Europa, one of Jupiter’s icy moons, long has fascinated scientists because of what may lie beneath its frozen shell: a global ocean of liquid water.
That hidden ocean has made Europa one of the most compelling places in the solar system to study the conditions that might support life. But new research led by Rutgers scientist Lujendra Ojha suggests one of the most promising shortcuts to Europa’s ocean may be far more complicated than previously thought.
In a study published in Nature Astronomy , Ojha and colleagues used computer simulations to test whether liquid water from Europa’s deep ocean could rise through cracks in the ice and collect in shallow reservoirs closer to the surface. Such reservoirs, if they exist, could be easier for future missions to detect or sample than the ocean buried far below.
“The mystery we wanted to solve was whether this journey is actually possible,” said Ojha, an associate professor in the Department of Earth and Planetary Sciences at the Rutgers School of Arts and Sciences. “Can liquid water rise from Europa’s deep ocean toward the surface without freezing along the way?”
Their conclusion: The route from deep ocean to shallow ice is probably much more difficult than scientists have assumed.
“There’s an icy shell, there’s water underneath, and there’s all this speculation about how that water can come from deep underground and make its way all the way up without freezing en route,” Ojha said. “That’s really what we think we disproved.”
The finding has important implications for future exploration of Europa. If shallow pockets of liquid water are found beneath the moon’s surface, they may not necessarily contain water from Europa’s deep ocean. Instead, they may have formed locally, from ice that melted within the shell itself.
That distinction matters. Scientists are interested in Europa because liquid water, chemistry and energy are all essential ingredients in the search for habitable environments beyond Earth. A shallow reservoir would be easier to reach than the deep ocean. But if that reservoir isn’t connected to the ocean, it may not reveal what is happening in Europa’s most intriguing environment.
The work arrives as two major spacecraft missions are on their way to the Jupiter system. NASA’s Europa Clipper mission launched in October 2024 and is scheduled to arrive at Jupiter in April 2030, where it will orbit the planet and make 49 close flybys of Europa. The European Space Agency’s Jupiter Icy Moons Explorer mission, known as JUICE, launched in April 2023 and is scheduled to arrive at Jupiter in July 2031.
Together, the missions are expected to give scientists a far more detailed view of Europa’s ice shell, surface composition and possible subsurface water. Europa Clipper’s radar instrument may help scientists determine whether shallow reservoirs exist and how they are structured.
Beneath Europa’s extremely cold surface, a global ocean may remain liquid because Jupiter’s powerful gravity continually squeezes and stretches the moon, generating internal heat that is trapped by the overlying ice shell.
The study focuses on dikes, narrow cracks or fractures that could, in theory, allow water from the ocean to rise upward through the ice. The idea is somewhat similar to the way molten rock can move through cracks on Earth before feeding volcanic activity. On icy worlds, the process is known as cryovolcanism, or volcanism involving ice and water rather than molten rock.
Ojha said that comparison is useful only up to a point.
“Ice and liquid water are fundamentally different than lava and the volcanoes that we see here on Earth,” he said. “I think there’s some fundamental physics that’s missing here, and so I wanted to explore that.”
One missing piece, Ojha said, is turbulence. Earlier models often treated water rising through Europa’s ice as if it moved in a relatively orderly way. But the Rutgers-led simulations suggest the water would likely move fast and turbulently through the fractures, mixing against the cold walls of the crack and losing heat quickly into the surrounding ice.
“This water that’s going to come up, it’s going to be turbulent,” Ojha said. “It’s going to be left and right, it’s going to be up and down, it’s going to have a swirling motion. And when that happens, that liquid water is going to cool very, very fast as it approaches the surface.”
As the water cools, it can become supercooled, meaning it remains liquid even after dropping below its normal freezing temperature. Under those conditions, tiny ice crystals called frazil ice can form, build up and clog the pathway.
The simulations show that narrow cracks could freeze shut within hours. Wider cracks could carry more water under idealized conditions, but turbulence makes those scenarios far less favorable. The researchers found that to deliver enough water to form some of Europa’s surface features, the fractures would need to be unrealistically long or occur in large numbers.
The result is a picture of Europa in which shallow water, if present, may have a different origin than many scientists have hoped. Rather than rising directly from the ocean, the water may be produced by localized heating and melting inside the ice shell.
“Our work suggests that Europa’s ice shell may be a stronger barrier between the ocean and the surface than previously assumed,” Ojha said. “This helps future missions interpret what they find and better understand where to look for signs of habitability.”
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Nature Astronomy
Computational simulation/modeling
Not applicable
Limited direct fluid exchange between the deep subsurface ocean and the shallow subsurface environment of Europa
23-Jul-2026
The authors declare no competing interests.