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Homing in on Europa Under the Ice

We wrap up our look at the American Geophysical Union meeting last week in San Francisco with an update on Europa. An interesting point that William McKinnon (Washington University, St. Louis) made in a news briefing there has that what had been a belief that there is an ocean on Europa is now hardening into a certainty. The intriguing next step is to learn more about that ocean, and here things get tricky. Just how do you study an ocean on a distant world upon which you have yet to land?

Fortunately, magnetic variations around Europa as well as observations of how the moon flexes and deforms as it orbits Jupiter can tell us much. Thus the need for a Europa orbiter, a mission that could measure gravity and magnetic fields as well as determining surface composition. Another area of interest for such a spacecraft: Are there recent eruptions from this geologically young world? The search for hot spots from such events could get interesting, to judge from what Cassini found on Enceladus.

Complementing such work will be the use of radar sounding, which should give us a solid idea of how thick the blanket of ice over the ocean is. Donald Blankenship (University of Texas at Austin), who joined McKinnon in the briefing, noted that ice-penetrating radar should be able to locate liquid water both within and beneath the shell. “Free water within the icy shell,” Blankenship adds, “and its relationship to the underlying ocean will be a critical factor in determining the habitability of Europa.”

Cross sections of Europa

Image: An artist’s conception showing two possible cut-away views through Europa’s ice shell. In both heat escapes, possibly volcanically, from Europa’s rocky mantle and is carried upward by buoyant oceanic currents. If the heat from below is intense and the ice shell is thin enough (left), the ice shell can directly melt, causing what are called “chaos” on Europa, regions of what appear to be broken, rotated, and tilted ice blocks. On the other hand, if the ice shell is sufficiently thick (right), the less intense interior heat will be transferred to the warmer ice at the bottom of the shell, and additional heat is generated by tidal squeezing of the warmer ice. This warmer ice will slowly rise, flowing as glaciers do on Earth, and the slow but steady motion may also disrupt the extremely cold, brittle ice at the surface. Europa is no larger than Earth’s moon, and its internal heating stems from its eccentric orbit about Jupiter, seen in the distance. As tides raised by Jupiter in Europa’s ocean rise and fall, they may cause cracking, additional heating, and even venting of water vapor into the airless sky above Europa’s icy surface. Credit: Michael Carroll, courtesy NASA/JPL.

That issue of habitability is also more interesting given new models showing that radiation on Europa is perhaps up to two-thirds less powerful than previously thought, making the prospects for orbital spacecraft and landers a little less daunting. Moreover, reprocessing of Galileo data is telling us more about the surface of this frozen world, including the presence of carbon dioxide, which is most likely coming from the ocean below. Future orbital missions may well find compounds Galileo’s instrumentation was unable to catch.

This is an interesting point in itself. We’re collecting so much data in our recent missions that researchers can be overwhelmed with the inflow. Further analysis and reprocessing — in some cases years or decades after the fact — can tease out information that had hitherto been missed. Thus the infrastructure demand is clear: We can’t afford to lose even the most apparently insignificant datasets, a fact that would seem obvious but bears repeating given the challenge of examining old Pioneer data. In terms of both storage and format, future scientists have got to be able to recover anything a deep space probe can send.

So will we ever get some kind of vehicle able to penetrate the ice on Europa? The answer may depend on what a future Europa orbiter, when and if it is funded, finds. One project to keep an eye on as these things are debated is Stone Aerospace’s Endurance, an autonomous underwater robotic vehicle that will be deployed in Antarctica some time in 2008, testing approaches and procedures for studying a frozen ocean. The kind of biochemical maps Endurance makes may one day tell us whether anything lives on Jupiter’s most provocative moon.

Comments on this entry are closed.

  • Adam December 15, 2007, 17:20

    Hi Paul

    Europa’s ocean seems like a habitat for life, but it’s lacking in a serious energy source to support that life – sunlight. Our complex biosphere is driven by the Sun and I can’t see how Europa can have a biosphere anything like ours with multicellular animals. But it does have chemical energy from both tidal volcanism and the free-radicals created in its icy crust by Jupiter’s continual radiation bombardment.

