Original subtitles

ROWE: The universe...

Vast, dynamic, and explosive.

[explosion blasts]

But this huge cosmos, with its billions of galaxies

and countless stars,

isn't the only one... We share our lives with

another universe.

The world of the small,

of the viruses, of the bacteria.

ROWE: We call this strange hidden kingdom the microcosmos.

LANZA: The microcosmos is incredibly important.

Even though we can't see it, it's everywhere.

It's almost like another universe

or another world all in its own.

ROWE: It guided our evolution...

We wouldn't be here without the microcosmos.

...and it keeps us alive.

The microcosmos is responsible for

the very oxygen that we breathe.

ROWE: And it will influence our future as we venture out

into space.

OLUSEYI: And if we were ever to find a place where

there is life, potentially a new microcosmos,

we would have no immunity if they're bad.

ROWE: We share our world with the microcosmos.

Will we coexist in an uneasy peace,

or will it destroy us?

[explosion blasts]

A strange invisible assassin stalks its prey.

It attacks and hijacks the cell,

forcing it to produce hundreds of new raiders.

This is what happens when the microcosmos turns on us.

In 2020, we experienced this invasion

of the body snatchers first-hand.

A tiny virus caused a global pandemic... COVID-19.

This pandemic makes me see the world completely

differently, because there was an invisible universe,

one that covers me and is within me

that I pretty much ignored for the most part.

ROWE: Maybe we ignore this other universe

because it's invisible to the naked eye.

PLAIT: We live in a largely invisible universe.

We can't see everything that's going on.

Some of the biggest stuff we can't see very well,

and, in fact, a lot of the littlest stuff we can't either.

Just because something is too small to see

doesn't mean it's not important.

In fact, very, very tiny things

have a huge impact on our lives.

ROWE: Some of these impacts are beneficial,

but they're overshadowed by the devastating effects

of disease.

The longest-running conflict that humanity has been

engaged in is that against

the microcosmos, our long running battle against

the bacteria and viruses

that are trying to kill us.

ROWE: A century ago, we faced the Spanish flu.

HOWETT: This absolutely annihilated Europe at the time.

It caused millions upon millions of death.

So this is definitely not the first pandemic,

quite frankly, probably isn't the last one.

In a way, the coronavirus has forced us to come

to a greater understanding of the microscopic world.

ROWE: The microcosmos is complex.

While some parts kill us, others keep us alive.

Microcosmos is important for us to survive,

in order for us to do all of the things

that our body does, in order for us to live

and grow and thrive.

Our lives depend on the microcosmos.

The air we breathe and the surface of the Earth around

us has been profoundly affected by the microcosmos.

ROWE: Three invisible microcosmos operates

in every part of the world.

This world that you can't see is everywhere,

from geothermal hot springs to glaciers

to deep sea hydrothermal vent systems.

ROWE: We have discovered that every cubic foot of

Earth's atmosphere and its oceans contain millions

of viruses.

There are more viruses here on Earth

than there are stars in the universe.

That's incredible.

ROWE: Even though they're around 1/400th

the thickness of human hair, stuck end to end,

all the viruses on Earth would stretch

100 million light-years.

That's 40 times the distance to our neighboring

galaxy, Andromeda.

RADEBAUGH: That really makes us ask,

"Whose planet is this anyway?"

If you just added this up by sheer numbers,

you would say, "This is the virus planet."

ROWE: The microcosmos has also taken over

our bodies... We're only partly human.

The fact that so little of my own body, of everyone's body,

is human cells kind of leaves you wondering

what's the rest of it made of, right?

It is astonishing that we share our bodies with over

380 trillion viruses.

ROWE: And over 39 trillion bacterial cells.

OLUSEYI: The average human has more bacterial cells

inside their body than there are human cells inside their body.

So what are we really?

There are moments in the history of science that I actually

remember where I was when they happened... when,

for example, we detected two colliding black holes

or something like that.

But another one was when I realized that

almost half our body is actually not human.

- I mean, that is crazy. - For people that are

scared of bacteria, that's a really interesting

thing to know, right?

ROWE: Bacteria help us digest food,

produce vitamins, and even influence our mood.

But what are they?

Bacteria are single-celled organisms with a cell wall

and a central nucleus containing genetic material,

RNA or DNA.

They can move around and replicate.

Viruses are completely different.

In the universe,

there are some mysteries that have actually personally made

me kind of pause,

give me goosebumps, and strangely enough,

one of them is viruses.

ROWE: The mystery is how viruses can

have so much impact on the world,

despite their tiny size and apparent simplicity.

Most are just a strand of genetic material,

sometimes encased in a shell of protein.

I mean, compared to bacteria,

which behave kind of like other normal cells that we're

used to, to some degree, viruses are very strange.

We don't really understand viruses.

We... we don't even know if they're alive or not.

The question are viruses alive is actually

more difficult to answer than you might think.

What is the definition of life?

What does it mean to be alive?

ROWE: NASA's definition of life is a self-sustained

chemical system capable of Darwinian evolution.

Entities that feed make energy and reproduce.

Viruses can't do that on their own.

They have to have a host cell to do that.

They have the genetic material that they need,

but none of the machinery.

So they really have to infect a host.

If not, they're useless.

ROWE: Inside a host's body, viruses latch

onto the surface of cells

and then take control.

A virus's life cycle is effectively to hack

another cell.

They have to inject that genetic material

into a living cell.

And then the cell is hijacked and starts making copies of

the virus.

Which then have to burst out of this cell almost literally

like that gory, grotesque scene in "Aliens."

They burst out from the inside.

That's like a cellular level horror movie.

ROWE: This method of replicating is chilling

and doesn't answer the question of whether

they're alive.

That uncertainty may influence our search for life in space.

BYWATERS: One of the interesting things to think about is

if we found a virus on another planetary surface,

would we classify that as life?

Would we say that we have found life?

ROWE: We don't know, but space viruses could be

a sign of other extraterrestrial life forms.

BYWATERS: Viruses have to have a host cell to replicate,

so if you find a virus, in essence, you've found life.

ROWE: Viruses might lead us to extraterrestrial life.

Now, new research suggests that life

on Earth may have come from space,

brought to us in a cosmic bombardment

when our planet was young.

ROWE: We find the microcosmos in every feature of Earth.

But where did this strange kingdom of the very small

come from?

Some of its members are so weird, they look like aliens.

Could they have come from space?

There's this idea that microbes could have hitched

a ride on a chunk of an asteroid

that would fall to Earth.

HOWETT: They could form on a different planet.

Something hits that planet.

The rock that they're sitting on gets lifted

and then hits the Earth as a meteorite.

ROWE: The idea of hitchhiking bugs sounds a bit wild,

but we have found chunks of Mars on Earth.

Perhaps these space rocks brought life.

PLAIT: It's not completely ridiculous.

We know that rocks, for example,

could come from Mars and land on Earth.

A giant asteroid impact on Mars could blow

shrapnel into space that could land on Earth.

ROWE: To learn how we must return to the early

solar system, 4.5 billion years ago.

Many infant planets orbit a new star,

our sun... this infant solar system is chaotic.

Collisions between planets are inevitable.

OLUSEYI: The early solar system was like a pinball machine.

Stuff was hitting,

knocking stuff off, that would land somewhere

and knock stuff off.

ROWE: The young Mars is in the line of fire.

It already has primitive oceans and perhaps

primitive life.

A huge space rock smashes into the surface.

We call the event the Borealis Impact.

It blows quadrillion tons of rock into space.

It's not crazy to think that one of these chunks of

rock traveling through our solar system has some

hitchhikers on board.

If there's some microbe riding on an asteroid that got blasted

off of Mars, kind of feel sorry for it, right?

It's just living there on Mars,

doing whatever little Martian microbes do.

And then a giant impact ejects this thing into space.

DARTNELL: In order to get from one planet to another,

a cell would have to run a gauntlet.

It's almost like winning a survival game show.

You've got to survive being blasted off your home world.

You've then got to survive the interplanetary journey

inside a small lump of rock,

being exposed to the vacuum of outer space, to cosmic rays,

to UV radiation, being dried out and frozen.

So the idea of moving life around

the solar system or through... Around the galaxy on asteroids

poses a lot of different challenges.

ROWE: Events like the Borealis Impact ejected so much rock

from Mars, there were lots of opportunities for hitchhiking

bugs to run the gauntlet of space.

But could they survive the journey?

To find out, astronauts on the International

Space Station grew simple bacteria outside in space.

After a year of being in open space, miraculously,

some of these microbes survived.

It's incredible. These microbes just could not

be killed, even though they were in the worst possible

environment for life.

DARTNELL: The mission, therefore, shows us that

life can survive the environment in outer space.

Life could be transferred between planets.

Maybe life did get started on Mars,

on our next door neighbor planet,

and then was transferred here

inside a meteorite.

Maybe we are immigrants from Mars.

ROWE: Hitchhiking bugs may have arrived on

Earth and kick-started the microcosmos.

But now, recent studies of meteorites suggest that

even if living microbes didn't make the journey,

the building blocks that made them did.

[explosion blasts]

In November 2019, an international research team

found an organic molecule

called ribose in meteorites that had crashed on Earth.

Ribose is a sugar.

It's a simple sugar,

but it is a sugar that is

absolutely crucial to all life on Earth.

Ribose is the sugar that makes up RNA, and RNA

sits right in the linchpin of every cell.

ROWE: RNA is a simple form of

genetic material that controls cellular function.

It's found in most primitive creatures.

Finding ribose on a meteorite is so important for us to

understand the origins of

the microcosmos, because these are

the building blocks, these are the things that it needs to

get started,

so understanding where these building blocks come from

allows us to understand how the microcosmos might have

evolved and started.

ROWE: The Rosetta Mission found another building block

for life out in space...

A form of phosphorus on the comet,

67P.

SHIELDS: This was astounding.

Comet 67P was formed at the birth of the solar system,

4.67 billion years ago,

and it hasn't changed since then.

It's a time capsule from the birth

of the sun and the planets.

DARTNELL: And it's been in the deep freeze ever since.

So these forms of phosphorus that we found on comet 67P

tell us what was available at

the time the Earth was forming and then

when life was getting started on primordial Earth.

ROWE: The early solar system

contained many chemicals needed for life.

BYWATERS: It's an important discovery,

because it means that these compounds

were around when the solar system was forming,

so they would have been readily available for life to

tap into and use to start forming cellular structure.

ROWE: These discoveries not only show that essential chemicals

came to Earth,

but that they exist throughout the solar system.

LANZA: We tend to think of the microcosmos as only

existing on Earth in the sense that only Earth

has these building blocks,

but now, these new observations suggest that a microcosmos,

at least the building blocks for one, could exist

beyond Earth and throughout the solar system.

ROWE: Comets and asteroids may have brought

chemicals to kick-start the microcosmos.

Now, explosive new research suggests that

space rocks hitting Earth did even more.

Could the violent impacts themselves

have helped life get started?

[explosion blasts]

ROWE: How did the microcosmos and life on Earth start?

Did asteroids and comets deliver the building

blocks, phosphorus,

ribose, and other organic compounds?

Or did they start life in other ways?

New research suggests the impact of crashing

space rocks could have provided the spark for life.

The force of the impact actually triggered the creation

of these molecules that are the building blocks of life.

ROWE: The energy from the impact breaks down

and reforms molecules into new compounds.

You can actually strip apart atoms and molecules,

re-combine them in more complex ways, and make the stuff

of life in an impact.

ROWE: Over millions of years,

complex organic materials fill Earth's oceans.

Then, around 3.5 billion years ago,

the process that kick-started life began.

THALLER: Going back to the origins of life on Earth,

it was a process... you began with large molecules

that almost accidentally began to make copies of themselves.

These became the first genetic material... some of these larger

molecules bound together and became the first sort of

protocells.

A protocell could represent

this earliest pre-life stage of evolution.

ROWE: Protocells lack the full chemical machinery of

modern cells.

They're a simple cell membrane surrounding a glob of

genetic material like RNA, built from ribose

and phosphorus.

Now you have a barrier.

Now you can actually control which chemicals come into

the cell and which go out, and you protect the genetic

code intact, inside the cell.

Once that happened, evolution began to run with it.

ROWE: These simple cells grew more and more complicated

until shazam,

you get all life on Earth...

All cellular life, anyway.

Unlike bacteria, viruses are not cells.

Scientists debate if they're even living things.

So how, then, do viruses fit into the birth of life?

Viruses aren't really thought of as playing a role

in our evolutionary history,

but we're just beginning to understand that

that's simply not the case.

What if viruses themselves were

an essential cog in the machinery of life?

ROWE: How can we investigate if

viruses helped life on Earth develop?

They don't leave many clues about their past.

BYWATERS: The hard thing with understanding

the evolutionary history

of viruses is they don't leave a fossil record.

There's no geology that we can go back and dig up and say,

Aha! This is when viruses first came about.

ROWE: We don't know when viruses entered

the evolutionary game of life.

Was it near the beginning, or a little bit later?

There's this crazy idea that viruses might actually

have come first in the tree of life.

THALLER: When you think about the real origins of life,

it had to start with something that simple,

something that was just a molecule that could

start replicating.

A virus may be our best example of that

transition from just complex chemistry

to the beginnings of life.

In this scenario, chemicals floating

in the 3.5-billion-year-old

oceans formed a shell of protein around some simple

genetic material.

But did viruses evolve before anything else?

BYWATERS: The flaw in the virus first hypothesis is that

a virus has to have a host organism to replicate.

So without a host, how does the virus replicate?

And this is the question we have to ask ourselves

when we think of viruses coming first on

the evolutionary tree.

ROWE: Modern viruses can't replicate without a host.

It's likely that ancient viruses couldn't either,

but could early cells and viruses have joined

forces in a way that benefited them both?

Some new theories are suggesting that viruses

and cellular life co-evolved and actually helped each other out,

and potentially even helped out the evolution of

human life.

ROWE: How did this co-evolution work?

We know that viruses today inject their genetic material

into cells to manipulate them.

Perhaps early viruses manipulated the genes

of the first cells the same way.

Think of this primordial soup and the genes, the RNA, that's

in this primordial soup being swapped between organisms,

kind of like a swap meet.

You bring something you don't need any more,

and you pass it along to somebody else.

So in this way, organisms sharing their genetic material

back and forth offers a competitive advantage

to each one.

ROWE: The virus might break off bits of

the host's genetic material and mix it with their own.

When the virus attacks another cell,

it could pass on the mixed genes to its next host.

In this sense, then,

viruses help stir things up.

They shuttle genes between wildly different

organisms and therefore help drive evolution itself.

Now, probably almost all of these injections did

nothing useful or maybe even killed the cell.

But if one in a million injection changed

something for the better,

made it more complex, made it more able to survive,

then that cell reproduced even more.

ROWE: If virally enhanced cells thrived in the primeval oceans,

over time,

they might have evolved into more complex creatures

and eventually, into us.

RADEBAUGH: What's so crazy is to think about

the fact that we could actually be descended

from viruses.

I am sure that a lot of my genetic

code originally came from the injection of a virus.

I love the idea that I might be descendant from a virus,

just coming from something that simple

and evolving into something

this complex is just a feat of nature.

ROWE: Viruses played a major part in human evolution.

Around 8% of human DNA came from ancient viral infections.

In fact, without them,

we wouldn't be human.

BYWATERS: In our brains, we actually have relic viral DNA.

So DNA that came from a virus,

but this helps us.

Without this, we don't think we would have consciousness.

ROWE: We also think that viral DNA helped us develop

an immune system

to fight off infection and gave us the ability to

digest starch.

The microcosmos has guided our evolution.

It even created the air we breathe.

But in doing so, it also triggered

the largest mass extinction the Earth has ever seen.

ROWE: Planet Earth, 2.5 billion years ago.

The microcosmos colonizes Earth's oceans.

This is not a world we would recognize today.

If you were to travel back in time, just on Earth, to see what

it was like 2.5 billion years ago,

it would look really different in many ways.

There were oceans, and they had life in those oceans.

But there weren't any land plants or land animals.

There was just bare rock.

So to think about a human going back in time to visit

the really early Earth,

they would find an utterly inhospitable planet.

LANZA: As a human, you'd be out of luck because there was

no oxygen in the atmosphere at that time,

so hopefully, you brought a space suit.

ROWE: The atmosphere was fine for

the billions of inhabitants of the early microcosmos.

They were very slow-paced, and they did

everything they did without any oxygen in the air.

ROWE: But this tranquil existence was about to change.

PLAIT: For a long time, conditions on Earth were

fairly static, but then, about 2.5 billion years ago,

an evolutionary glitch changed everything.

ROWE: A clue to that glitch

rests in strange rocky mounds,

stromatolites.

DARTNELL: Stromatolites are almost like microbial cities.

If you zoom down onto their scale, you'll see layer

upon layer of bacteria,

almost like the high-rise skyscrapers in one of

our cities.

ROWE: The microcosmic high rises are full of cyanobacteria.

These bacteria can photosynthesize.

Photosynthesis is a chemical reaction that

takes place inside a plant, producing food.

Today, it's an important part of our planet's existence.

2.5 billion years ago, it was revolutionary.

And it happened when ancient cyanobacteria similar to those

in the stromatolites mutated.

This mutation allowed cyanobacteria

to take the energy from sunlight and use it to make

sugars out of water and carbon dioxide.

ROWE: This gave cyanobacteria a huge evolutionary edge.

They could now make more energy for

themselves so they could grow and reproduce faster.

For everything else, it was a catastrophe.

It produced oxygen as a waste product.

Oxygen was no use to them, so they released it into

the air, transforming Earth's atmosphere

over millions of years.

ROWE: This by-product, oxygen, is extremely toxic.

THALLER: The reason oxygen is so dangerous is that

it's very reactive.

It loves to combine with everything,

so think about something rusting... iron rusts because

oxygen is actually combining with the molecules.

It's called oxidation.

So when oxygen was first released,

it was tremendously dangerous.

ROWE: The new oxygen built up in the atmosphere,

killing off species of microbes everywhere on the planet.

Right when this happened, you would have had

a mass extinction.

This would have been a global mass extinction event.

This was an unprecedented environmental disaster,

probably in the entire history of the Earth up to that point.

And I'm not even sure it's been paralleled,

even up to today.

This may have been the single

biggest catastrophe in our planet's history.

This was the Great Oxidation Event, and it changed

our atmosphere, it changed our planet,

and it didn't just end there.

Something changed again.

Another mutation allowed some of these bacteria to use that

oxygen in their own metabolism,

and that was a huge change.

ROWE: The ability to use oxygen was an incredible leap forward.

The beauty of oxygen is that it allows

the metabolism to process nutrients much more rapidly.

It basically helps bodies burn these materials so that

they can generate a lot more energy a lot more quickly.

Organisms that figured out how to use oxygen for respiration

ended up getting a huge kick-start

of energy and gave them a huge advantage

over other organisms.

It supplied enough energy that organisms could become

more complex,

larger, multicellular, really the tapping into

oxygen and being able to use oxygen in our metabolism meant

that it was a game changer,

that we could evolve in ways that never would

have been possible without cyanobacteria.

ROWE: Simple organisms became more complex.

Single-celled creatures became multicellular.

SHIELDS: This gradual accumulation of oxygen

into the atmosphere of the Earth

was huge for the multicellular animal and life explosion,

um, that occurred as a result and was

one of the most important events in Earth's history.

BYWATERS: This would have been a complete transformation

of the Earth's atmosphere and physical setting.

This is when the green Earth started to evolve.

ROWE: The Great Oxidation Event changed the course of evolution,

leading to our complex world.

It is really hard to overemphasize

the importance of the microcosmos.

Just the fact that I'm speaking to you,

I'm breathing in and out,

I wouldn't be doing that without

the tiniest organisms on the planet.

ROWE: The microcosmos gave us life.

Now, it could wipe us out.

Global warming is releasing

potentially lethal bacteria and viruses.

Are we facing a microcosmic zombie apocalypse?

ROWE: Siberia, present day.

Rising temperatures are melting the Arctic permafrost,

revealing land sealed under ice for tens

of thousands of years.

DARTNELL: As that permafrost begins thawing out

and melting with climate change,

maybe that will release pathogens that have

been locked up for potentially thousands of years.

ROWE: In 2014,

researchers investigated melting Siberian tundra,

a region larger than the USA.

I've seen a lot of science fiction movies where scientists

are digging around in the ice and find something bad

from a long time ago.

ROWE: Scientists took samples of

tundra soil to the lab and examined the contents.

They found a frozen ancient virus.

A virus locked in ice from over 30,000 years ago.

Isn't this the start of,

like, every horror movie? A scientist uncovers some deep

secret of nature and then just

open it up and unleash it on the world?

ROWE: Just like in a B movie,

The team fed the virus to

living single-celled creatures called amoebas

to see if the virus still functioned

after being frozen for thousands of years.

The virus woke up, attacked the amoebas, and replicated.

BYWATERS: Bringing this ancient virus back to life

was sort of waking up the undead.

ROWE: Scientists had no idea how this zombie virus would behave.

Something about it was very, very different.

It was huge compared to normal viruses.

It was substantially larger than any

virus that we had seen before.

This is the Goliath of Goliaths among viruses.

ROWE: So large it looks more like bacteria than a virus.

We call these kinds of giant viruses mimiviruses,

because they mimic other creatures, like bacteria.

ROWE: One way the virus mimics bacteria is

in the amount of its genetic material.

It has 900 genes, eight times as many as a regular virus.

SUTTER: Viruses are very simple.

They don't require a lot of genes to function,

but this virus has more genes than necessary.

What is it doing with all these extra genes?

ROWE: We have now found other mimiviruses.

20 years ago, we had no idea

that this complex type of virus even existed.

We still don't know what all the extra genes do.

This type of virus might even be able to generate

its own energy,

making it closer to bacteria than other viruses.

Because it has so many extra genes,

this is a virus that is not acting like a virus.

ROWE: We can't be sure how

the Siberian mimivirus will behave if released,

and even if it only attacks amoebas, there could be

other large, complex viruses buried in the ice.

They may not be so safe.

We know that there are large regions of

the Earth that are locked in ice right now.

There could be viruses that live inside that ice that if

the Earth gets too warm, could reactivate.

And these viruses could potentially be a threat to us.

ROWE: Recently, other dangerous frozen zombies

have reanimated, hidden in the dead.

We tend to think of people who died in

the past as not being able to affect us all, right?

They're gone, their germs are gone.

Unfortunately, this isn't exactly true.

So for people who are buried in tundra that's been frozen,

they never really disappeared.

And now, unfortunately, as the climate warms,

these tundra environments are releasing frozen people

and animals who died thousands of years ago.

ROWE: But it's not the dead people and animals

that threaten us... It's the microbes inside them.

In 2016, that threat became real

when another area of Siberia thawed.

A 12-year-old boy died,

and dozens of people needed medical treatment.

2,000 reindeer also perished.

The culprit? Reanimated bacteria called

anthrax inside a melting reindeer.

Anthrax is a common microbe found in soil.

In medieval times,

sometimes farmers would come back to find entire fields

of dead animals.

They didn't understand at the time what was going on.

They attribute it to cursed fields.

But we now know these are outbreaks of anthrax.

ROWE: The defrosted reindeer died nearly a century ago.

The anthrax that killed it was safely locked away in

the ice.

DARTNELL: The thawing out of regions

like the Siberian permafrost

could be almost like the inadvertent opening of

Pandora's box.

Once you open it, you don't know what's gonna come out.

DARTNELL: It could be releasing ancient preserved microbes,

bacteria, or viruses

that have been laying dormant for hundreds,

if not thousands of years.

LANZA: If these microbes are actually very different

from what we have on Earth today,

if we encountered these microbes, it's not really clear

what would happen with our immune systems.

You know, it could be totally fine,

but it could also wreak complete havoc on us.

ROWE: It's also not clear if modern drugs would

help us beat any ancient microbes we unleash.

Now, as humanity expands beyond Earth to new worlds,

will we carry our microcosmos with us into space?

Or have we already infected

our cosmic neighborhood?

ROWE: Space is no longer the final frontier of the future.

We're already exploring the solar system.

We've sent probes to the planets

and put boots on the moon.

Now, NASA plans to land astronauts on Mars

by the 2030s.

As a science fiction nerd myself, without even breaking

a sweat, I could name 10 movies

where people go to another planet, and some disease,

some alien life form, is unleashed on humans

and kills us all.

I think that has it exactly backwards.

If we try to settle on other planets, we have to be really,

really careful and really, really think about

how we are affecting them.

ROWE: As we launch more and more missions into space, we risk

sending Earth's microcosmos with them, endangering

the health of the solar system.

LANZA: And if we find a planet that actually has

its own biosphere, that has life of its own,

we need to be very careful about how we introduce

our microbes to their microbes,

because it could really be catastrophic for them.

PLAIT: It's serious, because we're looking at places

like Mars, like Titan,

Saturn's moon, like comets where life or at least

prebiotic life could have existed.

Or, in the past, there could

have been a much more habitable environment.

So it's entirely possible that we are polluting,

we are infecting these other objects with our own bacteria.

ROWE: If we contaminate a pristine world,

we won't know which microbes were there first.

Our bugs could even kill off the native ones.

It may have already happened.

OVER RADIO: You're looking good.

ROWE: The Apollo 12 mission brought back bits of the lunar

robotic probe Surveyor 3 it found on the moon.

Analysis of the probe found a bacterial contamination.

We don't know where it came from.

PLAIT: If that thing was infected before we sent it

to the moon, and it sat on the moon's surface

for two years in a vacuum, changing temperatures,

radiation from space, that really is telling us that

we can infect other planets and we should

take this very seriously.

SUTTER: We're ramping up our space missions,

we're sending probe after probe

to planets all throughout the solar system.

Taking care to not send our own diseases out onto

other planets is something we actually have to care about.

ROWE: NASA does care.

Before launching a new probe, a planetary protection team

deep cleans every inch.

You try to bake the spacecraft, you try to disinfect things.

You build everything and keep everything within a clean room,

which has a pressure that blows dust out.

Everybody wears what are called bunny suits,

so nobody touches anything directly.

But then, that's still not enough,

because microbes are incredibly hardy.

ROWE: It's even more difficult to kill microcosmic

stowaways if they're traveling inside an astronaut.

DARTNELL: In the not too distant future,

we'll start sending not robot explorers, not probes to Mars,

but people, an inherently dirty, mucky organism

like myself.

You can't sterilize a human.

You can't remove all bacteria.

We have to realize that we are bringing the microcosmos

with us, and we may change worlds entirely

without even noticing it.

Potentially, our impact could be absolutely devastating on...

On worlds that are either have life or emerging life,

and so we just need to take that responsibility seriously

and be careful with the way in which we explore them.

ROWE: Humans bear a responsibility

for the safety of the cosmos.

Our track record on Earth isn't good.

RADEBAUGH: When we look at the pattern of exploration

or colonization that we use as humans, we are really invasive.

We see a lot of destruction in our path,

and we have to wonder if that's what we're going to do

when we start to really explore and colonize

outside of Earth.

Like viruses, we also insist on spreading.

We insist on spreading around

our world, around our solar system.

There is a great chance

that we will cause utter destruction wherever we go.

ROWE: Our relationship with the microcosmos is complicated.

It's killed millions of people,

but without it, we wouldn't be here.

RADEBAUGH: This time we're living in is really causing us

to reflect on the microcosmos, and the better

we understand these microorganisms,

the better able we are to deal with what's happening today.

ROWE: The coronavirus crisis reminds us

we need to respect the world we cannot see

and recognize that the microcosmos is

every bit as important to us as the greater universe.

It's so easy, especially right now in history,

to hear the word virus and think about how harmful they

are, how dangerous they are.

But remember that you are actually a creature built

of viruses yourself.

As far as we know, we've never been without the microcosmos.

Microbes were here before us.

They'll probably be here after us, and we need them to live.

BYWATERS: The microcosmos... It's absolutely essential.

We couldn't function. We wouldn't survive.

We wouldn't be here without it.

But it's also our greatest ally,

and it's also our greatest enemy.