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The landscapes of Earth have been shaped by volcanoes. | 0:00:05 | 0:00:09 | |
We've long been in awe of their destructive beauty. | 0:00:12 | 0:00:16 | |
But only recently have we discovered that volcanism exists beyond Earth. | 0:00:17 | 0:00:23 | |
The planets and moons of the solar system have volcanoes that are even | 0:00:26 | 0:00:31 | |
more extraordinary than those on our home planet. | 0:00:31 | 0:00:34 | |
Rivers of lava once raced across our moon. | 0:00:36 | 0:00:39 | |
It's an amazing thought that you could have been standing on Earth | 0:00:39 | 0:00:43 | |
and looked up at the moon, and seen these massive eruptions happening. | 0:00:43 | 0:00:46 | |
The largest volcano of the solar system, | 0:00:49 | 0:00:52 | |
three times the height of Everest, is on Mars. | 0:00:52 | 0:00:56 | |
The most violent volcano is on a moon of Jupiter. | 0:00:58 | 0:01:02 | |
Huge, icy geysers fountain out into space from a moon orbiting Saturn. | 0:01:06 | 0:01:12 | |
We have not closed the book on volcanism across the solar system by any means. | 0:01:12 | 0:01:16 | |
But what's most remarkable is what volcanic activity elsewhere in | 0:01:18 | 0:01:22 | |
the solar system has told scientists about our own planet, Earth. | 0:01:22 | 0:01:27 | |
What the Earth was like at its birth, | 0:01:30 | 0:01:34 | |
why we have the geology and the atmosphere we do. | 0:01:34 | 0:01:37 | |
And even how life on Earth, and possibly elsewhere, originated. | 0:01:39 | 0:01:44 | |
Way back in the ninth century AD, | 0:01:58 | 0:02:00 | |
a band of Vikings discovered Iceland. | 0:02:00 | 0:02:03 | |
They experienced volcanic eruptions for the first time. | 0:02:04 | 0:02:07 | |
To explain their devastation, | 0:02:12 | 0:02:14 | |
they evoked the terrible wrath of gods such as Surtr, the fire giant. | 0:02:14 | 0:02:19 | |
A Viking poet wrote, "In the beginning, all was cold and grim. | 0:02:20 | 0:02:25 | |
"Then came Surtr with a crashing noise. | 0:02:26 | 0:02:29 | |
"Bright and burning, he bore a flaming sword." | 0:02:31 | 0:02:35 | |
A millennium later, and a team of international scientists has also | 0:02:43 | 0:02:47 | |
travelled to the land of fire and ice. | 0:02:47 | 0:02:50 | |
This small country has more types of | 0:02:57 | 0:03:00 | |
volcanoes and geological wonders packed into it | 0:03:00 | 0:03:03 | |
than anywhere else in the world. | 0:03:03 | 0:03:05 | |
For the team, it allows them to compare the volcanism of Earth with | 0:03:10 | 0:03:14 | |
volcanoes found elsewhere in the solar system. | 0:03:14 | 0:03:17 | |
You've got these continual cycles of glaciers and volcanoes. | 0:03:20 | 0:03:23 | |
Absolutely brilliant. | 0:03:23 | 0:03:25 | |
Yeah, you have a really diverse range of volcanic features here, | 0:03:25 | 0:03:28 | |
and I think it's a good place to see the importance of volcanism. | 0:03:28 | 0:03:31 | |
For geologist Jim Head, | 0:03:37 | 0:03:39 | |
Iceland is a familiar landscape. | 0:03:39 | 0:03:41 | |
In the 1960s, | 0:03:43 | 0:03:45 | |
he was teaching the Apollo astronauts all about rocks | 0:03:45 | 0:03:48 | |
before they headed off to the moon. | 0:03:48 | 0:03:50 | |
We took them everywhere we could | 0:03:52 | 0:03:53 | |
that would give them geological information. | 0:03:53 | 0:03:55 | |
Iceland was clearly one of those. | 0:03:55 | 0:03:57 | |
And I think it's completely perfect, actually, | 0:03:57 | 0:04:01 | |
that we are here today in Iceland, studying the volcanoes that | 0:04:01 | 0:04:04 | |
actually propelled the astronauts to go to the moon. | 0:04:04 | 0:04:07 | |
Five, four, three, two, one. | 0:04:10 | 0:04:16 | |
The Apollo missions weren't just about the space race. | 0:04:16 | 0:04:19 | |
They were also the most ambitious geological field trips of all time. | 0:04:21 | 0:04:25 | |
A key aim was to discover if volcanoes | 0:04:27 | 0:04:30 | |
had helped create the moon. | 0:04:30 | 0:04:32 | |
And, if so, were any still active? | 0:04:33 | 0:04:36 | |
Before the Apollo programme, | 0:04:37 | 0:04:38 | |
we didn't even know whether the moon had volcanism. | 0:04:38 | 0:04:41 | |
For example, some people thought it was a cold moon, | 0:04:41 | 0:04:43 | |
some people thought it was a warm moon, | 0:04:43 | 0:04:45 | |
which had heating inside and volcanism. | 0:04:45 | 0:04:46 | |
So this is a big question - was it even volcanic rock? | 0:04:46 | 0:04:49 | |
2,000 feet, 2,000 feet. | 0:04:49 | 0:04:51 | |
47 degrees. Roger. | 0:04:51 | 0:04:54 | |
These dark-looking plains of the moon | 0:04:57 | 0:04:59 | |
were particularly tantalising to scientists. | 0:04:59 | 0:05:03 | |
They're called the seas, or the maria. | 0:05:03 | 0:05:07 | |
Beautiful view! Isn't that something? | 0:05:09 | 0:05:12 | |
Magnificent desolation. | 0:05:12 | 0:05:14 | |
To find out exactly what they were, | 0:05:14 | 0:05:16 | |
the first Apollo landing was to Mare Tranquillitatis, | 0:05:16 | 0:05:20 | |
the Sea of Tranquillity. | 0:05:20 | 0:05:21 | |
OK, ready for me to come out? | 0:05:21 | 0:05:23 | |
All set. | 0:05:23 | 0:05:26 | |
As the astronauts explored the dusty and rocky surface, | 0:05:26 | 0:05:29 | |
they recognised basalt - the most common volcanic rock found on Earth. | 0:05:29 | 0:05:34 | |
And lots of it. | 0:05:37 | 0:05:38 | |
When you erupt molten rock on a moon, liquid rock on the moon, | 0:05:39 | 0:05:43 | |
it actually is one sixth gravity, | 0:05:43 | 0:05:45 | |
so it's much less gravity than we see on the Earth. | 0:05:45 | 0:05:47 | |
It looks like a collection of just about | 0:05:47 | 0:05:50 | |
every variety of rock you could find. | 0:05:50 | 0:05:53 | |
If the lava is coming up from great depths, given the gravity, etc, | 0:05:53 | 0:05:59 | |
you'll get a lot of lava coming up, | 0:05:59 | 0:06:01 | |
commonly much more than you see on the Earth, | 0:06:01 | 0:06:03 | |
and so it flows great distances, | 0:06:03 | 0:06:04 | |
and so we have lava flows that go over 1000 kilometres, | 0:06:04 | 0:06:08 | |
like, incredible, it would go | 0:06:08 | 0:06:10 | |
halfway across the United States, no problem. | 0:06:10 | 0:06:12 | |
Another mysterious feature found on the moon | 0:06:13 | 0:06:16 | |
was these winding canyons, or sinuous rilles. | 0:06:16 | 0:06:20 | |
These channels were up to 400 metres deep and over 100km long. | 0:06:22 | 0:06:27 | |
Clues as to what created them can be found back on Earth. | 0:06:29 | 0:06:33 | |
Under the south-west of Iceland are curious tunnels through solid rock. | 0:06:41 | 0:06:46 | |
They appear almost man-made. | 0:06:46 | 0:06:49 | |
Gro Pedersen is exploring one. | 0:06:52 | 0:06:55 | |
In the depths of the tunnel, | 0:06:57 | 0:06:59 | |
she hopes to find evidence of what used to flow through it. | 0:06:59 | 0:07:02 | |
You can actually see how the lava has been running along the wall here, | 0:07:03 | 0:07:08 | |
and you can see also that it was very hot in here, | 0:07:08 | 0:07:11 | |
because some of this lava re-melted, | 0:07:11 | 0:07:13 | |
and basically was dribbling down the wall. You see that here. | 0:07:13 | 0:07:17 | |
It's a lava tube and, long ago, lava was surging through these tunnels. | 0:07:19 | 0:07:24 | |
One of the very exciting things people found on the moon | 0:07:26 | 0:07:29 | |
was these sinuous rilles and, | 0:07:29 | 0:07:31 | |
