Horizon (1964–…): Season 37, Episode 11 - Life on Mars - full transcript
In the last few months
a probe orbiting Mars
has sent back
astonishing pictures
which have rekindled
the search for life.
Billions of years ago
did a river flow through this canyon?
If these gullies were
created by water
and if this was once a lake
then there is every chance
we will one day find signs of life on Mars.
Ever since humans first realised
there might be life elsewhere in the universe
we've dreamed
of aliens on Mars.
Finding even a primitive life form
would be one of the most important
discoveries of all time.
I think the search for life on Mars
is a perfect scientific question
because either answer is
so philosophically profound and interesting.
If we found life on Mars
it would mean there's likely
to be life throughout the universe
and if Mars is barren
then maybe the rest
of space is too.
Maybe life on Earth is unique.
Could life have started on Mars?
If it didn't
and the environment was right,
why not, what, what,
what was wrong with it?
Did it take some chance
in a billion random event to occur,
or if it did happen
what happened to it, how come
there are not Martians running around.
But there's an even more
amazing possibility.
Occasionally Mars is hit
by such violent impacts
that the debris is blasted
right out into space.
One of these rocks could have been
the origin of life on Earth billions of years ago.
Maybe actually life
started on Mars
and came to Earth
via these meteorites.
Maybe in fact we're all Martians.
I mean you can ask one of the most fundamental
questions that scientists can ask:
are we alone in the universe?
What's the frequency
of life in the universe?
For a planet to support life
there is one vital ingredient
it must have,
one special substance
which any alien anywhere will need.
The search for life
is the search for water.
Life involves complex
chemical reactions
and as far as we know,
complex chemistry needs water.
Liquid water is the absolute key, fundamental,
one and only must have it requirement for life.
No liquid water, no life.
It's just as simple as that.
Mars seems an unlikely place
to look for life.
It's far too cold for water.
Temperatures can be
minus 100 degrees
and there's virtually
no atmosphere
so every trace of moisture
is sucked out into space.
Unprotected a human being
would last just a few seconds,
but it seems that Mars
was once far more hospitable.
In 1969 NASA launched the first ever probe
to go into orbit around Mars.
When Mariner 9 arrived it found the planet
completely shrouded in a massive dust storm.
For a month they waited
for the dust to clear.
As soon as the images
started coming back from Mariner 9
people began to get
a really different picture of Mars.
Everyone had expected to see
a dead ball of rock like the Moon,
but slowly they started seeing signs
that Mars had once been very active.
The first thing that emerged
was this crater
that must have been 20 km above the surface
because it was in the middle of the atmosphere,
so it was like wow,
there's something really big there
that is sticking
up into the atmosphere
and above the atmosphere
and in fact is volcanic
so all of a sudden
it wasn't like the Moon at all.
And then they saw something
even more amazing
- what looked like
dried up river valleys.
That was a complete surprise.
I mean this was supposed
to be a dry, frozen planet
and here we have evidence of things
that look like old river beds.
And it completely changed
people's view of Mars in that sense
back to something that might
have been more Earth-like in the past
and much more dynamic than the Moon.
If these were dried up river beds
it meant that Mars must once have had
the perfect conditions for life.
Rivers form from streams,
streams are fed by rain,
rain falls from clouds
and clouds mean an atmosphere.
Mars must once have been
like the Earth is today,
if these were rivers.
The pictures from Mariner
just weren't clear enough to be sure.
Five years later the Viking orbiters
arrived with better cameras.
Some of these valleys had faint tributaries
just like rivers on Earth.
And these really look
like terrestrial river valleys
when you look at them
and you can see one here.
You can see there's
a, a valley through here
and you can see it branches,
there are tributaries.
Here's one branch going off
here with tributaries,
so this looks very much
like a terrestrial river system.
But many scientists just wouldn't accept
that rivers had once flowed on Mars.
The Viking images still weren't
good enough to settle the argument.
Then in 1998
Mars Global Surveyor arrived
equipped with the latest
high resolution electronic cameras.
Sections of the valleys
were revealed in fantastic detail,
but these amazing pictures
were still no use.
These valleys had all been
eroded and filled in with sand.
It was impossible to say
how they'd been formed.
Then, after they'd searched
through thousands of images,
they struck gold,
a winding valley
two kilometres wide
and at a bend in the canyon
a tiny channel,
the unmistakable trace
of an ancient river.
This is the best evidence
that we have
that climate in the past was different
from what it is today,
that there were warmer conditions
on Mars.
So Mars must once have been
warm and wet like the Earth.
It had rain and flowing rivers.
Then at some point the atmosphere
must have thinned and the planet cooled.
The flowing rivers
iced over and froze.
But when did the rivers
stop flowing?
Was there time enough
for life to emerge
before the last traces
of liquid water vanished from Mars?
The river valleys
are pockmarked with craters,
so they must have formed
billions of years ago
during the beginning
of the planet's history
when Mars was still
being bombarded with meteors,
but there are other features
carved into the surface more recently
which tell a very different story
about water on Mars
- giant channels stretching
for thousands of kilometres.
Well you see on this image
a fairly typical example
and you can see the channel
on this picture here.
Here's one side
of the channel,
here's the outline, you can see the sort
of eastern shore of the channel here
and there's the other side
of the channel.
These channels are enormous.
This crater here is 60 km across,
so you can see that the, the channel
down here is, is 200 km across,
so what happened, there was a lot of
speculation as to how these channels formed.
We, we looked into
the possibility of lava,
could lava cut a channel like this?
Liquid hydrocarbons,
liquid carbon dioxide,
and of course water.
Water seemed
the most likely explanation,
but how could anyone be sure
what had carved these monster channels.
For years scientists have been
searching for clues on Earth.
American geologist Jim Rice
thinks he's found them, in Iceland.
Buried under vast glaciers are some
of the most active volcanoes in the world.
It's a powerful combination
which had shaped the entire landscape.
When a volcano erupts
lakes of steaming melt water
form high up on top of the glacier
until the enormous weight
of water forces its way down
bursting out from the base
of the glacier.
These are the biggest floods
on earth,
a surging wall of water
stretching for kilometres.
In their wake they leave
vast plains littered with boulders.
To a geologist
these boulder fields contain unmistakable evidence
of the flood waters that ripped through here.
OK, well this is really
a classic textbook example.
These two large boulders here.
