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NARRATOR:
When we look beyond Earth,

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we discover dynamic worlds.

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KATHERINE DE KLEER:
As we're exploring
the solar system,

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we are finding

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remarkably diverse

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and ferociously active worlds.

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CLARA SOUSA-SILVA:
Where lava flows,
where volcanoes erupt,

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where rumblings beneath
crack the surface.

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NARRATOR:
From giant, dead volcanoes

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on the planet next door...

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JAMES DOTTIN:
It's absolutely mind-boggling

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that there are volcanoes
that can get that big

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that it can tip a planet.
That's absolutely crazy.

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NARRATOR:
...to active ice-cold eruptions

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on frozen moons.

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PAUL BYRNE:
Where everything's frozen over,

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we see volcanic eruptions
blasting out into space,

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and that's a real surprise.

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NARRATOR:
These explosive worlds

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could even provide a clue

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to one of the biggest questions
of them all.

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JEN GUPTA:
Studying volcanoes
in the solar system

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is incredibly important.

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It can help answer that question
of where you and I came from

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and even how life first began.

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NARRATOR:
But ultimately,
volcanoes, fiery or frozen,

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reveal the incredible activity
that lies within.

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When I think of a volcano,

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I think of awesomeness and...

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how can I get a ticket
to go there?

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NARRATOR:
How can there be so many

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different kinds of eruptions
across our solar system?

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And what might
Earth's volcanoes tell us

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about the possibilities
of life elsewhere?

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"Solar System: Volcano Worlds."

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Right now, on "NOVA."

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♪ ♪

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NARRATOR:
Humans have only set foot

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on one world beyond our own.

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On the moon,
we found a barren landscape,

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appearing unchanged
for more than a billion years.

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Its surface, scarred
with craters and dark patches.

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This was activity that occurred
early on in the moon's history.

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The moon now, there isn't much
going on there.

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NARRATOR:
Our moon is an inactive world,

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frozen in time.

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In stark contrast with Earth.

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Which seethes with activity
beneath the surface.

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Who doesn't love a volcano?
I mean, hot stuff

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jumping out
of the ground at you.

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It would be really exciting.

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OLUSEYI:
I've seen erupting volcanoes,

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and I just love active geology.

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It just tells me
that the planet is alive,

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not literally, but figuratively.

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NARRATOR:
And when we look beyond
Earth and its moon,

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out into our solar system,

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other dynamic worlds like ours
do exist.

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As we're exploring
the solar system,

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both with telescopes
and with spacecraft,

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we are finding
remarkably diverse

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and ferociously active worlds
throughout the solar system.

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NARRATOR:
Many hold clues
to our own planet's story.

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JASON HOFGARTNER:
Looking at volcanoes
elsewhere in the solar system,

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we see that Earth has a special
type of volcanic activity,

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and so, by understanding
other volcanoes,

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we might understand how Earth

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had eruptions in the past
or in the future.

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NARRATOR:
And since many scientists
think volcanic activity

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might have played a major role

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in the origins of life
on Earth...

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...other active worlds
in our solar system

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are especially intriguing.

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SOUSA-SILVA:
We know that
there's a relationship

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between volcanism and life,

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but we don't know where it ends
and where it begins,

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and that's why
we need to keep exploring.

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♪ ♪

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NARRATOR:
The largest volcanoes

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discovered
in the solar system so far

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are right next door.

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Mars is one of the most
explored and photographed

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of all the planets beyond Earth.

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We've captured its stark beauty.

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From ice frosted dunes

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to canyons
just over six miles deep.

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And many of the most
detailed images

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have come from
the Mars Reconnaissance Orbiter.

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Launched in 2005,

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it is still orbiting
the planet today.

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JORGE NÚÑEZ:
It carries instruments,
high-resolution instruments,

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that allows us
to view and explore

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the surface of Mars
in such detail

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that we could map out

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things the size of a desk
on the surface.

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OLUSEYI:
It's the length of a school bus

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with these two big solar panels
to power it,

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and as it's going
about its business,

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it's sent back
more data to Earth

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than any mission ever.

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NARRATOR:
These images show in
greater detail than ever before

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giant volcanoes

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that dwarf anything
seen on Earth.

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One so wide...

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...it would cover
the length of Nevada.

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And one so tall...

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...it reaches over twice
the height of Mount Everest.

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It's the largest volcano
in the solar system.

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Lava once flowed
from these giants,

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spilling across the land
in all directions.

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So much molten rock

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that the combined mass

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tipped the planet over
on its axis

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by about 20 degrees.

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How did these monsters
get so big?

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A hint comes from studying
active volcanoes

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here on Earth.

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OLUSEYI:
If you want to understand
volcanism on Earth,

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or if you just want

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to understand Earth at all,

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you need to start with
plate tectonics.

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NARRATOR:
Earth's crust is made up
of seven large plates

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and several smaller ones,

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which interact with each other
at their boundaries.

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AISHA MORRIS:
And they interact
in multiple different ways.

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They can be smashing
into each other,

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pulling apart from each other,

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or grinding against each other
as they move around.

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DOTTIN:
So at plate boundaries,

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what happens is that

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you end up with
rock instabilities

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and, ultimately,
the rock melts.

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NARRATOR:
Creating the conditions

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that have formed the majority
of volcanoes on Earth.

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But it's the volcanoes that
don't form at plate boundaries

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that tell us the most
about Martian volcanoes.

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GUPTA:
On Earth, we also have volcanoes

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in the middle of a plate,
not just the boundary.

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These are called
hotspot volcanoes,

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and Hawaii is a
great example of this.

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DOTTIN:
Hotspot volcanoes

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are typically created
by a plume,

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like a bubble of hot magma

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welling up directly
from the interior,

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hitting the bottom of the plate
and bursting through.

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NARRATOR:
Hawaii is a chain
of hotspot volcanoes,

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created by a tectonic plate

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moving across
a single plume of magma,

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erupting onto the surface

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forming a line of islands.

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Like on Earth,

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Mars has hotspot volcanoes,

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but with one major difference,

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no plate tectonics.

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On Mars, instead of the plate
moving over the plume

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and making a chain of volcanoes,

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you get the plume stationary,
with respect to the ground,

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and that means,

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over millions or even
billions of years,

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Mars has been able
to build up volcanoes

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that dwarf anything
that we see on Earth.

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NARRATOR:
But all of those
monster volcanoes have quieted.

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Still and cold
for millions of years.

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Why?

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To find the answer,

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scientists look deep within,

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tracing the source of heat
that drives volcanism

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on rocky planets like ours.

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Four and a half
billion years ago,

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with the rest
of the solar system,

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the Earth formed
from the collapse

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of a cloud of gas and dust

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being smashed together

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under the force
of its own gravity.

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NARRATOR:
Much of the energy
that went into these collisions

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turned into heat,
trapped inside Earth.

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Added to that is heat
from radioactive elements

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inside the planet, like uranium.

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So over time,

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these elements actually decay

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into lighter elements

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and as they do so,

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they are constantly warming
and heating our planet

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from the inside.

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When you stop
and think about it,

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it really just is incredible
that all of this heat

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that is powering volcanoes
here on Earth

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can be traced back four
and a half billion years ago

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to the formation of the Earth.

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♪ ♪

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NARRATOR:
Mars shares
Earth's origin story.

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It formed in the same way...

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...at the same time...

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...capturing enough heat
to drive volcanism

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on a staggering scale.

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But now the volcanoes are
cold and silent.

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Where did all that heat go?

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00:12:05,738 --> 00:12:09,505
A clue exists
within this volcanic landscape.

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In Mars's northern hemisphere
lies the Marte Vallis area...

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...where cliffs are built

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from an intricate array
of pillars.

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00:12:22,605 --> 00:12:25,071
Arranged in uniform patterns,

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these structures are made
of solidified lava.

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Similar structures also exist
here on Earth...

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...and they can help
unravel the mystery

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00:12:38,938 --> 00:12:43,205
behind why Mars's volcanoes
are now silent.

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PAUL BYRNE:
We see columnar jointing

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00:12:48,838 --> 00:12:50,405
in lots of places on Earth.

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00:12:55,038 --> 00:12:57,338
There's a particularly
beautiful example

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in the Studlagil Canyon
in Iceland.

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NARRATOR:
Hot lava once flowed here.

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00:13:04,271 --> 00:13:07,638
As it cooled,
it did something extraordinary.

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PAUL BYRNE:
As that lava's cooling down,

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it's shrinking,
it's contracting.

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00:13:13,538 --> 00:13:16,705
And as the lava pulls apart
from itself, as it contracts,

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it makes these fractures

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00:13:18,471 --> 00:13:20,938
and these fractures form
this very regular,

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00:13:20,938 --> 00:13:22,305
even pattern.

