All language subtitles for through.the.wormhole.s01e05.how.did.we.get.here.hdtv.xvid-momentum

Earth teems with life.

But billions of years ago,

our planet was just
a ball of molten rock.

Did the first Earthlings rise

from a chemical soup bubbling
in a primordial pond?

Or did the seeds of life
crash down from outer space?

Now, at last,
science may be on the cusp

of solving
that most enduring mystery --

How did we get here?

Space, time, life itself.

The secrets of the cosmos lie
through the wormhole.

♪ Through the Wormhole 1x05 ♪
How Did We Get Here?
Original air date on July 7, 2010

-- sync, corrected by elderman --
-- for www.Addic7ed.Com --

Life is full of mysteries,

but the most compelling mystery
is life itself.

The ancient Greeks believed
the gods shaped man from clay.

The Vikings tell
of two great continents,

one made of fire, one of ice.

When they met, sparks flew,

and the first living beings
were born.

Scientists are still trying to
solve this age-old conundrum --

how simple chemicals

were somehow transformed
into living molecules,

molecules that eventually
evolved into you and me.

But the answers may at long last
be close at hand,

and more surprising than
we could have ever imagined.

As a kid, I used to go around
with a magnifying glass,

trying to set things on fire.

Was I being destructive?

I don't think so.

I was seeing what I could create
with the power of the sun.

There was something magic to me
about that spark.

Is this what happened on Earth
billions of years ago?

Did a spark
turn inanimate matter

into something that can grow,
reproduce, and evolve --

something we would define
as alive?

It's a puzzle

that science has been struggling
to piece together.

We have a very good theory
of life's evolution,

but we have no agreed theory
of life's origin.

We don't know how a mix
of nonliving chemicals

turns itself
into a living thing.

That's a very good question.

Because no one's actually
experimentally converted

the nonliving into living,

we don't know precisely
what we need.

It's a question
that may never find an answer.

But the scientists who dare
to probe our moment of creation

are leading us
on a fascinating journey

to an unexpected destination.

To solve the mystery
of our genesis,

we have to rewind evolution,

go back to the time
and the place

where the first living things
came to be...

...Our solar system
more than 4 billion years ago.

It was a very different place
from the solar system we know.

The sun was a young star,
cooler than it is today.

Earth was much hotter,

having just solidified
from a molten ball of hot rock.

Comets and large meteorites
were whirling all around it.

Fiery impacts were frequent
and often devastating.

It's a period of earth's
geological history

called the "Hadean,"
the age of hell.

Geologist Stephen Mojzsis,
from the University of Colorado,

is traveling back in time
to the Hadean,

trying to discover evidence
of life there.

It's interesting to visualize
what you might see

standing on the surface
of the Hadean Earth

some 4 billion years ago.

The moon would fill the sky

because it was much closer
to the Earth at that time.

But the sky itself
would appear different.

So rather than
a beautiful sky blue,

it must have been red

and blasted by meteors
and comets.

The oceans would also
have looked different

in the Hadean.

They would not be blue
and clear, but dark green,

filled with iron minerals.

To us, it would appear
as an alien planet,

incapable of sustaining life.

But Stephen is convinced

it could have harbored
primitive life,

just like today's
most extreme environments,

where microscopic organisms
find a way to survive.

We know,
looking at our planet today --

whether in the driest desert,
the coldest glacier,

the deepest ocean,
the tallest mountain --

life exists.

Why should we expect otherwise
for the earliest earth?

Paleontologists
look for evidence

of ancient life-forms
fren in rocks.

There are fossils
of sea creatures and plants

going back half a billion years.

But the more primitive,
microscopic life

that existed before that

is much harder to detect,

and finding rocks
that date back to the Hadean

is next to impossible.

Almost all of early earth
is now gone,

buried under lava flows
and oceans.

But a few rare outcrops
of 4-billion-year-old rock

do remain.

Stephen tracked one down

in a remote region
in the heart of Greenland.

The traditional wisdom was
that there could not be a record

of the first half billion years
of earth history.

Instead, what we have found
by careful searches is

that not only is there a record
from this time period,

but the record reveals to us
an eminently habitable world.

The rocks Stephen found
in Greenland

came from an ocean that formed
3.8 billion years ago.

They were peppered with a series
of black dots.

