Space Volcanoes Horizon


Space Volcanoes

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The landscapes of Earth have been shaped by volcanoes.

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We've long been in awe of their destructive beauty.

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But only recently have we discovered that volcanism exists beyond Earth.

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The planets and moons of the solar system have volcanoes that are even

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more extraordinary than those on our home planet.

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Rivers of lava once raced across our moon.

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It's an amazing thought that you could have been standing on Earth

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and looked up at the moon, and seen these massive eruptions happening.

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The largest volcano of the solar system,

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three times the height of Everest, is on Mars.

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The most violent volcano is on a moon of Jupiter.

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Huge, icy geysers fountain out into space from a moon orbiting Saturn.

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We have not closed the book on volcanism across the solar system by any means.

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But what's most remarkable is what volcanic activity elsewhere in

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the solar system has told scientists about our own planet, Earth.

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What the Earth was like at its birth,

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why we have the geology and the atmosphere we do.

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And even how life on Earth, and possibly elsewhere, originated.

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Way back in the ninth century AD,

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a band of Vikings discovered Iceland.

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They experienced volcanic eruptions for the first time.

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To explain their devastation,

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they evoked the terrible wrath of gods such as Surtr, the fire giant.

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A Viking poet wrote, "In the beginning, all was cold and grim.

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"Then came Surtr with a crashing noise.

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"Bright and burning, he bore a flaming sword."

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A millennium later, and a team of international scientists has also

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travelled to the land of fire and ice.

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This small country has more types of

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volcanoes and geological wonders packed into it

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than anywhere else in the world.

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For the team, it allows them to compare the volcanism of Earth with

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volcanoes found elsewhere in the solar system.

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You've got these continual cycles of glaciers and volcanoes.

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Absolutely brilliant.

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Yeah, you have a really diverse range of volcanic features here,

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and I think it's a good place to see the importance of volcanism.

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For geologist Jim Head,

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Iceland is a familiar landscape.

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In the 1960s,

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he was teaching the Apollo astronauts all about rocks

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before they headed off to the moon.

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We took them everywhere we could

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that would give them geological information.

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Iceland was clearly one of those.

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And I think it's completely perfect, actually,

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that we are here today in Iceland, studying the volcanoes that

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actually propelled the astronauts to go to the moon.

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Five, four, three, two, one.

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The Apollo missions weren't just about the space race.

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They were also the most ambitious geological field trips of all time.

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A key aim was to discover if volcanoes

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had helped create the moon.

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And, if so, were any still active?

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Before the Apollo programme,

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we didn't even know whether the moon had volcanism.

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For example, some people thought it was a cold moon,

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some people thought it was a warm moon,

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which had heating inside and volcanism.

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So this is a big question - was it even volcanic rock?

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2,000 feet, 2,000 feet.

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47 degrees. Roger.

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These dark-looking plains of the moon

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were particularly tantalising to scientists.

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They're called the seas, or the maria.

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Beautiful view! Isn't that something?

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Magnificent desolation.

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To find out exactly what they were,

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the first Apollo landing was to Mare Tranquillitatis,

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the Sea of Tranquillity.

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OK, ready for me to come out?

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All set.

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As the astronauts explored the dusty and rocky surface,

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they recognised basalt - the most common volcanic rock found on Earth.

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And lots of it.

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When you erupt molten rock on a moon, liquid rock on the moon,

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it actually is one sixth gravity,

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so it's much less gravity than we see on the Earth.

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It looks like a collection of just about

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every variety of rock you could find.

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If the lava is coming up from great depths, given the gravity, etc,

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you'll get a lot of lava coming up,

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commonly much more than you see on the Earth,

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and so it flows great distances,

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and so we have lava flows that go over 1000 kilometres,

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like, incredible, it would go

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halfway across the United States, no problem.

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Another mysterious feature found on the moon

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was these winding canyons, or sinuous rilles.

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These channels were up to 400 metres deep and over 100km long.

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Clues as to what created them can be found back on Earth.

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Under the south-west of Iceland are curious tunnels through solid rock.

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They appear almost man-made.

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Gro Pedersen is exploring one.

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In the depths of the tunnel,

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she hopes to find evidence of what used to flow through it.

