Onward to Europa

The oceans of Jupiter's ice worlds might be swimming with life — so why do we keep sending robots to Mars?

by 2700 2,700 words
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Europa, one of Jupiter's moons. Photo by NASA/JPL/Ted Stryk

Europa, one of Jupiter's moons. Photo by NASA/JPL/Ted Stryk

Lee Billings is a science journalist, whose work has been published in Nature, New Scientist, and Popular Mechanics, among others. His first book is Five Billion Years of Solitude: The Search for Life Among the Stars (2013).

The robots come to Mars out of a sky tinged peach from whirlwind-lofted dust. They cut through the thin, cold air in supersonic aeroshells and parachutes, making planetfall in bouncing airbag cocoons and bursts of braking retrorockets, bristling with cameras and spectrometers, antennas and manipulator arms. Some stay where they land; others rove for years on end. Sniffing the air, sifting through soil, wheeling across a cratered landscape, the robots doggedly seek any wisp of Martian moisture, like lost desert travellers dying of thirst. They are looking for life, following a strategy that NASA officials describe as ‘following the water’.

This strategy pays heed to water’s eerie harmony with life: wherever one is found on Earth, the other isn’t far behind. There are good reasons to believe that water is the ideal cornerstone of biology, not only on Earth, but elsewhere in the Universe. All you need to make it is hydrogen and oxygen, respectively the first and third most abundant elements in the cosmos.

In liquid form, water is unparalleled in its attunement to life’s needs. It facilitates the transmission of biochemical energy, nutrients, and waste. It shapes the structures and interactions of proteins and other macromolecules. It shields against hostile cosmic radiation, and it has a remarkably robust capacity for retaining warmth. Most strangely, unlike almost every other substance in the Universe, when water freezes, it expands instead of contracting, forming a protective, insulating shell of ice at its surface. This helps oceans, lakes, and other liquid reservoirs avoid freezing solid when exposed to prolonged cold.

For researchers who study Mars, following the water has paid off handsomely. Every mission sent to Mars seeking water has found it and, as a result, we now know that our neighbouring world used to be a warmer, wetter, more habitable place. Billions of years ago, that all changed, as the planet cooled and lost most of its air and water, and settled into a quiet senescence. But present-day Mars still harbours a slumbering aquasphere, locked in the ground as ice, which may stir every so often, erupting to the surface in evanescent briny flows.

Officially, the next stage of NASA’s Mars exploration programme is to ‘seek signs of life’, a phase that supposedly began in the summer of 2012 with the successful landing of the car-sized Curiosity rover. It’s true that Curiosity can sniff out organic carbon in samples of Martian rock and soil, but it mostly seems to be following the water, too. So far, it has rolled through what looks to be an ancient dried-up riverbed, and found evidence suggesting that some of Mars’s ancient water was fresh enough to drink.

Whether there is or ever has been anything on Mars to actually drink it is, surprisingly, not a question that Curiosity is well-equipped to answer, though it should have lots of time to try. Thanks to its nuclear power source, Curiosity could roam for at least 14 years, long enough to be joined by several more planned orbiters, landers, and rovers, bringing the total number of robots investigating Mars to perhaps a dozen. For the foreseeable future, Mars will be the focal point of our planetary science, dwarfing all other efforts to explore elsewhere in the solar system.

Our current explorations of Mars have become cautious and procedural, perhaps to a fault, as a result of past overreaches in the search for Martian life. The strategy of following the water emerged in the long aftermath of NASA’s costly and ambitious Viking missions, which landed on Mars in 1976, seeking life and finding none. Mission-planners controversially included cameras in the Viking payloads, inspired by none other than Carl Sagan, who noted half-jokingly that a lander focused strictly on microbial life would risk missing any Martian polar bears that might wander by.

Of course, when the Vikings landed, no polar bears showed up, and no microbes did, either. Twenty years later, the chastened Mars-research community was still smarting from Viking’s sting and NASA held a press conference declaring that some of its scientists had discovered ‘microfossil’ evidence for life in a Martian meteorite. The microfossil interpretation was disputed before the ink dried on the breathless newspaper headlines, and within a few years it had been decisively debunked, but not before spawning a flurry of funding, which helped to produce today’s bumper crop of Martian robots.

looking for water on Mars has become one of the most humdrum pursuits imaginable

Our obsession with Mars arises out of its similarity to Earth, and its nearness. Finding something clearly alien on the planet next door – some bacterium not built around DNA or RNA, for instance – would tell us that life arose independently on two separate worlds orbiting our solitary yellow star. We could no longer consider ourselves alone, for we would know with great confidence that life is a truly cosmic phenomenon, as inevitable in our Universe as the galaxies, stars, and planets themselves.

