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Seafloor Volcanoes on Europa?

What’s going on on the floor of Europa’s ocean? It’s hard to imagine a place like this, crushed under the pressure of 100 kilometers or more of water, utterly dark, although I have to say that James Cambias does wonders with an ice moon ocean in his novel A Darkling Sea (Tor, 2014). Science fiction aside, Europa Clipper is in queue for a 2024 launch, and we can anticipate a flurry of new studies that feed into plans for the mission’s scientific investigations. The latest of these puts Clipper on volcano watch.

The work deploys computer modeling to show that volcanic activity seems to have occurred recently on Europa’s seafloor. The concept is that there may be enough internal heat to cause melting — at least in spots — of the rocky interior, which would produce the needed results.

How this heating affects the moon is deduced from the 3D modeling of heat production and transfer in the paper, which was recently published in Geophysical Research Letters. The lead author is Marie Běhounková (Charles University, Czech Republic), who describes the astrobiological import of the team’s results:

“Our findings provide additional evidence that Europa’s subsurface ocean may be an environment suitable for the emergence of life. Europa is one of the rare planetary bodies that might have maintained volcanic activity over billions of years, and possibly the only one beyond Earth that has large water reservoirs and a long-lived source of energy.”

Image: Scientists’ findings suggest that the interior of Jupiter’s moon Europa may consist of an iron core, surrounded by a rocky mantle in direct contact with an ocean under the icy crust. New research models how internal heat may fuel volcanoes on the seafloor. Credit: NASA/JPL-Caltech/Michael Carroll.

With massive Jupiter close at hand, it’s no surprise that gravitational interactions should account for heat production in Europa’s mantle, for the rocky interior flexes in the course of the moon’s orbit. The paper drills down into how this flexion operates, where the resulting heat dissipates, and how it results in melting in the mantle.

In Europa Clipper terms, it’s useful to learn that volcanic activity is most likely to occur near the poles, for this is where the most heat is produced from these effects. On top of this, we learn that the volcanic activity likely to be produced here is long-lived, giving life the opportunity to evolve. As an analogue, we can imagine hydrothermal systems like those at the bottom of Earth’s oceans, where seawater and magma interact.

In the absence of sunlight, the resultant chemical energy supports life on the seafloor and could conceivably do so on Europa. Europa Clipper will measure the moon’s gravity and magnetic field, looking for anomalies toward the poles that could confirm the presence of volcanic activity. Long-time Europa specialist and Europa Clipper project scientist Robert Pappalardo (JPL) sees all this as fodder for continuing investigation:

“The prospect for a hot, rocky interior and volcanoes on Europa’s seafloor increases the chance that Europa’s ocean could be a habitable environment. We may be able to test this with Europa Clipper’s planned gravity and compositional measurements, which is an exciting prospect.”

Europa Clipper should reach the Jupiter system in 2030, orbiting the giant planet and performing numerous close flybys of Europa as it surveys the surface, samples any gases that may have been emitted by the exchange of material from below the ocean, and possibly takes advantage of plumes of water vapor. If water is indeed welling up on occasion from below, we may be able to learn a good deal about the interior ocean without having the need to drill down through kilometers of ice.

The paper is Běhounková et al., “Tidally Induced Magmatic Pulses on the Oceanic Floor of Jupiter’s Moon Europa,” Geophysical Research Letters Vol. 48, Issue 3 (22 December 2020). Abstract.

{ 14 comments… add one }
  • torque_xtr May 27, 2021, 15:39

    One possibility about Europan ocean is that it’s likely not everywhere 100 km deep. It’s floor should be able to support truly enormous mountains due to very low gravity and some compensation of lithostatic pressure by hydrostatic one (partial buoyancy of rocks). The height of Mauna Kea from the bottom of the sea, multiplied by the according coefficient, gives 120 km – enough to rise above the surface. Of course, any peaks rising into ice layer would quickly get scraped off, and Europan lithosphere could be weaker than ours because of higher internal heat flow (on Io, mountains are even lower than on Earth). But I think there is a good chance that the shallowest point of it’s ocean is less than 50 km deep, with pressure close to that on Earth’s abyssal plains. Maybe even some terrains resulting from viscoelastic convection indicate volcanic peaks close to ice-water boundary.

