Did life here begin out there?

By Phil Plait | August 7, 2007 4:11 pm

There is this idea called panspermia, which says that life originated somewhere other than Earth, and was transported here by some means — usually a comet or meteorite impact.

This isn’t as silly as it sounds. For one, Mars is smaller than the Earth and farther from the Sun, so it cooled more rapidly and may have been more earthlike long before the Earth was. For another, complex molecules called amino acids, which are the building blocks of proteins, have been found in meteorites. Third, we know that chunks of other planets have made it here to Earth as meteorites.

The problems with this idea are legion. For one, two astronomers named Hoyle and Wickramasinghe who support panspermia have in the past made hysterical claims about it in the past, wielding it like a wildcard every time they can (when you claim bird flu and the 1918 flu come from space with absolutely no reason to think so, it’s time to consider the source when new claims are made). For another, it’s unknown how long a microbe, say, could survive in a chunk of rock or ice out in space. Research into this problem would be very interesting.

An article was just published on The Age’s website saying comets cannot transport microbes to Earth, because cosmic rays — subatomic particles in space moving at very nearly the speed of light — would destroy them.

The problem is, the article is almost entirely content-free. The scientists found ancient microbes in some Antarctic ice and tested their genetic material for degradation. The article doesn’t say how they went from this to saying microbes cannot survive in comets. It says the work has been published in PNAS, but I cannot find it. The article does quote other scientists who bring up legitimate objections, but this doesn’t help if I can’t find the (&*(*$*()^$ original article.

I’d love to say something scientific here about the study, but I can’t. If anyone has any leads on this, I’d appreciate it.

Update: It figures. Within minutes of posting this, I coincidentally get an email from a list on I’m on pointing me to this article from the BBC, which clarifies the whole thing. The researchers revived old microbes and found the younger ones (100,000 years old) fared better than older ones (8 million years old). Radiation damage was the culprit. The ice they used was 3-5 meters below the surface, so it seems to me the claim that this is an objection to panspermia is hollow; comets can be very large, so microbes could be buried a mile deep in the cometary ice.

CATEGORIZED UNDER: Astronomy, Piece of mind, Science

Comments (26)

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  1. A Ler…-- Rastos de Luz | August 8, 2007
  1. Hey Phil,

    Im a longtime lover of Badastronomy.com, and I may have commented once or twice.

    Anyway, I just wanted to say that I liked the page format better before the ads came in between the body and sidebar columns.

    Perhaps move the ads column to the left of the page, keep the body in the middle, and the info sidebar on the right?

    Anyway, your writing and topic choices are still first rate. I looooooove the material :)

  2. AstroPaul


    The Science article is VERY slightly more detailed, but I agree it could use more explanation — and I, too, find no sign of the article on PNAS yet. Maybe later this week!

  3. Dexceus

    While the younger ones did do better, some of the older ones did survive and reproduce so it is still a possible. Or I am completely wrong. I was reading last week on the Planetary Society Web Page where they are actually planning on doing an experiment on a mission going to Mars to see if it is possible for microbes to survive the trip. http://www.planetary.org/programs/projects/life/

  4. You still see ads on the internet Aaron? Just get Ad Block Plus (it’s free) and poof, they’re gone. https://addons.mozilla.org/en-US/firefox/addon/1865

    Great article Phil! Wasn’t the whole “we found life on Mars” thing a decade or so ago due to small forms of life living in space on the probes we sent up?

  5. bearcub

    I read an AP article about this yesterday. That article only mentioned that there a sharp falloff at about 1.1 million years, no mention of radiation at all. The way it was phrased led me to believe that it was along the lines of an upper limit for molecular stability, without any outside influence.

    I’m glad I read the BBC article you linked, because I was going to ask where you got the radiation bit. Lazy writing over at AP I guess.

