Europa Erupts: Hubble Space Telescope Discovers Tantalising Evidence of Water Plumes on Jupiter's Moon

An artist's concept of the water plumes on the south pole of Europa, discovered by recent ultraviolet observations from the Hubble Space Telescope. Image Credit: NASA/ESA/K. Retherford/SWRI

An artist’s concept of the water plumes on the south pole of Europa, discovered by recent ultraviolet observations from the Hubble Space Telescope. Image Credit: NASA/ESA/K. Retherford/SWRI

“All these worlds are yours, except Europa.
Attempt no landing there.”

— 2010: The Year We Make Contact

 

In the fictional universe of ‘2010’, people on Earth receive a message being described as the most important one ever transmitted, concerning the presence of life on Europa. In the real world, scientists have possibly discovered the most important evidence to date: the presence of a liquid water ocean underground this fascinating Jovian moon.

This year has turned out to be a really good one for planetary science, with important and fascinating discoveries concerning the possible habitability of various places in the Solar System. Just days after we have reported here on AmericaSpace new evidence from the Mars Reconnaissance Orbiter about current flowing water on the Red Planet, it’s time for the fascinating Jovian moon Europa to come to the spotlight. Scientists working with the Hubble Space Telescope announced the results of their observations of water plumes on Europa’s surface.

The location of the water plumes observed in the ultraviolet on Europa's south pole, superimposed on a visible light photograph of the moon. Image Credit: NASA/ESA/L. Roth/SWRI/University of Cologne

The location of the water plumes observed in the ultraviolet on Europa’s south pole, superimposed on a visible light photograph of the moon. Image Credit: NASA/ESA/L. Roth/SWRI/University of Cologne

The new Hubble observations were reported at a press conference during the recent 2013 Fall meeting of the American Geophysical Union, held in San Francisco, Calif., between 9-13 December. A scientific team, led by Lorenz Roth of the Southwest Research Institute in San Antonio, Texas, used Hubble’s Space Telescope Imaging Spectrograph, or STIS, to conduct observations of Europa in ultra-violet wavelengths during November and December 2012. The team was particularly interested in confirming the presence of water vapors coming from Europa, which were hinted at by previous observations from Hubble in 2009. During their 2012 observing campaign, the scientists discovered a vast amount of hydrogen and oxygen ions coming from the moon’s south polar region.

A set of observations made by Hubble in the ultraviolet, in December 2012, when Europa was at the apocenter of its orbit around Jupiter. At left, the hydrogen ion signature near Europa's south pole, and at right, the oxygen ion signature. The red circles point to the ion signatures and white cirlce shows the position of Europa. Image used from the team's presentation at the recent AGU meeting.

A set of observations made by Hubble in the ultraviolet in December 2012, when Europa was at the apocenter of its orbit around Jupiter. At left, the hydrogen ion signature near Europa’s south pole, and at right, the oxygen ion signature. The red circles point to the ion signatures, and the white circles shows the position of Europa. Image used from the team’s presentation at the recent AGU meeting.

“With these images, we were able to detect water vapor in Europa’s south pole, for the first time,” says Kurt D. Retherford, co-author of the study, also of the Southwest Research Institute in San Antonio. “These images point to the existence of water vapor, about 200-km high, at or near the south pole of Europa.”

The presence of ions around Europa might not be seen as evidence of water vapors at first glance, but the moon lies inside Jupiter’s radiation-laden massive magnetosphere. This magnetosphere traps and accelerates charged particles along its magnetic field lines to very high speeds, creating radiation belts of very high intensity while producing auroras on Jupiter and its Galilean moons, including Europa. As Europa completes an orbit around Jupiter every 3.5 days, it sweeps across this intense magnetic field, dragging its magnetic field lines along, which pass right through the interior of the moon. Since Jupiter completes a rotation around its axis approximately every 10 hours, the magnetic field and radiation environment around Europa display a periodic 10-hour variability. By winnowing out these observed variabilities from the Hubble data, the scientists saw that some patterns of ionised hydrogen and oxygen were fixed above the limb of the moon near the south pole.