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You can actually see how the lava has been running along the wall here,

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and you can see also that it was very hot in here,

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because some of this lava re-melted,

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and basically was dribbling down the wall. You see that here.

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It's a lava tube and, long ago, lava was surging through these tunnels.

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One of the very exciting things people found on the moon

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was these sinuous rilles and,

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of course, before people actually had been on the moon,

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they were thought to potentially be water eroded.

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But then people have gone to the moon,

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and it has been studied much more and we've found out that these

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sinuous rilles were always connected with the maria,

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the moon lava that we have up there.

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Perhaps these sinuous rilles were once enclosed lava tubes.

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So one of the things that you see here, obviously,

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is that we have what we call skylights,

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so the roof has collapsed.

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If all of the roof collapses, you will end up with a valley,

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like something you see on the moon.

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But you can also see the tubes on the moon by a string of skylights,

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just as we see here, one hole after the other, and you just follow them,

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you trace them down and you can see that these are within lava flows.

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But when did these eruptions take place?

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And why did they eventually stop?

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The answer would come in small bags of volcanic rocks

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brought home by the astronauts.

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On Earth, they could be accurately dated.

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So when the moon rocks were brought back, it's, like, unbelievable.

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OK, this we can tell, four-billion-year-old rocks.

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These are the keys to the understanding of the solar system.

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Like other planetary bodies made of rock,

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the moon was a mass of hot molten magma as it was forming.

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It's an amazing thought that you could have been standing on Earth

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and looked up at the moon and seen these massive eruptions happening.

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But all the time, it was cooling -

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being relatively small, a quarter the diameter of the Earth,

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the moon cooled down quickly.

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By three billion years ago,

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almost all the lava and interior magma had solidified

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into one big lump of cold rock.

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No more volcanoes.

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But you see the remnants of it.

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I mean, when you look at the sky and you look at the moon,

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you see the evidence of the volcanism,

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because you see the dark areas, the basalt,

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which has filled in the craters.

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Understanding how the moon lost its volcanoes

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helps explain why Earth remains so active.

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Being larger allowed the Earth to retain much of its original heat.

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And so today, our planet is a dynamic and ever-changing world,

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rather than a dead one.

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So, the discovery on the moon of lava flows

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gave us pause to think about how this worked

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on other planetary bodies.

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How does volcanism work on Mars?

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So, the lunar exploration really opened up

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a field of, really, planetary volcanology.

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Exploring our neighbour, Mars,

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also reveals secrets about Earth's geology.

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When probes first reached the red planet,

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one feature stood out above swirling sandstorms.

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The volcano Olympus Mons.

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Olympus Mons is enormous, it's about 25km high.

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On Earth, you would be looking at something ridiculously high.

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Most commercial aircraft fly 10-15 kilometres.

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So you're looking at something that is towering way above

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what commercial aircraft might fly.

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Its base covers an area the size of France.

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It's three times the height of Mount Everest.

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Making it the largest volcano ever discovered in the solar system.

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Finding out how it grew to be so colossal

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tells scientists more about the volcanoes of Earth.

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That's why three of the team have come together to study this volcano.

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Icelanders call it Skjaldbreidur, which means "broad shield",

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as side on, it's reminiscent of a Viking shield.

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Although small in stature, it's of great significance.

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This shield volcano is the one over...

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about which all the other volcanoes of this type are called,

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in the solar system and on the Earth.

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So this is the first one, in many senses,

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the first one to be named the shield.

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It's only 1,000 metres high,

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a 25th the height of Olympus Mons,

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but crucially, it's the same type of shield volcano.

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At the summit is the crater.

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Wow, now you can see the crater.

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-Yeah.

-Fantastic.

-Wow!

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That's very nice.

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-I mean, you could even have come skiing up here.

-Oh, wow.

-Yeah.

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Then we can imagine, like, a lava lake.

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Yeah, just round the top.

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-Yeah.

-Dribbling over where we are now.

-Yeah.

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Around the rim are mysteriously-shaped rocks.

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They look almost like fossilised snakes.

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Yet they give a hint how this type of volcano forms,

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and what gives it the distinctive shield shape.

