Forgot your password?
typodupeerror
Earth Space Science

Scientists Study Trajectories of Life-Bearing Earth Meteorites 199

Posted by samzenpus
from the we-come-from-earth dept.
Hugh Pickens writes "About 65 million years ago, Earth was struck by an asteroid some 10 km in diameter with a mass of well over a trillion tonnes that created megatsunamis, global wildfires ignited by giant clouds of superheated ash, and the mass extinction of land-based life on Earth. Now astrobiologists have begun to study a less well known consequence: the ejection of billions of tons of life-bearing rocks and water into space that has made its way not just to other planets but other solar systems as well. Calculations by Tetsuya Hara and his colleagues at Kyoto Sangyo University in Japan show that a surprisingly large amount of life-bearing material ended up not on the Moon and Mars, as might be expected, but the Jovian moon Europa and the Saturnian moon Enceladus also received tons of life-bearing rock from earth. Even more amazingly, calculations suggest that most Earth ejecta ended up in interstellar space and some has probably already arrived at Earth-like exoplanets orbiting other stars. Hara estimates that about a thousand Earth-rocks from this event would have made the trip to Gliese 581, a red dwarf some 20 light years away that is thought to have a super-Earth orbiting at the edge of the habitable zone, taking about a million years to reach its destination. Of course, nobody knows if microbes can survive that kind of journey or even the shorter trips to Europa and Enceladus. But Hara says that if microbes can survive that kind of journey, they ought to flourish on a super-Earth in the habitable zone (PDF). 'If we consider the possibility that the fragmented ejecta (smaller than 1cm) are accreted to comets and other icy bodies, then buried fertile material could make the interstellar journey throughout the Galaxy,' writes Hara. 'Under these circumstances fragments could continue the interstellar journey and Earth origin meteorites could be transferred to Gl 581 system. If we take it as viable, we should consider the panspermia theories more seriously.'"
This discussion has been archived. No new comments can be posted.

Scientists Study Trajectories of Life-Bearing Earth Meteorites

Comments Filter:
  • Panspermia (Score:5, Insightful)

    by The Evil Atheist (2484676) on Thursday April 12, 2012 @08:20AM (#39656131) Homepage

    If we take it is viable, we should consider the panspermia theories more seriously.

    Only as a possible answer to the origin of Earth's life. It still doesn't answer the origin of life itself, wherever it may have started.

    • Re:Panspermia (Score:5, Insightful)

      by olsmeister (1488789) on Thursday April 12, 2012 @08:39AM (#39656239)
      No, but it could answer the question of how life managed to arise here on earth in a relatively short period of time, and would also exponentially expand the potential area we consider when we think about places that could have been suitable, both chemically and environmentally.
    • Re:Panspermia (Score:5, Interesting)

      by fatphil (181876) on Thursday April 12, 2012 @08:41AM (#39656261) Homepage
      I've seen arguments on a scientific mailing list in the last few days that this paper is based on false assumptions. It has assumed (too high) values for masses based on (too low) values for velocities based on the assuption that the meteorites are aiming at earth under its gravity, rather than aiming for the sun under its gravity and accidentally hitting earth on its way towards the sun.

      If you change the masses downwards to what they should be, then the chance of them getting through an atmosphere without breaking/burning up and denaturing all its alleged payload become minuscule.
    • by jellomizer (103300) on Thursday April 12, 2012 @08:46AM (#39656313)
      God? (Ducks!)

      I still follow the premise that Life originated on earth. As a random chemical reaction, that created simple DNA strains that that happened in an area where the environment stayed constant enough for those chemical reactions to persist but changing enough to allow the strain to change over time. The Chemical Reaction that didn't break down allowed for more chemicals to connect to the DNA strand and multiply.
      • Re:Panspermia (Score:4, Insightful)

        by ArcherB (796902) on Thursday April 12, 2012 @09:07AM (#39656501) Journal

        God? (Ducks!)

        I still follow the premise that Life originated on earth. As a random chemical reaction, that created simple DNA strains that that happened in an area where the environment stayed constant enough for those chemical reactions to persist but changing enough to allow the strain to change over time. The Chemical Reaction that didn't break down allowed for more chemicals to connect to the DNA strand and multiply.

        While thinking about it, the environment would not necessarily need to change to force the DNA to change (evolve). All the "environment" needs is to be stable enough to foster replication. The edges of such an area would provide the change in conditions needed for evolution to take hold. The bonds that were able to multiply at the edges and beyond did so. Those that were not able to didn't.

