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WWW.MY-SUBS.CO

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>> Earth, a unique planet,

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restless and dynamic.

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Continents shift and clash,

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volcanoes erupt,

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glaciers grow and recede--

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Titanic forces that are

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constantly at work...

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Leaving a trail

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of geological mysteries behind.

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This episode travels back

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in time to investigate

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the greatest geological

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mystery of all--

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The Birth of the Earth.

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Scientists explore how

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our planet first formed from

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the dust of the solar system,

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how molten rock solidified

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to land, how our oceans

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filled with water,

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and how life arrived on Earth.

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These are the earliest chapters

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in the incredible story

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of "How the Earth Was Made."
S02x04 Birth of the Earth
Original Air Date on December 8, 2009

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== Sync, corrected by elderman ==
== for www.MY-SUBS.com ==

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When it comes to finding clues

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to the birth of the Earth,

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our planet has been good

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at covering its tracks.

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Billions of years of erosion,

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volcanic activity,

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and the shifting of continents

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and oceans have destroyed

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almost all the evidence

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of the earliest stages

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in Earth's formation.

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For geologists trying to

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discover how and when

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the Earth first formed,

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this is a major challenge.

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>> As geologists began to

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question the age of the Earth,

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and of course they looked

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for older and older rocks,

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what we began to find was that

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the further back you go

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in Earth history, the harder it

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is to find any of those rocks.

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>> The search for the oldest

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rocks on Earth brings

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investigators to the harsh

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desert landscape of northern

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Arizona.

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This giant hole in the ground

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is meteor crater, formed

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when a massive meteorite

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slammed into the Earth.

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>> We didn't really have

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rocks from the very beginning.

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Well, where could we

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find something?

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What about the meteorites

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that have been out in space

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and fall on the Earth?

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>> It was here that geologists

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made a vital discovery.

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Meteorites are older

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than any rocks on Earth.

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They had found the key

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that would unlock the secret

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of Earth's formation.

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If the oldest rocks came

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from space, that is where

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the investigation must begin--

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in space.

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Our solar system,

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4 1/2 billion years ago.

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At its center, the young sun.

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>> The theory that emerged

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was that the sun was surrounded

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by a cloud of dust and gas,

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and as that cloud cooled, little

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grains of minerals formed.

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So all these little grains

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of minerals floating in this

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gaseous cloud are moving around

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the sun, and they start

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to bump into each other.

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>> But there was a problem

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with this theory. Nobody could

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explain how colliding

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microscopic mineral grains

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could ever create an object

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the size of a planet.

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Then in 2003, an experiment

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onboard the international

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space station accidentally

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provided extraordinary

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new evidence.

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Astronaut Don Pettit

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wanted to see what happened

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to different substances

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in the zero-gravity conditions

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of space.

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He did a simple experiment

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by pouring some salt into

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a plastic bag and shaking it.

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The results were astounding.

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The particles immediately

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began to stick to each other,

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forming little clumps,

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all held together by tiny

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static electric charges.

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Scientists realized that

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if grains of salt stuck together

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in space, then so could

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the mineral grains

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in the solar dust cloud.

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Here was real evidence

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for the fundamental mechanism

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that kickstarted the formation

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of the Earth.

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As mineral grains in the solar

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dust cloud bumped into each

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other and stuck together,

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they grew into small pieces

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of rock orbiting the sun.

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Over the next few million years,

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some of them collided

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and grew bigger.

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Many of these rocks are still

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orbiting the sun today.

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They have drifted for the past

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4 1/2 billion years...

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Unchanged from when

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they first formed.

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Occasionally they fall to Earth,

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and we call them meteorites.

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They provide scientists

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with an incredible window

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onto the past.

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>> We brought what's called

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a stony type of meteorite.

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What the scientists do then

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is slice across it

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and look on the inside.

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And to the planetary

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mineralogist, you start seeing

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all kinds of wonderful things.

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>> This meteorite contains

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minerals and metals from every

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part of the solar dust cloud.

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>> So what we're looking at

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is the assemblage of all these

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little ancient, ancient, ancient

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materials that were floating

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around the sun in the nebula

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of dust and gas, and when they

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hit each other, they gradually

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aggregated into solid bodies,

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which got bigger and bigger.

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>> Gradually, billions of these

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rocks grew as they orbited

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the sun, first to the size of

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boulders, then as big as houses.

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And they kept on growing.

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When an object reached

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about half a mile across,

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its own gravitational pull

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became strong enough to draw

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other objects towards it.

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>> Some object in this huge

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number of objects going around

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the sun, one of them

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had to be the biggest.

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And as soon as it gets bigger

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than the others, it's sweeping

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up more objects, just like

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you're driving through a cloud

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of mosquitoes at night

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in your car, and the front

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windshield is getting hit

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more often. So the bigger it is,

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the faster it grows,

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and the faster it grows,

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the more gravity it gets,

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and that pulls in more objects.

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So the biggest object starts

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to run away from the crowd.

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It starts to grow fastest.

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>> And that biggest object...

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Was the fledgling Earth.

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Soon the young planet had

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so much gravitational pull

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that it began to attract

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bigger and bigger objects.

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As they crashed onto its

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surface, Earth's size increased

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with every impact.

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The bombardment was so intense

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that it only took about

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30 million years for the planet

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to grow to almost

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its present size.

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The young Earth was made

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of billions of pieces of rock

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randomly stuck together.

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But geologists know

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that the modern Earth

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is not like that.

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Below the surface, Earth is

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separated into distinct layers--

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a thin crust, then a massive

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dense layer of rock called

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the mantle, and at the center,

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an iron and nickel core.

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Some extraordinary event

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must have occurred

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to transform the interior

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of the young planet.

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Geologists now believe

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that soon after it formed,

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the Earth completely melted.

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>> Originally the Earth was

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probably just a big collection

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of rocks like this,

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but it heated up to the point

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where these rocks all melted,

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and when that happened,

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the denser elements sank down

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through to the very core

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of the Earth, and the lighter

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elements floated at the top.

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>> The huge gravitational pull

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dragged the heavy iron

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and nickel down to form the core

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and separated the rest

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of the planet into layers.

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What caused such a huge mass

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of rock and metal to heat up

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in the freezing depths of space

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puzzled geologists

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for many years.

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>> We think it's from

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the incorporation of very hot

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radioactive elements.

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They're out there floating

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in space. As the Earth accretes,

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it includes some of this

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ferociously hot material.

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As it gets inside there,

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it begins to heat up

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the rocks around it.

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And if you build the Earth

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fast enough and you incorporate

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enough of these really hot

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radioactive elements, it will be

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enough to melt the Earth

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from the inside out.

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>> Only 30 million years

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after it began to form,

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Earth had become a giant

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round ball of boiling liquid

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rock and metal orbiting the sun.

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>> Imagine a totally molten

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world. I mean, it had

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molten magma oceans.

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No dry land anywhere. No water.

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Just flowing lava everywhere.

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>> The temperature of the molten

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Earth was now a staggering

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2,000 degrees.

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But at the edge of the planet,

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the vacuum of space

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is a constant minus 450 degrees,

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almost 2,500 degrees colder.

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The surface rock could not

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stay molten for long.

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>> It's cooling from the outside

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in, so from the outside,

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it begins to crust over,

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and you get this little scab,

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like on a wound, of cooled rock

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that's still really hot

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and then gradually begins

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to cool from the outside in.

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>> In less than a million years,

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Earth's surface was covered

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in a thin crust.

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But volcanoes still spewed out

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lava and choking gases.

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00:10:40,626 --> 00:10:42,059
Meteorites rained down

293
00:10:42,161 --> 00:10:44,529
in a constant bombardment.

294
00:10:47,332 --> 00:10:48,599
Earth had a long way to go

295
00:10:48,700 --> 00:10:49,801
before it could support

296
00:10:49,902 --> 00:10:55,540
continents, oceans, and life.

297
00:10:55,607 --> 00:10:56,774
Scientists investigating the

298
00:10:56,809 --> 00:10:58,543
earliest origins of the Earth

299
00:10:58,610 --> 00:10:59,610
have uncovered evidence

300
00:10:59,678 --> 00:11:02,346
from salt grains in space.

301
00:11:02,414 --> 00:11:03,347
They reveal that the Earth

302
00:11:03,448 --> 00:11:04,682
began to form when fragments

303
00:11:04,716 --> 00:11:05,950
of the solar dust cloud

304
00:11:05,984 --> 00:11:08,152
stuck together.

305
00:11:08,187 --> 00:11:09,520
The Earth's internal layers

306
00:11:09,588 --> 00:11:10,888
provide the clue that,

307
00:11:10,989 --> 00:11:12,723
soon after it formed, the young

308
00:11:12,791 --> 00:11:15,827
planet completely melted.

309
00:11:15,894 --> 00:11:17,628
Scientists had worked out

310
00:11:17,729 --> 00:11:19,597
how the Earth first formed

311
00:11:19,631 --> 00:11:21,899
from a cloud of dust in space.

312
00:11:21,967 --> 00:11:22,967
But they were missing

313
00:11:23,001 --> 00:11:25,269
a vital piece of the puzzle.

314
00:11:25,337 --> 00:11:26,637
They still did not know

315
00:11:26,738 --> 00:11:30,341
the age of the Earth.

316
00:11:34,379 --> 00:11:35,312
>> Billions of years

317
00:11:35,413 --> 00:11:36,947
before humans evolved,

318
00:11:36,982 --> 00:11:39,250
tiny mineral grains in space

319
00:11:39,317 --> 00:11:40,451
clumped together to form

320
00:11:40,519 --> 00:11:42,086
the molten ball that became

321
00:11:42,187 --> 00:11:44,288
the Earth.

322
00:11:47,826 --> 00:11:50,094
But exactly when that happened

323
00:11:50,195 --> 00:11:51,795
is a question that has taxed

324
00:11:51,830 --> 00:11:53,264
the minds of scholars

325
00:11:53,365 --> 00:11:56,100
and scientists for centuries.

