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Space Science

Murchison Meteorite Still Contentious 211

Posted by michael from the tainted-love dept.
An anonymous reader writes "The well-known 1969 meteorite that fell 60 miles north of Melbourne, Australia, remains remarkably contentious today. The 100 kilogram carbon rock : a) contains pre-biotic proteins and 12% water; b) harbors 50 amino acids not found on Earth; c) favors the tell-tale signature of biochemistry based on a dominant left-handed chirality, compared to random or racemic mixtures found in test-tube syntheses. While terrestrial contamination (even interior to the meteor) may discount this so-called 'Murchison meteor', its light isotopes of carbon and nitrogen suggest the left-handed amino acids not found elsewhere on Earth have the same ratios as the right-handed ones. This would not be the case if, say, bacteria was just making the left-handed ones after impact. Seems quite a controversy from down-under."
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Murchison Meteorite Still Contentious More

Murchison Meteorite Still Contentious

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  • Relevance? (Score:3, Interesting)

    by Vardan ( 172720 ) on Thursday February 13, 2003 @06:26PM (#5297713)
    You'd think that after they found what appears to be microscopic life (fossilized, rather) on Mars, it wouldn't be that big of a stretch.

    However, it is fairly interesting that that many amino acids are left-handed. Organic molecules tend to form in pretty much the same way in any given environment, so I'd think that if those aminos ARE from Earth, they'd be from someplace strange, like a hydrothermal vent. How they would've gotten onto a meteor from there, who knows.
    • Soviet Russia, that's where!

      I think the major importance of this is that the theory of evolution(which God could direct!) does not account for the switching of one set of amino acids to another. That means that these acids are not from Earth, or at the very least not from the epoch.

    • Re:Relevance? (Score:2, Interesting)

      by stratjakt ( 596332 )
      Except that the 'fossilized microbes' on the martian meteor can be completely dismissed by natural (non-organic) processes.

      I dont know enough about blingblongology to elaborate, I can merely regurgitate what I've learned watching 'UFO week' on the history channel.

      (Rant: WTF do UFOs, Loch Ness monster, bigfoot or Ghosthunting have to do with history?!)

    • Re:Relevance? (Score:2, Interesting)

      by kavau ( 554682 )
      so I'd think that if those aminos ARE from Earth, they'd be from someplace strange, like a hydrothermal vent. How they would've gotten onto a meteor from there, who knows.

      How about this: 10 billion years ago a gigantic asteroid hits earth, sending countless fragments of terran rock into space, many of them harbouring life in its early stages. Now, billions of years later, one of those galactic pieces of rubble happens to cross earth's path again. Hence the amino acids we found might be from earth's own past...

      Just a thought...

      • Re:Relevance? (Score:3, Informative)

        by helix400 ( 558178 )
        10 billion years ago a gigantic asteroid hits earth...

        The earth is only roughly 4.55 billion years old. [talkorigins.org]

        But that would just mean the asteroid in your example would only have to hit...say...2 billion years ago.

        • By 2 billion years ago, as far as we can tell, life was stablized in it's current chemical composition. If you want to get to the early days, when life would be experiementing with novel chemical forms, then you're going to have to go much closer to the formation of the planet. r

    • circular polarized light could forms L-amino acids (Score:5, Informative)

      by searleb ( 168974 ) on Thursday February 13, 2003 @09:12PM (#5298866) Homepage
      Recent research [cam.ac.uk] suggests that there is an excess of L-amino acids (the specific enantiomer used in life-proteins) found in space, suggesting that the chiral specific process involving circular polarized light (mentioned in the article) could have lead to the amino acids that were found on the Murchison (and other meteorites).

      From the article:
      Recently it has been discovered that an excess of L-amino acids is present in the Murchison and Murray meteorites indicating that a preference for L-amino acids existed in solar system material before there was life on Earth. This supports an idea, first proposed by Rubenstein et al. (1983, Nature 306, 118), for an extraterrestrial origin for homochirality.

      In this model the action of circular polarized light on interstellar chiral molecules introduced a left handed excess into molecules in the material from which the solar system formed. ...

      If our own solar system formed in such a region of high circular polarization, it could have led to the excess of L-amino acids which we see in meteorites and to the homochirality of biological molecules. It is possible that without such a process operating it would not be possible for life to start. This may have implications for the frequency of occurrence of life in the universe.

