Did life crash land on Earth from space?

PRINCETON / U. ARIZONA (US) — Early life forms or the ingredients for life may have traveled to Earth on chunks of rock, scientists say.

An international team reports that under certain conditions, there is a high probability that life came to Earth—or spread from Earth to other planets—during the solar system’s infancy when Earth and its planetary neighbors orbiting other stars would have been close enough to each other to exchange lots of solid material.

The findings—published in the journal Astrobiology—offer the strongest support yet for “lithopanspermia,” the idea that basic life forms are distributed throughout the universe via meteorite-like planetary fragments cast forth by disruptions such as planet and asteroid collisions.

Eventually, another planetary system’s gravity traps these roaming rocks, which can result in a mingling that transfers any living cargo.

“We wanted to know how debris left over from the formation of our solar system can get transported from one planetary system to another,” says Renu Malhotra, a professor of planetary science in the University of Arizona’s Lunar and Planetary Laboratory.

“Even today, some of these rocks leak out of the asteroid belt and hit planets,” adds Malhotra. “That’s how we get meteorites. Some of them land on other planets, and some get thrown out of the solar system.”

“With this study, we wanted to find out what happens to those small rocks that are thrown out and escape the solar system. Where do they go?”

Previous research suggested that, typically, those small rocks called meteoroids leave the solar system at high speeds, making the chances of being snagged in the gravitational pull of another object highly unlikely.

“Those studies assumed a typical velocity of 5,000 meters per second or more,” notes Malhotra. “They neglected the small fraction of material leaving a solar system at speeds slow enough to be captured by other planetary systems.”

‘Could have happened anywhere’

Using the star cluster in which our sun was born as a model, the team conducted simulations showing that at these lower speeds, the transfer of solid material from one star’s planetary system to another could have been far more likely than previously thought, explains first author Edward Belbruno, a mathematician and visiting research collaborator in the department of astrophysical sciences at Princeton University, who developed the principles of weak transfer.

Weak transfer describes a low-velocity process wherein solid materials meander out of the orbit of one large object and happen into the orbit of another. In this case, the researchers factored in velocities 50 times slower than previous estimates, or about 100 meters per second.

The researchers suggest that of all the boulders cast off from our solar system and its closest neighbor, five to 12 out of 10,000 could have been captured by the other. Earlier simulations had suggested chances as slim as one in a million.

“Our work says the opposite of most previous work,” Belbruno says. “It says that lithopanspermia might have been very likely, and it may be the first paper to demonstrate that. If this mechanism is true, it has implications for life in the universe as a whole. This could have happened anywhere.”

The team also found that the timing of such an exchange could be compatible with the actual development of the solar system, as well as with the earliest known emergence of life on Earth.

The researchers report that the solar system and its nearest planetary-system neighbor could have swapped rocks at least 100 trillion times well before the sun struck out from its native star cluster, moving it out of range of other planetary systems.

Additionally, existing rock evidence shows that basic life forms could indeed date from the sun’s birth cluster days—and have been hardy enough to survive an interstellar journey and eventual impact.

Co-author Amaya Moro-Martín, an astronomer at the Centro de Astrobiología in Spain, says the weak transfer mechanism would have allowed large quantities of solid material to be exchanged among planetary systems, over timescales that could potentially allow the survival of microorganisms embedded in large boulders.

Moro-Martín will present findings at the 2012 European Planetary Science Congress on Sept. 25

Star birth clusters satisfy two requirements for weak transfer, Moro-Martín says. First, the sending and receiving planetary systems must contain a massive planet that captures the passing solid matter in the weak-gravity boundary between itself and its parent star. Earth’s solar system qualifies, and several other stars in the sun’s birth cluster would too.

Second, both planetary systems must have low relative velocities. In the sun’s stellar cluster, between 1,000 and 10,000 stars were gravitationally bound to one another for hundreds of millions of years, each with a velocity of no more than a sluggish 1 kilometer per second, Moro-Martín says.