326
00:11:59,437 --> 00:12:02,540
In 1650, the Irish archbishop

327
00:12:02,641 --> 00:12:04,008
James Ussher added up

328
00:12:04,075 --> 00:12:05,709
the ages of all the prophets

329
00:12:05,744 --> 00:12:08,012
and kings in the Bible.

330
00:12:08,079 --> 00:12:09,280
His calculations led him

331
00:12:09,381 --> 00:12:11,482
to very precise conclusions

332
00:12:11,550 --> 00:12:13,384
that Earth was created

333
00:12:13,485 --> 00:12:15,653
at nightfall before Sunday,

334
00:12:15,720 --> 00:12:19,557
October 23, 4004 B.C.

335
00:12:21,826 --> 00:12:23,627
A century later, geologists

336
00:12:23,662 --> 00:12:24,995
realized that Earth's

337
00:12:25,030 --> 00:12:26,363
thick layers of sediments

338
00:12:26,398 --> 00:12:27,998
and volcanic lavas must have

339
00:12:28,033 --> 00:12:30,100
been laid down over millions

340
00:12:30,202 --> 00:12:34,038
rather than thousands of years.

341
00:12:34,105 --> 00:12:36,173
The next breakthrough came

342
00:12:36,208 --> 00:12:38,576
in 1897, when physicist

343
00:12:38,677 --> 00:12:40,044
Ernest Rutherford figured out

344
00:12:40,111 --> 00:12:41,946
that measuring radioactive decay

345
00:12:42,013 --> 00:12:43,314
could accurately date

346
00:12:43,381 --> 00:12:46,684
the age of rocks.

347
00:12:46,751 --> 00:12:48,219
Rock samples from around

348
00:12:48,286 --> 00:12:49,820
the globe were found to be

349
00:12:49,888 --> 00:12:51,121
not just millions,

350
00:12:51,223 --> 00:12:54,291
but billions of years old.

351
00:12:54,326 --> 00:12:56,493
But in their hunt for the age

352
00:12:56,595 --> 00:12:58,596
of the Earth, scientists hit

353
00:12:58,663 --> 00:13:00,864
a major obstacle.

354
00:13:04,402 --> 00:13:05,669
Rocks from the earliest

355
00:13:05,770 --> 00:13:07,137
stages in Earth history

356
00:13:07,239 --> 00:13:10,474
are very hard to find.

357
00:13:10,475 --> 00:13:11,742
>> If you want to go back

358
00:13:11,776 --> 00:13:13,277
as a geologist and try to find

359
00:13:13,378 --> 00:13:15,045
evidence of those early days,

360
00:13:15,046 --> 00:13:16,247
it's very hard to do

361
00:13:16,348 --> 00:13:17,514
on the Earth because, of course,

362
00:13:17,616 --> 00:13:18,882
we have rain eroding,

363
00:13:18,950 --> 00:13:19,984
we have tectonics

364
00:13:20,051 --> 00:13:21,452
and continental drift

365
00:13:21,519 --> 00:13:22,886
destroying continental surfaces.

366
00:13:22,954 --> 00:13:24,722
We simply can't find the rocks

367
00:13:24,789 --> 00:13:28,425
that go back to that age.

368
00:13:28,460 --> 00:13:30,894
>> In the early 1950's,

369
00:13:30,962 --> 00:13:32,363
the American geologist

370
00:13:32,430 --> 00:13:33,731
C.C. Patterson tried

371
00:13:33,798 --> 00:13:39,270
a new approach using meteorites.

372
00:13:39,337 --> 00:13:40,804
He knew that meteorites

373
00:13:40,905 --> 00:13:42,273
must have clumped together

374
00:13:42,340 --> 00:13:43,540
from the same mineral grains

375
00:13:43,642 --> 00:13:46,443
in space that formed the Earth.

376
00:13:46,511 --> 00:13:47,911
And that happened at the same

377
00:13:47,979 --> 00:13:50,714
time as the Earth was born.

378
00:13:50,782 --> 00:13:53,984
So if he could date a meteorite,

379
00:13:54,019 --> 00:13:55,452
he should get the true age

380
00:13:55,553 --> 00:13:58,355
of the Earth.

381
00:13:58,423 --> 00:14:00,658
In 1953, Patterson came

382
00:14:00,725 --> 00:14:03,260
to meteor crater in Arizona

383
00:14:03,295 --> 00:14:06,797
looking for samples.

384
00:14:06,831 --> 00:14:08,299
The meteorite which blasted out

385
00:14:08,366 --> 00:14:09,933
this enormous crater was

386
00:14:10,001 --> 00:14:12,469
about 50 yards across.

387
00:14:12,537 --> 00:14:13,570
It slammed into the Earth

388
00:14:13,638 --> 00:14:17,107
at a fantastic speed.

389
00:14:17,208 --> 00:14:18,542
>> Objects hitting the Earth

390
00:14:18,576 --> 00:14:20,477
from space may typically come in

391
00:14:20,545 --> 00:14:23,647
at 10 or 15 miles per second,

392
00:14:23,715 --> 00:14:24,648
hitting the ground,

393
00:14:24,716 --> 00:14:26,216
penetrating into the ground,

394
00:14:26,284 --> 00:14:28,719
generating enormous pressure

395
00:14:28,753 --> 00:14:30,287
and shockwave and creating

396
00:14:30,388 --> 00:14:32,823
a huge explosion.

397
00:14:32,924 --> 00:14:34,491
>> The meteorite hit the Earth

398
00:14:34,559 --> 00:14:36,293
with the force of a 2-megaton

399
00:14:36,394 --> 00:14:38,662
atomic bomb. The explosion

400
00:14:38,763 --> 00:14:41,131
vaporized most of the meteorite,

401
00:14:41,199 --> 00:14:42,566
but individual fragments

402
00:14:42,667 --> 00:14:44,768
survived.

403
00:14:44,836 --> 00:14:46,570
>> This is one of the pieces

404
00:14:46,671 --> 00:14:49,273
of the object that crashed into

405
00:14:49,307 --> 00:14:51,275
the Earth and made this crater.

406
00:14:51,309 --> 00:14:53,210
This is pure iron.

407
00:14:53,311 --> 00:14:54,478
We know it's iron because,

408
00:14:54,579 --> 00:14:56,013
for example, it's magnetic.

409
00:14:56,047 --> 00:14:57,681
An amazing piece of something

410
00:14:57,749 --> 00:14:59,950
that was floating in space.

411
00:15:00,018 --> 00:15:01,218
This was the kind of place

412
00:15:01,286 --> 00:15:02,753
that people could get samples

413
00:15:02,821 --> 00:15:05,022
for the first radiometric dating

414
00:15:05,056 --> 00:15:06,757
of meteorites.

415
00:15:06,825 --> 00:15:08,726
And so Patterson came here

416
00:15:08,827 --> 00:15:11,862
and got samples like this.

417
00:15:11,963 --> 00:15:13,864
>> Patterson dated the samples

418
00:15:13,965 --> 00:15:17,234
and was amazed by the results.

419
00:15:17,302 --> 00:15:19,503
The meteorite was a staggering

420
00:15:19,571 --> 00:15:23,607
4.5 billion years old...

421
00:15:23,675 --> 00:15:25,876
Meaning that the Earth was also

422
00:15:25,944 --> 00:15:30,381
born 4.5 billion years ago.

423
00:15:30,415 --> 00:15:32,416
Patterson had solved the problem

424
00:15:32,484 --> 00:15:34,151
that had defeated scientists

425
00:15:34,219 --> 00:15:36,420
for centuries.

426
00:15:36,521 --> 00:15:38,255
>> There's this apocryphal story

427
00:15:38,323 --> 00:15:39,857
that Patterson got so excited

428
00:15:39,958 --> 00:15:41,692
about the date that was coming

429
00:15:41,793 --> 00:15:43,060
back from the laboratory

430
00:15:43,128 --> 00:15:44,695
and so hyper about it,

431
00:15:44,796 --> 00:15:45,496
he thought he was having

432
00:15:45,530 --> 00:15:46,864
a heart attack, and he was

433
00:15:46,931 --> 00:15:48,132
driven to the hospital,

434
00:15:48,166 --> 00:15:49,166
and it turned out to be

435
00:15:49,234 --> 00:15:50,300
just his excitement

436
00:15:50,335 --> 00:15:53,570
over this fantastic discovery.

437
00:15:53,605 --> 00:15:55,139
>> Modern radiometric dating

438
00:15:55,240 --> 00:15:56,306
techniques have refined

439
00:15:56,341 --> 00:15:57,608
the age of the Earth to

440
00:15:57,709 --> 00:16:00,144
a remarkable degree of accuracy.

441
00:16:00,245 --> 00:16:02,713
The most recent study

442
00:16:02,781 --> 00:16:04,415
dates the Earth as

443
00:16:04,449 --> 00:16:09,787
4,567,000,000 years old.

444
00:16:09,888 --> 00:16:11,722
So scientists now knew how

445
00:16:11,790 --> 00:16:15,225
and when the Earth was formed.

446
00:16:15,260 --> 00:16:16,860
But nobody had figured out

447
00:16:16,895 --> 00:16:20,798
what happened next.

448
00:16:20,865 --> 00:16:22,900
Then in 1974,

449
00:16:23,001 --> 00:16:25,636
a radical new theory emerged.

450
00:16:25,703 --> 00:16:27,704
In the early solar system, there

451
00:16:27,806 --> 00:16:29,907
were dozens of mini-planets

452
00:16:29,974 --> 00:16:32,176
chaotically orbiting the sun.

453
00:16:32,243 --> 00:16:33,444
According to the theory,

454
00:16:33,545 --> 00:16:34,411
one of these was on

455
00:16:34,446 --> 00:16:38,549
a collision course with Earth.