  6. Why couldn’t life have originated on Earth?

    Which is more likely, that life started earlier on Mars then luckily got blasted to Earth at just the right time so that it would flourish here and before conditions on Mars because inhospitable to organic life, or that as soon as conditions here on Earth became hospitable the molecules that could become life did?

    After all, it had to start somewhere and we know conditions here were just right for it about the same time we think it, in fact, did start. So, did I get up and get to work on time today because my neighbor did so first, or because my alarm clock went off at the appropriate time and conditions were right for me to get out of bed?

    We don’t know that Mars was ever really hospitable to life. Was the atmosphere of Mars thick enough to block the ultraviolet light that is so dangerous (such that we use the light to help sterilize some parts of our homes)? Was the liquid that carved certain features on Mars really water? Was Mars hospitable to life long enough?

    So, yeah, it’s interesting to consider that life may have begun somewhere else and gotten itself transported here. It just doesn’t seem (at least to me) to be the most likely cause of the life we have here now.

  7. So where did we all come from?
    Well in my opinion its not really a question of where we all come from and how we got here, in truth it is quite an irrelevant opinion to the question I’m going to ask here-

  8. John Fleming

    I think panspermia is viable, and has probably happened in the past, if not in our solar system then somewhere in the universe. When I think about it, though, it’s kind of impractical to transport ready-made organisms, because chances are against them landing in an environment similar to the one they evolved for. Instead, I find it much more likely that panspermia seeds the prefabricated components (such as aforementioned amino acids) to various bodies, where it can then have a chance to assemble into a form suited to the climate it happens to find itself in.

    Am I saying this is the work of an intelligent creator, then? Of course not! I just think that the galaxy, and perhaps the universe itself, has over vast amounts of time ‘selected’ for these molecules. They aren’t living things, but viruses scarcely are, either.

  9. Re: Chris,

    Well, if I were to install that, would it remove the entire ad column on Phil’s site?

    I dont necessarily want all ads to be removed. First of all, im a capitalist, and secondly, I know that oftentimes the ad generators produce crap thats relevant to what youre looking at, and sometimes I indeed to want to click on an ad that I see on a site Im browsing.

    I just figured that the main body of the site would be better off in the middle, with ads on the left and the sidebar thingy on the right.

    I wouldnt want Phil to delete the ads either. Gotta let a player get paid for his honorable toil!

  10. Tony

    The theory is fine… but I hate it when people explain the source of life with “It came from space…”. Then, where did THAT life come from? Stupid people… 😛

  11. Nigel Depledge

    Amino acids are “complex” are they?

    Here’s one: alanine: H2NCH(CH3)CO2H.

    Here’s the empirical formula of a protein I’m working with:

    Of course, I get that amino acids are relatively complex in terms of the kind of chemistry that happens out in space (mostly taking place at very low temperatures).

    Besides, the fact that 8-million-year-old microbes did not fare so well as younger ones is not a convincing criticism of panspermia. This is because the first microbes arriving on Earth would have had no competition, so they did not need to multiply rapidly. All they would have needed was the ability to reproduce at all. If they could do this, they would have been able to form a large enough population for natural selection to act upon, even if this took many years.

  12. Nigel Depledge

    Hmmph. The “subscript” tags didn’t work. I’ll just try that again with spaces to see if that makes it any easier to read:
    C831 H1323 N267 O251 S10

  13. Adam

    A comet seems to be a very unlikely source of life on Earth. Organic material? Sure, why not, but not living organisms since that would mean that life would develop on or inside an asteroid. Not viable, in my opinion. A meteorite makes more sense if it came from some planet. But I agree with John B. Sandlin: Earth seems the most likely place for spawning life in our solar system. Of course, it could have come from outside our solar system.

    Well, then there is this untestable idea that life came to be through a miracle i.e. divine intervention which circumvents the laws of nature but saying this on this blog is probably asking for trouble… 😉


  14. Carolyn

    Sorry if this is slightly off-topic (life beyond earth, not how it might have got here), but I can’t find any mention here or on the discussion board…did anyone watch BBC2 (UK) last night, 7.30pm?