The odds of a star capturing solid matter from another planetary system with a star similar to the sun’s mass are 15 in 10,000, the researchers report—probabilities exceeding those under the conditions proposed by previous publications by a factor of 1 billion.

200 billion rocks

To estimate the actual amount of solid matter that could have been exchanged between the sun and its nearest star neighbor, the researchers used data and models pertaining to the movement and formation of asteroids, the Kuiper Belt—the solar system’s massive outer ring of asteroids—and the Oort Cloud, a hypothesized collection of comets, ice, and other matter about one light year from Earth’s sun widely believed to be a primary source of comets and meteorites.

The researchers used this data to conclude that during a period of 10 million to 90 million years, anywhere between 100 trillion to 30 quadrillion solid matter objects weighing more than 10 kilograms transferred between the sun and its nearest cluster neighbor. Of these, some 200 billion rocks from early Earth could have been whisked away via weak transfer.

For lithopanspermia to happen, however, microorganisms first have to survive the long, radiation-soaked journey through space. Computer simulations published previously by other researchers showed that survival times ranged from 12 million years for a boulder up to 3 centimeters (roughly 1 inch) in diameter, to 500 million years for a solid objects 2.67 meters (nearly 9 feet) across.

As for the actual transfer of life, the researchers suggest that roughly 300 million lithopanspermia events could have occurred between our solar system and the closest planetary system.

If life arose on Earth shortly after surface water was available, life would have had about 400 million years to journey from the Earth to another habitable world and vice versa before the sun’s star cluster dispersed, the researchers report. Likewise, if life had an early start in other planetary systems, life on Earth may have originated beyond our solar system.

“Our study stops when the solid matter is trapped by the second planetary system, but for lithopanspermia to be completed it actually needs to land on a terrestrial planet where life could flourish,” Moro-Martín says. “The study of the probability of landing on a terrestrial planet is work that we now know is worth doing because large quantities of solid material originating from the first planetary system may be trapped by the second planetary system, waiting to land on a terrestrial planet.

“Our study does not prove lithopanspermia actually took place,” Moro-Martín says, “but it indicates that it is an open possibility.”

NASA, the National Science Foundation, and the Ministry of Science and Innovation in Spain supported the work.

Sources: Princeton and the University of Arizona

chat44 Comments


  1. Cris Sleightholm

    This sounds the most plausible. Better than the god created theory.

  2. Roy Niles

    The big question has long been, where did our earthly life’s intelligence come from if life needed an initial spark of intelligence to evolve intelligent beings. This tends to firm up the conjecture that panspermia of some sort was the likely answer. Not a complete answer, of course, since we may ever know its ultimate origin.

  3. Jonathan Jordahl

    This finally justifies all of the aliens in science fiction being so anthropomorphic! They easily could have evolved in parallel ways all around the universe;)

  4. kimbee

    What do you mean by ‘intelligent’ Roy? That’s a very human concept. All you need is life which will evolve into ever more complex forms.

  5. Roy Niles

    Today’s biologists are aware that all life forms operate with at least a minimum of intelligence. And otherwise, it would have to kick in somewhere up the evolutionary line by some sort of creationist’s, or mother nature’s, magic. Which is fine with me if you want to believe either of those outdated theories. Such as life somehow blindly and dumbly gathering its intelligence out of thin air.
    And all our concepts about the nature of the world and the universe are human. So what? Do you use monkey concepts when discussing lower firms of life, or perhaps microbial concepts? I always wonder why you people read these scientific articles anyway, but of course ignorance doesn’t know it’s ignorant, does it.

  6. kimbee

    Ignorance? Wow, calm down there Roy, it was just a simple question about how you were defining the term ‘intelligence’ within the context of your comment!

    I personally would have just used the term life but as you said ‘Today’s biologists are aware that all life forms operate with at least a minimum of intelligence’ then we mean the same thing. By ‘intelligence is a very human concept’ all I meant was that it had several meanings. Intelligence could be defined by chemotaxis by a microbe or by reasoning and problem solving by a higher animal. It depends on how you use the term and from your original comment I did not understand how you were using it.

