Original subtitles

In 1979, a robotic spacecraft

flew by the Planet Jupiter.

Completely unexpectedly, it found a mysterious object

the size of our Moon.

The craft had observed something almost unbelievable.

We live on a remarkable planet.

The rock itself is alive.

The Earth spits out hot lava, creating new land.

It is a sight we can only watch in awe.

Well, I find it absolutely overwhelming to look

inside a volcano like this and see the hot lava oozing out.

You can see that the Earth is active.

It's like the lifeblood of the planet.

For a geologist, like Jim Head,

the Earth is an inspiration to look into other worlds.

How does all this play out on the other planets?

What does it look like there?

Would there be hot lava like this, volcanoes?

Would we see things like ocean basins?

We have absolutely no clue.

The history of this planet is written in its rocks.

Over hundreds of millions of years,

mountain ranges have risen up,

entire continents have drifted apart.

Is this how other worlds would be?

Earth's satellite, the Moon, could hardly be more different.

Nothing has happened on this dusty world

for billions of years.

Its surface shows only the scars

of countless impacts by asteroids.

The surfaces of the other planets

must also reveal clues about their past.

But they are so far away,

they appear just as dots of light in the sky.

Astronomers gazed at those dots;

but only on one of them could they make out anything

that looked remotely like the landforms of the Earth.

It was the Red Planet of Mars.

Over a century ago, an Italian astronomer,

Giovanni Schiaparelli, began to chart

the dark and light regions of Mars.

His maps were the best we had until space probes came along.

In 1964, NASA launched Mariner 4.

Its mission was to fly past Mars

and try to send back closeup pictures.

The mission was a technical success.

But the fuzzy images showed nothing particularly

interesting, just craters, like those on the Moon.

But astronomers were convinced

that the probe had looked in the wrong place.

Brad Smith had spent years gazing at the Red Planet.

He thought he knew where the next probe should look.

For the next mission, NASA asked him for help.

I have been observing Mars for quite some time

with ground-based telescopes, and we had noticed

that there were certain regions

that were very changeable,

they change with the seasons,

they seem to have colors to them.

And we thought that those would be particularly interesting,

so I set up the targeting so that Mariner 6 and 7

would look at these particular areas during the approach.

As Mariner 6 and 7 raced towards Mars,

they saw what appeared to be mountains,

dark plains, deep canyons.

But when the closeups came back,

Brad and NASA were once again disappointed.

Unfortunately the surface was

very heavily-cratered.

There were dark and light areas, to be sure,

but it was still a lot like looking at the Moon.

Convinced that there had to be more

than just craters on Mars, NASA went back again.

This time, they planned to give the probe longer to search.

Mariner 9 was not a quick flyby;

it was designed to go into orbit around Mars

and photograph every square foot of the Planet.

But as the probe closed in, disaster.

A large dust storm began to stir.

I was watching the Planet, hoping that it wouldn't

be a bad one, but within just a matter of days

a brilliant brilliant yellow cloud developed

and we knew it was a bad dust storm,

and it spread out over the entire Planet,

covering up everything.

But Mariner sat out the storm,

and then, miraculously, saw something poking up

through the dust.

We saw these four dark spots

and we weren't really quite sure what they were.

And one of our team members had pointed out

that there were things that looked like

the tops of volcanoes; and he suggested that in fact

these were volcanoes that were so high

that they were actually poking up through the dust.

As the dust began to recede,

the four spots showed themselves.

They were volcanoes,

giant ones.

The biggest of them was christened Olympus Mons.

It was 15 miles high,

three times the size of Everest.

Mars was not just another Moon;

it was a real world;

and geologists were eager to compare it with the Earth.

Jim Head went straight to the biggest volcanoes he knew

on the Island of Hawaii.

I remember when Olympus Mons first came out of the clouds

on Mariner 9; it was absolutely spectacular,

this gigantic volcano.

And I couldn't wait to get back here to Hawaii

to get some sense of the perspective and scale

from something that I knew about.