A strategy of following the water has become a necessary but insufficient placeholder for this grand ambition, and sadly we can now expect a decades-long interlude before the real story begins. The uncomfortable truth is that, despite the technical tour-de-force of our robotic reconnaissance, looking for water on Mars has become one of the most humdrum pursuits imaginable in all of 21st-century space science. It is the safest possible bet, the astrobiological equivalent of the bland-yet-filling casserole your in-laws sometimes make. Most news stories trumpeting yet another aqueous Martian discovery (or rediscovery) speak more to a collective public amnesia than to any paradigm-shifting knowledge being gained.

Indeed, scientists who specialise in Mars have been forced to dial down their dreams, hypothesising ever-smaller windows of opportunity for past life on the red planet, and ever more inaccessible refuges for anything now living there. Native Martians, if they exist at all, are most probably microbes clinging to life almost unreachably deep beneath the surface. This does not diminish the importance of exploring our neighbouring planet, but it must be admitted that there might well be more promising places to seek alien life. Indeed, if following the water is the prime directive in the search for extraterrestrial life, it increasingly appears that we should look beyond Mars to an icy moon of Jupiter called Europa.

It is a cold Sun that shines down on Jupiter and its moons, a dim bulb some four times smaller in size and about a 30th the brightness of the life-giving orb we see in Earth’s skies. For decades, most scientists thought that the water in Jupiter’s light-starved system would be granite-hard ice rather than life-giving liquid. But that view began to change in 1979, when NASA’s Voyager 1 and 2 spacecraft captured images of Europa as they soared past Jupiter on a grand tour of the outer solar system.

Europa is roughly the same size as Earth’s Moon, and some researchers thought that it too might have an ancient, inert surface scarred by giant impact craters. Instead, they were surprised to see Europa bearing a bright and icy crust relatively free of blemishes, a sign that its outer shell is active enough to hide the telltale craters that scar the face of a world over geological time.

they found signs of an electrically conductive layer beneath Europa's surface, precisely where a tidally heated reservoir of salty, conductive seawater would be

But Europa’s crust wasn’t wholly flawless – a jigsaw-puzzle network of cracks and fissures snaked across its surface. The cracks were filled with reddish-brown mineral salts that had welled up from the depths, and their spidery patterns suggested the whole crust was sliding over a deeper layer that was warm, wet, and slippery – a potential subsurface ocean. Investigators postulated that as Europa swung to and fro around Jupiter, tidal forces from the giant planet were causing the moon’s interior to flex, warming it through frictional heat like a paper clip bent back and forth in the palm of a hand. Though Europa's crust was young, an ocean beneath it produced by tidal heating could likely have existed nearly as long as the Jovian system itself, offering billions of years of time for life to arise and evolve in its depths. 

Confirmation of Europa’s ocean would not come until the mid-1990s, when NASA’s Galileo spacecraft slipped into orbit around Jupiter and began close-up studies of its most tantalising moon. It imaged ‘chaos terrains’ where upwelling molten material had ruptured the ice into jumbled slurries of slabs, like icebergs tumbling in a frozen sea. Later, when measuring Europa’s magnetic field, the spacecraft found global signs of an electrically conductive layer beneath the surface, precisely where a tidally heated reservoir of salty, highly conductive seawater would be.

If Europa is alive, if some biology dwells within those dark waters, the implications would be even more staggering than finding life on Mars. Our gaze would turn to Jupiter’s Ganymede next, and to Callisto, along with Saturn’s Titan and Enceladus, and perhaps even the dwarf planets such as Ceres and Pluto, all of which also likely harbour substantial subsurface reservoirs, heated through some combination of tides and radioactive decay.

