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Earth Space Science

Venus' Crust Heals Too Fast For Plate Tectonics 135

Posted by samzenpus
from the too-hot-to-crack dept.
An anonymous reader writes in with an interesting look at how important plate tectonics may be to life and why the crust on Venus works differently than it does on Earth. "Without plate tectonics, carbon would build up in the atmosphere. Venus, which does not have tectonics, shows the results: an atmosphere that is 96 percent carbon dioxide. It's toxic. Yet Venus is about the same size and composition as our planet, so why doesn't it have plate tectonics? Some researchers made a model to explore how Earth initiated plate movements, and these same researchers made one model of its neighbor for comparison. A 1.5-billion-year-old Earth and a similarly aged Venus were modeled as a hot, mushy material made of tiny particles of rock. The model uses physics at the one-millimeter rock grain scale to explain how the whole planet behaves. According to David Bercovici, a geophysicist at Yale who was an author on the paper, the model also shows how plate tectonics emerged on Earth but not on her twin."
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Venus' Crust Heals Too Fast For Plate Tectonics

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  • Rare Earth? (Score:5, Informative)

    by K. S. Kyosuke (729550) on Monday April 21, 2014 @10:51AM (#46806209)
    I believe I've read similar arguments some time ago in a book titled Rare Earth: Why Complex Life is Uncommon in the Universe [amazon.com]. It was published a decade ago. So it's a slow news day again, I guess. ;-)
  • Re:Why? (Score:5, Informative)

    by K. S. Kyosuke (729550) on Monday April 21, 2014 @11:03AM (#46806349)
    If you bothered to read the article (or the book I linked), you'd find out that plate tectonics is crucial in the long-term carbon cycle that snatches carbon-containing minerals and, passing through subduction zones, deposits them in the depths of the Earth. (I'm not a geologist but I also vaguely recall that the hydration of these minerals contributes to the increased levels volcanic activity near the subduction zones, by means of lowering the melting point of rocks - which is how the cycle gets closed, since this volcanic activity releases the carbon back.)
  • by BitZtream (692029) on Monday April 21, 2014 @11:21AM (#46806509)

    A basic biology class will tell you that CO2 is poisonous to a great many things ... like everything that breaths oxygen.

    http://en.wikipedia.org/wiki/H... [wikipedia.org]

    The rest of your post could be solved if you opened any 3rd or 4th grade science book ... not sure what planet you're thinking of, but its not venus, which has both an atmosphere and a solid surface.

    http://en.wikipedia.org/wiki/V... [wikipedia.org]

    It makes no sense because you have absolutely no idea what you're talking about.

  • by Anonymous Coward on Monday April 21, 2014 @01:16PM (#46807659)

    The atmosphere is 78% nitrogen, and we breath it just fine. But air of 5 - 10% carbon dioxide is far more than enough to kill you. This happens because carbon dioxide is toxic to humans and nitrogen is not. It has nothing to do with oxygen deprivation.

    As anyone who has taken college level biology will know, the hemoglobin found in red blood cells has two functions. The first is to transport oxygen from the lungs to the rest of the body, because oxygen is needed for cellular respiration (mainly the electron transport chain). The second function is to remove CO2 from the body cells and send them to the lungs. CO2 is the byproduct of cellular respiration, so if red blood cells did not transport it out, it would quickly accumulate in the body and make it too acidic to function (carbon dioxide plus water makes carbonic acid). This is why it is so critical for hemoglobin to be able to transport CO2 out of the body. The problem is that since hemoglobin can bind both CO2 and oxygen, high CO2 levels will begin to "crowd out" oxygen and hog up all of the hemoglobin, leading to suffocation. But even though the atmosphere is 78% nitrogen, this does not happen with nitrogen because nitrogen is not able to bind to hemoglobin at all. Evolutionarily, there is no reason for hemoglobin to have this ability.

    tl;dr It's not about lack of oxygen. CO2 is toxic, nitrogen is not even though there is much more of it.

  • by Anonymous Coward on Monday April 21, 2014 @02:54PM (#46808653)

    To add onto the other AC's helpful response, you can think about it as a sort of diffusion process. When blood reaches the lungs, it (and the hemoglobin within it) is rich in carbon dioxide while the lungs are rich in oxygen, so CO2 diffuses out of the blood and into lungs and oxygen flows from the lungs to the blood. When blood reaches body tissues, the body tissues have lots of CO2 and little oxygen compared to the blood, so the CO2 flows from the tissue to the blood and oxygen in the opposite direction. As the other AC already said, CO2 has a much higher binding affinity for hemoglobin than oxygen, which is why it can be a deadly poison even at low concentrations.

    Fun fact: breathing is actually more driven by the need to exhale CO2 than the need to inhale oxygen. This is part of the reason that swimmers continue to exhale while they are holding their breath underwater.

  • by dryeo (100693) on Monday April 21, 2014 @03:12PM (#46808859)

    Venus is still in the Goldilocks zone, which is why it was expected that Venus would be covered with steaming jungles and inhabitable until we actually measured the temperature and it was such a surprise that it was so hot. This would have been even more true early in the Solar Systems history when the Sun itself was 25% cooler.
    BTW, even the Earth would be an iceball at our distance from the Sun without the greenhouse effect which raises temperatures something like 40K

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