The size of them indicates
this was an enormous flood,
the deposit of these features,
but also if you look
at their geometry
these boulders are kind
of dipping back in this direction.
This has given us information about the path
the flood waters took that deposited these boulders.
The flood waters were going in this direction
where these rocks were deposited.
Now there's other interesting things
in the scene here.
For instance you notice some
of these smaller rocks are very well rounded
and these little nicked corners
of these boulders here.
These are called
percussion marks
and these are produced in the water,
highly turbulent water column
when the boulders
and rocks basically slam into one another
knocking the corners off.
These things all group together
just tell you there's no doubt
this was a catastrophic flood deposit.
Four years ago the Americans
sent a probe to land on Mars.
It was aimed at the middle
of one of these vast channels.
For the first time we'd see
what these strange features looked like
from close up on the ground.
The answer was obvious.
The first view of the landing site
sent back by the cameras on Pathfinder
revealed a rock-strewn plain
just like the boulder fields
left by catastrophic floods on Earth.
Here were the slanting boulders
lined up by the flood waters
and the cameras on the rover provided
detailed views of the individual rocks
with their telltale chipped edges.
We saw perched rocks that were kind
of sitting on a very small little,
as if it had been deposited
by this flood and actually scoured
as water had run past it,
so a whole suite
of things like that.
Observational evidence
very, very strongly argues
that, that this site is exactly
what we thought it would be from orbit.
Pathfinder confirmed that the vast Martian channels
had been carved by enormous floods,
so what does this mean
for the chances of finding life?
Some of these floods seem
to be quite recent,
so did Mars remain warm and wet
for billions of years?
Well that depends on
what caused these giant floods.
They stop almost instantaneously
in rubble-filled holes
with a channel coming out
and going off to the north
and so that suggested
that whatever caused the large channels
it was, it erupted
from the ground.
Mike Carr's theory is that these floods
are actually a sign that Mars was very cold.
Deep underground
geothermal heating melted ice.
For millions of years
the water built up
trapped under pressure
by a thick layer of permafrost,
until something broke the crust.
A vast reservoir of melt water
is released and surges out of the ground.
As the water rushes out it would rush out
so violent that it pulled a rock,
the aquifer, with it
so you'd have both rock
and water coming out
and then after
the flood was over
why the ground would collapse to form
this rubble-filled hole that we see.
To Mike Carr these floods are evidence
that Mars has been deep frozen for billions of years.
I actually believe that cold climates
are required to make these large flows.
You can't get the large flows
without this thick permafrost zone
that keeps the water in the ground
and doesn't allow it to get out.
So Mars might have been frozen
for almost its entire history
with violent floods periodically
bursting out from beneath the permafrost,
so what does that mean
for the chances of finding life?
Well that depends on
one other fundamental question.
The question you have to ask is
after these enormous floods
what was the fate of that water?
The floods on Mars were thousands of times
bigger than anything on Earth today.
Where did all the water go?
The channels flow downhill
into a giant basin around the north pole.
Did the floods just
fizzle out and freeze
or were they big enough
to fill this entire basin?
Did they form
an ice covered ocean
which could have sheltered
life for millions of years?
NASA's Tim Parker is convinced
there was an ocean on Mars.
His evidence comes
from features carved by a giant lake
which once filled
an enormous area of southern Utah.
We're flying over the, the floor
of an ancient lake
called Lake Bonneville that covered
about half the state of Utah
when it was at its maximum level
about 10,000 years ago.
The best evidence
that there was a lake here
is the erosion that occurred
at the margin of the lake, the shorelines.
Waves beating on the mountains
and, and cutting cliffs
and depositing ridges,
beach ridges along the margin.
One of the most dramatic features
is the flat terrace in the side
of this volcano cut by the water.
It's a clear sign this was once
an island in the middle of a giant lake.
Tim believes he's seen
similar features on Mars,
flat terraces around rocky
outcrops in the northern basin
formed by the pounding
of the ocean waves
and around the edge
of the basin
Tim believes the old Viking images
show two faint shorelines
stretching for thousands
of kilometres.
He suggested these were cut
by a shrinking ocean
which might have existed
for a billion years,
but he had no way
to prove it.
Then last year Global Surveyor beamed back
the first detailed contour map of Mars.
What we're looking at here
is a view of the northern hemisphere.
We're looking straight down
on the pole and this is the pole.
What the colours represent
are elevations.
This red here is the area of Tharsis
where there are huge volcanoes
and this one, Olympus Mons, is
2 and a half times the height of Mount Everest.
It's a huge volcano.
Now the large outflow channels,
the largest ones are over here.
The water came through here
and down into the low areas
here which are coloured blue.
Now Jim Head could check
the height of Tim Parker's proposed shorelines.
A standing body of water
forms a flat surface,
so shorelines should be level
along their entire length.
The outer line, called contact 1,
turned out to be extremely uneven,
but contact 2 seemed
much more like a shoreline.
The younger contact, contact 2,
was a much closer approximation to a flat line.
It, it had bumps
and wiggles as well,
but in many places
it was really straight
and corresponded to the place
where Parker had mapped the contact.
But not everyone is persuaded.
Last year the first close-up pictures
of the edge of the basin came back from Mars
and there's nothing
that looks like a shoreline.
I do not find the evidence
of these oceans convincing.
I would expect to be able
to see something
because the original shorelines
were depicted on the basis of imaging
and yet when we go back
and get better imaging
of the, of the places
where the shorelines have been mapped
we're not seeing
the shoreline there.
But even on Earth evidence of shorelines
can disappear when you get too close.
The terrace cut into the volcano
by Lake Bonneville
just becomes a stretch
of flat ground
which means nothing
this close in.
The argument goes on,
but perhaps life didn't need
a whole ocean to get started.
Just a few weeks ago
NASA released one of the most
important pictures ever taken of Mars.
Layered rocks in a basin
hundred of kilometres across,
probably formed by the slow
build up of sediments in a lake.
Did this lake last long
enough for life to evolve?
Might these sediments
contain fossilised Martians?
I think life would get started probably
in a few hundred or perhaps 1,000 years
so I don't think that we need huge amounts
of time to, to worry about the origin of life.
We don't, life kicks in
I think pretty rapidly.
On Earth it was
about one billion years
after the planet formed
from a mass of molten rock
that the first microscopic
fossils appear,
but no one actually knows
how long it took the first living things
to develop from the primordial soup.