        An example would be ocean vents. This environment is rather stable and fosters life within it. Along the edges, where the conditions are not as favorable to the original life forms, most those that are venturing out will die. Those that don't die continue to reproduce, each surviving generation better able to survive further away from the vents until the need for the vents completely disappears.

        Just my $0.02 and I'm not a biologist. But I have stayed in a Holiday Inn and the concepts are not that hard to grasp.

        • Re:Panspermia (Score:4, Insightful)

          by mcgrew (92797) * on Thursday April 12, 2012 @09:20AM (#39656609) Homepage Journal

          From what I've read (which was a LONG time ago so further discoveries and theories may have developed), Earth had little or no oxygen when life developed, and the oxygen would have been a poisonous byproduct, like methane is to today's life.

          So life itself would have changed the environment, of course along with other such variables as volcanos, continental drifting, and meteors.

        • by Intrepid imaginaut (1970940) on Thursday April 12, 2012 @10:50AM (#39657823)

          All the "environment" needs is to be stable enough to foster replication.

          Its the bit between "dumb chemicals" and "things actually replicating" where we're a bit wobbly. If a stable environment were all it took we could have recreated the process many times.

          • by cusco (717999) <brian.bixby@gma i l .com> on Thursday April 12, 2012 @11:38AM (#39658515)
            I'm left assuming you have a couple hundred million years to let your experiment run, then? Good grief, I can set up a wireless mesh network and let it run and connectivity will be perfect for years until that moment that a train is going past, the janitor is running the vacuum with the bad motor brushes, and a tractor-trailer rig is parked in the fire lane simultaneously. If you wait long enough pretty much anything combination of things that CAN happen WILL happen, good or bad. The Urey-Miller experiment produced amino acids after only a few days, what if they had been able to expand the experiment and let it run for a few decades?
      • by Chris Burke (6130) on Thursday April 12, 2012 @10:42AM (#39657695) Homepage

        God? (Ducks!)

        Indeed -- not God, but Ducks! Some might say they're one in the same (especially the ducks). And given ducks' well-known sexual proclivities, a theory of panspermia where basically every object in the galactic vicinity, even those with no chance of the payload taking root, being "inseminated", makes a lot of sense.

      • by Eivind Eklund (5161) on Thursday April 12, 2012 @12:27PM (#39659421) Journal

        It wouldn't have been DNA; DNA is too complicated and has problems replicating without a bunch of machinery. RNA is one possibility, though I personally have the feel that it is too complicated as well. One example of a hypothesed simpler pathway is Cairn-Smith's Clay hypothesis (http://en.wikipedia.org/wiki/Abiogenesis#Clay_hypothesis) though experiments indicate that clay crystals likely aren't stable enough to work for this purpose. However, there only needs to be some kind of material with the right properties, and then evolution rapidly creates variation and more advanced structures. (For more on abiogenesis, you may want to see the nice talk.origins FAQ at http://www.talkorigins.org/faqs/abioprob/originoflife.html [talkorigins.org])

    • Re:Panspermia (Score:5, Informative)

      by socialleech (1696888) on Thursday April 12, 2012 @08:54AM (#39656383)
      You should read about the Miller-Urey experiment [wikipedia.org].

      For those to lazy to read about it, scientists have created all of the amino acids required by life, using nothing but inorganic compounds, by recreating the atmospheric conditions of early Earth.

      Life may or may not have originated on Earth, but we tested it and found that it could have. If it could have been created here, using nothing but the things that the universe placed here, why couldn't it have also developed else where? Are we the seeding planet of the galaxy/universe? Were we seeded? Or is life just incredibly common?
      • Re:Panspermia (Score:2, Informative)

        by Anonymous Coward on Thursday April 12, 2012 @09:46AM (#39656915)

        You're not still dragging out that tired old experiment, are you? Have you figured out how many orders of magnitude (both in terms of probability and complexity) bare amino acids are away from the simplest self-replicating thing we have found on earth so far? You'll need a lot more experimental evidence than just Miller-Urey to bridge the gap between inorganic compounds and life.

        (Yes, there are experiments that show self-replication of specially-designed ad hoc molecules, but the experimenters have to provide all the raw materials in just the right amounts for those experiments to work. Not exactly realistic pre-biotic conditions.)

    • by Barbara, not Barbie (721478) <barbara@hudson.gmail@com> on Thursday April 12, 2012 @11:06AM (#39658017) Journal

      If we take it is viable, we should consider the panspermia theories more seriously.

