Europa is the kind of place that makes space scientists giddy: an icy moon with strong evidence for a global ocean, chemistry that looks interesting,
and surface geology that screams “something is happening down there.” It’s also the kind of place that may greet your expensive robot with
a field of jagged ice bladesbecause apparently Europa didn’t get the memo about being a welcoming tourist destination.
Over the last several years, researchers have argued that Europa’s equatorial regions could host “penitentes”:
sharp, closely spaced spikes of ice that, on Earth, can turn a walk into a shin-destroying obstacle course.
On Europa, the stakes are higher than bruises. A lander that touches down in the wrong neighborhood could tilt, snag a leg, or find itself trying to
“park” on what amounts to frozen spears.
This article breaks down what these ice spikes are, why anyone thinks they might exist on Europa, what could make them so dangerous,
and how future missions can reduce the riskwithout needing to bring a cosmic machete.
Europa: The ocean world with a not-so-friendly welcome mat
Europa is one of Jupiter’s most fascinating moons because it’s widely considered an “ocean world”: a body with liquid water beneath an icy crust.
That combinationwater, energy sources, and chemistrymakes it a prime candidate in the hunt for environments that could support life.
So naturally, humans started planning ways to study it up close.
The catch is that “up close” includes landing. And landing on Europa isn’t like landing on a calm, flat parking lot. Even the best images from past missions
capture only relatively large features, leaving the truly lander-sized hazards (think meters, not miles) frustratingly uncertain.
Europa’s surface is a tapestry of ridges, bands, disrupted “chaos” regions, and cracksbeautiful, dynamic, and potentially awful for landing stability.
Meet the “ice spikes”: penitentes, Europa edition
What penitentes look like on Earth (and why they’re so weird)
On Earth, penitentes form in specific conditionsoften high altitude, dry air, and strong sunlight. Instead of melting evenly, the snow and ice can
ablate unevenly, with sunlight concentrating in small depressions. Over time, tiny pits deepen, the peaks stand proud, and the landscape evolves into
rows of blades that can reach several feet (and sometimes meters) high.
Imagine the sun acting like a mischievous sculptor with a laser pointer: wherever the light bounces and concentrates, it removes more ice.
The result is a “forest” of icy fins that can be tightly packed and sharply angled. Great if you’re filming an alien movie.
Less great if you’re trying to place four landing feet down gently and evenly.
Why scientists suspect Europa might have them
The Europa spike hypothesis gained attention because Europa is cold, dry, and has essentially no atmosphereconditions where sublimation
(solid ice turning directly into vapor) can dominate how ice erodes. Some researchers modeled how sunlight and surface processes might shape Europa’s
equatorial ice over long periods, and concluded that spikes could form where sublimation wins the tug-of-war against smoothing processes.
The headline-grabbing idea: in parts of Europa’s equatorial zone, penitentes might grow to around 15 meters (about 50 feet) tall,
with spacing on the order of several metersdense enough to turn a landing ellipse into a game of “don’t touch the spikes.”
Importantly, this is not based on direct images of Europa showing individual blades. It’s an inference built from modeling and from hints in older data
(like radar and thermal measurements) that could be consistent with a rough, jagged surface.
Why ice spikes are a lander’s worst kind of “rough terrain”
Landing stability is all about geometry and bad surprises
A typical lander wants a surface that’s reasonably flat at the scale of its landing legs.
If the ground tilts too much, one foot touches first, the lander rocks, and you get a cascade of problems:
higher loads on one leg, slipping, tipping, or bouncing in low gravity where “bounce” can turn into “please stop drifting sideways.”
Now swap “rocky slope” for “knife-blade ice.” Spikes introduce hazards that aren’t just uneventhey’re pointy and potentially load-bearing in
all the wrong ways:
- Foot placement failure: A landing pad might come down on a ridge crest instead of a stable flat patch.
- Straddling voids: Legs could land on separate spikes with gaps between them, creating awkward leverage and instability.
- Tip-over risk: Closely spaced blades can force a lander into a tilted stance from the moment it touches down.
- Structural damage: Sharp ice could gouge footpads, snag deployment mechanisms, or concentrate forces where you don’t want them.
- Surface interaction surprises: Thruster plumes, touchdown vibrations, or even minor sliding could break brittle spikes and shift support.
