Nova (1974–…): Season 46, Episode 13 - The Planets: Mars - full transcript
The dry, red planet Mars was once a blue water world studded with active volcanoes. But if it once had many of the ingredients necessary to form life, how far along might that process have gotten?
Two rocky worlds formed
at the same time...
now close neighbors.
One blue with oceans
and full of life.
Earth has got
this rampant biosphere.
The other a barren desert.
If you look at Mars,
it's a red, dusty planet,
it's super dry.
But it hasn't always been
that way.
There's a lot of evidence
for ancient flowing water
on Mars.
It was a bizarre discovery,
it was startling.
Stunning findings reveal
a deep mystery...
Why is Mars so different
from Earth?
Daring to us to explore...
We knew it landed safely
when we realized that the wheels
sensed the ground.
We had successfully landed
on Mars.
And discover.
What we found in those rocks
is a turning point for us.
Finding the organic matter
is the clue
to searching for life.
And if life did evolve
in its ancient oceans,
what happened to it?
How far along did it get
and did it go long enough
that life could have taken hold
there?
It opens up the possibility
that the universe is full
of life.
"The Planets: Mars"
right now, on "NOVA."
Major funding for "NOVA"
is provided by the following:
Doppler and orbit around
the planet Mars.
("The Void" by Muse playing)
♪ They'll say
no one can see us
♪ That we're estranged
and all alone
♪ They believe
nothing can reach us
♪ And pull us out
of the boundless gloom
♪ They're wrong
♪ They're wrong
♪ They're wrong
Mars.
Our planetary neighbor is
a barren desert world,
its surface red with rusted rock
and parched sand.
But beneath the dust
Mars bears the scars
of a former life.
Four billion years ago,
Mars was
a very different world...
Its atmosphere dense enough
to support seas...
and rivers of running water,
what we believe are
the conditions
for life to emerge.
But today
that vibrant world is gone.
Its rivers run dry.
Oceans evaporated.
While clearly visible
from the red planet's surface,
is its neighbor, Earth...
blue with oceans
and teeming with life.
On Earth we have this
amazing biosphere
that is super-vigorous.
There's an ocean,
all sorts of things are
happening.
If you look at Mars,
it's a red, dusty planet,
it's super dry.
One of the questions is,
"Why are they different?"
Earth has a thick atmosphere,
Mars has a very thin atmosphere.
Earth is warm almost everywhere,
Mars is freezing cold
almost everywhere.
So these are very different
planets.
But if you go back
into the past,
around four billion years ago,
the two planets were probably
very similar.
4.6 billion years ago
an innocuous cloud of dust
and gas
is collapsing,
forming the embryonic sun.
Swirling around it,
the remnants of the dust cloud
are slowly drawn together
by gravity...
forming eight new worlds.
Amongst them:
our smaller neighbor, Mars...
and our home planet Earth
are both rich
with elements like carbon,
metals like iron,
and, crucially, water.
But despite many similarities
at birth,
their differences in size
and distance from the sun
set them
on very different paths.
These two planets started off
very similarly.
It's what I like to call
comparative planetary evolution.
The same things could have been
happening
in the very beginning
of their existence.
And then as the clock ticks
forward geologically,
they actually become
very different from each other.
And that's the fascinating part.
What's happened since?
If they looked and acted similar
in the very beginning,
and life formed on one planet,
possibly on the other,
then what happened?
Five, four...
To find out has taken decades
of pioneering exploration.
Mariner 4 was successfully
launched on time
for its historic 228-day journey
to Mars.
Picture information started
to come in
on July 15, 1965.
During its brief flyby,
Mariner 4 gives
the first close-up glimpses
of Mars.
A revelation,
comparable to Galileo's
first view of the moon
through a telescope.
Beautiful picture.
First of all,
there are two eyes.
Not only in color
but also in stereo
and in the infrared part
of the spectrum.
Viking is the first
to successfully land on Mars.
Touchdown, we have touchdown.
Perfect set down.
And there's the first piece
of information coming in.
Oh, oh.
But the most surprising
revelations
come from the rovers...
Spirit and Opportunity.
Over 50 years
of Mars exploration
has revealed intriguing clues
suggesting Mars has
a surprisingly watery past.
There's a lot of evidence
for ancient flowing water
on Mars.
For one thing,
there's a lot of rivers
that once coursed
across the surface
that are now dry today.
There's also evidence for floods
that catastrophically scoured
the surface.
It's undeniable
that the early history of Mars
was much wetter
than it is today.
The surface of Mars is littered
with an uncountable number
of little round things.
These blueberries,
as we nicknamed them,
are what geologists called
concretions.
Concretions form typically
in sedimentary rocks
that are soaked
with liquid water.
And so what those blueberries
told us
was that this was a place where
the ground was once soaked.
It might not have been as wet
as the earth.
But it was probably wet enough
for life to evolve.
What everybody wants to know
is whether or not
Mars once had life.
Were conditions on Mars
once suitable for life?
To find out,
a new generation of spacecraft
is investigating...
led by the most complex mission
to the red planet
ever attempted.
Vehicle reports entry interface.
We have two-way Doppler and
orbit around the planet Mars.
Mars has a unique set
of challenges,
compared to other places
we go with spacecraft.
Mars has an atmosphere,
but it's thin,
so it's not enough
to really slow you down.
But it is enough to burn you up
as you're trying to land.
To get Curiosity safely
to the surface of Mars,
we basically had to pull out
every trick in the book.
At 2,000 pounds,
Curiosity is one of the largest
and heaviest probes
anyone has ever attempted
to land
in the thin Martian atmosphere.
We fired rockets,
and a jet pack flew the rover
down to the surface.
We knew it landed safely
when we realized that
the wheels sensed the ground.
At that point
a signal was received,
and all of us sort of melted
in our seats,
knowing that we had successfully
landed on Mars.
