Jupiter’s icy moon, Europa, is a prime candidate in the search for life elsewhere in our Solar System — but landing a spacecraft on the moon may be even more difficult than we thought. Certain patches of ice on Europa could be rough and jagged, resembling sharp blades, according to a new modeling. And that may make it hard for future probes to touch down gently on the surface.

It’s possible that conditions in areas around Europa’s equator may be just right to form what are known as “penitentes.” These are unique ice formations found here on Earth in places like the Andes Mountains. Penitentes form on Earth when super-cold ice sits in direct sunlight for long periods of time, causing patches in the ice to turn directly from a solid to a gas. In a new study, published today in Nature Geoscience, researchers found that the exact conditions needed to create this phenomena are present on parts of Europa too.

Scientists still hope to confirm the finding with visual evidence

Scientists still hope to confirm the finding with visual evidence of penitentes on Europa. But the new model is a key piece of information that could help inform NASA’s future missions. Right now, the space agency is working on two different missions to the moon. The first, Europa Clipper, is slated to launch sometime around 2022 and will send a spacecraft to fly by Europa and possibly zoom through the world’s plumes — suspected geysers that spew water from a vast ocean below the moon’s icy crust. In the meantime, NASA is in the very early stages of designing a lander that could also travel to Europa someday, touch down on the surface, and then drill into the ice. That way, it could potentially sample the unseen water below.

But if parts of the surface are truly shaped like blades, it would be extremely hazardous for a conventional lander. This new research could help NASA decide which areas to avoid when considering landing spots on Europa. And it’s possible that the upcoming Europa Clipper mission will get even more detailed images of the moon’s surface, to confirm if these formations are actually there. “We’re really hoping that the Clipper mission will tell us one way or the other,” Daniel Hobley, a geologist and planetary scientist at Cardiff University in the UK, as well as lead author on the study, tells The Verge. “We should be able to take pictures of good enough quality to prove it.”

The impetus to look into this came from a simple question: “What would it be like to land on Europa?” Up-close images of the moon, taken in the 1990s by NASA’s old Jupiter probe, Galileo, revealed that the ice world is covered with reddish grooves and ridges. These bands are super wide, but it’s unclear what the terrain is like inside and around these troughs. Is it smooth and slick or jagged and coarse?

To figure this out, Hobley and his team decided to look to Earth as a guide. “On Earth it’s pretty unusual to find completely flat ice,” he says. “Especially if it’s left out in the Sun, that ice will be roughening it up. It won’t just sit there as a beautiful fresh surface of snow. It will have texture on it.” Given this kind of roughness happens on Earth, Hobley wondered if it was something we needed to worry about on Europa, as well.

“On Earth it’s pretty unusual to find completely flat ice.”

After researching different types of ice formations, the researchers focused in on penitentes. These jagged formations are rare on Earth, as they require extremely specific conditions to form. Pentientes typically emerge in areas of thin atmosphere, where the air is very still and dry. And these places must be really, really cold, too, so the ice there doesn’t have any risk of melting. That way, when these areas are exposed to direct sunlight, the ice doesn’t turn into a liquid but immediately forms into water vapor. It’s a process known as sublimation, and it occurs when temperatures and pressures are just right so that materials skip the liquid phase of the transition process.

But it’s not enough just to have sunlight in these areas. The sunlight must remain in the same part of the sky for large periods of time, says Hobley. This causes patches of ice to erode away, forming deep pits and high spikes. And when the Sun remains in the same spot overhead, the bottoms of these pits stay illuminated and continue to deepen. This is why penitentes usually only form in South America’s Andes Mountains. At such high altitudes, the air is thin and still; plus these regions are near the equator, so during the winter, the Sun is typically in the same part of the sky for a while. “What you need is light coming straight down in winter, and it needs to not wobble around too much. And that only happens near the equator on Earth,” Hobley says.

Hobley and his team then looked for these conditions on Europa. And sure enough, it has all the right elements for penitentes to grow. “Europa is ideal for that, because it doesn’t have any air essentially,” he says. “There is no atmosphere on Europa.” Plus, temperature is not an issue. It ranges from -210 degrees to -370 degrees Fahrenheit on the moon’s surface. “It’s really cold, so you never have to worry about melting ice,” Hobley says. “You go straight from solid ice into water vapor, because there is no air.”