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NARRATOR:
Exactly what conditions cause

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00:13:26,238 --> 00:13:29,371
these unusual structures
to form is complex.

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00:13:30,838 --> 00:13:32,238
But they do reveal

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00:13:32,238 --> 00:13:36,005
one of the most fundamental
laws of nature.

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00:13:36,005 --> 00:13:37,105
DOTTIN:
The simplest explanation

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00:13:37,105 --> 00:13:40,138
for the second law
of thermodynamics

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00:13:40,138 --> 00:13:43,238
is that heat flows
from hot to cold.

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00:13:43,238 --> 00:13:45,938
So if you were to go outside
on a cold day

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00:13:45,938 --> 00:13:48,438
with a hot cup of coffee,
eventually,

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00:13:48,438 --> 00:13:51,205
that hot cup of coffee will be
the same temperature

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as your outdoor surroundings.

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NARRATOR:
More than 65 feet tall,

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these columns show
this very principle in action.

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00:14:04,171 --> 00:14:07,205
BYRNE:
So we can think of how, say,
columnar joints form

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00:14:07,205 --> 00:14:11,171
through that lens of energy
flowing from hot to cold.

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When the lava flow is
flowing over the surface,

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00:14:14,205 --> 00:14:15,871
in the case of Earth, at least,

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it's much hotter than both
the ground and the air.

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00:14:20,705 --> 00:14:22,771
NARRATOR:
As the lava cools,

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00:14:22,771 --> 00:14:25,971
its heat rises
into the atmosphere

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00:14:25,971 --> 00:14:27,871
and then out into space,

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00:14:27,871 --> 00:14:31,038
slowly cooling
the entire planet.

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♪ ♪

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TRIPATHI:
The beautiful truth
about physics

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00:14:35,371 --> 00:14:38,705
is that the laws are the same
everywhere.

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00:14:38,705 --> 00:14:41,638
So the laws of thermodynamics
work on Earth,

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00:14:41,638 --> 00:14:43,938
they work on Mars,
they work beyond.

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00:14:46,471 --> 00:14:48,938
NARRATOR:
The physics may be the same:

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00:14:48,938 --> 00:14:52,438
volcanoes driven
by ancient internal heat

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00:14:52,438 --> 00:14:54,405
moving towards equilibrium

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00:14:54,405 --> 00:14:56,605
with the coldness
of outer space.

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00:14:59,105 --> 00:15:00,338
But one key difference

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00:15:00,338 --> 00:15:02,805
caused a big change
in how quickly

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00:15:02,805 --> 00:15:04,505
Mars lost its heat.

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00:15:07,071 --> 00:15:08,671
OLUSEYI:
If we look at these two balls

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00:15:08,671 --> 00:15:12,438
as an example for Earth--
the baseball--

255
00:15:12,438 --> 00:15:15,271
and Mars-- the golf ball--

256
00:15:15,271 --> 00:15:16,738
then they're different sizes.

257
00:15:16,738 --> 00:15:19,305
So as the object gets bigger,

258
00:15:19,305 --> 00:15:22,971
the volume grows faster
than the surface area grows.

259
00:15:22,971 --> 00:15:28,138
In spite of having a volume
that's only 15% of the Earth,

260
00:15:28,138 --> 00:15:31,105
Mars's surface area is,
actually, bigger proportionally.

261
00:15:31,105 --> 00:15:32,738
It's got about 28%

262
00:15:32,738 --> 00:15:35,171
of the surface area
of the Earth.

263
00:15:35,171 --> 00:15:36,771
You can think of it this way.

264
00:15:36,771 --> 00:15:40,238
If I make a big pot of coffee,
it's gonna stay warm for hours.

265
00:15:40,238 --> 00:15:42,905
If I pour some of that coffee
into a mug,

266
00:15:42,905 --> 00:15:45,438
it'll cool down much faster
because there's less of it,

267
00:15:45,438 --> 00:15:46,938
but there's more surface area.

268
00:15:46,938 --> 00:15:49,105
And these differences
have resulted

269
00:15:49,105 --> 00:15:51,671
in so much of what we see today,

270
00:15:51,671 --> 00:15:54,738
including the geologic
and volcanic history

271
00:15:54,738 --> 00:15:56,138
on the two worlds.

272
00:15:56,138 --> 00:15:58,171
♪ ♪

273
00:16:02,171 --> 00:16:04,071
NARRATOR:
Earth and Mars started out

274
00:16:04,071 --> 00:16:09,905
with similar materials:
heat and volcanic activity.

275
00:16:11,671 --> 00:16:15,871
But while Mars's heat
and its volcanism ebbed away,

276
00:16:15,871 --> 00:16:19,405
Earth's volcanoes continue
erupting to this day.

277
00:16:21,505 --> 00:16:24,438
And many scientists believe
that on Earth,

278
00:16:24,438 --> 00:16:28,005
volcanism on the ocean floor
played a role

279
00:16:28,005 --> 00:16:29,871
in life's beginnings.

280
00:16:32,105 --> 00:16:34,905
So with such similar
origin stories...

281
00:16:35,871 --> 00:16:38,905
...could there once have been
life on Mars?

282
00:16:40,438 --> 00:16:42,538
NÚÑEZ:
Mars is like Earth's cousin.

283
00:16:42,538 --> 00:16:45,171
And so very early
in their history as they formed,

284
00:16:45,171 --> 00:16:47,438
they had this volcanic activity,
and we found evidence

285
00:16:47,438 --> 00:16:51,105
that Mars had liquid water
on its surface.

286
00:16:51,105 --> 00:16:53,805
It had a thicker atmosphere.

287
00:16:53,805 --> 00:16:55,538
And around the same time

288
00:16:55,538 --> 00:16:58,438
that we know that life emerged
here on Earth,

289
00:16:58,438 --> 00:17:02,471
there was liquid water
on the surface of Mars

290
00:17:02,471 --> 00:17:07,505
and it had conditions
very similar to early Earth.

291
00:17:09,138 --> 00:17:13,738
NARRATOR:
Today the Perseverance rover,
on Mars since 2021,

292
00:17:13,738 --> 00:17:18,305
is creating packages of rock
samples with the intention

293
00:17:18,305 --> 00:17:22,005
that a later mission will
one day return them to Earth.

294
00:17:23,671 --> 00:17:27,338
Could they contain evidence
of Martian life?

295
00:17:29,105 --> 00:17:32,171
DOTTIN:
So generally, in these rock
samples from Mars,

296
00:17:32,171 --> 00:17:33,738
we're looking for signatures

297
00:17:33,738 --> 00:17:36,205
that there was life
on the planet.

298
00:17:36,205 --> 00:17:38,905
But it would be
absolutely amazing

299
00:17:38,905 --> 00:17:42,838
if we actually found cells
or something similar

300
00:17:42,838 --> 00:17:44,471
in these rocks that indicated

301
00:17:44,471 --> 00:17:46,805
that there is life
on Mars today.

302
00:17:48,238 --> 00:17:53,038
NARRATOR:
For now, any secrets of life
on Mars remain a mystery.

303
00:17:54,305 --> 00:17:57,071
But what Mars does demonstrate

304
00:17:57,071 --> 00:18:01,971
is the smaller the planet,
the more quickly it loses heat.

305
00:18:06,171 --> 00:18:09,571
Still, there is a rule breaker:

306
00:18:09,571 --> 00:18:12,105
a world even smaller than Mars

307
00:18:12,105 --> 00:18:15,571
that is somehow the most
ferociously active body

308
00:18:15,571 --> 00:18:17,138
in the solar system.

309
00:18:22,971 --> 00:18:26,738
Leaving the quiet
volcanoes of Mars behind...

310
00:18:27,738 --> 00:18:30,505
...passing through
the asteroid belt,

311
00:18:30,505 --> 00:18:32,238
the cold rubble left over

312
00:18:32,238 --> 00:18:34,105
from the formation
of the planets...

313
00:18:36,138 --> 00:18:39,538
...we reach the first
of the gas giants.

314
00:18:42,938 --> 00:18:46,305
Twice the mass of all
the other planets combined,

315
00:18:46,305 --> 00:18:50,738
Jupiter is circled
by more than 80 moons.

316
00:18:52,938 --> 00:18:54,671
Some are icy.

317
00:18:55,938 --> 00:18:58,738
Like the frozen expanses
of Ganymede.

318
00:18:59,771 --> 00:19:01,371
And Europa.

319
00:19:03,205 --> 00:19:06,438
But then, there is Io.

320
00:19:12,371 --> 00:19:14,605
About the size of our moon,

321
00:19:14,605 --> 00:19:18,871
Io orbits closer to Jupiter
than any other moon of its size.

