Europa’s Acidic Oceans May Prohibit Life

Article written: 2 Mar , 2012
Updated: 23 Dec , 2015


The more we explore our solar system, the more we find things in common. Jupiter’s frigid moon – Europa – is about the size of our satellite and – like Earth – home to some very hostile environments. Underneath what is surmised to be an icy crust a few miles deep, Europa may possess an acidic ocean that could extend down as much as 100 miles (160 km) below the surface. We know from exploring our home planet that life happens under some very extreme conditions here… But what about Europa? What are the chances that life could exist there, too?

Check out liquid water on Earth and you’ll find some form of life. As a given, scientists hypothesize other worlds which contain water should also support life. According to recent studies, Europa’s ocean might even be saturated with oxygen – further supporting these theories. However, there’s a catch. Like Earth, surface chemicals are continually drawn downward. According to researcher Matthew Pasek, an astrobiologist at the University of South Florida, this could constitute a highly acidic ocean which “is probably not friendly to life — it ends up messing with things like membrane development, and it could be hard building the large-scale organic polymers.”

According to Charles Choi of Astrobiology Magazine, “The compounds in question are oxidants, which are capable of receiving electrons from other compounds. These are usually rare in the solar system because of the abundance of chemicals known as reductants such as hydrogen and carbon, which react quickly with oxidants to form oxides such as water and carbon dioxide. Europa happens to be rich in strong oxidants such as oxygen and hydrogen peroxide which are created by the irradiation of its icy crust by high-energy particles from Jupiter.”

Although it’s speculation, if Europa produces oxidants, they may also be drawn toward its core from ocean motion. However, it might be infused with sulfides and other compounds creating sulfuric and other acids before supporting life. According to the researchers, if this has happened for just half of Europa’s lifetime, the result would be corrosive, with a pH of about 2.6, “about the same as your average soft drink,” Pasek said. While this wouldn’t prohibit life from forming, it wouldn’t make it easy. Emerging life forms would have to be quick to consume oxidants and build an acid tolerance – a process which could take as much as 50 million years.

Are there similar acid-lovin’ lifeforms on Earth? You bet. They exist in acid mine drainage found in Spain’s Rio Tinto river and they feed on iron and sulfide for their metabolic energy. “The microbes there have figured out ways of fighting their acidic environment,” Pasek said. “If life did that on Europa, Ganymede, and maybe even Mars, that might have been quite advantageous.” It is also possible that sediments at the bottom of Europa’s ocean may neutralize the acids, even though Pasek speculates this isn’t likely. One thing we do know about an acidic ocean is that it dissolves calcium-based materials such as bones and shells.

It’s a lesson repeated on Earth…

Right now our oceans are absorbing excess carbon dioxide from the air which – when combined with seawater – forms carbonic acid. While it is mostly neutralized by fossil carbonate shells at the ocean’s bed, if it’s absorbed too quickly it can have some major ramifications on sea life such as coral reefs, plankton and mollusks. According to a recent study, this acidification is happening faster (thanks to human carbon emissions) than it has during four major extinction events on Earth in the last 300 million years.

“What we’re doing today really stands out,” said lead author Bärbel Hönisch, a paleoceanographer at Columbia University’s Lamont-Doherty Earth Observatory. “We know that life during past ocean acidification events was not wiped out—new species evolved to replace those that died off. But if industrial carbon emissions continue at the current pace, we may lose organisms we care about—coral reefs, oysters, salmon.”

According to this new research, our carbon dioxide levels have escalated by 30% in the last century. This means we’ve jumped to to 393 parts per million, and ocean pH has fallen by 0.1 unit, to 8.1–an acidification rate at least 10 times faster than 56 million years ago, says Hönisch. If this continues, the Intergovernmental Panel on Climate Change predicts the pH may drop as much as another 0.3 units… a drop that will constitute major biologic changes. While you might scoff at the extinction of a few forms of plankton or the annihilation of a small coral or shellfish, there is a ripple effect that cannot be denied.

“It’s not a problem that can be quickly reversed,” said Christopher Langdon, a biological oceanographer at the University of Miami who co-authored the study on Papua New Guinea reefs. “Once a species goes extinct it’s gone forever. We’re playing a very dangerous game.”

It may take decades before ocean acidification’s effect on marine life shows itself. Until then, the past is a good way to foresee the future, says Richard Feely, an oceanographer at the National Oceanic and Atmospheric Administration who was not involved in the study. “These studies give you a sense of the timing involved in past ocean acidification events—they did not happen quickly,” he said. “The decisions we make over the next few decades could have significant implications on a geologic timescale.”

For now, we’ll look to Europa and wonder at what may exist below its frozen waves. Is there an acid-loving form of life just waiting to bubble to the surface for us to find? Right now researchers are developing a drill which could assist in looking for extreme forms of life. The “penetrator” could eventually be part of a Europa exploration mission which could begin as early as 2020.

“Penetrators are the most feasible, cheapest and safest option for a landing on Europa today, and the knowledge to build those is there,” said Peter Weiss, a post-doc now at the National Center for Scientific Research (CNRS) in France. “Otherwise, we won’t have any confirmation on astrobiology on Europa — or maybe even in the solar system — during our lifetime.”

Original Story Source: Astrobiology Magazine. For Further Reading:

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15 Responses

  1. alan martin says

    It you add an acid to a basic solution shifting the pH closer to a neutral value the process is called neutralization

    • Member
      IVAN3MAN_AT_LARGE says

      Tammy was merely restating what the original article at had stated.