A set of old ultraviolet observations made on Europa by the Hubble Space Telescope on October 1999, with the new ones on November-December 2012. In the first two observations, Europa was near, or at the pericenter of its orbit, displaying no plumes at all. When it reached the apocenter of its orbit in December 2012, the plumes were clearly visible. A the bottom of the picture, there are three maps of Europa's south hemisphere, showing the possible location of the water plumes on the moon's surface. Image used from the team's presentation at the recent AGU meeting.

A set of old ultraviolet observations made on Europa by the Hubble Space Telescope in October 1999, with the new ones in November-December 2012. In the first two observations, Europa was near or at the pericentre of its orbit, displaying no plumes at all. When it reached the apocentre of its orbit in December 2012, the plumes were clearly visible. At the bottom of the picture there are three maps of Europa’s south hemisphere, showing the possible location of the water plumes on the moon’s surface. Image Credit: Roth et al, Science, Vol. 334, no. 6167.

This observed pattern was consistent with the hypothesis of water coming out of Europa and breaking apart into hydrogen and oxygen ions by the intense radiation around Jupiter. Furthermore, these emissions varied as Europa orbited Jupiter. During its pericentre, when the moon was at its closest to Jupiter, the team observed no emissions at all. These were only seen at or near Europa’s apocentre, when the moon was at its farthest distance from the planet. This bode well with the suggestion of an underground water ocean on Europa and the presence of plumes on the surface that erupt this water into space, driven by Jupiter’s tidal forces which vary according to Europa’s distance from the massive planet.

Jupiter’s massive gravitational pull exerts tidal forces on Europa the same way the Moon  exerts tidal forces on the Earth, creating the tides. This stretching and squeezing of the moon’s interior is at its strongest when Europa is at its pericentre, and at its lowest when at its apocentre. Consequently, any fissures on Europa’s surface would close while the moon was closest to Jupiter and would relax and open when Europa was at its farthest, allowing for subsurface water to erupt through fissures at the surface, accounting for the Hubble observations. “The plume variability supports a key prediction, that we should see this kind of tidal effect if there is a subsurface ocean on Europa,” says Retherford.

A photograph of the the water plumes on the south pole of Enceladus, taken by the Cassini probe. A similar view may await a spacecraft visiting Europa. Image Credit: NASA/JPL/Space Science Institute

A photograph of the the water plumes on the south pole of Enceladus, taken by the Cassini probe. A similar view may await a spacecraft visiting Europa. Image Credit: NASA/JPL/Space Science Institute

A similar phenomenon has been observed on Saturn’s moon Enceladus from the Cassini spacecraft, albeit in a much higher resolution. Cassini discovered the now-infamous fissures, better known as “tiger stripes,” near Enceladus’s south pole in 2005. These stripes consist of a series of four parallel fissures on the moon’s surface that spew out water ice, dust, and organic compounds high into space. Enceladus is another Solar System object believed to hold a subsurface liquid water ocean just like Europa. Although similar water plumes on Europa have long been hypothesised, they were never directly observed until now.

With all these different, exciting lines of evidence coming together, the question about the possibility of life comes naturally. “The discovery that water vapour is ejected near the south pole strengthens Europa’s position as the top candidate for potential habitability,” says Roth. “However, we do not know yet if these plumes are connected to subsurface liquid water or not.”

“We pushed Hubble to its limits to see this very faint emission,” says Joachim Saur of the University of Cologne, Germany, co-lead author and principal investigator of the Hubble observing campaign. “Only after a particular camera on the Hubble Space Telescope had been repaired on the last servicing mission by the Space Shuttle, did we gain the sensitivity to really search for these plumes.”

The proposed Europa Clipper mission. Image Credit: NASA / JPL-Caltech

The proposed Europa Clipper mission. Image Credit: NASA / JPL-Caltech

As powerful as it is observing from afar, the Hubble Space Telescope can’t provide the high-resolution views that a Europa-bound spacecraft would. And although Europa had been studied by the Galileo spacecraft that was in orbit around Jupiter from 1995 to 2003, its cameras and instruments lacked the necessary sensitivity and resolution to detect the plumes. “It’s really unfortunate that Galileo had only 11 passes of Europa,” said Dr. Jim Green, director of NASA’s Planetary Science Division during the press conference. “And all the knowledge we have of Europa is based on observations from those flybys. So the south pole was not covered very well, and my understanding is, that the highest resolution we have for some of those passes is about 100 km per pixel, so looking for these details, would not be found on the Galileo data.”