And if water and life could exist there, why not in the hearts of large comets, before the Sun’s planets and moons even finished forming? Our solar system might have brimmed with hidden life for nearly as long as the Sun has shined, and ice-roofed worlds might be the default abodes for biology in the Universe. Life within a roofed world could proceed swimmingly against any number of otherwise-fatal cosmic calamities, whether being slingshotted into the interstellar dark as a rogue planet, or being bathed in hard radiation from a nearby supernova or burping black hole. We could then guess why, like our solar system, the Universe at large looks so desolate to us. In this scenario, most life, even if it had eyes to see, would never glimpse sky, stars, light, or fire, and would have scant hope of ever reaching what lies above and beyond its icy shell.

After the revelations of Galileo, a minor cottage industry arose among planetary scientists estimating the volume of Europa’s ocean and the thickness of overlying ice, all in hopes of pinning down what sort of life might exist in that dark watery world – and how accessible it might be to future probes. After more than a decade of debate, the general consensus is that Europa’s abyss is more than 100km deep, holding double or even triple the amount of water in Earth’s oceans.

Whether the ice is thick or thin, the key question facing astrobiologists is really whether sufficient free energy exists within Europa’s sunless depths to support a biosphere – for life, if it is anything, is hungry. If scant useful energy is available beneath Europa’s ice, as many researchers suspect, the ocean could at best be a sparsely populated habitat for alien microbes. But if energy is plentiful, Europa could boast rich ecosystems of complex multicellular organisms – perhaps even something as magnificent and fearsome as Earth’s predatory deep-sea giant squid.

Europa probably offers a rich haven for extraterrestrial life right now

Based on measurements of its density, Europa should have an iron core sheathed by a mantle of silicate rock. This rock likely constitutes the bottom of the ocean, and is the probable source of the mineral salts that well up to the surface – a useful influx of chemical energy and raw construction materials for life. On Earth, communities of organisms thrive on the sea floor, utterly isolated from the surface and sunlight, living off chemical reactions driven by hydrothermal vents. Relocated to hydrothermal vents in the Europan depths, they might conceivably thrive there, too.

Many scientists suspect such sea floor oases were where our planet’s life first emerged from inanimate matter. If the overlying ice crust is thin and mobile enough, useful energy could also trickle down from above, via heat and ejecta from the occasional cometary impact, or from the upwelling mineral salts that oxidise at the surface before slowly filtering down through fractures in the ice. It increasingly seems that, unlike Mars, which, just maybe, might have been able to support a robust biosphere deep in its geological past, Europa probably offers a rich haven for extraterrestrial life right now.

So why then, one might wonder, with so much promise for life on Europa, are we lavishing attention on Mars? Why are we chasing ice crystals underneath a desert instead of seeking out alien seas?

For one, Europa is much harder to get to than Mars, and much less hospitable when you arrive. Current space-based solar power systems can barely generate sufficient electricity from the sunlight available at Jupiter, and the meagre nuclear power sources presently available to civilian space agencies are, by and large, already committed to upcoming Mars missions. Due to its powerful magnetic field, which acts like a giant particle accelerator, Jupiter also creates an extremely hazardous radiation environment at Europa’s surface, sufficient to give a spacesuited human a fatal dose in a matter of hours. Even a robotic orbiter or lander must be heavily shielded, at great expense, if it is to withstand such bombardment.

There is also the question of penetrating Europa’s icy shield. Perhaps abnormally thin regions of crust could be found, allowing a robotic submersible to be slipped down a borehole made with mechanical drill or a nuclear-powered melter, but the cost would be staggering – imagine the expense and difficulty of setting up a deep-sea oil-drilling platform not in the Gulf of Mexico, but on another world. In an earlier time of more plentiful funding, NASA estimates guessed that even a simple Europa orbiter – never mind any tunnelling landers or radioactive cryobots – would cost nearly $5 billion, though later efforts suggested a bare-bones mission could be had for approximately $2 billion.

Fly a spacecraft through or near a plume, and, who knows, you might even catch a flash-frozen fish

Yet the more closely we examine Europa, the more its complexities seem to offer a cheaper, faster pathway to knowing its ocean. Late last year, a team of researchers used the Hubble Space Telescope to detect plumes of water vapour gushing some 200km out from regions around Europa’s south pole, venting an estimated 7000kg of water per second into space. The plumes seem to occur when Europa is at its farthest orbital separation, suggesting they’re driven by fissures that open and close, cyclically, as the moon flexes from Jupiter’s tidal pull.

