Jupiter's moon Europa has long been considered one of the most promising places to search for life in the Solar System. Beneath its thick icy crust lies a global ocean containing more water than all of Earth's oceans combined. However, new research suggests that this ocean may be far more isolated from the surface than previously thought.

Why Europa is so intriguing

Voyager and Galileo missions in the last century revealed the existence of an extensive water ocean beneath Europa's icy shell. NASA's Europa Clipper spacecraft is now on its way to the moon, where it will perform 49 close flybys. Scientists hope to detect water plumes or warm surface regions that could provide direct information about the composition of the hidden ocean.

New calculations change the picture

A study led by planetary scientist Lujendra Ojha of Rutgers University has shown that Europa's icy shell poses a far more formidable barrier than previously believed. Computer models demonstrated that water rising from the ocean through cracks moves turbulently, rapidly loses heat, and freezes – often within hours, never reaching the surface layers.

"There is an icy shell, there is water beneath it, and there are many assumptions about how that water can rise from depth without freezing on the way. That is precisely what we think we have refuted," Ojha noted.

Instead of flowing smoothly, the water mixes chaotically as it comes into contact with the cold walls of the fractures. It supercools, forms tiny ice crystals (frazil ice), which quickly clog the channel and block further ascent.

What this means for future missions

If Europa Clipper or the European JUICE spacecraft detect shallow water pockets or similar structures, they are likely to have formed from local melting within the icy shell itself, rather than from direct upwelling from the deep ocean.

"This will help future missions correctly interpret what they find and better understand where to look for signs of potential habitability," Ojha emphasised.

The study was published on 23 July in the journal Nature Astronomy.

In brief

New computer models show that water from Europa's subsurface ocean can hardly reach the surface: it freezes rapidly in cracks due to turbulent motion and heat loss. Any liquid pockets detected near the surface are most likely formed locally within the ice shell. This complicates the search for signs of life but helps more accurately interpret data from the upcoming Europa Clipper and JUICE missions. The work was published in the journal Nature Astronomy.