    Erm, no I don’t use simian or microbial concepts, ever. I wish I could, it would make life quite interesting. Neither do I believe in these ‘outdated theories’ , I am a biochemist with a keen interest in evolution and a curiosity about the origins of life and the universe as a whole. However, I’d not criticise any one who did or anyone who wants to believe in both a scientific theory and a creationist belief.

    I always wonder why you people comment on these scientific articles if you only do so to insult and not to discuss. I thought that was the whole point of a comment section but then being so ignorant, what would I know?

  7. Roy Niles

    Chemotaxis by a microbe? How outdated can you get? Check out the papers by James Shapiro among several others.
    And in any case, you said earlier, “all you need is life which will evolve into ever more complex forms .” Nothing there about just wondering what I meant by intelligence. So, yes, you wrote an ignorant comment, and your latest one did very little to save it. Biochemist, indeed.

  8. kimbee

    What?! Are you just wanting to antagonise me? Please, what is the point? I think you’ve made it clear that you think I’m stupid. Great, fine. Let’s leave it at that. And I don’t like you either. Hooray for humanity. I’ll send you my qualifications in the post.

  9. Joshua


    Great conflict-resolution.

    This is all.


  10. Roy Niles

    Anyone who starts a sentence with “erm” is asking for it.

  11. rtwilliams

    ..( pick whatever word you want to start)… none of this nullifies the possibility of a God created universe and opens up another mystery wherein God expects us to grow in understanding of His ineffable nature.The Bible i see as a magnificently and divinely inspired text written down by human hands and with human understanding of mysteries we have not grown into. I accept Christ Jesus as the historical personage and true son of God sent to teach us that the above conversations, which do not treat the coparticipants as respectfully as they would have themselves treated, detract, rather than enhance our ability to grow into the Kingdom of Heaven on earth, which we earthlings alone can make real.

  12. Roy Niles

    So if life did arrive here from elsewhere in the universe, your God only lets we earthlings into heaven?
    Maybe that’s what he tells all other creatures in the universe, all of them being flummoxed according to their abilities and needs.

  13. Robert

    Sooner than later it turns out that everything Douglas Adams came up with in the guide to the galaxy was correct.

  14. Alex

    Oi Roy level of functioning logic is damn low here or you are just trolling ? ” Such as life somehow blindly and dumbly gathering its intelligence out of thin air.” are we talking about DNA changes here ? Or we are talking about intelligence : ability to learn ,reason or memorize?

  15. Roy Niles

    You’re the dummy if you think there was no intelligence out there in “thin air” before life, as the scientific studies above indicate, may have been seeded here. Or do you think that the first life forms could not think at all, but like that other dummy argues, reacted intelligently to stimuli with no intelligence? Talk about trolling! I started the comments with a positive note in agreement with the article. You trolls sprung up to disagree as usual.

  16. Roy Niles

    Actually, Alex, nobody here yet has argued that life “blindly” gathered intelligence out of “thin” air, and if that’s how you’ve interpreted the article or any of my comments, your functioning logic is at a low level indeed.

  17. Roy Niles

    “Which is fine with me if you want to believe either of those outdated theories. Such as life somehow blindly and dumbly gathering its intelligence out of thin air.”
    But apparently, Alex, you do believe in those outdated theories, which is fine with me.

  18. Roy Niles

    In 1990, The physicist, John Wheeler suggested that information is fundamental to the physics of the universe. According to this “it from bit” doctrine, all things physical are information-theoretic in origin.
    Wheeler: It from bit. Otherwise put, every “it” — every particle, every field of force, even the space-time continuum itself — derives its function, its meaning, its very existence entirely — even if in some contexts indirectly — from the apparatus-elicited answers to yes-or-no questions, binary choices, bits. “It from bit” symbolizes the idea that every item of the physical world has at bottom — a very deep bottom, in most instances — an immaterial source and explanation; that which we call reality arises in the last analysis from the posing of yes — no questions and the registering of equipment-evoked responses; in short, that all things physical are information-theoretic in origin and that this is a participatory universe.”