Europa seems to have all the right elements for penitentes to grow

Based on data gathered by NASA’s old Galileo probe, Hobley and his team estimated how much sublimation is happening on Europa, or how quickly ice is thought to turn into vapor on the moon when exposed to the Sun. Multiple things can cause ice to disappear on Europa, such as charged particles hitting the moon’s surface or small meteorites hitting the ground and ejecting material. And the team wanted to know how sublimation compared to these other processes. They found that ice seems to be turning into gas at a high rate at the equator, making it possible that penitentes are growing there. And they believe these blades could get up to 50 feet tall — about they height of a five-story building.

And this part of Europa has another thing needed for the ice blades: direct sunlight overhead. Because of how Europa orbits Jupiter, the Sun more or less stays in the same spot at the moon’s equator. “The Sun for Europa goes straight overhead at the equator every day, all day long, all years long, for forever,” says Hobley. “It traces the same arc in the sky over and over.” It’s all ideal conditions for ice blades to form at Europa’s tropics.

Of course, we don’t have photographic proof, but Hobley and his team found other signs as well. They say that the penitentes may explain some really weird radar readings and heat signatures that the Galileo probe found at Europa’s equator. That’s because the ice in this region is just structurally different from the rest of the surface.

“There are other potential answers for those results.”

It all makes for a good theory, one that Hobley has posited before. The researchers have discussed their findings with NASA, and space agency scientists agree it’s a compelling idea. However, not everyone is convinced just yet. Cynthia Phillips, NASA’s Europa project staff scientist, says it’s possible that other explanations may explain the weird readings at the equator. It’s hard to know because Galileo’s instruments weren’t strong enough to tell us for sure. “There are other potential answers for those results,” she says. “It’s just because the data that we have so far is so low-resolution that you can’t really use it to point to one particular explanation or another.”

However, answers will come soon with Europa Clipper, which will fly within 16 miles of Europa’s surface. The spacecraft also has a camera and instruments with higher resolution than Galileo had. “It will be flying over the equatorial region, which is where these features are predicted to exist,” Phillips says. “I think Europa Clipper is well-suited to see any actual evidence for these formations.”

Even if ice blades are found, it’s not a showstopper for a future lander. The new study only found these high sublimation rates occurring in a narrow band around the equator, but areas closer to the poles don’t seem to have the same conditions. “There are still lots of places on the surface of Europa that would be really interesting potential landing sites that are well outside of this band,” says Phillips. “There’s no reason to shoot for the equator over anywhere else.”</s>Shards of ice 15 metres (50ft) high could exist on the surface of Jupiter’s moon Europa, posing a threat to landing probes, scientists say.

The moon, which is covered by an ice-encrusted ocean of salty water, has a habitat that may support life.

It is high on the list of targets for future interplanetary space missions.

Any robotic spacecraft landing on the moon will have to navigate its way around lethal obstacles, a new study suggests.

A team led by scientists at the University of Cardiff predicts that shards of ice up to 50ft tall could be scattered across Europa’s surface.

Known as “penitentes”, the formations are sharp-edged blades and spikes that point towards the mid-day sun.

They form through a process of sublimation that allows ice to turn directly into water vapour without melting into a liquid first. When lumps of ice sublimate, the jagged shards are left behind.

Small one to five metre tall penitentes exist on Earth where they are restricted to high-altitude tropical and sub-tropical regions such as the Andes.

But on Europa, conditions are perfect for the formation of giant penitentes.

Dr Daniel Hobley, from the University of Cardiff’s School of Earth and Ocean Sciences, said: “The unique conditions of Europa present both exciting exploratory possibilities and potentially treacherous danger.

“The presence of sharp, blade-like structures towering to almost 15 metres high would make any potential landing mission to Europa extremely precarious.

“We hope studies like ours will help the engineers to develop innovative ways of delivering landers safely on Europa’s surface so that we can find out even more about this fascinating place, and potentially look for signs of extra-terrestrial life.”

