Original subtitles

(deep space music)

- [Narrator] This is the closest planet to Earth

in size and distance.

It once may have had oceans and a similar climate.

Now, it is hostile and unforgiving.

Scientists want to know why and how it changed.

This could help with the hunt for other habitable worlds.

For now, Venus could be considered Earth's evil twin.

(energetic orchestral music)

(soft wondrous music)

One of the brightest objects in the sky,

Venus has been a world of mystery and conjecture.

Probes were sent to briefly study the cloud tops

as they passed by,

the NASA Mariner Mission,

quickly followed by the Soviet Union series

of Venera Flights.

They left more questions than answers in their wakes.

Eventually, Venera 4 landed a probe

through the dense atmosphere onto a searing hot surface,

followed up with more sophisticated probes

that lived for a very short time.

Other probes floated briefly

in the dense poisonous atmosphere.

Mars became a much more attractive target,

and Venus has been left little explored.

In the late '80s, the Magellan Probe was launched

from the Space Shuttle.

It mapped the planet's surface with radar,

giving us a detailed look

at the rugged surface of the planet.

Stripping away the dense, thick atmosphere revealed

intricate mountains, volcanoes, and lava fields,

an uninviting and hazardous environment hot enough

to melt lead.

Following orbiters from both Europe and Japan

also studied the surface features with radar.

The Venus Express dipped

into the upper atmosphere to aerobrake

and descended into lower orbits.

In recent years, several probes have used Venus

for gravity assists to propel them to other destinations.

BepiColombo, on its way to study Mercury,

passed by taking images and other readings.

The maneuver, the second of Venus

and the third of nine flybys overall,

helped steer the spacecraft on course for Mercury.

Another European spacecraft,

the Solar Orbiter also utilized Venus for a slingshot

as it closed in on its solar orbit.

The Parker Solar Probe made a close flyby

taking measurements of the electric field of the planet

and the radio emissions from the hot surface.

(electronic screeching)

- [Brian] It's thrilling to be able to see something

that's never been seen before.

This emission that we're seeing is thermal emission.

Even on the nightside,

the surface of Venus is so hot

that it's glowing faintly at very red wavelengths.

- These WISPR images I think are really exciting

because they provide a new window

into the lower atmosphere and surface region of Venus

where these extreme conditions exist.

- [Narrator] A faint glow of heat from the nightside

shows distinctive features like continental regions,

planes and plateaus.

A luminescent halo of oxygen in the atmosphere

can also be seen surrounding the planet.

These observations revealed much

about the chemical composition of the surface.

- Another really interesting thing we could look for

is potentially mineralogical differences.

Different rocks and different minerals

emit different levels of heat.

- [Narrator] Some surprising results suggested

that water may have been on Venus in the past,

but climatic changes in planetary processes

removed the water from the planet and its atmosphere.

- We have chemical fingerprints in Venus' atmosphere

and on its surface suggesting

that Venus might have been habitable in the past.

- [Narrator] The Wide-Field Imager

or WISPR is the sole imager aboard the Parker Solar Probe.

- This is something that's truly new,

and I believe will yield exciting science in the longterm.

- [Narrator] Once upon a time,

Venus might just have been like an early Earth

with oceans, lakes, and rivers of liquid water,

a much milder oxygen-rich atmosphere.

What changed the environment?

(soft intense orchestral music)

Perhaps volcanic eruptions and toxic gases

creating an atmosphere of carbon dioxide

and sulfuric acid clouds trapping heat

in a greenhouse effect.

Venus has the hottest surface

of any planet in our solar system, hotter the mercury.

The atmospheric pressure is nearly 75 times greater

than that of Earth.

NASA and DSA are returning to the planet

to find some answers.

(gentle orchestral music)

Europe is sending the spacecraft EnVision

in partnership with NASA,

which is providing the synthetic aperture radar system

called VenSAR.

The S band radar will also act as a microwave radiometer

and altometer to map the surface.

