A Story of Planetary Seduction: The Captivating Charms of Europa

An enchanting image of Europa hanging above Jupiter's limb, as seen by the New Horizons probe in 2007, on its way to Pluto. When will we return there and answer one of the most important questions ever asked: Is there life beyond Earth? Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
An enchanting image of Europa hanging above Jupiter’s limb, as seen by the New Horizons probe in 2007, on its way to Pluto. When will we return there and answer one of the most important questions ever asked: Is there life beyond Earth? Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Here’s Europa for a shilling
No one minds, and she’s quite willing;
Spotless sheets her charms enfold,
She’ll light a fire if it be cold:
No need to have turn’d bull, dear Jove,
The day you sought Europa’s love.

— Antipater of Thessalonica, 1st century AD


Although the Greek poets of antiquity praised the unsurpassed beauty of the mythological maiden princess, they could never have imagined that hundred of million of kilometers away lay a real world of equal beauty and intrigue that would captivate the hearts and minds of astronomers, planetary scientists, and space advocates alike, up to this day. And even though scientists do not have to metamorphosise into a bull in order to cover the vast distances to go to Europa enchanted by its inviting charms, nevertheless making physical contact and landing on the distant moon presents one of the hardest engineering challenges.

Europa was one of the first things Italian astronomer Galileo Galilei saw in 1610 when he turned his telescope upward to examine the heavens for the first time, during a set of observations that would change the world forever. For the next 350 years, Europa, like most of the things that astronomers observed through a telescope, remained just a point of light in the sky. All this changed with the advent of the Space Age, when these points of light started to transform into real and exciting worlds just like our own. Still, Europa holds a special place among them, for many in the scientific community view it as the single, best place in the Solar System to hold the possibility of supporting extraterrestrial life today.

Prior to space exploration, astronomers believed for decades that the moons of the outer planets in our Solar System were frozen and boring chunks of rock and ice. After all, conventional wisdom held that so far from the Sun, every Solar System body would be a denizen of a vast icy planetary graveyard. But the Voyager probes’ fly-bys during the 1970s and ’80s revealed a very different picture. An assortment of dynamic, active, and ever-changing moons orbiting their equally fascinating planets, in setups that could best be described as mini solar systems in their own right. And exploration of Europa brought its own fascinating discoveries: a Jovian moon that, unlike Saturn’s Titan, only holds a very tenuous atmosphere of molecular oxygen, created by the breakup of the surface water ice from the radiation around Jupiter. But the real treat proved to be its interior, which is considered a promised land for astrobiology research, more so than even Titan’s surface itself.

A natural color-processed composite image of Europa. Processed image copyright: Ted Stryk. Image credit: NASA/JPL/Ted Stryk.
A natural color-processed composite image of Europa. Processed image copyright: Ted Stryk. Image Credit: NASA/JPL/Ted Stryk.

With a diameter of 3,120 km, slightly smaller than the Earth’s Moon, Europa is believed to have a layered internal structure, much like the rest of the Solar System’s major planets and moons. Tantalizing evidence have shown that above the layers of an iron core and a rocky mantle lays a vast ocean that covers the entire moon, an ocean comprised entirely of salty water ice. And Europa’s visible icy surface that we observe from afar is this ocean’s frozen uppermost layers. The photographs beamed back by the Voyager probes showed a very smooth and young surface, mostly free of craters and impact features. That surface, though, exhibits some very interesting characteristics that have intrigued planetary scientists: it is criss-crossed by a vast network of red-colored ridges, spanning the entire globe. They look like fractured sea ice that is seen on Earth, more than anything else.

When planetary scientists started studying the photographs and data from Voyager and the subsequent Galileo mission that studied the Jovian system during the 1990s and early 2000s, they confirmed this notion: these ridges, or lineae, are fructures, or cracks, on Europa’s icy surface, caused be the intense tidal forces of the massive, nearby Jupiter and the orbital resonances with the other nearby moons.

High resolution image of Europa's fructured ice crust, taken by the Galileo probe. Image credit: NASA/JPL
High-resolution image of Europa’s fructured ice crust, taken by the Galileo probe. Image Credit: NASA/JPL

“We see places where very clearly the ice has cracked,” says John Spencer, an astronomer working at the Southwest Research Institute’s Department of Space Studies in Boulder, Colo. “And the two sides have spread apart, and material has come up frozen in the middle, to fill the gap.” Far from being a frozen, boring moon, indeed!