The research is reported in the journal Nature Geoscience.- Press Association</s>Jupiter’s moon Europa, with its subsurface ocean, may have what it takes to foster alien life. A mission to this icy moon is on the wishlist of many astronomers, but new research suggests it won’t be easy to land spacecraft there: Its surface seems to be littered with icy spikes, the tallest of which measure five stories high.

New research published this week in Nature Geoscience suggests Europa’s surface is covered with tall, sharp-edged icy blades known as penitentes (pronounced PEN-E-TENT-EES). If you’re a geologist, that’s a super cool discovery; but if you’re an astrobiologist, it’s a major bummer. That’s because Europa, like Saturn’s moon Enceladus, features a vast subsurface ocean that could serve as a potential habitat for extraterrestrial life. The presence of the penitentes—some reaching 50 feet into the sky—could “pose a hazard to a future lander on Europa,” the researchers write in the new study.

Penitentes are composed of snow and ice, and they arise through sublimation—a chemical process in which ice turns directly into water vapor without melting into a liquid beforehand. The remnants of this process are the penitentes themselves, which always point towards the midday sun. To form, these icy spikes require bright sustained sunlight, and also cold, dry, still air.

We’ve got penitentes here on Earth, but they’re only found in high-altitude regions near the tropics, such as the Andes, and they range in size from about 3 to 16 feet. The conditions on Europa are considerably better for penitente formation, as the authors of the new study, led by Daniel Hobley from Cardiff University, point out. Those conditions include a surface covered in ice, ideal temperatures, and other environmental factors to support sublimation, and a consistent angle of incoming sunlight.



To date, the resolution of photographs taken of Europa’s surface hasn’t been fine enough to show the penitentes, so they remain hypothetical. That said, computer models run by Hobley and his colleagues strongly support their presence. Using pre-existing observational data, the researchers calculated the sublimation rates at various points on the moon’s surface, allowing them to estimate both the size and distribution of the penitentes. According to the models, Europa’s penitentes are capable of growing to around 50 feet tall (15 meters), with a spacing of about 25 feet (7.5 meters) between each one. The icy spikes are likely to be more common around Europa’s equatorial regions, according to the study.

If there is some good news in all of this, it’s that a future mission to Europa might avoid the equatorial regions anyway. Research published this past July suggests scientists on the hunt for life will have a better chance of finding potential biosignatures in Europa’s younger ice and in lower-radiation locations. This type of ice, which is less than 10 million years old, should exist in the mid-to-high latitudes, where the moon points away from Jupiter. And as the new study shows, these areas are less likely to host those hazardous icy spikes.

Further observations are needed to definitively prove that Europa’s surface is covered in the penitentes, but that could come soon. NASA’s Europa Clipper spacecraft is scheduled to launch at some point between 2022 and 2025. This orbital probe is packed with instruments, and it’ll come to as close as 16 miles (25 kilometers) to Europa’s surface. Excitingly, the Europa Clipper mission may be a forerunner to a landing mission on the Jovian moon, in which a probe would drill through the icy surface and plunge into the dark ocean beneath.

The technical requirements of such a mission boggle the mind, and now, with the news that Europa’s surface may contain vast fields of penitentes, there’s an added complication. But as it’s often said, space is hard. And as we continue to push the envelope, it’ll only continue to get harder.</s>Penitentes ice formations at the southern end of the Chajnantor plain in Chile in 2005. Similar formations likely are found on the surface of Europa, a new study suggests.

If you're planning a trip to Jupiter's moon Europa, be prepared for a rough landing.

In a study released Monday, scientists say they've found evidence of huge, jagged "ice spikes," some 50 feet tall, on the moon's surface. They spikes would "pose a hazard to any future space mission landing on the moon," according to the study.

The spikes could be similar to "penitentes" down here on Earth, like those found in the higher elevations of South America.

"In extreme cold and dry conditions on Earth, such as those encountered in the Andes, the sun’s rays can cause parts of the ice and snow to undergo sublimation – becoming water vapor without melting first," the study said. This process leaves behind distinctive, blade-like formations called penitentes.

Although scientists have not seen the spikes there, a similar process likely occurs on Europa, the study suggests.

Evidence of penitentes has also been seen on Pluto, suggesting that such jagged terrains may be common on icy worlds – including Europa.