EnVision will also carry three optical spectrum meters

designed to observe the surface and atmosphere of Venus,

and a subsurface radar sounder

that will probe the top kilometer of subsurface.

NASA will also be sending DAVINCI and VERITAS to Venus,

due to be launched around 2029.

VERITAS stands for Venus Emissivity, Radio Science,

InSAR, Topography and Spectroscopy Mission.

It will also map Venus's surface

to determine the planet's geologic history.

Germany and France are contributing

to the infrared mapper and radar systems to determine

whether active volcanoes are releasing water vapor

into the atmosphere.

DAVINCI the atmospheric probe will descend

into the Venusian atmosphere

to study the gases and chemistry with advanced sensors.

It is designed to survive the descent to ground level,

whilst imaging its journey.

The one-meter wide probe will target a region

called Alpha Regio, twice the size of Texas,

and will add to scientists' understanding

of rocky atmosphere-bearing exoplanets

that will be explored by new observatories,

such as the James Webb Space Telescope.

(low space music)

- [Glyn] So Venus is cool.

Venus is awesome.

Venus is, in many ways,

one of the most Earth-like planets that we know of.

One of the key ways that it's different

is that it's very, very dry.

With temperatures on the surface of 460 degrees centigrade

and whatever that is in Fahrenheit,

you would never expect there

to be liquid oceans on the surface.

That kind of temperature

only boils off that water into steam,

but the atmosphere of Venus is still incredibly dry.

So where did the steam go?

So to talk about how we remove something from a planet,

we're gonna have to talk about two forces of nature.

Firstly, the force of gravity.

Gravity is the thing

which is holding you down to the planet.

But if you think about it,

it's also what is holding the atmosphere down

onto the planet as well.

If I want to remove some of the oxygen from the planet,

we have to overcome that gravity.

So to do that, I wanna talk about the electric force.

It's the thing which your device is using right now

to pump electricity around its wires, right?

It's pushing the electrons around the circuits.

And what we think can happen is

that the electric force can help push on the ions

in the upper parts of the atmosphere,

push them off and up into space.

So just as every planet has a gravity field,

we think that every planet has a weak electric field.

So we went looking for Venus' electric field,

and boy oh boy did we find it.

It turns out that Venus' electric field is

at least five to 10 times stronger than on Earth.

It's a monster of a force.

It can rip heavy things like oxygen

straight out of the upper atmosphere

and send them kicking and screaming off into space.

So this really changes the way

we have to think about planets

'cause it turns out

that planets can lose heavy things like oxygen to space

entirely through electrical forces in their ionospheres.

This is something that's really important

if we want to go looking for exoplanets,

for habitable planets around other stars.

It is no good having conditions perfect for an ocean

and an atmosphere you might wanna breathe

if some invisible force is going to come along

and rip it all off into space.

It's only understanding how atmospheres evolve

can we try and understand how we got here.

(soft wondrous music)

- [Narrator] Many orbiting telescopes

and instruments are now in use to search for,

identify, and catalog exoplanets,

planets orbiting other stars.

TESS, Kepler, Hubble, James Webb,

and the Nancy Roman telescopes are looking

at planetary formations around various stars.

Knowing how Venus evolved would give additional assistance

to the planet searches.

This image is of a new star in its gas disc.

The black rings show where planets are forming

by gathering the dust and debris.

This image reveals a moon forming

around a gas giant as it evolves.

This massive exoplanet orbits a white dwarf,

the remnant of a dead star that is slowly evaporating.

- Another big unknown is to characterize planets

that are orbiting other stars.

So we could now...

Astronomers have got very good at finding these planets,

but what we want to do is look at what they're made of,

so what's in their atmospheres,

or if they were rocky,

what kinds of minerals are we seeing.

And to be able to do that I think will be stupendous.

- So this, we can see the composition

of the atmosphere in exoplanet, so what it's made of.

