Though we dream of the possibility of life
in the distant universe...
We assume that we are the only life in our solar system.
But is life truly exclusive to our planet?
Thanks to the latest extraordinary advances
in astronomy, it appears that we are closer
than ever to answering that question.
A new crop of space probes and sophisticated telescopes
is scanning our solar neighborhood
looking for answers,
and so far, things are looking up.
One of the big triumphs of astronomy
in the last two decades
is to show the majority of stars have planets.
There are planets all over the place.
There are more planets than stars.
It's a game changer.
It changes what we think about the possibility
for life somewhere else.
We may find some form of life
in the strange methane lakes of titan,
in the ocean hidden under the mysterious
icy surface of Europa,
in the gigantic geysers of Enceladus,
or in the desert plains of Mars.
The second Genesis within the same solar system
implies the origin of life is a likely event.
Is it only a matter of time
before we discover life in outer space?
Captions by vitac... www.vitac.com
captions paid for by discovery communications
Life...
An unbelievably perfect combination of elements
able to create living matter...
Possibly the biggest mystery of nature.
A combination of matter that shows certain attributes
that include responsiveness, growth, metabolism,
energy transformation and reproduction.
We don't yet know exactly what life is.
We don't have a working definition.
Probably my favorite definition is that life
is some sort of chemical entity that is self-enclosed
and is capable of Darwinian evolution by natural selection.
Some studies state
that life may have begun on earth
as early as 4.1 billion years ago.
That is still only slightly younger than earth.
A question arises immediately...
"is life an exclusive phenomenon of our earth?"
There is no easy answer to this question.
The chemistry of life began shortly after the big bang,
13.8 billion years ago, during a habitable period
when the universe was only 10 to 17 million years old.
Life may have emerged independently
at many places throughout the universe...
Or life may have formed less frequently,
then spread by meteoroids or comets
between habitable planets in a process called panspermia.
In any case, complex organic molecules may have formed
in the protoplanetary disk of dust grains
surrounding the sun before the formation of earth.
According to these hypotheses,
the processes leading to life may occur outside earth
on several planets and moons of the solar system.
Since ancient times, humankind asked itself
if we are alone in the universe
and if there is life beyond earth.
Those questions may not be easily answered.
However, they have always fascinated us.
Astronomers have been interested
in the question of life beyond earth
for a very long time.
I mean, we can trace back through the ancient Greeks'
and Romans' and Chinese writings
speculation about life beyond earth.
The first goal in our search for life
is to establish the conditions that will support it.
A source of energy, such as from a nearby star,
is needed to drive endothermic or energy-absorbing reactions.
Raw materials, predominantly carbon,
build and form organic molecules.
So the building blocks of life on earth then,
we know them... they are carbon, hydrogen, oxygen,
nitrogen... and others.
Um, they are what we are looking on other planets
to look for life as we know it.
These building blocks for life, at least as we understand it,
are ubiquitous.
Also indispensable is the presence of a liquid
or very dense gas
that enables biochemical reactions
to occur quickly and stably.
Liquid water,
the life-sustaining universal solvent,
at least on earth,
requires certain atmospheric composition and temperatures.
Now, in order to have a habitable environment,
you need three things.
You need liquid water, and you need organic material,
and you need energy.
And there are a number of places in the solar system
where all three of those things are thought to exist.
If we know the key conditions
for supporting life,
the question is then,
how many planets or moons in our solar system
meet these conditions?
Considering that one of the key prerequisites
for extraterrestrial life
is the existence of liquid water,
there are three candidates in our solar system
that have liquid water on their surface...
The planet Mars...
Jupiter's moon, Europa...
And Saturn’s moon, Enceladus.
Of all 160 or so planets and moons in the solar system,
Mars has so far received the most interest
from astrobiologists.
There are many signs that show that very early in its history,
Mars was much like earth,
with large areas of liquid water,
a thick atmosphere,
ample sources of energy for life,
and a good inventory of organic molecules.
In fact, what I like to say, when I compare the two planets,
is that you don't have to invent words to describe Mars.
You have mountains. You have canyons.
You have polar caps. You have dunes.
There is evidence that Mars
had a warmer and wetter past.
Dried-up riverbeds...
Vast canyons blasted out by epic floods...
Valleys carved by raging rivers...
polar ice caps...
Volcanos...
And minerals that form in the presence of water
have all been found.
There is a lot of evidence for liquid water
earlier in the planet's history,
much earlier, about 4 billion years ago,
and perhaps some transient water in the time
since 4 billion years ago.
But the evidence indicates
that all water disappeared
from the surface billions of years ago.
As Mars cooled down and lost its atmosphere...
did life ever get a foothold on the planet?
