Scientists have thought for a while now that
there may be water trapped within the earth’s
mantle.
Yeah, a secret ocean--underneath our oceans--inside
the earth!
This would change our common understanding
of what the earth looks like on the inside.
Now, there’s new evidence that provides
even more support for this idea, and has geoscientists
of all kinds wondering how Earth’s hidden
oceans could have formed.
And get this--the new evidence...it’s diamonds.
Back in 2014, scientists discovered diamonds
that contain water-bearing minerals.
These diamonds were brought up into human
range from deep within the earth’s transition
zone, around 400 miles below the earth’s
surface, so this was pretty remarkable.
How did water get trapped in something that
far down?
Well, when we’re talking about water here,
we’re not talking about the liquid water
we’re familiar with.
They’re actually the different elements
that make UP water--hydrogen and oxygen--bound
into the crystalline structure of a solid
mineral, which is where we get water-bearing
minerals.
See, the earth’s mantle moves by convection,
meaning hot magma rises and pushes other parts
of the mantle down further into the earth.
When these water-bearing minerals get pushed
down because of this convection activity,
the increased pressure literally wrings the
water out of them--this time, as water we
would probably recognize.
The initial conjecture that there might be
some water deep within the earth was confirmed
by the 2014 diamond discovery, and then backed
up with seismic data.
The seismic readings were consistent with
the idea that there was water in the mantle,
and it contributes to the mantle’s behavior.
More recently?
Even more diamonds!
These new jewels pulled from the earth’s
depths actually do contain water...but in
a TOTALLY new form that we’ve never observed
before.
These diamonds, from several locations across
southern Africa and China, contain tiny inclusions
of a form of water called ice-VII, an extremely
high pressure form of water that scientists
refer to as water-ice . This is the first
time we’ve ever actually observed this form
of water in nature.
The researchers say these new diamonds support
the presence of, at least what they’re calling,
‘aqueous pockets’ of water throughout
the mantle.
So not only is there water DEFINITELY inside
the earth, but also, it may be in a totally
novel form of water.
Who knew water came in different forms?!?
I feel like that leads us to two important
questions: 1.)
“So what?” and 2.)
“How did it get there?”
Well, one answer kind of addresses both.
The main theory for how we have water on earth
at all is that it got brought to us by rogue
asteroids containing water-bearing minerals
crashing into us from the far-reaches of our
solar system.
The theory goes that when the earth was forming,
our solar system was probably too hot for
any water molecules to survive and cling to
the space dust that would become the earth,
so water had to have been brought to us from
off-planet after the earth formed.
But these new diamonds could upend that.
Some scientists now estimate that the mantle
might contain more water than all the earth’s
oceans combined, which is way more water than
could have been pulled, via convection, from
the surface of the earth into the mantle in
the given time frame.
We may need to re-examine our theories about
the state of the solar system at the time
the earth was forming--maybe it was possible
for water to survive and cling to dust and
rock as it coalesced to form the earth.
Maybe there’s an entirely different theory
that we haven’t thought of yet!
We’re still unsure of the exact amount of
water in the mantle though, or what form it
might be in.
Scientists plan to keep exploring, though,
both with seismic measurements and lab experiments
that try to simulate the materials and pressures
that we would find inside the earth.
And, of course, keep looking for and examining
diamonds--not the kind you want to put in
a ring, but of course the kind that contain
hydrous minerals.
A girl’s true best friend.
Fun fact: the materials that primarily make
up the earth’s mantle are called Wadsleyite
and Ringwoodite, both water-bearing minerals
whose structure leaves them prone to gapping,
letting researchers think of them a bit like
a sponge that’s holding the mantle’s water.
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the massive asteroid currently headed for
earth.Thanks for watching!