“Just like the Earth’s oceans have tides, because they are pulled by the Moon’s gravity, Europa should have a tide, because it’s pulled by Jupiter’s gravity,” explains Dr. Robert Pappalardo, a senior research scientist working at NASA’s Jet Propulsion Laboratory. “And Europa’s orbit gets a little closer and a little further from Jupiter. So, when it’s closer to Jupiter, it’s streched out more, when it’s further from Jupiter it will contract more.” A dramatic representation of this effect, albeit on a larger scale, could be seen on the neighboring moon, Io, orbiting closer to Jupiter. Tidal forces acting on Io are so pronounced that the satellite’s interior is literaly molten, causing the moon to be the most volcanically active planetary body in the Solar System, sporting over 400 active volcanoes! Europa, being farther away from Jupiter, witnesses a same but gentler effect.

Jupiter's moons Io (left) and Europa (right) are captured on the same frame, by the camera onboard the New Horizons probe in 2007, two days after its closest approach to Jupiter on its way to Pluto. Io's Tvashtar volcano is seen erupting at the upper left corner of the moon's disk. The plume erupted, reached a height of 300 km above the surface of Io. Two smaller plumes can also be seen. Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Jupiter’s moons Io (left) and Europa (right) are captured in the same frame by the camera onboard the New Horizons probe in 2007, two days after its closest approach to Jupiter on its way to Pluto. Io’s Tvashtar volcano is seen erupting at the upper left corner of the moon’s disk. The plume erupted and reached a height of 300 km above the surface of Io. Two smaller plumes can also be seen. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Yet, although tidal forces were obviously at work on Europa, this didn’t necessarily mean that a hidden ocean lay underneath. It could well be that the outer icy crust stretched all the way down to the rocky mantle.

But staying true to its seductive nature, Europa held more unrevealed charms.

Studying the long lines of lineae and other chaotic terrain features on the surface, planetary scientists realised that these surface patterns didn’t align exactly the way they should, according to theoretical predictions. Europa is tidally locked to Jupiter, just like the Moon is to the Earth, having the same hemisphere constantly facing toward Jupiter. Taking into account Europa’s synchronous rotation, if the moon’s interior was frozen solid, then the geologic formations on the surface should exchibit a certain position and pattern. But the formations seemed to be displaced, as if the surface ice was rotating faster from the rest of Europa’s interior. For some time, scientists thought that this was caused due to the moon having a “non-synchronous” rotation. But a recent study by Drs. Alyssa Rhoden and Terry Hurford, both working at NASA’s Goddard Space Flight Center, has presented evidence that the ice’s displacement is probably also caused by precession as well, with Europa rotating around a tilted axis, constantly changing direction much like the Earth does. Either way, the surface features’ displacement can best be explained by having a liquid ocean underground, with the surface ice layer sliding above it, thus rotating faster than the rest of the moon’s interior.

Intriguing as these evidence were, they still didn’t provide any proof for the existence of a water ocean. Could it be just a layer of soft ice under the surface, or a molten lava ocean just like the one inside Io?

Artist's concept of Europa's interior. Image credit: NASA/JPL-Caltech/Univ. of Ariz./JHUAPL/Univ. of Colorado.
Artist’s concept of Europa’s interior. Image Credit: NASA/JPL-Caltech/Univ. of Ariz./JHUAPL/Univ. of Colorado.

Enter the Galileo mission’s Magnetometer. While studying the magnetic environment around Jupiter, Galileo found that Europa didn’t possess any internal magnetic field. But its findings were equally interesting. It detected an induced magnetic field close to the surface, with electric current running through the moon’s interior. Induction occurs when a moving magnetic field generates an electric current inside a conducting material. In the case of Europa, because of its orbit around Jupiter the magnetic lines from the massive planet’s magnetosphere were passing right through the moon. But what could the conducting material inside Europa be? “Ice isn’t conductive enough to create such a field,” explains Kevin Hand, a planetary scientist working at the Jet Propulsion Laboratory. “So the best explanation is a region of salty, liquid water below the frozen surface, which supplies a conductive layer. When you go through a metal detector at the airport with a conductor such as keys in your pocket, the alarm goes off. Likewise, when Galileo flew by, Europa set off the alarm.” “It’s very hard to get that pattern, without having an ocean underneath the ice,” adds Spencer.

So the picture was complete. Europa turned out to have all three basic requirements for life as we know it: liquid water, chemistry, and an energy source. But there’s a question still remaining unanswered about Europa, the most important question of all: Does it harbor life as well?