Safe on Mars.
Just a few minutes
after landing,
we had the first images
come back.
It's a thrill to see images
of a new world,
you know, from eye level
for the first time.
Curiosity touches down
in Gale Crater,
the remains of
an asteroid impact
about a hundred miles wide
thought to have been home
to ancient lakes and rivers.
As we drove out
of our landing site,
we came across what looked like
an upturned sidewalk
with like
concrete kind of breaking apart
and pebbles falling out of it.
This was a rock that had been
cemented together,
and when the geologists studied
those rounded pebbles,
they realized this rock probably
was once the bed of a river
flowing on Mars, with water
maybe, like, knee-deep.
To find out if these ancient
waters had the basic ingredients
for life, or endured long enough
to support it,
requires careful analysis.
Curiosity is
a roving laboratory.
We collect samples,
by scooping it or by drilling,
that allow us to pick apart
the story
that those things hold.
61 days after landing,
Curiosity takes the first
of many scoops of soil.
Analyzing the sand and stone
across the crater
reveals something surprising.
Not only is the Martian soil
bound with water molecules,
but also a small amount
of carbon-rich organic material.
Organic matter is
actually composed of carbon.
It's carbon molecules put
together.
And that is a turning point
for us.
What we found in those rocks
is what we expected
of natural organic matter.
It's what you would expect
to find on Earth.
Finding the organic matter
is the clue
to searching for life.
And, crucially,
these ingredients are present
for millions of years.
Really, the central discovery
of the mission so far
is that there were lakes
that survived
for maybe tens of millions
of years.
And within those lakes,
there was fresh water,
there were the raw materials
that life requires.
Just beneath the surface,
amongst ephemeral droplets
of concentrated brine,
lie the raw chemical ingredients
for life...
The final tears
of a long-lost world.
For hundreds of millions
of years,
Mars is a water world,
rich with the building blocks
for life.
Rains fall, rivers run,
and in the northern hemisphere
evidence suggests water collects
in a vast sea
bigger than the Arctic Ocean
that covers a fifth
of the Martian surface.
The red planet was once blue.
But it didn't last.
The fascination to me
about the early warm, wet Mars
is not what happened,
although
that's an interesting question,
why did it dry up?
The billion-dollar question is
whether or not
Mars actually originated life
before all the water was lost.
How far along did it get?
How is how far along did
the process go
and did it go long enough
that life could have taken hold
there?
Today only one blue planet
survives.
70% of Earth's surface
is covered by oceans.
Under the waves,
up to a million species
thrive...
While on land
the rains support
Earth's delicate ecosystems...
Providing a home
for complex life to evolve.
But our planet hasn't always
been so hospitable.
The early Earth
is unrecognizable
compared to the planet
we know today.
When Earth first formed,
it was this molten body
and it probably had a crust that
was forming around the outside,
and it was moving around a lot;
it was turning
into something rocky.
And then at the same time
that the rocks are forming,
we've also got gases
in the atmosphere,
liquid water to form oceans.
Chemical analyses
of our planet's oldest rocks
reveal its atmosphere
was choked with carbon dioxide
spewing from myriad
active volcanoes...
Making its newly formed
oceans acidic.
Early Earth was
a very different place
from today's Earth.
So if one looked at Earth
from another solar system
and asked, "Is Earth alive?"
it would have been hard to tell
four billion years ago.
And then everything changed,
and chaos ensued.
Clues as to what happened next
can be seen when the moon rises
in the night sky above us.
Etched into the moon's surface
are vast areas of impact craters
and lava fields...
traces of a violent past
revealed by the lunar landings.
Two, one, zero...
Over three years,
Apollo astronauts take samples
from across the moon's surface.
The age of the rocks
they collect
suggests the majority
of the craters form
in a narrow window of time
peaking 3.9 billion years ago.
And traveling
to the far side of the moon...
a side we never see from Earth,
reveal even more.
Countless craters,
a permanent record
of a ferocious bombardment
unleashed throughout
the inner solar system
thought to date
from the most violent period
since the planets themselves
formed,
known as the
Late Heavy Bombardment.
This Late Heavy Bombardment
turns out to be a critical event
in the history
especially
of the terrestrial planets.
All of the rocky planets were
being hit by other rocks
from other places
in the solar system.
Around four billion years ago,
while the outer planets are
settling into their orbits,
it's thought they disrupt
a cloud of icy objects
circling the edges of the
developing solar system...
sending many hurtling inwards
toward the sun.
And so these fragments
and pieces of rock
all arrive
at about the same time
in the inner part
of the solar system
to hit the planets like
Mercury, Venus, Mars,
Earth, and the moon.
Imagine meteorites hitting
on a regular basis.
It caused turmoil on the surface
of all those planets.
They basically hit
with such energy
that they resurface the planets.
As rocky asteroids fragment
in Mars's atmosphere,
havoc rains on every corner
of the planet.
Based on the rates of crater
formation on the moon,
it's thought at least 50 tons
of rock fall
for every square meter
of Mars's surface
in a hard rain that lasts
tens of millions of years.
Over a third of the
planet's crust is resurfaced...
as Mars descends into chaos.
Earth suffers the onslaught
just as Mars does...
relentlessly smashed
by falling rock.
Both young planets endure
a catastrophic pounding.
But just when conditions appear
at their least promising
on Earth,
the raw organic materials on
its surface come together...
To produce its most
precious creation...
Life.
The kind of environment
that's needed for life to start,
we need to be converting
the first organic molecules
to whole cells.
And those kind of conditions
require a dynamic geological
environment,
and that kind of environment
would have been everywhere
on the early Earth.
The volatile conditions on Earth
may be responsible
for turning the simple organic
molecules already present
into complex organic material
capable of replicating itself...