They were lumps
of ancient carbon,

and there was something
very unusual about them.

Carbon comes in two forms --

normal carbon,
called carbon 12,

and a much rarer form
called carbon 13,

or heavy carbon.

Normal geological deposits
of carbon

contain a precise ratio
of carbon 12 to carbon 13,

but not these lumps.

Life does something interesting.

It discriminates
against carbon 13.

So the biological matter
is profoundly enriched

in carbon 12.

In the world's oldest known
sedimentary rocks,

it's very clear.

There's a carbon isotope
signature

of early life.

Stephen can't tell
what the primitive life-form

that left this telltale
signature was like,

but it must have been able to
survive in a brutal environment,

a planet constantly pummeled
by giant space rocks,

a world where
most geologists believe

the deluge of impacts would have
melted huge parts of earth,

boiled its oceans dry,

and sterilized
the entire planet.

Yet Stephen Mojzsis is sure

that somewhere
on this hellish earth...

There was life.

Stephen has developed
a computer simulation

to prove our planet could have
remained hospitable to life

even during the intense
bombing campaign it endured

in the Hadean
4 billion years ago.

Each of these episodes here

is an individual asteroid
or comet

coming into the earth

at the time
of the late heavy bombardment.

We find that impact
melt pools here --

basically lava lakes,

some of which are the size
of the continent of Africa.

But this blue region here,

which represents
cold temperatures,

are areas where liquid water
is still stable.

Even in the intense
bombardment epoch

of the early solar system,

the earth would have remained
a habitable place.

Microbes deep down
in the earth --

or deep in the ocean,

like those that today gather
around volcanic vents --

would have the best chance

of surviving
these devastating blows.

What these bombardments do is
favor organisms

that can find a sanctuary

to ride out the raining storm
of space debris

until the epoch of bombardment
is over

and the whole world
is left for them to colonize.

And we think that happened
on the Earth

about 3.8 billion years ago,
when the bombardment ceased.

Stephen's discovery

may have pinpointed
the time and place

for the origin of life,

but it tells us nothing
about how life actually started.

To do that, scientists
must re-create early earth

in their labs

and try to catch a glimpse
of that first magical spark.

Planet Earth,
4 1/2 billion years ago.

If we stepped on its surface,

molten lava would incinerate us
immediately.

One breath of its atmosphere
would kill us.

How could life have formed

in this bubbling,
poisonous hell?

In 1953,

two intrepid chemists
try to answer this question.

Stanley Miller and Harold Urey
designed an experiment

to simulate our planet
soon after its birth.

The results would turn out to be
so groundbreaking

that the apparatus
has been preserved

at the Scripps Institution
in San Diego

by their former student
Dr. Jeffrey Bada.

At first glance,

it looks like just an assortment
of flasks and tubes,

but this was
carefully designed to,

first of all, have a flask

that would represent
an evaporating ocean,

and that was connected
to a flask

that represented the atmosphere.

And in this atmosphere,
you see these electrodes,

and you can apply an electric
discharge to these electrodes

to simulate
atmospheric lighting.

And the products would condense
out of the atmosphere

via this condenser,

run into this tube,

and then back
into the water flask.

Perhaps inspired
by the book of Genesis,

Miller and Urey left their
experiment on the origin of life

running for seven days.

Then, as now, the flask
representing the ocean

slowly started
to turn dark brown,

filling with
a seemingly toxic sludge.

It is a tricky experiment.

If you're not careful,
you can blow it up.

And moreover,
this solution is highly toxic.

It contains large amounts
of hydrogen cyanide.

You'd never want to try
and drink this thing,

or you'd be dead in a second.

But this brown goo also
contains something remarkable.

Among the toxic chemicals
are amino acids.

Amino acids are the basic
building blocks of proteins,

and living things
are built from proteins.

They make up bones,
hair, and skin.

It was a major breakthrough.

Up to this time,

people had tried to make
organic compounds

simulating an early atmosphere,
but they'd always fail.

But it was only
a baby step toward life.

In all these samples saved from
Miller and Urey's experiments,

Jeffrey Bada
has never been able to detect

amino acids joined together
to make proteins.

What you're making
is simple molecules,

what we call monomers.

Life as we know it
is made up of polymers,

complex molecules
that are made up of monomers.

And the challenge still remains

how we can assemble
these simple molecules

into complex molecules
that have a biological function.