And here we are on the edge of this volcano,

this incredibly large volcano,

one of the largest on the Earth,

and in fact it's like tiny compared to Olympus Mons.

To travel right across the crater

of Olympus Mons would mean a journey of 600 miles,

an area the size of France.

It's covered with crumbling red lava.

The volcanoes were just the start.

As the dust withdrew, Mariner 9's cameras

snapped thousands more pictures.

A whole new world was taking shape.

NASA called in scientists with a new expertise:

planetary geologists.

When this thing began to shape up

and we began to see all these features, that was the first

time that this whole Planet Mars

had ever really begun to take shape in the sense

of knowing what the physical features were, the geology.

None of that stuff had ever been seen before.

It was a historical moment,

when you finally start, like with an orange,

peeling the peel off and exposing a planet for what it is.

As Mariner's cameras tracked across

the Red Planet, a giant crevice appeared.

Each day we'd get a new set of images,

and as they mosaic, then we say: "My god, look at that!

"Where's it going?"

And stretch clear across roughly an eighth of the Planet.

They had discovered the biggest canyon ever seen.

Valles Marineris is 4,000 miles across

and maybe 100 miles at its widest

and as much as six miles deep.

Scale of the United States is something like that.

The scale of the United States I think is,

over there would be San Francisco

and over here would be New York, something like that.

So it would span the United States.

And this little canyon right here

is the size of the Grand Canyon.

The Valles Marineris probably cracked open

when the four giant volcanoes to its north pushed up,

breaking open the surface of the Planet.

Martian geology is written on a scale

that dwarfs the Earth's.

Giant features, like Valles Marineris and Olympus Mons,

have been steadily growing in the same place

for billions of years.

This suggested that the surface of the Planet did not move,

unlike the drifting continents of the Earth.

Mariner 9 had gone in search of geological life

and had found it.

So it was a very active Planet;

it was a planet that had real geology, active geology

going on even in modern geologic history.

But was it all history?

Was Mars a graveyard of geology from the distant past?

Or were the volcanoes still alive?

To find out, a probe needed to land on the Planet's surface.

Jerry Soffurn was the mission's scientist.

The whole point of Viking is to be the first time

you really explored the surface of the Planet.

The Mariners had actually orbited, or flown by, the Planet,

but the idea of actually getting a lander on the surface

of Mars, it was as important as Columbus' voyage.

I was absolutely terrified that we wouldn't

land successfully because I had spent so much of my life

aimed at this great moment in history.

14,000 feet.

15,480 feet per second.

3,000 feet.

On July the 20th, 1976,

Viking dropped into Mars' upper atmosphere

and began its descent.

8.4 Gs.

ATS is green, 1.5 degrees per second max.

0.2 Gs.

Eight feet per second.

When the landing took place,

it was like it was two minutes ago.

I can see every single face and the expectation.

The signals from Viking took 18 minutes

to travel back to Mission Control.

The scientists could do nothing but wait.

And when the touchdown came, I just exploded inside.

Touchdown! We have touchdown!

Yeah!

We have touchdown.

We're looking good.

That is a treat.

Copy, power.

We're out of sync.

The idea of being there in history

when the first landing on Mars took place was thrilling.

And now, what everyone wanted to know:

What would the surface of Mars look like?

Was it gonna be like someplace on the US?

Was it gonna be a desert?

Was it gonna be sandy, or dusty?

But all we knew is that it was gonna be red.

An hour after Viking landed,

the first black-and-white pictures began to be sent back.

Line by line, the surface of Mars was revealed.

Then came color pictures.

The surface was littered with rocks,

some of them dark and porous, clearly volcanic.

They must have been hurled there by volcanoes.

We knew there were volcanoes on Mars but

actually see a piece of the volcano was just astonishing.

But when had the pieces landed there?

Viking carried a device to find out

whether Mars was still active,

a seismometer, to tell if the ground was shaking.

Viking listened and waited, but felt nothing.

For all its spectacular volcanoes and canyons, it seemed

that geological activity on Mars was a thing of the past.