456
00:16:38,616 --> 00:16:40,717
The idea was the brainchild

457
00:16:40,819 --> 00:16:42,453
of Bill Hartmann, who was trying

458
00:16:42,554 --> 00:16:43,987
to explain the origin

459
00:16:44,055 --> 00:16:45,622
not of the Earth,

460
00:16:45,690 --> 00:16:48,258
but of the moon.

461
00:16:48,359 --> 00:16:49,993
>> What we came up with was that

462
00:16:50,094 --> 00:16:51,728
maybe during that period

463
00:16:51,796 --> 00:16:54,465
of intense impacts,

464
00:16:54,566 --> 00:16:56,099
maybe a very large impact

465
00:16:56,167 --> 00:16:57,568
hit the Earth and blew some

466
00:16:57,635 --> 00:16:59,703
crustal outer mantle rock

467
00:16:59,737 --> 00:17:02,105
off of the Earth into space

468
00:17:02,207 --> 00:17:03,273
around the Earth, and the moon

469
00:17:03,341 --> 00:17:05,742
formed from that material.

470
00:17:05,844 --> 00:17:07,744
>> Hartmann suggested that

471
00:17:07,812 --> 00:17:09,646
another planet, about the size

472
00:17:09,714 --> 00:17:13,283
of Mars, crashed into the Earth.

473
00:17:21,292 --> 00:17:23,560
He claimed that the moon

474
00:17:23,661 --> 00:17:24,761
could have been formed

475
00:17:24,829 --> 00:17:29,466
by debris from that collision.

476
00:17:29,534 --> 00:17:31,201
To many scientists,

477
00:17:31,302 --> 00:17:33,403
this was nothing but fantasy,

478
00:17:33,471 --> 00:17:35,839
but Hartmann had evidence...

479
00:17:38,943 --> 00:17:43,847
Collected from the moon itself.

480
00:17:43,948 --> 00:17:45,849
>> If I fall in the...

481
00:17:45,950 --> 00:17:47,017
in the plumb crater

482
00:17:47,085 --> 00:17:48,752
getting this rock.

483
00:17:48,820 --> 00:17:50,020
>> Footage from the Apollo XVI

484
00:17:50,121 --> 00:17:52,289
mission in April 1972

485
00:17:52,323 --> 00:17:54,224
shows astronaut Charles Duke

486
00:17:54,292 --> 00:17:55,325
struggling to pick up

487
00:17:55,393 --> 00:17:57,194
a large sample of moon rock

488
00:17:57,228 --> 00:17:58,662
to bring back to Earth

489
00:17:58,763 --> 00:18:00,864
for geologists to analyze.

490
00:18:00,932 --> 00:18:03,767
>> That's 20 pounds of rocks.

491
00:18:03,868 --> 00:18:05,502
>> At the Johnson Space Center

492
00:18:05,570 --> 00:18:07,571
in Houston, this actual piece

493
00:18:07,672 --> 00:18:09,673
of moon rock is still kept under

494
00:18:09,774 --> 00:18:13,010
strict laboratory conditions.

495
00:18:13,044 --> 00:18:15,345
>> I would say, behold the moon.

496
00:18:15,413 --> 00:18:16,647
This is an actual piece

497
00:18:16,681 --> 00:18:17,681
of the moon, and it's

498
00:18:17,749 --> 00:18:19,383
the largest single rock

499
00:18:19,417 --> 00:18:20,417
that they brought back

500
00:18:20,518 --> 00:18:21,952
from the surface of the moon

501
00:18:22,020 --> 00:18:23,153
when the Apollo astronauts

502
00:18:23,221 --> 00:18:24,154
went there.

503
00:18:24,222 --> 00:18:25,055
We can't touch it.

504
00:18:25,156 --> 00:18:26,323
They don't want human beings

505
00:18:26,424 --> 00:18:27,491
touching these rocks

506
00:18:27,525 --> 00:18:28,692
and leaving organic material

507
00:18:28,760 --> 00:18:31,228
on them.

508
00:18:31,329 --> 00:18:32,796
>> Until the late 1960's,

509
00:18:32,864 --> 00:18:34,331
geologists thought that the moon

510
00:18:34,399 --> 00:18:35,966
formed in the same way as

511
00:18:36,034 --> 00:18:38,068
the Earth, by clumps of mineral

512
00:18:38,136 --> 00:18:39,436
grains sticking together

513
00:18:39,504 --> 00:18:41,772
in the solar dust cloud.

514
00:18:41,806 --> 00:18:43,707
They believed it had layers

515
00:18:43,775 --> 00:18:44,975
like the Earth

516
00:18:45,043 --> 00:18:48,345
and a heavy iron core.

517
00:18:48,413 --> 00:18:49,613
But when geologists analyzed

518
00:18:49,681 --> 00:18:51,248
lunar samples, they were

519
00:18:51,316 --> 00:18:52,783
astonished to discover that

520
00:18:52,884 --> 00:18:54,351
the moon rocks contained much

521
00:18:54,419 --> 00:18:57,487
less iron than they expected.

522
00:18:57,522 --> 00:18:58,422
>> One of the mysteries

523
00:18:58,489 --> 00:18:59,790
has always been why isn't there

524
00:18:59,857 --> 00:19:01,258
as much iron in the moon

525
00:19:01,359 --> 00:19:02,693
as there is on the Earth,

526
00:19:02,794 --> 00:19:03,894
if the two objects are

527
00:19:03,962 --> 00:19:06,630
right close together in space?

528
00:19:06,698 --> 00:19:08,065
>> The question bothered

529
00:19:08,132 --> 00:19:09,967
Hartmann so much that he began

530
00:19:10,068 --> 00:19:11,401
to think that conventional

531
00:19:11,436 --> 00:19:12,769
theories about how the moon

532
00:19:12,804 --> 00:19:15,238
formed might be wrong.

533
00:19:15,273 --> 00:19:19,076
>> That lack of iron in the moon

534
00:19:19,177 --> 00:19:20,344
or to put it another way,

535
00:19:20,411 --> 00:19:21,411
the fact that the moon

536
00:19:21,446 --> 00:19:22,913
is made out of rock that looks

537
00:19:22,981 --> 00:19:24,615
like the crust and the upper

538
00:19:24,682 --> 00:19:26,984
mantle material of the Earth,

539
00:19:27,085 --> 00:19:31,521
that was a clue that the moon

540
00:19:31,623 --> 00:19:33,323
may have formed from rocks

541
00:19:33,358 --> 00:19:34,825
from the outer portion

542
00:19:34,892 --> 00:19:36,460
of the Earth.

543
00:19:36,527 --> 00:19:38,462
>> This was the key

544
00:19:38,529 --> 00:19:40,464
to Hartmann's idea

545
00:19:40,531 --> 00:19:41,965
of a collision between Earth

546
00:19:42,000 --> 00:19:44,167
and another planet.

547
00:19:47,605 --> 00:19:48,905
The force of the impact

548
00:19:49,007 --> 00:19:50,507
completely destroyed

549
00:19:50,575 --> 00:19:52,442
the other planet and flung

550
00:19:52,510 --> 00:19:54,077
billions of tons of Earth's

551
00:19:54,145 --> 00:19:56,513
crust and mantle out into space

552
00:19:56,614 --> 00:19:59,149
and into orbit around the Earth.

553
00:20:02,220 --> 00:20:03,620
Within a few thousand years,

554
00:20:03,721 --> 00:20:05,489
this debris clumped together

555
00:20:05,523 --> 00:20:07,724
to form the moon.

556
00:20:12,163 --> 00:20:13,530
Advanced computer models

557
00:20:13,598 --> 00:20:14,598
show that the collision

558
00:20:14,632 --> 00:20:16,533
was a glancing blow.

559
00:20:16,601 --> 00:20:17,501
The other planet did not

560
00:20:17,535 --> 00:20:20,637
hit Earth head-on.

561
00:20:20,705 --> 00:20:21,872
This meant that while Earth's

562
00:20:21,906 --> 00:20:23,440
outer layers were ripped off,

563
00:20:23,508 --> 00:20:24,875
none of its iron core

564
00:20:24,909 --> 00:20:27,077
was blasted away.

565
00:20:27,178 --> 00:20:28,779
>> That lack of iron would

566
00:20:28,813 --> 00:20:30,247
end up explaining why

567
00:20:30,281 --> 00:20:32,349
we have a moon that is

568
00:20:32,450 --> 00:20:33,450
only the rocky material

569
00:20:33,518 --> 00:20:35,986
without the iron material.

570
00:20:36,087 --> 00:20:38,088
>> Hartmann's collision idea

571
00:20:38,156 --> 00:20:40,824
is now accepted as fact.

572
00:20:40,892 --> 00:20:42,926
It was his fascination

573
00:20:42,994 --> 00:20:44,361
with the moon that led

574
00:20:44,462 --> 00:20:45,829
to a new understanding

575
00:20:45,897 --> 00:20:47,064
about a vital stage

576
00:20:47,098 --> 00:20:50,834
in the formation of the Earth.

577
00:20:50,902 --> 00:20:51,902
>> The moon always, to me,

578
00:20:52,003 --> 00:20:53,537
is a reminder that we live

579
00:20:53,638 --> 00:20:56,106
in a larger environment

580
00:20:56,174 --> 00:20:57,174
than just the Earth.

581
00:20:57,241 --> 00:20:58,642
It's the cosmic environment.

582
00:20:58,710 --> 00:20:59,810
The inner solar system

583
00:20:59,911 --> 00:21:00,744
is our environment

584
00:21:00,812 --> 00:21:03,547
that we can move around in now.

585
00:21:03,648 --> 00:21:04,915
>> In the quest to discover

586
00:21:04,982 --> 00:21:06,650
the age of the Earth,

587
00:21:06,751 --> 00:21:08,285
evidence from radiometric dating

588
00:21:08,352 --> 00:21:09,553
of meteorites proves

589
00:21:09,654 --> 00:21:11,021
that the Earth was formed

590
00:21:11,089 --> 00:21:15,092
just over 4.5 billion years ago.