322
00:19:22,371 --> 00:19:24,405
Since 2016,

323
00:19:24,405 --> 00:19:27,038
the space probe Juno
has been our eyes

324
00:19:27,038 --> 00:19:28,905
on Jupiter and its moons.

325
00:19:29,905 --> 00:19:32,338
With an elongated orbit,

326
00:19:32,338 --> 00:19:35,438
it has made regular
flybys past Io...

327
00:19:39,371 --> 00:19:42,305
...witnessing violent eruptions,

328
00:19:42,305 --> 00:19:46,005
which shoot out
columns of gas and dust

329
00:19:46,005 --> 00:19:48,838
that reach far out into space...

330
00:19:52,638 --> 00:19:57,805
...and send rivers of lava
pouring across the landscape...

331
00:19:59,138 --> 00:20:03,205
...creating a surface
dotted with lakes of lava.

332
00:20:04,638 --> 00:20:08,105
Io is a volcanic powerhouse,

333
00:20:08,105 --> 00:20:11,071
defying all expectations.

334
00:20:12,271 --> 00:20:15,338
DE KLEER:
Considering how small Io is,

335
00:20:15,338 --> 00:20:18,471
the heat sources
like we have on Earth,

336
00:20:18,471 --> 00:20:21,238
the heat of formation
and the radioactive decay,

337
00:20:21,238 --> 00:20:24,271
those should be, essentially,
completely gone on Io by now.

338
00:20:25,271 --> 00:20:28,605
OLUSEYI:
This little, tiny,
small world of Io,

339
00:20:28,605 --> 00:20:31,405
you'd expect it to be
geologically inactive.

340
00:20:31,405 --> 00:20:32,838
Instead, it's the most

341
00:20:32,838 --> 00:20:34,071
volcanically active body

342
00:20:34,071 --> 00:20:36,371
in our solar system.

343
00:20:36,371 --> 00:20:38,105
That's a surprise.

344
00:20:40,871 --> 00:20:45,338
NARRATOR:
Eruptions continue
day in, day out,

345
00:20:45,338 --> 00:20:48,571
across the entire surface.

346
00:20:50,738 --> 00:20:54,205
A world like no other
in our solar system.

347
00:20:55,438 --> 00:20:57,471
♪ ♪

348
00:20:59,138 --> 00:21:02,438
But similarities can be found

349
00:21:02,438 --> 00:21:05,438
by taking a closer look
beneath the surface

350
00:21:05,438 --> 00:21:08,871
inside volcanoes here on Earth.

351
00:21:16,405 --> 00:21:20,405
Astrophysicist Jen Gupta
is entering a chamber

352
00:21:20,405 --> 00:21:22,871
created by a volcanic eruption

353
00:21:22,871 --> 00:21:25,938
over 4,000 years ago.

354
00:21:28,871 --> 00:21:31,338
GUPTA:
The incredible thing
about this place

355
00:21:31,338 --> 00:21:33,238
is that
as the magma drained away,

356
00:21:33,238 --> 00:21:35,438
it left behind these colors

357
00:21:35,438 --> 00:21:38,371
that we can see here
on the walls,

358
00:21:38,371 --> 00:21:40,038
from elements and minerals

359
00:21:40,038 --> 00:21:42,505
that were dragged up
from the interior of the Earth

360
00:21:42,505 --> 00:21:44,405
during that volcanic eruption.

361
00:21:45,905 --> 00:21:49,071
The one that immediately grabbed
my attention is the yellow.

362
00:21:49,071 --> 00:21:52,171
This is from sulphates
and sulphur,

363
00:21:52,171 --> 00:21:53,438
and these are
the exact same colors

364
00:21:53,438 --> 00:21:56,371
that we see covering
the entire surface of Io.

365
00:22:03,138 --> 00:22:05,138
NARRATOR:
Images of Io are dominated

366
00:22:05,138 --> 00:22:07,405
by its yellow surface,

367
00:22:07,405 --> 00:22:11,705
created by the same sulphates
and sulphur

368
00:22:11,705 --> 00:22:15,238
that line the chamber walls
here in Iceland.

369
00:22:18,938 --> 00:22:21,538
GUPTA:
The scale of this place
is just astonishing,

370
00:22:21,538 --> 00:22:24,905
and to think that
there are chambers like this

371
00:22:24,905 --> 00:22:26,771
under the surface of Io,

372
00:22:26,771 --> 00:22:31,071
filled with molten magma
ready to erupt out.

373
00:22:31,071 --> 00:22:33,771
It's easy to think that Earth,
our home planet,

374
00:22:33,771 --> 00:22:35,871
is completely unique,

375
00:22:35,871 --> 00:22:38,138
but the more we discover
about the solar system,

376
00:22:38,138 --> 00:22:41,005
the more we see
these remarkable similarities,

377
00:22:41,005 --> 00:22:42,705
like having volcanoes on Io.

378
00:22:45,738 --> 00:22:49,171
NARRATOR:
And unlike Mars's
ancient dead volcanoes,

379
00:22:49,171 --> 00:22:55,238
Io's are continually erupting,

380
00:22:55,238 --> 00:22:58,638
creating a thin atmosphere
of volcanic gases.

381
00:23:05,305 --> 00:23:08,505
As Jupiter blocks the sun,

382
00:23:08,505 --> 00:23:11,105
Io passes into its shadow.

383
00:23:14,205 --> 00:23:17,471
Even
with such constant activity,

384
00:23:17,471 --> 00:23:19,571
temperatures plummet,

385
00:23:21,271 --> 00:23:26,471
so low that the thin atmosphere
begins to freeze,

386
00:23:26,471 --> 00:23:28,971
creating an incredible frost.

387
00:23:34,271 --> 00:23:35,938
Made not of water,

388
00:23:35,938 --> 00:23:40,738
but of delicate crystals
of sulphur dioxide.

389
00:23:46,471 --> 00:23:49,271
A few hours later,

390
00:23:49,271 --> 00:23:52,471
they are gone,

391
00:23:52,471 --> 00:23:55,538
evaporating away

392
00:23:55,538 --> 00:23:57,638
as the sun returns.

393
00:23:59,638 --> 00:24:01,605
DOTTIN:
Sulphur is a major component

394
00:24:01,605 --> 00:24:03,538
of volcanic eruptions.

395
00:24:03,538 --> 00:24:05,638
And so it's not surprising

396
00:24:05,638 --> 00:24:09,371
that the surface of Io is

397
00:24:09,371 --> 00:24:10,605
covered with sulphur crystals

398
00:24:10,605 --> 00:24:12,938
because there's so much
volcanic activity

399
00:24:12,938 --> 00:24:14,905
going on there.

400
00:24:20,138 --> 00:24:21,638
NARRATOR:
Io isn't big enough

401
00:24:21,638 --> 00:24:24,005
to have retained heat
from its formation.

402
00:24:25,205 --> 00:24:27,305
So the heat
that drives this much sulphur

403
00:24:27,305 --> 00:24:30,138
to the surface

404
00:24:30,138 --> 00:24:32,671
must be coming
from somewhere else.

405
00:24:34,638 --> 00:24:36,138
DE KLEER:
So, the question is,

406
00:24:36,138 --> 00:24:38,671
why is an object this small

407
00:24:38,671 --> 00:24:40,371
still volcanically active?

408
00:24:40,371 --> 00:24:43,005
Why hasn't it run out
of heat yet?

409
00:24:47,771 --> 00:24:49,305
GUPTA:
The thing about Io

410
00:24:49,305 --> 00:24:53,205
is it doesn't orbit Jupiter
in a circular orbit.

411
00:24:53,205 --> 00:24:55,005
What it does instead is
travel round

412
00:24:55,005 --> 00:24:58,605
in an elliptical orbit
like this.

413
00:24:58,605 --> 00:25:00,471
And it's that elliptical orbit

414
00:25:00,471 --> 00:25:02,305
that's one of the driving forces

415
00:25:02,305 --> 00:25:04,571
behind the level
of volcanic activity

416
00:25:04,571 --> 00:25:07,138
on the moon.

417
00:25:07,138 --> 00:25:09,171
NARRATOR:
Jupiter is the largest planet

418
00:25:09,171 --> 00:25:10,605
in our solar system,

419
00:25:10,605 --> 00:25:14,838
and its gravitational pull
on Io is enormous.

420
00:25:16,438 --> 00:25:19,405
GUPTA:
As Io comes in
towards the planet,

421
00:25:19,405 --> 00:25:21,571
the gravitational pull
of Jupiter is stronger,

422
00:25:21,571 --> 00:25:24,105
causing the very rock on Io

423
00:25:24,105 --> 00:25:26,771
to bulge out
towards its host planet.

