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posted by Fnord666 on Thursday May 21 2020, @03:46PM   Printer-friendly
from the gotta-hand-it-to-them dept.

Cosmic Rays May Have Left Indelible Imprint On Early Life, Stanford Physicist Says:

Chirality, also known as handedness, is the existence of mirror-image versions of molecules. Like the left and right hand, two chiral forms of a single molecule reflect each other in shape but don't line up if stacked. In every major biomolecule – amino acids, DNA, RNA – life only uses one form of molecular handedness. If the mirror version of a molecule is substituted for the regular version within a biological system, the system will often malfunction or stop functioning entirely. In the case of DNA, a single wrong handed sugar would disrupt the stable helical structure of the molecule.

Louis Pasteur first discovered this biological homochirality in 1848. Since then, scientists have debated whether the handedness of life was driven by random chance or some unknown deterministic influence. Pasteur hypothesized that, if life is asymmetric, then it may be due to an asymmetry in the fundamental interactions of physics that exist throughout the cosmos.

"We propose that the biological handedness we witness now on Earth is due to evolution amidst magnetically polarized radiation, where a tiny difference in the mutation rate may have promoted the evolution of DNA-based life, rather than its mirror image," said Noémie Globus lead author of the paper and a former Koret Fellow at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC).

In their paper, published on May 20 in Astrophysical Journal Letters, the researchers detail their argument in favor of cosmic rays as the origin of homochirality.

Cosmic rays are an abundant form of high-energy radiation that originates from various sources throughout the universe, including stars and distant galaxies. After hitting the Earth's atmosphere, cosmic rays eventually degrade into fundamental particles. At ground level, most of the cosmic rays exist only as particles known as muons.

Muons are unstable particles, existing for a mere 2 millionths of a second, but because they travel near the speed of light, they have been detected more than 700 meters below Earth's surface. They are also magnetically polarized, meaning, on average, muons all share the same magnetic orientation. When muons finally decay, they produce electrons with the same magnetic polarization. The researchers believe that the muon's penetrative ability allows it and its daughter electrons to potentially affect chiral molecules on Earth and everywhere else in the universe.

[...] The researchers' hypothesis is that, at the beginning of life on Earth, this constant and consistent radiation affected the evolution of the two mirror life-forms in different ways, helping one ultimately prevail over the other. These tiny differences in mutation rate would have been most significant when life was beginning and the molecules involved were very simple and more fragile. Under these circumstances, the small but persistent chiral influence from cosmic rays could have, over billions of generations of evolution, produced the single biological handedness we see today.

Globus and Blandford suggest experiments that could help prove or disprove their cosmic ray hypothesis. For example, they would like to test how bacteria respond to radiation with different magnetic polarization.

Journal Reference:
Noemie Globus, Roger D. Blandford. The Chiral Puzzle of Life. The Astrophysical Journal, 2020; 895 (1): L11 DOI: 10.3847/2041-8213/ab8dc6


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  • (Score: 2) by Runaway1956 on Thursday May 21 2020, @04:04PM (1 child)

    by Runaway1956 (2926) Subscriber Badge on Thursday May 21 2020, @04:04PM (#997424) Journal

    All the other indelible cosmic rays proved to be poor imposters.

    • (Score: 0) by Anonymous Coward on Friday May 22 2020, @02:03PM

      by Anonymous Coward on Friday May 22 2020, @02:03PM (#997838)

      Bbut... Sharpie Stanford is the best brand.

  • (Score: 2) by FatPhil on Thursday May 21 2020, @06:20PM

    by FatPhil (863) <pc-soylentNO@SPAMasdf.fi> on Thursday May 21 2020, @06:20PM (#997482) Homepage
    > They are also magnetically polarized, meaning, on average, muons all share the same magnetic orientation.

    Are they polarised a different way in the earth's two hemispheres then? If so, then left chirality would have been dominant near the other pole, and the tropics would have no bias at all. Which would mean that chirality didn't bias earth's life just one way.
    If not, then what external thing causes the "sharing" of this magnetic orientation? How do the particles communicate with each other to have this bias, and what decided what bias it should have in the first place? You've just moved the question of the source of bias to another location.

    Before testing this hypothesis, first I'd like an explanation for the existence of the physical effect you're claiming is causing the physical effect, before testing whether that physics would have the biological effect.
    --
    Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
  • (Score: 4, Interesting) by HiThere on Thursday May 21 2020, @06:58PM (2 children)

    by HiThere (866) Subscriber Badge on Thursday May 21 2020, @06:58PM (#997507) Journal

    This is an unnecessary hypothesis. If one form evolves first then that form will dominate.

    This kind of hypothesis will only become necessary if we encounter several independently evolved life forms (i.e. no common ancestry) and they all have the same chirality. Then we need to consider why. Until then random chance suffices quite well.

    P.S.: It's not clear that Martian life would have evolved independently. This will probably need to wait until multiple stars with locally evolved life have been visited.

    --
    Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
    • (Score: 2) by deimtee on Friday May 22 2020, @05:22AM

      by deimtee (3272) on Friday May 22 2020, @05:22AM (#997734) Journal

      Interstellar panspermia, while difficult, is still possible. I think you would need to wait until you find multiple independent biosystems. Even given amino acids as the most likely biochemistry, there is no particular reason to choose the small subset that Earth life uses. If other planets use a substantially different set but still with the same chirality, then Lucy might have some 'splaining to do.

      --
      If you cough while drinking cheap red wine it really cleans out your sinuses.
    • (Score: 0) by Anonymous Coward on Friday May 22 2020, @09:11PM

      by Anonymous Coward on Friday May 22 2020, @09:11PM (#997976)

      i assume that they are not compatible ...
      so, maybe, both handedness "came into being" but there was "some sort of competition"? assuming there weren't too many(?) in the soup, once one handedness got the ..errr... upper hand that's that. i assume they both would compete for the same resources.

      anyways, what is more interesting and maybe the moment that DNA "invented the wheel" moment, is why isn't new primordial life "generated" on a daily basis ... but fails?
      is there a "mechanism" that turns chemical molecules (left OR right handed) into life?

      the narrative, i guess, is that today we're living in a very civilized environment and turning "dead molecules" into "living ones" requires a environment on earth that we "evolved" beings could not survived, if teleported back? how quaint ^_^

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