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Europa Clipper: NASA’s Incredible Hunt for Alien Life

Written by Morris M.

Imagine, if you will, a distant world. A frozen moon, encased in ice, circling a vast planet. 

Beneath its surface lies a lightless ocean – a dark and secret world lit only by the flares of seafloor volcanoes. Stable for billions of years, this ocean of endless night has all the ingredients for life: liquid water, complex chemicals, abundant energy in the form of hydrothermal vents. In fact, it may already be home to alien creatures: perhaps microbes. Perhaps something far more complex. 

What do you think it might take to study such a remote world? What sort of engineering magic would be required for humanity to fly out there and see what lies beneath? 

The good news is we already know the answer. 

Set to launch in 2024, Europa Clipper is one of the biggest, most-complex craft NASA has ever designed. Larger than a basketball court, and equipped with nine cutting-edge instruments, it’s going to try to answer one of the most-profound questions of all.

Are we alone in the universe? 


The Craft

In the mid-19th Century, they were an awe-inspiring – if familiar – sight. The great clipper ships with their three masts: slicing through the waves of the Atlantic, carrying tea and spices. 

Fast forward over 150 years, and their modern namesake is certainly less-familiar. But the awe it inspires is as great as ever.

Currently being assembled at JPL for a fall, 2024 launch, the Europa Clipper is superlative in every sense of the word. 

Standing at 5 meters tall (or 16 feet for those who hate sensible measurements), the craft’s main body consists mostly of a propulsion module about equal in size to an SUV. One equipped with 24 seperate engines. 

Now, that’s not crazy big for a spacecraft. But we’re only talking about height so far. 

It’s the Clipper’s width that’s really impressive. 

Designed to run on solar power, Europa Clipper comes equipped with vast arrays to capture incoming light.


How vast? Well, Jupiter and its moons are five times further from the Sun than Earth. That means Clipper needs arrays large enough to capture sunlight that – to human eyes – would appear dim and distant. 

The result is a pair of solar paneled wings so big, that – taken together – they span 30m. 

That’s the size of a basketball court. Or – to put it in a slightly more-colorful, yet still basketball-related, way – as long as 14 illegally-cloned Shaquille O’Neals lying head to toe in a row.

No other NASA craft yet launched on a planetary mission has come close to this size. Nor is the solar array the only bit of mechanical gigantism on display.

Sticking proudly out the craft like the mast of a 19th Century ship, the onboard magnetometer boom is equally impressive: clocking in at a staggering 8.5 meters (or 25 feet). 

We’ll be going into its uses in a later chapter. But for now, just know that it’s so big that it has to be stowed away for launch, only deploying when the Clipper is safely out in space. 

Speaking of space, this might be a good time to geek out a little bit about the part that’s actually gonna take the craft through the void: the propulsion module.

As we mentioned earlier, this module is the main part of Clippy; with two dozen engines to guide her to Europa. And that requires some serious behind the scenes kit. 

Deep inside the module itself, a huge tangle of wires and connectors rises like the trunk of a tree, shooting different branches out to deliver power where it’s needed. 

Known as the Harness, it weighs a total of 68kg. Like with the solar array, though – and certain other things – it’s really the length that counts.

Completely unfolded, the Harness would stretch 640m, or 2,100ft, or just “a really freakin’ long way”. 

Also pretty freakin’ large: the Clipper’s weight.

At launch (with all its fuel included), Europa Clipper is going to weigh an eye-watering 6,000kg, or 13,000lbs – a weight Shaquille O’Neal could only achieve by somehow cannibalizing 40 cloned copies of himself.

We mention this to give you some idea of how much went into building just the basic body of Europa Clipper, before we even get onto the specialized instruments.  

And, trust me, we’ll being doing a deep dive into those instruments soon enough. 

But first – to really understand what makes them so special – we need to look at the place they’ll be measuring. The remote, icy moon that NASA has made its recent focus. One of only a tiny handful of places outside Earth that may be home to life.


The Moon

All told, the cost of Europa Clipper is currently estimated at $5bn. 

That’s a lot of money. Less than the $9.7bn invested in the James Webb Space Telescope, but significantly more than the $2.9bn NASA spent sending the Perseverance rover and Ingenuity helicopter to Mars.