On Europa, these spikes could be as close as about 20 feet apart, creating a "treacherous terrain" for potential landing craft.

Due in part to its salt water ocean, Europa is one of the more promising candidates for extraterrestrial life in our solar system, NASA said, so the moon has been targeted as destination for a future space mission.

"Beneath the icy surface of Europa is perhaps the most promising place to look for present-day environments suitable for life," NASA said. Scheduled to launch in the 2020s, the Europa Clipper mission would arrive at Jupiter several years later and try to see whether the icy moon could harbor conditions suitable for life.

Led by Daniel Hobley, a Cardiff University scientist, Monday's study was published in the peer-reviewed British journal Nature Geoscience.

This image shows two views of Europa. The left image shows the approximate natural color appearance of Europa. The image on the right is a false-color composite version that enhance color differences in the predominantly water-ice crust of Europa.</s>Few moons in the Solar System are as intriguing as Jupiter's moon Europa. A global ocean of salt water almost certainly surrounds the moon - and it holds more water than any ocean on Earth.

Above this immense sea, where surface temperatures dip to minus 300 degrees Fahrenheit (-184 degrees Celsius), a crust of water ice forms a shell.

Astronomers predict that Jupiter, which bombards the moon with intense radiation, causes the entire moon to groan with gravity's tug. Europa's liquid water is a tempting target for future missions looking for possible alien microbes.

But before a future lander can search for microscopic ET, the probe might have to contend with a forest of tall, jagged ice spikes. So argues a team of planetary scientists and geomorphologists Monday in the journal Nature Geoscience.

Their research suggests Europa is an icy hedgehog world, covered in ice formations rarely found on Earth.

On our planet, ice takes several forms, as varied as needle ice, rime, parking lot slush and more exotic lumps. But because Europa's surface is "incredibly cold," said Daniel Hobley, a geomorphologist at Cardiff University in the UK, an author of the study, ice will not melt and refreeze.

Instead, stranger things happen. Ice is not perfectly flat - it's made of little crystals.

"Each of those crystals has potential to lens light," Hobley said, channeling or refracting light down into ice. Over millions of years, energized by the sun's radiation, Europa's ice transforms into gas.

Sunlight alone would not be enough to form huge ice blades. Europa is tidally locked with Jupiter, which means its orbit around Jupiter matches its own rotation.

Put another way, the same face of Europa always faces Jupiter. That also means that the angle of the sun is constant in Europa's sky, Hobley said. The moon has no seasons.

"It's just day-night, day-night, day-night," Hobley said, year after Jovian year.

Hobley and his colleagues considered where on Earth might approximate Europa. They landed on the Andes, the South American mountain range that stretches from Venezuela to Argentina.

At the highest peaks, the Andes has ice - and, in winter, the ice stays too cold to melt. What's more, near the equator, the sun's angle is high and constant, just like it is over Europa's middle.

In the Andes, Hobley and his co-authors knew, an ice formation called penitentes takes shape.

Penitentes are named after an Easter religious festival, practiced by some Spanish-speaking Christians, in which monks wear pointed white hats (the "penitent," hence, penitentes).

Charles Darwin, who made some of the first scientific observations of penitentes in the 1830s, imagined the wind created the ice spikes.

But in 2001, University of Colorado at Boulder physicist Meredith Betterton grew penitentes in a lab via the solid-to-gas process.

At mountain tops, the sun's light carves pits deep in the ice, leaving behind blades twice as tall as they are wide. Penitentes do not form at high latitudes because the sun is too low in the sky in winter; the ice crystals do not funnel the light so sharply downward.

The bottom of these triangular cavities get hotter, and the sides stay cool. On Europa, they would grow "crazy, crazy slow," Hobley said, at about a foot every million years.

But because Europa's surface has been largely unchanged for 50 million years, "they've got a nice long time to do it." Europa's penitentes, the authors calculated, could be almost 50 feet long.

"They have a pretty solid case," said astronomer William Grundy, an expert on icy Solar System objects at Arizona's Lowell Observatory who was not involved with this work.

To be clear, though, this work is a prediction. The conditions are right, but a future observation is required to confirm the penitentes.

