Where Did Water Come From?

4.5 billion years ago earth was off to a

rocky start we just collided with

another early planet the size of mars a

cataclysmic event that melted both

planets and spun off a sizable chunk of

lava that cooled into our moon this

impact set the stage for the haitian eon

named of course for hades the greek god

of the underworld it was a name that

matched earth's generally hellish vibes

at that point since our planet was so

hot that our atmosphere actually

contained vaporized gaseous rock we're

talking temperatures around 2 000

degrees celsius but as the earth and the

moon began to cool something new formed

on earth's surface liquid water which

seems standard after all 71 of the earth

is covered in our estimated 366

trillion gallons of water except we

shouldn't have that water we formed too

close to the sun mercury venus and mars

are all super low on water so where did

ours come from and why do we have so

much of it well it's complicated and

still debated but we think our water

came from a few unlikely sources

space dust and even the sun

water itself isn't actually that

uncommon in our solar system it's just

further out for example jupiter's moon

europa is a quarter of the earth's size

but has twice as much water as we do and

that has to do with the fact that europa

formed farther away from the sun because

in the beginning of our solar system we

were all star stuff our solar system is

formed from a nebula the dusty remains

of an exploded star as that star dust

collided and collapsed it formed our sun

and the gravity of that young sun made

all the rest of the dust spin around it

in a flat plate like cloud called a

protoplanetary disk but our early sun

was hot and soon that disk of dust began

to differentiate solar and magnetic

winds blasted light gases away from the

sun leaving mostly heavier elements like

iron and silica behind which is why

earth is a rocky planet that's what was

in our section of the disk lots of iron

and lots of silica we also had some of

the ingredients for water but not all

water is made of hydrogen and oxygen and

oxygen is pretty heavy so we have a lot

of it in fact though it only makes up

about 21 of our atmosphere oxygen binds

so readily to silica and iron that it's

the most common element on our planet

but oxygen is only part of what you need

for water and hydrogen is really light

so it got blown out towards jupiter

saturn and other planets which now have

a lot of water ice so if it didn't form

here to start with where did we get that

missing ingredient where did our

hydrogen come from and when did it get

here the easy answer is we got pelted

with it water ice and hydrogen hang out

in the outer solar system but sometimes

they come inwards in the form of space

pebbles aka asteroids and meteorites and

there is a specific type of meteorite

called a chondrite that is full of water

but i don't mean full of water like a

gusher you can't crack open a meteorite

like a coconut and sip star water from

it as much as i would like to as much as

we would like to do instead the solo

hydrogen and the complete h2o water

molecules have become part of the

chemical structure of the minerals that

make up chondrites these include

minerals like serpentine chlorite and

smektite which hold on to their water

tight this is actually how most of

earth's water is stored today while we

have a bunch of liquid water we estimate

that earth's rocks hold maybe 18 times

the amount of water that our oceans have

so how do you get that water out of

these minerals well the easiest way is

to melt it which isn't always going to

happen just by flinging those

water-bearing minerals at the earth

after all we have solid chondrite

meteorites that hit our planet and

didn't melt but that's because they hit

today if they'd hit earth in the haitian

that would have been a much different

story back in the beginning of the

haitian anything that hit the surface

would have just melted straight into our

magma oceans there hydrogen met oxygen

and the resulting water superheated into

gas lighter than magma the water vapor

would bubble up and out into our

atmosphere but this process was a race

against the clock because our magma

surface was cooling and once a solid lid

of rock formed no more water could

escape the oldest traces of rocks we

found date to about 4.4 billion years

old so that's probably when the lid of

solid rock formed but those rocks have

signs of something surprising they were

exposed to a liquid ocean yep as soon as

the earth cooled enough to put a cap on

the magma we had an ocean that said it

was probably a little different than the

oceans we see today earth's atmosphere

in the early hayden was full of carbon

dioxide and was very thick potentially

as thick as

215 bars of pressure which is 215 times

what it is now with all that pressure

and heat earth's surface was

weird today water turns to gas when it

reaches 100 degrees celsius but if you

change the pressure you can change when

water turns to gas you can even do this

by walking up a mountain at the top of

mount everest where air pressure is a

third of what we see at sea level water

turns to gas at only 68 degrees celsius

and in the haitian the much thicker

atmosphere meant that the reverse was

happening it was so thick that even when

the surface was 230 degrees celsius

water didn't boil so our first ocean was