    Buckminster Fuller believed that the universe, like the life it has allowed to exist on earth, operates with an anticipatory system. He said, “Experience had clearly demonstrated an a priori anticipatory and only intellectually apprehendable orderliness of interactive principles operating in the universe into which we are born.“

  19. Alex

    roy talking about logic : familiar with term ad hominem ? ” You are an idiot if you think there is no intelligence in the air” . Sound like one of those: its- so- self- evident- that- you- dont- need -to -prove- it nonsense. You are yet to define what ‘intelligence’ you are talking about . I think you are trying to start an argument here , but i dont really see any real argument . Something about me being stupid , something about life gathering intelligence , some bizarre physics theories ,etc . Appeal to authority is another fallacy i smell . I dont care what people think when it comes to science , what i care about is if they can prove their ideas or not .

    Now my turn for ad hominem :you sound like another pseudo intellectual playing philosopher . Wordy writing with little substance . You think you are unique , but internet full of fellows like you .

  20. Roy Niles

    Again with the little misquotes to make what you think is a point? The internet is full of little lying twerps like you as well. Do you, for example think you are smarter than the [people who wrote this article? Or John Wheeler, or Buckminster Fuller, or Whitehead, etc., etc., etc.? I don’t think I am.
    (But then I didn’t make up my name here so I could safely show my ignorance.)

  21. Sam

    As a biochemist and keen scientist, I say Roy is either a troll, or a blooming idiot, or both. I don’t recommend anyone give him the time of day. I won’t be responding to any of his ‘questions’, regardless of what form they take. @Roy, if you are a troll, give it up mate, there is much more to life. If you are merely misguided, I recommend education, of the sort that is peer reviewed and qualified. Good day to you sir!

  22. Roy Niles

    Kimbee now calls himself Sam. But otherwise he can’t do anything but say I’m wrong, and if one is wrong, then one is a troll. Supposedly this article was written by trolls as well, since I agree with it. And why does he disagree? Why because he says he’s a keen scientist. Other than that, he has no science to offer to dispute the contentions of the scientists who inspired this article.
    He says I need peer reviewing to comment on an article, when I agreed with the article. Or I need peer reviewing to state why I agreed? Do the scientists I cited count as peers?
    Is Kimbee/Sam the proper name for a peer that disagrees by insult and calls it logical?

    This was a good article. It makes some good and interesting points about the origin of life on earth. To assume that it has to be wrong because some outdated scientists still claim the universe is dead and life somehow started making choices by accident is not scientific. Kimbee/Sam is certain that the article and anyone who agrees with it is wrong. The article did not claim to be certain, and neither did I. Only the Kimbee/Sams here claim certainty. That;s science? Give us a break.

  23. Cris

    As Rod Serling once said, It is difficult to produce a television documentary that is both incisive and probing when every twelve minutes one is interrupted by twelve dancing rabbits singing about toilet paper.

    Same goes for comments. Comments should stay on course and not be filled with insults. Intelligence be damned.

  24. Roy Niles

    “All you need is life which will evolve into ever more complex forms.” “Intelligence be damned.”

    Comments continuing to stay on course, of course. Are we having fun yet? I know I am.

  25. kimbee

    Sorry Roy I really didn’t find our argument that interesting to carry on under a different name ‘Sam’ is not me. I was interested in discussion of the topic not a slanging match – hence my farewell. You’ve tempted me back now with your incorrect use of the personal pronoun. Please remember, next time you want to call me names it’s ‘she’ not ‘he’.

    I’d also like to state my own views, not have some strange old American bloke do it for me: ‘Kimbee/Sam is certain that the article and anyone who agrees with it is wrong.’ This is not true at all. I did not say or imply anything of the sort. Nor do I think there is much to agree or disagree with, the article describes something that possibly happened. It did or it didn’t, it doesn’t matter about arguments. It is the review of evidence that interests me, not philosophical debate. I for one find lithopanspermia to be a very sound theory and one that I hope, is true.


  26. Roy Niles

    Sorry for the mistake, Kimbee. It looks like Sam was pretending to be you, calling himself or itself “a biochemist and keen scientist.”