One needs millions to billions
of years for evolution,
but for the actual onset of life
I don't think you need much time.
I can look at Mars
and think that this is a typical
rocky, wet, sunny planet
and life would have inevitably
started on such a planet.
Many scientists now believe that if life
did emerge billions of years ago before Mars froze,
craters once filled with water
are the best place to look
and there's one which stands out.
30 years ago NASA published pictures
of a strange formation of white rock
in the bottom
of a crater 90 km across.
I just clocked the fact
that it had been published
and I thought it was
a very interesting paper
but I wasn't particularly
interested in Mars at the time.
It just rather made us
think in a particular way.
During a trip
to central Turkey
Mike Russell stumbled
across a lake
which made him think again
about the white rocks on Mars.
Near the southern shore
Mike spotted strange white islands
and decided
to investigate further.
Well these particular structures
are probably only a few decades old
and the lake has dropped level
in the last 30 or 40 years or so.
It's really exciting
to come back here.
I, I first came out here, I swam out here in 1992
and I couldn't believe my eyes because
we'd been led to believe these were sand-dunes.
Mike Russell discovered these islands
were actually something far more extraordinary.
These rocks had been built
by microscopic organisms.
Photosynthetic bacteria,
the most primitive
life form on earth,
exactly the kind of creature
you'd expect to find on Mars.
From then on we started to think well,
could there have been life on Mars in these craters
and could it be that some of these white
rocks could have been formed by bacteria.
This lake showed that bacteria
can build huge rock formations
and as it happened these white rocks
were made of magnesium carbonate,
exactly what you'd expect on Mars
which has magnesium-rich soil.
So could this mysterious
white formation
be a sign that life evolved
in this crater long ago?
There will be vestiges of water
in craters, in lakes and so forth
on Mars for perhaps 500 million years
and that is absolutely plenty of time
to evolve photosynthetic bacteria,
so I would expect us to find eventually
evidence for photosynthetic bacteria on Mars.
And wherever they first appeared
they could have quickly
colonised the entire planet.
Of course that bacteria
can get anywhere.
It can last a long time,
they can get blown by winds
from here and there,
so any standing body of water on Mars
would have captured some of this,
some of these early bacteria
and they would have then
colonised any seepages
in any of these crater
lakes on Mars.
Last year the camera orbiting Mars sent back
the first close-up pictures of the white rocks.
Could these have been islands in a lake
teeming with bacteria
or are they just sand-dunes sculpted
and compacted by the Martian winds?
The only way we'll know for sure
is when we land a probe right on them.
As scientists have pieced
together the tantalising clues
it seems more and more likely
that early in its history
there could well have been life on Mars,
but what chance is there that
anything could still be alive there today?
If it ever started then the chance
of it surviving up to today
is pretty good because life somehow finds
niches and adapts to whatever's there.
Until a few years ago
it didn't seem likely that anything could
survive being deep frozen for billions of years,
but research in one of the coldest places
on earth has helped changed that.
In northern Siberia the brief summer sun
breaks up the pack ice and thaws the rivers,
but just below the surface
the ground stays permanently frozen.
Every year a team of Russian scientists
comes here to drill into the permafrost
in search of micro organisms.
People found the micro-organisms
in permafrost in the end of 19th century.
It was done specially in Russia
when people found mammoths.
Back then it was
the mammoth they were after,
but David Gilichinsky's team
have found bacteria and algae
which have been frozen underground
for an astonishing length of time.
The deeper they go
the older the permafrost.
The frozen cores are taken
to their laboratory near Moscow.
A sample is taken
from the centre of the core.
Then they see
if anything's still alive.
They've discovered that bacteria
can survive in the permafrost
for far longer than anyone
had thought possible.
When they started it was surprise for us
when they find even 10,000 years old bacteria,
but step by step you can come in Arctic
two or three million years old.
These micro-organisms have been living off
the minute amounts of liquid water
which exist even in permafrost,
so could they survive indefinitely?
In Antarctica the ground
is even colder than Siberia
and it's been frozen
for much longer.
This is the closest place
on earth to conditions on Mars.
The Russians have now teamed up
with NASA scientists to drill here.
A few months ago
they found bacteria
which may turn out to have been
at -20 degrees for more than 10 million years.
We have some data,
but we are not sure 100%
but probably we have now these alleged
bacteria from Antarctic permafrost.
It's between 8
and 15 million years old.
Bacteria had been buried
here in frozen ground
since before the beginning
of human evolution.
If life can survive
in Antarctica for 15 million years
then something could be waiting
to be revived on Mars
and last summer Mars Global Surveyor
sent back another extraordinary set of pictures
which suggests that in places
the Martian permafrost has been melting.
The camera has detected hundreds
of examples of cliff sides on Mars
with little gullies
running down the cliffs.
Now these look exactly
like gullies
that would form on the Earth
when, when an underground aquifer
comes out the side of a cliff,
a little bit of water comes out,
runs down the gully,
makes a seep, it just
keeps eroding down there.
These cases on Mars you have
a gully running down,
then you, in many cases you even have
a little mud-like deposit at the bottom.
These gullies must
be very recent.
There's no sign
of any erosion by the wind,
so if they were carved by water
our whole view of Mars
would have to change.
It means there could be liquid water
just below the surface right now.
The temperature here typically is
-60, -70, -80 degrees centigrade.
It's extremely cold,
so it's hard to imagine how one
could have seepages of water
under these very cold,
very cold conditions.
Any water seeping from below would freeze
long before it reached the surface,
but perhaps the water
could build up underground,
trapped by a thick
plug of ice
until the pressure gets so great
that the water forces a way out,
gushing so fast that even
in the icy Martian conditions
it could carve a gully
before freezing again.
Bill Hartmann believes he's found signs
of what could be melting the water underground.
His team have discovered that volcanoes on Mars
have erupted more recently than anyone had expected.
The most recent lava flows may be
less than a million years old.
For every time that you heat up
the crust of Mars enough to melt rock,
that's 1200 degrees centigrade,
I mean there could be
a thousand times
when you heat it up to zero
degrees centigrade and melt ice.
It's not out of the question
in my mind
that some of these seeps
have been active 1,000 years ago,
10,000 years ago, 100,000 years ago,
numbers like that,
or maybe more recently, you know,
maybe it was six months ago.
If there is still water
erupting on Mars
the implications for the history
of life are fantastic.