While the Americans were putting all their efforts into Mars

the Russians headed for Venus.

This world is almost as large as the Earth,

and geologists had always thought it would be our twin.

But Venus was no easy target.

The surface was hidden by a thick blanket of cloud;

but below that serene exterior were hellish conditions.

The pressure of the atmosphere had already

crushed three Soviet probes.

The Russians had found to their cost that the temperature

on the surface was nearly 500 degrees centigrade.

In 1975 they tried again,

and equipped their probe with a camera.

They hoped it would cling on long enough

to send back just one picture of the surface.

The mission chiefs didn't want anyone

to know that it might fail.

Seconds after landing, signals showed

Venera 9 systems were intact.

But on the surface the temperature was hotter than an oven.

Would the probe survive long enough to send back an image?

The camera had captured a blurred view of some rocks.

It was the first-ever image of the surface of Venus.

But it was only a tantalizing glimpse.

With their next probe,

the Russians hoped for something more.

On landing, all systems radioed back OK,

but there was no image of the surface.

Sasha Basilevski was on the team

that tried to work out what had gone wrong.

We had technical meeting and there was discussion

and chief designer that time told:

"You know, I have an idea that we have landed

"in something very sticky and viscous."

And then nasty voice told:

"Yes, sir, in the shit."

But Venera had not sunk.

The intense heat on the surface had melted

the lens cap onto the camera.

Three years later, another pair of probes headed for Venus.

This time, they took beautiful pictures

of a patch of ground filled with lava.

But when the probe tried to sample the newzean rock,

that lens cap came back to haunt them.

Venera 14S, Venera 13, they had special device

to measure electric properties

and mechanical properties of the surface.

It's some arm, this arm goes and puts device

on the surface, it measures.

And Venera 14 did it in a perfect way,

but it just get the cap.

So we measured mechanical properties

and the electrical properties of that thing

they brought from Earth.

On the Planet's surface, the probes

could only survive for an hour or two at most.

Somehow another way had to be found

to see through the clouds.

In 1989, NASA launched Magellan.

Magellan wouldn't take pictures but would scan the planet

with radar to make out the contours of the surface,

cutting through the clouds as if they weren't there.

We were able to actually come around the globe

every day many times and build up a picture

of the global geology of Venus.

Magellan began to send back reams

and reams of data, and a whole new generation

of geologists set to work on it.

When the first image data came back from Magellan,

I went in about four in the morning,

looked at the first strip of Magellan data,

this first track down the Planet.

To see the Planet's surface being revealed

in such incredible detail and to say:

"I'm one of the first people who's ever looked

"at this piece of ground on Venus."

You felt like such an explorer.

The first images showed that Venus had

many similarities to Earth.

There were large mountain ranges;

some of them almost similar to the Himalayas.

There were long faults on the Planet that looked

maybe sort of similar to faults we see on the Earth.

There were volcanoes, lots and lots of volcanoes

on the surface, very large ones,

much larger than some on the Earth,

others on a similar scale.

But then, an alien landscape began to emerge.

There were these huge circular features.

And by huge, I mean about 250, 300 kilometers across.

They were encircled by ridges and they were high,

they were sort of mountainous, and they tended to have

volcanoes all over the surfaces of 'em,

"What are these features?

"How could they have formed?"

We've never seen anything like them.

The 3D images revealed giant blisters

that had oozed lava from every crack.

And the surface of Venus seemed

to have channels running through it.

They looked like long rivers going across

the surface of the Planet.

But we know with Venus' incredibly-high surface temperatures

there's no way that water could have formed those channels

so they had to have been formed by lava.

There are other volcanic features that look like pancakes;

they have very steep sides and very flat tops

and it literally looks like somebody threw

a bunch of pancakes out onto the surface of the Planet.

There were other kinds of volcanoes that looked like

little squashed bugs, like ticks.

Everywhere you look you see some sort of volcanic feature:

a flow, a small volcano, a weird channel.

It's just dominated by volcanism and that's just something

we weren't prepared for really at all.