That crucial step towards life

may not come
from a bubbling flask in a lab.

Jen Blank is sure of that

because she believes
life needed something else

to get started on earth
and it came from the sky...

At 20,000 miles per hour.

We know that in the early
history of the solar system,

comets were slamming
into the planets,

and maybe this
would have been a vehicle

for delivering prebiotic
materials to the early earth.

Comets --

mountain-sized lumps of ice
and dust circling the sun.

In 1999,

NASA sent a spacecraft
called Stardust

to snag a piece of a comet
and bring it back to earth.

When scientists
analyzed the material,

they discovered
that it contained amino acids,

the building blocks of protein,

the very tissue of life.

One of the big
outstanding questions

is whether or not
organic compounds

coming in on a comet
and slamming into the earth

could survive
the harsh conditions

of that delivery experience.

And so we set out to test this
in the laboratory.

Jen Blank works at SETI,

the Search for Extraterrestrial
Intelligence,

but she's not interested in E.T.
so much as alien molecules.

So she's developed
a computer simulation

to see what happens to them
on impact.

Comets that hit earth head on
are not very promising.

The collision almost completely
incinerates them.

In this movie,
the blue colors are cold,

and as you go toward the red,
it gets hotter and hotter.

And so we expect
the normal impact

to have
the most extreme conditions.

You can see
there's no blue color,

so essentially the material's
all volatilized or vaporized.

But when a comet
makes a glancing blow,

it doesn't incinerate.

It melts and dumps massive
amounts of water and amino acids

on our primeval planet.

This time, we're coming in

at a 15-degree angle
from the horizontal.

Watch the blue,

which will correspond
to the liquid water.

So you can see
a lot of the water's going away,

but you still are retaining
somewhere on the order of 20%

that's being delivered
as liquid water.

But these simulations

only track the temperature
of the comet

as it crashes to earth.

To see what happens
to the amino acids,

Jen needs to get her hands
on some serious firepower.

Here's where
you might want to have

a picture of a gun or something.

This is
the shockwave lab at Caltech.

Its pride and joy --

a 65-foot-long gun
capable of firing projectiles

at over 16,000 miles per hour.

And this is Jen's bullet.

Let's imagine this is a comet.

It's a metal cannister
with a liquid fill volume

that contains water
and dissolved amino acids.

And, in our experiment,

we want to test
the the response of this

to a collision with an earth.

This is actually
a two-stage gun,

and at the far end,

we use gunpowder
to compress gas.

The gunpowder's ignited,

and the compressed air slammed
into the projectile,

and sends it traveling down
the barrel of the gun

at velocities of around 2,000
to 3,000 miles per hour.

This corresponds
to an oblique-angle impact

between a comet
and a rocky Earth.

To simulate this
glancing interplanetary blow,

Jennifer dials down the gun
from its maximum muzzle speed

and prays her cannister
and its payload will survive.

Temperatures in these impacts

would be essentially thousands
of degrees centigrade.

So these are
really extreme conditions.

300 volts. Ready.

Smell that?

That's the gunpowder,
the gunpowder smell.

The capsule is sent
into this larger tank,

which is called
the recovery tank.

It weighs about 2 tons,

and so it really muffles
the collision.

And, really,
at the end of the experiment,

if all things go well,

it looks much the same
as when we first started.

Now Jen breaks open
the bullet capsule

to retrieve its smashed contents
and discover what happened

to this cometary soup
of organic chemicals.

And here's an example with two
different amino acids in it --

glycine, which is
the simplest amino acid,

and proline,
which is another one.

And here's the initial solution.
You can see just two.

Here's an analysis
of the solution afterwards.

The most high-abundance
byproducts

turned out to be
all combinations

of the first two amino acids.

So we were actually very excited

because the reactions
that were occurring

were actually forming larger
biologically relevant molecules.

Jen's high-powered experiment

suggests comets
may have bludgeoned early Earth

one step closer to life.

They helped amino acids
join together,

perhaps even forming
primitive proteins.

We're actually harnessing
the power of the impact

to build larger biologically
relevant molecules.

So this could have been
a dominant source

of the building blocks
that led to the origin of life.

We used to think
our planet was a hellhole

4 billion years ago,

where any spark of life would
have been instantly incinerated.

Now we know the chemicals
of life were inside comets,

raining down on our planet.