Whether the plumes are connected to the deep ocean itself, or to a population of smaller, sea- or lake-sized reservoirs closer to the surface, remains unknown. What’s certain is that all that vented water should be carrying contaminants, too – vestiges of other physical, chemical, potentially even biological processes, taking place deeper within Europa. Fly a spacecraft through or near a plume, and, who knows, you might even catch a flash-frozen fish.

Only one mission capable of the task is presently funded, the European Space Agency’s Jupiter Icy Moons Explorer (JUICE), slated to launch in 2022 and arrive at Jupiter in 2030. But JUICE won’t orbit Europa, and might only encounter the moon twice on its three-year mission, which might not be enough to sample the transient plumes. At the urging of the US Congress and the Obama administration, NASA is now studying the feasibility of its own Europa mission. Yet the very same politicians encouraging NASA to look to Europa have failed to give it the true freedom to do so: budgetary squabbling has reduced NASA’s targeted pricetag for a Europa mission to less than $1 billion, which is less than half the cost of its previous estimates for a bare-bones mission.

Meanwhile, Mars beckons from right next door, and we heed the call, like young children setting out to see the wide-open world by overnighting in a backyard tent. Perhaps it can’t be helped. Perhaps it shouldn’t be. Beyond the pressures of time, energy, and money that make exploring Europa seem so prohibitive, there is also the problem of human psychology.

Even if Mars proves totally, irrevocably dead, one can still squint up at its ruddy disk in the night sky, and envision a better future for it. Someday, humans might walk there, perhaps even live. No one has such dreams for Europa. If Mars is a warped mirror we stare into, while imagining ourselves as explorers in some pleasantly familiar frontier future, then Europa must be a locked door, or maybe a matte-black monolith, cold and indifferent, an abyss that might, some day, gaze back at us, if only we could first convince ourselves to look.

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  • Toroid

    Great Article - and much needed. There isn't any real doubt that the most exciting places in the solar system (after earth) are the icy moons of Jupiter, Saturn and even Neptune. My favourite has to be Titan. A moon with an atmosphere 5 times that of earths, surface rivers, lakes, and seas (OK they are of methane, but still..) and a sub-surface ocean like Europa. Also, much less trouble with radiation compared to Europa. Twice the distance though.

  • Karen Ercolani

    Ganymede boasts a lot of water, perhaps 25 times the volume of Earth's oceans. Its oceans are estimated to be about 500 miles (800 km) deep.

    500 miles deep?



    • G

      Water + complex chemistry + an energy source = life.

      With that much water, there's a high probability of macroscopic organisms.

      What I wouldn't give to see Ganymedian fish. We could have gone there by now, but for the idiotic propensity of humans to bicker and fight over whose precious genes are the most-precious of all, and who gets to dominate who, and all of the destructive and squanderous insanity that follows.

      • Lexi Mize

        Water + complex chemistry + an energy source != life

        If your original equation were true, Earthly scientists would have created it already. They have not, and probably will not.

        • G

          Carbon granules + metal diaphragms + electromagnets + metal diaphragms + batteries + connecting wires = telephones. The fact that it took humans about 1900 years after the birth of Christ to figure that out did not make it impossible.

          The reason we have not yet created synthetic life is that we do not yet understand the process of abiogenesis. But a large number of smart people are working on it, so it cannot be ruled out a-priori. Once we get it, it will be as retrospectively obvious as the telephone.

        • G

          Well guess what? We just did it. Results announced about two days ago.

          Synthetic DNA, inserted into suitably modified bacteria, and capable of being reproduced. See headlines on various science sites over the past few days.

          • Lexi Mize

            Modification of existing life is not recreating the "miracle of life." This is not even close to that process.

            Of course nothing can be permanently ruled out. As a base of development, 50,000 years of the existence of a higher life-form, only 100 or so of which has seen true technological advancement, is just a blink of an eye compared to the future timescape in which abiotic life may be created. Who can know? Nostradamus maybe. I wouldn't put it past humans to some day create life. Yet even as an a-theist, I still believe that spark that defines life is one that may elude us.

  • gvanderleun

    Hey, hold it there cowboys..... you have already received these very SIMPLE instructions.


  • Michael Hanlon

    A very good analysis. Frozen Europan fish! Love it ...

