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Venus' Crust Heals Too Fast For Plate Tectonics
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."
I believe I've read similar arguments some time ago in a book titled Rare Earth: Why Complex Life is Uncommon in the Universe. It was published a decade ago. So it's a slow news day again, I guess. ;-)
Ezekiel 23:20
Amanita phalloides (Deathcap mushrooms) are NOT toxic.
Hundreds of thousands of rabbits would challenge the notion that it is toxic.
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.)
Ezekiel 23:20
Yes, but call me Robert.
Table-ized A.I.
Venus gets about twice the solar irradiation we do here. If we got 2.5kw or so per square meter here, this planet would be uninhabitable too.
And since the Great Oxygen Event had a biological cause, it's probable we'd have a CO2 atmosphere too, with or without plate tectonics, if we had Venus levels of solar irradiation.
"I do not agree with what you say, but I will defend to the death your right to say it"
There's a big difference between Earth and Venus.
Later doesn't have an over-sized moon.
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...
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...
It makes no sense because you have absolutely no idea what you're talking about.
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If instead of yelling about how Mr. Bercovici's theory doesn't explain life, the Universe and everything we accept that he has provided a reasonable theory explaining one of the factors which led to the current difference between Earth and Venus, the conversation here might be more productive.
Yes, Venus gets considerably more energy from the Sun than Earth does. Yes, this alone could reasonably be expected to make it very different from Earth. Is that the only thing which caused Venus to be different from the Earth? If not, it might be interesting to know what other factors resulted in the differences we see - hence, the article exploring how plate tectonics may have contributed to the differences we see.
Oh, one last observation - Mr Bercovici has postulated a theory. I'm sure he started with a hypothesis for which he then sought supporting evidence, which he has provided. So far, sounds like good science to me.
From TFA:
the Venus model, which was a couple hundred Kelvin hotter,
So, how does it get so much hotter than Earth? It is certainly that much hotter now but that is attributed almost entirely to the greenhouse effect. However, the article earlier states:
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.
So, because plates did not form, Venus experienced a runaway greenhouse effect and high temperatures. But high temperatures are supposed to prevent plates from forming. A little circular, no?
Don't get me wrong: this is interesting work but it doesn't really answer the question of how Venus became the way it is . To close the gap, you need to assume that:
a) Venus started out 200K hotter though some other means (Proximity to the Sun is not generally considered sufficient for that)
-or-
b) Venus plate tectonics stalled early on for some other reason, allowing the greenhouse effect to take over.
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.
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
https://en.wikipedia.org/wiki/Inverted_totalitarianism