of course, before people actually had been on the moon, | 0:07:31 | 0:07:34 | |
they were thought to potentially be water eroded. | 0:07:34 | 0:07:38 | |
But then people have gone to the moon, | 0:07:38 | 0:07:40 | |
and it has been studied much more and we've found out that these | 0:07:40 | 0:07:44 | |
sinuous rilles were always connected with the maria, | 0:07:44 | 0:07:49 | |
the moon lava that we have up there. | 0:07:49 | 0:07:52 | |
Perhaps these sinuous rilles were once enclosed lava tubes. | 0:07:53 | 0:07:57 | |
So one of the things that you see here, obviously, | 0:08:00 | 0:08:02 | |
is that we have what we call skylights, | 0:08:02 | 0:08:05 | |
so the roof has collapsed. | 0:08:05 | 0:08:06 | |
If all of the roof collapses, you will end up with a valley, | 0:08:06 | 0:08:10 | |
like something you see on the moon. | 0:08:10 | 0:08:12 | |
But you can also see the tubes on the moon by a string of skylights, | 0:08:12 | 0:08:18 | |
just as we see here, one hole after the other, and you just follow them, | 0:08:18 | 0:08:21 | |
you trace them down and you can see that these are within lava flows. | 0:08:21 | 0:08:25 | |
But when did these eruptions take place? | 0:08:27 | 0:08:30 | |
And why did they eventually stop? | 0:08:30 | 0:08:32 | |
The answer would come in small bags of volcanic rocks | 0:08:37 | 0:08:40 | |
brought home by the astronauts. | 0:08:40 | 0:08:42 | |
On Earth, they could be accurately dated. | 0:08:44 | 0:08:47 | |
So when the moon rocks were brought back, it's, like, unbelievable. | 0:08:47 | 0:08:50 | |
OK, this we can tell, four-billion-year-old rocks. | 0:08:50 | 0:08:54 | |
These are the keys to the understanding of the solar system. | 0:08:54 | 0:08:57 | |
Like other planetary bodies made of rock, | 0:08:59 | 0:09:02 | |
the moon was a mass of hot molten magma as it was forming. | 0:09:02 | 0:09:06 | |
It's an amazing thought that you could have been standing on Earth | 0:09:06 | 0:09:11 | |
and looked up at the moon and seen these massive eruptions happening. | 0:09:11 | 0:09:14 | |
But all the time, it was cooling - | 0:09:17 | 0:09:19 | |
being relatively small, a quarter the diameter of the Earth, | 0:09:19 | 0:09:24 | |
the moon cooled down quickly. | 0:09:24 | 0:09:26 | |
By three billion years ago, | 0:09:27 | 0:09:29 | |
almost all the lava and interior magma had solidified | 0:09:29 | 0:09:33 | |
into one big lump of cold rock. | 0:09:33 | 0:09:35 | |
No more volcanoes. | 0:09:37 | 0:09:38 | |
But you see the remnants of it. | 0:09:45 | 0:09:46 | |
I mean, when you look at the sky and you look at the moon, | 0:09:46 | 0:09:49 | |
you see the evidence of the volcanism, | 0:09:49 | 0:09:52 | |
because you see the dark areas, the basalt, | 0:09:52 | 0:09:54 | |
which has filled in the craters. | 0:09:54 | 0:09:56 | |
Understanding how the moon lost its volcanoes | 0:09:58 | 0:10:02 | |
helps explain why Earth remains so active. | 0:10:02 | 0:10:05 | |
Being larger allowed the Earth to retain much of its original heat. | 0:10:08 | 0:10:12 | |
And so today, our planet is a dynamic and ever-changing world, | 0:10:16 | 0:10:20 | |
rather than a dead one. | 0:10:20 | 0:10:23 | |
So, the discovery on the moon of lava flows | 0:10:23 | 0:10:26 | |
gave us pause to think about how this worked | 0:10:26 | 0:10:29 | |
on other planetary bodies. | 0:10:29 | 0:10:30 | |
How does volcanism work on Mars? | 0:10:30 | 0:10:32 | |
So, the lunar exploration really opened up | 0:10:35 | 0:10:37 | |
a field of, really, planetary volcanology. | 0:10:37 | 0:10:40 | |
Exploring our neighbour, Mars, | 0:10:44 | 0:10:47 | |
also reveals secrets about Earth's geology. | 0:10:47 | 0:10:50 | |
When probes first reached the red planet, | 0:10:52 | 0:10:55 | |
one feature stood out above swirling sandstorms. | 0:10:55 | 0:10:58 | |
The volcano Olympus Mons. | 0:10:59 | 0:11:01 | |
Olympus Mons is enormous, it's about 25km high. | 0:11:06 | 0:11:10 | |
On Earth, you would be looking at something ridiculously high. | 0:11:10 | 0:11:14 | |
Most commercial aircraft fly 10-15 kilometres. | 0:11:14 | 0:11:18 | |
So you're looking at something that is towering way above | 0:11:18 | 0:11:21 | |
what commercial aircraft might fly. | 0:11:21 | 0:11:23 | |
Its base covers an area the size of France. | 0:11:29 | 0:11:32 | |
It's three times the height of Mount Everest. | 0:11:34 | 0:11:36 | |
Making it the largest volcano ever discovered in the solar system. | 0:11:38 | 0:11:42 | |
Finding out how it grew to be so colossal | 0:11:48 | 0:11:50 | |
tells scientists more about the volcanoes of Earth. | 0:11:50 | 0:11:54 | |
That's why three of the team have come together to study this volcano. | 0:11:59 | 0:12:04 | |
Icelanders call it Skjaldbreidur, which means "broad shield", | 0:12:07 | 0:12:12 | |
as side on, it's reminiscent of a Viking shield. | 0:12:12 | 0:12:15 | |
Although small in stature, it's of great significance. | 0:12:19 | 0:12:22 | |
This shield volcano is the one over... | 0:12:25 | 0:12:28 | |
about which all the other volcanoes of this type are called, | 0:12:28 | 0:12:33 | |
in the solar system and on the Earth. | 0:12:33 | 0:12:35 | |
So this is the first one, in many senses, | 0:12:35 | 0:12:37 | |
the first one to be named the shield. | 0:12:37 | 0:12:39 | |
It's only 1,000 metres high, | 0:12:42 | 0:12:44 | |
a 25th the height of Olympus Mons, | 0:12:44 | 0:12:47 | |
but crucially, it's the same type of shield volcano. | 0:12:47 | 0:12:51 | |
At the summit is the crater. | 0:12:54 | 0:12:56 | |
Wow, now you can see the crater. | 0:12:57 | 0:12:59 | |
-Yeah. -Fantastic. -Wow! | 0:12:59 | 0:13:02 | |
That's very nice. | 0:13:02 | 0:13:03 | |
-I mean, you could even have come skiing up here. -Oh, wow. -Yeah. | 0:13:03 | 0:13:07 | |
Then we can imagine, like, a lava lake. | 0:13:07 | 0:13:10 | |
Yeah, just round the top. | 0:13:10 | 0:13:12 | |
-Yeah. -Dribbling over where we are now. -Yeah. | 0:13:12 | 0:13:15 | |
Around the rim are mysteriously-shaped rocks. | 0:13:15 | 0:13:18 | |
They look almost like fossilised snakes. | 0:13:21 | 0:13:23 | |
Yet they give a hint how this type of volcano forms, | 0:13:26 | 0:13:29 | |
and what gives it the distinctive shield shape. | 0:13:29 | 0:13:32 | |
This is a type of lava we call entrail, | 0:13:35 | 0:13:38 | |
and it's a bit like the entrails from the inside of a human body | 0:13:38 | 0:13:42 | |
or any animal body. | 0:13:42 | 0:13:44 | |
They're characteristically quite thin. | 0:13:44 | 0:13:45 | |
I mean, you can see from the shape of my hand, | 0:13:45 | 0:13:47 | |
it's a couple of hand widths. | 0:13:47 | 0:13:49 | |
Shield volcanoes comprise lavas that are very runny, | 0:13:49 | 0:13:52 | |
because the shapes of them, | 0:13:52 | 0:13:53 | |
this broad shield shape, tells us it has to have been. | 0:13:53 | 0:13:56 | |
And we have the evidence in front of our eyes of these small tubes, | 0:13:56 | 0:14:00 | |
these entrails running down the sides of the volcano, | 0:14:00 | 0:14:03 | |
telling us that indeed, it had to be very runny. | 0:14:03 | 0:14:05 | |
This fast-flowing lava creates | 0:14:11 | 0:14:13 | |
the gentle slopes of all shield volcanoes, | 0:14:13 | 0:14:16 | |
including the largest one of all, on Mars. | 0:14:16 | 0:14:19 | |
But while shield volcanoes on Iceland | 0:14:26 | 0:14:28 | |
