When will we find life in space?

By Phil Plait | August 23, 2012 6:51 am

[The article below was originally posted on the BBC Future blog, and was titled "Will we ever… find life elsewhere in the universe?" I’m reposting it here because, oddly, the BBC page is only readable for people outside the UK! It has to do with the BBC rights and all that. But they gave me permission to post it here, and since I thought it was fun and provocative, I figure y’all would like it. Enjoy.]

Will we ever… find life in space?

One of the reasons I love astronomy is that it doesn’t flinch from the big questions. And one of the biggest is: are we alone?

Another reason I love astronomy: it has a good shot at answering this question.

Even a few decades ago hard-headed realists pooh-poohed the idea of aliens. But times change, and so does science. We’ve accumulated enough data that makes the question less far-fetched than it once was, and I’m starting to think that the question isn’t "Will we find life?" but rather "Which method will find it first?"

There are three methods that, to me, are the front-runners for finding life on other worlds. And I have an idea as to which one may find it first.

Life on Mars?

The first method follows the principle that when you’re looking for something, it’s best to start close to home.
We know of one planet that has life: Earth. So it makes sense to look for other places with Earth-like conditions: that is, liquid water, oxygen in the air, nutrients for growth, and so on.

The most obvious place to look is Mars. At first glance it appears dry, cold and dead. But if you can see past that, things start to look up. The polar caps, for example, have lots of frozen water, and we’ve directly seen ice at lower latitudes on the Red Planet as well – meteorite impacts have left behind shiny craters, digging up fresh ice from below the surface.

Several Mars rovers and landers have uncovered tantalising evidence that liquid water might flow just beneath the surface, but we still lack any conclusive evidence. However, if you broaden your timescale a bit, there is excellent evidence that in the past – perhaps a billion years or so ago – our neighbouring planet had oceans of liquid water and thicker air. In fact, conditions were pretty good to develop life as we know it even before it popped up here on Earth.

It’s entirely possible that life got a toehold (or pseudopod hold) there long ago, and died out. If that’s the case, we may yet find fossils in the Martian rocks. Again, there’s no conclusive evidence yet, but we’ve literally barely scratched the surface there. Now that it has successfully landed on Mars, we have the exciting possibility that the plutonium-powered, car-sized Curiosity rover will soon use its on-board laser and other tools to crack open and examine rocks in the Gale Crater, which were laid down billions of years ago in the presence of liquid water.

And Mars isn’t the only possibility in our solar system. Liquid water exists inside Saturn’s moon Enceladus, where geysers of liquid water erupt from deep canyons at its south pole. Energised by the gravitational tug of the giant ringed planet itself, the interior of Enceladus may be a vast ocean of liquid water even while the surface is frozen over. That doesn’t guarantee we’ll ever find alien fish swimming that moon’s seas, of course. But it’s an interesting place to look.

Europa, a moon of Jupiter, almost certainly has an undersurface ocean as well. If you relax your constraints even more, Saturn’s moon Titan has lakes of liquid methane and ethane on its surface, too. The chemistry for life would be different there – it’s a rather chilly -180C on the surface – but it’s not impossible to suppose life might arise there too.

Finding out whether this is the case means getting up close and personal. We’re doing that for Mars; however, the likes of Europa and Enceladus may have to wait a decade or four.

Phone home

But maybe we don’t have to go anywhere. Instead, we might be able to sit here and wait for alien beings (of whatever form) to message us.

BBC Future has created an interactive Drake Equation calculator. How many alien civilizations are out there? Plug in some numbers and find out!

SETI is the Search for Extraterrestrial Intelligence, and its name tells you its story: it’s a group of astronomers looking for signs of intelligent life in space. They use various methods to look for advanced aliens, but the most promising one is to listen for any messages sent across the skies.