    Mars wins, as you say, because getting there is relatively cheap, and Mars occupies a powerful place in popular culture. It is very important that Mars is the only celestial body aside from the Moon whose solid surface can be seen easily from the Earth. Mars is a place; Europa is a pinprick of light in binoculars.

    The current Mars strategy is a bit odd- throw a load of robots at the place to look for two-billion-year-old lakebeds. I have asked NASA why it gave up looking for extant life and have never had an entirely satisfactory answer. Many people think that the Viking experiments DID find life, or at least something suspiciously like it. The failure to simply rerun the Viking tests (updated, with better equipment and the failings of the originals addressed) on a later lander seems very strange. Curiosity could certainly have carried a life-detector.

    My suspicion is that a confirmed negative finding (and most astrobiologists think that the Vikings found nada) would switch off public (and political) interest in Mars and hence cut the funding altogether. But keep on looking for water (on a world where we have known there is probably a great deal of the stuff since 1666) will always get 'positive' and newsworthy results.

    Europa, and also Titan and Enceladus, would make excellent targets. But they are insanely expensive to explore. You could just about get away with solar power at Europa but at Saturn, no way. My favourite would be a Titan balloon. In that gravity and atmosphere it could stay up for years, drifting around and maybe landing every now and then to take pictures and samples.

    A comprehensive exploration of the Jovian/Saturnian systems will have to wait until the 2070s or later, long after most of us are dead. Which is a shame. I certainly don't see anyone drilling through the Europan ice this side of the Centenary of the Voyager flybys. Not unless we get really lucky and Cassini or Juice spot something really weird, or we have some sort of technology breakthrough.

  • http://almashriq.hiof.no/lebanon/300/320/324/324.2/hizballah/ Sons of Ares

    Shorter version: Mars sucks, I hate it, it's boring, let's contaminate Europa.

  • G

    Excellent article, and we need more of this sort.

    The point of going to Mars is to eventually build a full-time colony there, leading to a self-sufficient Martian civilisation with (eventually) the capacity to build its own interplanetary spacecraft. This doesn't require terraforming but could be done 'under glass,' in domed excavations with contained atmosphere. Earth and Mars would be independent planets but closely connected, in the manner of the UK, USA, Canada, Australia, and New Zealand.

    This is the first step toward becoming a cosmic civilisation: not only interplanetary but interstellar.

    We are virtually assured of that outcome just as long as we don't destroy ourselves such as through climate change sufficient to crash technological civilisation. In other words, all we have to do is evolve culturally just a wee bit more, and we will have the means at our disposal to persist and evolve until the last star blinks out in our galaxy and possibly in the observable universe.

    That said, Europa is a must-do destination, worthy of whatever investment is needed to make it succeed. Knowing what we know now, there is no excuse for turning our backs on this.

    The discovery of life on Europa would immediately answer one of our most fundamental questions: Earth-like biology or something else?

    The yearly budget for NASA is approximately equal to the yearly expenditure by Americans on video games. Meditate on that.

  • bilejones

    Wonderful, informative piece except that the assumption seems to be that tax-payer dollars will somehow be involved.

    • G

      Yes, taxpayer dollars will be involved.

      Taxes are the price-tag for civilisation, on Earth, as it will be in the proverbial heavens.

  • Jorge

    I already saw what's gonna happen on Europa Report...please make it happen!!!

  • jon

    there is life on mars fools. nasa is just going to coverup whatever they find anyway.

    • G

      Not even wrong.

      if NASA discovered microbes on Mars, it would be the headline news story of our lifetime. The demand for further exploration of Mars and the outer planets and their satellites would be unstoppable. This would also produce a science renaissance that would (one can hope, anyway) sweep away the present swamp of obscurantism and anti-science attitudes in the US.

      • JaiGuru

        This. It's ludicrous to suggest NASA would cover it up, even if they
        were under orders to do so. This isn't the cold war. There's not just a
        lack of public support for the organization but a growing hostility
        towards it for the gross resources it requires to do even basic things
        in an age when surplus is threatened to be a thing of the past.

        Life on Mars would give NASA the ultimate trump card to strong arm congress into near limitless funding. The public would do an immediate 180 and demand it themselves. It would literally become a ballot issue in the congressional elections.

        • G

          Though, it could become the cold war again, or something like it, depending on what happens between Russia and Europe/UK/USA. At minimum, an unpleasant attitude between Russia and the rest provides an incentive for Europe/UK and the US to have non-Russian launch capacity.

