Molecules From Space May Have Affected Life On Earth

Article written: 17 Mar , 2009
Updated: 24 Dec , 2015
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A decade ago researchers analyzed amino acids from space, brought to Earth in meteorite which landed in Australia, finding a prevalence of “left-handed” amino acids over their “right-handed” form. Now, a new study of dust from meteorites supports this finding, and offers new clues to a long-standing mystery about how life works on its most basic, molecular level. “We found more support for the idea that biological molecules, like amino acids, created in space and brought to Earth by meteorite impacts help explain why life is left-handed,” said Dr. Daniel Glavin of NASA’s Goddard Space Flight Center in Greenbelt, Md. “By that I mean why all known life uses only left-handed versions of amino acids to build proteins.”

20 different amino acids arrange themselves in a variety of ways to build millions of different proteins. Amino acid molecules can be built in two ways that are mirror images of each other, like your hands. Although life based on right-handed amino acids would presumably work fine, “you can’t mix them,” says Dr. Jason Dworkin of NASA Goddard, co-author of the study. “If you do, life turns to something resembling scrambled eggs — it’s a mess. Since life doesn’t work with a mixture of left-handed and right-handed amino acids, the mystery is: how did life decide — what made life choose left-handed amino acids over right-handed ones?”

Over the last four years, a team lead by Glavin, carefully analyzed samples of meteorites with an abundance of carbon, called carbonaceous chondrites. The researchers looked for the amino acid isovaline and discovered that three types of carbonaceous meteorites had more of the left-handed version than the right-handed variety – as much as a record 18 percent more in the often-studied Murchison meteorite. “Finding more left-handed isovaline in a variety of meteorites supports the theory that amino acids brought to the early Earth by asteroids and comets contributed to the origin of only left-handed based protein life on Earth,” said Glavin.
The building blocks of proteins are molecules called amino acids. Most types of amino acids can exist in two different forms, one that is 'left-handed' and the other as 'right-handed.' Credit: NASA
All amino acids can switch from left-handed to right, or the reverse, by chemical reactions energized with radiation or temperature, according to the team. The scientists looked for isovaline because it has the ability to preserve its handedness for billions of years, and it is extremely rarely used by life, so its presence in meteorites is unlikely to be from contamination by terrestrial life. “The meteorites we studied are from before Earth formed, over 4.5 billion years ago,” said Glavin. “We believe the same process that created extra left-handed isovaline would have created more left-handed versions of the other amino acids found in these meteorites, but the bias toward left-handed versions has been mostly erased after all this time.”

The team’s discovery validates and extends the research first reported a decade ago by Drs. John Cronin and Sandra Pizzarello of Arizona State University, who were first to discover excess isovaline in the Murchison meteorite, believed to be a piece of an asteroid. “We used a different technique to find the excess, and discovered it for the first time in the Orgueil meteorite, which belongs to another meteorite group believed to be from an extinct comet,” said Glavin.

The team also found a pattern to the excess. Different types of meteorites had different amounts of water, as determined by the clays and water-bearing minerals found in the meteorites. The team discovered meteorites with more water also had greater amounts of left-handed isovaline. “This gives us a hint that the creation of extra left-handed amino acids had something to do with alteration by water,” said Dworkin. “Since there are many ways to make extra left-handed amino acids, this discovery considerably narrows down the search.”

If the bias toward left-handedness originated in space, it makes the search for extraterrestrial life in our solar system more difficult, while also making its origin a bit more likely, according to the team. “If we find life anywhere else in our solar system, it will probably be microscopic, since microbes can survive in extreme environments,” said Dworkin. “One of the biggest problems in determining if microscopic life is truly extra-terrestrial is making sure the sample wasn’t contaminated by microbes brought from Earth. If we find the life is based on right-handed amino acids, then we know for sure it isn’t from Earth. However, if the bias toward left-handed amino acids began in space, it likely extends across the solar system, so any life we may find on Mars, for example, will also be left-handed. On the other hand, if there is a mechanism to choose handedness before life emerges, it is one less problem prebiotic chemistry has to solve before making life. If it was solved for Earth, it probably has been solved for the other places in our solar system where the recipe for life might exist, such as beneath the surface of Mars, or in potential oceans under the icy crust of Europa and Enceladus, or on Titan.”

