Europa, one of Jupiter’s icy moons, has fascinated scientists for decades because a vast ocean of liquid water may lie hidden beneath its frozen surface.
Europa’s subsurface ocean makes the moon one of the most promising locations in the solar system for investigating whether environments capable of supporting life exist beyond Earth. However, new research led by Rutgers scientist Lujendra Ojha suggests that material from Europa’s deep ocean may be much harder to reach than scientists previously thought.
Can Water Move Through Europa’s Ice?
Published in Nature Astronomy, the study used computer simulations to investigate whether water from Europa’s global ocean could rise through fractures in the moon’s icy shell and collect in shallow underground reservoirs. If these pockets exist, future spacecraft might detect or sample them more easily than the ocean located far below the surface.
“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 study’s results indicate that water traveling from Europa’s deep ocean into the upper ice shell is far less likely than many earlier models suggested.
“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 on Europa May Have a Local Origin
The findings could influence how scientists interpret future evidence of liquid water beneath Europa’s surface. If spacecraft identify shallow reservoirs, that water may not have come from the moon’s deep global ocean. Instead, it could have formed when localized areas of Europa’s ice shell melted.
This distinction is scientifically important. Researchers are interested in Europa because it may contain three key ingredients associated with habitability: liquid water, chemical compounds and energy. Shallow water would be far easier to study than the ocean buried beneath many miles of ice. However, if the reservoirs are isolated from the ocean, they may reveal less about Europa’s most intriguing environment.
Europa Clipper and JUICE Will Study Jupiter’s Icy Moons
The research comes as two major space missions journey toward the Jupiter system. NASA’s Europa Clipper mission launched in October 2024 and is expected to reach Jupiter in April 2030. The spacecraft will orbit Jupiter and conduct 49 close flybys of Europa. The European Space Agency’s Jupiter Icy Moons Explorer, or JUICE, launched in April 2023 and is scheduled to arrive at Jupiter in July 2031.
Together, the missions should provide valuable information about Europa’s icy shell, surface chemistry and possible subsurface water. Radar instruments aboard Europa Clipper may help scientists determine whether shallow liquid reservoirs exist and reveal their depth, size and structure.
Although Europa’s surface is extremely cold, a global ocean may remain liquid beneath the ice. Jupiter’s powerful gravity repeatedly stretches and compresses the moon, generating internal heat that becomes trapped below its thick ice shell.
Could Fractures Carry Ocean Water Toward the Surface?
The new study focused on dikes, narrow fractures that could theoretically transport ocean water upward through Europa’s ice. The idea is loosely comparable to molten rock moving through cracks in Earth’s crust before feeding volcanic eruptions. On icy worlds, water- and ice-related activity is known as cryovolcanism.
Ojha emphasized that the comparison between cryovolcanism and volcanic activity on Earth has important limitations.
“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 researchers identified turbulence as a factor that earlier models may have underestimated. Previous simulations often treated water moving through Europa’s ice as a relatively smooth and organized flow. The Rutgers-led study suggests instead that the water would move quickly and chaotically, swirling against the cold walls of the fracture and rapidly transferring 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.”
Frazil Ice Could Block Europa’s Fractures
As rising water loses heat, it may become supercooled, remaining liquid even when its temperature drops below the normal freezing point. Under these conditions, tiny ice crystals called frazil ice can form. As the crystals accumulate, they could clog and seal the fracture.
The simulations indicate that narrow cracks could freeze shut within hours. Wider fractures might allow more water to move upward under ideal conditions, but turbulence would still make the process highly inefficient. The researchers concluded that transporting enough water to create some of Europa’s visible surface features would require fractures that are unrealistically long or occur in exceptionally large numbers.
The results support a model in which shallow liquid water on Europa forms independently of the moon’s deep ocean. Rather than rising from great depths, the water may be generated when localized sources of heat melt sections 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.”
Source: www.sciencedaily.com