Just like the maiden in Antipater of Thessalonica’s poem, Europa proved to be a truly seductive world, revealing its charms only to those who are willing to go after them. Maybe we could let ourselves be inspired by mythology and borrow some of Zeus’ passion and desire to reach out and touch upon Europa. The rewards promise to be as unimaginable and enticing as the mythological princess’ beauty itself.


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  1. This is an excellent article and having recently watched the movie Eroupa Report with the yesterdays news from IM by Tito and how he plans a Mars Flyby for under a $1B US in 2018 Europa will be coming soon I hope. Next up is Ad Astra Vasmir rocket engine with a Nuclear Reactor and Europa is 4 to 6 months away…Doable by 2030!!!

    • I was equally excited with Tito’s recent report and testimony to Congress. I very much agree that the way to go forward in space is through public-private partnerships such as this. It’s time for space advocates to burry the hutchet and stop arguing over which is best, government space or private space. Truth is, we need both working together, and Tito understands that. Yet, it all comes down to political will and funding. Those things are more difficult to achieve than engineering advancements. With political will and funding, I believe that there’s nothing that we can’t achieve in space.

      • In the 21 Nov Daily Launch of the AIAA it was reported that a Washington Post article stated NASA spokesperson David Weaver was clear that NASA is willing to share “technical and programmatic expertise with Inspiration Mars but is unable to commit to sharing expenses.” Tito wants to “essentially borrow” the NASA SLS with private “donors” contributing 300 million and the taxpayer paying 700 million. The Wall Street Journal reported that Tito admits that in fact the 2017 target date is a “long shot” and that he offered up 2021 instead. The Journal also stated that, “there is a major technical issue that must be addressed: how the planned reentry pod would withstand the heat from the high speeds at which it must travel.” The Houston Chronicle stated that: “To meet the 2017 target date, NASA and Inspiration Mars would have to begin working on it immediately.” (not likely given the current situation in Congress). Your article on Europa was very well written Leonidas, and certainly does make many of us want to continue our program of manned space exploration and not cancel it to save some 73 billion dollars from 2015 to 2023 as set forth in a report from the Congressional Budget Office (AIAA Daily Launch 20 Nov). Perhaps my lack of a degree in Economics prevents me from seeing the “profit” to be made in a voyage to Mars or Europa which would entice “free-market” investors hungry for return on investment to put up their money. There was no private sector investment, no profit made, in Mariner, Ranger, Surveyor, Viking, Phoenix, Pathfinder, Opportunity, Spirit, Voyager, Pioneer, Galileo, New Horizons, Maven. etc. etc. and there probably will be none. Despite slick salesmanship, publicity-hungry billionaires, hot-tub cheer-leading, and wishful dreaming of moving out of Mom’s basement and into a base on Mars with a hot space babe, the final decision as to the role of the private sector in exploring Mars and the outer solar system will be made by the profit-fixated analysts and accountants of Wall Street. Start screaming NASA-bashing howler monkeys, because I trust NASA, fully and unequivocally. Without their genius, hard-work, and dedication coupled with a fervent national desire, adequate long-term funding, and inspirational leadership at the highest levels, no “free-market” fantasy is going to get us to Mars . . . or Europa.

        • Carol
          Have a little faith in the private sector..This mission by IM and Tito has a good chance of happening..Nasa already has a team of 4 men and 4 women training…The SLS/Orion will be ready and the crewed Vehicle up will be done which could be SpaceX…700 million is peanuts in government funding deals…I think it is a go!!!!

          • Stacy, Whether or not I have faith in the private sector is of no consequence. Will Wall Street gamble huge institutional pension funds of firefighters, teamsters, police officers, auto workers, and teachers on “profit from a Mars mission”? There is no doubt, a Mars mission will cost billions. I’ll be waiting to hear that you’ve invested your life savings, pension, and retirement savings in Tito’s private sector venture. Good luck!