The basic SETI assumption is that aliens are out there and want to contact us. If that’s the case, there’s a good way they can signal us: radio waves. They’re the perfect medium: they’re cheap, easy to make, easy to encode with information, they travel across the whole galaxy unimpeded, and they move at the speed of light, the fastest thing we know. So SETI scours the skies looking for radio signals from ET.

They haven’t found anything yet, but as SETI astronomer Seth Shostak points out, we’ve just started looking. There’s a lot of galaxy and a lot of radio wave frequencies to sift through. But our technology gets better all the time, allowing for more sensitive searches. According to Shostak, if they’re out there and currently sending signals our way, we should have an answer one way or another in about 25 years given the way things are going.
I think SETI is a good idea. In a practical sense their engineers are advancing our radio technology and signal processing, and philosophically I think it’s interesting to listen for alien signals. But I do wonder about the basic assumption that aliens are out there and want to contact us – it’s a big leap, and based on our own human motivations. So while this is certainly worth the effort, it’s hard to know if it’ll pay off, and the 25-year deadline reflects that.

But I suspect another method may have the edge.

New world order

For a long time, we only knew of nine planets (including Pluto, though this was downgraded from its planet status five years ago), and only one that could support life. Then, in 1995, astronomers found the first planet to orbit another sun-like star. The planet wasn’t like ours at all – more massive than Jupiter, and orbiting so close to its parent star its temperature is over 1,000C. But it was a watershed moment. We finally knew that other planets exist.

Since then, NASA’s Kepler space telescope, the European Space Agency’s Corot mission and ground-based instruments have found nearly 800 other planets, and that number grows every week. We know of enough planets orbiting other stars that we can actually start to extrapolate some numbers: it looks like approximately half of all stars in the galaxy have planets, and planets may in fact outnumber the 200 billion stars in the Milky Way.

We still don’t know how many of these worlds are like ours, but it seems like it’s a good bet the number is in the million, if not billions. We’re finding smaller and smaller planets all the time, and statistically speaking Earth-sized planets should be fairly common.

The big question is how many of these have life? We don’t know. But consider this: we have evidence that life on Earth started almost immediately after its surface was cool and stable enough to allow it. For three billion years that earthly life consisted of one-celled organisms, and it’s only relatively recently that these evolved into the type of multi-celled creatures that now inhabit every niche of this blue planet.
It means that any Earth-like planets we find may be populated by… yeast. But that counts. It’s life. And life does something special: it ingests chemicals and excretes other chemicals.

Tell-tale signs

One such chemical is oxygen. On Earth, we breathe it in, but plants breathe it out. There’s a lot of it in our air; our atmosphere is more than 20% oxygen. If we found a planetary atmosphere with lots of oxygen gas, that would almost certainly be an indicator of life.

As it turns out, we’re on the verge of being able to do just that. Planets are dim and huddle close to their stars, but there are techniques to separate the light from the two objects. Oxygen has a signature, like a fingerprint, that can be detected in that light. It will take an extremely sensitive telescope and very clever techniques to see it, but we have the technology now to build such machines. One such is the James Webb Space Telescope, due to launch in 2018. It should be able to detect oxygen in an alien planet’s air. And many other instruments are being planned and built that can carry out similar observations.

Our technology is getting so good so quickly that finding alien biological atmospheric signatures is probably our best bet. To me, the numbers add up better than for the other strategies: there must be lots of this type of planet out there, life seems to arise easily, and biology messes with a planet’s chemistry in a detectable way. We don’t know if Mars or those watery moons have life at all, and even if they do it could take a long time to find it. And who knows if smart aliens are out there, and want to talk to us? But it may only be a few more years until we point a telescope at a fleck of light, absorbing those photons one by one, sifting through them, and finding in them – literally – the breath of life.

So when will we find life in space? If it’s out there, then my hope is: very soon.


Comments (44)

  1. Chris B.

    Thanks for seeking and receiving permission to repost this. I’d been curious about its content since your first posting a couple weeks back.

    Any chance they’ll also allow you to repost “Will We Ever Live on the Moon?” from June?