I'll spin the, the most
glorious optimistic scenario
which would be that
the geothermal heating from below
has for 4 billion years,
the entire history of Mars,
has, has kept open some liquid
water channels some place on Mars
so there's always been some place
you could swim from this place to that place.
If there has been water
on Mars for 4 billion years
what strange creatures
might be waiting for us?
If this discovery is confirmed,
it will surely be one of the most stunning insights
into our universe that science has ever uncovered.
The events of that week
in August 1996
are burned indelibly
on my brain
and I will never forget
them until my dying day.
Four years ago
a team of American scientists claimed
they had found evidence of microscopic life
in a meteorite that had come from Mars.
Allan Hills 84001 has become the most
intensively studied rock in the world
because proving that this rock contained life
from Mars has turned out to be very difficult.
What I would like
to do this afternoon is
lead you through our story
which is a bit of a detective story.
In 1994 geologists heard about
a new meteorite which had come from Mars.
We requested three
or four small fragments,
small chips about the size
of my fingernail.
Monica Grady's team in London
found unusually large amounts
of carbonate in the Allan Hills meteorite
which formed orange globules
in the rock.
Carbonates can sometimes
be produced by living things,
but the finding didn't
mean much on its own.
Then David McKay's team
at NASA took a closer look.
We were looking,
scanning around
in our electron microscope
looking at Allan Hills
and we particularly looking
at the carbonates.
There were a lot of rumours
and, and mutterings in corners
about the possibility
of something unusual
having been found
in this meteorite,
but nobody would say
for definite.
And I started to see some features
in Allan Hills which were very strange,
somewhat elongated features
that had segments in them.
The next day we found a few more
of 'em and we really got excited.
They thought they'd found
a tiny fossilised Martian.
This is perhaps the most
controversial part of our presentation,
but we'll show you
those anyway.
Anybody else who'd seen
Allan Hills 84001, who'd analysed it,
who'd even had a grandma
who's seen 84001 was being interviewed
to, to get their, their take
on, on what had happened.
The scientists will lay
out for you
how an ancient rock found
its way from Mars and it got to Earth.
The first time I saw
the worm-like structure
was at the press conference
that the NASA scientists had.
Martian micro fossils.
And I must admit I was
pretty amazed at the structure.
It is 41 billion years old.
It looks like a segmented worm,
it looks like you might think
a fossilised bacterium would look like,
but then you realise well,
crumbs, it's very small.
It means we're right
on the edge
of a potential unbelievable discovery
that's going to rock our world,
rock our world,
if it's true.
When McKay's team analysed
the rock surrounding their worm
they found three different substances
often produced by bacteria on earth.
These substances could all
be explained without life,
but McKay had a theory which would
explain why they were all there together.
Ours was the only one
that could explain everything
simultaneously with the same
simple explanation,
that is life on Mars.
They are the remains
of Martian life.
Is the fact that six things are
consistent with the presence of life
enough to convince you
that you're making one of the,
the most sensational claims ever made
and I would say no,
that, that what you need is evidence
that requires life to explain it.
This may look
like a Martian worm,
but Ken Nealson has shown how deceptive
appearances can be at this minute scale.
The pictures
of the Allan Hills meteorite
were taken using
an electron microscope
and to get the best images
the rock sample was coated
with an extremely thin layer of gold.
Nealson's team have been looking at rock
with a new kind of electron microscope.
This one can work
without the gold coating.
To my way of thinking
it's very impressive
how different the samples are
when they're coated
with gold or not coated.
His uncoated rocks looked jagged
and crystalline at high magnification,
but add the gold coating
and tiny blobs appear
which are about the same size
as the famous Martian worm.
The edges now can be
rounded off with the gold
and even an expert could
be fooled.
You'll look at it and you'll say
wow, you know that could be life.
So this might just
be rock fragments
made to look like a worm
by a thin coating of gold.
To prove it was once alive
you have to find out
what it's made of.
In California Ken Nealson's team have been
developing the kind of techniques
which may one day be needed to probe
Martian rocks for microscopic life.
Their system works by firing
a fine beam of electrons at the sample
and it's astonishingly precise.
They can find out what even the tiniest
microscopic structures are made of,
how much of each chemical
element the sample contains.
The first tests on the famous
Allan Hills worm
suggest it has exactly the same
composition as the surrounding rock.
If that's the case
this was never living.
The search for life on Mars began
25 years ago with the Viking missions.
Two landers touched down
and scooped up a sample of the Martian
soil for chemical analysis.
The billion dollar robots
worked perfectly,
but they failed
to find proof of life.
The Americans now realise
that solving one of the greatest
scientific mysteries
could never be
that straightforward.
We sent two spacecraft
which had extremely sophisticated
life detection experiments
and they came back negative.
You don't need to go and land
and poke your arm
in and pull out soil
and say is there a life
eating chicken soup there?
It's not, you know, that,
we already did that
and in a sense
we didn't learn as much.
We, maybe, maybe,
and this is arguable certainly,
maybe we asked too specific
a question too soon.
In 2003 the next missions
will be heading for Mars.
The Europeans have chosen to send the Beagle
probe to scratch the surface looking for life,
but NASA will be taking
a giant leap backwards.
The new rovers they're testing
at the Mars yard
will not be looking
for life.
They're just designed to gather basic information
about the geological history of the planet.
The rovers that we're sending
have no life detection experiments.
That's not the point.
We've landed three
places on Mars
and those three places are all
in the northern lowlands,
they're all kind
of the same.
Well let's go see what the southern
highlands are, what are they?
Let's go land in places
that have these unique signatures,
let's go see
what Mars is really about.
Rockets on the back shelf:
fire!
NASA is planning an armada
of increasingly complex missions.
Three, two, one, release!
Oh, sweet.
When they've scoured
every inch of Mars
and they've identified
the one place on the planet
which is most likely
to answer the question
then they'll be ready
to look for life.
Get that kind of information,
get that broad understanding first
before you go in
to ask the specific question,
so I think that's, that's
a noble question to try to answer -
is there life on Mars today,
but it's one that you
dare not ask directly
for maybe 20 years,
maybe 30 years, maybe even more.
The search for life on Mars
may turn out to be one of the hardest
problems science has ever faced.
Perhaps it's a question no machine
will ever be able to answer.
Perhaps Mars will only
give up its secrets
when the first humans make the journey
across the Solar System.