    • Re:Relevance? (Score:2, Interesting)

      by joethebastard ( 262758 )
      Meteoritics is a messy science, because measurements are never conclusive and explanations are always at least partially guesses. To analyze the chirality of the amino acids, you measure how much light it absorbs of different polarizations (circular dichroistic spectroscopy). To measure absorption, you must cut a thinsection; cutting something open always introduces contaminants. Explaining the chirality, once measured, is just as tricky- most scientists would just look at the excess of left-handed acids as proof of contamination.

      Isotopic data is even worse- it's easy to show some difference in a sample, as isotopes on this planet tend to be extremely isotropic, but proving anything with that is difficult. Amino acids make up a small percent of the sample of a chondrite, so the number of particle counts representing (from a secondary ion mass spectrometer, or similar device) them will be fairly low; this makes the relative error very high. Every bit of processing done on the sample introduces terrestrial atoms, and a spectrometer calibrated to look at specific atom masses won't know the difference between nitrogen from a meteorite's amino acid or from a hamster. How do you attach the isotopic excesses to the left-handed chiral amino acids?

      All this just to say: take meteoritics with a grain of salt. Every time I work in a meteorite lab, I take their claims a bit less seriously. It's a really cool, wonderfully hard area of science, but you have to deal with largely destructive and oft imprecise analytical techniques on a limited number of samples, all of which have been partially processed or contaminated.... with never enough funding. This group is doing a good job, but rarely in this field is any result ever conclusive.

  • Leftorium (Score:5, Funny)

    by The_Rippa ( 181699 ) on Thursday February 13, 2003 @06:29PM (#5297736)
    And chunks of it are now on sale at Ned Flander's Leftorium.

    Fan-diddly-tastic!
  • We really are all aliens!
  • there goes the human race! ;p

  • Sounds like lawyer talk to me!. (Score:5, Funny)

    by setrops ( 101212 ) on Thursday February 13, 2003 @06:32PM (#5297754)
    I m just a simple caveman, your fire scares me. These pre-biotic proteins you speak of are unfamiliar to me!

  • Let me ask this... (Score:5, Interesting)

    by Mullen ( 14656 ) on Thursday February 13, 2003 @06:32PM (#5297755)
    So if the big debate is whether these "rocks" from space contain the building blocks of life, but are being contaminated when they hit earth. Why don't we send up a robot (Or what have you) into space and collect some rocks that have not been on earth?

    To me, if you collected about 20 or 30 of these things, it would answer the question rather quickly. Yes, I know that does mean we would get rocks with ammo acids, but sitting waiting for the rocks to come to us seems to be a waste of time.
    • To me, if you collected about 20 or 30 of these things, it would answer the question rather quickly.
      Unfortunately, the theories I've heard suggest that the amino acids form in colder parts of space than here, and not very often, so the probe would have to go a long way, and gollect rather more than 30 rocks (Would you look under only 30 rocks on a beach to find evidence of life? Space is quite big, and life is less common there.) This would be very expensive and probably not vey conclusive, unless it happened that it found some amino acids quickly. A conclusive negative result could not be found this way.

    • don't we send up a robot (Or what have you) into space and collect some rocks that have not been on earth?

      No way! Haven't you read/seen The Andromeda Strain? We don't want to bring back a "super virus"!

      Instead, let's send lawyers into space to collect rocks. Entertainment industry and media lawyers. Yeah-- and marketing professionals. Perhaps politicians, too. We don't really particularly care if they come back or not, either!

    • Re:Let me ask this... (Score:4, Interesting)

      by odyrithm ( 461343 ) on Thursday February 13, 2003 @06:42PM (#5297813)
      but sitting waiting for the rocks to come to us seems to be a waste of time.

      erm... how exactly do we catch them would you suggest? pretty nippy little fuckers when there streaking at about 100k miles a second through space..

    • Re:reason why not (Score:5, Interesting)

      by davebo ( 11873 ) on Thursday February 13, 2003 @06:44PM (#5297820) Journal
      here's a couple of reasons I can think off the top of my head:

      1) we've got to get the ship someplace where there are "space rocks". a low-earth orbit really isn't going to accomplish that - you'd have to go to the asteroid belt for a ready supply. that's not easy. or, conversly, you land someplace where rocks may have accumulated (ie, the moon, mars).

