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More Evidence for Plumes on Europa

Were deviations in Jupiter’s magnetic field, recorded by Galileo’s magnetometer during a flyby of Europa in 2000, an indication of a cryovolcanic eruption? The data on this event have been evaluated by several independent groups in Europe and the US, an indication of how much interest such a plume would generate. If, like Enceladus, Europa occasionally blows off material from below the surface, we would have the possibility of collecting water from its ocean without having to drill through kilometers of ice.

Now a team of European Space Agency scientists led by Hans Huybrighs, working with colleagues at the Max Planck Institute for Solar System Research (MPS), has gone to work on the question, this time through the measurements made by Galileo’s Energetic Particles Detector (EPD), an instrument with roots both at MPS and the Applied Physics Laboratory of Johns Hopkins University (APL). EPD recorded significantly fewer fast-moving protons near Europa than expected during the same flyby. This adds weight to the conclusions of those finding evidence for a plume in the magnetometer data.

Jupiter’s magnetic field is twenty times stronger than Earth’s, extending far enough into space that Europa orbits within it. What Huybrighs and company set out to do was to simulate conditions during the flyby, modeling high-energy proton movements that correspond with what the EPD recorded.

The question raised by the EPD instrument is why these energetic protons were disappearing during the E26 flyby, an observation earlier considered to be caused by Europa itself obscuring the detector, making the measurement unreliable. But the paper makes the case that some of the proton depletion could only be explained by a plume of water vapor that disrupted Europa’s tenuous atmosphere and perturbed magnetic fields in the region. Indeed, the simulations are only successful under the assumption of a plume, whose effects are added into those caused by the atmosphere. Evidence for a plume noted by earlier researchers is thus strengthened by an analysis drawn from an independent dataset.

Image: Color image data from the Galileo mission recorded between 1995 and 1998 were used to create this depiction of Europa’s cracked and icy surface. The inset shows dark reddish, disrupted regions dubbed Thera and Thrace. Credit: Galileo Project, Univ. Arizona, JPL, NASA.

The authors’ conclusion also highlights how much we do not know about the environment at Europa, while pointing to a helpful tool for planning purposes on future missions:

Large uncertainties remain in the properties (density profile, 3D structure, temporal variability…) of Europa’s tenuous atmosphere and plumes (Plainaki et al., 2018). This study emphasizes that energetic ions are an important tool that can contribute to the detection and characterization of Europa’s tenuous atmosphere and plumes and probe its moon-magnetosphere interaction, independently of other methods. This is in particular relevant for the upcoming JUICE mission (Grasset et al., 2013), which has the instrumentation to detect both energetic ions and ENAs, using the Particle Environment Package (PEP)…

The ability of JUICE to detect energetic charged and neutral particles near Europa will help us spot future plumes. Note this ESA description of the Particle Environment Package:

A plasma package with sensors to characterise the plasma environment in the Jovian system.

PEP will measure density and fluxes of positive and negative ions, electrons, exospheric neutral gas, thermal plasma and energetic neutral atoms in the energy range from <0.001 eV to >1 MeV with full angular coverage. The composition of the moons’ exospheres will be measured with a resolving power of more than 1000.

For more on the science payload of this mission, with 10 instruments onboard, click here. JUICE launches in 2022 in a mission aimed at Europa, Callisto and eventual orbit at Ganymede.

The paper is Huybrighs et al., “An active plume eruption on Europa during Galileo flyby E26 as indicated by energetic proton depletions,” Geophysical Research Letters 12 May 2020 (abstract).

{ 17 comments… add one }
  • Gary Wilson May 13, 2020, 12:56

    Great work on the possible plume detection. Putting a lander down on Europa in a plume region sounds very difficult technically but very rewarding if it were to work. Another risk vs reward calculation required and first we would have to conclusively show such activity occurred in detail at high resolution. Many years of work ahead.

  • Alex Tolley May 13, 2020, 16:39

    To get a plume sample we have to be able to predict the location and timing of a plume or plumes to ensure our sampler probe flies through the plume. Anything that will help in this determination would be of help so as not to waste the opportunity. Ideally, we need to detect an unambiguous biosign, such as frozen cells or cell breakdown products. These must be distinguishable from abiotic material.

    If life is unambiguously detected, then it makes sense to put a lander on teh ground in the place where the plume material falls to look for more material, even multicellular life. This approach is like beachcombing looked for dead marine life that is washed up rather than going to the sea in a submarine. Not ideal, but a lot less expensive and difficult.

    I hope the sensors on the JUICE mission provide some confirmation of the plumes, their location, and frequency. They might also help locate the plume source on the surface for future sampling and lander missions.

