intriguing areas. Observations from JWST detected crystalline ice both at the surface and deeper below — challenging previous assumptions about how ice is distributed on Europa.
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By measuring the spectral properties of these “chaos” regions using remotely sensed data, scientists could gain valuable insight about Europa’s chemistry as well as its potential for habitability, they explained in the paper, which was published May 28 in The Planetary Science Journal.
“Our data showed strong indications that what we are seeing must be sourced from the interior, perhaps from a subsurface ocean nearly 20 miles (30 kilometers) beneath Europa’s thick icy shell,” Ujjwal Raut, program manager at the Southwest Research Institute and co-author of the study, said in the statement.
Hidden chemistry
Raut and his team conducted laboratory experiments to study how water freezes on Europa, where the surface is constantly bombarded by charged particles from space. Unlike on Earth, where ice naturally forms a hexagonal crystal structure, the intense radiation on Europa disrupts the ice’s structure, causing it to become what’s known as amorphous ice — a disordered, noncrystalline form.
The experiments played a crucial role in demonstrating how the ice changes over time. By studying how the ice transforms between different states, scientists can learn more about the moon’s surface dynamics. When combined with fresh data from JWST, these findings add to a growing body of evidence showing that a vast, hidden liquid ocean lies beneath Europa’s icy shell.
“In this same region […] we see a lot of other unusual things, including the best evidence for sodium chloride, like table salt, probably originating from its interior ocean,” Cartwright said. “We also see some of the strongest evidence for CO2 and hydrogen peroxide on Europa. The chemistry in this location is really strange and exciting.”
These regions, marked by fractured surface features, may point to geologic activity pushing material up from beneath Europa’s icy shell.
JWST’s NIRSpec instrument is especially well suited for studying Europa’s surface because it can detect key chemical signatures across a wide range of infrared wavelengths. This includes features associated with crystalline water ice and a specific form of carbon dioxide called ¹³CO₂, which are important for understanding the moon’s geologic and chemical processes.
NIRSpec can measure these features all at once while also creating detailed maps that show how these materials are distributed across Europa’s surface. Its high sensitivity and ability to collect both spectral and spatial data make it an ideal tool for uncovering clues about what lies beneath Europa’s icy crust.
The team detected higher levels of carbon dioxide in these areas than in surrounding regions. They concluded that it likely originates from the subsurface ocean rather than from external sources like meteorites, which would have resulted in a more even distribution.
Moreover, carbon dioxide is unstable under Europa’s intense radiation environment, suggesting that these deposits are relatively recent and tied to ongoing geological processes. “The evidence for a liquid ocean underneath Europa’s icy shell is mounting, which makes this so exciting as we continue to learn more,” Raut said.
Another intriguing finding was the presence of carbon-13, an isotope of carbon. “Where is this 13CO2 coming from? It’s hard to explain, but every road leads back to an internal origin, which is in line with other hypotheses about the origin of 12CO2 detected in Tara Regio,” Cartwright said.
This study arrives as NASA’s Europa Clipper mission is currently en route to the Jovian moon, with an expected arrival in April 2030. The spacecraft will perform dozens of flybys, with each one bringing it closer to Europa’s surface to gather critical data about the ocean hidden beneath the moon’s icy crust.