How the Universe Works (2010–…): Season 5, Episode 6 - Life and Death on the Red Planet - full transcript
Life on Mars went through a series of life impacting events and the first impact may have seeded life on earth by debris from Mars..
3.7 billion years ago,
early life was on the brink
of extinction.
Colossal impacts...
Ferocious climate change...
And total atmospheric collapse
have turned paradise into hell.
But this isn't Earth...
It's Mars...
And this is the violent
history of perhaps
the first life forms
in our solar system.
Could these martians
still exist today?
Could they even be
living among us?
Captions paid for by
discovery communications
scientists suspect that life may
once have thrived on Mars...
That the barren world
we see today
swarmed with martians long ago.
If I had to bet something
incredibly valuable to me...
If I had to bet my car...
On whether or not
there's life on Mars,
or evidence of past life
on Mars,
I'd take that bet.
The building blocks for life
are widespread in the universe,
and early Mars could have been
the perfect place
to pull these
ingredients together.
If you had a recipe book for
everything you need for life,
you'd have things like water,
organic chemistry,
a stable surface,
a thick atmosphere...
Well, Mars had
all of those.
Mars satisfies
every specific requirement
for letting life get started.
Life on Mars
may have been inevitable,
and we've sent a robot army
to hunt for signs of it.
But so far,
it's been elusive.
Our rovers, landers,
and satellites
haven't found life yet,
but they have found evidence
of something extraordinary.
Mars was the victim
of a devastating series
of extinction-level events
that rocked
the red planet to its core...
Leading us to wonder,
if life could have started over
multiple times,
with generation
after generation of martians
rising and falling through
Mars' violent history.
It seems likely
that a first Genesis of life
could have occurred very early
on in Mars' history,
just as soon
as the crust was cool enough
to give it a solid foothold.
The secret to this early life
would have been
a crucial ingredient,
one shared by the young Earth.
Dry, harsh Mars
once had oceans.
For life to get started,
you need some carbon,
an energy source,
it needs nutrients
like nitrogen...
But those are likely to be
present on Mars,
they are present
and widespread on Earth.
The essential requirement
is really the liquid water.
Picture Mars
4.5 billion years ago.
Molten rock has cooled
to form a solid crust.
Water collects on the surface,
forming primitive oceans.
Rain clouds sweep across
the steaming,
volcanic landscape,
and in shallow pools
of water,
the martians
begin to emerge.
But these first aliens
are simpler
than Sci-Fi
would have us believe.
We're probably not talking
about little green men
or women, or whoever.
Walking around on the surface
of Mars, we...
We're talking
about something probably
much, much smaller
and simpler,
single-celled life.
If would look familiar,
it would look just like
bacteria on Earth.
Little, tiny, round,
rod-shaped organisms.
If this generation
of bacterial martian life
really did exist,
it was the first life
to grace our solar system.
Multiplying inside
the rock pools of Mars
long before life
took hold on Earth,
Mars' small size would've
given it a head start.
Because Mars is smaller
than the Earth
it would have cooled
a little bit faster
than we did.
So early on in the life
of the solar system,
Mars may have been
more like Earth
than Earth was at the time.
Let's go back 100 million years
after the sun formed.
The surface of the Earth
is still a molten lake.
But martian life
could be thriving
on the smaller,
cooler world.
But these first martians
won't have long
to enjoy
their time in the sun.
Inescapable death is already
on its way from space...
A cosmic bomb so huge,
it would completely alter
the shape of the planet,
leaving it lopsided,
the northern
hemisphere crushed.
Most planets are round,
and that's just something
you don't really
give much thought to,
but it turns out Mars isn't
as round as it could be.
The Southern hemisphere,
on average,
has a higher elevation
than the northern hemisphere.
So, in other words, if you were
to start on the north pole
and walk all the way
around to the south pole,
you'd be walking uphill,
essentially, the whole time.
So, we call this difference
between the northern
and the Southern hemisphere,
we call this the crustal
dichotomy on Mars,
and it's been one of the biggest
mysteries of the planet,
you know, it's the first thing
that you see about it,
and you say, well, how could
this possibly have happened?
In 2008, scientists mapping
the surface of Mars came up
with an explanation
for the massive dent
in the planet, shown in blue.
This basin, the biggest
in the solar system,
had to be the result
of a massive impact.
Called the Borealis impact,
it blasted out a crater 6500
miles wide and five miles deep,
big enough to swallow
the entire United States
with room to spare.
Something really big happened.
In fact, the entire top half
of the planet
seems to have
practically been blown off.
The only thing that could do
that is a huge collision,
and we're talking a collision
with something the size
of Pluto, perhaps.
You're talking about an impact
that makes
the dinosaur killer impact
65 million years ago look pretty
much like a wet firecracker.
4.5 billion years ago,
the early solar system
is filled
with planetesimals
and protoplanets...
Asteroid-like leftovers
from a planet building process
that created Mars
and the Earth.
One of these
asteroids is huge,
and it's on a direct collision
course with Mars.
Any microscopic martians
have just seconds to live.
If this impact
was happening today
and we were so unlucky
as to be there to witness it,
what you first would have seen
is another moon in the sky...
And then you would've
looked back and seen,
oh, it's getting bigger.
As it came down it would have
filled the entire sky,
from horizon to horizon,
and as it struck,
the top would have still
been well out into space.
The impactor
is 1200 miles across,
the size of Pluto,
and as it hits,
the energy of the impact
shakes Mars to its core.
The entire planet
wobbles like jell-o.
As it came down,
it would have been hitting
into the surface of Mars
as fast as a bullet
out of a gun,
and it would have slammed
into the surface
and sent a shockwave out
that would've been bigger than
any earthquake ever recorded.
It would have been
like a Tsunami of rock
coming out and tossing us
out of the way.
The impact is catastrophic.
It blows nearly half
the planet's surface into space
and turns what crust remains
into a boiling lake of lava.
You can't have
an impact of that scale
without almost melting
the planet.
It's not literally
a planet breaking event,
but it's
a planet melting event,
and it is, it is
the sterilization
of the planet
at that point.
The surface of Mars was molten,
its atmosphere
blown into space,
the oceans boiled away.
If Mars was home
to the first generation of life
in our solar system,
that life didn't
stand a chance.
It would take the surface
of Mars 50 million years
to recover from the impact.
But what sort of planet
will rise from the ashes?
Compelling new evidence suggests
that the conditions for life
may have returned to Mars,
but did life itself
make a comeback?
This impact
was only a blip in time,
and there was possibilities
for life
and the planet to recover.
4.5 billion years ago
an asteroid
the size of Pluto
slammed into the surface
of infant Mars.
It melted the surface
of the planet,
it blew the atmosphere
into space,
and it boiled
away the oceans.
If life had gotten
a foothold on the planet,
that life would have been
completely exterminated.