We don't know precisely
where life started.
It could have been an
environment like this,
a terrestrial geothermal system.
It could have been even
delivered from space,
perhaps organic molecules
delivered
into exactly
this kind of setting.
To me it seems more likely that
it started under the oceans
in deep-sea hydrothermal vents.
Volcanic activity erupting deep
in the oceans
would create
a high-energy system.
That pressure makes reactions
happen faster
and more likely to give rise
to life.
And the emergence of life
need not be limited
to just one planet.
Life should really start
wherever these geologically
active conditions are met,
where we have a continuous
bubbling of gases
from in the bowels of the planet
or the moon,
to react with gases in
the atmosphere or in the oceans.
These conditions are
very similar
to what we think might have been
present on Mars
four billion years ago.
But how can we be sure
that catalysts for life
like this
existed on Mars that long ago?
Ignition and liftoff
of the Atlas V rocket
with MRO.
Surveying
for the deepest insights
into the mysterious evolution
of Mars.
Searching for conditions
that could kickstart life
is NASA's
Mars Reconnaissance Orbiter.
Sent to map Mars
in intricate detail,
MRO sends back more data
than all other Mars missions
combined.
MRO has three cameras on board.
The first is
the MARCI weather camera.
It sees horizon to horizon
on every orbit,
so it builds up a map of
the entire planet every day.
So you can see a global
weather map ever day on Mars.
The second camera is
the context camera.
It provides high resolution,
and it's covered
about 99% of the surface.
MRO has made
more than 60,000 orbits...
Its high-resolution cameras
revealing Mars
in unprecedented detail...
Discovering polar avalanches,
shifting sand dunes,
and what look like
seasonal flows of sand
or even liquid meltwater.
Then, in 2017,
MRO turns its gaze
to some of the red planet's
oldest rocks:
in the Eridania Basin,
thought to have once been home
to an ancient sea.
Eridania Basin is a huge basin
in some of the
most ancient crust on Mars.
It formed
about 3.8 billion years ago,
and it held more water
than ten times that
of the Great Lakes
or three times that
of the Caspian Sea on Earth.
And it's on this ancient seabed
that MRO sees something
remarkable...
a potential catalyst for life.
MRO saw a massive,
400-meter-thick deposit
formed from a mineral
that forms in deep-sea
hydrothermal environments,
such as one that might have
undersea vents.
Analysis shows the deposits are
rich with saponite,
a mineral found on Earth
at hydrothermal vents...
suggesting in the past
Mars not only had the same
ingredients for life as Earth
but also an active environment
to spark it into action.
Eridania Basin was
an ancient sea
3.7 to 3.8 billion years ago.
And that's about the same time
when life was first emerging
on Earth.
This might have been a place
where life could have existed,
because those hydrothermal vents
underneath that sea
might have created a very
conducive environment for life.
These initial conditions
in the history of both planets
look so similar that
it seems reasonable to expect
that this could
eventually lead to life.
These actively fertile
conditions
are thought to survive in
places like the Eridania Basin
for hundreds of millions
of years,
with Mars, like Earth, rich
with the potential for life.
But then, 3.7 billion years ago,
something happens
that transforms prospects
for life on Mars forever.
Analysis
of the ancient Martian surface
reveals a dramatic change.
Mars underwent through a fairly
substantial transformation
in its climate.
The climate got colder.
What liquid water there was
either soaked into the ground
and froze
or froze at the surface.
A lot of it ultimately would get
transported to the poles,
where it forms these big,
thick icecaps
that we see today.
At the same time
as the temperature plummets...
Mars becomes
more volcanically active...
leading to catastrophic flooding
with water raging
for hundreds of miles.
Until, in a place known
as Echus Chasma,
it plunges over cliffs
two-and-half miles high...
Creating the largest waterfall
the solar system has ever
seen...
Cascading
into a spectacular canyon
six miles wide
and 60 miles long.
Once the floods subside,
the water disappears,
the only trace it ever existed
etched into
the planet's surface.
So what causes
this dramatic change in climate?
That's being investigated
by NASA's most active
Mars orbiter.
T-minus ten, nine, eight, seven,
six, five, four,
three, two, one.
Main engines start,
ignition, and lift off
of the Atlas V with MAVEN,
looking for clues
about the evolution of Mars
through its atmosphere.
In September 2014,
NASA's MAVEN probe is on
its final approach
to the red planet.
Its mission:
to understand the processes
that transformed Mars.
We know that the Mars climate
has changed through time.
The geological evidence tells us
there was lots of water
early on,
and that it's been cold and dry
in the last couple
of billion years.
Maven was sent there
to understand what processes
drove this climate change.
Based on observed
navigation data,
congratulations.
MAVEN flies in an elliptical
orbit around the planet.
At its lowest point,
it's only 150 kilometers
above the surface.
At its highest point,
it's over 6,000 kilometers.
That means that on every orbit,
we're able to measure
the full profile
of the entire upper atmosphere.
The previous missions
we've sent had cameras
to look at the geology
of the surface
or the behavior of the clouds
and dust
in the lower atmosphere.
We're making measurements
in the upper atmosphere,
where we're more interested
in the behavior of atoms
and molecules,
so our instruments are focused
on taking measurements of those.
MAVEN carries an array
of instruments
designed to measure the behavior
of atoms and molecules
in Mars's atmosphere.
From the measurements
that MAVEN has made now
over an entire Martian year,
we've confirmed that gas is
being lost to space today
out of the atmosphere.
And it's being lost at a rate
of about two to three kilograms
every second.
By measuring the gas being
stripped from its atmosphere,
MAVEN is witnessing the process
that transformed Mars's climate
over three-and-a-half
billion years ago.
We think that this stripping
of the atmosphere over time
has been responsible
for the change in climate
which Mars has suffered.