  2. andrew g says

    If the constituents of Earth’s atmosphere were in equilibrium and we’ve disturbed that by our actions then isn’t it probably already too late? If you push the system back you’re extremely unlikely to achieve the same state, a bit like trying to rebalance a pencil once you’ve knocked it away from the vertical.

    So we, and the plankton etc., are all doomed.

    • Torbjörn Larsson says

      The point of an oxygen atmosphere in the case of astrobiology is that it is _not_ in thermodynamical equilibrium for liquid water temperatures, so being an excellent spectroscopic signature of mature biospheres.

      I haven’t kept up with the observation, which if fact would be the larger effect of AGW to date, but I think the article understates it. Maybe I misunderstood, but I believed the change or the change rate was touted as the largest in ~ 300 My. Or as a comparison, about the time there have been complex land life.

      • Peristroika says

        Torbjorn, it’s LOSE not LOOSE. (Looz, not Looce) and
        We are certainly doomed as a species. The lifetime of an average mammal species is ~ 1 My.
        Hardly. C’mon now, are you comparing us to Giant Sloths and sabre toothed tigers? How much did they modify their environment? How much of the Earth did their species cover? How dependent on one food source were they? How resourceful and determined were they compared to a species that lives in caves, domes, houses, permafrost, underground, in sky scrapers, by itself, among millions, in deserts, rainforests, can genetically modify seeds, understands the nature of molecules, creates fire, fission, electricity, and yet still revels in the first steps of its young?
        There is nothing and has never been anything to compare with us. To use a tree shrew or pangolin or bat as comparison is ridiculous. Our will to live as a person is indomitable but our will to survive as a species will supercede even God’s (read: Reality’s) best effort to destroy us or our planet.

      • Torbjörn Larsson says

        I’m comparing us with the average mammal, but the number isn’t important. The point is that a species will disappear as it evolves into its descendants. There is no stasis.

        Even seemingly ‘static’ species are now believed to be replaced by similar looking ones. That is arguable of course, but it is not important to the point.

        it’s LOSE not LOOSE

        I was rushed, but the use is arguable, it works either way. Thanks anyway.

      • Astrofiend says

        This assumes that the sophistication of a species will necessarily correlate with its longevity; an idea for which I can’t really see a strong motivation nor precedent. If anything, there has never been a species so utterly dependent on such a fragile house of cards as us. I’m not saying we’ll go extinct (although we will either meet that end or evolve to some only vaguely recognizable form eventually), but the way we are going does not bode well.

        Devastation of forests, fisheries, overpopulation, deep food supply issues, watering down of the genetic pool for food resources, rampant pollution of the world’s oceans, rising ocean temp and acidity, climate change, strong suggestions that global weather patterns possess critical points etc. etc. etc. None of these would wipe us out, but the combination may send us back to the caves eventually if we don’t have the collective commitment to live in a lower impact manner.

      • super_earth says

        “The final global oxidation that ushered in large complex life is now theorized to have been caused by the first minute calcium skeleton sponges O. antigua”

        Very interesting. Could you show the paper where that hypothesis is elaborated?

    • Peristroika says

      Doomed implies an understanding of a place we’ve never been. You are extrapolating a possible future of many. We changed earth the first time we breathed. That hardly meant we were doomed. Change comes, change is inevitable with or without us. We, as the most adaptable species on the planet, have choice and as long as a dozen or so survive, like the few who crossed the arctic land bridge 20,000 years ago, we have the chance to do it all again.

    • Prof. Michael O. Zimmermann says

      You are absolutely right… we can’t go back to square ONE, because we can’t travel in time ;-). However, nature does have a way to recover… over a period of a few million years, AND probably without us!
      Homo sapiens is insignificant by any measure, even if we screw up a planet.

  3. Torbjörn Larsson says

    When they discovered the possibility of oxygen being generated at the surface (like the Dione results now being released) and brought down to Europa’s ocean, I didn’t think it would affect the geochemistry on such a global scale.

    However, I can’t see how this is more serious than discovering oxygen in the first place. If the oxygen generating mechanism was in place when Europa formed, and I don’t see how it wasn’t, the oxygen would have poisoned chemical evolution. So no life.

    If the oxygen generation was somehow delayed, the delay time until poisoning would have been ~ 1 – 2 My IIRC. The ~ 50 My year of rising pH would be a later, smaller concern.

    Also, besides an inflow of oxygen supplying energy for a later biosphere, there could have been hydrothermal vents throughout the biosphere history. Those happen to supply redox energy and – local pH differences. The latter would give refuges for life in a lowering (or raising) global pH environment.

    I am still thinking that the discovery of oxygen, first on Europa and now on Dione as well, means we can expect many ocean ice moons orbiting energetic gas giants to be sterile. But as far as I know, Enceladus plumes didn’t show this problem (to the resolution of the insensitive mass spectrometer), so it isn’t all gloom.

    • super_earth says

      Do not worry about the early oxidation of prebiotic chemistry:

      Richard Greenberg, the aiuthor of the study that found that strong oxydizers are produced in the surface of Europe and then are trasported downwards to the ocean, found also that:

      “he good news for the question of the origin of life is that there would be a delay of a couple of billion years before the first surface oxygen reached the ocean. Without that delay, the first pre-biotic chemistry and the first primitive organic structures would be disrupted by oxidation”

  4. ITSRUF says

    Without space travel, every species on Earth is doomed.

    • Stuart Saunders says

      If the space travellers carry there polluting ways, won’t they be dooming everywhere else they visit?

      Why don’t we just try to live within earths limits?

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