      Only as a possible answer to the origin of Earth's life. It still doesn't answer the origin of life itself, wherever it may have started.

      So you mean mom was right - you are evil alien spawn?

    • by tinkerton (199273) on Thursday April 12, 2012 @11:09AM (#39658075)

      I'll offer a view that goes the other way round, that of the irrelevance of panspermia. Life originated on earth because under the right conditions that is inevitable. Incoming meteorites with life or predecessors of life wouldn't have made any difference. Life on other planets is hard. Incoming seeds originating from earth wouldn't make any difference.

      If you look at the origins of panspermia theories however, they're of the silly kind: "life is very difficult to start so it must have come from elsewhere".

  • by alen (225700) on Thursday April 12, 2012 @08:21AM (#39656139)

    humanoids walking on two feet with funny heads

  • so the culmination of mankind's civilization, scientific efforts, and technological achievements, is to go to some exoplanet, only to find some foot fungus some dinosaur had long before mankind ever appeared?

  • Place Bets Here (Score:3, Interesting)

    by flyneye (84093) on Thursday April 12, 2012 @08:27AM (#39656175) Homepage

    Hmmm, made it to other Earth-like planets instead of randomly catching a closer strong gravitational field or drifting randomly into nothingness.
    Even making Europa would be kind of like hitting a cockroach with a needle from across a football stadium.
    Oh to be the house, if this scientist ever landed in Vegas with a wallet-load... Sounds like someone needs to re-fill the ol' grant jar.

    • Apparently you've forgotten about gravity.

      • Re:Place Bets Here (Score:4, Insightful)

        by jochem_m (1718280) on Thursday April 12, 2012 @08:40AM (#39656249)
        and the fact that it's more like hitting any of a dozen cockroaches with a million needles...
        • by flyneye (84093) on Thursday April 12, 2012 @10:43AM (#39657711) Homepage

          To add to my Vegas theme, consider the planets are moving like a roulette wheel. Further consider that gravity could also act as a slingshot rather than a mitt, dependent on distance from the modifying source it approaches. The numbers of the odds just roll like cherries, bells and bars on a slot machine, the more criteria you add.

      • by flyneye (84093) on Thursday April 12, 2012 @10:36AM (#39657601) Homepage

        Which gravity? The Suns? Are you assuming the ejecta came out in a general direction available to magically put it under the weak gravitational field of planets and moons so distant it would be like trying to get a BB to stick to a magnet by throwing it across the stadium? Did you not take into account how many directions are available that do not line up with the motions of our Suns hub of planets and asteroids? If it went in an upwards direction relative to our position around the sun, even nearby gravity would steer it only a bit as it flew at amazing speeds through the vacuum to nowhere in particular. Reach a distant system from there? Did you win the Mega-millions jackpot? No? Probably just some organic space crap floating somewhere to this day.
        It's probably nicer to think of it in the role that this story imagines it, just not very likely. I just can't make myself see it. I'll see it when I believe it or visa versa, whatever.

        • by Electricity Likes Me (1098643) on Thursday April 12, 2012 @11:12AM (#39658115)

          You do realize the solar system is not necessarily aligning its orbital plane with the galactic orbital plane, and that the volume of the galaxy around it's orbital plane is enormous?

          Something going "up" isn't heading out of the galaxy necessarily. In fact, unless it achieves galactic escape velocity, or falls into a conduit of unusual gravity interactions, then it's going to be orbit in and be captured by something, somewhere, eventually.

          • by flyneye (84093) on Thursday April 12, 2012 @11:31AM (#39658401) Homepage

            Then how many degrees of direction did stuff go, how did it disperse the further it got, how much useful material will fall in a useful place at what stage of development and potential for survival of the place then to find the time needed and then to have potential to rise above any other "geo- sperm" from " competing" sources. The more I think about this the more I get like Hawking about contacting aliens. There are just so many things that seem to work against this, I'm not seeing odds I can live with yet.
            Good point, BTW.

        • by cusco (717999) <brian.bixby@gma i l .com> on Thursday April 12, 2012 @12:03PM (#39659013)
          You need to read up on the dynamics of space flight, and take a look at the sheer volume of material ejected. You are aware that there are quite a number of rocks from Mars and the Moon here on Earth, aren't you?
          • by flyneye (84093) on Thursday April 12, 2012 @02:35PM (#39662137) Homepage

            I'm thinking of all that and considering the sheer volume of null targets and trajectories that are more likely even in the face of gravity if you consider the wide splatter trajectory. Then there's the other thought that there might be an ejection of something a bit more chunky and less dispersed and what could keep it from finding a chance trajectory that would take it to a viable planet and still be able to make it to evolved life in this amount of time.
            Not sure how well rocks evolve or if they hold enough potential to make the dif, What amount of material would be feasable in what environment and the chances for finding that environment.
            I can't deny that bits from here end up there and visa versa, But I'm beginning to see success in this being equal in odds to having a viable million dollars land on ME! lol.

