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Space Earth NASA Science

NASA Discovers Life's Building Block In Comet 148

Posted by timothy
from the low-glycemic-index dept.
xp65 writes "NASA scientists have discovered glycine, a fundamental building block of life, in samples of comet Wild 2 returned by NASA's Stardust spacecraft. 'Glycine is an amino acid used by living organisms to make proteins, and this is the first time an amino acid has been found in a comet,' said Jamie Elsila of NASA's Goddard Space Flight Center in Greenbelt, Md. 'Our discovery supports the theory that some of life's ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts.'"
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NASA Discovers Life's Building Block In Comet

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  • Panspermia (Score:2, Informative)

    by Icegryphon (715550) on Tuesday August 18, 2009 @10:20AM (#29105341)
    Adama: "Life here began out there." These are the first words of the Sacred Scrolls...
  • by Half-pint HAL (718102) on Tuesday August 18, 2009 @10:24AM (#29105405)

    That was lysine. Muppet.

    HAL.

  • Glycine is simple... (Score:5, Informative)

    by cfa22 (1594513) on Tuesday August 18, 2009 @10:44AM (#29105659)
    Glycine is the simplest amino acid, and it the only one that lacks a chiral center on the alpha carbon. Of the four groups attached in a tetrahedral arrangement to the alpha carbon, two are hydrogen atoms. In all other amino acids, one of the two hydrogens of glycines is replaced by a distinct functional group. The really interesting thing about biologically used amino acids is that it is always the same hydrogen of the two that is replaced -- all the 19 non-glycine amino acids are so-called "L-stereoisomers." Discovery of any one of the 19 amino acids other than glycine in a comet would be quite a story, and it would be even more surprising if there were a mixture of "L" and "D" stereoisomers other than 50/50. My bet is that if another amino acid is found in cometary debris, it is asparagine, since it can form by the reaction 2*glycine - water.
  • Re:Tin Foil Hat (Score:5, Informative)

    by c6gunner (950153) on Tuesday August 18, 2009 @11:48AM (#29106507)

    They might not be intelligent, but at least they'll be edible

    Actually, you're wrong there. As one example, life on earth is composed of right-handed sugars and and left-handed amino acids, but as far as we can tell there's no particular reason why that configuration had to happen - it was a random configuration which manifested early in the development of terrestrial life and spread to all existing species. This means we can only process food with that particular molecular makeup. Early artificial sweeteners took advantage of this fact - their manufacturers figured out how to make left-handed sugars which we could taste, but couldn't digest. In other words you can eat it and it won't cause you any harm, but you won't get any energy from it. What this means is that there would be, at best, only a 25% chance of us being able to use your hypothetical life-forms as a food source, and that's without having to worry about whether they provide us with the right vitamins/nutrients, what sorts of hormones and toxins might be in them, etc.

  • Re:hypotheses (Score:2, Informative)

    by Cattus Curiosus (970543) on Tuesday August 18, 2009 @01:16PM (#29107977)

    5) the gel got contaminated on earth. or the mass spec is not definitive about the molecule in question.

    I lean towards 5, and then 3 as a close second.

    I would have agreed with you before I RTFA. The authors acknowledged contamination as a confounding factor, and tested for it by isotopic analysis of the C13:C12 ratio, where glycine from space is expected to have a greater amount of C13. This is precisely what they found, allowing them to conclude that the glycine did, in fact, come from the comet.

  • Re:How sure? (Score:3, Informative)

    by psnyder (1326089) on Tuesday August 18, 2009 @02:47PM (#29109439)
    It's not the first time amino acids were found to be formed under extraterrestrial conditions. It's the first time amino acids were found on a comet. Many meteors have been found with amino acids, most notably the Murchison Meteorite [wikipedia.org] of 1969.

    _

    A question for anyone who has studied the subject: do we have any idea why there is a difference between terrestrial and extraterrestrial carbon isotope ratios?

    To answer your question from what I understand:

    • Atmospheric CO2 contains the naturally occurring carbon isotopes C12, C13, and C14 in the proportions 98.9%, 1.1% & 10 to the -10%, respectively.
    • Plants take in CO2 with both C12 and C13 isotopes, but about 7 million years ago, the predominant flora evolved so that they absorbed more CO2 with C13 than their predecessors. It was actually a stunningly quick change evolutionarily, about the span of a couple of million years. I don't remember why this benefited the plants, but it did, and that's what happened.

    So I believe a lot of terrestrial C13 is trapped because our plants have preferred it for 7 million years.


    Incidentally, this is how we know that the increased CO2 in the atmosphere is caused by fossil fuel burning. The plants that created fossil fuels are much older than this 7 million year mark and trapped a higher ratio of C12. There's an increase of C12 isotope in the atmospheric ratio that starts around 1850 (the beginning of the industrial revolution). In other words, the trapped C12 isotopes are escaping in higher ratios when we burn those old plants. And we can figure out the timing of all of this because of Carbon dating using C14. Gotta love those isotopes!


    _

    Or for that matter, the higher presence of iridium in space rocks, etc?

    Found this one on Wikipedia =) [wikipedia.org]

    It is thought that the overall concentration of iridium on Earth is much higher than what is observed in crustal rocks, but because of the density and siderophilic ("iron-loving") character of iridium, it descended below the crust and into the Earth's core when the planet was still molten.

  • No direct proof (Score:3, Informative)

    by glitch23 (557124) on Tuesday August 18, 2009 @05:55PM (#29111997)

    'Our discovery supports the theory that some of life's ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts.'"

    Again guys, you are filling in gaps with information that fits your ideal world and to support other theories but there is no direct evidence that events happened this way. There is no direct evidence that glycine can survive the impact or that it actually was transferred from space-borne objects. Example: A 30 year old brown-haired person lives in San Francisco and another one who is 50 years old lives in New York. Does that mean the one in San Francisco is the offspring (and therefore related) of the one in New York either because the person in New York traveled to San Francisco then had a child or had a child then the child moved to and grew up in San Francisco? Yeah it can mean that but without asking the people involved or seeing it happen first-hand you can't just fill in the blanks and assume you are correct. We obviously can't ask glycine where it came from so we have to see it first-hand be transferred from a comet/meteorite to Earth and remain intact and viable before we can really say for sure that supports the theory that life's ingredients came from out of this world. Something generic like 2 samples of glycine or 2 brown-haired people are too generic to conclude they are related, but feel free to make that gross assumption anyway to fit theories of evolution.

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