591
00:21:15,193 --> 00:21:17,094
The lack of iron in rocks

592
00:21:17,161 --> 00:21:18,462
brought back from the moon

593
00:21:18,563 --> 00:21:19,896
is evidence that the Earth

594
00:21:19,931 --> 00:21:21,732
survived a massive collision

595
00:21:21,766 --> 00:21:23,900
with another planet.

596
00:21:23,935 --> 00:21:25,736
But vital parts of the modern

597
00:21:25,837 --> 00:21:27,204
Earth were still missing

598
00:21:27,271 --> 00:21:30,373
from the newly born planet.

599
00:21:30,475 --> 00:21:31,641
The investigation now needs

600
00:21:31,676 --> 00:21:33,376
to figure out how the Earth

601
00:21:33,444 --> 00:21:36,113
gained 2 essential components--

602
00:21:36,180 --> 00:21:38,582
solid land...

603
00:21:38,649 --> 00:21:40,951
And water.

604
00:21:47,200 --> 00:21:49,902
>> 4.5 billion years ago,

605
00:21:49,936 --> 00:21:51,437
Earth formed out of the solar

606
00:21:51,471 --> 00:21:53,372
dust cloud, then survived

607
00:21:53,473 --> 00:21:55,007
a devastating impact

608
00:21:55,108 --> 00:21:57,276
with another planet.

609
00:22:00,080 --> 00:22:01,647
The investigation now moves

610
00:22:01,715 --> 00:22:03,549
200 million years forward

611
00:22:03,583 --> 00:22:05,618
in time, as scientists try

612
00:22:05,652 --> 00:22:06,852
to discover how the first

613
00:22:06,920 --> 00:22:11,924
continents and oceans formed.

614
00:22:11,992 --> 00:22:13,559
They are looking for evidence

615
00:22:13,627 --> 00:22:15,127
on the northeast shores

616
00:22:15,195 --> 00:22:17,830
of Hudson Bay, Canada.

617
00:22:20,767 --> 00:22:23,636
This is the desolate landscape

618
00:22:23,670 --> 00:22:25,404
of Porpoise Cove,

619
00:22:25,472 --> 00:22:27,039
the site of an important new

620
00:22:27,107 --> 00:22:29,775
scientific discovery.

621
00:22:29,843 --> 00:22:31,744
And it's all down to a young

622
00:22:31,778 --> 00:22:33,946
Ph.D. student's fascination

623
00:22:34,014 --> 00:22:36,048
with ancient rocks.

624
00:22:36,116 --> 00:22:37,216
>> I was interested in studying

625
00:22:37,284 --> 00:22:38,851
the early Earth, so the idea

626
00:22:38,852 --> 00:22:40,586
is to get as far as we can back

627
00:22:40,687 --> 00:22:43,022
in time, to get these old rocks

628
00:22:43,023 --> 00:22:44,924
and study rocks that were there

629
00:22:44,958 --> 00:22:47,226
in the past.

630
00:22:47,327 --> 00:22:48,961
>> Geologists already knew

631
00:22:49,029 --> 00:22:50,463
that rocks in this part

632
00:22:50,497 --> 00:22:51,664
of northern Canada

633
00:22:51,698 --> 00:22:53,666
are extremely old.

634
00:22:53,700 --> 00:22:56,135
But something about a small area

635
00:22:56,236 --> 00:22:58,337
in this vast wilderness

636
00:22:58,405 --> 00:23:00,673
caught O'Neil's eye.

637
00:23:00,774 --> 00:23:01,941
>> The overall aspect

638
00:23:01,975 --> 00:23:03,309
of the rocks really looked

639
00:23:03,376 --> 00:23:05,411
different, and right away

640
00:23:05,479 --> 00:23:06,412
we knew that something was

641
00:23:06,513 --> 00:23:07,947
really bizarre, really unusual

642
00:23:07,981 --> 00:23:10,316
about these rocks.

643
00:23:10,383 --> 00:23:12,685
>> The rocks are highly altered

644
00:23:12,752 --> 00:23:14,487
deformed volcanic lavas

645
00:23:14,521 --> 00:23:17,957
known as amphibolites.

646
00:23:18,024 --> 00:23:19,692
>> The chemistry was unusual.

647
00:23:19,759 --> 00:23:21,694
The mineralogy was unusual.

648
00:23:21,795 --> 00:23:22,528
And nobody had seen

649
00:23:22,596 --> 00:23:24,597
rocks like that before.

650
00:23:24,698 --> 00:23:25,898
>> O'Neil decided the rocks

651
00:23:25,966 --> 00:23:27,967
needed further investigation.

652
00:23:28,068 --> 00:23:29,401
He sent samples to be

653
00:23:29,436 --> 00:23:31,704
radiometrically dated.

654
00:23:34,407 --> 00:23:37,810
The results were astounding.

655
00:23:37,878 --> 00:23:39,512
>> We were in the lab

656
00:23:39,579 --> 00:23:40,679
in Washington, D.C.,

657
00:23:40,747 --> 00:23:41,914
when we first got the first

658
00:23:41,948 --> 00:23:43,582
number out of the machine.

659
00:23:43,683 --> 00:23:44,950
And the first reaction is

660
00:23:45,018 --> 00:23:46,485
we didn't believe it.

661
00:23:46,586 --> 00:23:49,054
So what you do is you reanalyze

662
00:23:49,122 --> 00:23:51,657
the rock a second time.

663
00:23:51,691 --> 00:23:52,491
And then the same number

664
00:23:52,559 --> 00:23:53,859
comes up, and then a third time,

665
00:23:53,960 --> 00:23:55,561
and then again and again.

666
00:23:55,595 --> 00:23:56,962
So you say, "ok. We'll analyze

667
00:23:57,030 --> 00:23:58,330
"more of these rocks,

668
00:23:58,398 --> 00:24:00,032
because I can't believe it."

669
00:24:00,133 --> 00:24:01,834
And these numbers,

670
00:24:01,868 --> 00:24:03,202
this signature, this really,

671
00:24:03,236 --> 00:24:04,136
really old signature

672
00:24:04,237 --> 00:24:05,137
keeps coming up,

673
00:24:05,238 --> 00:24:05,971
keeps coming up,

674
00:24:06,039 --> 00:24:06,972
and keeps coming up.

675
00:24:07,040 --> 00:24:07,840
And in the end, you have to

676
00:24:07,874 --> 00:24:08,774
come to the conclusion

677
00:24:08,875 --> 00:24:09,742
that these rocks have been

678
00:24:09,776 --> 00:24:11,877
formed nearly 4.3 billion

679
00:24:11,945 --> 00:24:13,612
years ago.

680
00:24:13,680 --> 00:24:14,880
>> The results were

681
00:24:14,948 --> 00:24:17,950
indisputable.

682
00:24:18,018 --> 00:24:19,618
The amphibolites are

683
00:24:19,686 --> 00:24:23,789
4.28 billion years old,

684
00:24:23,890 --> 00:24:25,591
200 million years older

685
00:24:25,659 --> 00:24:26,892
than any other rocks

686
00:24:26,960 --> 00:24:29,328
so far discovered.

687
00:24:31,197 --> 00:24:32,831
They are the closest

688
00:24:32,866 --> 00:24:34,400
anyone has come to finding

689
00:24:34,467 --> 00:24:37,670
Earth's original crust.

690
00:24:37,771 --> 00:24:39,038
>> These are the oldest rocks

691
00:24:39,105 --> 00:24:40,139
in the world, and it's amazing

692
00:24:40,206 --> 00:24:41,574
when you stand on it.

693
00:24:41,641 --> 00:24:44,043
You can try to imagine yourself

694
00:24:44,110 --> 00:24:46,745
almost 4.3 billion years ago,

695
00:24:46,780 --> 00:24:47,913
when the Earth was so young

696
00:24:47,948 --> 00:24:50,916
and just barely forming...

697
00:24:50,951 --> 00:24:53,586
Walking on this landscape, and

698
00:24:53,687 --> 00:24:56,956
it's a really amazing feeling.

699
00:24:57,057 --> 00:24:58,490
>> These rocks are now yielding

700
00:24:58,558 --> 00:24:59,959
clues about the thickness

701
00:25:00,060 --> 00:25:02,595
of the early crust.

702
00:25:02,662 --> 00:25:04,797
O'Neil has found unusual

703
00:25:04,831 --> 00:25:06,532
minerals which can only form

704
00:25:06,566 --> 00:25:08,300
in conditions of very high

705
00:25:08,368 --> 00:25:10,369
temperature and pressure.

706
00:25:10,470 --> 00:25:12,571
They prove that the amphibolites

707
00:25:12,639 --> 00:25:14,807
were made at least 12 miles down

708
00:25:14,841 --> 00:25:17,643
in the crust of the Earth.

709
00:25:17,744 --> 00:25:19,545
This means that more than

710
00:25:19,579 --> 00:25:21,113
4 billion years ago,

711
00:25:21,181 --> 00:25:22,581
Earth had a solid crust

712
00:25:22,649 --> 00:25:25,384
at least 12 miles thick,

713
00:25:25,452 --> 00:25:27,219
and a crust that thick suggests

714
00:25:27,287 --> 00:25:30,289
there must have been continents.

715
00:25:33,994 --> 00:25:36,395
And there's more. Evidence

716
00:25:36,463 --> 00:25:37,930
hidden in the amphibolites

717
00:25:38,031 --> 00:25:39,398
reveals that these rocks

718
00:25:39,499 --> 00:25:41,100
must have originally formed

719
00:25:41,134 --> 00:25:43,369
deep underwater.

720
00:25:43,470 --> 00:25:44,470
>> Well, you have to understand

721
00:25:44,504 --> 00:25:45,738
that when rocks form,

722
00:25:45,772 --> 00:25:47,406
they can record their chemical

723
00:25:47,474 --> 00:25:49,041
signature, and depending on

724
00:25:49,109 --> 00:25:50,676
where the rocks are forming,

725
00:25:50,777 --> 00:25:52,011
in what geological context

726
00:25:52,045 --> 00:25:53,145
they will be formed,

727
00:25:53,213 --> 00:25:54,113
they will carry that

728
00:25:54,147 --> 00:25:56,482
specific chemical signature.