      2) if you send a ship to a place with lots of space rocks, the ship is going to get hit by a lot of space rocks. shielding becomes a problem.

      3) if you land some place, you're stuck getting rocks next to where you land (like viking) or you've got to build a way to move around (like pathfinder)

      4) building a reliable, completely automated assay for amino acids is not trivial. if it's mobile, that's going to be even less trivial.

      • Agreed... but... (Score:4, Interesting)

        by joshuaos ( 243047 ) <ouroboros@freedo m e nt.com> on Thursday February 13, 2003 @08:10PM (#5298489) Journal
        All your reasons why collecting asteroids would be quite difficult are valid. I also think that it would be an interesting, and likely fruitful, way to answer this rathering important question. More importantly however, I think that we have lots and lots of other reasons to go get us some ansteroids. There's a big asteroid belt out there with a lot of useful minerals, where we don't have a pesky ecosystem to worry about destroying, we can do all the damn mining we want on any unocupied asteroids we should find out there.

        Although of course this would be an imense venture, probably requiring a permanent base on the moon and who knows where else, but it would remove the dependency of technology on earth from our fragile ecosystem, and let's face it, we've taken a lot of the easy metals out of the ground, and it's only going to get harder and harder to find. Another important point to remember is that although going up is expensive, going down is dirt cheap. ;)

        My two cents. Joshua

        • The "Asteroid Belt" is still pretty much empty space, just a bit less empty than most space out in that part of the solar system. You might as well just head straight for Mars and get your rocks there if looking for signs of life.
        • There's a big asteroid belt out there with a lot of useful minerals, where we don't have a pesky ecosystem to worry about destroying, we can do all the damn mining we want on any unocupied asteroids we should find out there.

          Yes, we wouldn't want to do any mining on the occupied asteroids, would we? And make sure to bring a towel!

      • You could simply send probes to the Lagrange points. It is highly likely that each L point will contain a mass of rocks...the problem is that they could contain a mix of terrestrial (blown off by meteorite strikes) and extraterrestrial rocks. Theses points are much closer than the asteroid belt.


        As for the asteroid belt and collision protection...not a problem. The asteroid belt is NOTHING like what you see on Star Wars movies. It is not a chaotic hoard of roaving rocks. There is a great deal of space between rocks and they are not wildly roaming about in the belt. You can easily (and we have done it every time we send out a deepspace probe to the outer planets) send a craft through the belt without coming anywhere near any rock.


        Just pick a rock or two and send a probe. Your chances of finding anything are likely minor as it is doubtful that EVERY space rock is going to contain appreciable amounts of amino acids or their precursors.

    • Re:Let me ask this... (Score:4, Insightful)

      by br0ck ( 237309 ) on Thursday February 13, 2003 @07:03PM (#5297910)
      Your idea is a valid one and scientists are currently thinking that the best chance to find life in our solar system will be on Jupitor's moon, Europa. However, it is actually extremely difficult to keep the robot probe itself from carrying contamination since modern electronics can't take the extreme heat needed to kill resilient strains which could possibly destroy any life on that planet. Recently scientists have been putting more effort into trying to figure out how to explore Europa [spacedaily.com] without contamination.

      Contamination has already been shown to occur easily. The first Apollo mission found the moon to be sterile, but later Apollo missions found strep bacteria [guardian.co.uk] from previous missions. Deeply buried in ancient Antarctic ice, Lake Vostok is an enviroment that is thought [bbc.co.uk] to contain ancient life forms, but scientists are reluctant to explore the lake until contamination can be prevented. Bacteria has already been found in drilling to just above the top of the buried lake.

      • Re:Let me ask this... (Score:5, Informative)

        by CaptainStormfield ( 444795 ) on Thursday February 13, 2003 @07:21PM (#5298099)
        The first Apollo mission found the moon to be sterile, but later Apollo missions found strep bacteria from previous missions.

        That's a little misleading. Apollo 12 found microbes inside the camera of Surveyor 3 (which landed three years before). Its not like the strep bacteria are colonizing the moon -- I'm pretty sure that the lunar environment is still sterile.

      • One can imagine... (Score:3, Insightful)

        by neurojab ( 15737 )
        I think of civilization and technology as a major/minor cycle. Technology doesn't always advance... sometimes it's lost. Sometimes entire advanced civilizations are wiped out and a hunter-gather society emerges in its stead. Now imagine this happening to the whole of civilization. Imagine we DO go to Europa, and leave behind a streptococcus. We then lose spacefaring technology for a period of a million years, then regain the technology to complete the cycle.