  27. Alex

    Roy can you disprove that Sam is not a scientist ? NO ? then why dont you just STFU ?
    “Do you, for example think you are smarter than the [people who wrote this article? Or John Wheeler, or Buckminster Fuller, or Whitehead, etc., etc., etc.? I don’t think I am.
    (But then I didn’t make up my name here so I could safely show my ignorance.)” Red herring much ?

  28. Roy Niles

    I can’t disprove Sam isn’t you either, who and whatever you are, Alex. All of you bozos seem afraid to use your real names.
    By the way, can I disprove either of you is a fool? No.

  29. kimbee

    No, it doesn’t really. Otherwise he’d have used my name. It looks like he was pretending to be himself. There are more biochemists on the planet other than myself; I’ve even met a few! You were just jumping to conclusions in an urge to insult someone, as usual. And no, I don’t use my full name, why should I? I, like most people, protect my identity so that the weirdos I talk to in comment discussions/slanging matches can’t find my website/social media profiles. I don’t really want those people knowing any of my personal information.

  30. Sam

    Kimbee, I agree with your sentiments about lithopanspermia. The chances it could have happened are much greater than we previously thought, something I have always wondered about, the probabilities of this happening. It would be interesting though to know the probabilities involved in successful transfer of live organisms from a planetary system to a viable planet. I’m guessing we would get a drop of several orders of magnitude.

  31. kimbee

    Exactly Sam. How much of it is out there too? And has the planet been exposed in the more recent past, since life has been established? Multiple sources would give rise to more diversity, could this also explain why we have such a wide variety of life?

  32. Sam

    Interesting thought Kimbee. As the planetary systems are now a lot further apart as the sun has migrated from its local cluster, my hunch would be that the exchange of material in more modern times may be less. Of course all known life uses DNA/RNA as its blueprint, and further, we can do phylogenetic mapping based on an organism’s DNA/RNA that ultimately links it to all other forms of life. Hence we know that all life alive today and all extinct specimens for which we are able to extract ancient DNA from had a common origin and single ultimate ancestor. I guess it is possible for that common ancestor to have arisen on another planet and ‘permutations’ of that origin be transferred to Earth multiple times, each time as a different species, this could have contributed to our diversity?

  33. Roy Niles

    A nice act there Sam/Kimbee. All within less than an hour’s time. Neatly arranged, but with your claim to be actual scientists, you don’t seem to know that there’s no evidence that any of our life forms would have evolved from a variety of planetary sources. So your little act as he and she, the contrite biochemists, hasn’t quite succeeded in fooling anyone. And over-explaining your reasons for not giving your real name is also a dead giveaway of this silly little setup. Pitiful as usual.

  34. Sam

    Further to my last point, it is a sobering thought that in 6 billion years of planet Earth, and with the possibility of exchange of material from other systems that could be a few billion years older, all our evidence points to life having only arisen once. Once. Let’s let that sink in. This means the chance of life arising de novo is incredibly, incredibly small. Once in 6 billion years per planet, or perhaps even less if lithopanspermia occurred, it could be once in 8 billion years across a dozen or more planets combined. It is even more sobering when we consider the fact that as far as we know Earth is the best place for life to develop. It is in the goldilocks zone so has liquid water, the best and universal solvent, there is nothing better. Everything about the temperatures on planet earth, and the composition of its materials is at or close to optimal on a relative scale for supporting the lowest energy requirements for life where it works at the microscopic scale. Other combinations could and may exist, but our combination, based on what we know of chemistry and the flow of Gibbs free energy, is close to the best. Yet still life only arose once. In 6 billion years. What does that say for the chances of novel life out there in the cosmos?!!

  35. kimbee

    I’d definitely agree with that, with the whole universe expanding it is inevitable. I’d also assume that if there were lithopanspermia in modern times then any life form would be subject to predation by existing species and it would be a lot harder to pass on any genetic information into an existing system. It is so very exciting to find evidence that supports a universe full of life, I’ve always found the idea that earth is an irregularity to be very sad and slightly arrogant. I guess one of the ways this to add more evidence to this theory is to look at samples from Mars (either from the surface or from sources like the ALH84001 meteorite, where they found the segmented ‘worm-like’ fossil). Whether or not life has ever existed on Mars is a whole different kettle of fish, but if any genetic material could be recovered (granted it would be very difficult/almost impossible to do so) it would be very interesting to see how it compares to early earth life.