  2. Sam G.

    Great post, BA. Like you, my hope for finding life on other planets involves improving our ability to analyze exoplanets to determine if they could support life. I’m less interested in finding sentient aliens (partly on account of the fact that we as a species can’t even accept the existence of humans who think differently yet), but rather in hopes that we’ll find another world for humanity to someday call Home.

    I’d lost my love for space exploration somewhere along the years. Your blog–especially posts like this one–have brought it back. Keep reaching, keep teaching.

  3. Marc JX8P

    What I am really curious about is how the amount of information scales that space telescopes can see. For example, if the James Webb with its 5 x larger mirror than Hubble can see signs of Oxygene, what kind of information could we get of exoplanets if we had a space telescope of say 100 x Hubble format?

  4. Phil

    Paul Gilster over at http://www.centauri-dreams.org/ posted some good stuff about detecting ETI space vehicles. Three part series posted over the last three days; talks over detecting dyson-like vehicles exhaust, detecting the bow-shock of magsail brake, wormholes, and world ships. Great addition to Phil’s article above.

  5. Hmmm. What’s worse – not knowing whether there is life elsewhere, or getting such a tantalising yet incomplete glimpse in the spectra from distant planets, knowing we’ll not ever be able to go there to see what the life is actually *like*?

    I’m being facetious – if we *are* able to detect biosignatures this way, it will dramatically alter our ability to define the conditions under which life can evolve on planets, and let us start putting some real stats into the Drake equation. Indeed, on the subset of planets that have life in the first place, we may be able to detect other signatures, such as those left by intelligent life. Listen super-close with radio telescopes etc.

    And of course, somewhere, someone is probably doing the same for Earth.

    An incidental point is that if we are looking for planets trying to communicate with us, we should concentrate near the ecliptic, because that’s where any planets that have alien Kepler-like satellites likely to detect us will be. They’ll see *us* eclipsing our sun (and our other planets of course), so they’ll be more likely to regard us as an interesting system for follow-up investigation. And maybe they’re beaming messages at us right now. Interesting to think what sort of spectral signature *we* are advertising to the galaxy.

  6. When will we find life in space?
    January 17th, 2015

    You’re running a pool on this, right? What’s the bet?

  7. amphiox

    It means that any Earth-like planets we find may be populated by… yeast.

    Yeast being eukaryotes, and with the prokaryote to eukaryote evolution in grade of complexity possibly being the most rate limiting step for the evolution of more complex life, I’m willing to hazard to hypothesize that any planet that has yeast, or yeast-like organisms, will also have complex multicellular life as well.

  8. amphiox

    Any paleontologists reading this out there interested in chiming in about the likelihood of a robotic mission in the near future finding a fossil on Mars? It was my understanding that finding fossils in the field even on Earth was as much art as science, requiring experienced expertise to pick out the difference between a fossil and a regular rock. Is that something that a rover could be constructed to do? Or would it take a person actually being there?

    If you could design a mars rover specifically for looking for fossils, what kinds of instruments would you want to have on it?

  9. Wzrd1

    @Amphiox, it depends on the fossil you are looking for. There are microscopic fossils as well as macroscopic fossils.
    It shouldn’t be too difficult to find fossils of diatoms, if there were any on Mars.
    For more complex animals and plants, one would have to start literally cracking stone, as anything on the surface would be sand blasted by martian dust storms.

  10. Gil

    @9 wouldn’t that depend a great deal on the biochemistry of the life? Without knowing the chemistry you wouldn’t know what kind of geological formations would likely harbor fossils of it, I’d think.