An artist's concept of ESA's JUICE mission during a flyby of Europa. Image Credit: ESA/AOES

An artist’s concept of ESA’s JUICE mission during a flyby of Europa. Image Credit: ESA/AOES

Indeed, even with Galileo’s several flybys of Europa, approximately 40 percent of the moon was left uncharted, including the south polar regions. And the recent Hubble observations have raised a whole series of new questions. “Do the vents extend down to a subsurface ocean or are the ejecta simply from warmed ice caused by friction stresses near the surface?” asks Roth. At the heart of it all, a key question remains: Is there life in that underground ocean?

In order to gain a better understanding, a dedicated mission to Europa is required. “We really do need a dedicated Europa mission,” Roth points out.

Still, the chances for such a NASA mission in the foreseeable future don’t look good. Although Europa as a destination was ranked as the second-highest priority in the 2013-2022 Planetary Science Decadal Survey and a Europa mission concept called Europa Clipper has been proposed to NASA, lack of funding has forced the space agency to postpone any plans for such a mission indefinitely. Although the European Space Agency has approved the JUpiter ICy moons Explorer, or JUICE mission, which would make some Europa flybys, it is not slated for launch until 2022, arriving at the Jovian system around the 2030 timeframe. With current budget realities, however, even such a mission occurring more than 15 years into the future may be the best we can hope for.

 

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13 comments to Europa Erupts: Hubble Space Telescope Discovers Tantalising Evidence of Water Plumes on Jupiter’s Moon

  • What will it take to shake up the space agencies in order to make Europa missions possible? The “chump change” (as I often say) is available to make the necessary exploration of Europa and the other Jovian moons take place, not “15” years from now, but RIGHT NOW. We owe the scientific community the opportunity to answer the fundamental question of life elsewhere – sooner rather than later.

    Leonidas, your recent articles about the search for habitable moons are truly fascinating.

    • Leonidas Papadopoulos

      Thank you Tom! I’m always humbled to read your feedback, and your insightful and spot-on comments are the thing I’m always looking forward to, in every AmericaSpace post.

      Maybe the recent Hubble observations are the tipping point that gets everyone really interested in funding such a mission. Although JUICE is a fascinating mission in its own right, it will be focused more on Ganymede and other moons, and will only make two flybys of Europa. And personally, I really don’t care waiting 15 years still, to see Europa again close-up. The Planetary Society has started lobbying at the White House and Congress, with the support of at least one Congressional member, Representative John Culberson (R-TX). You can read more about it here. I’m not a US citizen, I’m living far away, and the best I can do frome here, is participating in writing campaigns towards the White House, but I believe its time for everyone in the space community in the US, to start taking representatives by storm, to make them realise the importance of this.

  • Karol

    I couldn’t agree more Tom, Leonidas has proven that he has exceptional research and writing ability. His work is of the highest quality and a pleasure to read. I was about to give up on AmericaSpace when Jason left and the Newspace trolls returned and began their NASA-bashing gibberish and worship of any con man with a good power-point presentation who seem to have infested the space community now that it lacks clear goals and direction. “Put on your pointy-ears, pack your phaser and move out of Mom’s basement boys, we’re all going to Mars in two years.” Perhaps Brian Williams of NBC news gave some insight as to what it would take to shake up those who could make a Europa mission possible – the “Sputnik moment” success of the Chinese. He indicated that their recent success might motivate us to move forward in space exploration. I would like to think so, but I doubt it. The America of the 60’s that gave us Shepard, Glenn et al is dead. Polls show people no longer trust one another, which leads to no one wanting to work together toward a common goal. Greed is good? No. Greed is GOD! We distrust each other to the point that our government teeters on irrelevancy. Young people can twerk but they can’t do mathematics. We can communicate globally but we are more isolated than ever – remember the Lions, Masons, Knights of Columbus, Elks and other groups where people actually spoke face-to-face? Imagine if a politician today had the nerve to say. “Ask not what your country can do for you, ask what you can do for your country.” He would be scorned, ridiculed, and humiliated. The Tea Baggers would want to use his skull as a chamber pot at the mere suggestion of putting country before personal profit. I would love to see a viable American space program, but I believe we have reached our zenith at “one small step” and now our “space program” will be little more than billionaires sending millionaires and pop stars on sub-orbital joy rides. The Chinese might have a base on the Moon someday and plans for a Mars expedition, but we’ll have “American Idol”!

