Space's Deepest Secrets

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?

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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.