It's intriguing to look at this surface

that you say: "It should be so much like the Earth;

"it's not; how did it get this way?"

It's just a puzzle.

And to me, that's what makes Venus so interesting.

But when had this volcanic surface formed?

Geologists hoped that by counting impact craters,

they could find out.

When we got the global picture together,

we started counting craters and looking for areas

that had a high density of craters and an area

that would have low density, indicating old and young ages.

When we look at the Moon, we look at Mars,

we look at Mercury, you have areas where you say:

"OK, this area has more craters, it's older;

"this area has fewer craters, it's younger."

But the amazing part was it looked like the craters

were almost randomly distributed across the surface.

And you say: "Wait a minute, the whole Planet,

"it can't be the same age."

It's the size of the Earth.

How could you have a planet the size of the Earth

where the entire surface formed at the same time.

It just didn't make any sense.

So what possible theory could explain

how Venus' surface was formed?

Well, it was really mystifying because nobody could

really be sure, since we hadn't seen anything like this,

what was going on.

One of the main ideas that came out was the idea

that Venus' may have actually been catastrophically

resurfaced just a few hundred million years ago.

The idea that Venus boiled over

in a planetwide flood of lava is still fiercely debated.

But if it did, and has now cooled down,

could it ever erupt again?

The most exciting thing would be to find

an erupting volcano on Venus to say: "Here we have proof

"Venus is still geologically active.

"It really is the Planet most like the Earth

"and here's proof of it.

"It's not a dead planet;

"it's still alive; it's still active."

And that's something that I would

give a awful lot to be able to find.

Magellan scans the Planet for four years,

but found no fresh lava flows.

Venus may well be alive,

but there's no sign of it yet.

Of course if you were in orbit around Earth for a year,

you might not see any volcanic activity at all;

so it's really hard to tell whether it's actually going.

It's like trying to find the smoking gun

or the smoking volcano; it's not easy to find.

Despite the discoveries of Magellan,

Venus remains a Planet shrouded in mystery.

Was Earth the only place where geologists

would find active volcanoes?

It was beginning to look that way.

The only other rocky planet is Mercury.

But it's a small world, barely bigger than our Moon,

and its surface is just as dead and full of craters.

No geological activity has ever been found on Mercury.

The outside of the Planet is baking hot;

but inside, it is stone cold.

There was no hope of finding anything on Jupiter

or the other giant planets

because they have no solid surface.

But there is some solid rock out here.

On its way past Jupiter, Voyager flew by the Planet's moons.

No one expected to see much going on at all

in these tiny worlds.

We expected small objects the size of the Moon or smaller

to be pretty lifeless geologically

and expected them to be

holding records of the very early Solar System.

The impact processes and fairly esoteric kinds of questions

that solar system geologists might be interested in

but not something the general public

would care a whole lot about.

The first thing we ran into course was Callisto

and that was pretty much what we had thought

one of these moons would look like.

Callisto is dark and icy.

Like Mercury, its cratered surface hasn't changed

for billions of years.

The next moon, Ganymede, is the largest in the Solar System.

It had little of interest.

As Voyager reached the Moon lo,

it was about to discover something completely unexpected.

As we looked at it from great distance

we saw a lot of dark spots on the surface,

which we thought maybe were gonna be impact craters.

But Voyager took a few pictures and sailed past lo.

The scientists wanted to focus on Jupiter.

Meanwhile, one of the engineers busied herself

with some routine spacecraft maintenance.

I came in about nine o'clock that morning

to the navigation area and the tape with the pictures

the spacecraft had taken the day before was on my desk.

I put them on the computer system and I displayed them.

And I could see that the Moon of lo was a crescent,

as very often our own Moon is a crescent in the night sky.

I went and enhanced the brightness and there appeared

beside lo an object, a huge object

that looked like something I couldn't recognize

and could never have expected

and it completely captured my attention.

I wanted to know so badly what that was

that I just had to ask myself:

"My goodness, what is that?"