Why “just land somewhere else” isn’t always easy
A mission doesn’t pick a landing site by spinning a globe and pointing. Engineers care about sunlight, communications geometry,
terrain safety, and where the fuel cost is lowest for getting the spacecraft onto a descent path.
If a region is “cheaper” to reachlike certain equatorial zonesthere’s pressure to land there unless hazards force a rethink.
Add Europa’s harsh radiation environment to the mix and you get a complicated trade:
you want a place that is scientifically exciting, operationally possible, and doesn’t subject your robot to immediate doom by ice kebab.
Are the spikes real? The debate is part of the story
The case for spikes: models + hints, not a Europa selfie
Several popular explanations of the spike hypothesis emphasize a key point: Europa’s best imaging to date can’t resolve meter-scale spikes directly.
So the argument leans on physics-based modeling and indirect clueslike how roughness might influence radar reflections and how surface texture can
affect thermal behavior.
In other words: the “ice spikes” aren’t confirmed obstacles; they’re plausible hazards that mission planners can’t ignore because ignoring plausible hazards
is how spacecraft become very expensive modern art.
The case against: Europa is not the Andes, and physics can be picky
Other researchers have pushed back, noting that Earth’s penitentes often involve specific environmental ingredients that Europa doesn’t share.
Europa’s lack of atmosphere, different ice chemistry (salts and other contaminants), and extreme cold complicate the simple analogy.
Some lab efforts and theoretical arguments suggest giant penitentes may be difficultor even unlikelyto form under Europa-like conditions.
This isn’t a “somebody is wrong, end of story” situation. It’s more like a cosmic courtroom drama where both sides have receipts,
and the judge is a future spacecraft with better data.
How Europa Clipper can help de-risk a future landing
The good news is that we are no longer stuck with only 1990s-era imagery and educated guessing.
NASA’s Europa Clipper mission is designed to study Europa through dozens of close flybys, collecting a layered view of surface geology,
composition, temperature, and subsurface structure.
What Clipper can measure that matters for spikes
If Europa’s equator really is bristling with roughness, Clipper’s instrument suite is built to detect the clues that roughness leaves behind.
That includes:
- High-resolution imaging: Better maps of terrain types, fractures, ridges, and candidate smooth zones.
- Thermal mapping: Surface temperature patterns that may hint at texture, porosity, and roughness.
- Radar sounding: Tools that probe the ice shell and may also help characterize near-surface structure and interfaces.
- Composition mapping: Identifying materials that may correlate with certain surface processes or terrain styles.
Even with improved data, there’s a reality check: a flyby mission can dramatically reduce uncertainty, but it may still not “see” every meter-scale hazard
everywhere. A future lander will likely need conservative safety margins, plus landing site selection strategies that assume the surface can be rude.
Designing a lander that doesn’t get bullied by ice
Engineering strategies for spiky worlds
If spikes are common in targeted regions, designers have optionsnone of them trivial, but all of them better than hoping for the best.
Concepts that come up repeatedly in landing-system design include:
- Wider stance and smarter legs: A broader footprint reduces tip-over risk, while compliant legs can absorb uneven contact.
- More forgiving footpads: Pads that spread load, handle small protrusions, or include crushable structures to adapt on contact.
- Hazard detection and avoidance: Terrain-relative navigation and last-second divert capability to avoid the worst patches.
- Touchdown tolerance testing: Drop tests and “Europa-yard” simulations that treat jagged terrain as the default, not the exception.
- Site selection with safety layers: Prioritizing zones that look smoother while still offering access to fresh materials.
Science vs. safety: the landing-site tug-of-war
Astrobiology doesn’t get excited about “perfectly flat, boring ice.” It gets excited about places where the subsurface may have communicated with the surface:
regions with disrupted blocks, recent-looking fractures, and terrain that suggests material movement.
Unfortunately, “geologically interesting” can overlap with “mechanically terrifying.”
That’s why the spike question matters beyond clickbait. If certain latitudes or terrain types are more likely to be spiky,
mission planners may need to redesign the landing strategyor adjust expectations about where a lander can safely go.
Earth analogs: practicing for Europa without the radiation or the 400-million-mile commute
One of the most practical ways to prepare for Europa is to study similar processes in places we can actually visit.
On Earth, penitentes and related ice textures provide a living lab for understanding how sunlight and sublimation carve sharp terrain.