But some scientists
believe this extinction
could have been brief,
and that life could have
started again from scratch.
One of the wonderful things
to imagine is that
there probably wasn't
a single origin of life.
It's not like
it happened once
and then everything
just went from there.
Maybe there were multiple times
that life got started
and went extinct.
Ten million years
after the Borealis impact
crushed the planet's
northern hemisphere,
Mars has cooled enough
for its surface
to become solid once more.
The planet has some
of the ingredients for life...
The right molecules,
a stable surface,
and an energy source.
But something's missing.
4.49 billion years ago
the surface of Mars was dry,
and without water,
life can't start over
and a second generation
of martian can never arise.
As far as we know life,
water is absolutely,
fundamentally important to life.
2004... NASA's opportunity rover
lands on Mars.
Part of its mission
is to search for evidence
that water returned to Mars
after the Borealis impact.
It's not long before
opportunity
stumbles across something
strange on the surface
of a fossilized sand dune...
Bizarre, round,
metallic rocks.
These rocks are called
blueberries,
and they're an important find
for planetary geologists,
like Jani Radebaugh,
because fossilized
sand dunes also exist on Earth.
And Utah's petrified dunes
are also littered
with blueberries.
This is really exciting
because we've seen the exact
same thing on Mars.
Finding blueberries on Mars
is significant,
because the Borealis impact
melted the planet,
so anything found
on Mars today
must have formed
after the impact.
But crucially,
these nodules of iron oxide
formed deep underground
and in the presence of water.
In order to form one of these
little blueberries,
there needs to be huge
amounts of water
flushing down
through the fossil sand dunes,
and as it does that,
it carries with it all
of the iron oxides
around each sand grain.
And just one tiny,
little one like this...
Now, this is maybe about
an ounce of iron,
maybe a little bit more...
And in order
to get an ounce of iron
to concentrate into
this blueberry,
you need to have
a thousand gallons of water.
Blueberries form
deep inside sandstone.
But over thousands
of years,
wind erosion blows away
the softer rock,
leaving just
the blueberries behind.
If we walk to the edge
of this
pile of blueberries,
we could see
the process by which
they're actually eroding
out of the rock.
The blueberries
right here contain
within this fossil
sandstone layer.
The winds are blowing
in this direction,
down the layers,
and they're actually eroding out
the soft sandstones right here
and leaving behind
very dense iron nodules,
and as they pluck themselves
out of the rock,
they roll down the hill
and they collect...
Right here,
in between layers.
We know we found conditions
just like this on Mars.
We have fossil
sand dune layers,
we also have blueberries
all over the surface,
so we know
the same kinds of things
had to have happened on Mars
that have happened here.
There has to be water
flowing through the rock,
gathering iron,
and then there has to be
a huge amount of wind
to strip away
the fossil sand dunes.
For blueberries to exist
on the surface of Mars today,
the red planet
must have gotten its water
and its atmosphere back after
the catastrophic impact.
With liquid water
on the surface,
the ingredients of life might
have combined, once again,
to create
a second generation of martians.
But where did this water
come from?
The answer is surprising.
It could have been
in the planet itself...
Water is incredibly abundant.
We know that
there's water deep,
deep, deep
in the Earth's mantle,
and so it's entirely
possible that on Mars
there was water so deep
in the planet
that even after this
catastrophe, it came back up.
On the Earth, scientists
diffuse the seismic waves
of earthquakes
to detect
an ocean's worth of water
chemically embedded
in minerals deep underground.
A similar water source
could have been hidden
hundreds of miles below
post-impact Mars,
and volcanoes could have brought
that water back to the surface.
One way for water to get from
deep underneath the surface
to the surface of the planet
would be through
geologic activities...
Volcanoes, for example.
We know that volcanoes spew out
a lot of gasses on Earth,
including water vapor,
and we see
volcanoes on Mars.
Mars is home to the largest
volcanoes
in the solar system.
The biggest of all,
Olympus Mons,
is over three times
taller than mount Everest.
4.49 billion years ago volcanoes
spew lava spiked with water
into the atmosphere
and create ferocious rainstorms
that flood
the surface of Mars.
Over tens of thousands
of years
Mars becomes
a watery world once again
with the perfect conditions
for a second generation
of martians to rise up.
It would seem that
when you have
a massive collision,
like what happened to Mars,
it would be game over
for life.
But there's something
more complicated going on.
Maybe that asteroid impact
kicked off
an entirely new cycle
of life on Mars.
In theory,
four billion years ago,
a second generation of
single-cell bacterial life
arose on Mars,
and for the very first time
there was life
on two planets
in the solar system.
140 million miles away,
life on Earth had just begun,
and thanks to Earth's
stable climate,
it would one day
evolve into us.
But the outlook for Mars
was very different.
Evidence from the Mars
reconnaissance orbiter
suggests an icy apocalypse
was about to strike.
For Mars' second generation,
winter was coming.
Four billion years ago,
the first life
has arisen on Earth,
but on Mars, life may be
starting out for a second time.
It's possible that Mars
had life before Earth did...
It got wiped out...
And then got started again
by rehydrating the planet.
A planetary collision
has blown away Mars'
atmosphere and oceans,
along with any life,
but giant volcanoes have brought
water back to the surface
from deep within the planet.
This could have allowed
for a second generation
of life to rise up.
But these martians are about
to be tested to their limits
by catastrophic
climate change.
2008... NASA's Mars
reconnaissance orbiter
flies high
over the surface of Mars.
Its ground-penetrating
instruments
peer deep below the surface,
aiming to unlock Mars'
geological secrets.
As it scans
near Mars' equator,
the orbiter spots something
that has no right to be there...
A vast,
underground glacier.
One mile thick and three times
the size of Los Angeles,
ice on this scale should
only form at the frigid poles.
The only explanation...
Mars must have been
tipped over
with its equator
tilted away from the sun.
The tilt on Mars' axis
has actually changed
significantly over time,
and in non-systematic ways,
it just happens randomly
that it will start moving,
and so there are some
models that suggest
that Mars has actually been
almost tipped over on its end.
Most planets wobble,
and from time to time,
they wobble so much
they can tip over,
leading to super winters.
If that had happened
here on Earth,
Los Angeles
could become the arctic.
Well, you can imagine something
similar would happen on Mars,
how drastic the change
would be.
You're used to seeing
the sun overhead,
it's very warm,
there's probably liquid water,
and as the planet
starts going this way,
the sun is not gonna rise
as high in the sky.
Eventually you may not see
sunrise for half a year,
and any water that's
there is gonna be frozen solid.
3.9 billion years ago,
Mars is tilting
by as much as 80 degrees.
Winter temperatures drop below
minus 125 degrees Fahrenheit.
As the polar ice sheet spreads
quickly toward the equator,
liquid water is frozen solid,
along with any potential
martians.
The water that drives
the biochemistry of life
freezes inside
the tiny bacteria.
