Europa has captivated scientists for decades because a vast ocean of liquid water may be concealed beneath its frozen surface.
That buried sea has made Jupiter’s icy moon one of the most promising places in the solar system to investigate whether conditions suitable for life might exist beyond Earth. However, new research led by Rutgers scientist Lujendra Ojha indicates that reaching material from Europa’s deep ocean may be much more difficult than previously believed.
Testing a Possible Route Through Europa’s Ice
In a study published in Nature Astronomy, Ojha and his colleagues used computer simulations to examine whether water from Europa’s global ocean could travel upward through fractures in the ice and accumulate in shallow underground reservoirs. If such pockets exist, future spacecraft could potentially detect or sample them more easily than the ocean 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?”
The results suggest that the trip from the deep ocean into the upper layers of ice is far less likely than many 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.”
Shallow Water May Have a Different Source
The conclusion could significantly affect how scientists interpret future discoveries on Europa. If spacecraft detect shallow pockets of liquid water beneath the surface, those reservoirs may not contain water that originated in the moon’s deep ocean. They could instead have formed when sections of the ice shell melted locally.
The difference is important because scientists are drawn to Europa by the combination of liquid water, chemistry and energy, which are all essential factors when evaluating whether an environment could support life. Shallow water would be far easier to investigate than the deeply buried ocean. But if those reservoirs are isolated from the ocean, they may offer little information about Europa’s most scientifically compelling environment.
Europa Clipper and JUICE Approach Jupiter
The findings come as two major missions travel toward the Jupiter system. NASA’s Europa Clipper mission launched in October 2024 and is expected to reach Jupiter in April 2030. It will orbit the planet and complete 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 spacecraft are expected to provide a much clearer picture of Europa’s frozen shell, surface chemistry and potential subsurface water. Radar aboard Europa Clipper may help researchers determine whether shallow reservoirs are present and reveal their size and structure.
Far below Europa’s bitterly cold exterior, a global ocean may remain liquid because Jupiter’s immense gravitational pull repeatedly stretches and compresses the moon. That motion produces internal heat, which becomes trapped beneath the thick ice shell.
Could Water Rise Through Fractures?
The new study examined dikes, which are narrow fractures that could theoretically serve as channels for ocean water moving upward through the ice. The concept loosely resembles the way molten rock travels through cracks in Earth’s crust before contributing to volcanic eruptions. On frozen worlds, similar activity involving water and ice rather than molten rock is called cryovolcanism.
Ojha cautioned that the comparison between the two processes has clear limits.
“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 factor that previous models may have underestimated is turbulence. Earlier simulations often assumed that water would rise through Europa’s ice in a relatively smooth and organized flow. The Rutgers-led research instead suggests that the water would move rapidly and chaotically, repeatedly mixing against the cold walls of the fracture and quickly transferring its heat 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.”
Ice Crystals Could Clog the Path
As the rising water loses heat, it may become supercooled, remaining liquid even after its temperature falls below the normal freezing point. In that state, small crystals known as frazil ice can begin to form. Over time, those crystals may accumulate and block the fracture.
According to the simulations, narrow cracks could freeze closed in a matter of hours. Larger fractures might transport more water under ideal conditions, but turbulence makes even those situations much less favorable. The team found that moving enough water to create some of Europa’s visible surface features would require fractures that are unrealistically long or present in unusually large numbers.
The findings point to a version of Europa in which any shallow liquid water may have formed separately from the global ocean. Rather than traveling upward from great depths, it may have been produced when localized heat melted portions of 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.”