Grundy noted that the spatial resolution of Europa images, taken by uncrewed spacecraft like Galileo, are just slightly too fuzzy to make out these features. "Who knows what dragons lurk down there?"

Supporting this argument are radar and temperature imagery.

Europa's midsection absorbs radar, in the way that resembles the "eggcup-shaped sound baffles on recording walls," Hobley said. Which happens to be the shape of penitentes.

What's more, blades of methane ice exist on Pluto. It's also possible, Grundy speculated, that the moons of Uranus - much farther from the sun than Europa - could have bladed terrain of solid carbon dioxide.

As for a landing hazard, the danger is not that a spike will impale a robot. But a probe could very well be lost in one of the pits between the blades, Hobley warned.

Space probes that have attempted landings on asteroids and comets have flipped like flailing beetles or gotten wedged in cracks.

It's not an insurmountable problem, just one of engineering and astronomy. Future landers could aim at a younger region of Europa's surface, where the ice has not had time to form such deep pits.

Higher latitudes, too, should not be covered so thickly in ice blades.

There are two planned orbiter missions to examine Europa: NASA is preparing to launch the Europa Clipper at some point in the 2020s; the European Space Agency's Jupiter Icy moons Explorer (JUICE), is planned to launch in 2022.

Their sensors could confirm or reject the penitente prediction.

Even if Europa's ice blades are too threatening for a lander, a spacecraft might not have to land on Europa to test the hidden ocean. Strong evidence indicates the moon spits plumes of water into space, which an orbiter could swoop up.

This article was originally published by The Washington Post.</s>If you're planning a trip to Jupiter's moon Europa, be prepared for a rough landing.

In a study released Monday, scientists say they've found evidence of huge, jagged "ice spikes," some 50 feet tall, on the moon's surface. They spikes would "pose a hazard to any future space mission landing on the moon," according to the study.

The spikes could be similar to "penitentes" down here on Earth, like those found in the higher elevations of South America.

"In extreme cold and dry conditions on Earth, such as those encountered in the Andes, the sun’s rays can cause parts of the ice and snow to undergo sublimation – becoming water vapor without melting first," the study said. This process leaves behind distinctive, blade-like formations called penitentes.

Although scientists have not seen the spikes there, a similar process likely occurs on Europa, the study suggests.

Evidence of penitentes has also been seen on Pluto, suggesting that such jagged terrains may be common on icy worlds – including Europa.

On Europa, these spikes could be as close as about 20 feet apart, creating a "treacherous terrain" for potential landing craft.

Due in part to its salt water ocean, Europa is one of the more promising candidates for extraterrestrial life in our solar system, NASA said, so the moon has been targeted as destination for a future space mission.

"Beneath the icy surface of Europa is perhaps the most promising place to look for present-day environments suitable for life," NASA said. Scheduled to launch in the 2020s, the Europa Clipper mission would arrive at Jupiter several years later and try to see whether the icy moon could harbor conditions suitable for life.

Led by Daniel Hobley, a Cardiff University scientist, Monday's study was published in the peer-reviewed British journal Nature Geoscience.</s>Exploring the tropics of Jupiter's ocean moon Europa would be no walk on the beach.

Equatorial regions of the potentially life-supporting Europa, which harbors a huge ocean of salty liquid water beneath its icy shell, are probably studded with blades of ice up to 50 feet (15 meters) tall, a new study suggests.

This finding should be of interest to NASA, which is developing a lander mission that will hunt for signs of life on the 1,900-mile-wide (3,100 kilometers) satellite. [Photos: Europa, Mysterious Icy Moon of Jupiter]

"Clearly, the paper suggests very strongly that the tropics of Europa are going to be spiky, and it would be unwise to plan to land there without a specially adapted lander," study lead author Dan Hobley, a lecturer in the School of Earth and Ocean Sciences at Cardiff University in Wales, told Space.com via email. "It would probably be safer to land further away from the equator!"

The driving force behind penitente formation is sublimation, the transition of a material directly from solid to gas form. An initially smooth snowpack sublimates at different rates in different spots, causing small pits to form in some places. Sunlight bounces around in these pits, boosting sublimation further in the depths and eventually creating fields of spiky ice towers.