    Would that be enough to initiate life? No way of knowing what that needs, just that we know it did happen here (or on Mars?) Personally I think Europa is a good target for discovering a second origin of Life because there’s no way panspermia could have delivered life there – impact speeds are too high and there was no atmosphere to deccelerate meteorites. Venus, Earth, Mars and Titan all probably exchanged material that could have transported viable organisms, and thus I hypothesise they will represent one extended biosphere. But Europa was locked beneath the ice at the bottom of a deadly gravity well – any Life there will be truly indigenous.

  • david December 15, 2007, 19:48

    Europa is the world that most interests me when it comes to our own solar system. The thought that there “might” be another biosphere so close by that we can study, and compare the earth’s with, is …. incredible.

    As for enough energy to sustain life. On earth life can sustain itself in very cold places – such as the arctic oceans. The earth has a solar energy input of approx. 178,000 terrawatts. Of that around 100 terrawatts is used for plant photosynthesis. (ie. It doesn’t require a huge amount of energy.) On Europa if there is enough energy to melt the ice then there is probably enough to sustain life. Though since we don’t know enough yet on how life started it probably would be hard to say for sure there is enough energy there to start the ball rolling. On the other hand if there are volcanoes then there is the potential to get the ball rolling even if it does require more energy than merely sustaining it would.

    A lander that can get through 3+ kilometers of ice is out of the question in the near future. However a study of the ice where water has escaped from the ocean below should provoke some curiosity. At the very least such a lander might confirm the existence of life there. Wonder how many years before we do send such a lander – an interest in such things really requires more patience than what I’ve got. Could the composition of the ice be studied from orbit somehow? Maybe by crashing a small object into the surface and studying the resulting vapor?

  • Enzo December 16, 2007, 8:00

    This article :

    says, at the end, that “the best fit to the Galileo data suggests an
    average thickness of 4 kilometers”.

    This is much less than what I remember reading a while ago. Does anyone
    know when this new low figure was first mentioned ?
    I remember when 10 Km was considered at the low end of the estimate.

  • Gregory Benford December 16, 2007, 17:21

    Europa demands nuclear rockets for real exploration — especially enough heat to penetrate a 4 km ice barrier. Indeed, nuclear rockets are essential to answering the large questions throughout the solar system. Subsurface life on Mars is far easier to find, if it is there, than Europa’s huge challenge. Let’s do that first. A manned expedition is essential, since NASA’s own estimate in the 1990s (the Mars Outpost panel I served on) was that we needed 30 or more years of robotic development to make a serious attempt at drilling and descent into caves. See my BEYOND HUMAN, nonfiction out now, for this argument

  • dad2059 December 16, 2007, 18:42

    Europa’s ocean seems like a habitat for life, but it’s lacking in a serious energy source to support that life – sunlight. Our complex biosphere is driven by the Sun and I can’t see how Europa can have a biosphere anything like ours with multicellular animals.

    The energy source would be Europa’s own flexing crust, which theoretically could be as energetic as Earth’s. Chimney smokers spewing hydrocarbons and other mineral nutrients is plenty of food for multicellular life. Not as much radiation leaking through the ice and crust is a help too.

    That makes the Endurance probes’ success that more important.

  • Adam December 16, 2007, 19:32

    Hi dad2059 & Greg Benford

    dad2059, the hydrothermal vent life in Earth’s oceans is supported by the oxygen created by the photosynthetic biosphere aboved them. While some oxygen might be brought down in solid-state convection of Europa’s ice it will be nothing like what powers life in Earth’s oceans. My point still stands.