And they didn't crash and burn.

They thrived.

But other ingredients of life
are still missing.

At the top of the wanted list
is DNA,

the molecule that carries
our genetic identity.

Now at last, one man
may have cracked the code

to the origins of DNA itself.

It's taken 4 billion years

for life to evolve

into organisms as complex
as you and me.

We're at the tip

of a tall branch
of the tree of life.

Down in the deepest roots
are microbes

whose bodies are
just a single cell.

But each microbe's biology
is just like ours.

No matter how different
it looks,

its identity resides
in a strand of DNA.

Every living organism we know
belongs somewhere on this tree.

But why did the tree of life
grow in the first place?

To solve that mystery,
we have to find the seed.

Scientists don't know much
about this seed,

but they are sure
about one thing.

Every living organism on earth
shares one common feature --

a tough outer layer

that separates it
from the world outside.

Every cell has a membrane.

The first seeds of life
must have had one, too.

Well, we think we need this kind
of primitive cell membrane

to keep the genetic molecules
trapped inside.

You can't just have everything
diffusing around.

You have to have this
compartmentalized.

Jack Szostak
at Harvard Medical School

is on a quest to solve one
of life's biggest mysteries --

how the earliest life-forms
walled themselves in,

defined "me" from "not me."

So, modern cell membranes
are really tough,

they're stable,
they're great barriers,

they allow cells to control
everything that gets in and out.

But that requires a lot of
fancy, highly evolved machinery,

which wasn't around by
definition for the first cells.

So those membranes
had to be really different.

But what might these
primitive skins around the cells

have looked like?

Jack found inspiration...

...In soap bubbles.

So, these are delicate.

They really illustrate the idea

that there's
an encapsulated space.

That was pretty good.

Soap bubbles are made

from molecules
called fatty acids,

primitive chemicals

that Jack thinks were produced
on the primeval Earth

inside hydrothermal geysers.

The right kinds of minerals

could catalyze the assembly
of fatty acids

from simple things like
carbon monoxide, methane, water.

One kind of nice way
that that could happen

is in a hydrothermal-vent
system,

and then they could bubble up
to the surface.

So Jack set about re-creating

the chemistry of a geyser
in his lab

and eventually created
fatty acids.

Now he mixes them
into a primordial chemical soup

made of water, salt,
and amino acids,

and he watches

as a remarkable transformation
takes place.

So, membranes form in sheets,
and they're kind of wavy,

and the edges
are kind of high energy.

So what happens is
they close up on themselves,

and they make
little round structures.

So they're closed structures,
like tiny soap bubbles.

These little dots
are actually hollow bubbles,

less than a thousandth
of an inch across.

This is what the first living
cells may have looked like

4 billion years ago.

Jack may have re-created
the seeds of life

right under his microscope.

But it is impossible
for life to evolve

unless cells can pull off
one crucial task.

They must be able to grow
and divide.

This is how seeds blossom
into flowers,

how a caterpillar
becomes a butterfly,

and how a baby becomes an adult.

Soap bubbles grow and divide

with nothing more
than a puff of air,

so Jack slightly jiggles
the vesicles

and watches
something incredible happen.

The membrane will start
to grow spontaneously.

What we see in the microscope

is that it grows
in a very peculiar way.

The whole initial vesicle turned
into a long, flexible tube.

These fatty-acid membranes

are achieving one of evolution's
most essential jobs --

self-replication.

And they appear to do it
automatically.

To Jack, this is a sure sign

he's getting close
to understanding

how the miracle of life began.

So we have a cycle
of growth and division

that's very much like primitive
cell growth and division.

Jack may very well
have found the recipe

for life's earliest
cell structure,

but to be truly alive,

those cells need
one vital ingredient --

genes.

Genes are the molecular identity

that can pass
from a cell to its copy.

All modern life does this
with a double helix of DNA.

It's the most complex
chemical molecule we know,

made up of tens of billions
of atoms.

DNA controls every detail
of every living thing --

the color of our eyes,

the shape of the leaves
on a tree,

the way even the most simple
bacterium swims.

And every time a cell divides,

it places a copy of its DNA

in both cells
of the new generation.

At the University of Manchester
in England,

chemist John Sutherland

is trying to discover
how DNA came to be --

the key to discovering
how we came to be.

