All language subtitles for Exploring.Venus.S01E05.WEBRip.x264-ION10_English

(suspenseful ethereal music)

- [Sue] Venus and Earth
are the twin planets.

We've seen thousands of
exoplanets around other stars

but Venus is still the
planet most like Earth.

- [Tony] The surface of Venus
is hot enough to melt lead.

- [Jonathan] Venus is incredibly hot,

it has what we call a runaway greenhouse,

where it's sort of the
extreme state of what happens

if you let a greenhouse
go completely crazy

on an Earth-like planet.

- [Rosaly] Venus is kind of a warning

that we have to pay
attention to what's happening

to the atmosphere of the Earth.

We don't want the Earth
to become evil like Venus.

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- Venus and Earth are
actually really similar

in many, many ways.

They are almost exactly the same size,

and they have similar gravity.

Venus has about 90% of Earth's gravity.

And we think that they both
formed in a similar part

of the solar system at about the same time

from more or less the same materials.

So they, they really should
have a lot of similarities,

we see they both have atmospheres,

they both show the same
types of geologic processes

on their surfaces with volcanoes

and tectonic regions,

which is where the crust is moving around.

- It's the only planet

that is likely to be
still geologically active

in some of the same ways as, as the Earth.

It has a similar bulk composition.

It has an atmosphere, a huge atmosphere,

one of the very few
plants in our atmosphere

to have a huge atmosphere.

- [Lori] That thick carbon
dioxide atmosphere acts

as a greenhouse,

warming the surface to
hundreds of degrees Fahrenheit,

and pressures that are
like being about mile deep

in the ocean.

At Venus, there's no magnetic field,

whereas at Earth, there is.

- [Rosaly] So Venus is kind of
the Earth's evil twin sister.

It shows how two worlds of
similar size, similar density,

not that far apart in terms
of distance to the sun,

evolved very differently.

- So the real core
question it comes down to

is what was it in Venus's
and Earth's history

that made these two similar planets

take very different paths.

And then how do we apply that

to planets beyond our solar system

and look at how understanding
Venus could help us

better understand what
exoplanets are like,

and which ones are the ones

that could potentially
harbor life like Earth?

And which ones are those
that are like Venus

and are very hostile to life?

- [Mike] We believe that
Earth and Venus formed

around the same time in our
original circumstellar disc.

They are probably
geo-chemically very similar

because they formed very close
to each other in the disc,

much closer than Earth did
to Mars and from what we know

about the geo-chemical similarities
between Venus and Earth

and Earth and Mars,

certainly we believe that
Earth is more similar to Venus

than it is to Mars.

We don't know that much about Venus

because we haven't sent
enough missions there

as we have for Mars.

It does have similar
amounts of carbon dioxide

in its surface and in its
atmosphere compared to Earth.

- Venus is, in some
sense, the poster child

for the greenhouse
effect of carbon dioxide.

It's a planet that has
much more carbon dioxide

than the Earth has in its atmosphere.

And even though it is covered

by this bright sulfuric acid haze,

Venus reflects 70-something
percent of the sunlight

that reaches it, so even
though it's very close,

it actually doesn't get
nearly as much sunlight

as you imagine because of that haze.

Yet it's got this crushingly hot surface.

And the only way to explain that

is because of the greenhouse
effect of the carbon dioxide.

Venus tells us

that the greenhouse effect
is a real phenomenon.

- [David] Venus, in many ways,

is an extreme case of some of
Earth's environmental issues.

I mean, the most obvious
one being global warming

and the greenhouse effect,

which is something we're
all obviously aware of

here on Earth because the
amount of CO2 has risen

above 400 parts per million,

and that is causing global warming

because of the infrared absorption of CO2.

And yet here's Venus, the
Earth-sized planet next door

with an atmosphere that
is almost 100% CO2.

Venus, as far we can tell,
was a habitable planet

for some time

before it went through this
runaway greenhouse transition.

- Imagine a graph where we have,

you know, temperature versus CO2.

And so Earth is in this section over here,

right, 'cause we have this much CO2.

So if we want to understand this process,

Venus offers data up here, right?

Another set of data points that we can use

to sort of link how much CO2
do we need before this happens?

When do we get into a position
where we're really in trouble

and there's nothing we can do about it

except move to Mars?

- [Tony] We don't expect the Earth

to turn into Venus anytime soon.

Humankind is putting more
and more carbon dioxide

into the atmosphere

as humankind has been doing
now for a few centuries,

since the Industrial Revolution began.

We know that the climate
is going to get warmer.

How warm it will get depends

on how much carbon dioxide
we put into the atmosphere.

Humans are not going to be able

to put enough carbon
dioxide into the atmosphere

to turn the Earth into Venus.