Converted into subtitles by m06166
a probe orbiting Mars
has sent back
astonishing pictures
which have rekindled
the search for life.
Billions of years ago
did a river flow through this canyon?
If these gullies were
created by water
and if this was once a lake
then there is every chance
we will one day find signs of life on Mars.
Ever since humans first realised
there might be life elsewhere in the universe
we've dreamed
of aliens on Mars.
Finding even a primitive life form
would be one of the most important
discoveries of all time.
I think the search for life on Mars
is a perfect scientific question
because either answer is
so philosophically profound and interesting.
If we found life on Mars
it would mean there's likely
to be life throughout the universe
and if Mars is barren
then maybe the rest
of space is too.
Maybe life on Earth is unique.
Could life have started on Mars?
If it didn't
and the environment was right,
why not, what, what,
what was wrong with it?
Did it take some chance
in a billion random event to occur,
or if it did happen
what happened to it, how come
there are not Martians running around.
But there's an even more
amazing possibility.
Occasionally Mars is hit
by such violent impacts
that the debris is blasted
right out into space.
One of these rocks could have been
the origin of life on Earth billions of years ago.
Maybe actually life
started on Mars
and came to Earth
via these meteorites.
Maybe in fact we're all Martians.
I mean you can ask one of the most fundamental
questions that scientists can ask:
are we alone in the universe?
What's the frequency
of life in the universe?
For a planet to support life
there is one vital ingredient
it must have,
one special substance
which any alien anywhere will need.
The search for life
is the search for water.
Life involves complex
chemical reactions
and as far as we know,
complex chemistry needs water.
Liquid water is the absolute key, fundamental,
one and only must have it requirement for life.
No liquid water, no life.
It's just as simple as that.
Mars seems an unlikely place
to look for life.
It's far too cold for water.
Temperatures can be
minus 100 degrees
and there's virtually
no atmosphere
so every trace of moisture
is sucked out into space.
Unprotected a human being
would last just a few seconds,
but it seems that Mars
was once far more hospitable.
In 1969 NASA launched the first ever probe
to go into orbit around Mars.
When Mariner 9 arrived it found the planet
completely shrouded in a massive dust storm.
For a month they waited
for the dust to clear.
As soon as the images
started coming back from Mariner 9
people began to get
a really different picture of Mars.
Everyone had expected to see
a dead ball of rock like the Moon,
but slowly they started seeing signs
that Mars had once been very active.
The first thing that emerged
was this crater
that must have been 20 km above the surface
because it was in the middle of the atmosphere,
so it was like wow,
there's something really big there
that is sticking
up into the atmosphere
and above the atmosphere
and in fact is volcanic
so all of a sudden
it wasn't like the Moon at all.
And then they saw something
even more amazing
- what looked like
dried up river valleys.
That was a complete surprise.
I mean this was supposed
to be a dry, frozen planet
and here we have evidence of things
that look like old river beds.
And it completely changed
people's view of Mars in that sense
back to something that might
have been more Earth-like in the past
and much more dynamic than the Moon.
If these were dried up river beds
it meant that Mars must once have had
the perfect conditions for life.
Rivers form from streams,
streams are fed by rain,
rain falls from clouds
and clouds mean an atmosphere.
Mars must once have been
like the Earth is today,
if these were rivers.
The pictures from Mariner
just weren't clear enough to be sure.
Five years later the Viking orbiters
arrived with better cameras.
Some of these valleys had faint tributaries
just like rivers on Earth.
And these really look
like terrestrial river valleys
when you look at them
and you can see one here.
You can see there's
a, a valley through here
and you can see it branches,
there are tributaries.
Here's one branch going off
here with tributaries,
so this looks very much
like a terrestrial river system.
But many scientists just wouldn't accept
that rivers had once flowed on Mars.
The Viking images still weren't
good enough to settle the argument.
Then in 1998
Mars Global Surveyor arrived
equipped with the latest
high resolution electronic cameras.
Sections of the valleys
were revealed in fantastic detail,
but these amazing pictures
were still no use.
These valleys had all been
eroded and filled in with sand.
It was impossible to say
how they'd been formed.
Then, after they'd searched
through thousands of images,
they struck gold,
a winding valley
two kilometres wide
and at a bend in the canyon
a tiny channel,
the unmistakable trace
of an ancient river.
This is the best evidence
that we have
that climate in the past was different
from what it is today,
that there were warmer conditions
on Mars.
So Mars must once have been
warm and wet like the Earth.
It had rain and flowing rivers.
Then at some point the atmosphere
must have thinned and the planet cooled.
The flowing rivers
iced over and froze.
But when did the rivers
stop flowing?
Was there time enough
for life to emerge
before the last traces
of liquid water vanished from Mars?
The river valleys
are pockmarked with craters,
so they must have formed
billions of years ago
during the beginning
of the planet's history
when Mars was still
being bombarded with meteors,
but there are other features
carved into the surface more recently
which tell a very different story
about water on Mars
- giant channels stretching
for thousands of kilometres.
Well you see on this image
a fairly typical example
and you can see the channel
on this picture here.
Here's one side
of the channel,
here's the outline, you can see the sort
of eastern shore of the channel here
and there's the other side
of the channel.
These channels are enormous.
This crater here is 60 km across,
so you can see that the, the channel
down here is, is 200 km across,
so what happened, there was a lot of
speculation as to how these channels formed.
We, we looked into
the possibility of lava,
could lava cut a channel like this?
Liquid hydrocarbons,
liquid carbon dioxide,
and of course water.
Water seemed
the most likely explanation,
but how could anyone be sure
what had carved these monster channels.
For years scientists have been
searching for clues on Earth.
American geologist Jim Rice
thinks he's found them, in Iceland.
Buried under vast glaciers are some
of the most active volcanoes in the world.
It's a powerful combination
which had shaped the entire landscape.
When a volcano erupts
lakes of steaming melt water
form high up on top of the glacier
until the enormous weight
of water forces its way down
bursting out from the base
of the glacier.
These are the biggest floods
on earth,
a surging wall of water
stretching for kilometres.
In their wake they leave
vast plains littered with boulders.
To a geologist
these boulder fields contain unmistakable evidence
of the flood waters that ripped through here.
OK, well this is really
a classic textbook example.
These two large boulders here.
The size of them indicates
this was an enormous flood,
the deposit of these features,
but also if you look
at their geometry
these boulders are kind
of dipping back in this direction.