have just one crater at the summit, | 0:14:28 | 0:14:31 | |
Olympus Mons has six overlapping craters. | 0:14:31 | 0:14:34 | |
That's the key. We actually can use what we see in Iceland to say, | 0:14:37 | 0:14:41 | |
what we see in Mars is similar, but also different. | 0:14:41 | 0:14:44 | |
It has to be much, much longer lived with multiple phases of eruptions | 0:14:44 | 0:14:48 | |
to produce these multiple summit craters we see on Olympus Mons. | 0:14:48 | 0:14:52 | |
When this behemoth erupted, Mars shuddered. | 0:14:56 | 0:15:00 | |
Rivers of lava swept down the massive flanks of the volcano. | 0:15:07 | 0:15:11 | |
But Earth is twice the size of Mars, | 0:15:15 | 0:15:18 | |
so why don't we have volcanoes as enormous as Olympus Mons? | 0:15:18 | 0:15:22 | |
It's all to do with plate tectonics. | 0:15:27 | 0:15:30 | |
Earth is made up of seven huge plates | 0:15:32 | 0:15:35 | |
drifting above a sea of magma. | 0:15:35 | 0:15:37 | |
The circulation of magma recycles rocks and gases, | 0:15:42 | 0:15:46 | |
bringing them to the surface and then back down again. | 0:15:46 | 0:15:49 | |
Iceland is the perfect place to witness plate tectonics in action. | 0:15:54 | 0:15:58 | |
This rift is where the North American plate, to the left, | 0:16:00 | 0:16:04 | |
divides from its Eurasian cousin, to the right. | 0:16:04 | 0:16:07 | |
The rift is widening rapidly, at over two centimetres a year. | 0:16:10 | 0:16:14 | |
We've got the best evidence of plate tectonics we can find here. | 0:16:17 | 0:16:21 | |
You can see the tension of the plates moving apart from each other. | 0:16:21 | 0:16:25 | |
Yeah, this is the only planet that we know that's got plate tectonics. | 0:16:25 | 0:16:28 | |
Mars, like all other planets we know of, has no active plate tectonics. | 0:16:31 | 0:16:36 | |
The entire crust of Mars remains locked in place, | 0:16:41 | 0:16:45 | |
with repercussions for its volcanoes. | 0:16:45 | 0:16:47 | |
Any upwelling magma continually breaks through | 0:16:54 | 0:16:57 | |
at one fixed location. | 0:16:57 | 0:16:59 | |
On Mars, it's just centred, the same spot, for so long, | 0:17:01 | 0:17:05 | |
building up a huge volcano. | 0:17:05 | 0:17:06 | |
So it's a very focused eruption of magma for billions of years. | 0:17:06 | 0:17:13 | |
And what happens is you just end up with a huge volcano, | 0:17:13 | 0:17:16 | |
the biggest in the solar system. | 0:17:16 | 0:17:18 | |
While Mars is no longer volcanically active, | 0:17:27 | 0:17:30 | |
it does share an important feature with Earth - the polar ice caps. | 0:17:30 | 0:17:35 | |
The story of these ice caps | 0:17:38 | 0:17:40 | |
has been revealed through unusually shaped volcanoes. | 0:17:40 | 0:17:43 | |
They have steep sides and a flat top like a table. | 0:17:45 | 0:17:49 | |
Scientists now believe they might have been formed when volcanoes | 0:17:51 | 0:17:55 | |
exploded through an ancient ice sheet. | 0:17:55 | 0:17:58 | |
To understand how ice can change the behaviour of lava, | 0:18:04 | 0:18:07 | |
scientists are carrying out an extreme experiment. | 0:18:07 | 0:18:11 | |
For this, Ingo Sonder and Tracy Gregg need to make their own lava... | 0:18:15 | 0:18:20 | |
..out of 50kg of basalt rock. | 0:18:23 | 0:18:27 | |
We're turning it to its lava state, | 0:18:27 | 0:18:29 | |
and the students have built a little ramp | 0:18:29 | 0:18:31 | |
that the lava will pour down and pool at the end. | 0:18:31 | 0:18:34 | |
And at the end of this lava stream, there will be a little pond of ice. | 0:18:34 | 0:18:38 | |
So the lava's going to flow over the ice. | 0:18:38 | 0:18:41 | |
We know this has happened on Earth. | 0:18:41 | 0:18:43 | |
We think it's happened on Mars in the past. | 0:18:43 | 0:18:46 | |
So we'll see what happens. | 0:18:46 | 0:18:47 | |
The electrical furnace is running at 80,000 watts. | 0:18:51 | 0:18:55 | |
By now, the molten rock is over 1,200 degrees Celsius. | 0:18:57 | 0:19:02 | |
It's ready for the big pour. | 0:19:02 | 0:19:04 | |
Look where it hits the ice, it's boiling! | 0:19:11 | 0:19:14 | |
Because the ice is melting and it's flashing to steam. | 0:19:14 | 0:19:17 | |
And it's creating all those bubbles there on the lava. | 0:19:17 | 0:19:21 | |
Whoa! And now, this is what happens... | 0:19:21 | 0:19:23 | |
..when the lava melts the ice and there's enough water, | 0:19:25 | 0:19:29 | |
we're getting some little steam explosions. | 0:19:29 | 0:19:31 | |
Right, there's no more lava coming out of the furnace. | 0:19:33 | 0:19:36 | |
But underneath that black crust, it's still liquid, | 0:19:36 | 0:19:39 | |
it's slowly flowing down. | 0:19:39 | 0:19:41 | |
And you can see where it's ponded over the ice, | 0:19:41 | 0:19:44 | |
there's some heaving going on as gas is trying to escape. | 0:19:44 | 0:19:49 | |
The experiment lets Tracy identify | 0:19:49 | 0:19:52 | |
key features as molten rock interacts with ice. | 0:19:52 | 0:19:57 | |
When the lava hit the ice, a couple of things happened really fast. | 0:19:57 | 0:20:01 | |
The lava started to bubble, | 0:20:01 | 0:20:03 | |
as the ice melted and then flashed to steam. | 0:20:03 | 0:20:06 | |
And then, as more melt occurred, | 0:20:06 | 0:20:08 | |
there were actually puddles of water | 0:20:08 | 0:20:10 | |
that started to boil and spatter just like | 0:20:10 | 0:20:12 | |
on your stove, right, the water spattering. | 0:20:12 | 0:20:14 | |
Where the ice wasn't, we have nice, neat, organised flows, | 0:20:14 | 0:20:19 | |
folds in the lava. | 0:20:19 | 0:20:20 | |
And right where the ice starts, | 0:20:20 | 0:20:22 | |
we get these bigger bubbles on the surface. | 0:20:22 | 0:20:24 | |
Look, that one's broken open, you can see inside. | 0:20:24 | 0:20:27 | |
That's the kind of thing we could look for on Mars. | 0:20:27 | 0:20:29 | |
Right? To see if there was any lava-ice interactions on Mars. | 0:20:29 | 0:20:33 | |
Can you hear it? | 0:20:33 | 0:20:35 | |
As the lava cools, it contracts, | 0:20:35 | 0:20:36 | |
and it makes little pops like breakfast cereal. | 0:20:36 | 0:20:40 | |
Pop, pop. | 0:20:40 | 0:20:41 | |
Yep. | 0:20:41 | 0:20:42 | |
That's amazing. | 0:20:45 | 0:20:46 | |
The artificial volcano confirms that | 0:20:51 | 0:20:53 | |
lava behaves very differently when it meets ice. | 0:20:53 | 0:20:57 | |
But what happens out in the real world? | 0:20:59 | 0:21:02 | |
One of the most distinctive types of volcano in Iceland is called a tuya. | 0:21:08 | 0:21:14 | |
The team believe they can help explain the mountains | 0:21:16 | 0:21:19 | |
with a similar shape on Mars. | 0:21:19 | 0:21:21 | |
Wherever we see volcanoes that look like this, | 0:21:23 | 0:21:26 | |
on Iceland we know that the ice has been there, | 0:21:26 | 0:21:28 | |
and if we see the same sorts of volcanoes on Mars, | 0:21:28 | 0:21:31 | |
we've got a good idea or a very good idea that there was ice present. | 0:21:31 | 0:21:34 | |
There are two polar ice caps on Mars today. | 0:21:36 | 0:21:39 | |
But millions of years ago, | 0:21:43 | 0:21:44 | |
they were far more extensive. | 0:21:44 | 0:21:46 | |
Mapping the tuyas on Mars reveals | 0:21:49 | 0:21:52 | |
the coverage and depth of the ancient ice sheets. | 0:21:52 | 0:21:56 | |
That's amazing, that you can actually say something about | 0:22:01 | 0:22:04 | |
ice thickness in the past on a different planet, | 0:22:04 | 0:22:07 | |
