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Fraser
2018-Aug-05, 09:50 PM
When looking for potentially-habitable extra-solar planets, scientists are somewhat restricted by the fact that we know of only one planet where life exists (i.e. Earth). For this reason, scientists look for planets that are terrestrial (i.e. rocky), orbit within their star’s habitable zones, and show signs of biosignatures such as atmospheric carbon dioxide – which […]
The post It Looks Like Plate Tectonics Aren’t Required to Support Life (https://www.universetoday.com/139738/it-looks-like-plate-tectonics-arent-required-to-support-life/) appeared first on Universe Today (https://www.universetoday.com).


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BigDon
2018-Aug-13, 10:21 PM
Umm, except for the fact that every 50 to 100 million years the planet will undergo complete planetary resurfacing as the internal heat builds up, there's nothing wrong with this idea, I guess.

geonuc
2018-Aug-14, 01:08 PM
Umm, except for the fact that every 50 to 100 million years the planet will undergo complete planetary resurfacing as the internal heat builds up, there's nothing wrong with this idea, I guess.

As I'm almost certain you know, only oceanic crust gets recycled. Continental crust does not, except for minor bits that get caught in the subduction process. So, not exactly a complete planetary resurfacing.

BigDon
2018-Aug-14, 01:42 PM
Morning Geo.

The subject was exoplanets without plate tectonics. Without plate tectonics to relieve the pressure, the above happens.

The matter is easy to Google up.

geonuc
2018-Aug-14, 02:26 PM
My bad. I read your 'the planet' as referring to Earth.

Eclogite
2018-Aug-14, 04:22 PM
While I agree with BigDon's assertion that planetary resurfacing will occur periodically, the time frame proposed (50-100million years) is questionable. The resurfacing of Venus is estimated to have occurred 500 - 1000 million years ago: an order of magnitude greater. I would suspect that the actual time would be contingent upon such factors as heat of accretion, heat released by core catastrophe, amount and type of radioactive elements, mantle and crustal thickness, atmospheric character and insolation.

BigDon
2018-Aug-14, 08:12 PM
I looked it up before I posted Eclo, I think my numbers are good.

Let's agree to disagree. :)

grapes
2018-Aug-14, 11:14 PM
While I agree with BigDon's assertion that planetary resurfacing will occur periodically, the time frame proposed (50-100million years) is questionable. The resurfacing of Venus is estimated to have occurred 500 - 1000 million years ago: an order of magnitude greater. I would suspect that the actual time would be contingent upon such factors as heat of accretion, heat released by core catastrophe, amount and type of radioactive elements, mantle and crustal thickness, atmospheric character and insolation.
And, plain old volcanism. As the article in the OP mentions:


You still have volcanism on stagnant lid planets, but it’s much shorter lived than on planets with plate tectonics because there isn’t as much cycling.


I looked it up before I posted Eclo, I think my numbers are good.

Let's agree to disagree. :)
Eclogite's counterexample, Venus, doesn't really work, because what we're talking about is stagnant lid planets (like Venus) that haven't resurfaced in a long time (like Venus) and can support life (definitely not Venus).

Do you still have a link to that info?

ETA: https://www.sciencedirect.com/science/article/pii/S0031920116301509

BigDon
2018-Aug-15, 03:06 PM
Well, I looked for an hour an a half this morning for the article I hit first and couldn't do it.

Found a dozen that provided confirmation of Eclogite's time scales with the closest to agreeing with my time scales in the 300 to 600 million year time frame.

Looks like I was unduly influenced by a minority view in two articles. One I read years ago and a second one the other day that was the first hit when I Googled it before posting. Had pictures and everything!

Honest, I wasn't trolling the authors, I did see those time scales *somewhere* but obviously they were wrong.

Eclogite
2018-Aug-15, 06:04 PM
Eclogite's counterexample, Venus, doesn't really work, because what we're talking about is stagnant lid planets (like Venus) that haven't resurfaced in a long time (like Venus) and can support life (definitely not Venus).
I may be misreading you, but I think it works perfectly as an example. The researchers ran many variations of stagnant lid planets, varying the sort of parameters I suggested might have an influence in my earlier post. Many of these produced planetary environments that would be compatible with life, but some did not. Venus fits perfectly in that latter subset.