This has given us information about the path
the flood waters took that deposited these boulders.
The flood waters were going in this direction
where these rocks were deposited.
Now there's other interesting things
in the scene here.
For instance you notice some
of these smaller rocks are very well rounded
and these little nicked corners
of these boulders here.
These are called
percussion marks
and these are produced in the water,
highly turbulent water column
when the boulders
and rocks basically slam into one another
knocking the corners off.
These things all group together
just tell you there's no doubt
this was a catastrophic flood deposit.
Four years ago the Americans
sent a probe to land on Mars.
It was aimed at the middle
of one of these vast channels.
For the first time we'd see
what these strange features looked like
from close up on the ground.
The answer was obvious.
The first view of the landing site
sent back by the cameras on Pathfinder
revealed a rock-strewn plain
just like the boulder fields
left by catastrophic floods on Earth.
Here were the slanting boulders
lined up by the flood waters
and the cameras on the rover provided
detailed views of the individual rocks
with their telltale chipped edges.
We saw perched rocks that were kind
of sitting on a very small little,
as if it had been deposited
by this flood and actually scoured
as water had run past it,
so a whole suite
of things like that.
Observational evidence
very, very strongly argues
that, that this site is exactly
what we thought it would be from orbit.
Pathfinder confirmed that the vast Martian channels
had been carved by enormous floods,
so what does this mean
for the chances of finding life?
Some of these floods seem
to be quite recent,
so did Mars remain warm and wet
for billions of years?
Well that depends on
what caused these giant floods.
They stop almost instantaneously
in rubble-filled holes
with a channel coming out
and going off to the north
and so that suggested
that whatever caused the large channels
it was, it erupted
from the ground.
Mike Carr's theory is that these floods
are actually a sign that Mars was very cold.
Deep underground
geothermal heating melted ice.
For millions of years
the water built up
trapped under pressure
by a thick layer of permafrost,
until something broke the crust.
A vast reservoir of melt water
is released and surges out of the ground.
As the water rushes out it would rush out
so violent that it pulled a rock,
the aquifer, with it
so you'd have both rock
and water coming out
and then after
the flood was over
why the ground would collapse to form
this rubble-filled hole that we see.
To Mike Carr these floods are evidence
that Mars has been deep frozen for billions of years.
I actually believe that cold climates
are required to make these large flows.
You can't get the large flows
without this thick permafrost zone
that keeps the water in the ground
and doesn't allow it to get out.
So Mars might have been frozen
for almost its entire history
with violent floods periodically
bursting out from beneath the permafrost,
so what does that mean
for the chances of finding life?
Well that depends on
one other fundamental question.
The question you have to ask is
after these enormous floods
what was the fate of that water?
The floods on Mars were thousands of times
bigger than anything on Earth today.
Where did all the water go?
The channels flow downhill
into a giant basin around the north pole.
Did the floods just
fizzle out and freeze
or were they big enough
to fill this entire basin?
Did they form
an ice covered ocean
which could have sheltered
life for millions of years?
NASA's Tim Parker is convinced
there was an ocean on Mars.
His evidence comes
from features carved by a giant lake
which once filled
an enormous area of southern Utah.
We're flying over the, the floor
of an ancient lake
called Lake Bonneville that covered
about half the state of Utah
when it was at its maximum level
about 10,000 years ago.
The best evidence
that there was a lake here
is the erosion that occurred
at the margin of the lake, the shorelines.
Waves beating on the mountains
and, and cutting cliffs
and depositing ridges,
beach ridges along the margin.
One of the most dramatic features
is the flat terrace in the side
of this volcano cut by the water.
It's a clear sign this was once
an island in the middle of a giant lake.
Tim believes he's seen
similar features on Mars,
flat terraces around rocky
outcrops in the northern basin
formed by the pounding
of the ocean waves
and around the edge
of the basin
Tim believes the old Viking images
show two faint shorelines
stretching for thousands
of kilometres.
He suggested these were cut
by a shrinking ocean
which might have existed
for a billion years,
but he had no way
to prove it.
Then last year Global Surveyor beamed back
the first detailed contour map of Mars.
What we're looking at here
is a view of the northern hemisphere.
We're looking straight down
on the pole and this is the pole.
What the colours represent
are elevations.
This red here is the area of Tharsis
where there are huge volcanoes
and this one, Olympus Mons, is
2 and a half times the height of Mount Everest.
It's a huge volcano.
Now the large outflow channels,
the largest ones are over here.
The water came through here
and down into the low areas
here which are coloured blue.
Now Jim Head could check
the height of Tim Parker's proposed shorelines.
A standing body of water
forms a flat surface,
so shorelines should be level
along their entire length.
The outer line, called contact 1,
turned out to be extremely uneven,
but contact 2 seemed
much more like a shoreline.
The younger contact, contact 2,
was a much closer approximation to a flat line.
It, it had bumps
and wiggles as well,
but in many places
it was really straight
and corresponded to the place
where Parker had mapped the contact.
But not everyone is persuaded.
Last year the first close-up pictures
of the edge of the basin came back from Mars
and there's nothing
that looks like a shoreline.
I do not find the evidence
of these oceans convincing.
I would expect to be able
to see something
because the original shorelines
were depicted on the basis of imaging
and yet when we go back
and get better imaging
of the, of the places
where the shorelines have been mapped
we're not seeing
the shoreline there.
But even on Earth evidence of shorelines
can disappear when you get too close.
The terrace cut into the volcano
by Lake Bonneville
just becomes a stretch
of flat ground
which means nothing
this close in.
The argument goes on,
but perhaps life didn't need
a whole ocean to get started.
Just a few weeks ago
NASA released one of the most
important pictures ever taken of Mars.
Layered rocks in a basin
hundred of kilometres across,
probably formed by the slow
build up of sediments in a lake.
Did this lake last long
enough for life to evolve?
Might these sediments
contain fossilised Martians?
I think life would get started probably
in a few hundred or perhaps 1,000 years
so I don't think that we need huge amounts
of time to, to worry about the origin of life.
We don't, life kicks in
I think pretty rapidly.
On Earth it was
about one billion years
after the planet formed
from a mass of molten rock
that the first microscopic
fossils appear,
but no one actually knows
how long it took the first living things
to develop from the primordial soup.