after the ice has gone. | 0:22:07 | 0:22:09 | |
Which may have been three and a half billion years ago, as well. | 0:22:09 | 0:22:11 | |
-Yeah. -It's similar processes on different planets but it's yielding | 0:22:11 | 0:22:15 | |
valuable information. It's telling us about what most planets... | 0:22:15 | 0:22:18 | |
how they were evolving and what was happening at the time. | 0:22:18 | 0:22:21 | |
Today, Mars and our own moon are cold and desolate planetary bodies. | 0:22:22 | 0:22:28 | |
Geologically inert. | 0:22:30 | 0:22:32 | |
While Earth has retained active volcanoes. | 0:22:35 | 0:22:38 | |
To understand how we got here, | 0:22:41 | 0:22:43 | |
we need to find out what Earth was like four billion years ago. | 0:22:43 | 0:22:47 | |
And scientists think they've found the perfect place to look, | 0:22:51 | 0:22:55 | |
a moon far out in the solar system. | 0:22:55 | 0:22:58 | |
Ashley Davies is a top planetary volcanologist. | 0:23:11 | 0:23:14 | |
He's fascinated by a moon of Jupiter called Io. | 0:23:16 | 0:23:20 | |
One of the most important images that's ever been collected by any | 0:23:23 | 0:23:28 | |
spacecraft was obtained by Voyager at Io. | 0:23:28 | 0:23:32 | |
The image revealed this crescent rising above Io's surface, | 0:23:36 | 0:23:41 | |
no-one knew quite what this was. | 0:23:41 | 0:23:43 | |
Could it be another moon behind Io, or some artefact in the image? | 0:23:43 | 0:23:48 | |
And then it was realised that this was actually a huge volcanic plume | 0:23:48 | 0:23:53 | |
rising up from Io's surface. | 0:23:53 | 0:23:56 | |
For me, this was | 0:23:59 | 0:24:01 | |
an image that I think shaped the rest of my life, | 0:24:01 | 0:24:05 | |
because from this point... | 0:24:05 | 0:24:06 | |
I was a schoolboy and I realised this was a huge step in an unknown | 0:24:06 | 0:24:11 | |
direction for astronomy and planetary science. | 0:24:11 | 0:24:15 | |
And in a way, this actually put me on the path through school and into | 0:24:17 | 0:24:21 | |
scientific research, and finally brought me here to study | 0:24:21 | 0:24:24 | |
this absolutely astonishing little world. | 0:24:24 | 0:24:26 | |
We now know that crammed into Io, the same size as our moon, | 0:24:31 | 0:24:36 | |
are over 400 active volcanoes. | 0:24:36 | 0:24:39 | |
Compare this to just 60 on the whole of Earth. | 0:24:41 | 0:24:45 | |
The most powerful eruption was seen at a volcano called Surtr, | 0:24:49 | 0:24:54 | |
which is actually named after an Icelandic giant. | 0:24:54 | 0:24:58 | |
A fissure opened up and a huge volume of lava literally gushed out | 0:24:58 | 0:25:03 | |
of the ground to form large lava fountains kilometres high. | 0:25:03 | 0:25:07 | |
It must have been an absolutely incredible sight to see | 0:25:07 | 0:25:10 | |
if you were there to witness it, but not from too close by. | 0:25:10 | 0:25:13 | |
When Surtr roars, | 0:25:14 | 0:25:16 | |
it sends plumes of lava and ash over 500km into space. | 0:25:16 | 0:25:22 | |
Io proved for the first time | 0:25:31 | 0:25:33 | |
that Earth wasn't alone in having active volcanoes. | 0:25:33 | 0:25:36 | |
And, perhaps more importantly, | 0:25:42 | 0:25:44 | |
Io offered a clue as to the conditions | 0:25:44 | 0:25:47 | |
that existed as the Earth formed. | 0:25:47 | 0:25:49 | |
But first, scientists needed to discover | 0:25:51 | 0:25:54 | |
where the heat driving Io's volcanism came from. | 0:25:54 | 0:25:57 | |
The reason why Io is so active | 0:25:59 | 0:26:02 | |
is it's caught in this gravitational tug-of-war between Jupiter, Io, | 0:26:02 | 0:26:09 | |
Europa and Ganymede, | 0:26:09 | 0:26:11 | |
and this pumps a lot of energy into the system. | 0:26:11 | 0:26:13 | |
What happens to a squash ball is just like Io, | 0:26:20 | 0:26:25 | |
as it's pulled between gigantic Jupiter and her other moons. | 0:26:25 | 0:26:30 | |
A thermal camera reveals the temperature of the squash ball | 0:26:32 | 0:26:36 | |
as the rallies progress. | 0:26:36 | 0:26:38 | |
We hit the ball against the wall and it heated up. | 0:26:39 | 0:26:44 | |
And it heated up because it was being compressed, | 0:26:46 | 0:26:48 | |
twisted and turned. | 0:26:48 | 0:26:50 | |
And Io is very much like that. | 0:26:51 | 0:26:54 | |
With Io, it's being twisted and turned and squeezed by gravitational | 0:26:55 | 0:27:00 | |
forces, and the gravitational forces | 0:27:00 | 0:27:03 | |
cause a lot of interior heating and the heating manifests at the surface | 0:27:03 | 0:27:07 | |
as huge volcanoes. | 0:27:07 | 0:27:09 | |
Io heats up so much that it might erupt | 0:27:13 | 0:27:16 | |
an extremely rare and hot form of lava called ultramafic. | 0:27:16 | 0:27:21 | |
Ultramafic lava was abundant 4.5 billion years ago, | 0:27:25 | 0:27:29 | |
when the Earth formed, | 0:27:29 | 0:27:33 | |
but no longer. | 0:27:33 | 0:27:34 | |
To discover this primitive lava on Io | 0:27:36 | 0:27:39 | |
would offer scientists a window on the past. | 0:27:39 | 0:27:42 | |
Volcanologist Rosaly Lopes does her research in Hawaii. | 0:27:52 | 0:27:57 | |
We're studying volcanoes on Hawaii not because of Hawaii itself, | 0:27:57 | 0:28:01 | |
but because Hawaiian volcanoes are such a good analogue, | 0:28:01 | 0:28:07 | |
or a mirror if you like, for volcanoes on Jupiter's moon, Io. | 0:28:07 | 0:28:11 | |
And it's really understanding the volcanoes on Io | 0:28:11 | 0:28:16 | |
that we are after. | 0:28:16 | 0:28:18 | |
Hawaii has more active volcanoes than anywhere on Earth. | 0:28:23 | 0:28:27 | |
In fact, the islands are a chain of shield volcanoes, | 0:28:29 | 0:28:33 | |
built up from the ocean floor. | 0:28:33 | 0:28:35 | |
Rosaly looks for the most active lava flows. | 0:28:36 | 0:28:39 | |
It's challenging, it's beautiful. | 0:28:41 | 0:28:44 | |
I think a volcano in activity | 0:28:44 | 0:28:46 | |
is just the most beautiful thing that anyone can see. | 0:28:46 | 0:28:50 | |
Io is like Dante's Inferno, it's absolutely volcanoes everywhere. | 0:28:52 | 0:28:58 | |
Sulphur everywhere, hot lavas everywhere, | 0:29:00 | 0:29:04 | |
it is a volcanologist's paradise, | 0:29:04 | 0:29:07 | |
but it would be absolute hell if you were actually there. | 0:29:07 | 0:29:10 | |
Rosaly will measure the cooling rate of the lava here in Hawaii, | 0:29:18 | 0:29:22 | |
and then apply it to the volcanoes of Io. | 0:29:22 | 0:29:25 | |
In this way she hopes to find out if | 0:29:27 | 0:29:30 | |
Io has the especially hot ultramafic lava. | 0:29:30 | 0:29:33 | |
The team use a thermal camera. | 0:29:35 | 0:29:37 | |
-These should be nice images. -Very nice, very nice. | 0:29:39 | 0:29:42 | |
And then just really hot in the middle, | 0:29:42 | 0:29:44 | |
where that's cooling so fast. | 0:29:44 | 0:29:47 | |
That's beautiful, just spectacular. | 0:29:47 | 0:29:49 | |
The hottest lava is the moment it emerges. | 0:29:51 | 0:29:54 | |
If Jenny manages to break through the surface, | 0:29:55 | 0:29:58 | |
you are going to see the hot lava spilling out. | 0:29:58 | 0:30:02 | |
Oh, there we go. So that's the heart of the lava flow. | 0:30:02 | 0:30:07 | |
The thermal camera reveals how quickly | 0:30:08 | 0:30:12 | |
the lava cools here on Earth. | 0:30:12 | 0:30:13 | |
Even on the hottest parts, it was only about 910 Celsius. | 0:30:14 | 0:30:19 | |
The melting temperature of this rock is about 1,200 Celsius, | 0:30:19 | 0:30:24 | |