  11. Perhaps we should send out robotic space trawlers with huge nets to the largest Lagrangian points in our solar system e.g. the Sun/Jupiter L4 & L5 points
    I’m fascinated by panspermia & Von Neumann probes & the L points might be a good place to look for evidence of both
    We may find natural & artificial life seeds out there collected into those little gravity wells
    We might even find a Dyson Astrochicken or two :)

  12. Fred Hoyle said that life came to Earth in a rain of viruses. No idea what evidence he used to support this idea. But life starting quickly on Earth *might* suggest something. It could equally mean that though life is complicated, there are lots of ways it could get started. But it could also mean that, although it’s improbable, we’re here, so it must have happened. The Universe is pretty big.

    I’m hoping we find ET before the zombie apocalypse [or insert your favorite doomsday scenario, possibly taken from Death From The Skies].

  13. Mission_guy

    I’m biased, but one of the coolest missions NASA is considering takes that next step beyond finding exoplanets to doing a massive survey of them to measure the molecules in their atmospheres. JWST can do it for some planets, FINESSE can do it for hundreds. We’ll see what NASA picks as part of their next Explorer competition in a few months.


  14. Mission_guy

    FINESSE, by the way, is one of the missions profiled in your own Discover Magazine in the Sept issue. Can’t seem to find the link to the article directly (it may not be online but only in the print version).

  15. If Martian methane is biogenic, then the discovery of life in space may turn out to be a gradual process of accumulating evidence rather than a single eureka moment. We might get another step in that process in the next few weeks from atmospheric analysis by Curiosity.

  16. Katie

    I’m interested in how the chemical experiments looking into life origins informs the search–particularly in looking for certain atmospheres. Chemists have been conducting experiments using the basic elements believed to be present when life arose to see what it takes for life to come into being. (Frankenstein anyone?) It seems like a greater understanding of the conditions when life arose here would give us a better idea of what to look for elsewhere. They haven’t succeeded in creating life yet, but the experiments have yielded some interesting results.


  17. What little higher math and astronomy I learned, ended 20 years ago….but I have never stopped wondering about these questions. I’ve kept up on the layman literature to the point where if it came to a citizen’s vote (not that it will or should just yet) I think I could make rational choices on what projects to fund, and at the very least, ask intelligent questions.

    I want to express my appreciation for those doing this amazing work, fighting to popularize this amazing work, and for all the other readers and commenters here who support the science and keep driving this debate, bringing it more into the mainstream every day.

    Between all the power struggles and politics and media distractions, it’s easy to forget that we live in wonderful times…amazing times.

  18. Chris Winter

    A bit of speculation…

    How would a Dyson Sphere be constructed? As many here know, I refer to a spherical shell around a star, by means of which the entire light output of said star is captured for use by an advanced civilization.

    Assuming such a thing is possible at all, it seems reasonable that it would be constructed much like the public works familiar to us — that is to say, in segments. It would start with a narrow chord and progress to a half-sphere. Finally, the narrowing gap would be filled in, making the sphere complete.

    Whatever stage of completion had been reached, the construct would still orbit its primary as a planet does. Thus (except possibly at the very earliest stage of construction) the light from that primary would follow an unusual pattern: visible light would blink out completely at regular intervals, while IR emissions would be relatively constant. I wonder whether it would be worthwhile to look for this sort of pattern.

  19. Kam

    I don’t know, and it’s a completely emotional hunch, but while it may not be equipped to find anything definitive, I’ve got a hunch about Rosetta.

  20. Bob Mabry

    I was surprised when I did the interactive web feature with the best numbers I could think of and came up with an estimate of only 185 extraterrestrial civilizations for the whole galaxy.

  21. Cairnos

    @ 19 Step one- invent scrith…

  22. Torbjörn Larsson, OM

    Great article, and I can agree with everything in it.

    The BBC Fermi calculator was neat, but it uses an old model paper of Lineweaver and Davis figure for the likelihood of habitable planets developing life of max 13 %. A Poisson model plugging in the Earth observation of early life raises that to ~100 % (for 7 billion year old planets).

  23. Torbjörn Larsson, OM

    @ amphiox:

    “Yeast being eukaryotes, and with the prokaryote to eukaryote evolution in grade of complexity possibly being the most rate limiting step for the evolution of more complex life,”.