One needs millions to billions
of years for evolution,
but for the actual onset of life
I don't think you need much time.
I can look at Mars
and think that this is a typical
rocky, wet, sunny planet
and life would have inevitably
started on such a planet.
Many scientists now believe that if life
did emerge billions of years ago before Mars froze,
craters once filled with water
are the best place to look
and there's one which stands out.
30 years ago NASA published pictures
of a strange formation of white rock
in the bottom
of a crater 90 km across.
I just clocked the fact
that it had been published
and I thought it was
a very interesting paper
but I wasn't particularly
interested in Mars at the time.
It just rather made us
think in a particular way.
During a trip
to central Turkey
Mike Russell stumbled
across a lake
which made him think again
about the white rocks on Mars.
Near the southern shore
Mike spotted strange white islands
and decided
to investigate further.
Well these particular structures
are probably only a few decades old
and the lake has dropped level
in the last 30 or 40 years or so.
It's really exciting
to come back here.
I, I first came out here, I swam out here in 1992
and I couldn't believe my eyes because
we'd been led to believe these were sand-dunes.
Mike Russell discovered these islands
were actually something far more extraordinary.
These rocks had been built
by microscopic organisms.
Photosynthetic bacteria,
the most primitive
life form on earth,
exactly the kind of creature
you'd expect to find on Mars.
From then on we started to think well,
could there have been life on Mars in these craters
and could it be that some of these white
rocks could have been formed by bacteria.
This lake showed that bacteria
can build huge rock formations
and as it happened these white rocks
were made of magnesium carbonate,
exactly what you'd expect on Mars
which has magnesium-rich soil.
So could this mysterious
white formation
be a sign that life evolved
in this crater long ago?
There will be vestiges of water
in craters, in lakes and so forth
on Mars for perhaps 500 million years
and that is absolutely plenty of time
to evolve photosynthetic bacteria,
so I would expect us to find eventually
evidence for photosynthetic bacteria on Mars.
And wherever they first appeared
they could have quickly
colonised the entire planet.
Of course that bacteria
can get anywhere.
It can last a long time,
they can get blown by winds
from here and there,
so any standing body of water on Mars
would have captured some of this,
some of these early bacteria
and they would have then
colonised any seepages
in any of these crater
lakes on Mars.
Last year the camera orbiting Mars sent back
the first close-up pictures of the white rocks.
Could these have been islands in a lake
teeming with bacteria
or are they just sand-dunes sculpted
and compacted by the Martian winds?
The only way we'll know for sure
is when we land a probe right on them.
As scientists have pieced
together the tantalising clues
it seems more and more likely
that early in its history
there could well have been life on Mars,
but what chance is there that
anything could still be alive there today?
If it ever started then the chance
of it surviving up to today
is pretty good because life somehow finds
niches and adapts to whatever's there.
Until a few years ago
it didn't seem likely that anything could
survive being deep frozen for billions of years,
but research in one of the coldest places
on earth has helped changed that.
In northern Siberia the brief summer sun
breaks up the pack ice and thaws the rivers,
but just below the surface
the ground stays permanently frozen.
Every year a team of Russian scientists
comes here to drill into the permafrost
in search of micro organisms.
People found the micro-organisms
in permafrost in the end of 19th century.
It was done specially in Russia
when people found mammoths.
Back then it was
the mammoth they were after,
but David Gilichinsky's team
have found bacteria and algae
which have been frozen underground
for an astonishing length of time.
The deeper they go
the older the permafrost.
The frozen cores are taken
to their laboratory near Moscow.
A sample is taken
from the centre of the core.
Then they see
if anything's still alive.
They've discovered that bacteria
can survive in the permafrost
for far longer than anyone
had thought possible.
When they started it was surprise for us
when they find even 10,000 years old bacteria,
but step by step you can come in Arctic
two or three million years old.
These micro-organisms have been living off
the minute amounts of liquid water
which exist even in permafrost,
so could they survive indefinitely?
In Antarctica the ground
is even colder than Siberia
and it's been frozen
for much longer.
This is the closest place
on earth to conditions on Mars.
The Russians have now teamed up
with NASA scientists to drill here.
A few months ago
they found bacteria
which may turn out to have been
at -20 degrees for more than 10 million years.
We have some data,
but we are not sure 100%
but probably we have now these alleged
bacteria from Antarctic permafrost.
It's between 8
and 15 million years old.
Bacteria had been buried
here in frozen ground
since before the beginning
of human evolution.
If life can survive
in Antarctica for 15 million years
then something could be waiting
to be revived on Mars
and last summer Mars Global Surveyor
sent back another extraordinary set of pictures
which suggests that in places
the Martian permafrost has been melting.
The camera has detected hundreds
of examples of cliff sides on Mars
with little gullies
running down the cliffs.
Now these look exactly
like gullies
that would form on the Earth
when, when an underground aquifer
comes out the side of a cliff,
a little bit of water comes out,
runs down the gully,
makes a seep, it just
keeps eroding down there.
These cases on Mars you have
a gully running down,
then you, in many cases you even have
a little mud-like deposit at the bottom.
These gullies must
be very recent.
There's no sign
of any erosion by the wind,
so if they were carved by water
our whole view of Mars
would have to change.
It means there could be liquid water
just below the surface right now.
The temperature here typically is
-60, -70, -80 degrees centigrade.
It's extremely cold,
so it's hard to imagine how one
could have seepages of water
under these very cold,
very cold conditions.
Any water seeping from below would freeze
long before it reached the surface,
but perhaps the water
could build up underground,
trapped by a thick
plug of ice
until the pressure gets so great
that the water forces a way out,
gushing so fast that even
in the icy Martian conditions
it could carve a gully
before freezing again.
Bill Hartmann believes he's found signs
of what could be melting the water underground.
His team have discovered that volcanoes on Mars
have erupted more recently than anyone had expected.
The most recent lava flows may be
less than a million years old.
For every time that you heat up
the crust of Mars enough to melt rock,
that's 1200 degrees centigrade,
I mean there could be
a thousand times
when you heat it up to zero
degrees centigrade and melt ice.
It's not out of the question
in my mind
that some of these seeps
have been active 1,000 years ago,
10,000 years ago, 100,000 years ago,
numbers like that,
or maybe more recently, you know,
maybe it was six months ago.
If there is still water
erupting on Mars
the implications for the history
of life are fantastic.