Even when the exact physics doesn’t translate perfectly, analog studies are invaluable for building intuition and validating models.
Add vacuum chambers, cold labs, and terrain testbeds, and engineers can stress-test lander designs against “worst plausible Europa”
instead of “optimistic Europa where everything is flat and friendly.”
Conclusion: spikes are a warning label, not a mission-stopper
The idea of menacing ice spikes on Europa sits right at the intersection of science, engineering, and healthy paranoia.
The spikes might exist at dangerous scales, they might be smaller than feared, or they might be rareclustered in certain zones rather than everywhere.
The critical point is that a future lander can’t afford to be surprised.
With better reconnaissance from Europa Clipper and continued work in modeling, lab experiments, and landing simulations,
the “ice spike problem” becomes manageable: a design constraint, not a dealbreaker.
Europa may still be the solar system’s most intriguing ocean worldjust one that demands we look before we leap.
Bonus: Experiences and Lessons From Ice, Labs, and Landing Sims (Extended Add-On)
Ask anyone who has ever walked through real penitentes on Earth, and you’ll get the same vibe: wonder, discomfort, and an immediate desire to watch
your step. Researchers in high-altitude regions describe penitente fields as both mesmerizing and maddeningblade after blade, aligned in patterns,
casting sharp shadows, and turning what looks like “snow” into something closer to a frozen maze. You don’t glide across it. You negotiate it.
That lived reality is why Europa’s hypothetical spikes trigger such strong reactions from mission designers: if a human has trouble crossing them at a
walking pace, a lander with a fixed footprint has even less room for error.
The engineering “experience” side is just as vividonly it happens indoors, under cranes, in test yards, and inside vacuum chambers.
Landing teams don’t simply read papers and nod thoughtfully; they build hardware, then try to break it in controlled ways.
One common strategy is to suspend a lander prototype so it behaves as if it’s in lower gravity, then run touchdown rehearsals onto deliberately nasty terrain:
uneven blocks, ridges, holes, and sharp protrusions meant to mimic the most pessimistic interpretations of Europa’s surface.
The point isn’t to prove a perfect landing is easy. The point is to discover how things fail: which leg slips first, how load shifts across struts,
how much tilt the system tolerates before it becomes a topple machine.
The funniest partif you’re into “spacecraft testing humor,” which is a niche but proud communityis that some test articles get names.
Engineers have used scale models and dummy landers to run repeated drop-and-contact tests, swapping foot designs and leg geometries like shoe choices
before a marathon. Each iteration answers a practical question: Does a wider footpad help, or does it catch and snag?
Do you want stiffness (predictability) or compliance (adaptability)? How do you keep a lander stable if it touches down on two high points and one low one?
Europa’s low gravity makes it weirderbecause the lander doesn’t “settle” the same way it would on Earth. Small bounces can last longer,
and a tiny sideways slide can become a bigger positional change than you’d expect.
Meanwhile, the science side of “experience” often looks like detective work with imperfect evidence. Europa’s older images show large-scale fractures and
chaos blocks, but the hazards that matter for landing live at scales that were, historically, below the pixel size.
So scientists learn to think in proxies: thermal behavior that hints at roughness, radar echoes that suggest texture, and model predictions that tie surface
evolution to latitude and sunlight geometry. It’s the same mental muscle used in weather forecastingbuild a physical model, test it against what you can
observe, then refine it until it stops embarrassing you.
The most practical lesson from all of these experiences is not “Europa is impossible.” It’s that Europa demands humility.
The surface might include smooth patches large enough to land safelyespecially away from the most rugged terrainsbut the mission must be built under the
assumption that hazards exist until proven otherwise. That mindset changes everything: it pushes reconnaissance to the top of the priority list, encourages
landing systems that can adapt on contact, and favors site-selection strategies that balance safety with science payoff.
If penitentes are real and large, then avoiding them may mean choosing different latitudes, different terrains, or different landing architectures.
If penitentes are rare or small, then the same tools used to prepare for them still pay offbecause Europa will still have cracks, blocks, slopes,
and surprises.
In short, the “experience” of preparing for Europa is the experience of turning uncertainty into engineering requirements.
And if that sounds like a buzzkill, remember: this is how we get from “wild theory” to “robot safely standing on alien ice,”
sending back the kind of data that makes the whole solar system feel a little more reachable.