- So there's this whole long-term cycle

where the carbon comes out of volcanoes

and ends up in the atmosphere

and then gets pulled out by chemistry

and made into carbonate rocks,

which get deposited on the ocean floor

and then subducted by plate tectonics

into the interior of the planet

and ultimately sort of heated and squished

to the point where the carbon
dioxide is, is released

and then comes out again in a volcano.

That's a cycle that
takes millions of years

and it ultimately regulates the carbon

in Earth's atmosphere, of course,

recently, we've been perturbing
it with our automobiles

and smoke stacks and things,

but that's all probably a
temporary sharp perturbation

in what is a multi-million-year cycle

that's been operating
for billions of years.

Now, compare that to Venus.

We think that early on Venus
probably had a similar cycle

because it has volcanoes,
it had volcanoes,

it's probably been volcanically
active its whole life.

And it used to, we believe, have an ocean

which facilitated those
weathering reactions

that pull carbon dioxide
out of the atmosphere.

- Part of the issue is that
Venus no longer has an ocean.

We think it had an ocean
earlier in its history,

we don't really know when water was lost.

Having an ocean is an important part

of pulling carbon dioxide
out of the atmosphere.

We think that Earth and
Venus have similar amounts

of carbon dioxide.

But, on Earth, those are
locked up in carbonate rocks.

And those carbonate
rocks often are subducted

back into the interior,

sequestered, in effect,
by geologic processes.

- [Martha] So you need an ocean.

And we hope that we can find evidence

in early Venus history of sequestering

of carbon in rocks.

That's what we look for on Mars,

that's, a lot of Mars
work has been to look

for those carbonate rocks on Mars.

What Venus shows us, without a doubt,

is that there is a relationship

between the amount of CO2
you have in an atmosphere

and the temperature.

- [Sue] Will the Earth
become 500 degrees Celsius,

900 degrees Fahrenheit?

That's really not likely to happen.

But understanding chemical reactions

in this very active
atmosphere that Venus has

is so important for
being able to understand

how climate change comes about.

What are the important chemicals,

what are the important processes?

So we really have a lot to learn

from the atmosphere of Venus.

- [David] For example, acid
rain is a problem here on Earth

because of sulfur dioxide
from our smoke stacks

getting into the clouds
and mixing with water

and making strong acid.

Well, Venus, again, is sort
of the poster child for,

for that condition with clouds

that are basically made
out of purer sulfuric acid,

and so it's, it's a place

where we can study this
environmental problem, acid rain,

in its most extreme manifestation.

And to give one more example,

another problem of our own making

is the problem with the ozone hole

and the ozone layer being eroded

by these chemicals,
these chlorofluorocarbons

that we released into the atmosphere

where the chlorine gets loose

because of ultraviolet
light in the stratosphere

and destroys ozone, which
then becomes a threat

to life here on the surface of the planet.

Well, one of the ways we
discovered the ozone layer

was being eroded on Earth came about

because we were studying the
upper atmosphere of Venus.

- [Sue] Venus's atmosphere
is so intriguing.

We actually found the
ozone hole on the Earth

because people were studying chemistry

of what was going on in the atmosphere,

upper atmosphere of Venus.

- Some scientists were
trying to understand why,

why isn't there more ozone on Venus,

why aren't there more oxygen compounds

in the high atmosphere of Venus?

And some other scientists
said, well, you know,

we've seen these experiments with chlorine

and chlorine can, can
destroy oxygen compounds.

And then they came out with a paper

saying we think it's chlorine
that is destroying ozone

on Venus.

Some other scientists saw that paper.

- And it made them ask
this question, well,

what's going on in the
upper atmosphere of Earth,

are there similar types of
chemical reactions going on?

- And they said, oh, that's interesting,

what about these, these chlorine compounds

that we're putting up into
the atmosphere on Earth,

that, couldn't that, and they
said, uh oh, wait a minute.

And that helped them
realize what was happening

and help them sort of sound the alarm.

- Look at that huge
difference that that made

in terms of discovering
the ozone hole on the Earth

and, you know, since
people have taken action

to actually stop putting those
chemicals into the atmosphere

that was creating such
a destructive process.

- And, indeed, that's an
example where we've responded

in a healthy way to this knowledge

that we were doing something to our planet

and have taken measures to fix it.

And it came about

partly because we were studying
this neighboring planet

out of pure curiosity,

trying to understand the chemistry there.

- The link between innovation
and expanding our thinking

is not linear.

In science and technology,

you don't plan for that necessarily,

you don't say, okay, I'm gonna
discover this great thing,

and I'm gonna start here,

and I'm gonna, at the end
will be this great discovery.

That comes from a lot of
tries and a lot of failure.

And if we don't push at the limits

of what we can do as a
society, we won't succeed.

That's the way it works.

That's what we do as scientists.

That's why we sail across the ocean.

That's why we climb the mountain.

And that's why we should go to Venus.

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