I'll spin the, the most
glorious optimistic scenario
which would be that
the geothermal heating from below
has for 4 billion years,
the entire history of Mars,
has, has kept open some liquid
water channels some place on Mars
so there's always been some place
you could swim from this place to that place.
If there has been water
on Mars for 4 billion years
what strange creatures
might be waiting for us?
If this discovery is confirmed,
it will surely be one of the most stunning insights
into our universe that science has ever uncovered.
The events of that week
in August 1996
are burned indelibly
on my brain
and I will never forget
them until my dying day.
Four years ago
a team of American scientists claimed
they had found evidence of microscopic life
in a meteorite that had come from Mars.
Allan Hills 84001 has become the most
intensively studied rock in the world
because proving that this rock contained life
from Mars has turned out to be very difficult.
What I would like
to do this afternoon is
lead you through our story
which is a bit of a detective story.
In 1994 geologists heard about
a new meteorite which had come from Mars.
We requested three
or four small fragments,
small chips about the size
of my fingernail.
Monica Grady's team in London
found unusually large amounts
of carbonate in the Allan Hills meteorite
which formed orange globules
in the rock.
Carbonates can sometimes
be produced by living things,
but the finding didn't
mean much on its own.
Then David McKay's team
at NASA took a closer look.
We were looking,
scanning around
in our electron microscope
looking at Allan Hills
and we particularly looking
at the carbonates.
There were a lot of rumours
and, and mutterings in corners
about the possibility
of something unusual
having been found
in this meteorite,
but nobody would say
for definite.
And I started to see some features
in Allan Hills which were very strange,
somewhat elongated features
that had segments in them.
The next day we found a few more
of 'em and we really got excited.
They thought they'd found
a tiny fossilised Martian.
This is perhaps the most
controversial part of our presentation,
but we'll show you
those anyway.
Anybody else who'd seen
Allan Hills 84001, who'd analysed it,
who'd even had a grandma
who's seen 84001 was being interviewed
to, to get their, their take
on, on what had happened.
The scientists will lay
out for you
how an ancient rock found
its way from Mars and it got to Earth.
The first time I saw
the worm-like structure
was at the press conference
that the NASA scientists had.
Martian micro fossils.
And I must admit I was
pretty amazed at the structure.
It is 41 billion years old.
It looks like a segmented worm,
it looks like you might think
a fossilised bacterium would look like,
but then you realise well,
crumbs, it's very small.
It means we're right
on the edge
of a potential unbelievable discovery
that's going to rock our world,
rock our world,
if it's true.
When McKay's team analysed
the rock surrounding their worm
they found three different substances
often produced by bacteria on earth.
These substances could all
be explained without life,
but McKay had a theory which would
explain why they were all there together.
Ours was the only one
that could explain everything
simultaneously with the same
simple explanation,
that is life on Mars.
They are the remains
of Martian life.
Is the fact that six things are
consistent with the presence of life
enough to convince you
that you're making one of the,
the most sensational claims ever made
and I would say no,
that, that what you need is evidence
that requires life to explain it.
This may look
like a Martian worm,
but Ken Nealson has shown how deceptive
appearances can be at this minute scale.
The pictures
of the Allan Hills meteorite
were taken using
an electron microscope
and to get the best images
the rock sample was coated
with an extremely thin layer of gold.
Nealson's team have been looking at rock
with a new kind of electron microscope.
This one can work
without the gold coating.
To my way of thinking
it's very impressive
how different the samples are
when they're coated
with gold or not coated.
His uncoated rocks looked jagged
and crystalline at high magnification,
but add the gold coating
and tiny blobs appear
which are about the same size
as the famous Martian worm.
The edges now can be
rounded off with the gold
and even an expert could
be fooled.
You'll look at it and you'll say
wow, you know that could be life.
So this might just
be rock fragments
made to look like a worm
by a thin coating of gold.
To prove it was once alive
you have to find out
what it's made of.
In California Ken Nealson's team have been
developing the kind of techniques
which may one day be needed to probe
Martian rocks for microscopic life.
Their system works by firing
a fine beam of electrons at the sample
and it's astonishingly precise.
They can find out what even the tiniest
microscopic structures are made of,
how much of each chemical
element the sample contains.
The first tests on the famous
Allan Hills worm
suggest it has exactly the same
composition as the surrounding rock.
If that's the case
this was never living.
The search for life on Mars began
25 years ago with the Viking missions.
Two landers touched down
and scooped up a sample of the Martian
soil for chemical analysis.
The billion dollar robots
worked perfectly,
but they failed
to find proof of life.
The Americans now realise
that solving one of the greatest
scientific mysteries
could never be
that straightforward.
We sent two spacecraft
which had extremely sophisticated
life detection experiments
and they came back negative.
You don't need to go and land
and poke your arm
in and pull out soil
and say is there a life
eating chicken soup there?
It's not, you know, that,
we already did that
and in a sense
we didn't learn as much.
We, maybe, maybe,
and this is arguable certainly,
maybe we asked too specific
a question too soon.
In 2003 the next missions
will be heading for Mars.
The Europeans have chosen to send the Beagle
probe to scratch the surface looking for life,
but NASA will be taking
a giant leap backwards.
The new rovers they're testing
at the Mars yard
will not be looking
for life.
They're just designed to gather basic information
about the geological history of the planet.
The rovers that we're sending
have no life detection experiments.
That's not the point.
We've landed three
places on Mars
and those three places are all
in the northern lowlands,
they're all kind
of the same.
Well let's go see what the southern
highlands are, what are they?
Let's go land in places
that have these unique signatures,
let's go see
what Mars is really about.
Rockets on the back shelf:
fire!
NASA is planning an armada
of increasingly complex missions.
Three, two, one, release!
Oh, sweet.
When they've scoured
every inch of Mars
and they've identified
the one place on the planet
which is most likely
to answer the question
then they'll be ready
to look for life.
Get that kind of information,
get that broad understanding first
before you go in
to ask the specific question,
so I think that's, that's
a noble question to try to answer -
is there life on Mars today,
but it's one that you
dare not ask directly
for maybe 20 years,
maybe 30 years, maybe even more.
The search for life on Mars
may turn out to be one of the hardest
problems science has ever faced.
Perhaps it's a question no machine
will ever be able to answer.
Perhaps Mars will only
give up its secrets
when the first humans make the journey
across the Solar System.
Converted into subtitles by m06166