424
00:25:26,771 --> 00:25:29,705
Then as Io moves further away,

425
00:25:29,705 --> 00:25:32,005
the bulge shrinks and moves,

426
00:25:32,005 --> 00:25:35,505
causing a tide of rock on Io

427
00:25:35,505 --> 00:25:38,671
that's over 300 feet tall.

428
00:25:38,671 --> 00:25:42,338
That's rock the height
of this chamber

429
00:25:42,338 --> 00:25:46,038
bulging and moving
on that rocky moon.

430
00:25:46,038 --> 00:25:49,138
This is rock
rubbing against rock

431
00:25:49,138 --> 00:25:51,705
in a similar way to
when we rub our hands together,

432
00:25:51,705 --> 00:25:53,038
and they warm up.

433
00:25:53,038 --> 00:25:54,805
It's generating huge amounts

434
00:25:54,805 --> 00:25:57,371
of heat
underneath the surface of Io.

435
00:26:00,105 --> 00:26:02,805
NARRATOR:
A process known as
"tidal heating."

436
00:26:04,238 --> 00:26:08,038
But this bulging movement
generates only some of the heat

437
00:26:08,038 --> 00:26:10,705
that drives
Io's violent volcanoes.

438
00:26:12,805 --> 00:26:15,438
So where is the rest
of the heat coming from?

439
00:26:16,571 --> 00:26:18,871
DOTTIN:
When we think about our moon,

440
00:26:18,871 --> 00:26:22,338
we understand that we only see
one side of the moon,

441
00:26:22,338 --> 00:26:23,671
and this is because

442
00:26:23,671 --> 00:26:25,771
the Earth and the moon
are tidally locked.

443
00:26:25,771 --> 00:26:28,038
NARRATOR:
But as the moon travels

444
00:26:28,038 --> 00:26:30,638
its elliptical path
around Earth,

445
00:26:30,638 --> 00:26:33,205
we actually see it
at slightly different angles.

446
00:26:34,571 --> 00:26:35,805
OLUSEYI:
It's sort of like

447
00:26:35,805 --> 00:26:37,805
if I was to shake my head
and say "no."

448
00:26:39,371 --> 00:26:41,671
Right? You see my face
the entire time,

449
00:26:41,671 --> 00:26:43,705
but because it rocks
back and forth,

450
00:26:43,705 --> 00:26:46,138
you see slightly more of my head

451
00:26:46,138 --> 00:26:49,271
than if I just kept it
pointing right at it.

452
00:26:49,271 --> 00:26:52,071
So, it's like the moon is
looking down on the Earth

453
00:26:52,071 --> 00:26:54,771
and going, "Mm, mm, mm.

454
00:26:54,771 --> 00:26:56,771
Look at those humans."

455
00:26:58,271 --> 00:27:00,005
NARRATOR:
Just like our moon,

456
00:27:00,005 --> 00:27:03,271
Io is tidally locked
to its planet

457
00:27:03,271 --> 00:27:05,138
and has an elliptical orbit.

458
00:27:06,805 --> 00:27:09,638
Which means
that as Io orbits Jupiter,

459
00:27:09,638 --> 00:27:13,371
it appears to rock back
and forth by around one degree.

460
00:27:14,805 --> 00:27:18,038
But there's one big difference
between our moon and Io.

461
00:27:19,538 --> 00:27:22,238
OLUSEYI:
Jupiter is way more massive
than the Earth,

462
00:27:22,238 --> 00:27:24,805
and Io is similar to the moon,

463
00:27:24,805 --> 00:27:27,705
so the tidal effects
are more extreme.

464
00:27:28,871 --> 00:27:30,338
NARRATOR:
Io's tidal bulge

465
00:27:30,338 --> 00:27:33,838
is continuously pulled
towards Jupiter.

466
00:27:33,838 --> 00:27:36,938
So as Io faces the planet
at slightly different angles

467
00:27:36,938 --> 00:27:38,838
throughout its orbit,

468
00:27:38,838 --> 00:27:43,438
Jupiter not only raises the
rock tide 300 feet up and down,

469
00:27:43,438 --> 00:27:48,138
but also drags that tidal bulge
back and forth

470
00:27:48,138 --> 00:27:50,438
40 miles across Io's surface.

471
00:27:51,671 --> 00:27:54,838
Earth's heat was captured
billions of years ago,

472
00:27:54,838 --> 00:27:57,771
locked inside the planet
at the time of formation.

473
00:27:58,738 --> 00:28:02,605
But on Io, its heat
is constantly replenished

474
00:28:02,605 --> 00:28:04,805
by its elliptical orbit.

475
00:28:08,038 --> 00:28:10,371
NARRATOR:
As Io deforms,

476
00:28:10,371 --> 00:28:12,271
the intense friction generated

477
00:28:12,271 --> 00:28:16,105
by these tidal forces
produces enough heat

478
00:28:16,105 --> 00:28:20,805
to drive Io's spectacularly
violent volcanism.

479
00:28:23,038 --> 00:28:25,038
But could all that heat
have driven out

480
00:28:25,038 --> 00:28:28,671
some common planetary
ingredients, like water?

481
00:28:31,705 --> 00:28:33,371
Io doesn't seem
to have any water today,

482
00:28:33,371 --> 00:28:36,571
and we actually don't
entirely know why that is.

483
00:28:36,571 --> 00:28:40,305
Maybe it was never able
to form with any water,

484
00:28:40,305 --> 00:28:42,971
but maybe it just lost
all of its water over time

485
00:28:42,971 --> 00:28:44,771
because of
this tremendous amount of heat

486
00:28:44,771 --> 00:28:47,538
that's produced in it.

487
00:28:50,571 --> 00:28:52,905
FRANCK MARCHIS:
So, there is no water on Io.

488
00:28:52,905 --> 00:28:55,338
Is there life?
We don't know.

489
00:28:55,338 --> 00:28:56,671
If there is life,
it would be a life

490
00:28:56,671 --> 00:28:58,138
which is very different

491
00:28:58,138 --> 00:29:01,138
to the life
we have on our own planet,

492
00:29:01,138 --> 00:29:03,071
and the only way
for us to find it will be

493
00:29:03,071 --> 00:29:05,371
to go there
and to explore directly.

494
00:29:06,338 --> 00:29:08,505
DE KLEER:
Every time
I point a telescope at Io,

495
00:29:08,505 --> 00:29:10,438
I still have that new excitement

496
00:29:10,438 --> 00:29:11,971
because you don't know
what's going to be happening.

497
00:29:11,971 --> 00:29:13,838
You take an image of Io,

498
00:29:13,838 --> 00:29:16,205
and you're saying,
"Which volcanoes are active?"

499
00:29:16,205 --> 00:29:18,605
And you look at it,
and you can just immediately see

500
00:29:18,605 --> 00:29:20,338
from the picture and identify

501
00:29:20,338 --> 00:29:23,705
which volcanoes are going off
at that time.

502
00:29:25,971 --> 00:29:27,838
NARRATOR:
As scientists learn more,

503
00:29:27,838 --> 00:29:29,705
they are finding the effects

504
00:29:29,705 --> 00:29:33,771
of tidal heating
on an even stranger world.

505
00:29:34,738 --> 00:29:37,405
That same source of heat,

506
00:29:37,405 --> 00:29:39,605
caused by an elliptical orbit,

507
00:29:39,605 --> 00:29:43,938
drives volcanic eruptions
that aren't even hot.

508
00:29:46,205 --> 00:29:49,071
Even farther
from Earth than Jupiter,

509
00:29:49,071 --> 00:29:52,771
across a great gulf of space,

510
00:29:52,771 --> 00:29:55,171
lies the next planet.

511
00:30:00,871 --> 00:30:05,371
Saturn's rings loop for hundreds
of thousands of miles.

512
00:30:09,705 --> 00:30:11,305
And just beyond them,

513
00:30:11,305 --> 00:30:14,105
one of its largest moons
changed everything

514
00:30:14,105 --> 00:30:17,071
we thought we knew
about volcanic activity

515
00:30:17,071 --> 00:30:19,305
this far out
in the solar system.

516
00:30:25,271 --> 00:30:29,471
♪ ♪

517
00:30:29,471 --> 00:30:32,538
With a hard, frozen exterior,

518
00:30:32,538 --> 00:30:35,838
Enceladus' surface
averages a chilly

519
00:30:35,838 --> 00:30:39,305
-330 degrees Fahrenheit.

520
00:30:40,971 --> 00:30:45,271
It's one of the coldest places
in the Saturn system.