    Greg, I agree with you on the need for nuclear-power in exploring the planets – the present technical restrictions make a proper mission nigh impossible. Flying to Mars sounds great, but the present commitment of your government to Vietnam II in Iraq makes a manned Mars mission as likely as it was when von Braun proposed it in 1969 for post-Apollo NASA. Why do you Americans keep voting for such bellicose governments???

  • Enzo December 16, 2007, 19:50


    The funny thing about a manned mission to Mars is that the longer they wait, the less effective compared to robots it will be. Spirit and Opportunity are much less efficient than human explorer at this stage, but by 2035 (probably the earliest for a manned mission to Mars), the gap between what robots and humans can do will be a lot smaller. And robots will always be immensely cheaper to deliver to Mars (or anywhere else for that matter).
    I’m not saying that by 2035 robots will be better than humans, just that the cost differential will be the same as now (huge), but the advantages of a human mission will have shrunk substantially.
    And yes, nuclear is essential for any exploration of the solar system, robotic or otherwise.

  • andy December 16, 2007, 20:14

    The most interesting thing about the potential Europan biosphere is that if it turns out it exists, much greater volumes of the universe suddenly become habitable. Whether Europa is habitable, who knows – I have seen one study that suggests that over the billions of years the ocean may have evolved to near-equilibrium, with the result that redox gradients are insufficient to power an ecosystem there. This might be a common fate that limits the habitability of oceans within icy planets.

  • ramkumar December 17, 2007, 2:26

    Europa has the possibility of sustaing life. By life we dosent mean an advanced one but unicellular or plant life (May be planktons & corel reff type in the ocean beneath ).Out thinking is more Human centric yet even a small cellar creture has it s own importance in nature of life in Universe.
    Nature has invented diversified life forms other than Humans .

  • andy December 17, 2007, 11:21

    Another issue is where does most of the energy from the tidal flexing get dissipated? If the energy is mostly input to the ice shell rather than the silicate core, then the volcanism on the ocean floor might be much reduced. This would result in fewer minerals from the core entering the ocean and also reduce the available hydrothermal vent habitats.

    A further interesting question is whether the ocean floor is in a plate tectonic regime or not: after all, like Earth it is a silicate planet in contact with a liquid water ocean. (AFAIK this is unique in our solar system to Earth and Europa – other icy moons contain sufficient ice to create a layer of high-pressure ice between the silicate core and the ocean)

  • Mark Wakely December 17, 2007, 12:07

    Pictures of Europa reveal a heavily scarred icy surface, the result of gravitational stress and heating. Identifying a crack where the ice is far thinner than three kilometers doesn’t seem beyond the realm of possibility for a future orbiter delivering an oceanic probe. This would make the probe’s task of melting through to the ocean below (and returning to the surface to relay its findings) much less daunting.

    I agree completely with Mr. Benford for the need for nuclear propulsion to open up the solar system for exploration, starting with trips to Mars. One company with an intriguing nuclear engine proposal is Pratt & Whitney. Their Triton thermal engine proposal was unveiled in 2004. Not sure if they’ve since abandoned efforts to market the engine due to ongoing public resistance to anything with the word “nuclear” in it, but it’s still a clever design. Here’s a link to the Triton on the nuclearspace.com website:


  • ljk December 17, 2007, 12:56

    Looking for Hot Views and a Cool Destination for Life?

    Where’s a great place to look for life in our solar system beyond Earth? Jupiter’s moon Europa with its warm, salty ocean, might be a good place to start. Check out a new JPL video at:


    And where would you look for “hot” views of the Red Planet? December’s What’s Up — all about Mars — is now playing at:


  • Rusty December 19, 2007, 12:08

    Actually, sunlight is NOT required as an energy source, even here on Earth. This fact has been known since the discovery of the deep sea geothermal vent communities in the 1970’s, which operate independently of energy input from the sunlit surface realm (yes, there is “marine snow”, but that can’t account for the ecosystems found there). Instead, these systems depend on hydrogen sulfide-based chemosynthesis (as opposed to photosynthesis), much as might conceivably be present under the ice in a place like Europa. THAT’S what makes Europa so exciting to me as a marine biologist…I think it’s the best bet for our finding complex life off our planet in the “near” future. And don’t get excited…by “complex”, I don’t mean intelligent…just possibly something other than bacteria or archaea.