All of which raises the question: why? Why spend so much dollar sending a craft not to Jupiter, but to just one of its 80-something moons? 

The answer lies beneath the surface of Europa’s cracked and icy shell. 15 to 25km beneath, to be exact. 

Down here in the dark, locked away from sunlight, NASA scientists are convinced there lies a layer of water. A vast, unfathomable ocean. 

And, where we find water on Earth, we nearly always find that most-precious thing of all: life. 

Ice shell aside, Europa is thought to be not too dissimilar to Earth: an iron core and rocky mantle, around which stretches a thin layer of habitability. 

In Europa’s case, that habitable layer comes in the form of a saltwater ocean. One of almost unimaginable depths.

Here on Earth, the deepest ocean point is the Mariana Trench, which bottoms out at an astonishing 11km, or roughly 7 miles. 

Europa, by contrast, laughs at such puny measurements. Although it’ll take the Clipper to really confirm this, it’s currently thought the moon’s ocean stretches down between 60 and 150km. 

That means there could be 100 miles of water between the mantle and the ice shell. An abyss of night so sublime – so overwhelming – it would give H.P. Lovecraft nightmares. 

Nor do the crazy numbers stop there. 

With a diameter of only 3,120km, Europa is a dwarf next to Earth. Smaller even than our Moon. So, it stands to reason that Earth – with its mighty oceans – must hold more water, right? 

Not even close. 

Thanks to its sheer, dizzying depth, Europa’s ocean is thought to contain 3 billion cubic kilometers of water. Enough to drown so many Shaquille O’Neals that it doesn’t bear thinking about. 

Earth, on the other hand, holds less than half that: a mere 1.4 billion cubic km. 

And that’s incredibly exciting, because Earth’s oceans are teeming with life. NASA estimates somewhere between 50 and 80 percent of all lifeforms live in our seas. 

Now, it’s important to remember that water isn’t the only ingredient needed for life to evolve. 


Any environment looking to cook up some funky sea creatures needs two other things besides water: the correct cocktail of chemicals, and an energy source. 

Luckily, the ice moon is thought to have both. 

Since Europa is so far from the Sun, it should really just be a ball of solid, inert ice. 

The fact it isn’t – at least, once you’ve drilled down far enough – means there must be an internal heat source. In this case: friction. 

Because Europa is one of four major moons circling Jupiter, it isn’t only the planet that’s exerting a gravitational pull on it. 

The moons Io and Ganymede likewise tug at Europa’s shell as they pass. This stretches and pulls the planet, creating friction heating, which in turn likely gives rise to things like hydrothermal vents. 

Chimneys pouring out a stream of energy and chemicals, hydrothermal vents are a classic location for finding life on Earth.

At the same time, the tidal heating might also be powering an invisible cycle, exchanging nutrients between the rocky seafloor and the ice shell; creating an ideal primordial soup. 

And, given this soup is thought to have been stable for nearly 4 billion years, life has had plenty of time to, uh, find a way. 

And it may just be getting its energy thanks to the same thing that makes Europa’s surface so hostile: radiation. 

Europa’s shell is so blasted with radiation that nothing could live there. But that same radiation also rips apart the water molecules in the moon’s atmosphere, splitting the hydrogen and oxygen. 

With the hydrogen drifting off into space, the oxygen may – somehow – be recycled back through the ice and into the sea. Since it’s such a reactive molecule, it could potentially provide fuel for anything living down there. 

So, that’s the “why Europa” part out of the way. Now for the really interesting bit. 

Digging deep into the suite of instruments the Clipper will use to uncover the secrets of this world.

The Science

When designing Europa Clipper, NASA evidently subscribed to the “go big or go home” school of planetary science. 

The sheer number of specialized instruments the craft is carrying is insane. A payload of nine individual pieces of kit – plus a high-quality camera – will all work together to unlock this one moon’s mysteries. 

Given there are so many of them, we don’t realistically have time to explore each instrument. So, we’re going to focus on some of the coolest to give you a flavor of what the Clipper will be capable of. 

Perhaps the coolest is the radar array known as REASON.