Ice crystals form and puncture
the martian's cell walls
until eventually, they die.
Every 120,000 years
the tilt of Mars changes,
as again and again
the planet's chaotic wobble
flips the martians in and out
of the deep freeze.
Any second generation
of life on Mars...
Is left in tatters.
Meanwhile, on Earth, our ancient
ancestors have it easy.
The Earth's wobble, and its
seasons, stay relatively stable,
and it's all thanks
to our secret weapon...
Our oversized moon.
The interaction
of our planet and the moon
means that the axis of our
rotation is very, very stable.
The seasons return year after
year, century after century,
for billions of years.
Our moon's enormous mass
exerts a huge gravitational pull
on the Earth,
stabilizing the wobble
of our planet
and keeping
our climate in check.
Without the moon,
the early Earth
would have wobbled
just as wildly as Mars,
and our ancestors could have
faced the same icy fate
as the early martians.
Mars doesn't have a big moon,
it has two, little,
tiny moons
that don't really
affect it much.
So if the martians were killed
the first time
by a giant impact,
they may have been killed
a second time
by Mars itself not being
stable and flipping over
and having catastrophic
super winters and super summers,
basically, mega catastrophic
climate change.
On Mars, the outlook for life
seems bleak.
But the brutal conditions
that drive martian life
to the edge of extinction
may also have pushed it
to adapt and evolve.
We know this because on Earth
organisms known as extremophiles
have evolved to live in the most
severe of circumstances,
from boiling,
hydro-thermal vents...
To the deep freeze
of glacial ice.
When the going gets tough,
life seems to get tougher.
Maybe the martian
super winters
gave rise to
a third generation of life...
A super tough army of bugs
able to survive
the harshest
of climate swings.
What we see on Earth
is that life evolves
to occupy
whatever niche it lives in,
and that evolution takes time.
So as the environment changes,
life changes with it.
If there are sudden changes,
then life forms can't cope
with it and many die away.
Those that survive,
they continue on.
3.8 billion years ago
a third generation
of life could have thrived
on the surface of Mars.
Evolved from a handful
of its predecessors
to make it through
Mars' super winters,
it's the toughest
martian life yet.
But, as the super winters end,
the challenges for life
on Mars are set to get worse.
Another extinction-level event
is on the way.
Mars' atmosphere is being ripped
away molecule by molecule.
Could this be the killer punch
that wipes out
the martians for good?
Narrator: Imagine Mars
3.8 billion years ago.
It's a warm, wet world,
and super tough bacterial life
is thriving.
But these martians are not
the planet's first inhabitants.
The first generation
of martian is vaporized
by the huge Borealis impact.
Perhaps life starts over
from scratch,
but endures a series
of extreme climate swings.
Only the toughest martians
make it through.
But another disaster
is about to strike,
and this catastrophe will test
even the strongest martians.
They're about to lose the most
basic ingredient of life...
Liquid water.
You really have to appreciate
how difficult it is
to have liquid water
on the surface of a planet.
We know that life works
so well
when there's
liquid water around.
But you need
just the right balance
of air pressure
and temperature.
Without air pressure
weighing down on it,
liquid water will evaporate from
the surface of a planet,
whatever the temperature.
That air pressure
is generated
by the presence
of an atmosphere.
In a lot of ways that atmosphere
serves as a kind of a lid
stopping down the water
from escaping into space.
It's very important
to have that atmosphere.
3.7 billion years ago,
life on Earth enjoys warm oceans
and a thick atmosphere.
But on Mars,
a third extinction-level event
is gaining momentum.
The atmosphere is slowly
being stripped away,
and Mars' great oceans
are starting to evaporate.
The fate of life
on both planets
now rests on the strength
of their magnetic cores.
It turns out
that the existence
of an atmosphere on Earth may
rely on the magnetic field,
because what
our magnetic field does
is it protects us from
the onslaught of this wind,
of subatomic particles
that the sun is blowing out
all the time.
We call this the solar wind.
And if we didn't
have a magnetic field
to basically catch and deflect
those particles gently,
they would directly slam
into the Earth's atmosphere.
If you think
of the magnetic field
as a windbreaker
from the solar winds,
once we lose that protection,
that planet becomes
very vulnerable.
The Earth's magnetic core
has stayed strong
for 3.45 billion years
as super hot molten iron
churns over and over
within the planet
like a lava lamp.
Churning iron
creates electricity,
which in turn generates
a magnetic field
that rises up around the Earth,
acting like a magnetic shield,
protecting our atmosphere from
the ravages of the solar wind.
3.8 billion years ago
Mars had a molten core
and a magnetic field.
But something caused
its shield to drop.
Did Mars' small molten core
simply get too cold to function?
Or did
something else kickstart
this third great extinction
of martian life?
A new and controversial
theory points the finger
partly at
the ancient Borealis impact.
A giant impact of this scale
can affect a range
of temperatures,
from the hot inner core
to the cooler outer mantle.
4.5 billion years ago
the impact that vaporizes
the first generation
of martian life
also drives heat
into the planet,
increasing the temperatures
in the outer mantle.
The heat inside the planet
evens out,
and the metals
slowly stop churning.
But there's less
of a temperature gradient...
That makes it harder
for this dyno process to,
to drive a strong
magnetic field.
Over hundreds of millions
of years, Mars' magnetic field
shuts down.
When Mars lost its magnetic
field all of a sudden
it was completely
vulnerable to the solar wind.
The solar wind
could break apart
and carry away
the martian atmosphere.
3.7 billion years ago
super tough martian life
faces annihilation.
Bit by bits, the atmosphere
is being swept into space.
The air pressure
is dropping across the planet
and most of Mars' water
has already boiled away.
The chances of survival
without this precious liquid
are remote.
But, for the martians, there's
an even more immediate danger.
With no magnetic field
and no thick atmosphere,
the surface of Mars
feels the full force
of the sun's radiation.
If you're a microbe
on the surface,
you would
have to make do
with very little atmosphere,
no water,
this flood of ultraviolet light
from the sun,
and these particles which are
slamming into you all the time.
The martians are bombarded
by radiation
from the solar wind.
It rips their DNA apart.
Without an atmosphere,
the surface of the planet
is sterilized.
But is this really
the end for martian life?
Life is so tenacious,
it can survive even those
incredible catastrophic changes,
and it may still
be there today.
To survive the radiation,
martian life would have had to
have moved deep underground.
In this protected
subterranean environment
it may also have found
a source of liquid water,
and if that happened,
could the martians
still be there today,
waiting for us to drop in
and say hello?
Since the 1960s
robotic probes and landers
have been searching the surface
of Mars for signs of life.
But have they been looking
in the right places?
The surface of Mars
is a waterless desert
that's bombarded
by harmful radiation.
If a fourth incarnation of
martian life is alive today,
many scientists think it'll
have to be deep underground.
Underneath the surface of Mars
you may have all the conditions
you need for life.