Overrlty science - discovery.
We had a piece of Mars here in the lab.
We still have it.
Allan hills 84001,
a rock that was chipped off Mars
by an impact millions of years ago,
wound around in space,
landed on the earth in the antarctic ice sheets.
And during the 1984 spring collection season,
as that ice was melting and those black rocks
were picked up in the melt pools, we realized,
by the gases that are included in that piece of rock,
that that's a piece of Mars.
And we took it apart at microscopic scales,
and wey Sc big scientific controversy
because there were scientists
over there claiming features in that rock
could only have been produced by biology,
and other scientists saying,
"nope. You can get that with geology."
The search for life on the red planet
started decades ago.
In 1976, a search for microbial life on the red planet
was performed for the first time ever.
Two decades later, in 1997,
the pathfinder mission took a new step forward
in this search-for-life adventure.
In 2008, the Phoenix spacecraft explored Mars' north pole.
After digging a few inches, it found a white material
that evaporated several days later.
The analysis of that material revealed it was water ice.
Satellites scanned both polar caps
and found that there was a lot of water ice
under a layer of frozen carbon dioxide.
If all that ice ever melted, an 80-foot-deep ocean
would cover the whole planet.
The same satellites also discovered
that there was ice buried
everywhere beneath the desert plains.
This was a shocking discovery.
Mars had huge amounts
of water ice everywhere.
But could life exist in the buried ice itself?
We now know that there are extremophile microorganisms
able to live in similar environments in the dry valleys
in the antarctic here on earth.
Currently, Mars is very dry and very cold.
It's like some regions in Antarctica today,
and it's kind of like a very cold desert,
so liquid water would not be stable.
If you opened up a container of water,
it would immediately evaporate because it's so dry.
Buried ice was found under a layer of dry dirt,
as also happens on Mars.
At the point where the dirt met the ice,
there was a thin film of liquid water
where extremophiles thrived just for a short time.
These microorganisms remain frozen
and dormant most of the year,
they only flourish for a few scoverrm wnce during the summer.
Today, micros could still live at depth,
at some depth favored by the presence of thin films of water
or maybe more liquid water because the deeper you go,
the more the chance that water could be liquid.
During the martian summer,
it's common to reach 70 degrees Fahrenheit at the equator,
so the buried ice might melt and create similar conditions
to those found in the antarctic dry valleys.
Any microbes that might have been there,
they're probably living within the rocks
or under rock coatings.
So that's one of the analog sites
that my group's been investigating
is microbes that are living underneath the surface
because that might be viable for Mars as well.
A future mission could eventually prove
whether this hypothesis is true or not.
But there is another possibility
that liquid subsurface water exists on Mars.
Mars' huge volcanos, such as Olympus Mons,
could contribute internal heat to sustain subsurface water.
This would imply that hydrothermal vents
could exist on Mars as well,
and therefore, it might also be possible
that extremophiles similar to the ones that thrive
in the terrestrial hydrothermal vents exist on Mars.
On September 2015, NASA's Mars reconnaissance orbiter
made in incredible discovery.
This spacecraft provided the strongest evidence yet
that liquid water
flows intermittently on present-day Mars.
It's not pure, transparent water.
It's very briny water, very salty water,
which allows it to remain stable
for a little while at the surface
because the pressure at the surface of Mars
is very, very small.
Using an imaging spectrometer,
researchers detected signatures of hydrated minerals on slopes
where mysterious streaks were seen on the red planet.
They darken and appear to flow down steep slopes
during warm seasons and then fade in cooler seasons.
This finding proved what anyone could have imagined.
On Mars' present-day surface, there is liquid water.
Maybe in some of those ephemeral streams of liquid water,
microbial life has managed to arise.
We will have to wait for future rovers and explorers
to confirm this hypothesis.
In the meantime,
there is another body in our solar system
that could hold life, but it's not a planet.
Much further away than Mars,
there is another unique world that might harbor life...
Europa.
Europa is one of the four largest moons of Jupiter.
It's slightly smaller than our moon,
and its icy surface
is negative 250 degrees Fahrenheit.
Virtually everything we know about Europa is thanks
to NASA's unmanned space probe, Galileo,
which passed by Europa 12 times.
These were the first images it captured.
It is covered by a smooth layer of water ice.
In fact, it has the smoothest surface
of any known solid object in the solar system.
The surface of Europa is unique in the solar system.
It has very few craters,
which tells us that the surface is being reprocessed frequently.
Some parts of its surface
show blocks of ice that are separated
but seem to fit together like a puzzle.
These icebergs could've been shifted by slushy
or liquid water beneath.
