Hunting the Hidden Oceans

July 12, 2018 8:14 PM

Water-bearing minerals reveal that Earth’s mantle could hold more water than all its oceans. So . . . where it did come from? These fragments of crystalline carbon are every bit as precious — not for the diamond itself, but for what is locked inside: specks of minerals forged hundreds of kilometers underground, deep in Earth’s mantle. Not actual drops of water, or even molecules of H20, but its ingredients, atoms of hydrogen and oxygen embedded in the crystal structure of the mineral itself. This hydrous mineral isn’t wet. But when it melts, out spills water. And still the question remains, where did it come from?
posted by MovableBookLady (11 comments total)

“A couple years from now, we’ll find ice-VII

When they find Ice Nine it’s all over.
posted by nikaspark at 8:31 PM on July 12, 2018 [9 favorites]

It's turtles all the way down...
posted by cosmologinaut at 8:35 PM on July 12, 2018

It's like the song says:

"Under the rocks and stones, there is water underground"
posted by Strange Interlude at 9:48 PM on July 12, 2018 [20 favorites]

Oh, this was a nice article. I was labmates with Steve in grad school, so I heard the wadsleyite story back then, but it's good to hear so much more has been learned since then.
posted by Maxwell's demon at 11:32 PM on July 12, 2018 [6 favorites]

So Stephen Baxter’s Flood gains plausibility.
posted by los pantalones del muerte at 4:47 AM on July 13, 2018 [4 favorites]

Neat read, thank you for the link!
posted by mordax at 8:42 AM on July 13, 2018

Interesting! Bit of an anticlimax at then end, there, though:

Then, to identify the minerals, she blasts X-rays onto each bit and measures how the rays scatter off its crystal structure. Of the hundreds of diamonds in the lab, all from Brazil, she’s gone through about 60. No water yet.

posted by clawsoon at 9:24 AM on July 13, 2018

Clearly we need invade.
posted by lumpenprole at 11:21 AM on July 13, 2018

I'm confused as to why this contradicts hypotheses regarding why Earth has so much surface water. It's not like most of these minerals have inclusions of literal water or ice. There are inclusions of hydrogen which can combine with oxygen already in the rock when the rock melts, thus forming water.

That is to say that one could use these minerals as a sort of water "ore," but are not themselves water. That seems entirely consistent with the orthodox view of Earth's formation. A cloud with a bunch of hydrogen and oxygen, among other things, condenses into tiny bits that gradually agglomerate, some of which would be water, eventually aggregates into a really hot ball of stuff containing a bunch of oxygen and hydrogen that then recombines into water when the rock melts and weakly bound molecules start flying off due to the suddenly higher temperature/lower pressure.

Basically I feel like I'm being told that I should be surprised that a cloud of gas containing mostly hydrogen would not condense into minerals with hydrogen both in their molecular structure and with some inclusions of hydrogen in the defects. That isn't very surprising to me.
posted by wierdo at 4:29 PM on July 13, 2018

I think the (modern) orthodox explanation is that comets brought the water in from the Oort cloud region:
the nascent Earth started out dry, getting wet only after water-rich bodies from the distant solar system crashed into the planet...

Always had a problem with that yarn. Too many things have to go ... just right.

The region around the sun where the planet formed was too hot for volatile compounds like water to condense.

So I *think* they're suggesting that the O (At#8) -containing minerals *could* form in that region. ... where they could potentially grab onto lots of hydrogen ... become part of the Earth ... and release water on being heated.

Glad someone's working on alternatives to 'Oort gifts'. (Talk about hidden variables.)

(Then there's the related question: if the 'moon collided with the Earth', was that *before* the oceans formed?)
posted by Twang at 7:56 PM on July 13, 2018

My comment was a bit unclear, as I was trying to say that both could be true, hence saying the new finding
is not really challenging the orthodoxy. (And not terribly surprising) Surface ice on geologically inactive and otherwise dry bodies like the moon are pretty strong evidence that the comet/Oort cloud object/hydrated asteroid idea is at least part of the answer.

What would be surprising is finding that inclusions of H₂O are common in diamond and other rocks formed in the deeper parts of the mantle. Alas, that seems to be rare.
posted by wierdo at 3:29 AM on July 14, 2018