so that tells you that even in those red hot parts, the lava has cooled, | 0:30:24 | 0:30:30 | |
you know, more than a couple of hundred Celsius, | 0:30:30 | 0:30:33 | |
so lava cools very, very fast. | 0:30:33 | 0:30:36 | |
Rosaly suspects this also happens on Io. | 0:30:38 | 0:30:41 | |
Space probes to Io have revealed that the surface hot spots | 0:30:44 | 0:30:48 | |
are 1,200 degrees. | 0:30:48 | 0:30:50 | |
When we get measurements of the temperatures on Io, | 0:30:51 | 0:30:55 | |
we know that those temperatures likely have cooled | 0:30:55 | 0:30:58 | |
by at least a couple of hundred degrees Celsius. | 0:30:58 | 0:31:01 | |
It means the temperature of the lava just below the surface of Io | 0:31:03 | 0:31:08 | |
must be around 1,400 degrees. | 0:31:08 | 0:31:11 | |
Lava this hot is strong evidence it's ultramafic. | 0:31:13 | 0:31:17 | |
An exciting finding, | 0:31:24 | 0:31:26 | |
as it means Io could hold the secrets of the Earth's past. | 0:31:26 | 0:31:30 | |
Io is a model of the early Earth, | 0:31:34 | 0:31:36 | |
because the lavas on Io may be of the ultramafic type, | 0:31:36 | 0:31:42 | |
and those are lavas that are very hot, | 0:31:42 | 0:31:44 | |
very primitive and they erupted on Earth billions of years ago. | 0:31:44 | 0:31:48 | |
The more we research Io, | 0:31:53 | 0:31:55 | |
the more we find out what the Earth was like as it was forming - | 0:31:55 | 0:31:59 | |
the type of lava flows, the form of volcanism, | 0:31:59 | 0:32:02 | |
the tremendous density of volcanoes. | 0:32:02 | 0:32:05 | |
By studying Io, | 0:32:08 | 0:32:09 | |
we look at volcanism on a scale that has not happened on Earth | 0:32:09 | 0:32:14 | |
for billions of years. | 0:32:14 | 0:32:15 | |
So, Io reveals what primitive Earth was like... | 0:32:16 | 0:32:19 | |
..Dante's volcanic Inferno. | 0:32:22 | 0:32:25 | |
Volcanoes have played a key role | 0:32:34 | 0:32:36 | |
in the evolution of planets in another way - | 0:32:36 | 0:32:40 | |
by creating their atmosphere. | 0:32:40 | 0:32:41 | |
And the best way of looking at that | 0:32:44 | 0:32:46 | |
is the most extreme example of all - Venus. | 0:32:46 | 0:32:50 | |
The planet Venus is a very hot climate. | 0:32:51 | 0:32:53 | |
The atmosphere is dense | 0:32:53 | 0:32:56 | |
and its primary constituent is carbon dioxide. | 0:32:56 | 0:32:59 | |
It has the densest atmosphere anywhere in the solar system. | 0:33:04 | 0:33:08 | |
And one of the hottest. | 0:33:12 | 0:33:14 | |
This extreme atmosphere was almost certainly created by volcanism. | 0:33:16 | 0:33:21 | |
It pumps out these gases. | 0:33:23 | 0:33:25 | |
But the thick atmosphere | 0:33:27 | 0:33:29 | |
also hid what was happening on the planet's surface. | 0:33:29 | 0:33:32 | |
So, we really didn't have much of an idea of what was beneath those | 0:33:38 | 0:33:41 | |
clouds, and it was a bit of guesswork. | 0:33:41 | 0:33:43 | |
You know, you send the probes down, are they going to survive, | 0:33:43 | 0:33:45 | |
what's the atmospheric pressure going to be, how hot is it going to be? | 0:33:45 | 0:33:49 | |
So when the first probes went down onto the surface, | 0:33:50 | 0:33:52 | |
they didn't last very long. | 0:33:52 | 0:33:54 | |
But a new generation of probes, armed with radar, | 0:34:00 | 0:34:04 | |
eventually peered through the veil of Venus | 0:34:04 | 0:34:07 | |
to reveal an astonishing landscape. | 0:34:07 | 0:34:09 | |
More volcanic cones and craters | 0:34:12 | 0:34:14 | |
than any other planet of the solar system. | 0:34:14 | 0:34:17 | |
When they eventually got | 0:34:19 | 0:34:21 | |
the correct sort of radar going through the clouds | 0:34:21 | 0:34:23 | |
and seeing what was going on, then it got really exciting. | 0:34:23 | 0:34:26 | |
Then we thought, "This is a planet with a lot of volcanoes on it, | 0:34:26 | 0:34:29 | |
"and even more fascinating, | 0:34:29 | 0:34:31 | |
"volcanoes unlike any we see on the Earth." | 0:34:31 | 0:34:33 | |
These volcanoes are unique to Venus. | 0:34:34 | 0:34:37 | |
Some are 65km across, | 0:34:39 | 0:34:42 | |
surrounded by cliffs over 1000 metres high. | 0:34:42 | 0:34:46 | |
Almost perfectly circular, they're known as pancake domes. | 0:34:48 | 0:34:53 | |
The pancake domes were very much a mystery. | 0:34:54 | 0:34:55 | |
What we saw on the surface of Venus were just large, basically pancakes, | 0:34:55 | 0:35:00 | |
stuck on top of these flat plains. | 0:35:00 | 0:35:02 | |
It was just, "What are these things?" | 0:35:02 | 0:35:04 | |
They are so untypical of what else we saw on Venus, | 0:35:04 | 0:35:07 | |
and that's when people started thinking, "Well, the sort of lava flows on Earth, | 0:35:07 | 0:35:10 | |
"where we actually have these same features, | 0:35:10 | 0:35:12 | |
"and these lava flows we have in places like Iceland." | 0:35:12 | 0:35:15 | |
What could pancake domes tell us about volcanism on Earth? | 0:35:18 | 0:35:22 | |
These are the extraordinary lava flows at Torfajokull in Iceland. | 0:35:25 | 0:35:30 | |
They end in cliffs, | 0:35:34 | 0:35:36 | |
similar to the pancake domes, but on a smaller scale. | 0:35:36 | 0:35:39 | |
It's like walking across a mossy Venus, isn't it? | 0:35:39 | 0:35:43 | |
Dave and Ian have come here to discover | 0:35:45 | 0:35:47 | |
more about the lava that created these landscapes. | 0:35:47 | 0:35:51 | |
One of the things I want to do quite soon | 0:35:52 | 0:35:55 | |
is to find a nice piece of this lovely lava to hit with my hammer, | 0:35:55 | 0:36:00 | |
so we can have a good look at what's inside it. | 0:36:00 | 0:36:03 | |
I'm going to hit this bit here, OK? | 0:36:08 | 0:36:10 | |
It makes a lovely noise as well, doesn't it? | 0:36:18 | 0:36:20 | |
It does indeed. And a nice smell, actually. | 0:36:20 | 0:36:22 | |
I love the smell of rhyolite in the afternoon! | 0:36:22 | 0:36:25 | |
So, you can see lots of little white crystals actually aligned in that | 0:36:25 | 0:36:30 | |
particular direction. | 0:36:30 | 0:36:31 | |
These only line up when you've got something that's very, | 0:36:31 | 0:36:34 | |
very sticky, and forcing crystals | 0:36:34 | 0:36:36 | |
to actually line up in the one direction. | 0:36:36 | 0:36:39 | |
And in this case, I know these crystals tell me | 0:36:39 | 0:36:41 | |
this rock is very high in silica. | 0:36:41 | 0:36:43 | |
Silica thickens the lava, and Dave and Ian believe this was what | 0:36:46 | 0:36:50 | |
created the pancake domes of Venus. | 0:36:50 | 0:36:53 | |
It behaves differently from thin lava. | 0:36:55 | 0:36:58 | |
The most common type of lava we have in the solar system is basalt, | 0:37:01 | 0:37:05 | |
and the entire surface of the moon and the entire surface of Mars | 0:37:05 | 0:37:08 | |
is covered in basalt. | 0:37:08 | 0:37:10 | |
I'm going to illustrate that by using oil. | 0:37:10 | 0:37:13 | |
It spreads out where it wants to go, | 0:37:17 | 0:37:19 | |
beautiful little fingers coming down thin and fast. | 0:37:19 | 0:37:23 | |
However, in some parts of the Earth and these pancake domes on Venus, | 0:37:24 | 0:37:28 | |
which is very exciting, we have this much thicker lava flow and I'm going | 0:37:28 | 0:37:31 | |
to illustrate that with treacle, and let's see how that goes. | 0:37:31 | 0:37:35 | |
Beautiful. | 0:37:39 | 0:37:40 | |
See how slow and how thick it is? | 0:37:40 | 0:37:43 | |