Mars lost much of its water
and the atmosphere
that insulated it
from the cold of space...
leaving it frozen and dry.
So what was it that sent Mars
down such a different path
from Earth?
The sun's outer corona burns at
a scorching one million degrees.
It releases a barrage
of charged particles that travel
at hundreds of miles a second...
The solar wind.
This onslaught would strip away
our atmosphere,
but for the powerful magnetic
field that protects us
The solar wind is
this stream of charged particles
that come streaming out
from the sun.
And at Earth,
which has
a powerful magnetic field,
when those charged particles
begin to get close to Earth,
they get diverted around Earth
by interactions
with that magnetic field.
That protection keeps solar wind
and other ionizing radiation
off of the surface.
So on Earth,
where we have this really great
magnetic field,
we are nice, safe, and sound
inside the shell of that,
protected
from all that radiation.
The magnetic field of Earth
effectively forms
a protective bubble
around the Earth's atmosphere.
And when the sun dips
below the horizon,
there are times when Earth's
protective force field
is visible.
The aurora is a stunning display
of Earth's magnetic field
in action.
It's best seen at the poles,
but across Earth
it's protecting our atmosphere
and all life on our planet.
This vital protective shield
is generated deep within.
The way a magnetic field is
generated inside a planet
is when you have
convective motion
in a fluid that is capable
of conducting electricity.
And in the Earth, that
electrically conducting fluid
is liquid iron.
And the molten portion
of the Earth's core
is a place where these motions
take place,
and it can set up
a magnetic field.
Just like Earth,
Mars once had
a molten metallic core,
generating a magnetic field
around the planet.
Auroras danced
above Mars's poles...
protecting its atmosphere
and seas below.
But the field didn't last.
In the oldest rocks on Mars,
you see evidence of
a once-powerful magnetic field.
You get to the younger rocks,
the rocks that are
three billion, two billion,
one billion years old,
no evidence of a magnetic field
whatsoever.
And there is no intrinsic
magnetic field on Mars today.
This invisible magnetic field
around the planet,
something we can't see,
it's like this layer of
protection around the planet...
disappeared.
Half a billion years
after it formed,
Mars's magnetic field dies out.
The bright auroras above
its poles slowly fade away...
As the shield
that protects the planet
shuts down for good.
Once it stops,
then what happens is
all the atmospheric components,
things like hydrogen and oxygen
that make up water,
they get stripped away
because you don't have
the shield,
the magnetic shield anymore.
So the high-energy particles
that come in from the sun
and from outer space,
they begin to strip away the
components that make up water.
Without its magnetic field
to protect it,
Mars's atmosphere and then water
slip away into space.
So why did Mars lose
its protective shield?
What happened
deep beneath its surface
that stopped Mars from
developing like Earth?
The answer lies at the beginning
of Mars's story...
at its very creation.
4.6 billion years ago,
when the planets were forming
from the dust cloud
circling the sun,
early differences
between Mars and Earth
set the young planets
on very different paths.
Crucially, Mars forms farther
from the sun,
where there is simply
less rocky material
to build a planet.
Mars is different
because it's not
just further out,
it's actually much smaller.
If a planet gets to be
too small,
it just freezes
all the way through.
Because Mars is so much smaller,
there's less thermal energy
coming from the interior
of the planet.
The planet is fundamentally
different
from the interior out,
and that is what separates Mars
from Earth.
It's this critical
size difference
that seals Mars's fate
and shapes its surprising story.
Four-and-a-half billion
years ago,
two young planets are born.
Initially inhospitable
and toxic...
both young planet develop
into warm, watery worlds.
They both survive the violence
of the Late Heavy Bombardment...
Emerging as mature planets,
primed with all the ingredients
for life to begin.
But while Mars appears
to be thriving,
deep in its cooling core,
the planet is dying.
Its once-great ocean is lost
to space.
One by one,
its volcanoes go out.
As the lava turns to stone,
all hope of recovery is
extinguished.
Today, Mars traces a lonely path
through the solar system,
rusted and gathering dust.
But this is far from the end
of what we hope to discover.
The next generation
of spacecraft
will soon be on their way...
with missions like
European Space Agency's ExoMars
and Mars 2020 searching
for signs of life...
And NASA's Orion,
currently undergoing
advance testing...
NASA's first step toward
sending humans to Mars.
My hopes for the future
eventually there's boot-prints
on the surface.
You know, humans on the surface
doing what humans do... explore.
Humans are going to go to Mars.
I can't wait to see someone else
not virtually explore Mars
but really explore Mars,
as a human being,
walking on the surface.
Future generations will be able
to look closer than ever before
for evidence of life.
So the next step is to search
for life on Mars.
We're probably going
to bring samples home.
We'll study them here, and
we'll learn all sorts of things
about ancient Mars
and even modern Mars.
And if we do find life on Mars,
the consequences will be
profound.
If you could show that
life independently took hold,
independently,
on two different worlds
just in this one solar system,
then when you consider the
multitude of planetary systems
that we now know are out there,
it takes no great leap
of imagination, faith,
or anything else
to believe that life could be
a universal phenomenon.
It's a situation where two is
a much bigger number than one.
I think if one was
to ever discover life
anywhere outside of Earth,
it opens up the possibility that
the universe is full of life.
Because if you find just
one example in our solar system,
now you imagine
all the solar systems
that have been discovered
that we call exoplanets,
and then you multiply
these things,
and it must mean
that life is everywhere.
I often wonder
how the world would react
if we found life on Mars.
For me personally,
it almost feels like
we're reaching the point
where it would be more
surprising not to find life.
I think it still would shock
all of us,
and we'd be amazed that
such a discovery was made,
but I've personally come to
think that life must be present
all over the universe,
and maybe even on a planet
as close as Mars.
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at the same time...
now close neighbors.