There may be some liquid water
down there,
and you're also protected
from the intense radiation
that you find on the surface.
Scientists are split
on the best underground places
to search for martian life.
But if Jani Radebaugh
were on Mars,
she would head to the nearest
sand dune and start digging.
Here you can see
this is wet sand
just below the surface.
This is the perfect environment
to be able to house life.
Even in the very driest
deserts on Earth,
in between the sand dunes,
in the inter-dunes,
you can find water
percolating up from Springs
that come up from
deep under the ground,
perfect for life
to form and grow.
And if you just keep on
digging...
Down into the bottom
of the inter-dune,
maybe you would reach
the water table.
And if you reach
the water table on Mars,
now you have all the conditions
just right for life.
This is my bet,
this is where I'd go,
right between the dunes.
Digging for martian life
in the desert is one option.
But some scientists
have very different ideas,
and planetary scientist
Nina lanza
would need to pack a rope
and a flashlight for her search.
So if were to go to Mars
to find life,
I would go to a lava tube.
Lava tubes are made
by ancient volcanoes,
the empty leftovers from
underground lava flows.
Today,
they form deep tunnels,
shielded from radiation
and shut off
from the harsh
martian climate.
We've never been
in a lava tube on Mars,
but it is absolutely possible
that there's liquid water.
So, that's an environment where
you could have some moisture,
you could have a little warmth,
you're protected from radiation.
I think that a martian microbe
would be very happy there.
Finding life on Mars
would be a monumental
human accomplishment.
But there is a danger.
By exposing martian
life to life from Earth,
could we unwittingly set off yet
another extinction event?
Humans have been
one of the most effective
extinction mechanisms
of life on Earth.
The interesting
question will be,
will we produce a similar
calamity on Mars?
If humans someday
go to Mars,
then we will be
an invasive species,
and if there is some
martian life
that's hanging on
in some niche,
we could be
their ultimate destroyers.
So we have an ethical
responsibility
to preserve whatever
life may be on Mars.
The problem isn't us,
it's the bugs
in and on our bodies.
The average human has
ten to 20 trillion
bacterial hitchhikers.
If we go to Mars,
we'll be taking our tiny
companions along for the ride,
and any one of those bugs
could turn out to be
a deadly competitor
for martian life.
It's NASA engineer
Moogega Cooper's
job to keep
Mars rovers bug-free.
But keeping astronauts clean,
that's a whole different matter.
We bake our spacecraft hardware
at 110 degrees Celsius
for at least 50 hours
to prevent the contamination
of Mars.
But unlike spacecraft,
we cannot bake humans out.
We will not survive
those temperatures.
Unless we find a way
to keep astronauts bug-free,
exploring Mars with robots
is our best option
for keeping the martians
safe from harm.
But what will happen
when our robots
finally find that life and we
look deep into the workings
of our extraterrestrial
neighbors?
What will the martians
turn out to be like?
Our example where DNA
is the organic molecule
that carries
the information of life...
We don't even know
if that's gonna be
the rulebook in other places.
Finding any evidence
whatsoever on Mars
would help us better understand
what else is possible.
Will the martians
be different than us?
Made from
different materials
and with a different
biochemistry?
Or will they seem
shockingly familiar?
Some scientists think
that the very first martian life
may not have stayed on Mars.
It may have come here.
It's not that
farfetched to think
that life could have
jumped from Mars
or been a back and forth
from Mars to Earth.
If the martians came to Earth,
could they have seeded life
on our planet?
Maybe the martians aren't dead.
Maybe I'm a martian,
maybe you're a martian.
We've sent a robot army to Mars,
and what it's found
is astonishing.
The possibility that life
could have arisen there,
perhaps more than once,
with different generations of
martians emerging from the ashes
of catastrophic
extinction events.
Life could still be sheltering
below the surface of Mars
right now.
But there's another possibility
that's truly astounding...
That martians
aren't just hiding out on Mars,
they're thriving,
right here on Earth.
I might be a martian,
you might be a martian.
We might be from another planet.
We might have already travelled
and lived on two planets
as life forms...
Not as a species, certainly,
but our ancestors may have
come from another planet,
and that is mind blowing.
The idea that our ancestors
could be martians
is a new take on an old theory
called Panspermia.
According to the theory,
life on Earth began
when a space rock
filled with alien bacteria
landed on the Earth
and every living thing
we see today, including us,
evolved from those
cosmic hitchhikers.
The idea of Panspermia
has been around for centuries,
but had a resurgence
when scientists
determined that life on Earth
may go back four billion years,
to the end of a sustained
attack of asteroid showers
known as the late heavy
bombardment.
There are a lot of objects
from the outer solar system...
Comets and asteroids,
all kinds of things...
Coming into
the inner solar system
and slamming
into the planets.
Conventional wisdom
suggests the objects
hitting the Earth at the time
were leftover debris
from the formation
of the solar system.
But a very controversial idea
suggests these space rocks were
actually all pieces of Mars,
thrown off
in the Borealis space impact
when a huge object
blasted into Mars.
The timing links up really well
for the Borealis space impact.
If you calculate
how much debris
that would have been
thrown out into space
and when it would have
had to have happened,
according to the martian
geologic record,
it coincides with
the late heavy bombardment...
It's possible
that the debris
from the Borealis
space in forming impact
might have come to Earth
and rained down on us
and made the late heavy
bombardment,
seeding the Earth with
bacterial spores from Mars.
Now, this is just a hypothesis,
we don't know this for certain,
we don't have evidence.
But it is physically possible
for that to have happened.
Was the Earth seeded
by microscopic martians
blown into space
by the Borealis impact?
It sounds crazy,
but the science stacks up.
We know that simple life
is tough,
able to survive
in the cold vacuum of space,
and the timing
of the Borealis impact
works out well for the rise
of the first organisms on Earth.
Crucially, we know that rocks
ejected from Mars
can make it
all the way to Earth
because they're still
crash landing here, even today.
One of the coolest things
I've done as a scientist
is held a piece of Mars
in my hands.
Now, we never had a mission that
returned a sample from Mars,
we had to come about it
a different way.
And it turns out
we have meteorites
that we are 100% sure
are bits of Mars.
They were actually exploded out
during huge collisions,
and eventually
they fell on the Earth.
Four different generations
of martians,
each of them facing
a different planetary
catastrophe.
But despite enormous odds,
martians could
still be alive today,
buried deep under
the surface of Mars,
or maybe even
thriving on Earth.
If life is really that tenacious
that it can come back
and keep coming back
and keep coming back,
that gives me a lot of hope
for life in the universe.
That tells me that life
is maybe tough,
maybe individuals are fragile,
but maybe life itself is tough.
For now,
all we can do is speculate
until future generations
develop the technology
to visit the red planet
and grab our first sample
of extraterrestrial life.
That's going to change
everything.