That's exactly what we expect to see | 0:37:43 | 0:37:45 | |
when we have these thicker lava flows | 0:37:45 | 0:37:47 | |
that are much richer in silica. | 0:37:47 | 0:37:48 | |
The forward edge is very thick | 0:37:48 | 0:37:50 | |
because everything is getting compressed | 0:37:50 | 0:37:52 | |
and squeezed forward at that forward edge. | 0:37:52 | 0:37:54 | |
If this was a real lava flow, | 0:37:54 | 0:37:57 | |
you would actually see blocks falling off the front of it. | 0:37:57 | 0:38:00 | |
On this sort of surface that's sloping, | 0:38:00 | 0:38:02 | |
you will see something that looks a little elongate, | 0:38:02 | 0:38:04 | |
as we can see here. But if you pour it onto a perfectly flat surface, | 0:38:04 | 0:38:08 | |
you will get, basically, a pancake, a circular pancake. | 0:38:08 | 0:38:10 | |
It's utterly fascinating, | 0:38:22 | 0:38:23 | |
because until recently, I thought these planets | 0:38:23 | 0:38:26 | |
were very, very boring, just had basalt, | 0:38:26 | 0:38:28 | |
but having found this particular type of rock on Venus, | 0:38:28 | 0:38:32 | |
it excites me personally, | 0:38:32 | 0:38:33 | |
because I've been working on them for 30 years. | 0:38:33 | 0:38:35 | |
But are any volcanoes on Venus still active? | 0:38:37 | 0:38:40 | |
Some exciting circumstantial evidence has recently been discovered. | 0:38:42 | 0:38:46 | |
They found that Venus had hot spots within it that occurred over quite | 0:38:47 | 0:38:53 | |
a short time interval, and this was the first evidence we had of perhaps | 0:38:53 | 0:38:56 | |
something active on Venus. | 0:38:56 | 0:38:58 | |
This image of the planet's surface was taken on June 22nd 2008. | 0:39:01 | 0:39:07 | |
The hottest parts are yellow and red. | 0:39:07 | 0:39:10 | |
And the same area, just two days later. | 0:39:11 | 0:39:14 | |
The best explanation of these new hot spots is erupting lava. | 0:39:15 | 0:39:21 | |
We're also seeing unexplained spikes of sulphur in the atmosphere, | 0:39:21 | 0:39:26 | |
which are probably related to these bursts of hot activity | 0:39:26 | 0:39:28 | |
appearing on the surface. | 0:39:28 | 0:39:30 | |
That really is quite exciting, to actually see these. | 0:39:31 | 0:39:33 | |
It's these active volcanoes | 0:39:33 | 0:39:36 | |
that create the dense atmosphere of Venus. | 0:39:36 | 0:39:39 | |
But why haven't all the volcanoes of Earth led to a similar dense | 0:39:48 | 0:39:52 | |
and hostile atmosphere on our own planet? | 0:39:52 | 0:39:54 | |
Claire Cousins is an astrobiologist. | 0:40:06 | 0:40:09 | |
She's been coming to Iceland for ten years, | 0:40:09 | 0:40:12 | |
as this is the ideal place to find out | 0:40:12 | 0:40:15 | |
how volcanoes can help support life. | 0:40:15 | 0:40:17 | |
Claire and her colleagues | 0:40:20 | 0:40:21 | |
are tapping into the gases of a volcanic vent. | 0:40:21 | 0:40:24 | |
Oh, that's interesting. That looks good, that looks good. | 0:40:28 | 0:40:31 | |
Nice. | 0:40:31 | 0:40:33 | |
So what kind of volcanic gases do we typically get from these systems? | 0:40:35 | 0:40:39 | |
It's about 2% CO2, carbon dioxide. | 0:40:39 | 0:40:42 | |
About 1% H2S, hydrogen sulphide, | 0:40:42 | 0:40:45 | |
and all of the other gases are in trace amounts. | 0:40:45 | 0:40:48 | |
Many of these gases are highly toxic. | 0:40:49 | 0:40:52 | |
So, we wear these gas masks while we're sampling these volcanic gases | 0:40:54 | 0:41:00 | |
because they're what we call acidic gases, | 0:41:00 | 0:41:02 | |
so they're things like carbon dioxide or hydrogen sulphide, | 0:41:02 | 0:41:05 | |
and they're basically gases that we just don't want to be breathing in. | 0:41:05 | 0:41:08 | |
They're really poisonous. | 0:41:08 | 0:41:10 | |
But surprisingly, the most abundant gas is actually water vapour - | 0:41:13 | 0:41:18 | |
97% at this site. | 0:41:18 | 0:41:20 | |
Across the entire Earth, all these gases have a global effect. | 0:41:22 | 0:41:26 | |
Volcanoes, they're not just destructive processes. | 0:41:28 | 0:41:31 | |
In the long-term, especially, they produce a huge amount | 0:41:31 | 0:41:34 | |
of essential ingredients for life, basically. | 0:41:34 | 0:41:37 | |
Particularly water vapour, | 0:41:37 | 0:41:39 | |
we're just surrounded at the moment by all this | 0:41:39 | 0:41:41 | |
volcanic gas and the vast majority of it is water. | 0:41:41 | 0:41:43 | |
Earth's early atmosphere and oceans were created by volcanism, | 0:41:47 | 0:41:52 | |
pumping water and gas into the primeval sky. | 0:41:52 | 0:41:55 | |
But because the tectonic plates of the Earth | 0:41:57 | 0:42:00 | |
dragged so much of this water | 0:42:00 | 0:42:01 | |
and gases back inside the planet... | 0:42:01 | 0:42:03 | |
..the right amount of atmosphere remained up above | 0:42:05 | 0:42:09 | |
for life to evolve. | 0:42:09 | 0:42:10 | |
Through this whole process, | 0:42:13 | 0:42:14 | |
volcanoes actually deliver to the surface | 0:42:14 | 0:42:16 | |
of the planet many fundamental ingredients required by life. | 0:42:16 | 0:42:19 | |
In contrast, Venus, without plate tectonics, | 0:42:19 | 0:42:23 | |
pumped ever more gases into her atmosphere. | 0:42:23 | 0:42:26 | |
Over time, this dense atmosphere created a hell planet. | 0:42:28 | 0:42:32 | |
All life that we know of needs heat, | 0:42:39 | 0:42:42 | |
liquid water, and an energy-rich foodstuff. | 0:42:42 | 0:42:45 | |
On Earth, volcanoes provide all three. | 0:42:47 | 0:42:50 | |
If they can do this for life here, | 0:42:53 | 0:42:55 | |
volcanoes might support life beyond Earth. | 0:42:55 | 0:42:59 | |
At a volcanic hot spot in Iceland, | 0:43:01 | 0:43:04 | |
Claire is searching for unusual life forms that can survive here. | 0:43:04 | 0:43:07 | |
Our perspective of what's extreme is incredibly human-centric. | 0:43:14 | 0:43:19 | |
We think that living at, you know, 20 Celsius | 0:43:19 | 0:43:22 | |
in an oxygen-rich atmosphere is, | 0:43:22 | 0:43:24 | |
that's what we like, | 0:43:24 | 0:43:25 | |
and we see anything that's different to that as, you know, extreme. | 0:43:25 | 0:43:29 | |
But in reality, | 0:43:29 | 0:43:30 | |
that's just what we've evolved to live in, | 0:43:30 | 0:43:32 | |
and microbes that live in these | 0:43:32 | 0:43:34 | |
very hot or very acidic environments, | 0:43:34 | 0:43:36 | |
they've evolved to live here | 0:43:36 | 0:43:38 | |
and they wouldn't actually grow in our conditions. | 0:43:38 | 0:43:40 | |
Mars had very similar environments where volcanism met ice. | 0:43:45 | 0:43:49 | |
This makes it a good candidate for evidence of extraterrestrial life. | 0:43:51 | 0:43:55 | |
Iceland acts as a useful parallel, | 0:44:01 | 0:44:04 | |
and here Claire tests the water for sulphur, | 0:44:04 | 0:44:06 | |
which certain bacteria can feed on. | 0:44:06 | 0:44:08 | |
The intensity of the blue tells you | 0:44:11 | 0:44:13 | |
how much sulphide is dissolved in the water. | 0:44:13 | 0:44:16 | |
How much food there is for the microbes to eat. | 0:44:16 | 0:44:18 | |
And we also get microbes which actually store the sulphur inside | 0:44:18 | 0:44:24 | |
their cells for future use, | 0:44:24 | 0:44:25 | |
like packing a sandwich into your bag for later. | 0:44:25 | 0:44:28 | |
And they use that sulphur when | 0:44:28 | 0:44:29 | |
they can't find any sulphur in the environment. | 0:44:29 | 0:44:32 | |