521
00:30:45,271 --> 00:30:48,205
An ice world,

522
00:30:48,205 --> 00:30:51,971
where we'd expect everything
to be completely still,

523
00:30:51,971 --> 00:30:54,471
frozen and unchanging.

524
00:30:58,971 --> 00:31:01,038
But in 2005,

525
00:31:01,038 --> 00:31:05,138
NASA's Cassini spacecraft
travelled to the South Pole

526
00:31:05,138 --> 00:31:08,038
and discovered
that stillness shattered.

527
00:31:10,338 --> 00:31:13,538
It captured explosive jets

528
00:31:13,538 --> 00:31:16,038
constantly erupting
from the surface.

529
00:31:16,038 --> 00:31:18,071
♪ ♪

530
00:31:20,471 --> 00:31:22,538
NÚÑEZ:
So, when we first saw
those plumes

531
00:31:22,538 --> 00:31:24,171
coming out of Enceladus,

532
00:31:24,171 --> 00:31:27,938
it was just... mind-boggling

533
00:31:27,938 --> 00:31:30,505
that to see this tiny world

534
00:31:30,505 --> 00:31:32,671
spewing material out,

535
00:31:32,671 --> 00:31:35,605
indicating
that it was geologically active.

536
00:31:38,205 --> 00:31:40,105
Discovering the jets
at Enceladus's south pole

537
00:31:40,105 --> 00:31:42,471
completely changed the way
that we see icy worlds.

538
00:31:42,471 --> 00:31:45,705
It changed the way that we see
small, icy worlds in particular.

539
00:31:49,038 --> 00:31:53,105
NARRATOR:
Giant plumes far bigger
than the moon they erupt from

540
00:31:53,105 --> 00:31:55,071
are an incredible sight.

541
00:31:56,971 --> 00:32:01,171
But how is it possible
to have such powerful eruptions

542
00:32:01,171 --> 00:32:03,238
on a frozen moon?

543
00:32:09,305 --> 00:32:11,905
Our usual experience
of volcanic eruptions

544
00:32:11,905 --> 00:32:13,638
is of molten rock

545
00:32:13,638 --> 00:32:16,038
bursting onto the surface.

546
00:32:19,238 --> 00:32:22,971
But eruptions on Enceladus
are different,

547
00:32:22,971 --> 00:32:25,071
more like what's happening here.

548
00:32:27,205 --> 00:32:29,638
At a geothermal power plant
in Iceland.

549
00:32:31,371 --> 00:32:34,005
A mile below the surface

550
00:32:34,005 --> 00:32:37,305
lies a reservoir
of superheated water.

551
00:32:38,471 --> 00:32:41,771
Drilling down into it
allows steam and water

552
00:32:41,771 --> 00:32:45,938
to erupt out
and generate electricity.

553
00:32:48,071 --> 00:32:50,271
HOWETT:
To be here is amazing!

554
00:32:50,271 --> 00:32:53,671
I spent most of my entire
adult life studying Enceladus,

555
00:32:53,671 --> 00:32:56,305
but I've never heard it,
I've never seen it,

556
00:32:56,305 --> 00:32:58,605
I've never felt it,
and this is one-tenth

557
00:32:58,605 --> 00:33:01,971
of what one of the jets
on Enceladus would be like.

558
00:33:01,971 --> 00:33:04,371
It's astounding.

559
00:33:06,805 --> 00:33:09,838
NARRATOR:
Over 660 pounds of water

560
00:33:09,838 --> 00:33:14,338
erupt from the surface
of Enceladus every second,

561
00:33:14,338 --> 00:33:16,271
creating visible eruptions

562
00:33:16,271 --> 00:33:19,638
that can thrust up to
6,000 miles into space.

563
00:33:22,238 --> 00:33:25,305
It's called cryovolcanism.

564
00:33:25,305 --> 00:33:27,938
"Cryo" from the Greek for cold.

565
00:33:29,905 --> 00:33:32,971
Cryovolcanism
is absolutely volcanism.

566
00:33:32,971 --> 00:33:35,205
When we study the planets,
we learned that,

567
00:33:35,205 --> 00:33:38,205
even though they have different
chemistry or slight differences,

568
00:33:38,205 --> 00:33:41,538
that these processes are common
throughout the planets,

569
00:33:41,538 --> 00:33:43,505
and volcanism is one of them.

570
00:33:46,705 --> 00:33:47,805
MARCHIS:
What is surprising

571
00:33:47,805 --> 00:33:50,171
is not only the presence
of the jets,

572
00:33:50,171 --> 00:33:52,838
but their size,
the fact that this is

573
00:33:52,838 --> 00:33:54,871
an extreme cryovolcanism

574
00:33:54,871 --> 00:33:57,305
coming from such a small body.

575
00:34:00,238 --> 00:34:03,138
NARRATOR:
But where does such
an enormous amount of water

576
00:34:03,138 --> 00:34:05,738
come from on a frigid ice moon?

577
00:34:09,105 --> 00:34:11,871
There is a hint.

578
00:34:11,871 --> 00:34:14,771
As Enceladus orbits Saturn,

579
00:34:14,771 --> 00:34:19,238
it wobbles by about 0.12 degrees
on its axis.

580
00:34:22,871 --> 00:34:25,538
A tiny but significant
movement...

581
00:34:26,871 --> 00:34:30,071
...that tells us something
about the moon's interior.

582
00:34:31,071 --> 00:34:32,538
HOWETT:
A simple way to think about

583
00:34:32,538 --> 00:34:34,505
what's happening
inside Enceladus

584
00:34:34,505 --> 00:34:38,138
is to consider what happens
when we rotate two eggs,

585
00:34:38,138 --> 00:34:41,171
one of which is hard-boiled
and the other one isn't.

586
00:34:41,171 --> 00:34:44,371
So, we'll start with this one.

587
00:34:44,371 --> 00:34:45,738
If we spin the egg...

588
00:34:49,371 --> 00:34:51,705
(laughs) Just with eggs,

589
00:34:51,705 --> 00:34:53,138
doesn't seem like
the most obvious solution.

590
00:34:53,138 --> 00:34:55,205
You can see that it...

591
00:34:55,205 --> 00:34:57,238
As it rotates, it's got
a bit of a wobble to it,

592
00:34:57,238 --> 00:34:59,605
and if we rotate it a bit faster
and then stop it,

593
00:34:59,605 --> 00:35:01,605
it'll continue to rotate.

594
00:35:02,905 --> 00:35:04,305
Whereas this one,

595
00:35:04,305 --> 00:35:05,605
we do the same thing.

596
00:35:05,605 --> 00:35:08,305
It rotates more smoothly,

597
00:35:08,305 --> 00:35:10,371
and if we rotate it and stop it,

598
00:35:10,371 --> 00:35:12,605
you can see it stops.

599
00:35:13,938 --> 00:35:15,805
NARRATOR:
The reason the first one wobbles

600
00:35:15,805 --> 00:35:18,371
is because it is raw.

601
00:35:18,371 --> 00:35:20,571
Whereas this one...

602
00:35:23,838 --> 00:35:25,738
...is hard-boiled.

603
00:35:28,038 --> 00:35:30,238
The raw one, of course,
has a liquid in the middle,

604
00:35:30,238 --> 00:35:32,338
and so, even after
you stop the shell,

605
00:35:32,338 --> 00:35:34,238
the liquid continues to rotate,

606
00:35:34,238 --> 00:35:36,238
and that causes
the shell to rotate.

607
00:35:36,238 --> 00:35:38,505
It also caused
that wobbly rotation

608
00:35:38,505 --> 00:35:40,038
that we see all the way along.

609
00:35:40,038 --> 00:35:42,805
Whereas the hard-boiled one
is solid all the way through.

610
00:35:42,805 --> 00:35:44,905
When you stop the shell,
you stop all of it.

611
00:35:44,905 --> 00:35:47,738
It also causes it
to rotate very nicely.

612
00:35:47,738 --> 00:35:49,505
But it's the liquid one,
the raw one,

613
00:35:49,505 --> 00:35:50,705
that's like Enceladus.

614
00:35:52,905 --> 00:35:56,471
NARRATOR:
Enceladus is unlikely
to crack like a raw egg.

615
00:35:57,438 --> 00:35:59,705
But it does wobble like one.

616
00:36:02,671 --> 00:36:07,005
And that tells us that
there is an outer shell of ice,

617
00:36:07,005 --> 00:36:10,971
sitting on top
of a global ocean of water.

618
00:36:14,505 --> 00:36:18,171
But how does that water
manage to erupt

619
00:36:18,171 --> 00:36:22,371
through a shell of around
three miles of solid ice?