          Right now, here in the US, that means SpaceX, and Elon Musk is a goodguy-capitalist genius with his eyes set firmly on Mars. Once he starts carrying humans to the Space Station, that will be the green light for him to develop the capacity that leads to the Moon and to Mars via Phobos.

          A reasonable combination would be: NASA doing the research missions, and private-sector companies such as SpaceX doing the missions for which the contracts with NASA would be profitable to their investors. The success of the corporate space sector would encourage funding for NASA by way of the well-known precedent that government R&D leads directly to technologies that fuel new startups.

          The problem with landing humans on Mars is the 'landing' part, on a planet with too much gravity and too little atmosphere for the well-tried approaches to work. This calls for some clever new tech, but fortunately no new fundamental science. But if we can get humans on Phobos operating robotic devices on Mars, we can explore Mars far more rapidly than at present when C-lag is such a major inconvenience, so even a Phobos mission will be a major boost for Mars science.

          Meanwhile China's going to become a substantial presence in space, and India is set to join the club pretty soon. I'll admit to not knowing where ESA is going as far as rocket development is concerned, but I could look it up easily enough.

          There are numerous routes that could lead back to a substantial increase in space activity. Any one of those could do it. An unequivocal discovery of bacteria on Mars would be the most certain way, but there are others.

  • http://avangionq.stumbleupon.com/ AvangionQ

    The oceans of Europa hold such possibility. If life is found to have originated separately at least twice in our solar system, it would likely mean that life is heavily prevalent in the universe and well worth seeking out.

  • JaiGuru

    When you start with a mistaken premise you inevitably arrive at mistaken destinations. The whole "searching for life by following the water" schtick isn't NASA's real goal. That's just what they publish in a vein bid to keep an increasingly disinterested public's attention because social clout directly equates to continued funding for the organization. NASA's mission is two part: Chemical and spatial analysis, and material synthesis. Nothing else. You have watched too many episodes of Star Trek. You have confused a tech flavored fantasy for real life potential to clownish results.

    I'm sorry, but life isn't a movie and our motivations for doing these things have little to do with the public's grand case of the feels for finding ET. I am disappointed in this too, I share those feels. But I know enough not to let my emotions confuse my head and trick my eyes.

    • G

      Inspiration and aspiration are necessary for motivation.

      If ours was a perfectly rational species, it would be possible to plan long-term and the public would accept the fact that progress occurs over the course of many many lifetimes.

      But if ours was a perfectly rational species, humans would not be fighting over whose precious genes are the most precious, or over who can accumulate the largest collection of private jets and liner-sized yachts, or over who can dominate the largest number of other humans. Nor would we be facing +2 celsius, much less +6.

      Personally I'm thinking it could take 6,000 to 10,000 years before the launch of the first interstellar colony ship. Between now and then we have to deal with achieving a sustainable global society, an end to warfare, and sufficient global surplus to support the necessary efforts along with all else that will be occurring between here and there.

  • Lexi Mize

    Humanity needs an off planet repository for itself. That is the reason for Mars colonization.

    Have you read the contrarian position to hoping for life on other planets, other systems, other galaxies? No other discovered life means humans have NOT been selected for Great Filter elimination. Fermi's paradox anyone? As soon as we start finding any type of life, other than Earthly life, then we've automatically discovered evidence of our probable doom.

    • atimoshenko

      Well, not any type of life - only self-aware, tool-enhancing life. After all, out of the billions of forms of life that have emerged on Earth, self-aware, tool-enhancing life emerged exactly once.

    • G

      Too many logic leaps for my taste.

      I'd rather make only one, until we have sufficient empirical data to justify making any more: that the conditions favorable to life occur frequently enough that the universe is likely infested with it. That justifies the empirical search, including the search for intelligent life. After we've searched for long enough, and in enough different ways, to have covered a substantial portion of the observable areas of our galaxy, we can start coming to conclusions.

      I don't see the link between the absence of affirmative data by now, and any implication for whether humans will or will not not persist long enough to develop an interstellar civilisation.

      And I especially do not see any basis for asserting that discovery of life beyond Earth implies that we are doomed to destroy ourselves.