729
00:25:56,583 --> 00:25:58,784
>> The chemical signature

730
00:25:58,852 --> 00:26:01,420
of the amphibolites is unique.

731
00:26:01,488 --> 00:26:03,222
It proves that when these rocks

732
00:26:03,289 --> 00:26:05,324
formed, Earth had not only

733
00:26:05,425 --> 00:26:09,428
a solid crust, but oceans.

734
00:26:13,133 --> 00:26:14,700
>> The signature we see here,

735
00:26:14,768 --> 00:26:15,768
it really looks like

736
00:26:15,869 --> 00:26:17,503
an oceanic floor.

737
00:26:17,570 --> 00:26:19,872
That means there was an ocean

738
00:26:19,939 --> 00:26:21,507
and a lot of water already

739
00:26:21,608 --> 00:26:24,209
at 4.28 billion years old.

740
00:26:24,244 --> 00:26:25,344
So it totally changes our view

741
00:26:25,412 --> 00:26:26,512
of what the Earth

742
00:26:26,579 --> 00:26:28,781
was like before.

743
00:26:28,848 --> 00:26:30,983
>> To the scientific world,

744
00:26:31,051 --> 00:26:35,220
this idea is dynamite.

745
00:26:35,255 --> 00:26:38,390
But O'Neil is not on his own.

746
00:26:38,425 --> 00:26:39,758
There is more evidence

747
00:26:39,793 --> 00:26:42,261
to back up his claim.

748
00:26:42,328 --> 00:26:44,396
In the same ancient rock

749
00:26:44,431 --> 00:26:45,798
sequence, geologists find

750
00:26:45,899 --> 00:26:47,700
another unexpected rock type

751
00:26:47,767 --> 00:26:52,705
called banded iron formations.

752
00:26:52,806 --> 00:26:54,707
These rocks are made up

753
00:26:54,774 --> 00:26:56,341
of alternating light layers

754
00:26:56,443 --> 00:26:58,343
of silica and dark bands full

755
00:26:58,411 --> 00:27:00,779
of a mineral called magnetite,

756
00:27:00,814 --> 00:27:02,247
which, as the name suggests,

757
00:27:02,348 --> 00:27:04,817
are rich in iron.

758
00:27:04,818 --> 00:27:05,584
>> We usually use a magnet

759
00:27:05,618 --> 00:27:08,687
to try to find these minerals.

760
00:27:08,688 --> 00:27:09,888
It's a quick and easy way

761
00:27:09,956 --> 00:27:12,458
to identify for sure those rocks

762
00:27:12,525 --> 00:27:15,160
as banded iron formations.

763
00:27:15,228 --> 00:27:16,462
>> Magnetite in banded iron

764
00:27:16,529 --> 00:27:17,963
formations only forms

765
00:27:17,997 --> 00:27:20,899
underwater. So these rocks

766
00:27:20,967 --> 00:27:22,901
are further evidence that

767
00:27:22,969 --> 00:27:24,436
there were oceans on Earth

768
00:27:24,504 --> 00:27:27,740
more than 4 billion years ago.

769
00:27:27,807 --> 00:27:29,007
But scientists don't know

770
00:27:29,075 --> 00:27:30,642
how much of Earth's surface

771
00:27:30,710 --> 00:27:32,978
was covered by water.

772
00:27:33,012 --> 00:27:34,379
>> The only way to form

773
00:27:34,447 --> 00:27:36,448
this magnetite is to be, like,

774
00:27:36,516 --> 00:27:39,551
in an ocean. We don't know

775
00:27:39,619 --> 00:27:41,086
exactly what was the ocean

776
00:27:41,154 --> 00:27:42,287
at that time, but we know

777
00:27:42,355 --> 00:27:43,822
for sure that we need water

778
00:27:43,923 --> 00:27:45,924
to form those rocks.

779
00:27:45,992 --> 00:27:47,659
>> These discoveries are forcing

780
00:27:47,727 --> 00:27:49,361
geologists to rethink their

781
00:27:49,462 --> 00:27:51,196
ideas of what conditions

782
00:27:51,297 --> 00:27:52,731
were like on Earth

783
00:27:52,832 --> 00:27:54,933
less than 300 million years

784
00:27:55,001 --> 00:27:57,936
after the planet formed.

785
00:27:58,004 --> 00:27:59,204
>> People often think of this

786
00:27:59,272 --> 00:28:00,706
early Earth like a ball of fire

787
00:28:00,740 --> 00:28:02,641
or molten rock, but this is not

788
00:28:02,742 --> 00:28:05,277
the picture that we see here.

789
00:28:05,345 --> 00:28:07,379
We see that, already

790
00:28:07,480 --> 00:28:09,214
at 4.28 billion years old,

791
00:28:09,282 --> 00:28:11,750
we probably had an ocean.

792
00:28:11,851 --> 00:28:13,118
We had continent that

793
00:28:13,186 --> 00:28:14,119
really, really looks like

794
00:28:14,187 --> 00:28:15,921
what we know today.

795
00:28:16,022 --> 00:28:17,289
So it changes totally our view

796
00:28:17,357 --> 00:28:19,658
of the early Earth.

797
00:28:21,494 --> 00:28:23,495
>> The investigation has now

798
00:28:23,563 --> 00:28:25,097
revealed when the Earth's

799
00:28:25,131 --> 00:28:26,665
continents and oceans

800
00:28:26,733 --> 00:28:29,001
began to form.

801
00:28:29,035 --> 00:28:30,669
Evidence from amphibolite rocks

802
00:28:30,770 --> 00:28:32,471
at Porpoise Cove confirms

803
00:28:32,572 --> 00:28:33,672
that the Earth had developed

804
00:28:33,773 --> 00:28:35,207
a thick solid crust

805
00:28:35,308 --> 00:28:39,044
4.28 billion years ago.

806
00:28:39,112 --> 00:28:40,779
Banded iron formations

807
00:28:40,847 --> 00:28:42,281
in the same rocks show that

808
00:28:42,315 --> 00:28:43,849
there were oceans on Earth's

809
00:28:43,950 --> 00:28:46,819
surface at the same time...

810
00:28:46,853 --> 00:28:48,954
All of which raises

811
00:28:49,022 --> 00:28:51,456
another mystery.

812
00:28:51,491 --> 00:28:52,758
If oceans existed

813
00:28:52,826 --> 00:28:54,827
more than 4 billion years ago,

814
00:28:54,861 --> 00:28:56,161
the investigation needs

815
00:28:56,229 --> 00:28:57,596
to figure out where all

816
00:28:57,664 --> 00:29:00,399
the water came from.

817
00:29:03,138 --> 00:29:04,238
>> After its formation

818
00:29:04,306 --> 00:29:05,506
from the solar dust cloud

819
00:29:05,574 --> 00:29:07,842
4.5 billion years ago,

820
00:29:07,876 --> 00:29:09,143
Earth was a fiery ball

821
00:29:09,244 --> 00:29:11,345
of molten rock,

822
00:29:11,413 --> 00:29:12,980
but 200 million years later,

823
00:29:13,048 --> 00:29:14,315
the first oceans were

824
00:29:14,349 --> 00:29:17,151
already forming, and Earth today

825
00:29:17,219 --> 00:29:19,353
is the blue planet,

826
00:29:19,421 --> 00:29:20,855
with 70% of its surface

827
00:29:20,889 --> 00:29:23,991
covered by water.

828
00:29:24,059 --> 00:29:25,693
The investigation now looks

829
00:29:25,794 --> 00:29:27,261
at the mystery of the origin

830
00:29:27,329 --> 00:29:30,364
of Earth's water.

831
00:29:30,432 --> 00:29:31,899
>> One of the important

832
00:29:31,967 --> 00:29:33,000
questions I've always thought

833
00:29:33,068 --> 00:29:34,535
about is, you know, where did

834
00:29:34,636 --> 00:29:35,903
all of this come from,

835
00:29:35,971 --> 00:29:36,904
all of this water,

836
00:29:36,972 --> 00:29:38,239
all the water in the oceans

837
00:29:38,240 --> 00:29:40,074
and in the atmosphere,

838
00:29:40,175 --> 00:29:42,176
in our bodies, in the ground?

839
00:29:42,177 --> 00:29:43,778
When you look at the Earth

840
00:29:43,812 --> 00:29:45,179
from space, what really

841
00:29:45,247 --> 00:29:47,248
impresses you is the water,

842
00:29:47,282 --> 00:29:50,251
how beautiful this planet is.

843
00:29:50,352 --> 00:29:51,352
Why does Earth have

844
00:29:51,453 --> 00:29:52,620
all of this water,

845
00:29:52,721 --> 00:29:54,722
and how did it get here?

846
00:29:54,823 --> 00:29:56,357
>> The question has puzzled

847
00:29:56,425 --> 00:29:58,993
geologists for years.

848
00:29:59,094 --> 00:30:00,728
Now they believe the answer

849
00:30:00,829 --> 00:30:03,364
lies in space.

850
00:30:03,465 --> 00:30:04,999
New evidence showing how

851
00:30:05,100 --> 00:30:06,734
our water arrived on Earth

852
00:30:06,835 --> 00:30:08,469
has emerged from a meteorite

853
00:30:08,537 --> 00:30:10,872
that fell in 1998 but which

854
00:30:10,973 --> 00:30:14,775
has only recently been analyzed.

855
00:30:14,877 --> 00:30:16,477
>> We found an astonishing

856
00:30:16,578 --> 00:30:18,112
thing. This meteorite

857
00:30:18,213 --> 00:30:20,281
contains grains of table salt,

858
00:30:20,315 --> 00:30:21,048
just like you'd put

859
00:30:21,116 --> 00:30:23,851
on your fish and chips.

