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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
you are mistaken, the composition of Venus rock from surface on down is nearly identical to Earth.
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.
At sufficiently low doses, nothing is toxic. At sufficiently high doses, everything is toxic.
Did you know you can (and people do every year) die from water toxicity?
I want to see a model of a Venus carbon scrub. 96% CO2? Earth is 20% O2, 0.035% CO2. Venus has 3.5% nitrogen. If we brought the CO2 down to Earth levels, the atmosphere would be 1% CO2, 99% nitrogen. Obviously, instead, you'd have a ton of oxygen--but if you could find hydrogen, you could make vast amounts of O2.
I went to research this and ... someone has already worked it out. Bombarding Venus with hydrogen would produce a 3 bar atmosphere, 80% coverage with water, 10% of the water on the earth's surface but Venus is flat. Habitable. Probably not for humans, but we could continuously dump life there and it would eventually adapt. Building an ecosphere would be hard; it would be easier to seed with microbial life and wait a billion years. Rapid terraformation is hard; we could use a temporal bubble to do it, otherwise not so great.
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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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ob. The Far Side reference
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
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 model uses physics at the one-millimeter rock grain scale to explain how the whole planet behaves."
A 3,000 x 3,000 x 3,000 grid is considered very large for modern scientific models. Assuming they are working on a cartesian grid, and an earth diameter of 12,000 km, their model would be 12,000,000 x 12,000,000 x 12,000,000; twelve orders of magnitude larger than the biggest physical model I've ever heard of.
This cannot be the case.
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.
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.
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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There's a big difference between Earth and Venus.
Later doesn't have an over-sized moon.
That adds a lot of stress. Then pile on 1.3 billion cubic kilometres of water that tends to try to follow the moon around...
1,400,000,000,000,000,000 metric tons sloshing around would put cracks in pretty much anything.
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Is it surprising that there is a difference in the behavioral history of a single planet and a similar planet that happens to be part of a binary planet system?
Hint: Venus does not have tides; has never had tides. Earth tides were a lot larger when Earth was young and the Moon was closer. They are still large enough to put a significant do-si-do waggle in the Earth's orbit about the Sun. Despite what dumb-ass astronomer conventions might say, when a satellite is so large that it deflects its primary from its orbit by 4,000 miles, you have a binary planet.
Why do so many Earth "scientists" fail to see that you cannot talk sensibly about Earth's mechanics without acknowledging the Moon's influence? Of course there is going to be a difference between the pot that sits on the stove undisturbed, and the one that is constantly stirred.
</rant>
Will
No, you have not missed anything. You are parroting the "logic" of the Committee for Small Body Nomenclature of the International Astronomical Union. This is a true committee of fifteen members whose job it has been to decide on definitions of words. There was and is no science here. Nor was there any logic based on science; the logic was that of taxonomy: making pigeonholes to classify stuff. Nor was logic used in making the final determinations; what the pigeonholes were to be called was decided by vote. It was a "let's make new words" party, having nothing to do with astronomy, geology, or selenology. (See? It is both easy and fun to add words to the pseudoscientific jargon. Even scientists can do it!)
The Moon is considered a moon as the barycentre is within the Earth.
The barycenter of the Earth-Moon binary system (and that is a legitimate phrase) is always 1,000 miles below the lithosphere of the Earth, and 3,000 miles above the Earth's core. Quito, Equador, is a city on the equator. When there is a lunar eclipse on either the Spring or Autumn equinox at Quito, an interplanetary voyager arriving from Mars would find that Quito was 1,500 miles closer to the Sun than usual, but 12 hours earlier or later it was almost 1,500 miles further from the Sun than the navigator's first order approximation*. The communications officer of that interplanerary ship had better take into account the way the Earth spins about the barycenter of the binary system if he is to stay in laser beam contact with the Quito space port.
More significantly over the Earth's history is that its rotation around the barycenter raises tides. Not just the noticeable ones in the hydrophere, but large ones in the various layers of the atmosphere, and smaller, but significant, ones in the lithosphere. Geology has yet to develop an effective model on how the tidal strains on the lithosphere affect plate tectonics. But there can be little question that significant tidal forces are at work, alternately stretching and compressing faults.
In retrospect, what this august body of astronomers should probably have done is given their naming problem over to the experts who have recognized degrees in the appropriate field of study: these kinds of taxonomic decisions are better left to the linguists and other language experts. There are probably very few astronomers who have done any study of language arts at all. No wonder they bungled the thing so badly. They probably did not even know they were not doing astronomy any more. *
I would not mind having someone check my geometry here. I think the difference is actually 3,000 miles (displacement of the Earth's center from the barycenter) but I'm going with the more conservative number.
Will