      The sample sizes are too small now, and they will be too small for the foreseeable future including if affirmative data are collected, to draw any viable inferences about the future of humanity.

      On the other hand, if the mythical Grays landed in a suitably public place and told us that their survey of a few hundred other intelligent civilisations shows that we have X probability of destroying ourselves, that would be a sufficient data set;-)

      And on the third hand, we know darn well what our self-created existential threats are:

      1) Climate disruption leading to collapse.
      2) Overpopulation and overconsumption generally, leading to overshoot and collapse.
      3) Nuclear war on a large scale.
      4) Biological war on a large scale.
      5) Cyberwar on a sufficient scale to permanently disable national electric grids.

      And we also know pretty well the factors that are creating those threats:

      1) Economic greed.
      2) Genetic greed (competitive reproduction).
      3) Vindictiveness and vengefulness.
      4) To which I would add: the unrecognised neuropsychiatric pandemic that consists of inadequate functioning of satiety feedback.

      All we are lacking as a species, so far, is the collective will to deal with these things decisively and conclusively. And no amount of data on life elsewhere or the lack thereof is going to predict whether we do or do not develop the needed collective will.

      • Lexi Mize

        My post was meant to have others search for The Great Filter papers that have popped up recently. I should have been more direct.

        But primarily the paper by Nick Bostrom linked internally in that article. Although Bostrom's paper is 8 years old it still lays out a solid argument against life everywhere philosophy most (including myself) have held.

        Of course the jury is out and will probably be forever out on the definitive answer about exo-life in the universe. Yet, I've changed my opinions, primarily due to Bostrom's argument as well as other data I've collected over the years. Earth is unique. Life is not common.

        • G

          Excellent, now we're talking. I've opened your link, and another that it led to (search for ET life likely to be fruitless), each advocating positions that are opposing my positions on these issues. Oddly enough, I actively seek out contrary positions, as a way of falsification testing of my preferred hypotheses. Frequently I change or alter or update my beliefs in accord with empirical facts and well-reasoned arguements.

          So I'll go have a good read or three over there, and see what happens. If they persuade me to change my working hypotheses or opinions (or even if they don't), I'll post here in reply to your comment above. (Plus or minus this page being broken which is why I haven't found your comment until now; Aeon.co's webmasters need to take a look at this, often the comment sections become inaccessible past a certain length, due to getting hidden behind the banners in the section below).

        • G

          Reply #2 to Lexi Mize (the first appears below this one, but this comment system appears to arrange them in reverse order):

          I read the first linked article, more to come, but I figured I'd get back to you on this first. The Fermi Paradox and Great Filter theories by themselves don't persuade me (and I've been aware of them for years, though I haven't read Bostrom's paper, which I just found by following links from your links, and will read it soon):

          SETI and similar efforts assume electromagnetic communication using presently known radio frequency means. We can't rule out other means of communication, some of which are within present physics (e.g. laser) and some of which may arise from new physics.

          We have only been actively searching for ETs for about 50 years. It's premature to draw conclusions of any sort from the data thus far, and counterproductive to draw conclusions that would lead to abandoning research. The physics community presently recognises the need for 'new physics' to address certain fundamental issues, and with new physics will come new technology, including new theoretical means of communication and observation. A minimum we should continue the research through the stage where we are capable of detecting the use of communications means that could use next-stage physics.

          The Great Filter arguement can reasonably be reduced down to something we have already observed: natural selection favours prolific breeders, which in turn are subject to population overshoot and collapse. Thus far humans have followed that course, with exceptions for cases of societies that have been economically secure for two generations or longer (e.g. the at- or slightly below-replacement level reproduction in prosperous societies).

          We can reasonably assume that since physics and chemistry are almost certainly uniform throughout our observable universe, there will at least be _some_ uniformities of biology. Selection/reproduction dynamics are among the elements of biology that are likely to be uniform or at least reasonably so. Thus there is a high risk of overshoot & collapse on the part of organisms generally, and intelligent species as well. This would tend to reduce the number of intelligent species that persist long enough to achieve high technology civilisation including interstellar travel.

          However, 'reduce' is not the same thing as 'eliminate.', so the net result is only that there will be fewer (rather than zero) interstellar civilisations.