We're going to have
another example
of how life started
and how life works.
And even if it's something
that's dead,
we knew it was there.
The universe will never be
the same again.
early life was on the brink
of extinction.
Colossal impacts...
Ferocious climate change...
And total atmospheric collapse
have turned paradise into hell.
But this isn't Earth...
It's Mars...
And this is the violent
history of perhaps
the first life forms
in our solar system.
Could these martians
still exist today?
Could they even be
living among us?
Captions paid for by
discovery communications
scientists suspect that life may
once have thrived on Mars...
That the barren world
we see today
swarmed with martians long ago.
If I had to bet something
incredibly valuable to me...
If I had to bet my car...
On whether or not
there's life on Mars,
or evidence of past life
on Mars,
I'd take that bet.
The building blocks for life
are widespread in the universe,
and early Mars could have been
the perfect place
to pull these
ingredients together.
If you had a recipe book for
everything you need for life,
you'd have things like water,
organic chemistry,
a stable surface,
a thick atmosphere...
Well, Mars had
all of those.
Mars satisfies
every specific requirement
for letting life get started.
Life on Mars
may have been inevitable,
and we've sent a robot army
to hunt for signs of it.
But so far,
it's been elusive.
Our rovers, landers,
and satellites
haven't found life yet,
but they have found evidence
of something extraordinary.
Mars was the victim
of a devastating series
of extinction-level events
that rocked
the red planet to its core...
Leading us to wonder,
if life could have started over
multiple times,
with generation
after generation of martians
rising and falling through
Mars' violent history.
It seems likely
that a first Genesis of life
could have occurred very early
on in Mars' history,
just as soon
as the crust was cool enough
to give it a solid foothold.
The secret to this early life
would have been
a crucial ingredient,
one shared by the young Earth.
Dry, harsh Mars
once had oceans.
For life to get started,
you need some carbon,
an energy source,
it needs nutrients
like nitrogen...
But those are likely to be
present on Mars,
they are present
and widespread on Earth.
The essential requirement
is really the liquid water.
Picture Mars
4.5 billion years ago.
Molten rock has cooled
to form a solid crust.
Water collects on the surface,
forming primitive oceans.
Rain clouds sweep across
the steaming,
volcanic landscape,
and in shallow pools
of water,
the martians
begin to emerge.
But these first aliens
are simpler
than Sci-Fi
would have us believe.
We're probably not talking
about little green men
or women, or whoever.
Walking around on the surface
of Mars, we...
We're talking
about something probably
much, much smaller
and simpler,
single-celled life.
If would look familiar,
it would look just like
bacteria on Earth.
Little, tiny, round,
rod-shaped organisms.
If this generation
of bacterial martian life
really did exist,
it was the first life
to grace our solar system.
Multiplying inside
the rock pools of Mars
long before life
took hold on Earth,
Mars' small size would've
given it a head start.
Because Mars is smaller
than the Earth
it would have cooled
a little bit faster
than we did.
So early on in the life
of the solar system,
Mars may have been
more like Earth
than Earth was at the time.
Let's go back 100 million years
after the sun formed.
The surface of the Earth
is still a molten lake.
But martian life
could be thriving
on the smaller,
cooler world.
But these first martians
won't have long
to enjoy
their time in the sun.
Inescapable death is already
on its way from space...
A cosmic bomb so huge,
it would completely alter
the shape of the planet,
leaving it lopsided,
the northern
hemisphere crushed.
Most planets are round,
and that's just something
you don't really
give much thought to,
but it turns out Mars isn't
as round as it could be.
The Southern hemisphere,
on average,
has a higher elevation
than the northern hemisphere.
So, in other words, if you were
to start on the north pole
and walk all the way
around to the south pole,
you'd be walking uphill,
essentially, the whole time.
So, we call this difference
between the northern
and the Southern hemisphere,
we call this the crustal
dichotomy on Mars,
and it's been one of the biggest
mysteries of the planet,
you know, it's the first thing
that you see about it,
and you say, well, how could
this possibly have happened?
In 2008, scientists mapping
the surface of Mars came up
with an explanation
for the massive dent
in the planet, shown in blue.
This basin, the biggest
in the solar system,
had to be the result
of a massive impact.
Called the Borealis impact,
it blasted out a crater 6500
miles wide and five miles deep,
big enough to swallow
the entire United States
with room to spare.
Something really big happened.
In fact, the entire top half
of the planet
seems to have
practically been blown off.
The only thing that could do
that is a huge collision,
and we're talking a collision
with something the size
of Pluto, perhaps.
You're talking about an impact
that makes
the dinosaur killer impact
65 million years ago look pretty
much like a wet firecracker.
4.5 billion years ago,
the early solar system
is filled
with planetesimals
and protoplanets...
Asteroid-like leftovers
from a planet building process
that created Mars
and the Earth.
One of these
asteroids is huge,
and it's on a direct collision
course with Mars.
Any microscopic martians
have just seconds to live.
If this impact
was happening today
and we were so unlucky
as to be there to witness it,
what you first would have seen
is another moon in the sky...
And then you would've
looked back and seen,
oh, it's getting bigger.
As it came down it would have
filled the entire sky,
from horizon to horizon,
and as it struck,
the top would have still
been well out into space.
The impactor
is 1200 miles across,
the size of Pluto,
and as it hits,
the energy of the impact
shakes Mars to its core.
The entire planet
wobbles like jell-o.
As it came down,
it would have been hitting
into the surface of Mars
as fast as a bullet
out of a gun,
and it would have slammed
into the surface
and sent a shockwave out
that would've been bigger than
any earthquake ever recorded.
It would have been
like a Tsunami of rock
coming out and tossing us
out of the way.
The impact is catastrophic.
It blows nearly half
the planet's surface into space
and turns what crust remains
into a boiling lake of lava.
You can't have
an impact of that scale
without almost melting
the planet.
It's not literally
a planet breaking event,
but it's
a planet melting event,
and it is, it is
the sterilization
of the planet
at that point.
The surface of Mars was molten,
its atmosphere
blown into space,
the oceans boiled away.
If Mars was home
to the first generation of life
in our solar system,
that life didn't
stand a chance.
It would take the surface
of Mars 50 million years
to recover from the impact.
But what sort of planet
will rise from the ashes?
Compelling new evidence suggests
that the conditions for life
may have returned to Mars,
but did life itself
make a comeback?
This impact
was only a blip in time,
and there was possibilities
for life
and the planet to recover.
4.5 billion years ago
an asteroid
the size of Pluto
slammed into the surface
of infant Mars.
It melted the surface
of the planet,
it blew the atmosphere
into space,
and it boiled
away the oceans.
If life had gotten
a foothold on the planet,
that life would have been
completely exterminated.
But some scientists
believe this extinction
could have been brief,
and that life could have
started again from scratch.
One of the wonderful things
to imagine is that
there probably wasn't
a single origin of life.