620
00:36:23,838 --> 00:36:26,205
QUICK:
When the liquid ocean
is heated from below

621
00:36:26,205 --> 00:36:29,171
by energy from tidal heating,
it expands,

622
00:36:29,171 --> 00:36:31,605
so the liquid wants
to take up more space.

623
00:36:31,605 --> 00:36:33,871
As it seeks
to take up more space,

624
00:36:33,871 --> 00:36:36,171
it pushes up against
the bottom of the ice shell.

625
00:36:37,638 --> 00:36:41,105
NARRATOR:
Once there, another force
comes into action.

626
00:36:42,405 --> 00:36:44,638
Once that water goes
through a crack

627
00:36:44,638 --> 00:36:47,538
and then is exposed to the
vacuum of space,

628
00:36:47,538 --> 00:36:49,038
it's like a suction.

629
00:36:49,038 --> 00:36:50,971
That's what vacuum does.

630
00:36:50,971 --> 00:36:52,871
BYRNE:
The reason water
behaves this way

631
00:36:52,871 --> 00:36:54,871
when it's exposed
to zero pressure

632
00:36:54,871 --> 00:36:56,738
is because
there's nothing acting

633
00:36:56,738 --> 00:36:58,071
to keep
the water together.

634
00:36:58,071 --> 00:37:00,405
So, the water will try
its best to expand

635
00:37:00,405 --> 00:37:02,305
as much as it possibly can.

636
00:37:04,271 --> 00:37:05,671
One force pushes the water up,

637
00:37:05,671 --> 00:37:08,238
and the other force
pulls it out onto the surface,

638
00:37:08,238 --> 00:37:10,471
and that's why we have
these magnificent jets.

639
00:37:12,238 --> 00:37:14,338
NARRATOR:
And they carry with them
the secrets

640
00:37:14,338 --> 00:37:17,605
of what lies beneath the ice.

641
00:37:19,538 --> 00:37:22,638
These plumes contain
traces of silica

642
00:37:22,638 --> 00:37:24,705
and molecular hydrogen

643
00:37:24,705 --> 00:37:26,905
that could've come
from the ocean water

644
00:37:26,905 --> 00:37:29,638
interacting
with hot volcanic rocks.

645
00:37:32,005 --> 00:37:35,705
Suggesting that, in the depths
of Enceladus's ocean,

646
00:37:35,705 --> 00:37:38,771
there may be hydrothermal vents,

647
00:37:38,771 --> 00:37:41,871
towering structures
created by water flowing

648
00:37:41,871 --> 00:37:44,738
into the volcanic rocks
on the seabed.

649
00:37:46,905 --> 00:37:48,005
I think the chances
are pretty high

650
00:37:48,005 --> 00:37:49,138
that there are
hydrothermal vents

651
00:37:49,138 --> 00:37:51,071
at the bottom
of Enceladus' ocean.

652
00:37:51,071 --> 00:37:52,571
Just like Earth's ocean,

653
00:37:52,571 --> 00:37:55,271
Enceladus's ocean sits right
on top of its rocky mantle.

654
00:37:56,271 --> 00:37:59,305
NARRATOR:
And with probable
hydrothermal vents,

655
00:37:59,305 --> 00:38:02,671
an exciting possibility
for life.

656
00:38:02,671 --> 00:38:07,005
NÚÑEZ:
We think that life
could've originated on Earth

657
00:38:07,005 --> 00:38:08,805
in hydrothermal vents.

658
00:38:08,805 --> 00:38:10,705
And these hydrothermal vents

659
00:38:10,705 --> 00:38:12,171
have those ingredients

660
00:38:12,171 --> 00:38:14,671
that are essential for life.

661
00:38:17,371 --> 00:38:20,238
NARRATOR:
And it isn't just
the possibility of heat

662
00:38:20,238 --> 00:38:23,938
that makes Enceladus
a compelling incubator for life.

663
00:38:25,471 --> 00:38:26,871
HOFGARTNER:
There are three key ingredients

664
00:38:26,871 --> 00:38:28,571
to a habitable environment:

665
00:38:28,571 --> 00:38:31,438
liquid water,
chemical nutrients,

666
00:38:31,438 --> 00:38:33,238
and an energy source to use,

667
00:38:33,238 --> 00:38:37,271
and now we know that Enceladus
has all three within its ocean.

668
00:38:40,338 --> 00:38:43,471
QUICK:
A 2023 study showed
that Enceladus's jets

669
00:38:43,471 --> 00:38:45,138
have phosphates in it,

670
00:38:45,138 --> 00:38:48,405
anywhere from 100 to 1,000 times
the amount of phosphates

671
00:38:48,405 --> 00:38:49,871
that we find in Earth's oceans.

672
00:38:49,871 --> 00:38:54,105
Phosphates, we know,
are a key component of DNA,

673
00:38:54,105 --> 00:38:55,671
which is the
building block of life.

674
00:38:58,738 --> 00:39:01,171
NÚÑEZ:
Does that mean
that we found life?

675
00:39:01,171 --> 00:39:02,605
Well, we don't know.

676
00:39:02,605 --> 00:39:04,005
Just because
we found phosphates,

677
00:39:04,005 --> 00:39:07,038
it's-it's a potential
ingredient,

678
00:39:07,038 --> 00:39:08,338
but it's not a slam dunk,

679
00:39:08,338 --> 00:39:11,638
and so, we need to go back
and really explore

680
00:39:11,638 --> 00:39:13,438
in more detail to see

681
00:39:13,438 --> 00:39:16,005
what is the origin
of this phosphate.

682
00:39:18,871 --> 00:39:22,305
NARRATOR:
Any mission to Enceladus
is a ways off.

683
00:39:23,805 --> 00:39:27,338
But there is another world
much closer to home

684
00:39:27,338 --> 00:39:30,738
that has more volcanoes
strewn across its surface

685
00:39:30,738 --> 00:39:32,838
than any other planet.

686
00:39:42,171 --> 00:39:44,205
To find it, we have to return

687
00:39:44,205 --> 00:39:47,538
all the way back
into the inner solar system.

688
00:39:49,571 --> 00:39:51,571
Past Mars's ancient peaks...

689
00:39:53,705 --> 00:39:55,371
...and beyond Earth.

690
00:39:56,405 --> 00:39:59,705
...to a mysterious,
cloud-covered planet.

691
00:40:10,138 --> 00:40:13,305
Venus's dense atmosphere
of carbon dioxide

692
00:40:13,305 --> 00:40:16,671
and clouds of sulfuric acid

693
00:40:16,671 --> 00:40:18,805
obscure the surface.

694
00:40:22,905 --> 00:40:26,205
For decades, orbiting probes
have used radar

695
00:40:26,205 --> 00:40:28,505
to peer through the clouds.

696
00:40:31,505 --> 00:40:33,871
Revealing a landscape dominated

697
00:40:33,871 --> 00:40:36,771
by more than 85,000 volcanoes.

698
00:40:39,738 --> 00:40:41,871
But it was hard to see
in the images

699
00:40:41,871 --> 00:40:44,071
if any were recently active,

700
00:40:44,071 --> 00:40:46,771
or if, like Mars,

701
00:40:46,771 --> 00:40:49,005
they were relics of the past.

702
00:40:50,571 --> 00:40:54,438
So why does Venus
have so many volcanoes?

703
00:40:56,705 --> 00:40:59,138
And are they still
erupting today?

704
00:41:02,771 --> 00:41:06,571
To find out, scientists
are studying Iceland,

705
00:41:06,571 --> 00:41:10,105
one of the most volcanically
active places on Earth.

706
00:41:19,438 --> 00:41:24,005
Here they are investigating
recent lava flow activity

707
00:41:24,005 --> 00:41:26,838
to help prepare
for future missions to Venus.

708
00:41:29,971 --> 00:41:32,138
SUE SMREKAR:
I have remained
fascinated by Venus

709
00:41:32,138 --> 00:41:35,471
because it tells us so much
about the Earth.

710
00:41:35,471 --> 00:41:36,471
They really are twin planets

711
00:41:36,471 --> 00:41:39,538
evolving down different paths.

712
00:41:42,305 --> 00:41:45,105
NARRATOR:
Sue Smrekar is leading
the Veritas mission

713
00:41:45,105 --> 00:41:48,471
preparing to launch to Venus
in the next decade.

714
00:41:50,105 --> 00:41:52,005
She uses radar data,

715
00:41:52,005 --> 00:41:54,038
which creates
black-and-white images

716
00:41:54,038 --> 00:41:56,538
that reveal the texture
of the surface.

717
00:41:59,505 --> 00:42:02,771
♪ ♪

718
00:42:04,438 --> 00:42:06,838
SMREKAR:
I try to see things
with my radar eyes,

719
00:42:06,838 --> 00:42:08,438
just imagining
what they look like.