Standing for Radar for Europa Assessment and Sounding: Ocean to Near-surface, REASON looks to the layman like nothing more than a giant antenna thing. Like something folk in the 1950s might’ve used to watch Leave it to Beaver.

But REASON’s raison d’etre isn’t to check in on Wally and the gang, but to send out high-frequency radio waves that’ll pierce Europa’s ice to a depth of 30km.

That means NASA will be able to build a detailed picture of the ice’s structure. More-importantly, though, it will provide confirmation that Europa’s ocean exists.

Right now, there are so many odd things about Europa that the only realistic explanation is the existence of a subsurface ocean. 

But knowing it theoretically isn’t the same as actually confirming it’s there. This is what REASON will hopefully do: provide solid proof.

More-importantly, REASON should also detect any pools of water lying closer to the ice shell’s surface – potentially where they’re more-accessible. 


Combined with Europa Clipper Magnetometer – abbreviated as ECM – it should paint a pretty amazing picture of Europa’s silent seas.

The massive, 8m-plus mast we talked about in the first chapter, the ECM is designed to measure changes in the moon’s magnetosphere. 

A by-product of Jupiter’s own magnetosphere, Europa’s is thought to be caused by electric currents flowing through the salty subsurface ocean.

Using the data gathered by the ECM, NASA will be able to figure out how deep that ocean really is.

The result will be our first deep understanding of an extraterrestrial ocean; a feat NASA will be hoping to recreate with later missions to the Saturnian moon Enceladus. 

Yet while the work of REASON and the ECM will broaden our understanding of Europa, they won’t answer the most-pressing question: can this alien ocean harbor life?

Hence the need for MISE (pronounced: “mize”), MASPEX, and SUDA.

The Mapping Imaging Spectrometer for Europa, MISE is going to closely examine the moon’s surface, hunting for signatures of the specific molecules that exist there.

Mostly, this will be stuff like sulfates and carbonates. But the team will also be searching for organics – the building blocks of life. 

At the same time, MASPEX – or the MAss Spectrometer for Planetary Exploration – will be performing a similar hunt among the moon’s gasses. 

With its gassy vents, Europa is like your underpants after the end of a sweaty gym session: absolutely funky with fumes. 

MASPEX, meanwhile, is like the locker room pervert giving them a cheeky sniff. Although rather than getting off, MASPEX will be converting them into ions and running tests to figure out what they are. 

With a resolution hundreds of times greater than anything sent into space before, it will determine what’s in Europa’s plumes: including any possible biosignatures.

Finally, SUDA – the SUrface Dust Analyzer – will do the same for the tiny bits of ejecta swirling around Europa. Examining them to see if any point towards the presence of organics. 

And this is just one tiny fraction of what the Clipper will do! 

Other instruments will take thermal readings; run experiments into plasma; collect ultraviolet light; and use doppler shifts in Europa’s radio signal to uncover its internal structure. 

Honestly, there’s enough here for us to do seven more posts on this craft, each digging down further into the geeky science of it all. But sadly, we don’t have time for that today.

Because there’s still one more, major thing we need to talk about: the mission itself.

The Mission

On a clear day in October 2024 – as America is consumed with the partisan rancor of an imminent election – a SpaceX Falcon Heavy will take off from Florida’s Kennedy Space Center, carrying a rare symbol of unity. 

It will be the start of Europa Clipper’s journey to the fifth planet. A journey intended by Congress to give Americans a scientific achievement they can be collectively proud of. 

At least, once it gets there. 

To make it to Jupiter, the Clipper will have to take a weird route – swinging around Mars in February 2025; looping back to Earth for Christmas, 2026; and then shooting off into the void again.

This is to give the craft a gravity assist: accelerating it to much higher speeds than fuel alone would allow, thus shaving years off its journey.

But this is the straightforward part. A simple means for traversing the millions of empty kilometers.

It’s once the Clipper reaches Jupiter in April 2030 that things will start to get complicated. 

The first thing to note is how we said “reaches Jupiter” rather than “reaches Europa” – for the very good reason that Europa Clipper won’t orbit Europa at all. 

Jupiter’s magnetic field is so powerful it generates a vast radiation belt, looping around the planet. A loop Europa falls into.