    Perhaps, perhaps not.

    Whole genome methods show that domain diversification likely happened after the oxygenation of the atmosphere. [“The evolution and functional repertoire of translation proteins following the origin of life”, Goldman et al, Biol. Dir. 2010; “The Emergence and Early Evolution of Biological Carbon-Fixation”, Braakman et al, PLOS Comp. Biol. 2012.] Certainly eukaryotes are depending on the oxygenation (mitochondria; Lane’s energy theory for eukaryotes).

    At the same time fossil evidence of eukaryotes (eukaryote originating fossil sterols) reach back nearly that far, IIRC ~ 2 billion years out of ~ 2.5 billion years for the oxygenation. We may have tentative scarce evidence of early eukaryotes from before the mitochondrial endosymbiosis event, remains in the form of parasitic Megaviruses that branch off early on a genome tree.

    So maybe there was a lock in effect, with the eukaryotes that branched off before endosymbiosis crowded out except for the parasitic niche and new endosymbiosis products never standing a fair chance. (Compare with the difficulty for new abiogenesis.) While the endosymbiosis happened nearly as early as it could, i.e. it was not mechanistically difficult. We even have evidence of bacteria-bacteria endosymbiosis today (albeit the result is not competing energetically with eukaryotes, instead it lives in mutualism with, and within, some insects).

    “Is that something that a rover could be constructed to do? Or would it take a person actually being there?”

    Finding fossil bearing layers, even of most trace fossils, seems to be an art where people go out many times before they strike gold. Since Mars fossils would be old, and I doubt have diatom analogs just everywhere in sediments, I think we would have to expect to be “cracking stone” as Wzrd1 says.

    Or rather, if Curiosity finds organics (and I don’t think it is equipped to identify trace fossils like sterols or cellulose), it would help defining sample return. Such a program would then likely have to make tens of missions, drilling deep to get pristine samples.

    Since such a program would stretch for decades with the current funding rate, any shorter end runs should first be attempted. One such would be to look for nucleotides and their heteromers, seeing how theoretically it could be preferred since we use it and since recent results hints that RNA is chemically selected for its catalytic ability in anoxic and iron rich environments (i.e. pristine terrestrials).

    An instrument capable of doing that is the SOLID experiment which looks for predefined chemical markers, it is relatively small already as prototype and I would think cheap. Unfortunately nucleotides doesn’t fossilize well, so it would mostly be a way to pick up extant life.

  24. Cheers for reposting this, BA – or do you prefer Phil, Dr Plait? :-)

    Co-incidentally borrowed Seth Shostak’s book ‘Confessions of an Alien Hunter’ from my local library yesterday among others – haven’t started reading it yet tho’.

    One major point when it comes to intelligent or technological life is that going by own planet’s history technological life suchas ourselves in incredibly rare . There’s only been Humanity in four and a half billion years – at least that we know of. Plenty of life even intelligent by some definitions, octopi, elephants even dogs could qualify – but most of Earth’s history has seen only microbes on the surface.

    A powerfully striking, thought-provoking illustration of this is Carl Sagan’s “Cosmic Calander” where the history of the cosmos is condensed into a single metaphorical Earth year. Our Sun formed in September, microbes existed early almost straight after – but land plants didn’t exist until the 20th of December, insects arrived the next day and dinosurs went extinct on the 30th of that very last of months! 😮

    Now that’s one example only we only have Earth to go on for how long it takes an intelligent technological species to arise. We could be atypical – in either direction – there. We’ve got as yet no basis for comparison. There are suggestions for instance, that our unusually (?) large Moon and its tidal and axial stabilising effects could play a significant partin life leaving the oceans and evolving well. Our planet’s level of natural radioactivity as in Asimov’s Foundation series could be a key factor too and so on.