        The new civilization travels to Europa, and finds... simple creatures with earthlike amino chains! At that point we will have discovered extraterrestrials.

        Of course one has to wonder if the earth-europa contamination hasn't already happened millions of years ago by an ancient civilization now forgotten. Or perhaps it was vice versa... spooky.


    • Because there's a Googleplex cubic kilometers of space for every freaking rock thats worth collecting.
  • wow, this is really interesting... I've never heard of this meteor before, however I find this really cool.
    I wonder why this was never mentioned in any of my chemistry, physics, geology, or biology classes in high school or college (last 10 years)?

    on a side note... is anyone else creeped out by the picutre of the guy [astrobio.net] halfway down the page?
    *shudder*

  • The real test... (Score:4, Funny)

    by Anonvmous Coward ( 589068 ) on Thursday February 13, 2003 @06:33PM (#5297763)
    .. is find and orifice and pump the meteorite full of shampoo. If all the 'life' on it dies, then it's extra terrestrial. :D


    • > .. is find and orifice and pump the meteorite full of shampoo. If all the 'life' on it dies, then it's extra terrestrial.

      Ah, I wondered why my alien abductors did that!

  • Don't get too excited yet. (Score:3, Interesting)

    by Sheetrock ( 152993 ) on Thursday February 13, 2003 @06:34PM (#5297768) Homepage Journal
    Earth bourne bacteria could express pre-biotic proteins similar to those discovered in the presence of the right catalysts. Chirality studies can be misleading; nearly 50% of a random sampling of biotic material will confirm the existence of left-handed biotes without revealing anything at all about the total material. Additionally, I'd disagree with the position that the presence of light isotopes in the left-handed chiratic samples in and of itself discounts the possibility that the amino acids were created by Earth bacteria.

    The point is simply that you cannot infer any biochemical 'facts' about extraterrestrial compounds once they've been exposed to Earth's lifeforms.

  • Just want to ask.. (Score:4, Interesting)

    by Visaris ( 553352 ) on Thursday February 13, 2003 @06:35PM (#5297771) Journal
    How would organic material from earth make it into the center of an object like this? Can the force of the impact explain that some how? Just want to know : )
    • Rocks are porous. It's unlikely scientists are going to find a pigeon in the center of a meteorite, but anything dust particle or smaller could make it in.
    • "How would organic material from earth make it into the center of an object like this? "

      I used to have a container of mayo in the fridge that'd prove to you it's not impossible for life to grow in surprising places, but it'd also kill your interest in learning how it managed that.

  • Only on earth... (Score:2, Insightful)

    by ackthpt ( 218170 )
    Only on earth could it be hotly debated: life on other worlds, no life on other worlds, over a meteorite.

    On thing seems abundantly clear: There's no life left on the world it came from. I hope ours doesn't pose a base for such a heated debate on some other world species some day.

    • The seems abundantly presumptuous. If it broke off of somewhere 4 billion years ago, or even 100 million years ago, it's entirely possible wherever it came from has evolved life and hasn't yet failed.

      In fact, it seems odd to me that no one has yet suggested it originally came from Earth. Think about it. As I understand it, there wasn't much of an atmosphere before life, so it's feasible that for one reason or another a hunk flew off. I'm not about to calculate the path it would have flown, or even argue the likelihood, but I don't think it's impossible.

      For reference, the nearest star is Proxima Centauri [gridclub.com], at ~25,000,000,000,000 miles. I looked a number of places and found no consensus on the speed of the meteorite, but the larger number I saw was 20,000 mph. At that speed it would have taken ~150,000 years to get here. Since that is assuming a straight line among other things I feel it is reasonable to conclude wherever it came from it took longer than that, if it was near a star we know about.
      (That really doesn't have anything to do with my point. But I did the research and math so I figured I might as well share it.)
      • No, there was an atmosphere before life. It wasn't like our current atmosphere though. It was high in ammonia, methane, carbon dioxide, carbon monoxide and water vapor. When the blue-green alge came along, they started converting this atmophere into our current atmosphere.
    • Only on earth could it be hotly debated...