  • ljk November 12, 2008, 23:48


    November 12th, 2008

    Europa Submarine Prototype Gets Another Test

    Written by Nancy Atkinson

    ENDURANCE submarine. Credit: John Rummel, NASA

    A submersible probe that could possibly be used on Jupiter’s icy moon, Europa is taking the next step to test its capabilities. The Environmentally Non-Disturbing Under-ice Robotic Antarctic Explorer, also known as ENDURANCE, will swim untethered under ice, and collect data to create three-dimensional maps of underwater environments. The probe also will take samples of microbial life.

    Earlier this year, it operated successfully in a 25 meter frozen lake in Wisconsin, USA. Now it will plunge under a permanently ice covered lake in Antarctica that is 40 meters deep. ENDURANCE isn’t like the Mars Rovers or other remote-operated probes.

    Once deployed, it’s on its own to systematically explore, take water samples, and find its way back. “It will have to think on its own,” said Peter Doran, an Earth scientist at the University of Illinois in Chicago.

    In the February 2008 test, ENDURANCE successfully found its way around the bottom of the lake and back to the hole that drilled in the ice to get the probe in and out of the lake. It also demonstrated that its electronics functioned perfectly well in cold water.

    At Lake Bonney in Antarctica, ENDURANCE will not only map the lake and explore its biology, but also take a close look at the base of a feature called Blood Falls, where reddish, iron-containing salts spill out of the face of a glacier at the lake’s upper end.

    If all goes well the next test would have the probe or an improved version descend through 3.5 km of ice to one of the world’s largest, deepest and most mysterious lakes, Lake Vostok, also in Antarctica.

    But even that pales in comparison to what a probe might encounter at Europa. Scientists believe that Europa’s ocean could be up to 100 kilometers deep, under 6 kilometers of ice.

    Hot water drills will bore a hole for ENDURANCE to enter the water in Antarctica. If all goes well, the probe will be tested again in 2009.

    But many hurdles remain before an underwater vehicle could possibly head to Europa. Presently, Endurance is too massive to send on interplanetary travel. Engineers will also have to come up with a way to drill through Europa’s icy crust and lower the sub safely through the ice.

    But many scientists feel that an orbiting spacecraft would be the best way to study Europa, before sending an underwater probe. The Jet Propulsion Laboratory is currently working on a concept called the Europa Explorer which would deliver a low orbit spacecraft to determine the presence (or absence) of a liquid water ocean under Europa’s ice surface. It would also map the surface and subsurface for future exploration.

  • ljk November 12, 2008, 23:52

    If we want to find Europan life, we may not have to drill down
    to swim in its global ocean.

    Instead, just check the surface ice for frozen seafood. Or scan
    for Europan life that got blasted into space around Jupiter by
    meteorite impacts.

    I am not saying I don’t want to see a sub probe explore Europa’s
    ocean, but if we are primarily looking for life there, then we should
    check out the surface ice first.

  • ljk September 4, 2009, 11:13


    Russia may launch a Fobos-Grunt based Europa lander in 2020-2021

    Babelfish translation:

    30-08-2009 Russia can send research mission to the satellite of Jupiter – Europe – in 2020-2021

    Russia can send research mission to the satellite of Jupiter – Europe – in 2020-2021, transfers [ITAR]- TASS. On this reported at the sixth international aerospace congress the deputy director of the Institute of Space Research of/[IKI]/of the Russian Academy of Sciences Oleg [Korablev]. On Thursday he made a report “landing apparatus to the satellite of Jupiter – Europe”.

    [Korablev] reminded one that Europe and the three additional satellites of Jupiter were opened by Galileo by Galileo. Contemporary concepts about Europe were formed after through Jupiter system they flew several American automatic spacecraft. In particular, it is established that in Europe are water of the glacial on the basis of these data they appeared different models of the thickness of ice cover.