  36. kimbee

    Sorry that last comment was in reply to your previous Sam. Roy, act? It’s a conversation. I’m not claiming to be an all knowing sage expert, I was just interested in discussing the topic with someone like-minded. WTF are your scientific qualifications anyway?!! I don’t even know why I’m bothering to get involved in your petty exchanges, I am quite ashamed of myself. All I can say to justify my behaviour is that it is a pretty slow day at work and your insistence to annoy everyone is fairly amusing. But like I said it is a slow day. I only have two more words for you and given that I’d estimate I’m about half your age they’re also fairly amusing: grow up.

  37. Sam

    I def hope that Earth is not an irregularity Kimbee :) That would be very sad.

  38. Sam

    And I do keep hoping that we will find life, or at least extinct life on Mars, or maybe soon on Europa. It would indeed be very fascinating to see if any life found used DNA (and not some other method of encoding itself) and hence was related to our life.

  39. kimbee

    Oh yes, that’s the dream. Although I did my thesis on extracting aDNA (ancient DNA, mainly from fossils – inspired by Jurassic Park!) and it is a very, very tricky business. Although they’re developing new methods all the time, there are a lot of new technologies for drug development that would apply. I guess if anything did turn up it would be pretty motivating!

  40. Roy Niles

    “I don’t even know why I’m bothering to get involved in your petty exchanges, I am quite ashamed of myself.”

    As well you should be. I’ve seen better acts in a flea circus.

  41. Roy Niles

    By the way, you still can’t handle this initial question, can you?

    “The big question has long been, where did our earthly life’s intelligence come from if life needed an initial spark of intelligence to evolve intelligent beings. This tends to firm up the conjecture that panspermia of some sort was the likely answer. Not a complete answer, of course, since we may never know its ultimate origin.”

  42. Roy Niles

    To sum it up, someone who claims to be a scientist, and pretends to be of either sex when suitable, won’t give his or her name, yet on the basis of those professed credentials, tells us with all certainty that early life could well have gotten DNA from several extra terrestrial sources, but even so there was no intelligence involved in the process, since chemotaxis by a microbe doesn’t require making choices or learning from mistakes. So even though today’s biologists have found that conjecture to be wrong, this “biochemist” says that because of his, her or its (alleged) status as a knowledgable chemist, those biologists who have found intelligence activating the physiochemical processes in living organisms are not only wrong, but are unquestionably so.

    And woe unto those of us who don’t buy it.

  43. alex

    Roy im most definitely not Sam . Because in my country there is no name Sam. You trolling stinks . You think too much of yourself if you think that people would use different names just for your sake . Now why dont you define what is that intelligence you are talking about ? Your demented brain stuck in eternal loop of name calling and screaming intelligence ?

  44. Harry Boota

    Besides the actual content within the article, the most amusing thing was the remark by Roy Niles on 26th September 2012 where he says –

    ” I always wonder why you people read these scientific articles anyway, but of course ignorance doesn’t know it’s ignorant, does it.”

    Him reading this article to remark on it shows that he is obviously ignorant to the fact that HE has actually read the article too!

    I guess we are all reading it hopefully for the same reason, for enlightenment, perhaps, curiosity about other’s thoughts, perhaps!

    One thing that always perplexes me is that fact that the scientists are always looking for an excuse for life from outside of the Earth!

    Why? what is wrong with looking within? why is it hard for them to think that if we have all this plethora of life on this beautiful planet that LIFE actually began here!!

    Ahh but that won’t bring in the funding so that could waste billions on exploring space!

    If there is no life outside of the earth in our own solar system then it quite pointless looking at planets millions of light years away, because for one thing, they may not even exist and secondly the practicalities just simply are not there.


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