The team’s paper appears in the March 16 Proceedings of the National Academy of Sciences.

Source: Astrobiology Magazine


25 Responses

  1. Aqua says

    Chirality, right? Anti-polar production of opposingly spun up matter, a result of a plasmatic vortex alignment?

  2. Trippy says

    Aqua Says:
    Chirality, right?

    Correct

    Aqua Says:
    Anti-polar production of opposingly spun up matter, a result of a plasmatic vortex alignment?

    This seems to me to be as word-soup.
    But it seems to me to beg two questions:
    1. Why would a plasma vortex prefer one order based on Atomic Number over another?
    2. Why would a plasma vortex preferentially rotate in one direction over another?

  3. Member
    Stuart says

    Surely in the headline you mean “Affected” not “Effected” ? Otherwise, nice article

  4. Stuart- I cringed when I came back and saw the typo in the headline, hoping no one had noticed yet….

  5. Austin says

    “Effected” could work if you mean that life on earth was brought about by molecules from space.

    http://www.thefreedictionary.com/effected

    tr.v. ef·fect·ed, ef·fect·ing, ef·fects
    1. To bring into existence.
    2. To produce as a result.
    3. To bring about. See Usage Note at affect1.

    Usage Note: Affect and effect have no senses in common. As a verb affect is most commonly used in the sense of “to influence” (how smoking affects health). Effect means “to bring about or execute”: layoffs designed to effect savings. Thus the sentence, “These measures may affect savings” could imply that the measures may reduce savings that have already been realized, whereas, “These measures may effect savings” implies that the measures will cause new savings to come about.

  6. TD says

    How about this for a recipe for life. 1) Start with planet. 2) drop on some bacteria. Done. Any life we find on Mars will most likely be gentically and amino acid-ly similar to earth life….since both planets most likely were seeded by the same source. (and please get on with it…..could the search for life on Mars possibly proceed any slower?…for years we played “follow the water”….well, guess what….Phoenix splashed in some when it landed. Please get on with it, or quit and make room for some scientists who prefer to search for answers than make excuses.

  7. Frank Glover says

    The late Isaac Asimov (whose primary education was in biochemestry, it should eb remembered) once wrote a series of essays (among many others) titled ‘The Left Hand of the Electron’ throuought, he builds up an argument for biological left-handedness due to the physics of the way matter interacts with ultraviolet radiation, with a preference related to the negative charge of the electron.

    Which means that in an all-antimatter universe where electrons would have a positive charge (we also know them as positrons), we would also see a preference for right-handed amino acids…

    (Forgive me for greatly oversymplifying this argument, it’s also been a very long time since I’ve read it.)

  8. MeMyselfAndI says

    There is no such thing as a positron. There are electrons, and particles without electrons.

  9. Nexus says

    No, there is such a thing as a positron. It’s a particle with the same properties as an electron except that its electric charge is positive instead of negative. They have been known for decades and are routinely produced in particle accelerator experiments, as well as some forms of radioactive decay. Their existence is not in dispute.

  10. br says

    “There is no such thing as a positron. There are electrons, and particles without electrons”

    there is such a thing. It exists in anti-matter.

    http://en.wikipedia.org/wiki/Positron

  11. procyan says

    Just wondering, has there been a similar study of sugars? Do D forms dominate?

  12. Astrofiend says

    “# MeMyselfAndI Says:
    March 17th, 2009 at 2:56 pm

    “There is no such thing as a positron. There are electrons, and particles without electrons.”

    Ah – positrons do exist – they are identical to the electron but with electric charge +e, not -e. Their existence cannot possibly be in dispute – they are THE fundamental particle of interest in such real world applications as Positron Emission Tomography (PET) scans, etc.