  • Robert Flores May 14, 2020, 13:23

    I am assuming these cryovolcanoes have an similar morphology to
    their counterparts on Earth. Does that mean that there is a long channel which spans from top to a deep reservoir of slush. I will call these structures Volcanoes (of Europa), to save letters.
    What I think is interesting is to estimate what thickness is the “CORK’ that keeps that reservoir isolated when the volcano is inactive. If these plumes occur with regular frequency, but of limited size and scope does it not stand to reason that the CORK is not very long, maybe less than Soccer field. On the other hand, if these volcanic events occur during special alignments of the moons and Jupiter, then one would expect that the cork will build up closer to Kilometer scale of length. I know that the Cork and Reservoir behavior will depend on their chemical composition and on frequency of eruptions, so we are going to be looking at a matrix of posibilities. So here is my estimated
    values for these CORKS depending on two variable below.

    Mostly Ice-water. Mix of Ice Water + Ammonia

    1/week/Small cork 100m cork 50m

    1/two mo int/Large cork 1,200m cork 600m

  • Andrei May 14, 2020, 15:00

    Thank you for sharing another example where old data provide new insights.
    If working as intended Juice’s RIME radar will answer many questions about the internal structure of all the 3 icy moons at Jupiter. And if lucky show us the locations of plumes and near surface water on Europa. The question is if there’s reservoirs of water near the surface, or even a continuous layer of ice separating an lower ocean and a near surface layer of water.
    Ganymedes might actually have a whole set of such layers each separated by ice.
    With weaker tidal forces, it’s not certain Callisto actually have liquid water.
    But the main focus for Juice will after all be Ganymede since it is to orbit that moon for an in depth study. There’s only 2 flybys of Europa, so only luck if any of those go trough a plume. Yet ESA mention the possibility in a press release, so perhaps they look into a possible tweak of the flyby to increase the chances.

  • Geoffrey Hillend May 14, 2020, 17:03

    Some remote sensing or different types of spectrometers would help to locate plume material.

    • wdk May 17, 2020, 16:27

      Noticed on some of the remarks above suggestion of landing or other
      remote sensing. But I don’t think I saw Europa orbiter explicitly
      mentioned. One possible way would be a hitch hiker to a subsequent
      mission out that way, even cube sat sized. Sampling with a lander has its own contamination hazards associated with braking. The minimum
      size of an orbiter to make an organic compound determination – it might yet be defined. Maybe the downlink will be critical. But high inclination and some attention to nodal regression could allow either a specific target or a wide search for plume effects.

    • Michael T May 18, 2020, 4:37

      JUICE has lots of remote sensors! Or were you thinking of another spacecraft or telescopes?

      I like the idea of a piggyback mission as suggested in wdk’s reply. Could such a thin possibly be added to to JUICE? Would a cubesat have the manouvering capability to reach the plume, based on data obtained by its “mother” ship (or “sow ship”, seeing as it’s a piggyback mission :-) ) en route? Could a microscope fit on a cubesat?

      • wdk May 19, 2020, 12:39

        Michael T.,
        At a November “space con” I did visit a booth for a suite of science application nano-satellites and I did see some very short focal length optics that might be just what the doctor ordered.

        If I may elaborate a little further on a Europa cube sat:

        How far advanced the Juice mission is in development, I don’t know. Though there are often calls for experiments, instruments or riders on large missions, the later the less likely for such inclusions .

        But should there be other Jupiter missions in planning and with caveats in mind:

        Much of this is very much akin to what happened with Enceladus and Cassini, focused on the detected south polar vents. Cassini flew by without braking into Enceladus orbit, of course, but the data collected became more and more intriguing, incentivizing similar plans for closer scrutiny.

        As described, Europa
        -could have had a recent water volcanic event,
        -one going on currently, or
        – it could have a follow up elsewhere within a few years.

        That argues for full geographic surface coverage or monitoring and some lifetime for the mission. A satellite low enough could fly through the plume or detect emissions, whereas a lander has some roulette table issues of a different sort.

        Now a Galileo follow up like Juice would be a very expensive mission in cost and propellant to divert to Europa – and especially into a high inclination low altitude orbiter. Even with a cubesat or nanosat it will be no small expenditure of delta velocity and flybys to get the payload suite into position. And to perform the mission, the instrumentation would have to be selected narrowly: to detect, to distinguish chemically or biologically – and to transmit back.

        Distinct from Saturn, the e-m environment is harsher. Solar power would be difficult to track and to keep operating due to charged particle depositions in the jovian magnetosphere.