It's not like
it happened once
and then everything
just went from there.
Maybe there were multiple times
that life got started
and went extinct.
Ten million years
after the Borealis impact
crushed the planet's
northern hemisphere,
Mars has cooled enough
for its surface
to become solid once more.
The planet has some
of the ingredients for life...
The right molecules,
a stable surface,
and an energy source.
But something's missing.
4.49 billion years ago
the surface of Mars was dry,
and without water,
life can't start over
and a second generation
of martian can never arise.
As far as we know life,
water is absolutely,
fundamentally important to life.
2004... NASA's opportunity rover
lands on Mars.
Part of its mission
is to search for evidence
that water returned to Mars
after the Borealis impact.
It's not long before
opportunity
stumbles across something
strange on the surface
of a fossilized sand dune...
Bizarre, round,
metallic rocks.
These rocks are called
blueberries,
and they're an important find
for planetary geologists,
like Jani Radebaugh,
because fossilized
sand dunes also exist on Earth.
And Utah's petrified dunes
are also littered
with blueberries.
This is really exciting
because we've seen the exact
same thing on Mars.
Finding blueberries on Mars
is significant,
because the Borealis impact
melted the planet,
so anything found
on Mars today
must have formed
after the impact.
But crucially,
these nodules of iron oxide
formed deep underground
and in the presence of water.
In order to form one of these
little blueberries,
there needs to be huge
amounts of water
flushing down
through the fossil sand dunes,
and as it does that,
it carries with it all
of the iron oxides
around each sand grain.
And just one tiny,
little one like this...
Now, this is maybe about
an ounce of iron,
maybe a little bit more...
And in order
to get an ounce of iron
to concentrate into
this blueberry,
you need to have
a thousand gallons of water.
Blueberries form
deep inside sandstone.
But over thousands
of years,
wind erosion blows away
the softer rock,
leaving just
the blueberries behind.
If we walk to the edge
of this
pile of blueberries,
we could see
the process by which
they're actually eroding
out of the rock.
The blueberries
right here contain
within this fossil
sandstone layer.
The winds are blowing
in this direction,
down the layers,
and they're actually eroding out
the soft sandstones right here
and leaving behind
very dense iron nodules,
and as they pluck themselves
out of the rock,
they roll down the hill
and they collect...
Right here,
in between layers.
We know we found conditions
just like this on Mars.
We have fossil
sand dune layers,
we also have blueberries
all over the surface,
so we know
the same kinds of things
had to have happened on Mars
that have happened here.
There has to be water
flowing through the rock,
gathering iron,
and then there has to be
a huge amount of wind
to strip away
the fossil sand dunes.
For blueberries to exist
on the surface of Mars today,
the red planet
must have gotten its water
and its atmosphere back after
the catastrophic impact.
With liquid water
on the surface,
the ingredients of life might
have combined, once again,
to create
a second generation of martians.
But where did this water
come from?
The answer is surprising.
It could have been
in the planet itself...
Water is incredibly abundant.
We know that
there's water deep,
deep, deep
in the Earth's mantle,
and so it's entirely
possible that on Mars
there was water so deep
in the planet
that even after this
catastrophe, it came back up.
On the Earth, scientists
diffuse the seismic waves
of earthquakes
to detect
an ocean's worth of water
chemically embedded
in minerals deep underground.
A similar water source
could have been hidden
hundreds of miles below
post-impact Mars,
and volcanoes could have brought
that water back to the surface.
One way for water to get from
deep underneath the surface
to the surface of the planet
would be through
geologic activities...
Volcanoes, for example.
We know that volcanoes spew out
a lot of gasses on Earth,
including water vapor,
and we see
volcanoes on Mars.
Mars is home to the largest
volcanoes
in the solar system.
The biggest of all,
Olympus Mons,
is over three times
taller than mount Everest.
4.49 billion years ago volcanoes
spew lava spiked with water
into the atmosphere
and create ferocious rainstorms
that flood
the surface of Mars.
Over tens of thousands
of years
Mars becomes
a watery world once again
with the perfect conditions
for a second generation
of martians to rise up.
It would seem that
when you have
a massive collision,
like what happened to Mars,
it would be game over
for life.
But there's something
more complicated going on.
Maybe that asteroid impact
kicked off
an entirely new cycle
of life on Mars.
In theory,
four billion years ago,
a second generation of
single-cell bacterial life
arose on Mars,
and for the very first time
there was life
on two planets
in the solar system.
140 million miles away,
life on Earth had just begun,
and thanks to Earth's
stable climate,
it would one day
evolve into us.
But the outlook for Mars
was very different.
Evidence from the Mars
reconnaissance orbiter
suggests an icy apocalypse
was about to strike.
For Mars' second generation,
winter was coming.
Four billion years ago,
the first life
has arisen on Earth,
but on Mars, life may be
starting out for a second time.
It's possible that Mars
had life before Earth did...
It got wiped out...
And then got started again
by rehydrating the planet.
A planetary collision
has blown away Mars'
atmosphere and oceans,
along with any life,
but giant volcanoes have brought
water back to the surface
from deep within the planet.
This could have allowed
for a second generation
of life to rise up.
But these martians are about
to be tested to their limits
by catastrophic
climate change.
2008... NASA's Mars
reconnaissance orbiter
flies high
over the surface of Mars.
Its ground-penetrating
instruments
peer deep below the surface,
aiming to unlock Mars'
geological secrets.
As it scans
near Mars' equator,
the orbiter spots something
that has no right to be there...
A vast,
underground glacier.
One mile thick and three times
the size of Los Angeles,
ice on this scale should
only form at the frigid poles.
The only explanation...
Mars must have been
tipped over
with its equator
tilted away from the sun.
The tilt on Mars' axis
has actually changed
significantly over time,
and in non-systematic ways,
it just happens randomly
that it will start moving,
and so there are some
models that suggest
that Mars has actually been
almost tipped over on its end.
Most planets wobble,
and from time to time,
they wobble so much
they can tip over,
leading to super winters.
If that had happened
here on Earth,
Los Angeles
could become the arctic.
Well, you can imagine something
similar would happen on Mars,
how drastic the change
would be.
You're used to seeing
the sun overhead,
it's very warm,
there's probably liquid water,
and as the planet
starts going this way,
the sun is not gonna rise
as high in the sky.
Eventually you may not see
sunrise for half a year,
and any water that's
there is gonna be frozen solid.
3.9 billion years ago,
Mars is tilting
by as much as 80 degrees.
Winter temperatures drop below
minus 125 degrees Fahrenheit.
As the polar ice sheet spreads
quickly toward the equator,
liquid water is frozen solid,
along with any potential
martians.
The water that drives
the biochemistry of life
freezes inside
the tiny bacteria.
Ice crystals form and puncture
the martian's cell walls
until eventually, they die.