    I’d brush up on the Standard Model of Particle Physics a bit mate. There are many many many particles in existence, defined by their properties such as spin, isospin, charge, mass, colour charge, etc. etc. The measurements performed on these particles and of their properties are extremely precise – they are as real as anything can be said to be real.

  13. Calib says

    astro, br, nexus…I think you guys just got trolled….

  14. ND says

    Calib,

    Troll? what’s that?

    🙂

  15. Calib says

    What is a Troll?

    Heres a definition from the Wikipedia page on internet trolls..
    “An Internet troll, or simply troll in Internet slang, is someone who posts controversial, inflammatory, irrelevant or off-topic messages in an online community, such as an online discussion forum or chat room, with the primary intent of provoking other users into an emotional response[1] or to generally disrupt normal on-topic discussion.[2]”

  16. Calib says

    Im sure most people who frequent this unmoderated forum will have a certain slimy oily person in mind.

    “There is no such thing as a positron. There are electrons, and particles without electrons”

    Sound familiar?

  17. ND says

    Calib,

    I think I unintentionally trolled you. I was just being silly. I know what a troll is. It’s just that Oils has been running a blog for over a year with his trolling. He struck me as someone who actually believes in what he’s saying.

    Anyway, you’re right. I’m done with Oils. I think he should be left alone with his ignorance of his ignorance.

  18. Ooops, got caught again!
    Yes.
    There is no such thing as a positron. There are electrons, and particles without electrons.

  19. Trippy says

    No such thing as Positrons? Then I guess all those people who have had PET scans are religous fundamentalists huh?

  20. neoguru says

    You cannot get more fundamental then the chirality of organic precursors to life. The fact that left-handed amino acids seem to predominate in space tends to support the idea that life may have originated there. One thought is that life evolved from a single molecule – it’s about the only way a single chirality could come about – one of the great, unsolved scientific mysteries we still face. I put it right up there with dark energy and dark matter.

  21. kate sisco says

    Well, at least I found out why my posts weren’t welcome. I have just a BS in Geology and am interested in outlandish theories but had no idea that posting them would create ‘a provocative reaction.’ I certainly never meant to do so. And I have seen lots of stuff that was meant to do so. And never helped it along with a reply.

    I think the problem stems from my not working in my degreed field and therefore not constrained to be circumspect in my ideas. Although I have seen valid non main line theories by far superior minds than mine.

    Just for the record, I do not troll. Isn’t a curious mind supposed to be desired?

  22. Feenixx says

    procyan asks:
    “Just wondering, has there been a similar study of sugars? Do D forms dominate?”

    It’s true for ALL substances which come in D and L forms: if they are produced by a living organism, ONLY the D variety is generated. Synthetic substances contain both, D and L varieties.

  23. ND says

    kate sisco,

    Were you posting under the handle “kate sisco”?

    Oils,

    If you’re posting under the handle “MeMyselfAndI “, are you also involved with holoscience.com? “MeMyselfAndI ” is mentioned at the bottom of the page on holoscience as a designer of the site.

  24. Frank Glover says

    “There is no such thing as a positron. There are electrons, and particles without electrons.”

    I’m sure that anyone who designs and builds PET Scanners (Positron Emission Tomography) would be fascinated to hear that…

    Electron-positron (so named before we began to think of anti-matter generically, and didn’t simply call it the anti-electron as we might today) interaction is probably the simplest case of matter-antimatter annihilation, usually producing two gamma-ray photons, each with an energy of 511keV.

    If you think you’ve got some new radical physical theory, it had better explain what we already observe to be true (any new theory must do so, as well as predicting something new that can be looked for, and/or explain observations that the old theory can’t).

    Talk is still highly inexpensive…

  25. Russ says

    Left handed alien life would be nice for space colonies, that want to eat the local vegetation. (If the amino acids of other planets are right handed, we would get any sustenance for making our own proteins from eating them).

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