    • by exploder (196936) on Thursday April 12, 2012 @09:34AM (#39656745) Homepage

      Astounding! With just a few minutes of thought and your superior intuition, you've dismissed the result of careful calculation and decades of training on the part of this group of scientists. Imagine what a genius of your magnitude could accomplish from within the scientific system...it truly staggers my humble intellect! But I'm sure you're working on much more important things.

    • by Chris Burke (6130) on Thursday April 12, 2012 @09:45AM (#39656895) Homepage

      Even making Europa would be kind of like hitting a cockroach with a needle from across a football stadium.

      True. Now explode a pile of trillions of needles and see if any one of them hit the cockroach.

      Oh to be the house, if this scientist ever landed in Vegas with a wallet-load...

      If the bet was that any of the visitors to Vegas would win the slot machine jackpot, the house might not be as willing to make the wager as you.

      Of course they'd only make that decision after doing what this scientist did, and actually calculating the expected pay-out. Estimating probabilities by gut feel isn't going to make you a winner in Vegas, even if you are the house.

      • by flyneye (84093) on Thursday April 12, 2012 @11:02AM (#39657963) Homepage

        I dunno about a trillion. Let's add that to the mix though.
        If it were that means the ejecta really splattered like Gallaghers melon in a lot of directions, but also that smaller amounts went with each "packet". perhaps a few "needles"were icy raindrops and hit. Then you face odds of survival. How's earthlife going to do as an ice chunk of earth water or frozen mudball on the surface of an icy moon? Of course the odds of these raindrops (which are still dispersing further from each other, the further they travel in this splatter scenario. This makes the odds of further planets getting a survivable amount of "geo- sperm" less than Europas.
                Even then we must consider the many directions it could go. We're not too far from the edge of the Milky- Way, did it go toward or away? Even up or down from that perspective are options. Then let's not forget gravity. This stuff could be flying around space in chunks or pieces to this day and not land anywhere.

    • by mattr (78516) <mattr@@@telebody...com> on Thursday April 12, 2012 @10:11AM (#39657255) Homepage Journal

      Actually Martin Lo discovered low energy gravitational paths or "superhighways" that would allow objects like space probes and maybe rocks to travel all around the solar system without power. These calculations were used in the Genesis probe NASA project IIRC.
      http://en.wikipedia.org/wiki/Interplanetary_Transport_Network [wikipedia.org]
      http://genesismission.jpl.nasa.gov/gm2/team/people/lo/interview1.htm [nasa.gov]

    • by onyxruby (118189) <onyxrubyNO@SPAMcomcast.net> on Thursday April 12, 2012 @11:15AM (#39658169)

      More like hitting a cockroach with a needle from across a football stadium, and you have millions of needles being launched at speeds well high enough to leave orbit. And then every so often you fire your needle cannon again and again.

      To put this in perspective, all you have to do is look at the moon. The chances of any given spot on the moon being hit by an impact are incredibly small, so small they are astronomical. However when you look at the moon, you can see the entire thing is covered with impact craters. Your proverbial needle is being fired at your proverbial cockroach in large quantities, again and again. Sooner or later your cockroach /is/ going to get hit by a needle, a second needle and so on.

      It also helps that their are what you could conceptually think of as gravity highways in space. Now you've discovered that your needles aren't just firing across the stadium randomly, but that the cannon is at least firing in their general direction.

      http://www.popsci.com/military-aviation-amp-space/article/2009-09/scientists-map-out-gravitational-space-highways [popsci.com]

      • by flyneye (84093) on Thursday April 12, 2012 @11:46AM (#39658659) Homepage

        O.K. this has come up in this thread and this is a better example of the space highway thing. Thank you.
        This spins the odds back down to something a bit more in grasp, but the viability/distance/dillution thing vs. finding a suitable planet in a suitable age of development is still giving me pause. Although the enormity of time does help a bit.
        Good one.
        I wish slashdot would implement a feature where we could explode any parent and its children so the group could see the conversation and we could bounce ideas off each other. That would've helped my intent with this, as the Vegas theme seems to be going nowhere.