860
00:30:23,919 --> 00:30:26,954
>> The clue is trapped inside

861
00:30:27,022 --> 00:30:28,823
the crystals of salt and

862
00:30:28,857 --> 00:30:33,094
revealed under the microscope--

863
00:30:33,128 --> 00:30:37,932
minute droplets of liquid water.

864
00:30:37,966 --> 00:30:38,866
On the computer screen, you can

865
00:30:38,967 --> 00:30:41,302
see a little fluid inclusion,

866
00:30:41,403 --> 00:30:42,937
a little drop of water,

867
00:30:42,971 --> 00:30:44,405
and you'll know it's water--

868
00:30:44,506 --> 00:30:45,606
we know it's liquid because

869
00:30:45,674 --> 00:30:47,308
you see a little bubble

870
00:30:47,409 --> 00:30:48,509
moving around inside of

871
00:30:48,577 --> 00:30:53,881
this little droplet of water.

872
00:30:53,949 --> 00:30:55,216
>> The amazing thing about

873
00:30:55,317 --> 00:30:57,118
this discovery is the age

874
00:30:57,152 --> 00:30:59,320
of the water.

875
00:30:59,421 --> 00:31:00,688
>> You can date this by several

876
00:31:00,756 --> 00:31:03,124
different dating techniques.

877
00:31:03,158 --> 00:31:04,225
The salt itself is

878
00:31:04,293 --> 00:31:05,860
4.5 billion years old.

879
00:31:05,961 --> 00:31:06,794
The water inside has to be

880
00:31:06,862 --> 00:31:08,496
at least that old,

881
00:31:08,597 --> 00:31:10,798
if not even older.

882
00:31:10,866 --> 00:31:13,067
There's no question about it.

883
00:31:13,135 --> 00:31:14,869
And so this water is at least

884
00:31:14,937 --> 00:31:17,572
as old as the solar system.

885
00:31:17,606 --> 00:31:19,707
>> Here is visible evidence

886
00:31:19,775 --> 00:31:21,876
that water existed in space

887
00:31:21,977 --> 00:31:25,513
when the Earth first formed.

888
00:31:25,614 --> 00:31:28,149
And Zolensky is convinced

889
00:31:28,216 --> 00:31:29,617
that meteorites then brought

890
00:31:29,718 --> 00:31:33,621
the water to Earth.

891
00:31:33,722 --> 00:31:34,855
>> And so it's looking

892
00:31:34,890 --> 00:31:35,890
more and more like the water

893
00:31:35,958 --> 00:31:38,492
arrived drop by drop in rocks

894
00:31:38,527 --> 00:31:40,962
like this meteorite here,

895
00:31:40,996 --> 00:31:42,697
landing over the course

896
00:31:42,731 --> 00:31:45,866
of billions of years.

897
00:31:45,901 --> 00:31:46,968
You have lots of material

898
00:31:47,002 --> 00:31:48,269
coming in every day

899
00:31:48,337 --> 00:31:49,337
and smacking into the Earth

900
00:31:49,371 --> 00:31:50,705
and depositing a little bit

901
00:31:50,806 --> 00:31:53,441
of water, a few drops at a time.

902
00:31:56,345 --> 00:31:57,612
>> The scale of the meteorite

903
00:31:57,646 --> 00:31:58,980
bombardment needed to fill

904
00:31:59,081 --> 00:32:00,648
the oceans with water is

905
00:32:00,716 --> 00:32:04,819
almost impossible to comprehend.

906
00:32:04,920 --> 00:32:07,254
But scientists believe

907
00:32:07,289 --> 00:32:09,190
that over billions of years,

908
00:32:09,257 --> 00:32:10,358
there were easily enough

909
00:32:10,425 --> 00:32:11,892
meteorites crashing into

910
00:32:11,927 --> 00:32:13,260
the Earth to account for

911
00:32:13,328 --> 00:32:19,266
all the water on the planet.

912
00:32:19,368 --> 00:32:20,468
>> Gradually those rocks

913
00:32:20,535 --> 00:32:21,702
were sweating water,

914
00:32:21,737 --> 00:32:23,704
building up first shallow seas

915
00:32:23,739 --> 00:32:24,705
here and there.

916
00:32:24,740 --> 00:32:25,840
They'd grow to be giant oceans.

917
00:32:32,814 --> 00:32:35,282
So you go from this to this.

918
00:32:38,120 --> 00:32:40,454
>> Once Earth had land masses

919
00:32:40,522 --> 00:32:42,556
and water, the stage was set

920
00:32:42,658 --> 00:32:45,860
for the development of life,

921
00:32:45,861 --> 00:32:48,362
the next phase in the evolution

922
00:32:48,430 --> 00:32:51,132
of the Earth.

923
00:32:51,166 --> 00:32:52,900
Life is an essential element

924
00:32:52,968 --> 00:32:54,702
in Earth's geology.

925
00:32:54,803 --> 00:32:57,338
Without life, sedimentary rocks

926
00:32:57,372 --> 00:32:58,973
like chalk and limestone

927
00:32:59,007 --> 00:33:01,509
would not exist.

928
00:33:01,543 --> 00:33:02,910
Without life, there would be

929
00:33:02,978 --> 00:33:07,148
no coal, oil, or gas.

930
00:33:07,182 --> 00:33:08,916
Life has shaped the Earth

931
00:33:08,984 --> 00:33:11,919
in profound ways.

932
00:33:11,987 --> 00:33:13,521
But finding the origin of life

933
00:33:13,555 --> 00:33:14,922
has challenged scientists

934
00:33:14,956 --> 00:33:18,793
for hundreds of years.

935
00:33:18,827 --> 00:33:22,563
Now there's a new explanation.

936
00:33:22,631 --> 00:33:23,898
It comes from evidence found

937
00:33:23,999 --> 00:33:25,566
at Allende in the desert

938
00:33:25,634 --> 00:33:29,003
landscape of northern Mexico.

939
00:33:29,104 --> 00:33:30,438
At about 1 a.m.

940
00:33:30,472 --> 00:33:32,907
On February 8, 1969,

941
00:33:32,974 --> 00:33:36,610
night suddenly turned into day.

942
00:33:36,645 --> 00:33:38,813
>> A large fireball was seen

943
00:33:38,814 --> 00:33:40,548
traveling from the south

944
00:33:40,615 --> 00:33:43,818
northwards over northern Mexico.

945
00:33:43,819 --> 00:33:45,352
And this big flash

946
00:33:45,387 --> 00:33:46,654
and this fireball was caused

947
00:33:46,722 --> 00:33:49,090
by a really large meteorite.

948
00:33:49,124 --> 00:33:50,124
It was probably about the size

949
00:33:50,192 --> 00:33:51,826
of a car. And it entered the top

950
00:33:51,927 --> 00:33:53,094
of the Earth's atmosphere

951
00:33:53,195 --> 00:33:56,097
at about 36,000 miles an hour.

952
00:33:56,198 --> 00:33:57,732
>> As it plunged through

953
00:33:57,833 --> 00:33:59,166
the atmosphere, the meteorite

954
00:33:59,201 --> 00:34:00,601
broke up into thousands

955
00:34:00,669 --> 00:34:02,837
of fragments.

956
00:34:05,574 --> 00:34:07,108
>> There was no crater left

957
00:34:07,175 --> 00:34:08,576
by the Allende meteorite.

958
00:34:08,643 --> 00:34:09,677
So it fell as a shower

959
00:34:09,745 --> 00:34:11,946
of stones, the largest of which

960
00:34:12,013 --> 00:34:13,447
was reported to be about

961
00:34:13,482 --> 00:34:16,217
the size of a beach ball.

962
00:34:16,284 --> 00:34:17,384
The stones are found in--

963
00:34:17,486 --> 00:34:18,886
we call it a strewn field,

964
00:34:18,920 --> 00:34:20,521
and I's an area about 30 miles

965
00:34:20,589 --> 00:34:22,256
by 5 miles wide.

966
00:34:22,324 --> 00:34:23,257
And we are here, right in

967
00:34:23,325 --> 00:34:25,426
the middle of that strewn field.

968
00:34:27,696 --> 00:34:29,063
>> Because the meteorite

969
00:34:29,164 --> 00:34:30,898
fragmented into so many pieces,

970
00:34:30,966 --> 00:34:32,333
geologists had to search

971
00:34:32,400 --> 00:34:35,936
a huge area to find samples.

972
00:34:38,940 --> 00:34:40,808
>> Now I actually have a smaller

973
00:34:40,876 --> 00:34:42,076
one of the stones here.

974
00:34:42,144 --> 00:34:43,077
You can see it's about

975
00:34:43,145 --> 00:34:44,712
the size of a plum.

976
00:34:44,813 --> 00:34:45,946
It's one of the most primitive

977
00:34:45,981 --> 00:34:47,248
type of meteorites.

978
00:34:47,315 --> 00:34:48,582
This means that since it formed

979
00:34:48,617 --> 00:34:50,251
at the very earliest stages of

980
00:34:50,352 --> 00:34:52,153
solar system formation, really

981
00:34:52,254 --> 00:34:54,688
not much has happened to it.

982
00:34:54,723 --> 00:34:56,056
>> When they analyzed samples

983
00:34:56,091 --> 00:34:58,058
from Allende, geologists made

984
00:34:58,093 --> 00:35:00,361
a groundbreaking discovery.

985
00:35:00,428 --> 00:35:02,997
The meteorite contained

986
00:35:03,064 --> 00:35:05,232
tiny amounts of chemicals

987
00:35:05,267 --> 00:35:08,335
called amino acids.

988
00:35:08,370 --> 00:35:09,537
>> Amino acids are terribly

989
00:35:09,638 --> 00:35:11,138
important constituents

990
00:35:11,173 --> 00:35:13,174
of things like proteins,

991
00:35:13,275 --> 00:35:14,642
and amino acids really are

992
00:35:14,709 --> 00:35:15,709
sort of like the chemical

993
00:35:15,811 --> 00:35:17,645
building blocks for life.