One blue with oceans
and full of life.
Earth has got
this rampant biosphere.
The other a barren desert.
If you look at Mars,
it's a red, dusty planet,
it's super dry.
But it hasn't always been
that way.
There's a lot of evidence
for ancient flowing water
on Mars.
It was a bizarre discovery,
it was startling.
Stunning findings reveal
a deep mystery...
Why is Mars so different
from Earth?
Daring to us to explore...
We knew it landed safely
when we realized that the wheels
sensed the ground.
We had successfully landed
on Mars.
And discover.
What we found in those rocks
is a turning point for us.
Finding the organic matter
is the clue
to searching for life.
And if life did evolve
in its ancient oceans,
what happened to it?
How far along did it get
and did it go long enough
that life could have taken hold
there?
It opens up the possibility
that the universe is full
of life.
"The Planets: Mars"
right now, on "NOVA."
Major funding for "NOVA"
is provided by the following:
Doppler and orbit around
the planet Mars.
("The Void" by Muse playing)
♪ They'll say
no one can see us
♪ That we're estranged
and all alone
♪ They believe
nothing can reach us
♪ And pull us out
of the boundless gloom
♪ They're wrong
♪ They're wrong
♪ They're wrong
Mars.
Our planetary neighbor is
a barren desert world,
its surface red with rusted rock
and parched sand.
But beneath the dust
Mars bears the scars
of a former life.
Four billion years ago,
Mars was
a very different world...
Its atmosphere dense enough
to support seas...
and rivers of running water,
what we believe are
the conditions
for life to emerge.
But today
that vibrant world is gone.
Its rivers run dry.
Oceans evaporated.
While clearly visible
from the red planet's surface,
is its neighbor, Earth...
blue with oceans
and teeming with life.
On Earth we have this
amazing biosphere
that is super-vigorous.
There's an ocean,
all sorts of things are
happening.
If you look at Mars,
it's a red, dusty planet,
it's super dry.
One of the questions is,
"Why are they different?"
Earth has a thick atmosphere,
Mars has a very thin atmosphere.
Earth is warm almost everywhere,
Mars is freezing cold
almost everywhere.
So these are very different
planets.
But if you go back
into the past,
around four billion years ago,
the two planets were probably
very similar.
4.6 billion years ago
an innocuous cloud of dust
and gas
is collapsing,
forming the embryonic sun.
Swirling around it,
the remnants of the dust cloud
are slowly drawn together
by gravity...
forming eight new worlds.
Amongst them:
our smaller neighbor, Mars...
and our home planet Earth
are both rich
with elements like carbon,
metals like iron,
and, crucially, water.
But despite many similarities
at birth,
their differences in size
and distance from the sun
set them
on very different paths.
These two planets started off
very similarly.
It's what I like to call
comparative planetary evolution.
The same things could have been
happening
in the very beginning
of their existence.
And then as the clock ticks
forward geologically,
they actually become
very different from each other.
And that's the fascinating part.
What's happened since?
If they looked and acted similar
in the very beginning,
and life formed on one planet,
possibly on the other,
then what happened?
Five, four...
To find out has taken decades
of pioneering exploration.
Mariner 4 was successfully
launched on time
for its historic 228-day journey
to Mars.
Picture information started
to come in
on July 15, 1965.
During its brief flyby,
Mariner 4 gives
the first close-up glimpses
of Mars.
A revelation,
comparable to Galileo's
first view of the moon
through a telescope.
Beautiful picture.
First of all,
there are two eyes.
Not only in color
but also in stereo
and in the infrared part
of the spectrum.
Viking is the first
to successfully land on Mars.
Touchdown, we have touchdown.
Perfect set down.
And there's the first piece
of information coming in.
Oh, oh.
But the most surprising
revelations
come from the rovers...
Spirit and Opportunity.
Over 50 years
of Mars exploration
has revealed intriguing clues
suggesting Mars has
a surprisingly watery past.
There's a lot of evidence
for ancient flowing water
on Mars.
For one thing,
there's a lot of rivers
that once coursed
across the surface
that are now dry today.
There's also evidence for floods
that catastrophically scoured
the surface.
It's undeniable
that the early history of Mars
was much wetter
than it is today.
The surface of Mars is littered
with an uncountable number
of little round things.
These blueberries,
as we nicknamed them,
are what geologists called
concretions.
Concretions form typically
in sedimentary rocks
that are soaked
with liquid water.
And so what those blueberries
told us
was that this was a place where
the ground was once soaked.
It might not have been as wet
as the earth.
But it was probably wet enough
for life to evolve.
What everybody wants to know
is whether or not
Mars once had life.
Were conditions on Mars
once suitable for life?
To find out,
a new generation of spacecraft
is investigating...
led by the most complex mission
to the red planet
ever attempted.
Vehicle reports entry interface.
We have two-way Doppler and
orbit around the planet Mars.
Mars has a unique set
of challenges,
compared to other places
we go with spacecraft.
Mars has an atmosphere,
but it's thin,
so it's not enough
to really slow you down.
But it is enough to burn you up
as you're trying to land.
To get Curiosity safely
to the surface of Mars,
we basically had to pull out
every trick in the book.
At 2,000 pounds,
Curiosity is one of the largest
and heaviest probes
anyone has ever attempted
to land
in the thin Martian atmosphere.
We fired rockets,
and a jet pack flew the rover
down to the surface.
We knew it landed safely
when we realized that
the wheels sensed the ground.
At that point
a signal was received,
and all of us sort of melted
in our seats,
knowing that we had successfully
landed on Mars.
Safe on Mars.
Just a few minutes
after landing,
we had the first images
come back.
It's a thrill to see images
of a new world,
you know, from eye level
for the first time.
Curiosity touches down
in Gale Crater,
the remains of
an asteroid impact
about a hundred miles wide
thought to have been home
to ancient lakes and rivers.