720
00:42:09,838 --> 00:42:13,205
When it's a nice smooth surface,
the radar wave comes down,

721
00:42:13,205 --> 00:42:14,638
and it looks dark.

722
00:42:14,638 --> 00:42:17,471
But these areas
that are super rough,

723
00:42:17,471 --> 00:42:19,271
you'll get
a lot more reflection, so,

724
00:42:19,271 --> 00:42:23,138
in radar, these areas
will be much brighter.

725
00:42:26,405 --> 00:42:28,705
NARRATOR:
Whether new lava flows
like we see on Earth

726
00:42:28,705 --> 00:42:33,738
exist on Venus
was a much debated subject,

727
00:42:33,738 --> 00:42:35,971
as scientists
had no direct evidence

728
00:42:35,971 --> 00:42:38,271
of recent volcanic activity
on Venus.

729
00:42:40,738 --> 00:42:42,771
Until now.

730
00:42:43,738 --> 00:42:45,005
ROBERT HERRICK:
It's really

731
00:42:45,005 --> 00:42:47,605
only been
in the last decade or so

732
00:42:47,605 --> 00:42:50,005
that technology
has made it possible

733
00:42:50,005 --> 00:42:51,638
to be able to zoom in and out

734
00:42:51,638 --> 00:42:54,805
and flip back and forth
between data.

735
00:42:56,471 --> 00:42:58,771
 
NARRATOR:
Using today's faster computers,

736
00:42:58,771 --> 00:43:02,638
Robert Herrick and his team
reanalyzed images taken

737
00:43:02,638 --> 00:43:05,171
by the Magellan orbiter...

738
00:43:05,171 --> 00:43:07,971
over 30 years ago,

739
00:43:07,971 --> 00:43:10,271
and spotted a volcanic crater

740
00:43:10,271 --> 00:43:13,138
that had doubled in size
over eight months.

741
00:43:14,105 --> 00:43:16,705
Proving that a volcano,

742
00:43:16,705 --> 00:43:20,071
about the size of Mount Everest,

743
00:43:20,071 --> 00:43:22,671
was erupting
from its northern flank.

744
00:43:24,005 --> 00:43:26,171
HERRICK:
When an investigation
actually works out,

745
00:43:26,171 --> 00:43:28,505
and you learn something
important, and you're like,

746
00:43:28,505 --> 00:43:29,938
"Oh, this is... this is cool."

747
00:43:32,005 --> 00:43:34,405
So, yes,
it's a thrill to, you know,

748
00:43:34,405 --> 00:43:37,271
"Wow, I've-I've made my mark
on the field."

749
00:43:37,271 --> 00:43:39,638
I was so excited
when we saw those images

750
00:43:39,638 --> 00:43:41,505
because what that tells us
is that everything

751
00:43:41,505 --> 00:43:43,905
we've been thinking
about Venus is right,

752
00:43:43,905 --> 00:43:46,371
that this world probably
is volcanically active,

753
00:43:46,371 --> 00:43:49,205
and that just makes us hungry
for more.

754
00:43:51,105 --> 00:43:54,571
NARRATOR:
But evidence of one
probable eruption can't reveal

755
00:43:54,571 --> 00:43:57,738
if the rest of Venus's volcanoes
are still active.

756
00:43:59,005 --> 00:44:02,005
And another mystery remains.

757
00:44:03,038 --> 00:44:05,205
Venus could have been
Earth's twin.

758
00:44:06,171 --> 00:44:09,705
It is roughly the same size
and built of the same stuff.

759
00:44:12,805 --> 00:44:15,671
So why are the two planets
so different today?

760
00:44:18,438 --> 00:44:22,338
Understanding where volcanoes
are found may solve this puzzle

761
00:44:22,338 --> 00:44:26,238
and explain
why Venus is now a planet

762
00:44:26,238 --> 00:44:29,105
with such extreme conditions.

763
00:44:33,805 --> 00:44:35,438
SMREKAR:
So, this map shows
the distribution

764
00:44:35,438 --> 00:44:37,071
of volcanoes on the Earth.

765
00:44:37,071 --> 00:44:39,071
And you can see
there's a big line of them

766
00:44:39,071 --> 00:44:41,438
that goes down the coast
of North America

767
00:44:41,438 --> 00:44:43,938
on down to South America,

768
00:44:43,938 --> 00:44:46,938
and their location
is really controlled

769
00:44:46,938 --> 00:44:50,671
to a large degree by the
location of plate boundaries.

770
00:44:51,738 --> 00:44:54,038
NARRATOR:
Most volcanoes
on Earth are found

771
00:44:54,038 --> 00:44:57,738
where two plates meet,
or are pulling apart,

772
00:44:57,738 --> 00:45:00,571
creating lines of volcanoes
along their edges.

773
00:45:01,671 --> 00:45:05,138
But on Venus,
the pattern is very different.

774
00:45:05,138 --> 00:45:08,105
SMREKAR:
So, this is a map
of the volcanism on Venus,

775
00:45:08,105 --> 00:45:10,138
the volcanoes, and you can see

776
00:45:10,138 --> 00:45:11,838
that they are
all over the place.

777
00:45:11,838 --> 00:45:13,071
They don't follow any nice,

778
00:45:13,071 --> 00:45:15,638
uh, tight line of volcanism

779
00:45:15,638 --> 00:45:17,505
the way we saw for Earth.

780
00:45:17,505 --> 00:45:19,105
And, you know, the difference is

781
00:45:19,105 --> 00:45:21,838
that, uh, on Venus,
we don't have plate tectonics.

782
00:45:21,838 --> 00:45:24,271
Venus has
some entirely different system.

783
00:45:28,038 --> 00:45:30,505
NARRATOR:
Not only are
there numerous volcanoes

784
00:45:30,505 --> 00:45:33,105
scattered
across Venus' landscape,

785
00:45:33,105 --> 00:45:35,671
they take on odd forms.

786
00:45:38,138 --> 00:45:41,771
From lines
of flattened volcanic domes

787
00:45:41,771 --> 00:45:44,138
that look like chains
of pancakes...

788
00:45:46,638 --> 00:45:48,405
...to strange volcanoes

789
00:45:48,405 --> 00:45:51,838
whose rutted sides make them
look almost like insects,

790
00:45:51,838 --> 00:45:54,805
clamped to the surface.

791
00:45:55,805 --> 00:45:58,871
Venus is a volcanic zoo,

792
00:45:58,871 --> 00:46:01,671
with a variety of volcanoes,

793
00:46:01,671 --> 00:46:04,871
including some that are unique
in the solar system.

794
00:46:07,271 --> 00:46:08,905
Venus doesn't have
plate tectonics,

795
00:46:08,905 --> 00:46:12,705
but its crust has
uneven thickness,

796
00:46:12,705 --> 00:46:15,638
and so, magma from within

797
00:46:15,638 --> 00:46:18,171
can climb and poke into
the crust and then cool.

798
00:46:19,871 --> 00:46:23,005
NARRATOR:
The inner heat drives
vast lava flows

799
00:46:23,005 --> 00:46:26,938
that can run
for thousands of miles,

800
00:46:26,938 --> 00:46:29,205
and creates far more blemishes
and bubbles

801
00:46:29,205 --> 00:46:31,738
on the surface
than here on Earth.

802
00:46:34,338 --> 00:46:36,638
But the lack of plate tectonics

803
00:46:36,638 --> 00:46:40,005
points to a far more
profound difference

804
00:46:40,005 --> 00:46:42,238
between Earth and Venus.

805
00:46:44,671 --> 00:46:46,005
DOTTIN:
So on Earth,

806
00:46:46,005 --> 00:46:47,038
there have
been times where

807
00:46:47,038 --> 00:46:50,305
there were
volcanic eruptions

808
00:46:50,305 --> 00:46:52,705
that were so large
and so constant

809
00:46:52,705 --> 00:46:55,405
 
that it was filling
the atmosphere

810
00:46:55,405 --> 00:46:58,771
with tons of toxic gases
and greenhouse gases.

811
00:47:00,471 --> 00:47:02,771
NARRATOR:
Venus's greenhouse gases
trapped heat,

812
00:47:02,771 --> 00:47:05,438
increasing the temperature,

813
00:47:05,438 --> 00:47:08,438
but thanks to plate tectonics,

814
00:47:08,438 --> 00:47:11,071
Earth had a way
to balance this effect.