994
00:35:17,712 --> 00:35:19,814
So to find these amino acids,

995
00:35:19,881 --> 00:35:20,981
these molecules within

996
00:35:21,082 --> 00:35:22,449
the meteorite was a really

997
00:35:22,551 --> 00:35:25,152
exciting discovery.

998
00:35:25,187 --> 00:35:26,787
>> Every living thing on Earth,

999
00:35:26,822 --> 00:35:28,522
plant or animal, contains

1000
00:35:28,557 --> 00:35:30,991
amino acids, and life could not

1001
00:35:31,092 --> 00:35:33,894
exist without them.

1002
00:35:33,929 --> 00:35:35,462
Until they were found

1003
00:35:35,564 --> 00:35:37,364
in the Allende meteorite,

1004
00:35:37,432 --> 00:35:38,566
scientists believed that

1005
00:35:38,633 --> 00:35:40,067
amino acids were first made

1006
00:35:40,101 --> 00:35:41,569
by chemical reactions

1007
00:35:41,636 --> 00:35:45,539
on the surface of the Earth.

1008
00:35:45,574 --> 00:35:47,474
>> People thought that maybe

1009
00:35:47,542 --> 00:35:48,809
life had started on Earth

1010
00:35:48,844 --> 00:35:51,478
in these sorts of warm pools,

1011
00:35:51,546 --> 00:35:52,479
maybe, you know,

1012
00:35:52,547 --> 00:35:53,547
a few hundred million years

1013
00:35:53,615 --> 00:35:55,282
after Earth actually formed,

1014
00:35:55,350 --> 00:35:57,384
or possibly through lightning

1015
00:35:57,452 --> 00:35:58,919
causing chemical reactions

1016
00:35:58,987 --> 00:36:01,088
in the early atmosphere.

1017
00:36:02,427 --> 00:36:03,628
There was a few theories

1018
00:36:03,646 --> 00:36:04,914
as to how life may have started

1019
00:36:04,976 --> 00:36:06,410
on Earth prior to the discovery

1020
00:36:06,478 --> 00:36:09,680
of amino acids in meteorites.

1021
00:36:11,410 --> 00:36:13,478
>> Since Allende, amino acids

1022
00:36:13,533 --> 00:36:15,034
have been found in hundreds

1023
00:36:15,038 --> 00:36:17,373
of other meteorites.

1024
00:36:17,474 --> 00:36:18,908
Their discovery has

1025
00:36:18,942 --> 00:36:20,543
revolutionized ideas about

1026
00:36:20,577 --> 00:36:24,213
the origin of life on Earth.

1027
00:36:24,281 --> 00:36:26,182
Scientists now believe

1028
00:36:26,216 --> 00:36:27,850
that the building blocks of life

1029
00:36:27,918 --> 00:36:30,753
originally came from space.

1030
00:36:30,854 --> 00:36:34,023
Meteorites containing amino

1031
00:36:34,090 --> 00:36:35,825
acids have bombarded Earth

1032
00:36:35,859 --> 00:36:37,927
ever since the planet formed,

1033
00:36:38,028 --> 00:36:39,728
and it was these amino acids

1034
00:36:39,763 --> 00:36:41,130
which were the starting point

1035
00:36:41,231 --> 00:36:44,500
for all life.

1036
00:36:44,568 --> 00:36:45,568
Hunting for the origin

1037
00:36:45,669 --> 00:36:47,102
of Earth's water and life,

1038
00:36:47,137 --> 00:36:48,771
the investigation has revealed

1039
00:36:48,839 --> 00:36:50,139
that the water on Earth

1040
00:36:50,207 --> 00:36:53,042
arrived here inside meteorites,

1041
00:36:53,143 --> 00:36:54,944
and meteorites also brought

1042
00:36:55,045 --> 00:36:56,912
amino acids,he building blocks

1043
00:36:57,013 --> 00:37:00,516
of life, to Earth from space.

1044
00:37:00,550 --> 00:37:03,185
Scientists now need one more

1045
00:37:03,253 --> 00:37:05,187
piece of the puzzle to explain

1046
00:37:05,255 --> 00:37:06,989
the final stage in Earth's

1047
00:37:07,023 --> 00:37:09,291
journey from particles

1048
00:37:09,392 --> 00:37:11,927
in the solar dust cloud

1049
00:37:11,995 --> 00:37:13,896
to a planet where life itself

1050
00:37:13,930 --> 00:37:15,464
builds Earth's geological

1051
00:37:15,532 --> 00:37:17,666
features.

1052
00:37:20,554 --> 00:37:22,864
>> 4.5 billion years ago,

1053
00:37:22,909 --> 00:37:23,909
Earth formed out of

1054
00:37:23,977 --> 00:37:26,279
the solar dust cloud.

1055
00:37:26,346 --> 00:37:27,647
200 million years later,

1056
00:37:27,748 --> 00:37:29,081
the first continents and oceans

1057
00:37:29,182 --> 00:37:30,916
were developing.

1058
00:37:32,919 --> 00:37:34,186
Meteorites brought water

1059
00:37:34,254 --> 00:37:35,655
and amino acids,

1060
00:37:35,722 --> 00:37:37,156
the building blocks of life,

1061
00:37:37,190 --> 00:37:40,092
to the surface of the planet.

1062
00:37:40,160 --> 00:37:42,161
The investigation now moves

1063
00:37:42,195 --> 00:37:43,462
forward to the period

1064
00:37:43,530 --> 00:37:47,566
3.5 billion years ago.

1065
00:37:47,668 --> 00:37:49,001
New forms of life were about

1066
00:37:49,102 --> 00:37:50,836
to emerge, which by their very

1067
00:37:50,937 --> 00:37:52,104
existence, would create

1068
00:37:52,205 --> 00:37:55,107
new kinds of rocks.

1069
00:37:55,208 --> 00:37:56,442
But life as we know it

1070
00:37:56,476 --> 00:37:58,744
needs oxygen, and 3.5 billion

1071
00:37:58,845 --> 00:38:00,112
years ago, there was

1072
00:38:00,180 --> 00:38:04,650
no oxygen on Earth.

1073
00:38:04,751 --> 00:38:06,285
At the time, the atmosphere

1074
00:38:06,353 --> 00:38:08,854
was deadly poisonous.

1075
00:38:08,922 --> 00:38:10,656
Volcanic eruptions filled

1076
00:38:10,757 --> 00:38:12,291
the air with a choking mixture

1077
00:38:12,359 --> 00:38:13,926
of sulfur, methane,

1078
00:38:13,994 --> 00:38:15,561
carbon dioxide,

1079
00:38:15,595 --> 00:38:18,397
and sulfuric acid.

1080
00:38:18,498 --> 00:38:20,299
But primitive life forms

1081
00:38:20,367 --> 00:38:23,102
did exist.

1082
00:38:23,136 --> 00:38:24,403
The fossilized remains

1083
00:38:24,471 --> 00:38:26,472
of strange coral-like structures

1084
00:38:26,506 --> 00:38:27,773
have been found in rocks

1085
00:38:27,841 --> 00:38:30,009
more than 3 billion years old

1086
00:38:30,043 --> 00:38:32,678
in many parts of the world.

1087
00:38:32,779 --> 00:38:34,780
They are called stromatolites,

1088
00:38:34,848 --> 00:38:35,915
and they are a clue

1089
00:38:35,949 --> 00:38:37,149
as to how the atmosphere

1090
00:38:37,217 --> 00:38:40,052
filled with oxygen.

1091
00:38:40,120 --> 00:38:41,320
Living stromatolites

1092
00:38:41,421 --> 00:38:43,556
are incredibly rare.

1093
00:38:43,590 --> 00:38:44,790
One of the few places on Earth

1094
00:38:44,858 --> 00:38:46,025
where they can be found

1095
00:38:46,059 --> 00:38:47,059
is in another part

1096
00:38:47,127 --> 00:38:49,962
of the northern Mexican desert.

1097
00:38:52,766 --> 00:38:54,133
This is the high valley

1098
00:38:54,201 --> 00:38:56,869
of Cuatro Cienegas.

1099
00:38:56,937 --> 00:38:58,304
>> You might think that this is

1100
00:38:58,338 --> 00:38:59,505
just any old desert,

1101
00:38:59,573 --> 00:39:00,506
but it's not.

1102
00:39:00,607 --> 00:39:02,708
This is a very special place.

1103
00:39:02,709 --> 00:39:04,143
Because of a particular way

1104
00:39:04,211 --> 00:39:06,579
the chemistry is in this valley,

1105
00:39:06,613 --> 00:39:08,147
it's unlike any other place

1106
00:39:08,248 --> 00:39:10,616
on the planet.

1107
00:39:14,621 --> 00:39:16,322
>> The pool is like

1108
00:39:16,423 --> 00:39:19,258
a time-capsule laboratory.

1109
00:39:19,326 --> 00:39:21,861
By examining the modern

1110
00:39:21,895 --> 00:39:23,596
stromatolites, scientists

1111
00:39:23,697 --> 00:39:25,431
can work out how they were made

1112
00:39:25,499 --> 00:39:29,068
more than 3 billion years ago.

1113
00:39:29,136 --> 00:39:30,069
>> What's interesting

1114
00:39:30,170 --> 00:39:31,704
about Cuatro Cienegas is that

1115
00:39:31,805 --> 00:39:35,074
this is almost like a proxy

1116
00:39:35,142 --> 00:39:36,709
to right before the world

1117
00:39:36,810 --> 00:39:38,544
had a lot of oxygen in it,

1118
00:39:38,612 --> 00:39:40,246
and the place was dominated,

1119
00:39:40,347 --> 00:39:41,447
our Earth was dominated

1120
00:39:41,515 --> 00:39:44,617
by microbial life.

1121
00:39:44,684 --> 00:39:46,452
>> Siefert has discovered

1122
00:39:46,520 --> 00:39:47,720
that the stromatolites

1123
00:39:47,788 --> 00:39:49,522
are made by billions of microbes

1124
00:39:49,623 --> 00:39:52,625
called cyanobacteria.