For me, the really
interesting point here

is the transition
between chemistry and biology.

It's always been assumed

that you need to have
an informational molecule.

You can't really have life
unless you can have inheritance,

so you need to have something
which you can inherit

the information stored
in a molecule.

A molecule as complex as DNA

could never have formed
all by itself

in a primordial pond.

But there is
a simpler version of it --

a single-stranded,
informational molecule

called ribonucleic acid,
or RNA.

Scientists studying
the origin of life

have long believed that RNA
might be the precursor of DNA,

a simpler carrier
of life's genetic code.

And so the name of the game,
if you like,

is to make RNA from very, very
simple precursor chemicals,

using simple organic chemistry

under conditions
which could have prevailed

on the early earth.

RNA is a giant molecular string

made up of four different
basic building blocks.

The order in which
these blocks are arranged

forms a genetic code.

When you look at RNA,
as a chemist,

you're in sort of astonishment,
really,

at just what a wonderful
molecule it is.

It's complex.

It's a really beautiful
structure.

And you inevitably wonder --

how on earth
did that structure arise?

How on earth
did chemistry produce it?

RNA's structure looks simple,

but looks can deceive.

Each building block
is actually made of two parts --

a sugar molecule
and a nuclear base.

Chemists found they
could make the nuclear bases,

and so, when they then realized

they could actually make
the sugars,

they just thought, "we must be
able to join them together."

And so they tried
for many years,

but the problem was, chemically,

you just can't join them
together.

For years,
scientists tried and failed

to whip up some RNA

by placing a sugar and a base
in a pot

and heating it up.

But John realized that
the primordial soup metaphor

was too narrow.

Early Earth's kitchen
had more than just a stovetop.

It had an oven, a steamer,
and a freezer.

This is like a pond that's
sitting there for a while,

and then
the temperature goes up,

and the pond
starts to evaporate.

And the residue that's left
after the pond's evaporated

is then heated for a period.

And then it rains again.

And after it rains,
the sun comes out.

So it's a sequence of events,

rather than one static set
of conditions.

So John and his team re-create

the sequence of wetting, drying,
heating, and cooling

that would have taken place
on early Earth.

And incredibly,
for the first time,

these chemists achieve what
none before them ever did --

they create two of the four
basic building blocks of RNA.

Well, now we have to find a way
to make the other two,

and I think we're pretty close
to doing that.

And then we want to
string them together

to make an RNA polymer molecule.

And we've actually
recently found some ways

in which we think
we can string them together.

John may be hot on
the trail of the first genes,

but there's no guarantee

he will ever stumble upon
the answer in a lab.

Now a few renegade scientists
are taking another path

to the origin of life.

They think
the most primitive life-forms

might still be alive
and lurk right under our feet.

All the life we know today,

even the simplest of microbes,
shares the same biology.

We're all from
the same tree of life.

But we know our incredibly
complex biology

could not have been the first
form of life on earth.

What was life like
before the life we know?

Finding that life might help us
understand how we got here,

and the answer could be
right under our noses.

All life so far started
as the same life.

But it's never been clear to me

that you can't have
more than one form of life

on the planet at the same time.

I think it's entirely likely

that we share this planet

with a genuinely alien type
of life --

alien not because
it necessarily came from space,

but because it belongs
to a different tree of life

from you or me.

Remarkably enough,

it turns out
that nobody has really thought

to look for life on earth
as we don't know it.

Paul Davies is

one of the world's
leading cosmologists.

He's the first to admit
he's not a biologist,

but he's not afraid to venture
into their territory

and ask questions
no one else thought to ask.

We don't know how a mix
of nonliving chemicals

turns itself
into a living thing.

We don't even know

whether this is a very likely
sequence of events

or very unlikely
sequence of events.

But let's suppose
it's very likely.

Then shouldn't it have happened
many times over

right here on earth?

Paul's term for
possible homegrown alien life

is "the shadow biosphere."

And he has a plan
for how we might discover it.

We could look at places on earth

where conditions are so extreme,
so harsh,

they're beyond the reach
of life as we know it

to see if there's some hardy
alien type of microorganism

living there.

One of Paul's colleagues,
Felisa Wolfe-Simon,

is looking
for a shadow biosphere

by digging through the mud.

So, the life that we might find
in, let's say, this much mud --

we could have billions
of different microbes

that are as different
as you and I are to a mosquito.