        • by onyxruby (118189) <onyxrubyNO@SPAMcomcast.net> on Thursday April 12, 2012 @12:19PM (#39659287)

          I don't think you were trolling, which I think some of the other posters may have assumed. In essence, I'm conceding your point that for any given piece of debris to make it to a given location is absurdly low, even by astronomical standards. Certainly the odds are so bad that the bet probably would not be legal is Las Vegas.

          The thing that makes this paper viable though is that I don't have one piece of debris or just one shot. A large impact like the one that wiped out the dinosaurs could make millions of pieces of debris large enough to survive entry. Repeat this enough times over the years, take into account natural gravity paths between objects and /some/ of those pieces are going to make it to other planets. Give enough time and some of those pieces will even make it to other solar systems.

          The meat of the matter is calculating all the "x's" and "y's" that make up the equations. Think of it as being similar to the Drake equation. The more we learn about things like the popularity of planets in other solar systems, the better we can place a value on the given "x" or "y" that is used to come up with the answer.

          Or to use your gambling scenario in Las Vegas. Chances are really good for any given bet (piece of debris) that it's going to lose and that the house will win. Certainly in the long run the house is the consistently safer bet to put your money on.

          That being said, if you have enough gamblers (pieces of debris) gambling enough times (another piece of debris) eventually someone will win a jackpot (bacteria survives re-entry). How big that jackpot is (bacteria can live and reproduce on another planetary body) and whether or not it become headline producing (bacteria evolves into intelligent life) are entirely up to conjecture. The logic is scientifically sound, the only question is what are the odds, and that is what the scientific paper was trying to address.

          • by flyneye (84093) on Thursday April 12, 2012 @02:44PM (#39662321) Homepage

            Give this man a cigar!
            That brings us closer to fruition than any post yet.
            I still have reservations about timeline and possibility of reaching somewhere that bacteria could eventually work up to legs and cable television, but now I would at least drop a small bet on the table, just in case.

          • by flyneye (84093) on Thursday April 12, 2012 @02:48PM (#39662403) Homepage

            It could be too that most usually take my cynicism for trolling, but I am fairly jolly today and it has some bearing.

            I still think the /. system could benefit from including some advanced thread abilities to facilitate group oriented discussion in a round table style. Checking messages doesn't always show whats going on elsewhere in the thread.

  • Sub 1cm Ejecta (Score:5, Interesting)

    by RivenAleem (1590553) on Thursday April 12, 2012 @08:27AM (#39656177)

    How do objects this size survive the trip through the destination planet's atmosphere?

  • by SJHillman (1966756) on Thursday April 12, 2012 @08:28AM (#39656183)

    There are those who believe that life out there began here
    Flung far across the universe, before there were tribes of humans...

  • by Trapezium Artist (919330) on Thursday April 12, 2012 @08:30AM (#39656205)

    I've made a quick scan of the underlying academic article by Hara et al., along with one of my colleagues in a meeting here, who is closely involved in the issue of planetary protection (i.e. making sure that our spacecraft don't "pollute" the solar system bodies they fly to and land on).

    Of course, this is a known issue in general: after all, there are meteorites on Earth which we know came from Mars, so the converse is obviously possible. But extending this to moons of Jupiter, Kuiper Belt objects, and even exoplanetary systems, and finding that a significant number of Earth rocks may have been dumped there is interesting. So, the article is worth a more careful read.

    However, my antennae were sent into a state of high agitation when I saw that the article has been posted on the arXiV following its having been accepted to the infamous Journal of Cosmology. We've discussed that here before: I invite you to view the journal website (easily found by googling) and decide for yourselves how reputable it is.

    Which raises the question of why Hara et al. chose to publish there. That I can't answer, obviously, but will keep it firmly in mind as I read the paper in more detail.

    • by CrimsonAvenger (580665) on Thursday April 12, 2012 @09:36AM (#39656761)

      Which raises the question of why Hara et al. chose to publish there. That I can't answer, obviously, but will keep it firmly in mind as I read the paper in more detail.

      Because it's rather long on speculation and short on facts?

      And because there's no way to test any of this for a very long time to come?

      • by Trapezium Artist (919330) on Thursday April 12, 2012 @09:54AM (#39657001)

        Well, in principle the paper is a fairly simple series of mathematical equations which you could actually work out on the back of an envelope. The devil though is in the details, namely the numerical parameters input to those equations. While many of those are straightforward and well-known, some may enter that category of WAGs (wild-assed guesses), and it's quite possible that the equations are particularly sensitive to (some of) those. That's why it's worth reading, to try and figure out where the issues may be.

