OSU: Ancient Earth Made Its Own Water — Geologically

[bystander]

Study Hints that Ancient Earth Made Its Own Water — Geologically
Ohio State University | AGU | 2014 Dec 17

[i]This plate tectonics diagram from the Byrd Polar and Climate Research Center shows how mantle circulation delivers new rock to the crust via mid-ocean ridges. New research suggests that mantle circulation also delivers water to the oceans.[/i]

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Evidence that rock circulating in the mantle feeds world’s oceans even today

A new study is helping to answer a longstanding question that has recently moved to the forefront of earth science: Did our planet make its own water through geologic processes, or did water come to us via icy comets from the far reaches of the solar system?

The answer is likely “both,” according to researchers at The Ohio State University— and the same amount of water that currently fills the Pacific Ocean could be buried deep inside the planet right now.

At the American Geophysical Union (AGU) meeting on Wednesday, Dec. 17, they report the discovery of a previously unknown geochemical pathway by which the Earth can sequester water in its interior for billions of years and still release small amounts to the surface via plate tectonics, feeding our oceans from within. ...

[Ann]

That is really very interesting.

I have found it slightly frustrating that, on the one hand, it has been generally accepted that comets (or perhaps meteorites) brought the Earth its water, and yet on the other hand, the chemical makeup of the Earth's water doesn't match the water of the comets that we have managed to analyze.

The idea that the Earth made its own surface water by releasing subsurface water and mixing it with water brought to our planet by comets and meteorites is quite satisfying.

Ann

[geckzilla]

I think it's entirely possible that the comet water theory has been overly accepted due to a lack of data and that other explanations are not nearly as intuitive. It's always been at least a little dubious so new ideas are quite welcome.

[Nitpicker]

The idea that Earth "made" its own water is not new. It is one of a number of mutually compatible ideas, none terribly well understood. I was under the impression that the consensus for the last few decades has been that the origin of the water on Earth is likely to be from a combination of terrestrial and extra-terrestrial sources.

What's new here is evidence of a particular kind of water cycle, previously unknown, between the mantle and the oceans.

...

But given that the Earth was formed from the soup that was the Sun's protoplanetary disc, following countless collisions and accumulations of material including water of one form or another, the line between terrestrial and extra-terrestrial origin is not entirely clear to me anyway.

[geckzilla]

Ok, new evidence for old idea, new idea, whatever. New thingy. I will endeavor to spread my nits into such a generalized mist that you cannot possibly pick at them in the future.

[Nitpicker]

My comment was not a nitpick of yours, geck. But I didn't think that anyone held the view that Earth's water came entirely and directly from collisions with comets, after the initial accretion of our fair planet.

[geckzilla]

No, I don't think so either. The gist I get is that comets contributed to some significant degree, though. Enough that when I played Sim Earth back in the day a good way to add water to your planet was to crash a comet into it. That was a really underrated game.

[Nitpicker]

I don't doubt that comets played some significant, perhaps even critically timed role in allowing our good, wet selves to evolve here. And in terms of an instant addition of a sizable quantity of water, a comet sounds like a great idea. Would you have enjoyed Sim Earth so much if it made you wait millions of years for geological processes to produce oceans?

[geckzilla]

Probably, since millions of years happened rather quickly. I'm sure there are numerous tweaks the game needs since it was first created. I was very confused by it when I was a kid but I still rented it quite a few times and when I look back at it I am surprised at the effort Maxis put into making it a hard science game.

[bystander]

http://asterisk.apod.com/viewtopic.php?p=236816#p236816