These cracks probably may extend
all the way down to the ocean,
or at some point, so you could get some percolation of water.
This peculiar landscape
is very similar to sea ice on earth.
Galileo was able to detect that all of those things together
add up to our picture of how we now know
that Europa has a liquid ocean under its surface.
In 1996,
the Galileo spacecraft detected a magnetic field
on the planet's surface
indicating that there must be some electrical conduction
likely to derive from a salty ocean
that could be 60 miles deep.
The studies and observations, measurements
that have been made in the past decades
seems to be converging pretty clearly
with the presence of an ocean under the surface of the ice.
So there we have the first key ingredient for life,
liquid water.
How can water remain liquid at temperatures
of negative 300 degrees Fahrenheit?
Some sort of mysterious internal heat
must be melting the icy crust,
and Jupiter is the culprit.
Scientists propose that it's due to the tidal heating
from the friction
due to Europa’s eccentric orbit around Jupiter.
The ice at the surface of Europa, it has been cracked.
It's not completely sealed.
You can see, because of gravitational pull and pull,
there is this tug-of-war as Europa is moving around Jupiter.
You can imagine that all this friction
is creating lots of energy, lots of heat.
And then we have good reasons to think
that there are... Hydrothermal system,
which means that you have, you know,
water being heated by this process.
Volcanos deep down may harbor hydrothermal vents
that provide an energy source to heat and maintain liquid water.
So we have two of the three conditions for life...
The liquid, in this case, liquid water,
and a source of energy, that interior heat.
We would just need some organic compound,
and the chances of life arising would skyrocket.
The Galileo spacecraft observed that Europa’s ice
contains carbon dioxide.
When this carbon dioxide is strongly impacted
by Jupiter's radiation,
it can produce simple organic molecules,
such as formaldehyde, that are steps towards life.
The aforementioned tides of Europa could also mix
life-supporting substances together in the ocean,
but nothing has been proven yet.
In 2013, NASA reported a surprising discovery
on the icy crust of Europa...
Some Clay-like materials,
specifically phyllosilicates, were detected.
Phyllosilicate just means phyllo-like layered silicate,
and these are fancy names for clays.
And clays are a kind of mineral that forms in a lot of water.
And on earth, there are some theories that these clays
were some of the original minerals
that were present when life was evolving.
According to some hypotheses,
the presence of these organic-associated minerals
may have been the result of a collision
with an asteroid or comet.
With liquid water, an energy source,
and the necessary chemical building blocks,
perhaps delivered by comets or asteroids,
Europa opens up the possibility
that life could exist in places never imagined.
12,000 feet beneath the arctic ice sheets,
in complete darkness, there are hydrothermal vents
that spew out super-heated water with lots of toxic chemicals.
Scientists think vents like this
could also exist on Europa’s ocean floors.
We think that the potential source of energy for an ocean
in Europa will be the volcanic activity.
We have recently discovered
that clustered around the vents,
there are extremophile microorganisms
that cover miles of the arctic seafloor.
The discovery of life there really raises
the possibility of life on Europa.
Probably, Europa might be
the best candidate for us
to find extant life.
The challenge now is to prove
that life has been able to thrive
in such a bizarre environment.
NASA and the ESA have planned two different missions to Europa
that will investigate its habitability
in the next few years.
In 2015, NASA approved a new mission to go to Europa
and investigate its environment
and, particularly, to look for habitability.
NASA's Europa multiple flyby mission
is a spacecraft that will be launched in the 2020s.
The spacecraft will be a highly capable radiation-tolerant probe
that will perform repeated close flybys of the icy moon.
It will also be looking under the surface
to learn more about the structure of the ice shell
and the structure of the ocean underneath the shell
using radar and magnetic field detectors and other instruments.
The ESA is developing another mission,
the Jupiter icy moon explorer, the so-called juice mission,
that is planned for launch in 2022
and arrival at Jupiter in 2030.
This spacecraft will spend at least 3 years
making detailed observations, not just of Europa,
but also of the giant gaseous planet, Jupiter,
and two of its largest moons, Ganymede and Callisto.
We will have to wait until the next decade
to confirm whether or not there is life on Europa,
but could another moon in our solar system
have similar conditions for life?
Europa isn't the only intriguing place
this far out in the solar system.
Could similar conditions exist on other moons
orbiting other planets, even further away from the sun?
Orbiting Saturn, there is a small, mysterious moon
that is totally different from the rest
of its more than 60 moons.
This tiny, icy moon, only 300 miles across,
is Enceladus.
In the last few years, this tiny moon
has became the main goal for exobiology,
as it has revealed some extraordinary conditions
for harboring life.