And the answer that occurred to me first

was it looked like another moon peaking out behind lo.

But there was no other moon,

and no fault in the camera.

Linda Hyder decided that this object had to be part of lo.

And in fact that was very hard to accept

because the size of this object was enormous

with respect to the size of lo.

And when I explored it I was able to find

that this large strange object,

it was exactly coincident

and fell over a heart-shaped feature on lo.

What I had discovered was the huge plume

of a volcanic eruption arising 270 kilometers

over the surface of lo and raining back down onto it.

So I had discovered the first-ever volcanic eruption

ever seen on another world besides the Earth.

We didn't really expect to find active volcanic eruptions

throwing material from a volcanic vent

to an altitude of a couple hundred miles,

300 kilometers above the surface.

This stuff goes up with a velocity of a high-powered rifle,

and of course it comes back onto the surface

with the same velocity, so a healthy place to stand

would not be the surface of lo.

The entire surface of lo is covered with volcanoes,

so volcanoes are not unique to our Earth.

But why is lo volcanically active?

It's only the size of our Moon.

It should be cold inside.

Head of the Voyager camera team was Brad Smith.

Up to this point, he'd concentrated on Jupiter's atmosphere.

Now he took a look at lo.

Io is a very small body.

It doesn't have enough of the radioactive materials

that heat up the rock, as happens on the Earth,

and so we didn't expect any kind of volcanism on lo.

The explanation was to be found in our own Moon.

And a NASA scientist in California had predicted it.

Well, as you can see, the power of the Moon's gravity

can move oceans on the Earth.

Imagine what the power of Jupiter,

which is 300 times the mass of the Earth,

can have on lo.

Now, lo, as it circles Jupiter,

approaches Jupiter closer at one point than at another.

What this does is it changes the gravitational force

from Jupiter and results in a giant squeeze.

Physicist Ray Reynolds had realized

that Jupiter's huge gravitational force

was causing the interior of lo

to heat up to incredible temperatures.

We plugged in the numbers into our equations

and lo and behold, we come out with thousands

of degrees near the surface of this satellite.

Well, this immediately raised visions

in our mind of volcanoes going off.

But nobody could have predicted the ferocity

of the sulfur-spewing volcanoes that Voyager found.

Io is just enormously volcanically active,

and more active than the Earth

and any other body in the Solar System.

There's nothing that even comes close to it.

Its surface is completely covered with volcanic debris.

Finally, geologists had found a world

that was alive yet constantly changing.

Draw a map of lo, and it will be obsolete by the next day.

But lo wasn't the only surprise Voyager found.

Next to it lay the Jupiter Moon Europa,

a bright dazzling world.

Europa was surprisingly smooth;

that is, there was little or no topography on it at all.

Scaled down it would have been as smooth as a billiard ball.

And why it should be, why there was no topography

we could only guess.

Close up, scientists were baffled by its surface.

When we looked at Europa, we see

a startling lack of craters and we also see

that there are large linear features

that look like cracks on the surface.

Reynolds thought the cracks might be

a result of the constant pressure

from Jupiter's huge gravitational force.

And there was an intriguing possibility.

Europa's surface is made of ice.

Could that mean that there might be water beneath?

Our calculations indicated that there was

a good possibility that there could be

a ocean beneath a thin ice layer.

Voyager's images were too crude

to prove or disprove the idea of a subterranean ocean.

But 16 years later, another spacecraft, Galileo,

returned for a closer look.

Close up, Europa's surface looks

like a crazy paving of ice.

There are giant icebergs.

It seems that hot water has welled up

through a network of cracks from below

and then frozen instantly in place,

just like lava from a volcanic eruption on Earth.

Instead of hot rock that's coming out,

it's water, it's liquid water.

But the principle is the same.

There's a fluid down underneath the crust

and from time to time this pushes up and flows

onto the surface much in the same way

that hot lava flows onto the surface of the Earth.

No actual eruption of ice has yet been spotted

but Europa has opened up the possibility

of completely new kinds of geological worlds.