    According to [Korableva], “in all these models general “raisin” – under ice is liquid water, ocean”. According to the estimation Of [korableva], “Europe is the model of the icy peace, where there can be life”.

    The representative of IKI reported that the scientific research work on the mission to Europe conducts [NPO] of the name Of [lavochkina] and IKI. “Is assumed that in the composition of mission they will be orbital module and landing apparatus, it refined [Korablev]. – Orbital module will remain in orbit of Europe for relaying of data from the landing apparatus.

    With the production of these modules will be used the reserves of the previous missions – “Phoebus- ground” and “Moon- resource”. It is assumed that the mass of landing apparatus will be 550 kgf”. [Korablev] noted that the developers of mission were forced to calculate large limitations on the basis of radiation, since powerful radiation belts of Jupiter can negatively influence onboard equipment.

    “Scientific research works on the mission to Europe it is planned to complete in 2010, reported [Korablev]. – The tentative date of starting – 2020-2021. Under this mission will be used the carrier rocket “proton”. According to [Korableva], the overflight into the system of Jupiter and the output to Europe will engage seven years. Landing apparatus works on the surface of Europe of 60-90 days.

    “By the primary task of mission – the search for the tracks of extraterrestrial life and the study of the structure of Europe, noted [Korablev]. – The flight of Russian mission will be carried out in parallel with the analogous missions of European Space Agency and American agency of NASA (National Aeronautics and Space Administration).

    In the opinion [Korableva], in the case of the success of these missions by the following direction of studies of the distant planets of the solar system, most likely, will become Saturn.

  • ljk September 4, 2009, 11:18

    Monday, April 6, 2009

    Europa Hard Landers and Penetrators

    This blog entry continues looking at presentations from the Russian-sponsored conference last January on Europa landers. The last entry looked at a proposal for a highly capable lander. This entry looks at proposals for two smaller landers.

    Concepts for planetary landers fall into three classes. The first is for soft landers like the Mars Phoenix or MER rover craft. Combinations of parachutes, rockets, and or airbags soften the landing force. As a result, highly sophisticated craft and instruments can be delivered to the surface.

    The other two classes of landers only partially spell the energy of descent and as a result do what can be termed as a controlled crash with style. Hard landers simply hit the surface, bounce and eventually come to a stop. Penetrators look like small rockets and burrow, nose first, into the ground and use the friction of ground penetration to stop some distance beneath the surface.

    Both classes of landers require hardened instruments and system electronics, which limit their capabilities. There isn’t room for complicated masts to hoist imagers or robot arms to gather carefully identified samples for analysis. Instead, one or two simple instruments are carried. The landed mission lasts until the small batteries are exhausted.

    The conference had presentations proposing both types of landers. The hard ‘stop and drop’ lander was discussed by a team from the Jet Propulsion Laboratory, one of NASA’s centers. The team presented a number of possible instruments, but focused on an accelerometer (presumably to study the surface hardness but possibly also to measure some seismic activity), a gas-chromatograph/mass spectrometer, and a camera. The goal would be to conduct measurements for a full Europan day (84 hours) plus an additional 12 hours for additional data relay to the orbiter. Approximately 14 to 24 Mbits of data would be returned, depending on the altitude of the orbiter.

    The penetrator presentations was done by the UK Penetrator Consortium. Here a small penetrator, perhaps 60 cm in length, would carry around 2 kg of instruments. Possible instruments include a seismometer, mass spectrometer, soil/environment package, simple surfve and descent cameras. Penetrators are used in a number of terrestrial studies, especially when dropped from airplanes. They have been studied for planetary missions for decades. Except for the doomed Deep Space 2 probes, none that I remember have flown. The Japanese space agency came close to flying penetrators to the moon, but canceled the mission due to development problems.

    Full article and the two presentations in PDF format here: