An expensive lander sinking into frozen depths after years of travel
Humanity's ambition to search for life on the ocean moons of Jupiter and Saturn has long rested on the assumption that we know what we would be landing on. A new discovery from a vacuum chamber in the United Kingdom quietly unsettles that assumption: the cryovolcanic surfaces of Europa and Enceladus produce a fragile, porous ice — layered like a croissant, deep as a city building — that could swallow a lander whole. Before the first spacecraft ever touches those distant shores, engineers must now reimagine the very act of arrival.
- Experiments recreating the extreme low-pressure conditions of Europa and Enceladus revealed that cryovolcanic eruptions produce brittle, air-filled ice structures that bear almost no resemblance to what mission planners had assumed.
- On Enceladus, these porous layers can reach 20 meters deep — enough to engulf an expensive lander that has spent years crossing the solar system, sinking it before it can transmit a single reading.
- NASA's own Europa Clipper scientist called the finding a serious engineering problem, acknowledging that the landing mechanisms currently envisioned for these worlds may need to be fundamentally redesigned.
- The window for redesign is narrowing fast: Europa Clipper arrives in 2030 and ESA's JUICE in 2031, both paving the way for surface landers whose blueprints may now need to be redrawn from scratch.
- The research team plans follow-up experiments using flowing water to simulate active eruptions, racing to understand not just how this ice forms, but how it behaves — knowledge that could determine whether humanity's first contact with an alien ocean is a triumph or a disappearance.
Europa and Enceladus — the ice-shelled moons of Jupiter and Saturn — have long been considered the solar system's most compelling addresses in the search for extraterrestrial life. Liquid oceans are thought to slumber beneath their frozen surfaces, and space agencies worldwide have made them priority destinations. But a new discovery is forcing a reckoning with a question nobody had fully asked: what exactly will a spacecraft land on?
The answer, it turns out, may be something disturbingly fragile. A team led by geophysicist Vojtěch Patočka at Charles University in Prague conducted experiments inside a large vacuum chamber at the Open University in the UK, recreating the extreme low-pressure, low-temperature conditions of these moons. When they froze low-salinity water under those conditions, the result looked less like solid ice and more like a croissant — flaky, layered, riddled with air pockets. They named it "fluffy ice," and it forms through cryovolcanic eruptions: geysers of water vapor that shoot upward and refreeze almost instantly in the vacuum of space.
The freezing unfolds in three stages: violent boiling creates a crusty surface crust as vapor escapes, those vapor pockets then freeze and trap air inside, and finally a denser layer forms below. On Europa, these brittle sheets grow to about 20 centimeters. On Enceladus, they can reach 20 meters — the height of a six-story building — more than enough to swallow a lander that has traveled years through deep space.
Patočka himself admitted the research "seems like the kind of thing that would have been done already." It hadn't been. Ingrid Daubar, a planetary scientist on NASA's Europa Clipper mission, told Science the findings would "definitely pose some serious engineering issues" and force a reimagining of landing mechanisms. Current lander designs were built around different assumptions about surface terrain.
The urgency is real. NASA's Europa Clipper reaches Jupiter in 2030, followed by ESA's JUICE mission in 2031. Neither will land — both are orbiters — but they are laying the groundwork for future surface missions that will need to touch down and, eventually, drill toward the oceans below. Those missions are still years away, but the time to redesign them is not unlimited.
Patočka's team plans to return to the vacuum chamber to run new experiments with flowing water, better mimicking the dynamics of actual eruptions. The stakes are straightforward: understand how this ice behaves, or risk watching billions of dollars in spacecraft vanish silently into the frozen depths of another world.
Europa and Enceladus, the ice-locked moons orbiting Jupiter and Saturn, have long captivated planetary scientists as the most promising places in our solar system to search for life beyond Earth. Beneath their frozen crusts lie oceans of liquid water—at least, that's what researchers believe—and that possibility has made them priority targets for space agencies worldwide. But a new discovery is forcing engineers to reconsider how they'll actually land spacecraft on these distant worlds. The problem is a kind of ice that forms in ways nobody fully anticipated until now.