She collects the microorganisms to study them more closely. | 0:44:36 | 0:44:40 | |
We can read the DNA of these microorganisms and, you know, | 0:44:41 | 0:44:45 | |
we can identify what they are, | 0:44:45 | 0:44:47 | |
we can see what genes they have, you know, for certain lifestyles. | 0:44:47 | 0:44:50 | |
Whether they can eat sulphur or not, for example. | 0:44:50 | 0:44:53 | |
And we can really get a handle on the microbiology of these sites. | 0:44:53 | 0:44:56 | |
Claire believes that life on Earth and possibly Mars | 0:44:56 | 0:45:00 | |
could have originated in a volcanic hot spot just like this. | 0:45:00 | 0:45:04 | |
But Mars is not the only planetary body | 0:45:07 | 0:45:10 | |
where volcanism is closely linked to ice. | 0:45:10 | 0:45:13 | |
Linda Spilker is head of the team that runs the Cassini probe that's | 0:45:28 | 0:45:32 | |
been exploring Saturn and her moons. | 0:45:32 | 0:45:35 | |
Linda is most interested in the moon called Enceladus. | 0:45:36 | 0:45:41 | |
Enceladus is only about 500km across, | 0:45:41 | 0:45:44 | |
and that's only about one seventh the size of our own moon. | 0:45:44 | 0:45:47 | |
And that tiny moon, we think, should have been frozen solid. | 0:45:47 | 0:45:51 | |
And if you look carefully, | 0:45:51 | 0:45:53 | |
you notice it doesn't look like our moon at all. | 0:45:53 | 0:45:56 | |
Our moon is covered with craters and it's dark, | 0:45:56 | 0:45:58 | |
but this is bright, icy white, and very few craters. | 0:45:58 | 0:46:01 | |
As the Cassini probe approached Enceladus, | 0:46:03 | 0:46:06 | |
Linda observed something never seen before on a planetary body. | 0:46:06 | 0:46:10 | |
If you look carefully, you can actually see individual geysers | 0:46:13 | 0:46:17 | |
coming up and shooting out into space. | 0:46:17 | 0:46:20 | |
And what a surprise. | 0:46:20 | 0:46:22 | |
Everyone was in awe and amazement to see this level of activity. | 0:46:22 | 0:46:26 | |
And we knew for the first time, this wasn't a dead moon. | 0:46:30 | 0:46:34 | |
Enceladus was an active world. | 0:46:34 | 0:46:37 | |
These eruptions are not molten rock. | 0:46:50 | 0:46:53 | |
They are geysers, water and ice, | 0:46:56 | 0:46:58 | |
fountaining over 700km into space. | 0:46:58 | 0:47:02 | |
It means that liquid water | 0:47:05 | 0:47:07 | |
deep below the surface is being forced upwards by heat. | 0:47:07 | 0:47:11 | |
The material erupts so high | 0:47:13 | 0:47:15 | |
that it's actually become part of Saturn's rings. | 0:47:15 | 0:47:19 | |
So, all along, visible evidence of volcanic activity | 0:47:23 | 0:47:28 | |
was present in the rings of Saturn, | 0:47:28 | 0:47:30 | |
but scientists hadn't even realised. | 0:47:30 | 0:47:33 | |
Coming out of the geysers, | 0:47:37 | 0:47:39 | |
there's water vapour, there's tiny particles. | 0:47:39 | 0:47:42 | |
If you'd stand near one of these cracks on Enceladus | 0:47:42 | 0:47:46 | |
and put out your hand, | 0:47:46 | 0:47:47 | |
it would almost be like it was snowing. | 0:47:47 | 0:47:49 | |
These tiny particles would fall back down. | 0:47:49 | 0:47:52 | |
And that's why there's no craters. | 0:47:52 | 0:47:54 | |
That these particles go and fill in with fresh snow, on Enceladus, | 0:47:54 | 0:47:59 | |
fill in all of the craters, | 0:47:59 | 0:48:01 | |
and so, some pieces of Enceladus' surface are only minutes old. | 0:48:01 | 0:48:06 | |
Covered by these tiny particles, falling in from space. | 0:48:06 | 0:48:10 | |
So, how are these extraordinary geysers of ice and water formed? | 0:48:11 | 0:48:16 | |
Again, Iceland provides a powerful analogy. | 0:48:21 | 0:48:24 | |
This is the Strokkur geyser. | 0:48:32 | 0:48:34 | |
Claire loves to witness its raw power. | 0:48:39 | 0:48:42 | |
A great natural wonder of the world. | 0:48:45 | 0:48:47 | |
So what we have here, | 0:48:50 | 0:48:51 | |
rather than molten lava coming out of the ground, | 0:48:51 | 0:48:54 | |
as you typically get for your regular volcano, | 0:48:54 | 0:48:57 | |
what we have here is actually just water, | 0:48:57 | 0:48:59 | |
just ground water which is within the ground. | 0:48:59 | 0:49:02 | |
And it's being heated up by these magma chambers, | 0:49:02 | 0:49:04 | |
which are actually much further, deeper underground. | 0:49:04 | 0:49:07 | |
And this water gets superheated | 0:49:07 | 0:49:09 | |
until it just can't stay underground any more, | 0:49:09 | 0:49:11 | |
and all that steam and all that energy, | 0:49:11 | 0:49:14 | |
just like in a normal volcano, | 0:49:14 | 0:49:15 | |
will erupt all of that water to the surface. | 0:49:15 | 0:49:17 | |
Just before the eruption, what we see is a kind of bubble forming, | 0:49:22 | 0:49:26 | |
where we get this really beautiful, | 0:49:26 | 0:49:28 | |
kind of almost glassy-looking dome of water, | 0:49:28 | 0:49:31 | |
which is all this superheated water just coming up to the surface | 0:49:31 | 0:49:35 | |
until it finally erupts. | 0:49:35 | 0:49:36 | |
A thermal camera measures the heat of the water. | 0:49:37 | 0:49:40 | |
What we can do when we look at the thermal camera here, | 0:49:42 | 0:49:45 | |
we can get an idea of how high temperature the system is. | 0:49:45 | 0:49:49 | |
It's about 70 Celsius. | 0:49:49 | 0:49:51 | |
For me, Enceladus is one of the most exciting places, I think, | 0:49:51 | 0:49:55 | |
in the solar system to go out and explore. It's... | 0:49:55 | 0:49:57 | |
LOUD WHOOSH | 0:49:57 | 0:49:59 | |
For reasons exactly like that, | 0:49:59 | 0:50:00 | |
it's one of the other places in the solar system where we actually have | 0:50:00 | 0:50:03 | |
this active hydrothermal activity, where we have these plumes which are | 0:50:03 | 0:50:08 | |
massive in scale compared to what we have here. | 0:50:08 | 0:50:10 | |
The geysers of Enceladus are so powerful, | 0:50:16 | 0:50:20 | |
there must be an ocean of heated water hidden below the icy surface. | 0:50:20 | 0:50:25 | |
Linda Spilker has ingeniously found out what's in this ocean. | 0:50:28 | 0:50:32 | |
The Cassini spacecraft, since we can get so close to Enceladus, | 0:50:34 | 0:50:39 | |
we can literally skim, fly through the jets and make measurements. | 0:50:39 | 0:50:44 | |
We can measure the gas, we can measure the particles coming out, | 0:50:44 | 0:50:48 | |
and figure out what they're made of. | 0:50:48 | 0:50:50 | |
And the clues inside those particles, those composition, | 0:50:50 | 0:50:54 | |
tells us about the ocean underneath. | 0:50:54 | 0:50:57 | |
It is full of salts and organic compounds. | 0:50:59 | 0:51:02 | |
Some of the key building blocks of life. | 0:51:02 | 0:51:05 | |
So, we wonder, could Enceladus also have life | 0:51:08 | 0:51:12 | |
very similar to the life on Earth? | 0:51:12 | 0:51:16 | |
Is it like the same kind of life we have here on Earth? | 0:51:16 | 0:51:19 | |
Is it something totally different that we can't imagine? | 0:51:19 | 0:51:22 | |
We've had volcanism on Mars, | 0:51:32 | 0:51:34 | |
we've had volcanism on Enceladus and its various different geysers. | 0:51:34 | 0:51:37 | |
To find evidence of life on another planet would be... | 0:51:37 | 0:51:40 | |
It would just be absolutely ground-breaking | 0:51:40 | 0:51:42 | |
in terms of our understanding | 0:51:42 | 0:51:44 | |
of our place, not just in the solar system, | 0:51:44 | 0:51:46 | |
but in the universe as well, right? | 0:51:46 | 0:51:48 | |