Most of what we know about Enceladus
is thanks to a mission called Cassini.
It's a mission that has been going on for many years.
It's an orbiter that has been studying
the entire Saturn system and its different moons,
but it's been paying close attention to Enceladus.
The Cassini mission offered us
a close-up of this remote world for the first time ever.
These were the first images it took.
The surface is white and glittering,
and it is carved with fissures, crests and cracks.
At the south pole, Cassini made a surprising discovery.
It photographed some strange large cracks, seen here in blue,
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They are 75 miles long and hundreds of feet deep.
They are similar to fault lines on earth.
After several flybys, Cassini's thermal radar revealed
something unexpected.
The tiger stripes should be colder
than the rest of the moon,
as they were in the south pole.
However, they were radiating heat.
The fissures were at negative 120 degrees Fahrenheit,
which was more than 270 degrees warmer
than the rest of the moon.
It's definitely a place where we see evidence
that something profound
is happening in terms of potential
for a habitable environment.
But the most shocking finding was still to come.
When Cassini was reoriented, it captured a shocking image.
Vast jets of ice were erupting into space.
The camera was able to image plumes of water vapor
and ice crystals
coming off the south pole of Enceladus.
These actual images showed
the plumes were ejecting ice particles
hundreds of miles out from the tiger stripes.
Those materials are being ejected through fractures
on the surface of the moon
which seem to be connecting the surface with the interior.
However, how can this small moon generate so much heat
as to be able to maintain such geothermal activity?
Scientists believe that Enceladus might have
an internal energy source like Europa.
When it orbits the massive Saturn,
friction from gravitational processes causes it to heat up,
melting ice in the moon's interior
in the same way as on Europa.
These jets were giant geysers of water
that erupted from its icy surface,
much like those in geologic hot spots on earth.
Cassini actually has a detector
that can fly through the plume,
pick up some of the particles and analyze them chemically.
And when that detector did its work,
it found that some of the particles are salty.
And the only way to get salt incorporated into a particle
is to have it evaporating directly off of liquid.
So that was yet another hint
that Enceladus has liquid under the surface,
from which these plumes are emanating.
But could it prove
that under the icy crust of Enceladus
existed a subsurface ocean like on Europa?
We needed even more evidence.
The next piece of evidence was from Cassini
flying past Enceladus,
and just carefully analyzing its trajectory,
as it flew past Enceladus, to directly measure
how Enceladus' gravity was pulling on the spacecraft.
And when that analysis was done, it found a density anomaly
under the entire south pole
indicating that you have a regional sea of water
from which these plumes are emanating.
These jets might be connected
to active hydrothermal vents
at a subsurface water ocean floor
where the moon's ocean meets the underlying rock,
a prime potential habitat for life.
But there still wasn't anything that could prove life existed
underneath that icy crust.
That's why it was decided that Cassini should fly
through these jets and collect particles.
The probe's spectrometers detected something
really exciting.
They found, in the jets,
the basic chemical building blocks of life.
So Enceladus is fascinating because, as far as we can tell,
it contains the three basic ingredients for life...
Liquid water, nutrients and organics.
But does this strange and alien world
actually support life?
The geysers could provide easy access
for sampling the moon's subsurface ocean.
And if there is microbial life in it,
ice particles from the sea
could contain the evidence astrobiologists
need to identify them.
There are two exploration missions proposed by NASA
to Enceladus in the near future
that would try to find evidence of life in the tiny, icy moon.
The first one is the journey to Enceladus and titan mission.
This is an astrobiology mission concept that will assess
the habitability potential of Enceladus and titan,
moons of Saturn.
The second mission waiting for approval and financing
is the life investigation for Enceladus.
This proposed mission would capture icy particles
from Saturn’s moon, Enceladus,
and return them to earth
where they could be studied in detail
for signs of life, such as biomolecules.
It's relatively simple, technologically speaking,
to send an orbiter to Enceladus
that can capture those icy particles
in the plume and analyze them in situ
or bring them back to earth
for detailed analysis in the laboratory.
Unfortunately, neither of these missions
have been approved yet,
so we will still have to wait to unveil whether or not
there is life on this tiny enthralling moon of Saturn.
Though we haven't yet found life outside earth,
there is one more candidate for life in the solar system, titan.
Close to Enceladus,
there is the last of the great candidates
for life in the solar system, titan.
It is one of the largest moons in the solar system,
and it is also the only moon
that is known to have a thick atmosphere.
Data from the Cassini-Huygens mission,
which flew by titan in 2004,
demonstrated the existence of hydrocarbon lakes.
Titan is a fascinating world.