    But another thing that gives me pause is how many exoplanetary systems we’ve found are not like ours and lack or probably lack – habitable planets for us – many systems with Hot Jupiters and Eccentric Orbiters and none so far – or just maybe just one or two possible abodes of (earth-like) life amonmg the thousand odd exoplanets known.

    There still so many uncertainties and its still early days here and a case of insufficent data to draw any firm conclusiosn from I think. We still, really, have so little in the realm of hard fact and so much is speculation and educated guesswork. There are schools of thought and good arguments for both the “Rare Earth” and “Life Everywhere” cases and the reality I expect lies somewhere in betwixt those extremes.

    Life, I think, is hopefully and probably quite common. At a bacterial and “primitive” level.

    Sentient, technological life that we can communicate with and relate to as mindful equals? Hard to say but probably extremely rare and the Fermi paradox even tentatively makes me conclude vanishingly so.

    I hope I’m wrong about that.

    Or, given possible aliens and comparison to how humans have treated each other as well as near human creatures -neandertals to chimpanzees and orang-utans – do I?

    Facinating question with huge implications but so, so much still to discover and consider.

  25. Messier Tidy Upper

    Our planet’s level of natural radioactivity as in Asimov’s Foundation series could be a key factor too and so on.

    In fairness mind, I think that particular factor was an in-universe explanation for Isaac Asimov’s all-human universe which he created that way for other reasons and one that is rather unlikely to be the case in reality where Earth is probably not that exceptional in that regard. IOW. Don’t really see the Earth’s natural radioactivity levels as likely to be dramatically diferent from other Earth-type planets.

    Just an example of a random one-off type thing that could make us special but we don’t know yet.

    PS. Linked the wikipedia Cosmic calandar illustartion in my name above but see full wikipage here :


    Plus on Youtube – second version – here :


    In addition, link explaining the Fermi Paradox is here :


    Just to cover the unlikely off chance that any readers here don’t know what that’s referring to. :-)


    “Something to think about when trying to fathom these numbers : 1 million seconds is about 12 days. One billion seconds is about 31 years.”
    – Stephen Jones, letter in the Weekend Australian newspaper 2011, April 9th-10th.

    “Suppose the nearest civilisation on a planet of another star is, say, 200 light years away. Then some 150 years from now they’ll begin to receive our feeble post-world war II television and radio emission.”
    – Carl Sagan, ‘Pale Blue Dot’ page 388, Headline Book Publishing, 1995.

    “Cosmology also tells us that there are perhaps 100 billion galaxies in the universe and that each contains roughly 100 billion stars. By a curious co-incidence, 100 billion is also the approximate number of cells in a human brain.”
    – Page 237, ‘StarGazer’, Dr Fred Watson, Allen & Unwin, 2004.

  26. WKM

    @9 & 11 IANAP, but a geologist. My guess is that if any life did exist on Mars, it would only have been the simplest type(s). The big-picture geology of Mars does not seem to support any of the more (sometimes wildly) optimistic opinions of what we might find. As Phil says, there is “…tantalising evidence that liquid water might flow just beneath the surface, but we still lack any conclusive evidence”. The big problem is that although some sedimentary rocks have been found, the vast majority of rocks seen so far are volcanic. The holy grail (perhaps obsession is more appropriate) for Mars geology for probably four decades has been finding large amounts of carbonate rocks, thereby trying to radically improve the chance of finding past life on Mars (i.e. carbonate rocks and life are intimately related on earth, so it must have been the same on Mars). This has not happened, despite the fairly extensive surface and orbital missions. Only small amounts of carbonate minerals have been discovered and these likely formed as minor hydrothermal alteration of volcanic rocks.

    Paleontologists like to study particular fossil types, so they usually go hunting in sedimentary geological formations of a specific age. Some formations are fossil-rich making life easy, while others are fossil-poor meaning a lot of work to find what you are seeking. Neil Shubin and crew found Tiktaalik roseae after five years or prospecting in the Arctic on Ellesmere Island – but before that, they studied the geology in order to narrow down the specific sedimentary geological formation they needed to prospect.