  • Michael May 27, 2021, 16:23

    Although the pressure is high its not that much higher than our deepest oceans.

    • Mike Serfas June 1, 2021, 13:27

      The gravity is 14.6% g, so 100 km is about 15 km on Earth. (Were the distance more precise, we might need to do some integrals, since that ocean goes 1/26 of the way to the center of the moon!) Mariana is 10.9 km deep, so the comparison is valid. Somewhere in the process though we lost track of what might be 150 km of ice above that, which would make the pressure more like 35 km deep in an Earthly ocean. As a reality check, https://webhome.phy.duke.edu/~hsg/363/table-images/water-phase-diagram.gif gives us a sense that we have to get to around 1 GPa before water freezes at elevated temperatures; that is 10,000 atmospheres = about 100 km of water on Earth. But looking closely on the graph more closely we could cut the 1 GPa by a factor of 2 or 3 if we’re right around 0 C and the boundary of ice V and VI.

      You’ve made me wonder if any of our trenches were ever *much* deeper, so that some of our life forms could have an evolutionary history of growing on or in exposed surfaces of ice VI. Someone should talk one of our public aquaria into opening a Future Ganymede exhibit where they test life forms from all over the deep ocean at preposterous pressures for future colonization. But be sure to tell the kids not to rap on the glass!!!

  • Geoffrey Hillend May 27, 2021, 16:39

    In order for life to have any chance of forming on Io, it would have to be higher up in the water since the pressure near the bottom of 100km or 62mi deep ocean might be too high for life to form. The heat still might be warm right beneath the ice over a magma mantle plume that has a vent and volcano at the surface.

  • gbaikie May 27, 2021, 17:33

    Europa gravity: 1.314 m/s/s (0.134 g)

    With 1 gee: 10 meter depth of water: 14.7 psi or 1 atm of pressure.
    0.134 g 10 meter deep: 1.9698 psi
    Say on, Europa, you went thru 110 meter ice and found liquid water or some kind of air, the pressure of water or air would be about 1.9698 psi x 10 = 19.698 psi or more air pressure than Earth surface. You don’t need spacesuit or pressure suit to breath any oxygen you got. Scuba gear works.
    Scuba gear doesn’t work on surface of Moon or Mars or in space.
    And if got liquid water, the water temperature must somewhere around the freezing point of water.
    Could be like diving in Antarctic waters.
    In terms of going to 100 km depth of water, it’s 1000 times more: 19.698 times 19,698 psi or 1,340 atm
    Or pressure of water at 13,400 meter deep on Earth. And deepest depth of ocean on Earth is about 36,200 feet or 11033.76 meters.
    Europa has more water pressure than Earth if it has a 100 km deep ocean.
    10 meter deep: 1.9698 psi and 73 meter = about 1 atm of pressure.
    When you dive 40 meter {131 feet} on Earth the effect in terms getting bends is equal/same 4 times 73 meters: 292 meter {958 feet}.
    With scuba any time diving more 10 meter one has to concerned getting bends- you can’t change depths quickly with Europa it’s 7.3 times further distance, that you likewise have be concerned about.
    It seems if swimming, you aren’t going able fast enough to “worry” about it. If were using a vehicle which could make go faster then swimming, then it becomes a concern.
    Also because low gravity you have less force of buoyancy- you can’t
    passively “float” towards the surface fast.
    So, roughly once adjust to whenever pressure it is, moving around will similar to moving around in Earth atmosphere.
    And in the boundary between ice and liquid ocean which might be under 5 to 10 km of ice. Though might be a small pocket
    in which ice is “only” 110 meters thick, as said above.
    This boundary could a place to make [or find] an “underground”
    Or said differently, all you need to do is add air- and air pressure will displace the water. Or if you make enough air one have vast cities areas under say 5 km of ice. And there could natural, gas filled caverns under the ice.
    Of course, Europa surface is quite “hostile” in terms of high radiation, but if you have hundreds meter of ice between you and the surface, then there is not a problem- though getting there and leaving is a issue/problem.