        I’ve seen 3-body studies of Jupiter, Europa and orbiters in the literature, e.g., AIAA Journal of Spacecraft and Rockets.
        The astrodynamics are interesting, some stability questions but placing satellites in LEO is not un-doable.

        Whether a launch of a separate orbiter should be done after a
        principal spacecraft reaches the Jupiter sphere of influence or before is an open question. Perhaps dependent on navigational resources.

        With Cassini, the Huygens lander and spacecraft, it appears, remained mated past initial periapsis in July of 2004. Cassini was a platform for aiming at Titan (released on 25 December 2004 and arriving 15 January 2005 at Titan). Aero-braking instead of entry could be considered in this case – but I suspect flybys and delta v maneuvers would be more effective for placement.

        A small satellite would have several controlled orientations:
        1. Down-looking at Europa to detect the hotspot.
        2. Velocity direction to align a collector.
        3. Sun tracking if solar power is provided ( built to provide
        power budget in less than 4% terrestrial intensity).
        4. Antenna orientation for communication with relay or Earth.

        Taking into account that the 3 body problem is significant, I am
        not sure where a genuine circular orbit would be the best solution to these pointing problem requirements or not.

        The pointing requirement would also have consequent payload budget and total mass implications. All these things can be done with existing micro-satellites ( I hesitate to say with cube sats), but the environment of Jupiter and Europa is more harsh than typical low earth orbit applications.

        Some of the things described could be tough or costly. But if there are genuine hydro-volcanic events going on on Europa, it might be worth it after all.

        • Michael T May 21, 2020, 4:31

          @wdk Thanks for the informative reply. The orbital dynamics were issues I had a vague idea about, which seems confirmed. So IF one was lucky one could detect a plume at some distance (with the mother ship) , work out a trajectory and execute it, but it would be a big set of “if”s, though from what you write, not impossible.

          Maybe one could “do a Cassini” instead; maybe add some other instrument to JUICE, and bring JUICE itself in for a run through a plume.

          But maybe it’s too late to add instruments or piggyback missions to JUICE.

          “LEO” for Low Europa Orbit :-). May need another acronym :-)

  • Brett P Bellmore May 16, 2020, 13:46

    Nice to see your site back up; A little late paying the hosting service?

    I personally like the idea of boring through the ice down to the water, it has a Tom Swift vibe to it, and would permit sampling on the way down. But it’s certainly not the low cost option.

    • Paul Gilster May 16, 2020, 20:12

      Nope, a security certificate that refused to take. Took 36 hours to figure out why.

  • Gary Wilson May 17, 2020, 13:59

    Good to see you found the problem Paul. I was missing my daily fix!

    • Paul Gilster May 17, 2020, 19:12

      Thanks, Gary. Glad to have this resolved!

  • ljk May 24, 2020, 13:16

    Finding Life on Europa: Do we have the chemistry?

    The SETI Institute – May 22, 2020


    Decades ago, science fiction offered a hypothetical scenario: What if alien life were thriving in an ocean beneath the icy surface of Jupiter’s moon Europa? Recent observations of Europa from Earth-based telescopes, and reanalysis of spacecraft data, have increased the confidence for Europa’s ocean.

    NASA, together with other space agencies, is looking for a way to explore Europa and hopefully identify the presence of life after solving technological challenges like landing on a chaotic and cryogenic surface, drilling into its crust and analyzing samples directly. If there is an ocean of liquid water beneath the relatively thin ice shell of Europa, is life there as well?

    The possible detection of a thin plume of water in 2019 being ejected from Europa’s surface has re-energized the community, which is now looking for a new way to answer these questions. Could a spacecraft travel through this plume, sample and analyze it, and confirm the existence of life in this ocean? What kind of biomarkers should we look for? What would they tell us about this extraterrestrial life?

    In conversion with:

    Dr. Jill Mikucki, professor at the University of Tennessee at Knoxville, is a microbiologist and Antarctic researcher who studies ecosystems under the ice. With her research in the McMurdo Dry Valleys, she has demonstrated that microbes can grow below ice in the absence of sunlight, a process that could potentially take place on Europa.


    Dr. Cynthia Phillips is a planetary geologist at NASA’s Jet Propulsion Laboratory. Additionally, she serves as project staff scientist for the Europa Clipper Mission, a NASA mission to be launched in the 2020s that will conduct a detailed survey of Europa, look for ingredients for life on the crust and search for locations of warmer ice and perhaps recent eruptions of water. She is also working on mission concepts that would study Europa from the surface and eventually explore its subsurface ocean.

    Hosted by Bill Diamond, and Simon Steel.

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