As we drove out
of our landing site,
we came across what looked like
an upturned sidewalk
with like
concrete kind of breaking apart
and pebbles falling out of it.
This was a rock that had been
cemented together,
and when the geologists studied
those rounded pebbles,
they realized this rock probably
was once the bed of a river
flowing on Mars, with water
maybe, like, knee-deep.
To find out if these ancient
waters had the basic ingredients
for life, or endured long enough
to support it,
requires careful analysis.
Curiosity is
a roving laboratory.
We collect samples,
by scooping it or by drilling,
that allow us to pick apart
the story
that those things hold.
61 days after landing,
Curiosity takes the first
of many scoops of soil.
Analyzing the sand and stone
across the crater
reveals something surprising.
Not only is the Martian soil
bound with water molecules,
but also a small amount
of carbon-rich organic material.
Organic matter is
actually composed of carbon.
It's carbon molecules put
together.
And that is a turning point
for us.
What we found in those rocks
is what we expected
of natural organic matter.
It's what you would expect
to find on Earth.
Finding the organic matter
is the clue
to searching for life.
And, crucially,
these ingredients are present
for millions of years.
Really, the central discovery
of the mission so far
is that there were lakes
that survived
for maybe tens of millions
of years.
And within those lakes,
there was fresh water,
there were the raw materials
that life requires.
Just beneath the surface,
amongst ephemeral droplets
of concentrated brine,
lie the raw chemical ingredients
for life...
The final tears
of a long-lost world.
For hundreds of millions
of years,
Mars is a water world,
rich with the building blocks
for life.
Rains fall, rivers run,
and in the northern hemisphere
evidence suggests water collects
in a vast sea
bigger than the Arctic Ocean
that covers a fifth
of the Martian surface.
The red planet was once blue.
But it didn't last.
The fascination to me
about the early warm, wet Mars
is not what happened,
although
that's an interesting question,
why did it dry up?
The billion-dollar question is
whether or not
Mars actually originated life
before all the water was lost.
How far along did it get?
How is how far along did
the process go
and did it go long enough
that life could have taken hold
there?
Today only one blue planet
survives.
70% of Earth's surface
is covered by oceans.
Under the waves,
up to a million species
thrive...
While on land
the rains support
Earth's delicate ecosystems...
Providing a home
for complex life to evolve.
But our planet hasn't always
been so hospitable.
The early Earth
is unrecognizable
compared to the planet
we know today.
When Earth first formed,
it was this molten body
and it probably had a crust that
was forming around the outside,
and it was moving around a lot;
it was turning
into something rocky.
And then at the same time
that the rocks are forming,
we've also got gases
in the atmosphere,
liquid water to form oceans.
Chemical analyses
of our planet's oldest rocks
reveal its atmosphere
was choked with carbon dioxide
spewing from myriad
active volcanoes...
Making its newly formed
oceans acidic.
Early Earth was
a very different place
from today's Earth.
So if one looked at Earth
from another solar system
and asked, "Is Earth alive?"
it would have been hard to tell
four billion years ago.
And then everything changed,
and chaos ensued.
Clues as to what happened next
can be seen when the moon rises
in the night sky above us.
Etched into the moon's surface
are vast areas of impact craters
and lava fields...
traces of a violent past
revealed by the lunar landings.
Two, one, zero...
Over three years,
Apollo astronauts take samples
from across the moon's surface.
The age of the rocks
they collect
suggests the majority
of the craters form
in a narrow window of time
peaking 3.9 billion years ago.
And traveling
to the far side of the moon...
a side we never see from Earth,
reveal even more.
Countless craters,
a permanent record
of a ferocious bombardment
unleashed throughout
the inner solar system
thought to date
from the most violent period
since the planets themselves
formed,
known as the
Late Heavy Bombardment.
This Late Heavy Bombardment
turns out to be a critical event
in the history
especially
of the terrestrial planets.
All of the rocky planets were
being hit by other rocks
from other places
in the solar system.
Around four billion years ago,
while the outer planets are
settling into their orbits,
it's thought they disrupt
a cloud of icy objects
circling the edges of the
developing solar system...
sending many hurtling inwards
toward the sun.
And so these fragments
and pieces of rock
all arrive
at about the same time
in the inner part
of the solar system
to hit the planets like
Mercury, Venus, Mars,
Earth, and the moon.
Imagine meteorites hitting
on a regular basis.
It caused turmoil on the surface
of all those planets.
They basically hit
with such energy
that they resurface the planets.
As rocky asteroids fragment
in Mars's atmosphere,
havoc rains on every corner
of the planet.
Based on the rates of crater
formation on the moon,
it's thought at least 50 tons
of rock fall
for every square meter
of Mars's surface
in a hard rain that lasts
tens of millions of years.
Over a third of the
planet's crust is resurfaced...
as Mars descends into chaos.
Earth suffers the onslaught
just as Mars does...
relentlessly smashed
by falling rock.
Both young planets endure
a catastrophic pounding.
But just when conditions appear
at their least promising
on Earth,
the raw organic materials on
its surface come together...
To produce its most
precious creation...
Life.
The kind of environment
that's needed for life to start,
we need to be converting
the first organic molecules
to whole cells.
And those kind of conditions
require a dynamic geological
environment,
and that kind of environment
would have been everywhere
on the early Earth.
The volatile conditions on Earth
may be responsible
for turning the simple organic
molecules already present
into complex organic material
capable of replicating itself...
We don't know precisely
where life started.
It could have been an
environment like this,
a terrestrial geothermal system.
It could have been even
delivered from space,
perhaps organic molecules
delivered
into exactly
this kind of setting.
To me it seems more likely that
it started under the oceans
in deep-sea hydrothermal vents.
Volcanic activity erupting deep
in the oceans
would create
a high-energy system.