It's the most alien place in the solar system, so to speak,
because it, in fact, other than the earth,
is the only place we know of
that has seas of liquid on its surface,
but those seas are not made of water.
In these seas and lakes, there are no waves,
as the liquid is liquid methane and ethane,
which is much less dense than water.
These two hydrocarbons, on earth, are volatile gases.
But on titan's negative 300 Fahrenheit degree temperature,
they are liquid.
Titan has a very similar landscape to earth.
There are seas, lakes,
smoothed rocks on the riverbeds,
mountains, valleys, canyons.
But these mountains and pebbles are not made by any rock,
like on earth.
They are made of water ice so frozen,
due to the negative 300-degree temperature on titan's
chilly surface, that it behaves like rock.
Cassini's radar images showed that on titan,
liquid methane forms clouds, thunderstorms,
and even falls as rain.
Methane in the atmosphere
also plays a role similar to water in the atmosphere.
On earth, you have a water cycle.
On titan, methane plays a very similar role.
It falls to the surface as rain or mist.
We do see channels and rivers
where methane is flowing across the surface
and doing geological work
like we would see water do on the surface of earth.
Liquid methane has a cycle
very similar to earth's water cycle.
The question is, could it behave like water on earth,
as liquid that allows organic molecules
to dissolve and interact?
There is no easy answer to this.
Titan's atmosphere also contains many organic gases,
such as methane, ethane and hydrocarbons,
and possesses conditions that resemble
those of early earth 4 billion years ago
that allowed life to develop.
In many ways, the atmosphere of titan looks like a young earth
in the fridge, much colder, much cooler.
But prebiotic chemistry, the same processes are there.
What we don't know is whether these prebiotic, you know,
processes are turning into something
that is biological in nature at the surface of titan
or in the subsurface.
However, liquid methane and ethane
are much colder than liquid water by some 400 degrees,
and biochemical reactions would occur
at painstakingly slow rates.
These compounds are far less capable as solvents
compared to water
and therefore much less life-inducing.
Water is also missing from the picture
due to freezing temperatures of negative 300 degrees Fahrenheit.
Several experiments have shown that,
with an atmosphere similar to that of titan
and the addition of UV radiation, complex molecules
and polymer substances
like tholins can be generated,
substances that could be considered
a sort of precursor to life.
What weirdo chemistry, physics, you know, biology could be,
people are trying to think in terms
of what could be a biology based on methane.
It's not the best, apparently,
when it comes to provide a structure for biochemistry.
The conclusion
is that titan is a world rich in organic matter
with a methane cycle comparable in atmospherical
and geological processes to earth's water cycle
that is really likely to harbor life.
Titan may harbor life,
but how exactly will we get there to find out?
In the last years,
NASA and the ESA have combined efforts
to develop an unmanned space mission
that could finally unveil all of titan's mysteries,
but none of them have been approved yet.
One of the most exciting missions
proposed to unveil the secrets of the methane
and ethane lakes of titan
is NASA's titan submarine.
This submarine would explore the depths of the Kraken mare,
the largest-known body of liquid on the surface.
This mission would be designed
to measure the organic constituents on titan
and would have performed the first nautical exploration
of an extraterrestrial sea, analyze its nature
and possibly observe its shoreline.
As the other proposed mission to titan,
this titan submarine mission
hasn't been given the green light yet.
There's lots of really fun options for exploring titan,
but NASA has not actually selected one of these options.
Therefore, to date,
there are no confirmed space missions
to titan in the coming years,
but everything could change if a shocking discovery
is made in the near future.
Whether or not any of these potential space missions
finally reveal the existence of life on Mars,
Europa, Enceladus or titan is an unknown.
But what we do know is that now we are much closer
than ever to finally finding an answer
to the question of whether there is life beyond earth.
Fifty years ago, the era of robotic exploration
of our solar system was just beginning.
In July 1965, the mariner 4 probe
sent the first close-up images of Mars.
Those blurred images showed that Mars did not have vegetation,
much less canals crisscrossing the planet,
as envisioned by earlier generations of astronomers.
At that time, the most widespread opinion was that Mars
was not just the red planet but also the dead planet,
with the chances for life of any kind
being considered infinitesimal.
Things have radically changed since 1965
thanks to the extraordinary advances of technology
that have let us use more and more sophisticated space probes
to explore our neighbors in the solar system.
Three vital factors...
Energy,
liquids,
and chemical building blocks...
Are more widespread than has ever been realized.
Now it is not so unlikely to find life beyond earth
in our solar system.
We can't deny that such a huge discovery,
even if it were just microbial life,
would be really shocking for mankind,
as it would imply the first step toward believing
that we may not be totally alone in the universe.