The hunt for volcanoes elsewhere | 0:51:52 | 0:51:54 | |
continues to produce amazing breakthroughs. | 0:51:54 | 0:51:57 | |
This is one of the remotest and most distant parts of the solar system. | 0:52:01 | 0:52:05 | |
Pluto. | 0:52:07 | 0:52:09 | |
After a nine-year odyssey, | 0:52:11 | 0:52:13 | |
the New Horizons probe finally reached Pluto in July 2015. | 0:52:13 | 0:52:18 | |
What it discovered was astonishing. | 0:52:21 | 0:52:24 | |
The New Horizons spacecraft that just visited Pluto | 0:52:26 | 0:52:29 | |
found features that have every indication of being cryovolcanic, | 0:52:29 | 0:52:33 | |
mountains, shield-like mountains, | 0:52:33 | 0:52:37 | |
flows on the surface. | 0:52:37 | 0:52:39 | |
Completely unexpected. | 0:52:39 | 0:52:41 | |
And just an extraordinary discovery | 0:52:41 | 0:52:43 | |
which just shows us how exciting the game can be. | 0:52:43 | 0:52:45 | |
This is Wright Mons on Pluto. | 0:52:47 | 0:52:50 | |
At 150km across, and 4km high, | 0:52:51 | 0:52:56 | |
it's believed to be the largest cryovolcano of the solar system. | 0:52:56 | 0:53:00 | |
It's driven by a similar process of mountain formation as on Earth, | 0:53:02 | 0:53:08 | |
but instead of molten rock, it's built up from flowing ice. | 0:53:08 | 0:53:12 | |
In the case of Pluto, it's so cold. | 0:53:15 | 0:53:18 | |
It's not water ice, | 0:53:18 | 0:53:20 | |
it's actually... can be nitrogen ice that can be there. | 0:53:20 | 0:53:22 | |
Or methane ice. | 0:53:22 | 0:53:24 | |
Other things that can be ice in that very cold environment of Pluto. | 0:53:24 | 0:53:28 | |
And there are some tantalising features | 0:53:28 | 0:53:30 | |
that perhaps are cryovolcanoes - maybe something has flowed out. | 0:53:30 | 0:53:33 | |
You mix a little bit of water and ammonia together and it can actually | 0:53:33 | 0:53:36 | |
flow on the surface. | 0:53:36 | 0:53:38 | |
A rare event on Earth called frazil ice | 0:53:40 | 0:53:44 | |
reveals how freezing water can sometimes behave | 0:53:44 | 0:53:47 | |
in a similar way to lava. | 0:53:47 | 0:53:49 | |
During winter, it's occasionally observed in Yosemite National Park. | 0:53:51 | 0:53:55 | |
A slowly flowing river of chunks of ice, given the right conditions, | 0:53:57 | 0:54:02 | |
suddenly freezes solid. | 0:54:02 | 0:54:05 | |
What happens when we see frazil ice on Earth, | 0:54:07 | 0:54:09 | |
is it is so close to its freezing point. | 0:54:09 | 0:54:11 | |
That's why it's filled with ice crystals. | 0:54:11 | 0:54:13 | |
And if it cools down just enough, just another half a degree Celsius, | 0:54:13 | 0:54:17 | |
a quarter of a degree Celsius, | 0:54:17 | 0:54:19 | |
suddenly all the water that's liquid between those ice crystals freezes, | 0:54:19 | 0:54:24 | |
and it happens just like that. | 0:54:24 | 0:54:25 | |
And it's entirely possible that that same process could be happening | 0:54:27 | 0:54:30 | |
on the surface of Pluto. | 0:54:30 | 0:54:32 | |
It's towards the end of the Iceland expedition, | 0:54:40 | 0:54:43 | |
and the team gather to discuss their findings. | 0:54:43 | 0:54:46 | |
Key to this is the fascinating paradox - | 0:54:50 | 0:54:53 | |
volcanoes are a violent and destructive force, | 0:54:53 | 0:54:57 | |
while also essential to life. | 0:54:57 | 0:54:59 | |
Whenever we find volcanism on Earth, | 0:55:02 | 0:55:03 | |
we find all sorts of kind of crazy chemistry, really, | 0:55:03 | 0:55:06 | |
which can just support microbial life, as it is on Earth. | 0:55:06 | 0:55:09 | |
And the real question is whether | 0:55:09 | 0:55:11 | |
these same kinds of processes that happen on Mars or on Enceladus, | 0:55:11 | 0:55:14 | |
whether those can actually support microbial life in the same way. | 0:55:14 | 0:55:17 | |
There's a lot of similarities between this type of environment, | 0:55:17 | 0:55:20 | |
that we've obviously got life in, we know that. | 0:55:20 | 0:55:23 | |
So this is the type of environment that would be a great target | 0:55:23 | 0:55:27 | |
-to look for on Mars. -Yeah. | 0:55:27 | 0:55:29 | |
But volcanoes of the solar system also give us a window | 0:55:33 | 0:55:38 | |
on what might happen to our own planet in the future. | 0:55:38 | 0:55:41 | |
What I think is really fascinating, | 0:55:43 | 0:55:45 | |
when you look throughout the solar system, | 0:55:45 | 0:55:47 | |
is that you have this diversity of bodies, and each of these bodies, | 0:55:47 | 0:55:52 | |
all of them, or most of them show volcanism. | 0:55:52 | 0:55:55 | |
And then you see that they have been developing in different ways, | 0:55:55 | 0:56:00 | |
each of the bodies. | 0:56:00 | 0:56:01 | |
In about a billion years, | 0:56:03 | 0:56:05 | |
it's predicted that the plate tectonics of Earth could end. | 0:56:05 | 0:56:10 | |
A catastrophe for life here. | 0:56:12 | 0:56:15 | |
Plate tectonics and volcanism replenish the atmosphere | 0:56:19 | 0:56:22 | |
with what we need, but won't you just lose the atmosphere | 0:56:22 | 0:56:25 | |
if you stop plate tectonics? | 0:56:25 | 0:56:27 | |
If Earth just literally kind of grinds to a halt, then, yeah, | 0:56:27 | 0:56:30 | |
eventually the atmosphere will be stripped away by the solar wind, | 0:56:30 | 0:56:34 | |
it will be just lost into space and, yeah, | 0:56:34 | 0:56:37 | |
basically I think we'll end up becoming very much like Mars, | 0:56:37 | 0:56:39 | |
just a very cold and dry, barren, rocky planet. | 0:56:39 | 0:56:42 | |
Earth as Mars is one option. | 0:56:45 | 0:56:48 | |
But another scenario is possible. | 0:56:50 | 0:56:52 | |
Even if plate tectonics ended, volcanism might continue unabated, | 0:56:56 | 0:57:03 | |
and our atmosphere would become thicker and hotter. | 0:57:03 | 0:57:07 | |
It could go the other way and end up like Venus, | 0:57:07 | 0:57:12 | |
where we have all this carbon dioxide in the atmosphere, | 0:57:12 | 0:57:14 | |
and, you know, either way, the options aren't looking that great. | 0:57:14 | 0:57:17 | |
So the interesting thing is | 0:57:17 | 0:57:19 | |
we've got these three planets next to each other, | 0:57:19 | 0:57:21 | |
and they've all got these incredibly different scenes at the present day, | 0:57:21 | 0:57:25 | |
that they may be telling us a lot about the potential futures for | 0:57:25 | 0:57:30 | |
the Earth, as well, and volcanoes are a big part of that story. | 0:57:30 | 0:57:34 | |
So you can see the higher life forms on Earth, like human beings, | 0:57:34 | 0:57:37 | |
dying out as the conditions become much more difficult for them. | 0:57:37 | 0:57:42 | |
Perhaps we'll lose our atmosphere, | 0:57:42 | 0:57:44 | |
perhaps actually we start losing our water. | 0:57:44 | 0:57:46 | |
It's going to be very difficult for human beings to adapt to those | 0:57:46 | 0:57:49 | |
-conditions, but the microbes will love them. -Yeah. | 0:57:49 | 0:57:51 | |
Microbes will inherit the Earth. | 0:57:51 | 0:57:54 | |
Fortunately, all this is a billion years from now. | 0:57:57 | 0:58:00 | |
Way back in the ninth century, Vikings discovered Iceland, | 0:58:03 | 0:58:07 | |
its landscape sculpted by volcanoes. | 0:58:07 | 0:58:10 | |
Today, a new generation of explorers are looking out into space, | 0:58:14 | 0:58:20 | |
discovering how volcanoes have shaped not just our planet, | 0:58:20 | 0:58:24 | |
but other extraordinary worlds. | 0:58:24 | 0:58:27 |