      Um, that's just silly. Until we make contact with intelligent life on other planets, we have no way of knowing whether or not those intelligent life forms on other planets (assuming they exist) would debate the matter.

      On thing seems abundantly clear: There's no life left on the world it came from.

      There's no evidence that it came from a world. Organic compounds form in interstellar space, and it has been speculated that life (or something eerily like it) could form in space. Or not, but in any case, I think you're trying to read far too much into this.

  • Auto-Google (Score:4, Interesting)

    by jjjefff ( 525754 ) on Thursday February 13, 2003 @06:39PM (#5297792) Homepage
    Perhaps even more interesting (especially if you're already familiar with the debate) is the fact that highlighting a word or phrase on that page causes a browser window to pop up with the results of a Google search on that word or phrase...

    Not technically very difficult, but a cool idea...
    • Is that like taking the last sentence the computer guy tells you and rephrasing it in the form of a question?

  • Could these things be ejecta from... (Score:4, Insightful)

    by exp(pi*sqrt(163)) ( 613870 ) on Thursday February 13, 2003 @06:40PM (#5297799) Journal
    ...Earth. They could be of terrestrial origian and thrown up a billion years ago or so by volcanic activity or a large meteor collision with earth, eventually arriving on earth again after a billion years of orbiting near the Earth. They could be leftovers from a very early time when left handed and right handed life coexisted on Earth.

    • Well, lets examine what we know. The meteorite hit which planet? Yes, Earth. It looks like comet material, so the comet must have a trajectory that goes near which planet? Earth, very good. So, if the comet previously came in contact with a planet, which planet would that most likely be?

      I think you see the point.

  • Hmmm (Score:5, Insightful)

    by mao che minh ( 611166 ) on Thursday February 13, 2003 @06:40PM (#5297800) Journal
    "c) favors the tell-tale signature of biochemistry based on a dominant left-handed chirality, compared to random or racemic mixtures found in test-tube syntheses."

    .....compared to random or racemic mixtures found in test tubes on Earth. We have yet had no other "lab" from which to study life and it's building blocks (life as we know it: carbon based and mostly made of water). Therefore, the sudden appearence of such components from the stars might very well appear to be "based on dominant left-handed chirality" when compared to the billions-old formula we have here on our planet.

    We also don't know how the environment of space will effect amino acids contained in the rock. Since these amino acids (and other material) are foreign, then how do we know that it isn't natural for them to be collected in such a manner?

    Never forget the scientific method. You have to ask questions. After you're done asking questions, submit to your peers for them to ask questions.

    It really isn't compelling at all. It's similar to how UFOlogists focus on half truths and anamolies that confirm their theories, while ignoring the evidence that shows how 90-95% of all sightings are reasonably explained (the tons of disconfirming evidence). They also turn their nose up to the community and the world, effectively becoming the closed-minded character that they try to call the real scientists: Real scientists submit their work to thousands of peers and accept feedback and analysis. Psuedoscientists do not, and yet they call the critical thinkers that reject their ideas closed-minded.

    OK, rant over.

    • They also turn their nose up to the community and the world, effectively becoming the closed-minded character that they try to call the real scientists: Real scientists submit their work to thousands of peers and accept feedback and analysis. Psuedoscientists do not, and yet they call the critical thinkers that reject their ideas closed-minded.

      I have a very well though out and reasoned rebuttal which is perfectly formed and completely undebatable. Howerver I refuse to share this information with you because you're such a boob...

      -dameron :)

  • Chirality (Score:5, Informative)

    by BWJones ( 18351 ) on Thursday February 13, 2003 @06:42PM (#5297815) Homepage Journal
    From the article: A curious aspect of Earth's life forms is that they contain (with few exceptions) only left-handed amino acids. In contrast, when scientists synthesize amino acids from nonchiral precursors, the result is always a "racemic" mixture - equal numbers of right- and left-handed forms. Scientists have been unable to perform any experiment that, when starting with conditions believed to emulate those of early Earth, results in a near-total dominance of left-handed amino acids, says George Cody, a geochemist at the Carnegie Institute of Washington.

    In many cases, the levorotary forms are lower energy structures and would be favored during synthesis. The fact that many L based systems are almost exclusively so is dependant upon the larger structures that are based upon amino acids and other small molecules. Often a D form of a molecule will not be able to integrate into a L structure.