          Lastly, I'm inclined to believe that we tend to underestimate the timeframe needed for interstellar migration. From where we are at present I would say it will take another 6,000 to 12,000 years before Earth-originated life is established as a viable civilisation in another star system, assuming we continue space exploration and development at even a moderately accelerated pace compared to at present. Even if there is a decline in time needed to establish each additional 'colony,' the early part of the growth curve will look relatively flat (though any 'rate of growth' is actually an exponential function). Here we're talking about hundreds of thousands of years, potentially millions of years.

          If that's the case, _and_ (assumption but none the less I think a reasonable one) Earth is unremarkably typical, then if we had 'perfect knowledge' of our galaxy, we would find that other interstellar civilisations are at early stages of development. In that case it would not be surprising that we had not found them yet.

          Lastly, at this point we have the means to handle all of the high-probability existential threats we presently face, so whether we 'pass the cosmic Darwin test' is up to us. We can achieve sustainability, we can set up a viable space defence against asteroid impacts, we can arrive at a global deterrence against biological warfare and limit our nuclear weapons to a 'neutral deterrence' role. We can switch from 19th-century energy sources to 21st-century energy sources and thereby solve the climate crisis. We can produce sufficient global prosperity and equality for women, that the birth rate will naturally arrive at a sustainable level for zero population growth. We can shift the economy to a steady-state system without foregoing the benefits of free enterprise or the benefits of social welfare. We can do all of these things if we have the will.

          And doing those things, I believe, will overcome the Great Filter. Admittedly this is a difficult leap. But no more difficult than nature has already bridged numerous times, from the leap that developed life itself, to eukaryotes, to complex multicellular life, to consciousness, then intelligence, then culture, then rudimentary tech, then science, and lately advanced tech. Each of these was a leap past a Great Filter. The next leap will be to the kind of sustainable global culture needed for humans to persist on Earth as long as the physical conditions allow: and that leap will also enable intelligent Earth-originated life to go interstellar and persist until the last star blinks out.

          So onward to Bostrom and let's see if he can persuade me otherwise.

          • David Malek

            More to your point, even in our own galaxy, if there is (or has been) a mere 6000 light year from us who have mastered the science of electromagnetic 1000 years ago, it would take another 5000 years to receive any sign of the signals they have generated.

        • Lexi Mize

          @G, First off, thanks for the polite interchange.

          Secondly, I've not entirely "changed my mind." I've put on this alternate view hat, completely, to see how it fits. So far, it's snug and comfortable, but is causing this itch in the back there. And of course this itch has a simple cause, one sample does not a statistic make. We have no choice but to base our projections of life in the universal on conjecture. Anthropocentric constraints dominate every extrapolation we have ever made about Earth's singular status or populous participation in the Universe's life party. No rational mind can possibly take a rooted stance to side with one or the other.

          The wikipedia article on Fermi's Paradox is actually quite fair in this regard. It also is a worthy read.

          That said I put together another narrowly focused position supporting The Great Filter / Fermi's Paradox here:


          (I invite you to take your well stated arguments and critique and create your own post on the topic. Buried comments, of excellent caliber, in any site, are no place for proper exposure of one's ideas.)

          You've prompted me to take my collection of Drake equation parameters and formalize them into a loose list. When finished they'll be posted to that wordpress site.

          Hey, thanks again for your efforts. I do still have a tendency to believe in your premises, but also lean to the Great Filter side too. Perched on the fence I'll sit, probably forever.

  • Dave

    Ok, I don't understand why you can't just have a simple lander and rover on Europa (obviously heavily shielded for radiation) and just observe what is on the surface. If Europa is continuously upwelling ice that used to be water from an ocean below... (sure, we would be observing what happened a few million years prior to reaching the surface)...wouldn't any microbial evidence present itself inside the surface ice? Thereby eliminating the need to drill miles down or fly through plumes?
    What am I missing?

    • Alex Musso


      See the above symbols for why NASA isn't sending a rover to Europa.

  • Wayne Martin

    My complements! You write absolutely beautifully, not only is your style of writing free flowing and natural the way that you pack information into your article is that of a child's wonderment and inquisitiveness after gazing into the heavens for the very first time!

    This is simply one of the very best articles I have ever read and thank you for taking me away with you on your journey!!! What a pleasure!!!

  • Luke

    I would just like to thank you for this truly outstanding piece of writing. The merging of beautiful prose with incredibly interesting content can be thrilling. And this is an example. Wow.