As space probes ventured further out,

they found other frozen worlds.

Among the moons of Saturn and Uranus

there were signs of strange geological events.

But it all seemed to have occurred millions of years ago.

Then, a decade after its encounter with Jupiter,

Voyager met Triton, Moon of Neptune.

Triton, as we got closer and closer,

became evident that it was gonna be a very tiny object

and that was covered with very very bright material.

That made it very cold,

the coldest thing we've encountered

so far throughout the Solar System.

Triton is so cold that even

its thin atmosphere of nitrogen freezes

into a solid icecap every winter.

To have expected geologic activity on such a surface

would be insane, frankly.

But when Voyager got close,

it saw there were dark streaks all over the fresh icecap.

Those dark markings had to be sitting on top of that ice.

They had to be laid down there in the recent past.

That meant something had to be going on to make them,

an active process.

Larry Sodablom spent two months

looking at pictures of Triton.

He examined images taken from slightly different angles

to try and build up a 3D view of the surface.

All of a sudden, he saw something

that seemed to stand up from the ice.

One afternoon we were stunned to find

active geysers shooting up above the Triton icecap.

Geysers, fountains of material rising five, 10 kilometers

or miles above the surface.

Even in this dark corner of the Solar System,

the faint heat of the Sun manages

to penetrate Triton's icecap.

It warms liquid nitrogen trapped beneath the surface

up to the point where it bursts out and rises up into space

before turning 90 degrees into Triton's high-altitude winds.

It's almost as if Triton was the last sentence

in the message that we got from the Voyager Mission,

that no matter where you go in the universe,

expect the unexpectable.

Changed that whole concept of what volcanism is.

Our classical concept of course before Voyager

was volcanism was hot rock coming out

of the interior of a planet.

But Voyager showed us that there are other materials

as well that produce volcanism.

On lo we saw molten sulfur, sulfur dioxide.

On Europa, water is an important element.

And on Triton, liquid nitrogen may actually be

the fluid that's involved in volcanism.

After so many amazing discoveries

across the Solar System, geologists are now returning

to the Earth's neighboring planets.

In 1997, NASA returned to Mars

with a new orbiting spacecraft that's providing

greater detail than ever before.

Mars Global Surveyor can pick out individual boulders

on the ground and can spot places where

they've rolled down into gullies.

Could these be evidence of tremors?

And a new probe, Mars Express,

has now discovered evidence of methane on the Red Planet.

Could all this point to geological activity on Mars?

What we're seeing now on Mars is like a shot

from a helicopter compared to a shot from a space shuttle.

The whole sense of Mars is a little bit different

when you get down to the size of detail that we can see.

And we're just beginning to get into that

and get a sense of what's really going on on Mars.

Soon we will have a map of Mars

that's as detailed as those of the Earth.

Now when I come out to Hawaii,

my whole perspective has changed.

I walk around on the surface here,

and in fact I'm beginning to see things

that are the same scale that I'm seeing on Mars

and it's incredibly exciting.

It's bridged the gap; it's brought it together

so it's almost like I'm walking around on Mars.

I think this is the way it's worked with all the planets.

They initially were alien objects

that you had little knowledge about.

But particularly from the geology you begin to see

old friends: volcanoes and lava flows,

sand dunes and so on.

And then little by little you transport yourself there,

you think about there.

I wake up in the night, I have a dream about being on Mars.

It's just amazing.

One day soon, a probe may also return to Venus

and perhaps survive for long enough in its hostile

atmosphere to observe a volcano erupting.

We now know that the Earth is just one

in a Solar System of active worlds.

Every year brings new discoveries.

The Galileo Probe was one of the most

ambitious projects so far.

It gave us a unique insight into Io, one of Jupiter's moons.

We now know it is the most volcanically-active world

in the Solar System.

But the Galileo is no more.

With its fuel spent and suffering critical radiation damage,

it dived headlong into Jupiter's vast atmosphere.

It was the end for the spacecraft;

but this is just the start of our new voyage of discovery

into the Solar System.