    This is not to say that D forms cannot have biological activity however as there are many instances I can think of where racemic mixtures of molecules can have biological activity. For instance, the 2 chiral forms of carvone have completely different smells due to receptors in the olfactory epithelium being activated by each of the racemic forms.

    Some instances of similarity of molecular structure but different chirality have also resulted in catastophies. One only has to think of MPTP poisoning the neurons of the substantia nigra or potentially thalidomide.

    • I haven't read anything specifically about this, but is the chirality of the amino acids used in protein synthesis at all related to the fact that the DNA molecules they are ultimately synthesized from have a handedness to them as well? (As DNA is usually in the B-form, which is right handed) I realize that there is an mRNA intermediate before actual translation, but wouldn't the enzymes that handle transcription need to have a particular handedness to process DNA?

      Teleogical, I know, but what we see now is perhaps, again, the end result of the fact that (1) While RNA was probably the original genetic material, DNA is a more efficient, less error-prone way to package code, so DNA eventually dominated (i.e., replicated faster) (2) DNA has a preferential handedness simply because of basic chemistry. The left handed Z-form is not as stable as the right handed B-form. (3) While both RNA and DNA can spontaneously form base pairs if sitting in a sea full of nucleotides, and while RNA can act like an enzyme, replication happens much faster if you can recruit proteins. Somehow DNA (and probably RNA before it) preferentially chemically bound to certain amino acids/peptides/proteins, and the machinery of the Central Dogma appeared after a billion or so years of chemical "trial and error". (4) Since DNA has a particular handedness, the proteins that handle it mostly have a certain handedness as well. (5) This handedness is derived from the fact that these proteins are composed of amino acids of a uniform chirality.

      Maybe?

      • Re:Chirality (Score:5, Informative)

        by abhinavnath ( 157483 ) on Friday February 14, 2003 @01:59AM (#5299969)
        That's an interesting theory you've got going there. Unfortunately, the handedness of DNA does not determine the chirality of amino acids used.

        The handedness of DNA is determined by the handedness of the sugar in its "backbone" - that is, B-DNA is right-handed because it contains D-deoxyribose instead of L-deoxyibose. A hypothetical DNA molecule formed using L-deoxyribose would have a left-handed B-DNA helix. (Now remember that the A, B and Z forms of DNA are artifacts of it being a double helix. These are three different stable conformations of a DNA double helix (local minima). Z-DNA is globally unstable, and unusual in nature, because it requires some of the bases in DNA to flip from their usual "anti" conformation relative to deoxyribose to a less stable "syn" conformation.)

        There is no reason that an RNA-based "enzyme" (similar to parts of a ribosome) would inherently prefer one isomer of an amino acid over another. It's just that once machinery had evolved to synthesize/utilize one isomer, it becomes very inefficient to use a whole 'nother set of enzymes for the other isomer of the same amino acid (unless you really really need a D-amino acid, as in bacterial cell walls). Dumb chance dictated that L-amino acids were chosen, for the most part, over D-amino acids.

        Interestingly, the D/L conventions of sugars and of amino acids both derive from the isomers of glyceraldehyde, the simplest 3-carbon sugar. Whether a compound is D or L is determined by the orientation of the major group on the 2-carbon, when the molecule is drawn in the Fischer projection. The D/L convention is just that, a convention, and does not affect the chemical or optical properties of compounds in any consistent fashion. (That is, D/L names are totally distinct from dextrorotatory/laevorotatory names, which denote optical activity. It sucks, but there it is.) Your parent post is just flat out wrong when it says L-amino acids are energetically more favored than D-amino acids.
      • I realize that there is an mRNA intermediate before actual translation, but wouldn't the enzymes that handle transcription need to have a particular handedness to process DNA?

        Absolutely. Yes, this also presents a bit of the chicken-egg problem as well when it comes to molecular evolution, but is most likely related to the success of DNA as a information storage form.

  • This will remain controversial for scientists until one of two things happen.

    1. There are other samples from the places that they claim the meteorite is from to compare to that are of the appropriate age.

    or...

    2. The current crop of scientists have passed on. There is a joke about the physics community that theory doesn't really advance until the last generation has died off...;)

    I hope it's the former rather than the latter. That implies a more than a few expeditions or at least sample returns to the source of origin...which we all know what that is! ;)

  • contentious ( P ) Pronunciation Key (kn-tnshs)
    adj.
    Given to contention; quarrelsome. See Synonyms at argumentative. See Synonyms at belligerent.
    Involving or likely to cause contention; controversial: "a central and contentious element of the book" (Tim W. Ferguson).