Every 120,000 years
the tilt of Mars changes,
as again and again
the planet's chaotic wobble
flips the martians in and out
of the deep freeze.
Any second generation
of life on Mars...
Is left in tatters.
Meanwhile, on Earth, our ancient
ancestors have it easy.
The Earth's wobble, and its
seasons, stay relatively stable,
and it's all thanks
to our secret weapon...
Our oversized moon.
The interaction
of our planet and the moon
means that the axis of our
rotation is very, very stable.
The seasons return year after
year, century after century,
for billions of years.
Our moon's enormous mass
exerts a huge gravitational pull
on the Earth,
stabilizing the wobble
of our planet
and keeping
our climate in check.
Without the moon,
the early Earth
would have wobbled
just as wildly as Mars,
and our ancestors could have
faced the same icy fate
as the early martians.
Mars doesn't have a big moon,
it has two, little,
tiny moons
that don't really
affect it much.
So if the martians were killed
the first time
by a giant impact,
they may have been killed
a second time
by Mars itself not being
stable and flipping over
and having catastrophic
super winters and super summers,
basically, mega catastrophic
climate change.
On Mars, the outlook for life
seems bleak.
But the brutal conditions
that drive martian life
to the edge of extinction
may also have pushed it
to adapt and evolve.
We know this because on Earth
organisms known as extremophiles
have evolved to live in the most
severe of circumstances,
from boiling,
hydro-thermal vents...
To the deep freeze
of glacial ice.
When the going gets tough,
life seems to get tougher.
Maybe the martian
super winters
gave rise to
a third generation of life...
A super tough army of bugs
able to survive
the harshest
of climate swings.
What we see on Earth
is that life evolves
to occupy
whatever niche it lives in,
and that evolution takes time.
So as the environment changes,
life changes with it.
If there are sudden changes,
then life forms can't cope
with it and many die away.
Those that survive,
they continue on.
3.8 billion years ago
a third generation
of life could have thrived
on the surface of Mars.
Evolved from a handful
of its predecessors
to make it through
Mars' super winters,
it's the toughest
martian life yet.
But, as the super winters end,
the challenges for life
on Mars are set to get worse.
Another extinction-level event
is on the way.
Mars' atmosphere is being ripped
away molecule by molecule.
Could this be the killer punch
that wipes out
the martians for good?
Narrator: Imagine Mars
3.8 billion years ago.
It's a warm, wet world,
and super tough bacterial life
is thriving.
But these martians are not
the planet's first inhabitants.
The first generation
of martian is vaporized
by the huge Borealis impact.
Perhaps life starts over
from scratch,
but endures a series
of extreme climate swings.
Only the toughest martians
make it through.
But another disaster
is about to strike,
and this catastrophe will test
even the strongest martians.
They're about to lose the most
basic ingredient of life...
Liquid water.
You really have to appreciate
how difficult it is
to have liquid water
on the surface of a planet.
We know that life works
so well
when there's
liquid water around.
But you need
just the right balance
of air pressure
and temperature.
Without air pressure
weighing down on it,
liquid water will evaporate from
the surface of a planet,
whatever the temperature.
That air pressure
is generated
by the presence
of an atmosphere.
In a lot of ways that atmosphere
serves as a kind of a lid
stopping down the water
from escaping into space.
It's very important
to have that atmosphere.
3.7 billion years ago,
life on Earth enjoys warm oceans
and a thick atmosphere.
But on Mars,
a third extinction-level event
is gaining momentum.
The atmosphere is slowly
being stripped away,
and Mars' great oceans
are starting to evaporate.
The fate of life
on both planets
now rests on the strength
of their magnetic cores.
It turns out
that the existence
of an atmosphere on Earth may
rely on the magnetic field,
because what
our magnetic field does
is it protects us from
the onslaught of this wind,
of subatomic particles
that the sun is blowing out
all the time.
We call this the solar wind.
And if we didn't
have a magnetic field
to basically catch and deflect
those particles gently,
they would directly slam
into the Earth's atmosphere.
If you think
of the magnetic field
as a windbreaker
from the solar winds,
once we lose that protection,
that planet becomes
very vulnerable.
The Earth's magnetic core
has stayed strong
for 3.45 billion years
as super hot molten iron
churns over and over
within the planet
like a lava lamp.
Churning iron
creates electricity,
which in turn generates
a magnetic field
that rises up around the Earth,
acting like a magnetic shield,
protecting our atmosphere from
the ravages of the solar wind.
3.8 billion years ago
Mars had a molten core
and a magnetic field.
But something caused
its shield to drop.
Did Mars' small molten core
simply get too cold to function?
Or did
something else kickstart
this third great extinction
of martian life?
A new and controversial
theory points the finger
partly at
the ancient Borealis impact.
A giant impact of this scale
can affect a range
of temperatures,
from the hot inner core
to the cooler outer mantle.
4.5 billion years ago
the impact that vaporizes
the first generation
of martian life
also drives heat
into the planet,
increasing the temperatures
in the outer mantle.
The heat inside the planet
evens out,
and the metals
slowly stop churning.
But there's less
of a temperature gradient...
That makes it harder
for this dyno process to,
to drive a strong
magnetic field.
Over hundreds of millions
of years, Mars' magnetic field
shuts down.
When Mars lost its magnetic
field all of a sudden
it was completely
vulnerable to the solar wind.
The solar wind
could break apart
and carry away
the martian atmosphere.
3.7 billion years ago
super tough martian life
faces annihilation.
Bit by bits, the atmosphere
is being swept into space.
The air pressure
is dropping across the planet
and most of Mars' water
has already boiled away.
The chances of survival
without this precious liquid
are remote.
But, for the martians, there's
an even more immediate danger.
With no magnetic field
and no thick atmosphere,
the surface of Mars
feels the full force
of the sun's radiation.
If you're a microbe
on the surface,
you would
have to make do
with very little atmosphere,
no water,
this flood of ultraviolet light
from the sun,
and these particles which are
slamming into you all the time.
The martians are bombarded
by radiation
from the solar wind.
It rips their DNA apart.
Without an atmosphere,
the surface of the planet
is sterilized.
But is this really
the end for martian life?
Life is so tenacious,
it can survive even those
incredible catastrophic changes,
and it may still
be there today.
To survive the radiation,
martian life would have had to
have moved deep underground.
In this protected
subterranean environment
it may also have found
a source of liquid water,
and if that happened,
could the martians
still be there today,
waiting for us to drop in
and say hello?
Since the 1960s
robotic probes and landers
have been searching the surface
of Mars for signs of life.
But have they been looking
in the right places?
The surface of Mars
is a waterless desert
that's bombarded
by harmful radiation.
If a fourth incarnation of
martian life is alive today,
many scientists think it'll
have to be deep underground.
Underneath the surface of Mars
you may have all the conditions
you need for life.
There may be some liquid water
down there,
and you're also protected
from the intense radiation
that you find on the surface.