            • Karol,
              I see this as no different as when the Europeans left for a better opportunity to come to America. If you have not noticed the concentration of markets on Earth has created a large disparity in wealth throughout the planet. Many will leave Earth for Mars seeking fortune, freedom or fame that will not be found on Earth. The Mars One Mission has more than 200,000 people willing to go to Mars and not come back. As for your belief that Wall Street will not get involved…Of course they will….there will be hundreds if not thousands of new companies that will be created. And yes Pension funds of Teamsters, Police Officers and Fire Fighters will invest in some of these companies at some point. Interestingly Tito’s Private sector portion of 300 M US has already been secured….These private investors see the long term reward (see above), there is a demand to go MARS…And NASA made all of this possible… They blazed the trail and started the ball rolling. And as they turn over hardware design and build to the private sector they will still be using those systems as well. NASA is not going anywhere either they will always exist. … We are starting to build the infrastructure to go to the other planets of the solar system now and I am so glad because yes someday I hope to travel to Mars or Europa or Titan…for fortune, freedom or fame.

        • Karol, Tracy, let’s not get into an argument of which is best, the government or the private sector, or else we’ll not achieve much in space. That’s the point I wanted to make with my comment.

          Having said that, I beleive that there is much dishonesty on the part of those who would like to see NASA’s budget eliminated for the shake of the private sector. In my opinion, what these people are really saying, is ‘don’t give that government money to NASA, give it to us instead because we need government subsidies’. I’m not saying that everyone on the private sector thinks like that, but there’s a part who does, always trying to undermine and find fault with everything NASA does, which to me, not only is infuriating, it’s also unacceptable.

          Those who are not after a government subsidy only, and trully care about our advancement in space, will realise that NASA (should) have a leading role, a pioneering one. That’s what I mean by saying public-private partnership. Whether NASA-haters like it or not, the space agency is the enabler, the one who can lead, because no one else can. If NASA was irrelevant and the private sector was trully the ‘can-do-everything’ magic pill, then commercial spaceflight would have taken off decades ago on its own, and there would be no need for Commercial Cargo and Commercial Crew programs. Clever people like Tito and Bigelow realise that. They don’t try to undermine the established organisations, they try to work with them.

          On the other hand, I’d like to see a NASA that is strong, well-funded and focused. And the focus of the space program shouldn’t be just about destinations, like ‘oh, let’s go to Mars in the 2030’s’. It should be about what we’ll do when we’ll get there. Exactly what the core of the VSE proposed when it was introduced in 2004. To include the Solar System into our economic sphere of influence. And that can come only by enabling permanent settlement of space, property rights and exploitation of space resources. That should be the ultimate goal of NASA’s space program-everything else is irrelevant.

          And in my opinion that can only come by a combination of a strong, leading NASA, that can lead the way, go out and explore, put boots on the ground and find where the trade winds are, and by a private sector that can then come in and find ways to make money, lower costs and enable permanent settlement of the space frontier.

  2. Leonidas’s excellent article on Europa underscores the need to explore this and other moons in our solar system. The remarkable and dramatic photo of Io and Europa by the New Horizon spacecraft is further evidence that mankind’s inquisitive nature must not be allowed to succumb to narrow-minded “thinkers” in charge of determining our future as explorers of the cosmos.

  3. Multimillionaire Dennis Tito needs $100,000,000 in tax payer money, an Orion capsule, and 2 SLS rockets to do mars human flyby. ALL BY 2017!


  4. Unless Tito does an about face, his IM is toast. The administration has already said they aren’t going to fund 70% of his mission… which is the good news. If they had said yes, it’s likely they wouldn’t have met the schedule. Especially since Orion isn’t schedule for crew until 2021.

    What is extremely puzzling is why they don’t shoot for a mission that would only cost them about $250m with hardware that is certain to be ready long before they need it?

    With the lighter Dragon on an F9 they could put together a 13 ton mission that would do the job. Especially since, as this article points out, the existing F9 upper stage could send 22 tons to mars!

    The catch is refueling but that’s an enabling technology we should be doing sooner rather than later.

    Tito doesn’t need $700m from NASA. He just needs one F9 and one FH which will be ready two years before he needs it. That’s about $250m.

    The 13 ton stack on the F9 would include the Dragon, an inflatable (probably from ILC Dover) about 3m3 of supplies and crew.

  5. Ken,
    Good point which is why I think that the powers that be in congress will suddenly come up with the $700 Million for the IM mission because they absolutely need to showcase the SLS/Orion package…If SpaceX steps up and does something like sends a Dragon and lands it on Mars that does not promote positive PR for the SLS/Orion Program…

  6. I wonder how it will play out? If Mars One gets enough funding for their initial lander does SpaceX go along? Can the government send enough pork to SpaceX to keep them in line? For how long? Elon has already said, if he doesn’t like the government’s terms he will not bid on their contracts. He was talking technical control, but once he has more commercial launches they may not allow financial control either.

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