That pressure makes reactions
happen faster
and more likely to give rise
to life.
And the emergence of life
need not be limited
to just one planet.
Life should really start
wherever these geologically
active conditions are met,
where we have a continuous
bubbling of gases
from in the bowels of the planet
or the moon,
to react with gases in
the atmosphere or in the oceans.
These conditions are
very similar
to what we think might have been
present on Mars
four billion years ago.
But how can we be sure
that catalysts for life
like this
existed on Mars that long ago?
Ignition and liftoff
of the Atlas V rocket
with MRO.
Surveying
for the deepest insights
into the mysterious evolution
of Mars.
Searching for conditions
that could kickstart life
is NASA's
Mars Reconnaissance Orbiter.
Sent to map Mars
in intricate detail,
MRO sends back more data
than all other Mars missions
combined.
MRO has three cameras on board.
The first is
the MARCI weather camera.
It sees horizon to horizon
on every orbit,
so it builds up a map of
the entire planet every day.
So you can see a global
weather map ever day on Mars.
The second camera is
the context camera.
It provides high resolution,
and it's covered
about 99% of the surface.
MRO has made
more than 60,000 orbits...
Its high-resolution cameras
revealing Mars
in unprecedented detail...
Discovering polar avalanches,
shifting sand dunes,
and what look like
seasonal flows of sand
or even liquid meltwater.
Then, in 2017,
MRO turns its gaze
to some of the red planet's
oldest rocks:
in the Eridania Basin,
thought to have once been home
to an ancient sea.
Eridania Basin is a huge basin
in some of the
most ancient crust on Mars.
It formed
about 3.8 billion years ago,
and it held more water
than ten times that
of the Great Lakes
or three times that
of the Caspian Sea on Earth.
And it's on this ancient seabed
that MRO sees something
remarkable...
a potential catalyst for life.
MRO saw a massive,
400-meter-thick deposit
formed from a mineral
that forms in deep-sea
hydrothermal environments,
such as one that might have
undersea vents.
Analysis shows the deposits are
rich with saponite,
a mineral found on Earth
at hydrothermal vents...
suggesting in the past
Mars not only had the same
ingredients for life as Earth
but also an active environment
to spark it into action.
Eridania Basin was
an ancient sea
3.7 to 3.8 billion years ago.
And that's about the same time
when life was first emerging
on Earth.
This might have been a place
where life could have existed,
because those hydrothermal vents
underneath that sea
might have created a very
conducive environment for life.
These initial conditions
in the history of both planets
look so similar that
it seems reasonable to expect
that this could
eventually lead to life.
These actively fertile
conditions
are thought to survive in
places like the Eridania Basin
for hundreds of millions
of years,
with Mars, like Earth, rich
with the potential for life.
But then, 3.7 billion years ago,
something happens
that transforms prospects
for life on Mars forever.
Analysis
of the ancient Martian surface
reveals a dramatic change.
Mars underwent through a fairly
substantial transformation
in its climate.
The climate got colder.
What liquid water there was
either soaked into the ground
and froze
or froze at the surface.
A lot of it ultimately would get
transported to the poles,
where it forms these big,
thick icecaps
that we see today.
At the same time
as the temperature plummets...
Mars becomes
more volcanically active...
leading to catastrophic flooding
with water raging
for hundreds of miles.
Until, in a place known
as Echus Chasma,
it plunges over cliffs
two-and-half miles high...
Creating the largest waterfall
the solar system has ever
seen...
Cascading
into a spectacular canyon
six miles wide
and 60 miles long.
Once the floods subside,
the water disappears,
the only trace it ever existed
etched into
the planet's surface.
So what causes
this dramatic change in climate?
That's being investigated
by NASA's most active
Mars orbiter.
T-minus ten, nine, eight, seven,
six, five, four,
three, two, one.
Main engines start,
ignition, and lift off
of the Atlas V with MAVEN,
looking for clues
about the evolution of Mars
through its atmosphere.
In September 2014,
NASA's MAVEN probe is on
its final approach
to the red planet.
Its mission:
to understand the processes
that transformed Mars.
We know that the Mars climate
has changed through time.
The geological evidence tells us
there was lots of water
early on,
and that it's been cold and dry
in the last couple
of billion years.
Maven was sent there
to understand what processes
drove this climate change.
Based on observed
navigation data,
congratulations.
MAVEN flies in an elliptical
orbit around the planet.
At its lowest point,
it's only 150 kilometers
above the surface.
At its highest point,
it's over 6,000 kilometers.
That means that on every orbit,
we're able to measure
the full profile
of the entire upper atmosphere.
The previous missions
we've sent had cameras
to look at the geology
of the surface
or the behavior of the clouds
and dust
in the lower atmosphere.
We're making measurements
in the upper atmosphere,
where we're more interested
in the behavior of atoms
and molecules,
so our instruments are focused
on taking measurements of those.
MAVEN carries an array
of instruments
designed to measure the behavior
of atoms and molecules
in Mars's atmosphere.
From the measurements
that MAVEN has made now
over an entire Martian year,
we've confirmed that gas is
being lost to space today
out of the atmosphere.
And it's being lost at a rate
of about two to three kilograms
every second.
By measuring the gas being
stripped from its atmosphere,
MAVEN is witnessing the process
that transformed Mars's climate
over three-and-a-half
billion years ago.
We think that this stripping
of the atmosphere over time
has been responsible
for the change in climate
which Mars has suffered.
Mars lost much of its water
and the atmosphere
that insulated it
from the cold of space...
leaving it frozen and dry.
So what was it that sent Mars
down such a different path
from Earth?
The sun's outer corona burns at
a scorching one million degrees.
It releases a barrage
of charged particles that travel
at hundreds of miles a second...
The solar wind.