There's no reason to believe this process is restricted to our planet. Indeed, scientists think the "bladed terrain" spotted on Pluto by NASA's New Horizons spacecraft likely consists of penitentes carved into methane ice.

Europa would seem to a good bet for penitente gardens as well; after all, it's a cold, dry, virtually air-free world that's entirely covered in ice. So Hobley and his colleagues calculated sublimation rates around the surface of the Jupiter moon and then compared those with the rates of other erosional processes. Those processes include bombardment by meteoroids and charged particles from Jupiter's powerful radiation belts.

The researchers found sublimation to be the dominant factor on equatorial Europa, the regions within 23 degrees of the moon's equator. And sublimation has likely carved penitentes into the ice there, the study team determined.

These are some serious putative penitentes, too: Some fields could feature towers up to 50 feet (15 m) tall, spaced about 23 feet (7 m) apart, the scientists found. Here on Earth, penitente heights typically range from 3 to 16 feet (1 to 5 m).

The size difference "is basically a factor of time," Hobley said. "The Europa penitentes grow much (MUCH!) slower than the Earth examples, but on Earth they might be restricted to a season or maybe two until they melt in summer or get covered in more snow, but on Europa, they are sat out in the sun growing for 50 million years."

There's some observational support for the existence of Europa penitentes as well, the researchers reported. For example, radar waves beamed at Europa from big Earth-based dishes such as Puerto Rico's Arecibo Observatory show signs of bouncing off multiple surfaces on the moon — a result that Hobley described as "really weird."

"People have tried to explain this before, but those explanations have come off (in my opinion) as pretty ad hoc," he said. "We haven't explicitly modeled it but are fairly sure that penitentes would do the trick — a lot of safety reflectors on cars, bikes, etc. work on the same principle of bouncing light between two sides of a cleft and firing it back out."

We could get a look at the putative Europa penitentes soon, if all goes according to plan. In the early to mid-2020s, NASA aims to launch a $2 billion mission called Europa Clipper, which will orbit Jupiter but study the ocean moon up close over dozens of flybys.

Clipper will assess the habitability of Europa's ocean and also scout out potential touchdown sites for the lander, which will seek out signs of life that have bubbled up to the surface, or the very near subsurface, from the dark depths.

Scientists think there's a fair amount of interaction between Europa's surface and subsurface. For example, the moon's crust may harbor plates of ice, some of which dive beneath others in alien tectonic activity.

The new paper was published today (Oct. 8) in the journal Nature Geoscience.</s>If you want to attempt a landing on Europa, you’d better bring a repair kit. Parts of its surface may be covered in metres-long blades of ice that could make exploring Jupiter’s frigid moon a dangerous endeavour.

In the driest, coldest places on Earth, sunlight bouncing off of small depressions in ice and snow creates pointy formations called penitentes, which can reach several metres tall, as shown in the picture above. As the sunlight hits the bottom of the divot it turns the ice directly from a solid to a gas, which floats away and leaves icy spikes behind.

Europa is much colder and much drier than Earth because it has almost no atmosphere, and it has lower gravity. Daniel Hobley at Cardiff University, UK, and his colleagues calculated that means it could build even bigger penitentes.

The researchers found that, over Europa’s lifetime, they could reach heights of 15 metres, with holes about 7.5 metres across between them.

Because penitentes grow faster when the sun is directly overhead, they are likely to mostly appear around the equator. That would give the moon a spiked belt around its middle.

This could be a problem for any spacecraft hoping to land in the region, either because of the spikes or the perfectly spacecraft-sized holes between them.

“You can imagine something getting lodged in there and flopping around,” Hobley says. “But if you already know the surface is likely to be spiky and full of holes, you can probably plan around that.”</s>Jupiter's moon Europa is teeming with towering shards of ice that will make future missions 'treacherous', researchers have found.

They raise fifty feet above the surface, stretching across the whole equator of the celestial body and beyond.

The huge pillars are just feet apart and there are fields of them meaning spaceships could find it hard to land, say scientists who worked on the study.

The mysterious waterworld is the likeliest place in the solar system to find alien life and may be more visually impressive than imagined.

The report conjures visions of the 300 mile-long solid ice barrier in Westeros - the fantasy land depicted in G R.R. Martin's best selling books that spawned the world's most popular TV show Game of Thrones.