1125
00:39:52,726 --> 00:39:53,626
>> These right here

1126
00:39:53,727 --> 00:39:54,960
are the stromatolites that

1127
00:39:54,995 --> 00:39:56,695
are here at Cuatro Cienegas.

1128
00:39:56,730 --> 00:39:58,164
I have a piece of it here.

1129
00:39:58,265 --> 00:39:59,465
And if you can see

1130
00:39:59,533 --> 00:40:01,867
this blue-green rim right here,

1131
00:40:01,902 --> 00:40:03,536
this is millions and millions

1132
00:40:03,637 --> 00:40:05,171
of cyanobacteria.

1133
00:40:05,238 --> 00:40:07,440
>> These bacteria were to change

1134
00:40:07,507 --> 00:40:09,909
the course of Earth history

1135
00:40:09,976 --> 00:40:12,545
because of one unique feature--

1136
00:40:12,646 --> 00:40:16,248
they produce oxygen.

1137
00:40:16,283 --> 00:40:17,550
>> Here at this pond,

1138
00:40:17,651 --> 00:40:18,818
we can actually see them

1139
00:40:18,919 --> 00:40:19,985
doing their job. We can

1140
00:40:20,020 --> 00:40:22,087
see them making that oxygen.

1141
00:40:22,155 --> 00:40:23,989
So when I get in the water

1142
00:40:24,090 --> 00:40:25,191
and I actually go up

1143
00:40:25,292 --> 00:40:26,459
to up to one of these

1144
00:40:26,526 --> 00:40:28,994
cyanobacterial mats...

1145
00:40:29,095 --> 00:40:31,096
If I look very closely,

1146
00:40:31,198 --> 00:40:32,264
all of the community

1147
00:40:32,299 --> 00:40:33,632
is making oxygen,

1148
00:40:33,667 --> 00:40:34,967
and as that oxygen collects

1149
00:40:35,068 --> 00:40:36,335
in that mat, it produces

1150
00:40:36,436 --> 00:40:37,736
a little air bubble, and you

1151
00:40:37,804 --> 00:40:38,904
can watch that air bubble

1152
00:40:38,972 --> 00:40:40,439
just transfer to the top,

1153
00:40:40,507 --> 00:40:41,707
and that's actually when oxygen

1154
00:40:41,775 --> 00:40:42,808
is being released

1155
00:40:42,876 --> 00:40:44,710
to the atmosphere.

1156
00:40:48,615 --> 00:40:51,317
>> 3.5 billion years ago,

1157
00:40:51,351 --> 00:40:53,185
oxygen was deadly poisonous

1158
00:40:53,253 --> 00:40:55,421
to other early life forms

1159
00:40:55,455 --> 00:40:56,722
which used sulfur

1160
00:40:56,823 --> 00:40:58,791
to obtain energy.

1161
00:40:58,825 --> 00:41:00,259
>> Cyanobacteria developed

1162
00:41:00,360 --> 00:41:02,962
a little molecular machine that

1163
00:41:02,996 --> 00:41:05,431
could actually take sunlight

1164
00:41:05,465 --> 00:41:07,633
and take water, and they made

1165
00:41:07,701 --> 00:41:10,436
a byproduct that was oxygen.

1166
00:41:10,537 --> 00:41:12,004
Well, on this planet back then,

1167
00:41:12,105 --> 00:41:13,005
none of the life

1168
00:41:13,106 --> 00:41:14,707
was used to oxygen.

1169
00:41:14,741 --> 00:41:16,509
And it's at that point

1170
00:41:16,543 --> 00:41:17,910
in life's history,

1171
00:41:18,011 --> 00:41:19,011
when they began making

1172
00:41:19,079 --> 00:41:20,446
excess oxygen that got

1173
00:41:20,514 --> 00:41:21,714
into the atmosphere,

1174
00:41:21,815 --> 00:41:23,282
our whole world changed

1175
00:41:23,383 --> 00:41:25,551
in the way it worked.

1176
00:41:25,619 --> 00:41:27,653
>> Over geological time,

1177
00:41:27,721 --> 00:41:29,355
there were enough cyanobacteria

1178
00:41:29,456 --> 00:41:31,090
to produce trillions of tons

1179
00:41:31,157 --> 00:41:33,292
of oxygen, creating

1180
00:41:33,360 --> 00:41:36,896
the atmosphere we breathe today.

1181
00:41:36,930 --> 00:41:38,931
And they were responsible

1182
00:41:38,999 --> 00:41:40,533
for changing the way

1183
00:41:40,600 --> 00:41:44,403
all life evolved.

1184
00:41:44,437 --> 00:41:45,604
>> From an evolutionary

1185
00:41:45,705 --> 00:41:47,606
standpoint on planet Earth,

1186
00:41:47,674 --> 00:41:49,808
we are where we are

1187
00:41:49,876 --> 00:41:51,710
because of cyanobacteria

1188
00:41:51,778 --> 00:41:53,078
and the fact that they managed

1189
00:41:53,179 --> 00:41:54,713
to fill our atmosphere

1190
00:41:54,781 --> 00:41:57,349
full of oxygen, because

1191
00:41:57,450 --> 00:41:59,418
unless we'd had that gas,

1192
00:41:59,452 --> 00:42:00,719
we wouldn't have the complex

1193
00:42:00,787 --> 00:42:02,354
organisms that we have

1194
00:42:02,422 --> 00:42:04,156
on the planet. You and I

1195
00:42:04,190 --> 00:42:06,725
wouldn't be here today.

1196
00:42:06,826 --> 00:42:08,360
>> Once the atmosphere

1197
00:42:08,428 --> 00:42:10,362
began filling with oxygen,

1198
00:42:10,430 --> 00:42:11,697
the stage was set

1199
00:42:11,731 --> 00:42:12,898
for the evolution of all

1200
00:42:12,999 --> 00:42:15,467
plant and animal life.

1201
00:42:15,535 --> 00:42:18,003
The impact on Earth's geology

1202
00:42:18,071 --> 00:42:20,539
was profound.

1203
00:42:20,607 --> 00:42:22,441
Over hundreds of millions

1204
00:42:22,542 --> 00:42:24,810
of years, decaying plant matter

1205
00:42:24,878 --> 00:42:26,645
from tropical forests built up

1206
00:42:26,713 --> 00:42:28,280
compressed layers, which

1207
00:42:28,381 --> 00:42:30,149
eventually formed all the coal,

1208
00:42:30,183 --> 00:42:31,984
oil, and gas deposits

1209
00:42:32,018 --> 00:42:34,820
on the planet.

1210
00:42:34,921 --> 00:42:36,155
Sedimentary rocks,

1211
00:42:36,189 --> 00:42:37,823
like limestone and chalk,

1212
00:42:37,891 --> 00:42:39,258
are made largely from

1213
00:42:39,292 --> 00:42:41,160
the skeletons of marine animals

1214
00:42:41,194 --> 00:42:42,561
which accumulated at the bottom

1215
00:42:42,662 --> 00:42:45,798
of shallow seas.

1216
00:42:45,832 --> 00:42:48,367
Without life, Earth's geology

1217
00:42:48,468 --> 00:42:52,838
would be very different.

1218
00:42:52,939 --> 00:42:54,573
The investigation into the birth

1219
00:42:54,641 --> 00:42:56,008
of the Earth has uncovered

1220
00:42:56,109 --> 00:42:57,543
evidence revealing the secrets

1221
00:42:57,577 --> 00:43:00,546
of Earth's development.

1222
00:43:00,580 --> 00:43:02,848
Experiments on salt crystals

1223
00:43:02,916 --> 00:43:04,917
in space reveal that the Earth

1224
00:43:04,951 --> 00:43:06,285
began to form when mineral

1225
00:43:06,353 --> 00:43:07,853
grains in the solar dust cloud

1226
00:43:07,921 --> 00:43:10,756
stuck together.

1227
00:43:10,824 --> 00:43:12,124
Evidence from meteorites

1228
00:43:12,225 --> 00:43:13,559
proves that Earth first formed

1229
00:43:13,660 --> 00:43:18,564
4.567 billion years ago.

1230
00:43:18,665 --> 00:43:20,566
The oldest rocks in the world

1231
00:43:20,667 --> 00:43:21,834
are evidence that continents

1232
00:43:21,935 --> 00:43:23,035
and oceans were forming

1233
00:43:23,136 --> 00:43:25,671
4.28 billion years ago,

1234
00:43:25,772 --> 00:43:26,672
much earlier than

1235
00:43:26,740 --> 00:43:29,208
previously thought.

1236
00:43:29,275 --> 00:43:30,776
Liquid water in meteorites

1237
00:43:30,844 --> 00:43:32,411
proves that water was brought

1238
00:43:32,479 --> 00:43:33,779
to Earth during billions of

1239
00:43:33,847 --> 00:43:38,017
years of meteorite bombardment.

1240
00:43:38,051 --> 00:43:40,686
3.5 billion years ago,

1241
00:43:40,754 --> 00:43:42,321
a billion years after it first

1242
00:43:42,389 --> 00:43:43,656
began to grow out of

1243
00:43:43,690 --> 00:43:45,190
the solar dust cloud,

1244
00:43:45,225 --> 00:43:47,026
Earth had continents, oceans,

1245
00:43:47,060 --> 00:43:48,594
primitive life forms,

1246
00:43:48,695 --> 00:43:51,397
and oxygen.

1247
00:43:51,464 --> 00:43:52,498
The birth of the Earth

1248
00:43:52,599 --> 00:43:54,867
was complete, a new canvas

1249
00:43:54,968 --> 00:43:56,502
on which billions of years

1250
00:43:56,536 --> 00:43:58,404
of geological processes

1251
00:43:58,471 --> 00:44:00,239
could mold the planet

1252
00:44:00,306 --> 00:44:02,975
we inhabit today.

1253
00:44:03,075 --> 00:44:06,575
== Sync, corrected by elderman ==
== for www.MY-SUBS.com ==