The culprit is what scientists are calling "fluffy ice," a brittle, porous structure that forms when water freezes under the extreme conditions found on these moons. The ice gets its texture from cryovolcanic eruptions—geysers of water vapor and other volatile materials that shoot up from beneath the surface and refreeze almost instantly in the vacuum of space. A team led by geophysicist Vojtěch Patočka at Charles University in the Czech Republic ran experiments in a massive vacuum chamber called George at the Open University in the United Kingdom to understand how this process works. They filled a fish tank with roughly 49 kilograms of low-salinity water, then dropped the temperature and pressure to match conditions on Europa and Enceladus. What they found was unsettling for mission planners: the ice that formed looked remarkably like a croissant, all flaky layers and air pockets.
The freezing happens in three distinct stages. First, the lack of atmospheric pressure causes the water to boil violently, creating a crusty surface layer while vapor escapes upward. Then those vapor pockets freeze solid too, trapping air inside. Finally, a denser, more transparent layer of ice forms at the bottom. The result is a structure so fragile and porous that it could swallow a lander whole. On Europa, these brittle sheets form about 20 centimeters thick. On Enceladus, they can grow to 20 meters—roughly the height of a six-story building. That's enough to trap and sink an expensive spacecraft that has spent years traveling through space only to punch through the surface like a stone through thin ice.
This wasn't a problem anyone had seriously studied before. Patočka acknowledged to Science that the research "seems like the kind of thing that would have been done already," but it hadn't. The implications are significant enough that Ingrid Daubar, a planetary scientist on NASA's Europa Clipper mission, told Science the discovery would "definitely pose some serious engineering issues" and force researchers to "re-envision the types of landing mechanisms we thought might work on Europa." The current generation of landers was designed with different terrain in mind. Engineers will now have to figure out how to either avoid these porous ice zones entirely or design landing gear that won't collapse under the weight of the spacecraft.
The timing of this discovery is both fortunate and urgent. NASA's Europa Clipper is scheduled to arrive at Jupiter in 2030, while the European Space Agency's JUICE mission will reach the same destination in 2031. Neither of these spacecraft will actually land on the moons—they're orbiters designed to study the moons from above—but they're paving the way for future missions that will. Both NASA and ESA, working with partners like Japan's space agency, are already planning the next phase of exploration: actual landers that will touch down on the surface and, ideally, drill through the ice to reach the oceans beneath. Those missions are still years away, but the window to redesign them is closing.
Patočka's team isn't done investigating. They plan to return to the George chamber soon to run new experiments, this time using flowing water to better simulate the conditions of actual cryovolcanic eruptions on these moons. The goal is to understand not just how the ice forms, but how it behaves when water is actively moving through it. That knowledge could be the difference between a successful landing and a catastrophic failure—between humanity finally reaching an alien ocean and watching billions of dollars in spacecraft disappear into the frozen depths.
Citas Notables
The highly porous and fragile layers that we observe could be several meters thick on the small icy worlds, which is enough to endanger a landed mission.— Vojtěch Patočka, geophysicist at Charles University
This type of porous, fragile ice would definitely pose some serious engineering issues, and researchers would have to re-envision the types of landing mechanisms we thought might work on Europa.— Ingrid Daubar, planetary scientist on NASA's Europa Clipper mission
La Conversación del Hearth Otra perspectiva de la historia
So these moons have oceans beneath the ice. Why does the surface ice matter so much if we're trying to reach the water underneath?
Because you have to land on the surface first. You can't just materialize at the ocean. A lander comes down, touches the ice, and if that ice is fragile enough, the spacecraft sinks. You've spent years getting there. You can't afford that.
But couldn't engineers just design stronger landing gear? Bigger feet, more support?
Maybe, but the ice layers can be 20 meters thick on Enceladus. That's not a thin crust you can punch through. It's more like landing on a field of frozen meringue. The more weight you put on it, the more it collapses. You need to either find solid ground or rethink the whole approach.
How did scientists not know about this until now?
They knew cryovolcanism happened on these moons. They just didn't run the experiment to see what kind of ice it actually creates. It took someone asking the right question and having access to a vacuum chamber that could simulate the conditions. Sometimes the obvious thing is the thing nobody's done yet.
What happens next? Do these missions get delayed?
The orbiters arriving in 2030 and 2031 aren't affected—they don't land. But the landers that come after? Those teams are probably in meetings right now figuring out how to redesign. The research is still ongoing too. Patočka's group is running new experiments with flowing water to get even closer to what actually happens on these moons.