WHAT ARE THE SHARDS OF ICE? Known as 'penitentes', these massive icy shards are nature's ice sculptures. The beautiful snowy spikes can be found in the Andean glaciers where the air is particularly dry. These are about 16 feet (5 metres) tall - 'pixies' compared to those on Europa. The stunning features always point towards the midday sun. They are carved by a process known as sublimation which requires bright, sustained sunlight as well as cold, arid and still air. As ice turns directly into water vapour without first melting into a liquid, the distinctive formations are left behind. On Earth they occur in high altitude tropical and subtropical areas - such as the Andes. But Europa has the perfect conditions for them to appear in abundance and in a uniformed pattern thanks to its bleak landscape. It has the right thermal conditions for the ice to sublime without melting and there is very little variation in the angle in which the Sun shines down.

Lead author Dr Daniel Hobley from Cardiff University's School of Earth and Ocean Sciences, says landing a spacecraft will be devilishly difficult.

He said: 'The unique conditions of Europa present both exciting exploratory possibilities and potentially treacherous danger.

'The presence of sharp, blade-like structures towering to almost 15 metres [50ft] high would make any potential landing mission to Europa extremely precarious.'

The study, published in Nature Geoscience, sheds light on the problems space engineers will face in the search for extra terrestrials.

Europa harbours a huge ocean under an icy crust up to 15 miles (24km) thick - conditions in which organisms could thrive.

A bit smaller than Earth's moon, the subterranean sea is estimated to be between 40 and 100 miles (64 to 160km) deep.

Nasa hopes to put a robot on the moon, drill through its crust and swim through the icy sea - a scenario played out in the 2013 sci-fi thriller 'Europa Report'.

But Dr Hobley says 'fields of 15-metre-high shards of ice' pose a major threat.

Known as 'penitentes', they are nature's ice sculptures.

The beautiful snowy spikes can be found in the Andean glaciers where the air is particularly dry.

These are about 16 feet (5 metres) tall - 'pixies' compared to those on Europa.

The stunning features always point towards the midday sun.

They are carved by a process known as sublimation which requires bright, sustained sunlight as well as cold, arid and still air.

As ice turns directly into water vapour without first melting into a liquid, the distinctive formations are left behind.

On Earth they occur in high altitude tropical and subtropical areas, such as the Andes.

But Europa has the perfect conditions for them to appear in abundance.

It has the right thermal conditions for the ice to sublime without melting and there is very little variation in the angle in which the sun shines down.

The discovery was made after Dr Hobley and colleagues used observational data to calculate the sublimation rates at various points across the moon.

This enabled them to estimate the size and distribution of the penitentes.

The study showed they are up to 15 metres (49.2 ft) in height, with a spacing of just 7.5 metres (24.6 ft) between each.

They could be anywhere but will be most prevalent around the equator.

Evidence of penitentes has also been seen on Pluto, suggesting such jagged terrains are common on icy worlds.

Nasa's Europa Clipper is being launched in 2022 to carry out a number of fly-bys and it is hoped a landing mission will follow soon after.

'We hope studies like ours will help the engineers to develop innovative ways of delivering landers safely on Europa's surface so we can find out even more about this fascinating place - and potentially look for signs of extra-terrestrial life', said Dr Hobley.

Europa's surface is fragmented by grooves and ridges.

This is the first time that high-resolution imagery has been able to determine how smooth the ice is between these features.

Co author Dr Jeff Moore, a planetary geologist at NASA's Ames Research Centre, Mountain View, California, said Europa Clipper could directly observe penetentes with its high-resolution camera.

It may also be able to measure other properties of these amazing features with the spacecraft's other instruments. Dr Moore is a co-investigator on the imminent mission.

Europa is not the only prime candidate for life in our solar system.

Saturn's ocean-bearing moon Enceladus has been found to contain hydrogen in hydrothermal vents, an environment that may have given rise to life on Earth.</s>Possible missions to Europa in the search for life could be challenging due to potential jagged ice covering its surface. Buzz60
New research suggests Europa, a moon of Jupiter, may be covered in tall, jagged ice spikes, presenting a problem for any potential landing on its surface.