815
00:47:12,071 --> 00:47:13,505
MORRIS:
On Earth,

816
00:47:13,505 --> 00:47:14,538
carbon dioxide is actually

817
00:47:14,538 --> 00:47:16,271
pulled out of the atmosphere

818
00:47:16,271 --> 00:47:18,038
when it rains,

819
00:47:18,038 --> 00:47:20,838
and those molecules interact
with the rocks

820
00:47:20,838 --> 00:47:23,871
and the carbon dioxide gets
deposited in the rocks,

821
00:47:23,871 --> 00:47:26,805
and as the plate tectonics
cycle occurs,

822
00:47:26,805 --> 00:47:30,838
that material gets then
pulled into the subsurface

823
00:47:30,838 --> 00:47:32,971
and removed from the atmosphere.

824
00:47:32,971 --> 00:47:34,305
BYRNE:
When we have

825
00:47:34,305 --> 00:47:36,305
these huge volcanic eruptions

826
00:47:36,305 --> 00:47:38,138
injecting all this CO2

827
00:47:38,138 --> 00:47:39,438
into the atmosphere,

828
00:47:39,438 --> 00:47:43,038
we see substantial
and severe climate change,

829
00:47:43,038 --> 00:47:44,338
at least for a while,

830
00:47:44,338 --> 00:47:46,305
until plate tectonics is able

831
00:47:46,305 --> 00:47:50,105
to regulate things
and get them back under control.

832
00:47:50,105 --> 00:47:51,271
DOTTIN:
So, plate tectonics

833
00:47:51,271 --> 00:47:54,371
is probably one
of the main reasons

834
00:47:54,371 --> 00:47:57,571
why we've been able
to maintain the climate

835
00:47:57,571 --> 00:47:59,305
that we have on our planet.

836
00:48:01,738 --> 00:48:04,338
NARRATOR:
As Venus's volcanoes erupted,

837
00:48:04,338 --> 00:48:06,405
it seems there was no mechanism

838
00:48:06,405 --> 00:48:08,905
to remove those gases
from the atmosphere

839
00:48:08,905 --> 00:48:10,738
back to the interior.

840
00:48:14,171 --> 00:48:18,605
So the planet got hotter
and hotter,

841
00:48:18,605 --> 00:48:22,671
turning it into the hellish
landscape we see today.

842
00:48:24,238 --> 00:48:27,671
Venus shows the importance
of plate tectonics

843
00:48:27,671 --> 00:48:30,871
in helping to control
not just volcanoes,

844
00:48:30,871 --> 00:48:33,005
but the climate, too.

845
00:48:34,571 --> 00:48:36,838
MORRIS:
So, the lesson
that we can learn from Venus

846
00:48:36,838 --> 00:48:38,771
is that on Earth,

847
00:48:38,771 --> 00:48:41,838
the planet is actually able
to stabilize itself

848
00:48:41,838 --> 00:48:43,805
through the process
of plate tectonics,

849
00:48:43,805 --> 00:48:46,105
and we see on Venus what happens

850
00:48:46,105 --> 00:48:47,605
when the planet's not able

851
00:48:47,605 --> 00:48:49,805
to maintain that stability
in the atmosphere.

852
00:48:53,571 --> 00:48:55,305
NARRATOR:
But human activity emits

853
00:48:55,305 --> 00:48:58,238
at least 60 times
more carbon dioxide

854
00:48:58,238 --> 00:49:01,505
than all the volcanoes
on Earth each year,

855
00:49:01,505 --> 00:49:05,805
and plate tectonics
is a slow process.

856
00:49:07,138 --> 00:49:09,805
OLUSEYI:
What we see in Venus's
atmosphere is a cautionary tale

857
00:49:09,805 --> 00:49:13,471
for the situation that Earth
is in at this very moment.

858
00:49:13,471 --> 00:49:15,738
We have a greenhouse effect
taking place

859
00:49:15,738 --> 00:49:17,771
that's warming
our planet.

860
00:49:18,805 --> 00:49:21,771
Venus is a runaway
greenhouse effect

861
00:49:21,771 --> 00:49:23,571
just gone rampant,

862
00:49:23,571 --> 00:49:26,671
and the whole planet is now
a hotbox of it.

863
00:49:31,538 --> 00:49:32,905
NARRATOR:
Scientists don't think

864
00:49:32,905 --> 00:49:35,471
human emissions alone
can send us

865
00:49:35,471 --> 00:49:37,505
to those extremes.

866
00:49:38,971 --> 00:49:41,205
But with Venus,
we have another planet

867
00:49:41,205 --> 00:49:43,905
that's identical in many ways.

868
00:49:43,905 --> 00:49:48,171
And by understanding
why it's so different today,

869
00:49:48,171 --> 00:49:52,838
we can appreciate the unique
habitability of our own planet.

870
00:49:52,838 --> 00:49:55,871
(explosive pop)

871
00:49:55,871 --> 00:49:59,138
SMREKAR:
Venus is kind of a...
like a teenager.

872
00:49:59,138 --> 00:50:02,538
We go back in time to the
early part of Earth's geology

873
00:50:02,538 --> 00:50:04,038
when we study Venus.

874
00:50:04,038 --> 00:50:06,771
So, it's a... it's a really
a fascinating, you know,

875
00:50:06,771 --> 00:50:09,471
look at our...
the evolution of our own planet.

876
00:50:11,271 --> 00:50:14,438
NARRATOR:
Future missions
like the Veritas orbiter

877
00:50:14,438 --> 00:50:16,871
will help explain
the different processes

878
00:50:16,871 --> 00:50:19,271
behind volcanism on Venus.

879
00:50:20,671 --> 00:50:22,038
SMREKAR:
With Veritas, we have just

880
00:50:22,038 --> 00:50:25,471
all kinds of ways
to look for new volcanism.

881
00:50:26,871 --> 00:50:30,338
We can actually see the surface
deforming at the scale of,

882
00:50:30,338 --> 00:50:31,938
you know, an inch or so.

883
00:50:31,938 --> 00:50:35,105
And I think we're just going
to see vastly more flows

884
00:50:35,105 --> 00:50:36,971
that are young and even,

885
00:50:36,971 --> 00:50:38,505
I predict,
happening during our mission.

886
00:50:40,505 --> 00:50:43,005
NARRATOR:
With new insights into Venus,

887
00:50:43,005 --> 00:50:44,805
we can better understand
the role

888
00:50:44,805 --> 00:50:49,438
plate tectonics plays in
balancing our own environment,

889
00:50:49,438 --> 00:50:53,105
creating the conditions
for life to thrive.

890
00:50:57,505 --> 00:51:00,105
One of the revelations
in our exploration

891
00:51:00,105 --> 00:51:03,438
of the solar system is
what we are finding

892
00:51:03,438 --> 00:51:06,005
isn't a collection
of inactive worlds.

893
00:51:08,271 --> 00:51:09,738
HOFGARTNER:
There is a great diversity

894
00:51:09,738 --> 00:51:12,371
of geological activity in
the solar system,

895
00:51:12,371 --> 00:51:14,071
and sometimes nature

896
00:51:14,071 --> 00:51:17,205
makes it occur
in surprising places.

897
00:51:19,105 --> 00:51:23,538
NARRATOR:
From the tiny,
explosive moon of Io...

898
00:51:23,538 --> 00:51:27,371
to the stunning cryovolcanoes
on Enceladus,

899
00:51:27,371 --> 00:51:32,071
they are telling us
so much about Earth.

900
00:51:32,071 --> 00:51:34,238
SOUSA-SILVA:
When we look
at other planets and moons,

901
00:51:34,238 --> 00:51:37,538
we see snippets
of Earth's past and future.

902
00:51:37,538 --> 00:51:41,171
We were once covered
in volcanoes like Io is now,

903
00:51:41,171 --> 00:51:43,271
and in Venus,
we see what happens

904
00:51:43,271 --> 00:51:46,571
when greenhouse gases
get out of control.

905
00:51:48,238 --> 00:51:50,038
NARRATOR:
But they also tell us

906
00:51:50,038 --> 00:51:53,371
just how remarkable Earth is,

907
00:51:53,371 --> 00:51:56,105
for one very special reason.

908
00:51:59,005 --> 00:52:01,105
Amongst all these geologically
active worlds,

909
00:52:01,105 --> 00:52:04,071
it's still pretty amazing
that the only place

910
00:52:04,071 --> 00:52:07,505
where we saw these
active geology become biology

911
00:52:07,505 --> 00:52:08,971
is here on Earth.

912
00:52:08,971 --> 00:52:11,438
♪ ♪

913
00:52:35,105 --> 00:52:37,971
♪ ♪

914
00:52:38,905 --> 00:52:46,438
♪ ♪

915
00:52:50,271 --> 00:52:57,805
♪ ♪

916
00:53:01,705 --> 00:53:09,238
♪ ♪

917
00:53:10,871 --> 00:53:18,405
♪ ♪

918
00:53:20,038 --> 00:53:27,571
♪ ♪