    Yeah, ok.
  • Now this is interesting, because no life on Earth uses left-handed Animo Acids. They all use Right-handed ones. Both left and right occur 50/50 in nature, so any ratio of left handed Amino Acids that outweighs right is...

    Well...

    Something would have had to *make* the left handed acids...

    • Re:Left-handed? (Score:3, Insightful)

      by Xtifr ( 1323 )
      no life on Earth uses left-handed Animo Acids.

      Quite the contrary, all life on Earth uses left-handed (levorotary) amino acids. Typing "levorotary" into Google and clicking "I'm Feeling Lucky" returns this short-but-informative article [swau.edu].

      • Re:Left-handed? (Score:3, Interesting)

        by benzapp ( 464105 )
        However, in many cases only dextro varieties of pharmaceuticals are active.

        D-methamphetamine is used as an illicit stimulant. L-methamphetamine is used in those Vicks inhalers and is nearly inert in humans.

        Dexedrine is pure dextroamphetamine, where as levoamphetamine is not even sold. It is however part of the Adderall mixture.

        • Sure, and lots of organically-created compounds are right-handed, e.g. most sugars (hence the name "dextrose"). But the important part in this discussion is that (unlike what the original poster stated) earth-life-derived amino acids are levorotary, just like the ones found in this meteor, which supports the contention (but not necessarily the conclusion) that terrestrial contamination is involved.

          If earth-life used l-amino acids, and the meteor contained mostly r-amino acids (or vice versa), then we'd have something really interesting to ponder. As it is, the evidence is ambiguous and leaves us with more questions than answers.
  • Is this another debate as to which is better? Lefties or Righties?

  • Hold on a sec! (Score:4, Interesting)

    by FreeLinux ( 555387 ) on Thursday February 13, 2003 @07:05PM (#5297921)
    amino acids not found elsewhere on Earth

    Every time I hear this I get rather angry. Are these people really so arrogant as to be absolutely certain that we have already found and identified ALL amino acids, presently on earth? Is there no chance at all, that these same amino acids could be present somewhere (bacteria in deep sea vents, perhaps) and we simply haven't found them yet?

    I'm not trying to suggest that, the amino acids found on the meteor are not extra terrestrial. But, I just get angry at these people who seem to feel that they have seen everything that there is to see on terra firma.

    • Re:Hold on a sec! (Score:5, Insightful)

      by zenyu ( 248067 ) on Thursday February 13, 2003 @08:03PM (#5298431)
      amino acids not found elsewhere on Earth

      Read it again, slowly.

      It doesn't say "amino acids that do not exist elsewhere on Earth."

      Simply that they haven't been found elsewhere, including, I assume, on rocks near the impact crater.

    • as a couple other people said they are only saying that we havn't found them, not that they don't exist on earth. Furthurmore I think the specifics of the statement may be irrelevant. I'm not familiar with biology but I'm assuming that is a certain system they would be able to indetify all the amino acids there most of the time. If they are able to identify all the amino acids in the area where the rock fell then it serves to reason that those amino acids didn't came from the immediate impact area. The next logical conclusion is they were picked up somewhere else (in space maybe?) or by contamination from researchers carrying amino acids from elsewhere.

    • Re:Hold on a sec! (Score:3, Insightful)

      by g4dget ( 579145 )
      Every time I hear this I get rather angry. Are these people really so arrogant as to be absolutely certain that we have already found and identified ALL amino acids,

      That's why it says "not found", not "non-existent".

      What matters for the meteorite is whether these amino acids are common enough on earth to have contaminated the meteorite, and the answer to that is clearly "no".

    • Re:Hold on a sec! (Score:3, Insightful)

      by Arcaeris ( 311424 )
      Gah! Of course there are more amino acids that we don't know. An "amino acid" is a broad set of compounds.

      However, the importance is in certain amino acids, and the configuration found in almost every life form we know. The fact that nearly every biologically-used amino acid favors one enantiomer over another in biological systems is of great significance.

      There are exceptions to every rule, but it's odd to see our freaky trends differ on a space rock.