    • Alex Tolley May 27, 2021, 21:40

      Scuba tanks are filled with terrestrial air by simple compression. It is cheap, but the N2 will give you the bends if not careful. On Europa, without an atmosphere, you will not have an N2/O2 mix for diving. Either a scuba diver would have to risk pure O2 or use another mixing gas. H2 might just be a little dangerous. ;)

      If one really wanted to explore Europan caves or other features by diving, I suspect a hard suit might be a better idea, recirculating the gas mixture and scrubbing the CO2. It would be more like a spacesuit but would allow large depth changes to be made, and if the base habitat was at depth too, there would be no need for decompression chambers.

      However, as there is no obvious way to circumvent running the gauntlet of Jupiter’s radiation to reach the subsurface ice habitat, I suspect Europan diving will be a robot-only activity, although possibly managed by human crews stationed further out in Jupiter’s orbit, perhaps at Callisto, with a tolerable communication latency.

      I like the point torque_xtr makes concerning the subsurface topography. We really shouldn’t expect almost platonically smooth topography, but rather a topography allowed by conditions, such as seamounts. The terrain may prove more interesting than abyssal plains with occasional smoker vents.

  • Alex Tolley May 27, 2021, 21:17

    The paper’s model indicates that the hotspots from tidal and radiogenic heating are concentrated near the poles. Is this why the plumes on Enceladus are at the south pole? However, this article in SciAm: Where Are the “Hotspots” for Europa’s Purported Plumes? suggests no obvious hotspots on Europa were found, although new instruments might be more definitive.

    If there is life in Europa, it would be worth knowing what the nutrient flow rate is that would be needed to metabolically support any ecosystem.

  • David Herne May 27, 2021, 22:01

    Europa is surely one of the Solar System’s most exciting prospects for in situ study. However, Jupiter is two planets over from us and we’re looking at a 6 year journey (2024-2030) – crazy. I hope that my grandchildren’s generation will be able to look back and laugh.

    In his book ‘Unmasking Europa’, Richard Greenberg, Professor of Planetary Sciences, University of Arizona, demonstrated the possibility of liquid water rising fleetingly to the planet’s surface due to tidal cracking of crustal ice. It might be possible to drop a robotic subsea explorer into one of these temporary fissures.

    Europa beckons.

    • Paul Gilster May 28, 2021, 6:01

      Agreed! And I’ll second your reference to Dr. Greenberg’s book. It’s a fine study in great detail of Europan terrain and what it implies; he also makes a convincing case for relatively thin ice, as opposed to the views of, say, Pobert Pappalardo. I had the chance to have lunch with Greenberg shortly after his retirement, talking about Europa and things even farther afield. A fascinating man.

    • Andrei May 29, 2021, 13:31

      Europa certainly is the most exciting world in the solar system for such exploration. With the wildly volcanic Io, it was not difficult to imagine that also Europa would have some degree on vulcanism or smokers – either which would circulate nutrients and compounds needed both for the emergence of life, as well as sustaining it.
      And this has been the reason for me to advocate Europa exploration over any other body in the solar system for a long time.
      In addition, we can be more certain that any life on Europa have a separate genesis than in other localities. Since interplanetary transport is quite less likely to Europa than lets say to Mars. It will in short, most likely be unique.

  • Robin Datta May 28, 2021, 4:42

    If there is the good fortune to sample an ejected plume, let’s hope they’ll analyze it for biological life through its biosignatures including a peek down a microscope.

  • Michael Fidler May 28, 2021, 10:33

    If there are now or have been volcanoes in Europa’s oceans, could there be chambers of gas beneath the ice? Since we do not know what the core is made up of, could these gases be conducive to more advanced life? Io emits sulfur dioxide (SO2), sulfur monoxide (SO), sodium chloride (NaCl) but Europa would have more carbon and hydrogen compounds. Just a thought…

  • Edwin May 29, 2021, 6:23

    Hi Paul

    Yes I was looking forward to reading this one from you and the comments are interesting too.

    torque_xtr makes an interesting point of volcanoes reaching to the ice shell possibley something I had never thourght about before.

    The comments about pressure were also interesting too, I hope the lover gravity was taken into account there.

    Cheers Edwin

  • Adam May 31, 2021, 18:42

    Hi Paul
    A handy base of operations for exploring Europa would be the equatorial region of Ganymede, under its native magnetic shield.

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