        As for the testability side, you're right, of course: very hard. But again, since we know of Martian rocks having made it to Earth via this mechanism, we can at least start to use some hard numbers based on that to try and constrain the likelihood of the Earth rocks having made it to other planets / moons.

  • by mevets (322601) on Thursday April 12, 2012 @08:50AM (#39656343)

    If we share common ancestry, that means we might find alien life tasty and nutritious. ... to seek out new life and new civilizations, to eat.

  • by tekrat (242117) on Thursday April 12, 2012 @09:25AM (#39656655) Homepage Journal

    So, without realizing it, we're ALREADY colonizing our galaxy. Life bearing rocks from earth hit other planets, those planets also experience trauma sooner or later, ejecting their rocks into space millions of years later, after life had caught on, and so on and so on.

    Therefore, Earth may be a colony of some other civilization from billions of years ago, or, we're creating colonies as we speak.

  • by rossdee (243626) on Thursday April 12, 2012 @09:36AM (#39656763)

    I could believe that some simple life form could suvive on a rock travelling through space for millions of years, but I don't see how it would have survived the heat of the impact event that blasted it beyond escape velocity in the first place

    (at least life as we know it, Jim)

  • by um... Lucas (13147) on Thursday April 12, 2012 @09:40AM (#39656809) Journal

    How can we study the trajectory when we don't know:

    When the asteroid hit?

    The earth's position relative to the sun, the other planet, and the rest of the stars in the galaxy at the time of impact.

    The direction from which the asteroid hit us.

    The size of the asteroid.

    For starters....

  • by jmulvey (233344) on Thursday April 12, 2012 @09:45AM (#39656897)

    Panspermia is a very interesting/compelling theory. But I'd avoid telling anyone in academia that you're interested in an Earth genesis hypothesis other than evolution.
    You may just as well have told them that you're a pro-lifer, who voted for Bush, are home schooling your kids, believe in a balanced budget, and are a racist all in one sentence.

  • by Lluc (703772) on Thursday April 12, 2012 @10:25AM (#39657429)
    Assume we're just dealing with Carbon (molecular weight 12) here, and "well over 1 trillion tonnes" is actually 2 trillion tonnes:

    number of molecules per gram = (Avogadro's Number) / 12 grams = 5.02E25 molecules/kg
    2 trillion tonnes = 2E15 kg
    (5.02E25 molecules / kg * 2E15 kg) = 1.004E41 molecules

    Surface area of sphere with radius of 20 light years = 4.499E35 meters^2

    1.004E41 molecules / 4.499 meters^2 = 223,091 molecules / meter^2 == 4.44 attograms of carbon per square meter.
    This is a pretty thin layer of material to survive reentry on some 20 light year distant planet.

    --------
    Alternatively, from google: ((Avogadro's number / (12 grams)) * (2 trillion tonnes)) / (4 * pi * ((20 lightyears)^2)) = 0.223099739 kilometers per liter = 0.5 miles/US gallon, which means we totally need to collect some gas guzzler tax on this material
  • by onyxruby (118189) <onyxrubyNO@SPAMcomcast.net> on Thursday April 12, 2012 @01:31PM (#39660727)

    Just a thought here, but I don't think re-entry would be that challenging for bacteria based life to survive. Most people think that what left of an asteroid is really hot when they land, but that just isn't the case. In fact asteroids have been touched right after landing and described as 'cool' in temperature.

    http://impact.arc.nasa.gov/news_detail.cfm?ID=1 [nasa.gov]

    If bacteria were in the core part of the asteroid that survived impact it should be reasonable to assume that the part that is cool to the touch never got hot enough to kill any bacteria that were inside it. The other two questions than become what kind of shock (g-forces) can bacteria survive? We know they can survive the shock of being launched into space, and without the squishy bodies that we have they may well survive the shock of re-entry.

    If we could determine the answers to those questions than really the only questions remaining are can bacteria adapt to their new home? We already know they live in places on earth that are very inhospitable by our standards. The only other real question is how long can they survive in space? We have documented cases of bacteria surviving in space for years at a time. If there is no real limit to how long they can survive in space than cross solar system colonization is all but inevitable.

If a subordinate asks you a pertinent question, look at him as if he had lost his senses. When he looks down, paraphrase the question back at him.

Working...