  • chirality (Score:3, Funny)

    by psychogentoo ( 582658 ) on Thursday February 13, 2003 @07:10PM (#5297953)
    favors the tell-tale signature of biochemistry based on a dominant left-handed chirality

    Sounds very sinister. :)

  • Hey! How come... (Score:3, Funny)

    by GeneralEmergency ( 240687 ) on Thursday February 13, 2003 @07:17PM (#5298052) Journal

    ...all these carbonaceous chondrites look EXACTLY like chunks from the Piggly-Wiggly parking lot on Alderaan?

  • It's really quite obvious ... (Score:5, Funny)

    by Snork Asaurus ( 595692 ) on Thursday February 13, 2003 @07:33PM (#5298206) Journal
    If the meteorite had landed north of the equator, they'd have found mostly laevo-rotatory amino acids. Since, it landed down under, where everything turns in the opposite direction, they found mostly dextro-rotatory amino acids.

    Case closed and make mine a Foster's. G'day.

  • Ugh. News and Science don't Mix well (Score:5, Insightful)

    by EvilTwinSkippy ( 112490 ) <yoda AT etoyoc DOT com> on Thursday February 13, 2003 @07:44PM (#5298301) Homepage Journal
    The signal to noise ratio in this article was essentially zero.

    Fact: the meteorite contains ammino acids, and chirality that is not generally found in terrestrial organisms.

    Fact: This meteroite is HEAVILY polluted with terrestrial organic matter.

    Conclusion: While ammino acids are generated in space, they seem to mimic the compositions found when we try to synthesize them in the lab.

    Aside: You can produce the same results with some methane gas, water vapor, and ionizing radiation.

    Move along, no controvesy here.

    • read the article? (Score:3, Informative)

      by twitter ( 104583 )
      Assides from the non sequetor, which applies regardless, did you read the article? If you had read it and the intro above, you would have noticed that the amino-acids not found on earth also are mostly "left-handed" which is not how they form in a lab.
      • Well the correlation, while strong in their opinion, was not available from the article. The fact the you have some amino acides with the opposite chirality shows that it was obviously NOT produced by an organism. If it was manufactured by an organism that produced left-hand chirality acids, we would see all left-hand acids. It it were manufactured by an organism that produced right-handed acids, the proportion would be much higher (and not the same isotope) as was revealed in the story.

        I was waiting for the alien autopsy at the end of this article, or a discussion of the gunman in the grassy knoll.

    • Re:Ugh. News and Science don't Mix well (Score:4, Insightful)

      by joethebastard ( 262758 ) on Friday February 14, 2003 @03:46AM (#5300271)
      News and science mix much better if you read the article. Try this:

      Fact: the signal to noise ratio would be outside error limits or they wouldn't report it

      Fact: there are only two chiralities, and synthesizing them in the lab always makes both. biological syntheses always make just one kind.

      Fact: isotopic data was used to ensure that contamination didn't effect this chirality data

      Conclusion: Some other process that we didn't know about is going on

      Aside: if you're interested in this sort of thing, you should read the article.
      • So the fact that even with the constraints above you have both chilarlities more or less eliminates an organism as the source.

        Your point?

        And BTW, signal to noise ratio doesn't have anything to do with errors. It has to do with how much information there is in comparison to background noise. This article, IMHO was all noise.

  • evidence of extraterrestrial life? (Score:3, Interesting)

    by g4dget ( 579145 ) on Thursday February 13, 2003 @08:41PM (#5298686)
    So, we have meteorites that contain molecules and chiral mixtures that are indicative of life. On the other hand, those mixtures do not correspond to anything terrestrial life forms would be expected to produce.

    One logical conclusion seems to be that the meteorite contained extraterrestrial life, or perhaps a complex network of biochemical reactions that isn't quite life but a precursor. Those may have existed briefly in space and ceased long ago, or it may have been destroyed when the rock fell to earth, or we may simply not recognize it. I mean, if it doesn't have distinct membranes or other structural features, we wouldn't easily recognize life or close precursors of life at all with our current technology.



  • cool....

    LONG LIVE ROCK!

  • lucky they were pre-biotic proteins... (Score:4, Funny)

    by cyril3 ( 522783 ) on Friday February 14, 2003 @01:09AM (#5299835)
    otherwise they would be sitting in a detention centre right now appealing their refusal of refugee status by the Australian Gumment. Bloody alien queue jumpers will not be tolerated.

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