And the specific planet we're looking at is hot.

And so what we see in that is that there's water there.

It wouldn't be in liquid form because the planet's hot,

so it'd be more like steam that's around it.

But we can tell what's in that atmosphere.

- So the James Webb Space Telescope is brilliant

in a number of ways.

One, it extends our wavelength

all the way into the infrared,

into the mid infrared.

So we can look for these heat signatures

from these planets as well.

But that also means we can cover the fingerprints

of different materials in the atmosphere.

So the Hubble Space Telescope looks

for fingerprints of sodium and potassium and water

in the atmospheres of these worlds.

But the James Webb Space Telescope's gonna be able

to look for signatures of methane and carbon dioxide

and carbon monoxide,

as well as all of these wonderful water features

that we'll be seeing in these giant planet atmospheres.

But not only can it tell us

in these different wavelength ranges,

it's actually better resolution.

So we can get more data points

for each of these different molecules.

And it's a much bigger telescope.

We're collecting far more light.

We can get a much better precision.

So that means that the degree

to which we believe our measurements

is going to improve a lot with this telescope.

That's gonna mean that we'll be able to tell you

with confidence what we're measuring.

Looking for life on other planets

is the ultimate future goal of all of these missions,

trying to understand how we got here,

how the earth is the way it is.

The James Webb Space Telescope's taking us one step further

towards that goal.

We're gonna be pushing to these smaller worlds

where we can see what different planets

that are unlike ones in our solar system are like,

how atmospheres change with the size of your planet.

And it's also going to give us information

on these giant planets

that we don't have in our solar system,

so close to their star, that they're hotter than a rocket.

There are different worlds that we can explore with this.

And every technique that we use

with the James Webb Space Telescope

is going to be the technique we need

to be looking for life signatures on these other worlds.

So getting good at using this technique is so important,

so that in the future we can be looking

for these signatures.

- [Klaus] So what we see here

is what's called a hot Jupiter.

So it's a planet that moves in front of its star,

and it has about the size of Jupiter,

but the mass of Saturn.

And what we see here is light filters

through its atmosphere,

and that allows us to look

for the fingerprints of certain molecules.

And in this case, the planet is full of water vapor,

full of water.

And that's what you see as wiggles in the spectrum.

When we go and look at other exoplanets with Webb,

we may look for other molecules,

some that are familiar in our own atmosphere here as well,

like carbon monoxide, carbon dioxide,

maybe even methane and ozone.

- [Narrator] The total so far exceeds 5,000 exoplanets,

with a further 8,000 to be confirmed.

Of particular interest are the smaller rocky

Earth-like planets.

- [Kate] We know our targets.

They're bright stars which are known

to host the type of planets we want to observe.

And we will know when these planets transit.

That is when the planets move across the disc of the star

and we can measure the changes in the output of the star,

the measured output of the star,

in order to measure the size of the planet.

We'll be focusing on smaller planets,

so Earth-size to Neptune-size planets,

which have been found by other missions such as Kepler

to be very abundant around other sun-like stars.

Something which is not so much the case

in our own solar system.

So it's a big question.

What are these smaller planets?

What are they made of?

- [Narrator] The range of planet types is amazing,

rocky worlds that sustain oceans and lakes,

likely candidates for life.

Others more extreme like WASP-76b,

tightly locked to its star,

only ever showing one face to its sun.

This extreme exoplanet has a dayside where metals evaporate,

and a nightside where it rains iron.

(low droning music)

Rogue planets that have no sun to orbit,

ejected from their solar system

and left to roam through space.

(wondrous orchestral music)

Planets that have the heavy element barium

in their atmosphere.

Water worlds, planets still forming,

others around dying stars.

(moves to soft orchestral music)

(violins begin)

(moves to upbeat orchestral music)

We must remember that amidst all these searches

for a new Earth,

we must take care of the one we have

because it is a very long way to travel

to reach these other habitable worlds.

(low space music)