That means radiation levels so high the Clipper would be rendered inoperable within a month if it orbited the moon. And NASA isn’t spending $5bn for a mere month of science.

Instead, the Clipper will enter an elliptical orbit around Jupiter. One that allows it to go zooming in for multiple Europa flybys; minimizing the time spent in this planetary Chernobyl.

Yet even these small doses will require an extraordinary level of shielding. 

Inside the Clipper, a special aluminum alloy box known as the Vault will seal the craft’s electronics behind a shield nearly 10 millimeters thick – a countermeasure against Jupiter’s radiation first designed for the Juno spacecraft.

Thus protected, the Clipper will be able to make a grand total of 49 flybys spaced two-to-three weeks apart. Fewer than the 53 originally planned, but still more than enough to get a truly spectacular look at this alien world.

Nor will it be the only probe to do so. 


Just as Europa Clipper is one of NASA’s biggest missions this decade, so too is JUICE an example of the European Space Agency pulling out all the stops. 

A somewhat-bizarre acronym of JUpiter ICy moons Explorer, JUICE will arrive at planet five a year after Clipper.

And while its main focus will be exploring Jupiter’s largest moon, Ganymede, it’ll also be conducting flybys of Callisto and Europa.

In other words, we’re going to see a brief period in the early-2030s when two of the most-advanced probes yet built are turning all their instruments onto this distant moon. Teasing out its secrets. Developing a whole new understanding of its past and present. 

So, it’s only natural that NASA wants to return the favor. 

Originally, the idea was to end the Clipper mission by deliberately diving the craft into Jupiter, where it’d be destroyed by unimaginable forces.

Ever since Europa’s potential for supporting life was discovered, all Jupiter missions have ended this way. There’s just too much risk of probes crashing into Europa and contaminating it. 

But not the Clipper.

Instead, NASA plans to deliberately crash it into Ganymede.

Although Ganymede is also thought to have a subsurface ocean, it’s far too deep below the crust for any chance of contamination. And with JUICE watching the show the impact could give the ESA a wealth of data to uncover even more about the solar system’s biggest moon. 

It’ll be a brutal, high-speed death for a project costing $5bn. But it will mean the Clipper contributing to science right up until the end. 

By then, of course, it will already have transformed our understanding of the Jovian system. 

At the moment it impacts Ganymede, Europa Clipper will have been circling Jupiter for years, generating unimaginable reams of data. Data that may open the door to us finding alien life in our own cosmic backyard.

In some ways, it’s hard to even process this. So potentially world-changing might the Clipper’s discoveries be that it’s hard to imagine what will come next. 

Although NASA already has a plan. 

Known as the Europa Lander, the proposal has yet to be funded. But, if selected, it could be ready to launch in 2027 – arriving as a follow-up probe toward the end of the Clipper’s life.

And while the Clipper will see if Europa is potentially habitable, the Lander would go one step further. 

Touching down on the icy surface, it would drill down 10cm (four inches). Nowhere near deep enough to catch a glimpse of alien fish… but deep enough that chemicals from the ocean below wouldn’t have been damaged by Jupiter’s radiation. 

Using an onboard laboratory, it would examine these samples. And maybe – just maybe – find solid proof of something living far below the surface of this ocean world.

Of course, this follow-up mission may never happen. It might be that NASA decides its limited budget is better spent elsewhere.

But whether the Lander flies or not, there’s no doubting that Europa Clipper will go down in history. The modern version of a great, 19th Century ship setting out to sea on a mission not of trade, or commerce…

…but of exploration and unimaginable adventure. 



NASA, Overview: https://europa.nasa.gov/mission/about/ 

NASA, Meet Europa Clipper: https://europa.nasa.gov/spacecraft/meet-europa-clipper/ 

NASA, Europa the moon: https://europa.nasa.gov/why-europa/europa-in-depth/ 

Astronomy Magazine, the flybys: https://astronomy.com/magazine/ask-astro/2022/04/ask-astro-why-will-europa-clipper-orbit-jupiter-instead-of-europa 

Space, how the mission might end: https://www.space.com/europa-clipper-might-crash-into-ganymede 

JPL, Europa Lander: https://www.jpl.nasa.gov/missions/europa-lander 

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