This onslaught would strip away
our atmosphere,
but for the powerful magnetic
field that protects us
The solar wind is
this stream of charged particles
that come streaming out
from the sun.
And at Earth,
which has
a powerful magnetic field,
when those charged particles
begin to get close to Earth,
they get diverted around Earth
by interactions
with that magnetic field.
That protection keeps solar wind
and other ionizing radiation
off of the surface.
So on Earth,
where we have this really great
magnetic field,
we are nice, safe, and sound
inside the shell of that,
protected
from all that radiation.
The magnetic field of Earth
effectively forms
a protective bubble
around the Earth's atmosphere.
And when the sun dips
below the horizon,
there are times when Earth's
protective force field
is visible.
The aurora is a stunning display
of Earth's magnetic field
in action.
It's best seen at the poles,
but across Earth
it's protecting our atmosphere
and all life on our planet.
This vital protective shield
is generated deep within.
The way a magnetic field is
generated inside a planet
is when you have
convective motion
in a fluid that is capable
of conducting electricity.
And in the Earth, that
electrically conducting fluid
is liquid iron.
And the molten portion
of the Earth's core
is a place where these motions
take place,
and it can set up
a magnetic field.
Just like Earth,
Mars once had
a molten metallic core,
generating a magnetic field
around the planet.
Auroras danced
above Mars's poles...
protecting its atmosphere
and seas below.
But the field didn't last.
In the oldest rocks on Mars,
you see evidence of
a once-powerful magnetic field.
You get to the younger rocks,
the rocks that are
three billion, two billion,
one billion years old,
no evidence of a magnetic field
whatsoever.
And there is no intrinsic
magnetic field on Mars today.
This invisible magnetic field
around the planet,
something we can't see,
it's like this layer of
protection around the planet...
disappeared.
Half a billion years
after it formed,
Mars's magnetic field dies out.
The bright auroras above
its poles slowly fade away...
As the shield
that protects the planet
shuts down for good.
Once it stops,
then what happens is
all the atmospheric components,
things like hydrogen and oxygen
that make up water,
they get stripped away
because you don't have
the shield,
the magnetic shield anymore.
So the high-energy particles
that come in from the sun
and from outer space,
they begin to strip away the
components that make up water.
Without its magnetic field
to protect it,
Mars's atmosphere and then water
slip away into space.
So why did Mars lose
its protective shield?
What happened
deep beneath its surface
that stopped Mars from
developing like Earth?
The answer lies at the beginning
of Mars's story...
at its very creation.
4.6 billion years ago,
when the planets were forming
from the dust cloud
circling the sun,
early differences
between Mars and Earth
set the young planets
on very different paths.
Crucially, Mars forms farther
from the sun,
where there is simply
less rocky material
to build a planet.
Mars is different
because it's not
just further out,
it's actually much smaller.
If a planet gets to be
too small,
it just freezes
all the way through.
Because Mars is so much smaller,
there's less thermal energy
coming from the interior
of the planet.
The planet is fundamentally
different
from the interior out,
and that is what separates Mars
from Earth.
It's this critical
size difference
that seals Mars's fate
and shapes its surprising story.
Four-and-a-half billion
years ago,
two young planets are born.
Initially inhospitable
and toxic...
both young planet develop
into warm, watery worlds.
They both survive the violence
of the Late Heavy Bombardment...
Emerging as mature planets,
primed with all the ingredients
for life to begin.
But while Mars appears
to be thriving,
deep in its cooling core,
the planet is dying.
Its once-great ocean is lost
to space.
One by one,
its volcanoes go out.
As the lava turns to stone,
all hope of recovery is
extinguished.
Today, Mars traces a lonely path
through the solar system,
rusted and gathering dust.
But this is far from the end
of what we hope to discover.
The next generation
of spacecraft
will soon be on their way...
with missions like
European Space Agency's ExoMars
and Mars 2020 searching
for signs of life...
And NASA's Orion,
currently undergoing
advance testing...
NASA's first step toward
sending humans to Mars.
My hopes for the future
eventually there's boot-prints
on the surface.
You know, humans on the surface
doing what humans do... explore.
Humans are going to go to Mars.
I can't wait to see someone else
not virtually explore Mars
but really explore Mars,
as a human being,
walking on the surface.
Future generations will be able
to look closer than ever before
for evidence of life.
So the next step is to search
for life on Mars.
We're probably going
to bring samples home.
We'll study them here, and
we'll learn all sorts of things
about ancient Mars
and even modern Mars.
And if we do find life on Mars,
the consequences will be
profound.
If you could show that
life independently took hold,
independently,
on two different worlds
just in this one solar system,
then when you consider the
multitude of planetary systems
that we now know are out there,
it takes no great leap
of imagination, faith,
or anything else
to believe that life could be
a universal phenomenon.
It's a situation where two is
a much bigger number than one.
I think if one was
to ever discover life
anywhere outside of Earth,
it opens up the possibility that
the universe is full of life.
Because if you find just
one example in our solar system,
now you imagine
all the solar systems
that have been discovered
that we call exoplanets,
and then you multiply
these things,
and it must mean
that life is everywhere.
I often wonder
how the world would react
if we found life on Mars.
For me personally,
it almost feels like
we're reaching the point
where it would be more
surprising not to find life.
I think it still would shock
all of us,
and we'd be amazed that
such a discovery was made,
but I've personally come to
think that life must be present
all over the universe,
and maybe even on a planet
as close as Mars.
Major funding for "NOVA"
is provided by the following:
Half a billion miles
from the sun...
Jupiter is very violent
and it's very intimidating.
The giant of the planets.
Transforming the destiny
of the solar system.
The most powerful
gravitational object
second to the sun.
"The Planets: Jupiter,"
next time on "NOVA."
I'm losing sight of our reality
I'm losing sight of our reality
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