    The Cosmos: A Beginner’s Guide, presented by Adam Hart Davis.

    Life in the Cosmos


    “If we find life elsewhere in the Cosmos, what will it look like? Could Hollywood’s science fiction monsters stand up to a bit of science fact? We’ve teamed up space scientist Dr Phil Plait with evolutionary biologist Dr Lynn Rothschild to scrutinise some of the most famous Hollywood aliens.”


    “…We travel to the pretty, seaside town of Beer in Devon. It’s probably the last place you’d expect to find life similar to that which could exist on other planets. But for astrobiologist Professor Charles Cockell of the Open University this beach on the South Coast is home to a form of life you could expect to find on alien worlds. We join Charles as he collects samples for the ultimate endurance test – a journey into outer space!”

    He’s planning to send some extremophiles (battered by salt water and exposed to the sun on a cliff) to the conditions they’d experience travelling through space. So that might shed some light on the problem of life surviving interplanetary/interstellar conditions.

  15. Martin Moran

    I watched BBC2 last night and it was great to see Phil on the TV. I did find it a bit disturbing though that there could be 10,000 civilisations out there in our galaxy alone and that our TV is being beamed into space. Imagine if the Aliens watch the original Star Trek, I mean if Kirk couldn’t shag it he’d kill it, surely this is not the message we should be beaming out to the wider community, lets hope they watch the next generation before making any decisions!

  16. Bill Bones

    “Life didn’t started here, it came from over there”. Fine. But, how did life started over there, then?

  17. R S James

    In the interest of accuracy, the article Phil referenced on the 1918 flu epidemic DOES NOT claim the microbes came from space. Instead the author’s claim is that the virus was floating in the air at high altitudes, and was coming down in mists and bird droppings! It is an interesting idea and the author seems to have no direct evidence whatsoever to back it up. He does the usual tactic of claiming that the predominant theory of the flu’s spread has deficiencies (i.e., If it were spread by human contact, the spread would happen at a constant, even rate.), so therefore the predominant theory must be wrong. Of course, the next logical jump is, since the dominant theory is wrong, the author’s theory MUST be correct. He even states “The only reasonable inference to be drawn is that the virus was airborne …” I’m tempted to argue that there might be other inferences that are reasonable!

    The article (actually, it appears to be a letter to the editor) provides a link to a research paper that does make the connection between microbes in Earth’s atmosphere and the arrival of these microbes from space. The paper sounds very technical, with lots of diagrams that seem to be tangentially related to the subject. And he even garners support for his theory from a Shakespeare quote! It makes for entertaining reading for the skeptics out there.

  18. Carl Fields

    I’ve never thought very highly of panspermia theories. However, it’s difficult for me to immediately accept your apparent argument that the observations described in the paper are irrelevent because the microbes were only 3-5 meters down into ice. Seems like one would have to compare the effects of several pairs of variables, including: (1) earth-suface radiation field vs interplanetary space radiation field; (2) amount of additional shielding for 3-5 meter depth vs possible multiple-km depth (“additional” because it’s in addition to shielding from earth’s atmosphere and magnetic field); and (3) few-million years (exposed to radiation) vs possibly few-billion years. I suspect you are right in that the amount of radiation shielding by ice is probably dominant (I think it goes with some kind of exponential relationship with depth), but I’m not 100% certain.

  19. Tony is correct

    Panspermia is one big cop out

    Q “So how did life arise on the Earth”
    A “It came from another planet but managed to get here by a comet”
    Q “So how did it arise there then”
    A“Oh it didn’t, it came from another planet and was lanted on that planet”
    Qgives up as he can see where this is headed

    All you do is move the question back up the line of how did life come into being.

    We have been working on this for years and still have never got anywhere near something living. To say it was planted from somewhere else is ducking the issue.

  20. John Krehbiel

    Wasn’t there live bacteria in the Surveyor camera brought back from the Moon?

