For decades, Europa has held a particular kind of allure for planetary scientists. Beneath its cracked, frozen shell, Jupiter’s fourth-largest moon is thought to hide a global ocean of liquid water — one of the most promising places in the solar system to look for the conditions that could support life. The trouble has always been access: that ocean sits many kilometers below an icy crust, far out of reach of any spacecraft currently in development.
One hope has been that nature might do the drilling for us. If liquid water from the deep ocean could work its way upward through cracks in the ice and pool in shallow reservoirs closer to the surface, a future lander or orbiter might sample that water without ever touching the ocean itself. A new study led by Rutgers University geophysicist Lujendra Ojha suggests that shortcut may be far less likely than scientists have hoped.
Published in Nature Astronomy, the study used computer simulations to test whether ocean water could realistically rise through fractures in Europa’s ice shell without freezing solid along the way. “The mystery we wanted to solve was whether this journey is actually possible,” said Ojha, an associate professor in Rutgers’ Department of Earth and Planetary Sciences. “Can liquid water rise from Europa’s deep ocean toward the surface without freezing en route?”
The answer his team arrived at is discouraging for anyone hoping for an easy sample of Europa’s ocean. “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 process under scrutiny is a version of what’s known as cryovolcanism — essentially volcanism with ice and water standing in for molten rock. On Earth, magma forces its way through cracks called dikes on its way to feeding a volcano. Scientists have long modeled Europa’s plumbing in similar terms, imagining ocean water pushing upward through icy dikes toward the surface. But Ojha argues the analogy breaks down quickly under close inspection. “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.”
The missing physics, in this case, is turbulence. Earlier models tended to treat rising water as moving in an orderly, predictable column. Ojha’s simulations instead show water moving chaotically through narrow fractures, churning against the frigid walls of the crack and shedding heat rapidly into the surrounding ice. “This water that’s going to come up, it’s going to be turbulent,” he 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.”
That rapid cooling creates a further complication. As the turbulent water loses heat, it can become supercooled — remaining liquid even after dropping below its normal freezing point. Under those conditions, tiny ice crystals called frazil ice begin to form, accumulate, and clog the very fracture the water is trying to travel through. According to the simulations, narrow cracks could freeze completely shut within hours. Wider fractures fare somewhat better under idealized conditions, but once turbulence is factored in, even those become far less promising conduits. To deliver enough water to account for certain surface features on Europa, the researchers found, the fractures would need to be improbably long or occur in unrealistically large numbers. <p>The upshot is a rethinking of what shallow water on Europa, if it exists, might actually represent. Rather than a direct extension of the deep ocean, any shallow reservoirs are more likely to be local affairs — pockets formed by heat generated and ice melted within the shell itself, disconnected from the ocean below. That distinction carries real scientific weight. Europa’s appeal rests on the combination of liquid water, chemistry, and energy that might exist in its ocean; a shallow pocket of water that never touched that ocean would be easier to reach, but far less informative about the moon’s potential habitability.
The findings arrive at a pointed moment. Two spacecraft are currently en route to the Jupiter system with instruments built in part to probe exactly these questions. NASA’s Europa Clipper, launched in October 2024, is scheduled to arrive in April 2030 and will make 49 close flybys of the moon, using radar to peer into its ice shell. The European Space Agency’s JUICE mission, launched in April 2023, arrives in July 2031. Together, the two missions should give scientists their most detailed look yet at Europa’s ice shell, surface chemistry, and any subsurface water it might contain — with Europa Clipper’s radar potentially able to determine whether shallow reservoirs exist at all, and how they’re structured.
Europa’s ocean is thought to stay liquid thanks to the immense gravitational pull of Jupiter, which continually flexes and squeezes the moon, generating internal heat that the overlying ice shell traps in place. Understanding how — or whether — that heat and water ever reach the surface has direct consequences for how future missions interpret whatever they find there.
“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.”
Endnotes
1. Ojha, L., et al. “Limited direct fluid exchange between the deep subsurface ocean and the shallow subsurface environment of Europa.” Nature Astronomy (2026). DOI: 10.1038/s41550-026-02918-2
2. Rutgers University press release, July 23, 2026, via EurekAlert!: https://www.eurekalert.org/news-releases/1137406