In fact, we are more closely
related to mosquitoes

than they are to each other.

That's how different
these microbes are.

Felisa works
at the U.S. Geological Survey

in Menlo Park, California,

but it's NASA's
astrobiology program

that pays her to study mud.

So, one of
the things I always do

when I go
to a new environment --

regardless of where it is
in the world --

I take samples
to set up a Winogradsky Column.

A Winogradsky Column

is like a potted history
of the earth,

a breeding ground for all kinds
of strange microbes.

You take your sample of mud

and you just fill, say,
a glass jar,

and you put it in the window.

You'll see over time,

beautiful colors evolve
in this Winogradsky Column.

The progression
of colors reveals

distinct types of microbes
that are inhabiting the column.

Every type of microbe needs
specific elements to survive.

Some feed on sunlight,
others on carbon.

More exotic bugs feed on sulfur.

But one mud sample
Felisa took in 2009

revealed bugs stranger than
she could have ever imagined.

It came from a place

that is highly toxic
to almost all life on earth --

Mono Lake in California.

You can't talk about Mono Lake
without being a little wistful.

You feel like
you're on another planet.

It also contains very
interesting compounds.

Of particular interest to me was
very high levels of arsenic.

There's roughly
40,000 times or so

the recommended arsenic
from, say, the E.P.A.

So it seemed to me logically

that it could harbor
potentially the vestiges

of a shadow biosphere.

Felisa was not disappointed

when she dug in the mud
of Mono Lake.

She did, indeed, find bugs

that could survive these
highly toxic doses of arsenic.

And her newfound interest
in this poison

didn't just cause ripples
with her scientific colleagues.

I came home one day,

and I brought
all these books in,

and I put them on my counter.

My husband said, "so, what are
you interested in arsenic for?"

And I said, "well, I'm
interested in how it dissolves,

where you might find it."

And my husband,
a little disturbed, said,

"but you don't study arsenic."

And then I started to giggle

'cause I realized
he was getting a bit nervous.

Arsenic is an effective
poison to most organisms

because it closely resembles
the element phosphorus.

It tricks our cells

into substituting one element
for the other.

Since phosphorus forms
the backbone of DNA,

its effects are devastating.

But not the bugs
that Felisa found.

No matter how big a dose
of arsenic she gave them,

even many times more

than the sky-high levels
in Mono Lake,

the microbes
just kept on growing.

So these are microbes using

what seems to be poison
or toxic substances,

and this biology is thriving.

It can cope with hundreds
of thousands of times

what would be, say,
an okay level of arsenic

for a human to be exposed to.

Could this microbe be
part of the shadow biosphere,

our own homegrown alien life?

Could its rules of biology
be different from ours?

So, perhaps, maybe they use
a similar kind of DNA --

only it's a little different.

Maybe parts of it are different.

Maybe they use
similar proteins to ours,

but maybe they use different
amino acids than we do.

If arsenic atoms

are somehow replacing phosphorus
atoms in these microbes,

then these bugs do not fit
on our tree of life.

They may not look any different
from life as we know it,

but these bugs
could be the descendants

of an entirely separate genesis.

So if we found something

that even did something
a little different,

it could mean
that here on Earth,

there was not
just one tree of life,

but there could be
multiple trees of life.

Humanity has spent an eternity

thinking about the loneliness
of being us.

It would provide for us
an example of something else,

some other form of life
that was also successful.

If we found
those microorganisms,

then bingo.

We could say life on Earth
has happened at least twice.

Two out of two
on one earth-like planet

surely means that the universe
is teeming with life.

It would be inconceivable

life had happened twice
on one earth-like planet

and not at all on all the other
earth-like planets.

If Felisa's bugs

are the offspring of
a second genesis here on Earth,

then life
could be a cosmic norm.

We would not be alone
in the universe.

But that leads us to an even
more intriguing possibility --

life on Earth may not be
from Earth at all.

The scientific quest
to discover the origin of life

has revealed something
totally unexpected...

...There might have been
more than one genesis.

Our planet might harbor not one,
but two or more trees of life,

each growing
from a separate seed.

Where did these seeds come from?

That question is forcing us
to reassess who we really are

because the answer could be
out of this world.

Planetary scientist Ben Weiss

has pieces of another world
in his lab.