  21. Darth Robo

    “did anyone watch BBC2 (UK) last night, 7.30pm?”

    Oh man, I wish I knew that was on! :(

    Don’t suppose the programme can be watched online? Not that I’ll be able to watch it ’till I get my net @ home fixed…


  22. VisionEngineer

    John Krehbiel: Yes, the surveyor camera recovered by Apollo 12 had 50-100 microbes that survived for nearly 3 years on the moon. The microbes were given the proper environment and nutrients and then began to multiply. The microbes had survived the pre-launch testing, vacuum of space, radiation, extreme cold, and no water or nutrients. Pretty amazing.

    I was wondering: Could it be dangerous to revive microbes from millions of years ago to which humans have never been exposed? I would think that this would have to be done with very careful control to remove the the risk of the microbes leaving the laboratory.

  23. SCR

    Mars and Venus at the time life arose were both possibly more habitable and better for life arising than Earth.

    Venus had a nice protective atmosphere, extra heat and warmth – and oceans.

    Mars had a nicely warm if cooling surface, thin but better than todays atmosphere with oceans, lakes and glaciers plus a shallow gravity well allowing material to be blasted off into space releatively easily.

    Erah had suffered a mammoth impact (forming our Moon) was molten or just highly geologically active with a thick poisonous atmosphere, deep gravity well and oceans.

    Later on, mind you, Earth froze into an enormous snowball, Mars lost its air and activity and chilled whilst Venus overheated & turned into a toxic pressure-cooker. Earth recovered – its planetary neighbours well … didn’t.

    But all three of those worlds could have been the origin for simple life living in _very_ different conditions from today.

    Perhaps all three of them were.

    I think comets *may* have carried ammino acids and protein-carbon chains to Earth. I think its likely life _could’ve_ emigratedfrommars to Earth via meterorite. Life *could’ve* begun in molecular clouds on small grains of dust drifting in the void.

    All speculative and plausible rather than proven but interesting.

    & wasn’t Svante Arrhenius or somebody like him (spelling?) the originator of that panspermia idea – as well as first noting the Greenhouse effect?

  24. SCR

    “# VisionEngineer asked on 08 Aug 2007 at 9:30 am :

    “I was wondering: Could it be dangerous to revive microbes from millions of years ago to which humans have never been exposed? I would think that this would have to be done with very careful control to remove the the risk of the microbes leaving the laboratory.”

    It would be I’d expect.

    But the danger is probbaly unlikely as humans and such microbes (nanobes /virii) would (most likely) be so vastly different as to be just too incompatible for creating diseases in each other.

    Parasites – even virii – depend on adapting to and living within (& exploiting for reproduction) – their hosts – it seems most probable alien organisms will be incapable of doing this.

    Panspermia in which life is derived from a common source may if true make us more vulnerable. Hoyle is a pretty smart bloke and a good writer but I remain unconvinced if intrigued by his arguments – I have read his book (co-written with Wickramasinghe – spelling?) many, many years ago.

  25. SCR

    To clarify : “Panspermia in which life is derived from a common source may – if true – make us more vulnerable to alien plagues. ”

    Because if we’re more closely rather than less closely related there’s a greater chance such exo-biotes (alien living things) could adapt to or survive & reproduce inside our bodies.

    If, for instance, we’re both carbon-&-water, DNA-RNA sugar & light feeding organisms rather than say us being carbon-&-water, DNA-RNA sugar & light feeding organisms but them being, say, LiNeFlHg* based silicate & gamma ray feeding organisms clearly the chances of them being compatible and able to cause disease(s) in us is vastly greater.
    * LiNeFlHg -based = Lithium Neon Fluorine Mercury based living creatures! An unlikely blend of exotic elements for life because of rareity and less reactive / more reactive chemical factors I know. I’m not postulating such alternative life merely a hypothetical example but …
    a-n-y-w-a-y … You get my point I hope.


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