    • Leonidas Papadopoulos

      Once again, I’d like to really thank you Karol! I’m trully honored to receive such feedback, from people such as you. I always admire your writing style as well – it’s always unique, intelligent and witty. And I’m grateful that you chose to stay on AmericaSpace. The site wouldn’t be the same without you.

      Having said that, I kindly urge you to not lose hope. I understand that this is difficult to do most of the time, because so many things around us every day, are disheartening to say the least. The game is lost ony when we abandon hope. There are so many things going wrong, but there are also many things that are right. Sometimes invisible things, that you have to search for and see, but the light of hope is always there. Small little things that can transform us. Take for instance Abigail Harrison, a 16 year-old girl in the US, doing trully some wonderful things. She recently gave a TEDx talk. I urge you to watch it! And what about Connor Johnson, a 6-year old kid, who started a petition on the White House website, asking for more funding for NASA. One of the persons to sign the petition, was Gene Cernan himself, who made a call to the little guy, giving him his support!

      There are many more such individuals like Abigail and Connor. And they represent the hope for the future. And the light they shed, can inspire us all.

      • Karol

        From your lips to God’s ear, my friend.

      • Leonidas has brought an important and exceptional dimension to the quality of America Space. I find the recent articles on Europa and the Jovian moons of great interest and I know they will continue as discoveries unfold. I join Karol in commending Leonidas’s excellent research and reporting. The articles are “must reads.”
        PS – I was unaware that Jason left.

        • Karol

          Tom, having thoroughly enjoyed your posts on AmericaSpace, and knowing that for both you and I, AmericaSpace is absolutely a “must read” (especially with exceptional, gifted writers such as Ben and Leonidas)please allow me to respectfully submit for your favorable consideration the site SpaceFlight Insider at http://www.spaceflightinsider.com. I believe that in addition to AmericaSpace, SpaceFlight Insider will provide you timely, reliable, and accurate information and insight which we members of the space community so value. With sincere respect and esteem, Karol

          • Thank you, Karol. I just bookmarked the site and plan to add it to my “must read” list. A great find and I look forward to the many interesting articles. As we make ever more exciting cosmic discoveries, both sites will add a wealth of knowledge to the “encyclopedia of the cosmos.”

          • Tihomir

            Carol,
            Thanks for pointing out the spaceflightinsider. I took sime time to check it out and would like to subscribe to its news.
            I wasn’t able to find a way to subscribe at the first glance – do you know how?
            Thanks
            Tihomir

    • Tracy the Troll

      Karol,
      You need to read Leonidas’ excellent article on the Webb telescope as he points out that it may very well see surface water on planets…My guess is that will be enough of impetus to really think hard about space propulsion ….really fast space propulsion…

      The thing is our (the US)space program is going commercial as it should…Costs are coming down dramatically..SpaceX reusable rockets will lower costs by a factor of 2 or 3…everything NASA has done has been to lead all us to this point…China claimed a huge success after spending Billions to land a rover on the Moon….Moon Express plans lunar missions starting in 2015 for Millions…

      SpaceX recently was selected to lease the shuttle launch Pad at Kennedy
      space center because of their established performance of launches and the 40 launch schedule they have….Things really are looking bright for me to retire on Mars!!!

      • Leonidas Papadopoulos

        Discovering definite signs of habitable exoplanets will be a monumental event in the history of science and the human race, rivaling in magnitute the revolutions brought forth by Copernicus, Newton, Galileo, Kepler and Hubble. I believe that it could jumpstart our desire to go interstellar.