They are rocks that have
traveled from Mars to Earth,

and he thinks
microscopic Martians

may have hitched a ride
on some of them.

About a ton of Martian rocks
lands on earth every year,

and over the history
of the solar system,

billions of tons of materials
have been transferred.

So it's possible that we,
in fact, are Martians.

4 billion years ago,

when Earth was being pounded
by meteorites and comets,

so was Mars.

Shrapnel from those impacts

was flying all over
the early solar system.

Scientists have found
one Martian rock

that dates back to those days
of interplanetary violence.

It's called ALH84001.

ALH84001 is a Martian meteorite

that formed
on the surface of Mars

and then was knocked
off the planet.

It wandered around in space,

and it landed on the earth
about 11,000 years ago.

It was found in Antarctica
by some U.S. scientists in 1984.

This rock is very special.

In the 1990s,

the discovery of tiny, wormlike
structures in the rock

turned ALH84001 into
an international celebrity.

The claims that these were
fossilized remains

of Martian microbes
have since been discredited,

but Ben's investigation
of this meteorite

might still offer proof
of life on Mars

because the rock is magnetized.

You see all these little dots,
little features.

That's magnetization
that originated on Mars.

In fact, it's 4-billion-year-old
magnetization.

So that must mean
that there was a magnetic field,

a global magnetic field on Mars
4 billion years ago or earlier.

A global magnetic field
acts like a protective cocoon.

It has kept Earth's atmosphere
safe since day one.

Without a magnetic field,

the planet has no protection
from the solar wind,

an intense stream of particles
from the sun.

Over hundreds of millions
of years,

it can blow a planet's
atmosphere clean away.

Mars has no magnetic field now
and almost no atmosphere.

The magnetization imbedded
in ALH84001 proves

that 4 billion years ago,
Mars had both.

ALH84001 contains some trapped,
we think, atmospheric gases

from early Mars.

The composition of these gases

do not resemble the composition
of the Martian atmosphere today.

But they do resemble

what you might think early Mars
had in its atmosphere.

Even though today
it's cold and dry

and not very hospitable
for life on the surface,

we think in its early days
that it had a climate

which was much more like
the Earth's today.

It was presumably significantly
warmer and wetter.

There might even have been
standing bodies of liquid water

on its surface.

Its atmosphere was thicker.

And it might have been a better
place for life to originate.

Since Mars is
only half the size of Earth,

it would have cooled
from a molten ball of lava

much quicker than Earth.

In other words, Mars could have
harbored life sooner than earth.

And Ben's most recent study
is closing the link

between the biology
of two planets.

He's discovering

that microscopic Martians
could, indeed,

have survived the hot
and bumpy ride on a space rock

from Mars to Earth.

So, what you see here
is a slice of the meteorite.

In fact, on the very outside
of it over here on the left,

there's a little melted zone.

And that's the zone that got
heated to high temperatures

when it passed through
Earth's atmosphere.

But most of the meteorite
was barely heated at all

by passage
through the atmosphere.

As mars was slowly cooling

and losing the ability
to support life,

the last Martians
may have jumped ship

to our warmer, wetter planet.

Organisms could have hitched
a ride on this material

that was being exchanged
between mars and the Earth

that even potentially seeded the
planet on which they landed on.

And there's every reason
to think that, you know,

if there was an origin of life
on Mars billions of years ago,

that it probably made it
to the Earth multiple times.

If Ben is right,

the best place to look
for clues to the origin of life

might be on the surface
of planet that's now dead.

Fossils
of primitive life on Mars

dating back billions of years
could still be there.

Perhaps the next space probe
we send to Mars

will stumble across them,

and we'll be able to study
our long-lost ancestors.

But it's also possible
the first living things on Earth

are still here,
lurking in the shadow biosphere.

You and I are
the latest chapter of a story

that's been unfolding
for billions of years.

How that story begins
is still unknown.

Did comets seed the Earth

with the raw ingredients
of life?

Was Mars our original birthplace

before we jumped
to a new planet?

Or are we the Earth's second
or third incarnation of life?

Aliens might be living among us.

We might all be Martians.

In the end,
the stuff of science fiction

might lead us to a cosmic truth

and answer
that eternal question...

How did we get here?

-- sync, corrected by elderman --
-- for www.Addic7ed.Com --