    Normal rocky planet geological evolution requires formation of igneous rocks as the first step over extended geological time. A further significant amount of geological time and physical/chemical weathering is required before any sedimentary rocks can form. Given that Mars certainly appears to have had a strongly abbreviated sedimentary rock forming period, it is no surprise that no significant amounts of carbonate rocks have been discovered. If you want an idea of what earth has to offer in this regard, check out Tyndall Stone to see many fantastic fossils. It is late Ordovician limestone (~445 Ma, Selkirk member of the Red River Formation) that is incredibly fossil-rich, and extends over a huge area from Saskatchewan, through Manitoba (where a quarry is located), and down into the plains states. The rock is used as building stone in many Canadian cities, and the Canadian embassy in Washington.

    The obsession (desperation?) to find extensive carbonate rock deposits on Mars can be seen in an article by Fernández-Remolar (2011)* where they rationalize the lack of surface carbonate rocks by proposing that carbonate rocks must exist in the subsurface. As Scotty might say, “I ha’ me doots.” The “missing” carbonate rocks may not be “missing”, but rather could be nonexistent.

    * D. C. Fernández-Remolar et al (2011): The environment of early Mars and the missing carbonates. Meteoritics & Planetary Science 46, Nr 10, 1447-1469.

  27. Nick L

    @ 19 Chris Winter said: “I wonder whether it would be worthwhile to look for this sort of pattern.”

    If memory serves, they already have looked and while there was nothing obvious, they did find some “interesting but probably not” candidates.

  28. amphiox

    It would certainly be cool if Curiosity sidled up to a bed of banded sedimentary rock, took a picture, and we saw in that picture, just poking out of one of the layers, an obviously bilaterally symmetrical imprint with a clear internal scaffolding….

    (On occasion on earth we find fossils just be tripping over them)

    Not that we could ever expect to be that lucky!

    But one can dream, no?

  29. amphiox

    Or, given possible aliens and comparison to how humans have treated each other as well as near human creatures -neandertals to chimpanzees and orang-utans – do I?

    I think one of the reasons we have treated near human creatures like neandertals (though we don’t actually know for sure how we treated them), chimpanzees, orangutans, etc, the way we have is that, on some level, we have viewed them as niche competitors.

    So extrapolating that to alien intelligences, the question would have to be how likely an technological intelligence from another planet would regard another technological intelligence on another planet to be a niche competitor.

  30. Nigel Depledge

    The BA said:

    It means that any Earth-like planets we find may be populated by… yeast. But that counts. It’s life. And life does something special: it ingests chemicals and excretes other chemicals.

    Yeah, there’s something else really special about yeasts, too : they are eukaryotes like us.

    Personally, I feel that whatever alien life we discover is likely to more closely resemble bacteria and archaea.

  31. Nigel Depledge

    Katie (17) said:

    Chemists have been conducting experiments using the basic elements believed to be present when life arose to see what it takes for life to come into being. (Frankenstein anyone?) It seems like a greater understanding of the conditions when life arose here would give us a better idea of what to look for elsewhere. They haven’t succeeded in creating life yet, but the experiments have yielded some interesting results.

    And they are not attempting to go straight from chemical soup to life. And none of them expect this to occur within the time-frame of a typical experiment.

    It is reasonable to assume that the initial steps, from chemical soup to a self-replicating system, took many years (perhaps millions). I don’t think anyone reasonably expects to see a “chemical soup” experiment in a lab suddenly yield living organisms.

    Instead, the chemical experiments illustrate the facility with which natural processes form some of the “uniquely” biological molecules such as nucleotides and amino acids.

    On Earth, we never find nucleotides or amino acids just randomly lying around in the environment. The reason for this is that life on Earth is ubiquitous. All living cells have the ability to absorb useful molecules that they happen to find in the environment (well, sort-of, but it’s more complicated for multicellular organisms). Living things therefore rapidly take up any of these molecules that happen to end up just lying around in the environment.