        But contemporary chemical space propulsion used today by NASA and the private sector won’t cut it. If we’re talking interstellar, we’re talking about really fast propulsion! For many within the space community, even going nuclear won’t do. It’s good for travelling within the Solar System, but I share the belief that some form of ‘exotic’ physics will really take us beyond, like some form of warp drive propulsion. Although it sounds like it’s out of Star Trek, there’s some really serious scientific investigation on this going on.

  • Tihomir

    Leonidas,
    Thank you for writing about Europa and the latest discoveries around it in such a detail! I read most AmericaSpace articles and they are a source of great pleasure and inspiration to me.
    Also, it’s nice to be able to post comments without having to log into a social network first. Ethan’s “Starts with a bang” also lets people comment without forcing them to log into sites they don’t use.
    Anyway, back to science: After all the discoveries about water on Mars (past or current), Enceladus, and Europa, I find it easy to imagine there *MIGHT* be something based on a reproducing DNA there. Let us consider a couple of steps in the future. Imagine we succeed in sending a mission to a Jovian moon (I’d vote for Europa’ ice digging mission sooner than Enceladus’ sniffing fountain one 🙂 because Europa’s fruits are bigger, even though they hang on a higher (more expensive) branch). Imagine a mission detecting something like a bacterium or even a virus. What a milestone that would be!
    Now, I wonder what the next step would or could be?
    A scientific revolution similar or greater than the change from the Ptolemaic geocentric model to the Copernican heliocentric model would happen, that’s sure. But next?
    Environmental protecion of the moon where the discovery was made?
    More missions thereto?
    Panspermia proof?
    As so often, a discovery would start off even more questions than it answered. I’d so much love to live long enough to see it happen!
    Keep writing
    Tihomir

    • Leonidas Papadopoulos

      Tihomir,

      Thank you for your kind words. AmericaSpace has been a source of inspiration for me as well, right from the start. The feedback from people reading the site is always important and wanted, and if it’s positive, it means that we’re on the right track. Yes, Ethan’s site is really great as well.

      Concerning Europa, I share your enthousiasm and awe, about all the posibilities for life there. It’s a point I was trying to make in the article, that we should be on Europa’s surface already! The technical difficulties for such a mission are really huge, but we’ve proven that if we set our sight to it, nothing is beyond reach. I agree as well that the discovery of extraterrestrial life anywhere, be it on Mars, Europa or Enceladus, would be a revolution equal to that brought forth by Copernicus in the 16th century. It could also prove the panspermia hypothesis, of which I’m quite fond of, personally. It just seems so poetic. You can read an earlier article about the posibilities of panspermia on Europa, here.

      On the other hand, I personally don’t like the prospect of ‘planetary quarantine’. Even if the panspermia hypothesis turns out to be invalid, it is highly likely that planetary ejecta from the different planets of our Solar System have fallen to each other’s surfaces, hundrends or thousands of times in the past. We have discovered meteorites from the Moon and Mars here on Earth, and the same thing possibly happened between the other planets too. In the article I linked you above, you can read about a recent study, showing that exchange of material between planets was highly likely during the Solar System’s early years. So, any ‘contamination’ of material from one planet to the other has most probably already occured anyway. Seen in that light, Nature itself might be the biggest ‘pollutant’ of the Solar System’s ‘pristine environments’, more than homo sapiens could ever be.

      Having said that, I certainly don’t propose that we should be totally reckless and uncaring, but things seem to be going into an extreme, with more people arguing as time passes by, that not only we should be kept off from any habitable environments elsewhere, but we should be kept off from the rest of the Universe generally, in order to protect those ‘pristine environments’ be it habitable or not, because we might ‘pollute’ them with our presence.

      Such a prospect of humanity’s ‘confinement’ on the Earth indefinitely is unsettling. I’m working on an article about that, which I’m thinking of posting in the near future.

      Thank you for your feedback and hope that the material here on AmericaSpace, will continue to inspire you.

      With kind regards,
      Leonidas