Europa’s Ice Shell Blocks Ocean Water From Reaching Surface, Study Finds

Liquid water from Europa’s subsurface ocean likely cannot reach shallow reservoirs near the moon’s surface without freezing along the way, according to a study published in Nature Astronomy. The research, led by Rutgers University planetary scientist Lujendra Ojha, used computer simulations to test whether cracks in Europa’s ice shell could carry ocean water upward — and found that turbulence causes the water to lose heat too quickly to complete the journey. Europa has drawn scientific interest for decades because its ice-covered ocean may hold conditions capable of supporting life.

Modeling Water’s Journey Through the Ice

Ojha’s team modeled dikes, narrow fractures that could in theory allow ocean water to rise through Europa’s ice shell toward the surface, the way molten rock moves through cracks before feeding volcanic eruptions on Earth — a process known on icy worlds as cryovolcanism. Earlier models generally assumed the rising water moved in an orderly way. The Rutgers-led simulations instead treated the flow as turbulent, mixing against the cold walls of each fracture as it rises.

“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.”

Fractures That Freeze Shut Within Hours

As the rising water cools, it can become supercooled — remaining liquid below its normal freezing point — until tiny ice crystals called frazil ice begin to form, build up and clog the fracture. The simulations found that narrow cracks could freeze solid within hours. Wider fractures could carry more water under idealized conditions, but the same turbulence effects apply. To deliver enough water to explain some of Europa’s observed surface features, the researchers found the fractures would need to be unrealistically long or occur in unrealistically large numbers.

“Ice and liquid water are fundamentally different than lava and the volcanoes that we see here on Earth,” Ojha said. “I think there’s some fundamental physics that’s missing here, and so I wanted to explore that.”

A Different Origin for Shallow Water

The findings suggest that if shallow pockets of liquid water exist beneath Europa’s surface, they may not be directly connected to the deep ocean. Instead, they are more likely produced by localized heating and melting within the ice shell itself, rather than water rising from below. “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.”

That distinction matters for astrobiology, since liquid water, chemistry and energy are the essential ingredients scientists look for when assessing whether an environment beyond Earth could support life. A shallow reservoir is far easier for a spacecraft to detect or sample than an ocean buried many kilometers down, but only if that reservoir is actually connected to the ocean below.

Two Spacecraft Will Test the Model

The study arrives as two missions head toward the Jupiter system. NASA’s Europa Clipper, launched in October 2024, is scheduled to arrive at Jupiter in April 2030 and will make 49 close flybys of Europa, using an ice-penetrating radar instrument designed to search for shallow water pockets beneath the surface. The European Space Agency’s Jupiter Icy Moons Explorer (JUICE), launched in April 2023, is scheduled to arrive at Jupiter in July 2031, and will study Europa alongside Jupiter’s other large icy moons.

Beneath its frozen surface, Europa is thought to host a global ocean kept liquid by heat generated as Jupiter’s gravity continually squeezes and stretches the moon. If Europa Clipper’s radar detects shallow reservoirs, the Rutgers findings suggest scientists will need to determine whether that water originated locally in the ice or connects to the ocean below before drawing conclusions about habitability.

The result does not rule out the existence of shallow water on Europa, but it complicates a simple readout: a detected reservoir may say more about local melting within the ice shell than about the deep ocean scientists are most interested in probing. That distinction will directly shape how researchers interpret data once Europa Clipper and JUICE begin returning radar observations of the moon in the next decade.

Source: Rutgers University — Department of Earth and Planetary Sciences. Published in Nature Astronomy. Primary source: nature.com/articles/s41550-026-02918-2 (Rutgers Today: rutgers.edu/news/why-europas-hidden-ocean-may-be-more-difficult-reach-scientists-thought).