super heated fortunately for us that

superheated ocean didn't last by the end

of the haitian four billion years ago

the surface of the earth was very

similar to what it's like today a rocky

crust an ocean of liquid but not

superheated water and an atmosphere of

about the same pressure as today so from

meteorites to magma to air to

superheated oceans that should be the

story of earth's water but there's one

really big problem with this story turns

out the chemical composition of the

water and the hydrogen and chondrite

meteorites doesn't actually match the

chemical composition of most of the

water on earth the water that is in our

rocks when we say chemical composition

what we mean is isotopes or types of

hydrogen there are two really important

isotopes of hydrogen the regular brand

with one proton and one electron and

what's known as deuterium with a proton

and neutron the addition of a neutron

makes deuterium heavier than regular

hydrogen most of the deuterium in our

solar system was actually formed in the

big bang and it's a huge component of

chondrite meteorites they're heavy with

this old type of hydrogen the oceans are

pretty heavy too but our modern oceans

aren't actually a great representation

of our early water for one they're not

230 degrees celsius and for another

they've been sitting on our surface for

4.4 billion years so we know they've

undergone some changes strangely if we

want to understand what our liquid water

looked like 4.4 billion years ago we

actually have to look at the water

that's contained within our rocks when

earth's magma oceans cooled enough to

form a seal of hard rock not all the

water in the magma escaped into the

atmosphere a lot of it was trapped below

the surface in a layer of earth known as

the mantle over time pieces of the

mantle have been shoved to the surface

through plate tectonics and we've been

able to look at the hydrogen the rocks

of the mantle contain and it's a lot

lighter than the hydrogen we see in the

oceans which is part of why the source

of earth's water is still somewhat

debated how could we have such light

water in our rocks when chondrites have

such heavy water this problem has

spurred a lot of research in the last

decade scientists did find a special

meteorite called an instatite that has

lighter hydrogen but most of them think

there's not enough of these meteorites

to make up the difference then in 2021

scientists reported on some interesting

samples that were collected from an

asteroid and maybe came up with the

answer they found that the samples had a

uniquely high level of light hydrogen

but to confirm their growing suspicions

of where that hydrogen came from they

had to replicate the process so they

measured the hydrogen and water content

of olivine crystals before and after

they exposed them to the equivalent of

solar wind when they looked at them

afterwards they found that just like the

asteroid samples they had a crust of

accumulated water built with light

hydrogen so where did this light water

come from well it's literally light

water because it came from the sun solar

winds from our sun shoot out a lot of

particles including protons when those

protons hit dust in their path they can

sometimes steal an electron and a proton

plus an electron is light hydrogen slam

that light hydrogen into a rock with

some oxygen in it and boom you've made

light water or more realistically slap

that hydrogen ion into some localized

space dust or a meteorite when that

falls to earth it carries down light

water into our magma ocean which is then

trapped in our mantle over time so the

story of water on earth is

complicated during the haitian we

accumulated light water and stored it in

the rocks that became our mantle but

meteorites continued to rain down and

our oceans eventually became full of

much heavier water so the water that you

drink today has had quite a journey to

get here and it isn't all from the same

source it came from space as a

combination of meteorites and sunburnt

dust it melted into our magma then

bubbled out and rained down into

superheated puddles eventually it cooled

enough to let life form so while the

story of where earth's water came from

is incredibly complex what it ultimately

means is that your existence boils down

to space dust and sky pebbles

wednesday october 12th is national

fossil day and we've made it an annual

tradition to do something fun on the

eons channel to celebrate this year it's

a four hour live stream michelle cali

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paleontology games answering your

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you'll join us then for what we're

calling eons live an epic live stream i

would pronounce that epoch but an epoch

live stream doesn't make sense when you

say it like that

hope to see you there so now that you

know about the origins of our water be

sure to check out the search for the

earliest life to find out what might

have been the first earthling and we're

star struck by this month's eontologists

annie and eric higgins chase r shambo

colton jake hart john davidson ing alex

tamai and melanie lamb carnival by

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deep time

[Music]

anything that hit the surface would have

just melted straight into our oceans

made of magma

ah

[Music]

laser beams on their heads