Scientists are split
on the best underground places
to search for martian life.
But if Jani Radebaugh
were on Mars,
she would head to the nearest
sand dune and start digging.
Here you can see
this is wet sand
just below the surface.
This is the perfect environment
to be able to house life.
Even in the very driest
deserts on Earth,
in between the sand dunes,
in the inter-dunes,
you can find water
percolating up from Springs
that come up from
deep under the ground,
perfect for life
to form and grow.
And if you just keep on
digging...
Down into the bottom
of the inter-dune,
maybe you would reach
the water table.
And if you reach
the water table on Mars,
now you have all the conditions
just right for life.
This is my bet,
this is where I'd go,
right between the dunes.
Digging for martian life
in the desert is one option.
But some scientists
have very different ideas,
and planetary scientist
Nina lanza
would need to pack a rope
and a flashlight for her search.
So if were to go to Mars
to find life,
I would go to a lava tube.
Lava tubes are made
by ancient volcanoes,
the empty leftovers from
underground lava flows.
Today,
they form deep tunnels,
shielded from radiation
and shut off
from the harsh
martian climate.
We've never been
in a lava tube on Mars,
but it is absolutely possible
that there's liquid water.
So, that's an environment where
you could have some moisture,
you could have a little warmth,
you're protected from radiation.
I think that a martian microbe
would be very happy there.
Finding life on Mars
would be a monumental
human accomplishment.
But there is a danger.
By exposing martian
life to life from Earth,
could we unwittingly set off yet
another extinction event?
Humans have been
one of the most effective
extinction mechanisms
of life on Earth.
The interesting
question will be,
will we produce a similar
calamity on Mars?
If humans someday
go to Mars,
then we will be
an invasive species,
and if there is some
martian life
that's hanging on
in some niche,
we could be
their ultimate destroyers.
So we have an ethical
responsibility
to preserve whatever
life may be on Mars.
The problem isn't us,
it's the bugs
in and on our bodies.
The average human has
ten to 20 trillion
bacterial hitchhikers.
If we go to Mars,
we'll be taking our tiny
companions along for the ride,
and any one of those bugs
could turn out to be
a deadly competitor
for martian life.
It's NASA engineer
Moogega Cooper's
job to keep
Mars rovers bug-free.
But keeping astronauts clean,
that's a whole different matter.
We bake our spacecraft hardware
at 110 degrees Celsius
for at least 50 hours
to prevent the contamination
of Mars.
But unlike spacecraft,
we cannot bake humans out.
We will not survive
those temperatures.
Unless we find a way
to keep astronauts bug-free,
exploring Mars with robots
is our best option
for keeping the martians
safe from harm.
But what will happen
when our robots
finally find that life and we
look deep into the workings
of our extraterrestrial
neighbors?
What will the martians
turn out to be like?
Our example where DNA
is the organic molecule
that carries
the information of life...
We don't even know
if that's gonna be
the rulebook in other places.
Finding any evidence
whatsoever on Mars
would help us better understand
what else is possible.
Will the martians
be different than us?
Made from
different materials
and with a different
biochemistry?
Or will they seem
shockingly familiar?
Some scientists think
that the very first martian life
may not have stayed on Mars.
It may have come here.
It's not that
farfetched to think
that life could have
jumped from Mars
or been a back and forth
from Mars to Earth.
If the martians came to Earth,
could they have seeded life
on our planet?
Maybe the martians aren't dead.
Maybe I'm a martian,
maybe you're a martian.
We've sent a robot army to Mars,
and what it's found
is astonishing.
The possibility that life
could have arisen there,
perhaps more than once,
with different generations of
martians emerging from the ashes
of catastrophic
extinction events.
Life could still be sheltering
below the surface of Mars
right now.
But there's another possibility
that's truly astounding...
That martians
aren't just hiding out on Mars,
they're thriving,
right here on Earth.
I might be a martian,
you might be a martian.
We might be from another planet.
We might have already travelled
and lived on two planets
as life forms...
Not as a species, certainly,
but our ancestors may have
come from another planet,
and that is mind blowing.
The idea that our ancestors
could be martians
is a new take on an old theory
called Panspermia.
According to the theory,
life on Earth began
when a space rock
filled with alien bacteria
landed on the Earth
and every living thing
we see today, including us,
evolved from those
cosmic hitchhikers.
The idea of Panspermia
has been around for centuries,
but had a resurgence
when scientists
determined that life on Earth
may go back four billion years,
to the end of a sustained
attack of asteroid showers
known as the late heavy
bombardment.
There are a lot of objects
from the outer solar system...
Comets and asteroids,
all kinds of things...
Coming into
the inner solar system
and slamming
into the planets.
Conventional wisdom
suggests the objects
hitting the Earth at the time
were leftover debris
from the formation
of the solar system.
But a very controversial idea
suggests these space rocks were
actually all pieces of Mars,
thrown off
in the Borealis space impact
when a huge object
blasted into Mars.
The timing links up really well
for the Borealis space impact.
If you calculate
how much debris
that would have been
thrown out into space
and when it would have
had to have happened,
according to the martian
geologic record,
it coincides with
the late heavy bombardment...
It's possible
that the debris
from the Borealis
space in forming impact
might have come to Earth
and rained down on us
and made the late heavy
bombardment,
seeding the Earth with
bacterial spores from Mars.
Now, this is just a hypothesis,
we don't know this for certain,
we don't have evidence.
But it is physically possible
for that to have happened.
Was the Earth seeded
by microscopic martians
blown into space
by the Borealis impact?
It sounds crazy,
but the science stacks up.
We know that simple life
is tough,
able to survive
in the cold vacuum of space,
and the timing
of the Borealis impact
works out well for the rise
of the first organisms on Earth.
Crucially, we know that rocks
ejected from Mars
can make it
all the way to Earth
because they're still
crash landing here, even today.
One of the coolest things
I've done as a scientist
is held a piece of Mars
in my hands.
Now, we never had a mission that
returned a sample from Mars,
we had to come about it
a different way.
And it turns out
we have meteorites
that we are 100% sure
are bits of Mars.
They were actually exploded out
during huge collisions,
and eventually
they fell on the Earth.
Four different generations
of martians,
each of them facing
a different planetary
catastrophe.
But despite enormous odds,
martians could
still be alive today,
buried deep under
the surface of Mars,
or maybe even
thriving on Earth.
If life is really that tenacious
that it can come back
and keep coming back
and keep coming back,
that gives me a lot of hope
for life in the universe.
That tells me that life
is maybe tough,
maybe individuals are fragile,
but maybe life itself is tough.
For now,
all we can do is speculate
until future generations
develop the technology
to visit the red planet
and grab our first sample
of extraterrestrial life.
That's going to change
everything.
We're going to have
another example
of how life started
and how life works.
And even if it's something
that's dead,
we knew it was there.
The universe will never be
the same again.