    Thus, it was initially assumed that such molecules could only be formed by living systems.

  32. Nigel Depledge

    Chris Winter (19) said:

    Assuming such a thing is possible at all, it seems reasonable that it would be constructed much like the public works familiar to us — that is to say, in segments. It would start with a narrow chord and progress to a half-sphere. Finally, the narrowing gap would be filled in, making the sphere complete.

    In fact, a solid Dyson sphere is not stable, because the slightest perturbation in its orbit will be amplified by the gravitational interaction between the sphere and its star, until the two collide. IIUC, Dyson’s proposal was for many independently-orbiting segments that could exist in stable orbits (a bit like geosynchronous satellites, but on a much, much larger scale). One would then expect these to be assembled and launched individually, so this kind of activity might simply result in a gradual dimming of the star’s light that reaches us.

  33. Jon Hanford

    @ (28) Nick L; (19) Chris Winter

    Perhaps the study Nick L was thinking of was this “IRAS-based whole-sky upper limit on Dyson Spheres”: http://arxiv.org/abs/0811.2376

    The abstract notes:

    “When other stellar signatures that resemble a Dyson Sphere are used to eliminate sources that mimic Dyson Spheres very few candidates remain and even these are ambiguous. Upper limits are presented for both pure and partial Dyson Spheres.”

  34. amphiox

    I kind of think that Dyson Spheres are a very 21st Century way of tackling a 31st Century problem.

    If you have the technological wherewithal to contemplate building a Dyson Sphere, it is highly likely that you already have far more effective energy generation methods and won’t need to.

  35. reidh

    Never. it will never be “found” and if imagined to have been “found” it will never be able to be “proven to have been”. bet you (like the amazing randi) $1,000,000.00.

  36. MaDeR

    @reidth …and stars are figments of imagination. Spectra are obviously Satan work.

  37. Q: “When will we find life in space?”
    A: “When it´s too late…”

  38. marcher

    you say oxygen is almost certainly an idicator of life…i disagree. I think if fish breathe water and trees breath carbon dioxide, whats to rule out that a human species or something out there can’t breathe oxygen but helium for example? I think you scientists are to quick to not consider there can be stuff out there different than us. That function differently.

  39. Drunk Vegan


    Scientists look for Earth-like life for a very simple reason: we have no evidence of any other kind, so we wouldn’t know what else to look for. And even if we found un-Earthly life, we might not recognize it because it would be so different from our own.

    Thus the qualifer that is often used in searches for exo-Life, that we are looking for “life as we know it.” IE, something that requires warm, wet conditions, and will typically require oxygen to thrive as well (although there are anaerobic Earthly organisms, just not the norm anymore).

    Scientists are well aware of this. It’s not a bias or an oversight. It’s just that looking for life that does not resemble us in at least some small fashion is currently not possible.

  40. Jim

    While this is an interesting question, I’m skeptical that life originating beyond planet Earth will ever be found. That’s because I believe that the Universe and everything in it are specially created by God and that human beings, created in God’s image are special and unique. All this specialness means that life elsewhere may not have been created at all! I reject the idea of the spontaneous, meaningless, random origin of life. But I admit the speculative nature of this post.

  41. dcr

    Actually, none of “us” are going to be around whenever they DO use these “yet to be perfected” “machines” that they are have, to detect “human”-type -life on any other planet…Even though the whole idea may seem kinda strange to some people, I’d love to encounter another non-mammalian form of “life” , to sit-with & like share a cup-of-coffee…OR is this too humanoid?? ?

  42. Phil,
    No nod to optical SETI? There are some that now think optical is a more likely source of SETI signals than radio. I think the project at Harvard, funded in part by the Planetary Society, is pretty cool.

    – Ben H.
    Houston, TX


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar