Original subtitles

(piano music)

- [David] There's one very tantalizing possibility about

the clouds of Venus, which is that some of us think that

it's plausible, that there could be life in the clouds.

- [Sanjay] Something is absorbing sunlight

in the clouds of Venus.

Maybe there's some microorganisms.

Venus has a habitable zone in the cloud layer.

So life could exist there.

- Four and a half billion years ago,

we had three terrestrial planets, all with oceans,

life evolved on one.

Everything that we know about chemistry, about physics,

about geology suggests that those conditions were there

on Mars and Venus, too.

- The presence of liquid water,

the presence of organic molecules,

the presence of some kind of energy sources and some sort of

stable enough environment for interesting chemistry

to happen and take root.

There's every reason to believe

there was an origin of life on Venus.

We don't know if there was,

but if we're correct about what it required on earth,

there's no reason to think it didn't happen on Venus.

- We know on earth that once life forms,

however that happens, life, life is tenacious.

Earth is dripping with life right now.

It's in every crevice. It's an it's in the atmosphere.

It's in every niche that we have on earth

after 4 billion years, it's it's everywhere.

So in my mind,

if the environment is driving the evolution of life,

those environments were certainly there

four and a half million years ago on those three planets.

- And so it may well have been that Venus and Earth

and Mars too, for that matter

all three planets seem to have had those conditions

for an origin of life and habitability early on.

It may be that,

that our system had multiple nearby habitable planets.

And if there was going to be life on Venus, you know,

life as we know it, made out of carbon molecules and such,

it could not be on the surface of the planet.

It's just too hot, but there is an environment in the clouds

where it's at least plausible there could be some

sort of biota.

So in addition to all the other reasons we want

to study the atmosphere and the clouds of Venus,

there's this exotic possibility that we could even,

who knows, maybe discover life there.

- My Venus atmosphere friends talk about the fact that

there is a signature in the atmosphere

that they can explain.

And there is something in the clouds

that absorbs UV radiation,

and they don't know what it is.

That signature may be due to

absorption by biota, by cloud creatures.

- Venus is completely covered with clouds.

If you actually look at Venus through a naked eye,

you don't see any detail at all.

The cloud cover is almost like a fog bank that's global,

from fritter to pole.

And within this fog of these patches,

you can see these patches moving very rapidly.

The Venus winds are extremely fast, but these patches,

they are a mystery.

You know, these patches would have seen

from most telescopes more than a century ago.

The mystery has remain for all this time

as to what is causing that absorption,

these patches are because something is absorbing sunlight

in the clouds of Venus.

Bacteria could be the absorber.

We know on Earth that the clouds harbor bacteria.

- We have life in the clouds of the Earth.

Now that life comes from the surface of the Earth

and has been transported up.

Lifeforms can exist in the clouds.

And there's certainly enough energy in the clouds to support

life on Earth. And maybe on Venus.

You need water, you need something for it to eat.

The temperatures in the clouds of Venus

are shirtsleeve weather. Okay?

So that's not a problem.

- The temperature and pressure conditions

in Venus's atmosphere

are pretty similar to what we experience here on Earth.

So similar temperatures may be a little warmer

than we're used to.

The main difference at that part of the atmosphere

of course, is the carbon dioxide and the sulfuric acid

that makes up the cloud layer.

But it's possible.

We know of organisms that can thrive

in those types of environments on Earth.

- The one impediment to life,

maybe the strong acid in the clouds,

but we've learned more recently of all these

extremophile organisms on earth,

including what we call Acidophilic organisms;

organisms that love living in strong acid.

The more we've learned about strange life on Earth,

the more we sort of dare contemplate the possibility of

life in strange environments on other planets.

- If Venus had habitable conditions for much of its history,

then it's possible that life could have evolved to live in

all kinds of ecological niches.

Just like life has on Earth.

Earth has had 4 billion years for life to fill every

ecological niche possible.

And we find life everywhere we go, we dig deep wells

we find life down there. We find life in the clouds.

And then there's another school of thought

that there would be a kind of a panspermia type of event

where there is mass exchange between the planets.

There is a really good chance that rocks from Earth

or even from Mars would have ended up on Venus.

And if those carried extraordinarily robust organisms

extremophiles, as we call them here on Earth,

they could also populate different aspects

of the Venusian atmosphere.

- If we have the opportunity to go to Venus

and float in the Venus clouds,

we should at least think about

if we can measure the conditions that might be reasonable

for life today,

and also any signature of life in the clouds of Venus today.

- If you want to look for life, you know,

right now we have about five objects.

We have a Venus, we have Mars, Europa, Enceladus,

and Titan.

I think of these five objects, I would argue that

Venus should be a top priority.

At least in the case of Venus, the search should be easy.

You can launch today a space car toward Venus

and be there in about three to five months.

So the journey is quick,

you don't have to wait for your children to analyze the data

that you work hard to update.

You don't need to find a place to land on Venus.

Look for life. On Venus, go anywhere in the clouds,

in the low latitudes. And if there's life,

you should find it because it's there everywhere.

If it is there at all.

(pensive music)