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Planetology: Plate tectonics may be essential for the development of life
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I keep thinking I've read something about this a while back, but can't recall where...
Makes a certain kind of sense. Sort of like the planet must be "alive" for anything else to survive.
Makes a certain kind of sense. Sort of like the planet must be "alive" for anything else to survive.
I think (speculating mind you) that it's the whole picture, not just moving plates. The planet needs a dynamo to create a magnetic field to protect the planet from radiation. A molten core results in a tectonic plated surface.
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No, it doesn't, not by itself. You also need a thin, brittle crust, which is what Earth has. And, for a significant magnetic field, a rapid enough planetary rotation to generate the dynamo effect generating the field. Venus almost certainly has a molten core, but no evidence of plate tectonics, probably due to its crustal zone being too thick. And Venus rotates far too slowly to generate a magnetic field. Mars rotates fast enough, but has a very weak magnetic field because its core appears to have cooled and solidified long ago. And it also has a thick crustal zone and no evidence of significant crustal plate development.
I am, by trade, a geologist, and teach geology at the local university in my spare time when I'm not entertaining my cats.
caw
I defer to your superior knowledge, but isn't Venus an exception in that the entire crust turned over a few hundred million years ago?
I'll have to get back to this, always happy to learn new things.
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Earth also has a much larger iron core than the other planets, apparently owing to a collision with another planet which resulted in the Earth having an extra helping of shared iron core and the Moon having a lot of the lightweight crustal elements of both planets which splashed off.
I don’t know how significant that is (and I am no geologist, for sure!), but it does seem to mean we have an unusually strong magnetic field for our size, so far as anyone knows.
I don’t know how significant that is (and I am no geologist, for sure!), but it does seem to mean we have an unusually strong magnetic field for our size, so far as anyone knows.
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I think that the effects of plate tectonics on life on earth are fairly speculative, if interesting. Certainly the long-term cycling of water and carbon through subduction and eruption have played a part in the Earth's life history. But I think we have little understanding of how other types of tectonics, such as existed on Mars and Venus for example, may have influenced elemental cycles. Plate tectonics is only one kind of tectonics, and one way that large scale cycling might occur on a planet. Since we have found plate tectonics only on Earth, it's easy to correlate the only planet with life with the only planet with plate tectonics and think that there might be a causative relationship (and maybe there is). But that thinking is based on a statistic of one data point which provides little constraints on how life and tectonics might work on other worlds.
OK, so I see the turnover of the crustal plates is also involved, recycling the carbon, not just the magnetic field. I sit corrected. 
This is from 2009: Astrobiology Magazine: PLATE TECTONICS COULD BE ESSENTIAL FOR LIFE
This is from 2009: Astrobiology Magazine: PLATE TECTONICS COULD BE ESSENTIAL FOR LIFE
That's especially interesting given the top layer of Gale Crater is devoid of the organic molecules they are finding further down.
It probably wasn't the Venusian crust that turned over, but instead an immense evulsion of magma from the Venusian mantle.
caw
Not sure I understand the difference. It's my understanding the surface cratering suggests the entire surface is the same age and not that old.
That's because it seems to have been entirely resurfaced by a planetary-wide evulsion of magma several hundred million years ago. That stuff would have come from deep within the Venusian mantle. Earth (thank Bokonon) has never experienced that kind of planetary event, but we have had a number of "smaller" magmatic events, notably the Siberian Traps eruption about 250 million years ago that wiped out 90-95% of the living biota on the planet. That stuff doesn't come from the crust, but from much deeper. It is what is happenng right now in Hawaii. The Kilauea eruption is drawing on sub-crustal magmatic material, stuff that is melted well below the brittle crustal zone.
You need to take my Physical Geology class. Meets Tuesday night, 6-10 PM, and Friday afternoons, 1:30-5:30 PM. There will be a mid-term exam next week. I can send you an electronic copy.
caw
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I know that. That was my point.
Sounds like fun. Not enough time in my life at the moment.