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This is a type of lava we call entrail,

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and it's a bit like the entrails from the inside of a human body

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or any animal body.

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They're characteristically quite thin.

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I mean, you can see from the shape of my hand,

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it's a couple of hand widths.

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Shield volcanoes comprise lavas that are very runny,

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because the shapes of them,

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this broad shield shape, tells us it has to have been.

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And we have the evidence in front of our eyes of these small tubes,

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these entrails running down the sides of the volcano,

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telling us that indeed, it had to be very runny.

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This fast-flowing lava creates

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the gentle slopes of all shield volcanoes,

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including the largest one of all, on Mars.

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But while shield volcanoes on Iceland

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have just one crater at the summit,

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Olympus Mons has six overlapping craters.

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That's the key. We actually can use what we see in Iceland to say,

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what we see in Mars is similar, but also different.

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It has to be much, much longer lived with multiple phases of eruptions

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to produce these multiple summit craters we see on Olympus Mons.

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When this behemoth erupted, Mars shuddered.

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Rivers of lava swept down the massive flanks of the volcano.

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But Earth is twice the size of Mars,

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so why don't we have volcanoes as enormous as Olympus Mons?

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It's all to do with plate tectonics.

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Earth is made up of seven huge plates

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drifting above a sea of magma.

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The circulation of magma recycles rocks and gases,

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bringing them to the surface and then back down again.

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Iceland is the perfect place to witness plate tectonics in action.

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This rift is where the North American plate, to the left,

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divides from its Eurasian cousin, to the right.

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The rift is widening rapidly, at over two centimetres a year.

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We've got the best evidence of plate tectonics we can find here.

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You can see the tension of the plates moving apart from each other.

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Yeah, this is the only planet that we know that's got plate tectonics.

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Mars, like all other planets we know of, has no active plate tectonics.

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The entire crust of Mars remains locked in place,

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with repercussions for its volcanoes.

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Any upwelling magma continually breaks through

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at one fixed location.

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On Mars, it's just centred, the same spot, for so long,

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building up a huge volcano.

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So it's a very focused eruption of magma for billions of years.

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And what happens is you just end up with a huge volcano,

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the biggest in the solar system.

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While Mars is no longer volcanically active,

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it does share an important feature with Earth - the polar ice caps.

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The story of these ice caps

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has been revealed through unusually shaped volcanoes.

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They have steep sides and a flat top like a table.

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Scientists now believe they might have been formed when volcanoes

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exploded through an ancient ice sheet.

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To understand how ice can change the behaviour of lava,

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scientists are carrying out an extreme experiment.

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For this, Ingo Sonder and Tracy Gregg need to make their own lava...

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..out of 50kg of basalt rock.

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We're turning it to its lava state,

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and the students have built a little ramp

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that the lava will pour down and pool at the end.

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And at the end of this lava stream, there will be a little pond of ice.

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So the lava's going to flow over the ice.

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We know this has happened on Earth.

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We think it's happened on Mars in the past.

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So we'll see what happens.

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The electrical furnace is running at 80,000 watts.

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By now, the molten rock is over 1,200 degrees Celsius.

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It's ready for the big pour.

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Look where it hits the ice, it's boiling!

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Because the ice is melting and it's flashing to steam.

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And it's creating all those bubbles there on the lava.

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Whoa! And now, this is what happens...

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..when the lava melts the ice and there's enough water,

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we're getting some little steam explosions.

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Right, there's no more lava coming out of the furnace.

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But underneath that black crust, it's still liquid,

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it's slowly flowing down.

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And you can see where it's ponded over the ice,

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there's some heaving going on as gas is trying to escape.

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The experiment lets Tracy identify

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key features as molten rock interacts with ice.

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When the lava hit the ice, a couple of things happened really fast.

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The lava started to bubble,

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as the ice melted and then flashed to steam.

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And then, as more melt occurred,

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there were actually puddles of water

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that started to boil and spatter just like

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on your stove, right, the water spattering.

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Where the ice wasn't, we have nice, neat, organised flows,

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folds in the lava.

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And right where the ice starts,

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we get these bigger bubbles on the surface.

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Look, that one's broken open, you can see inside.

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That's the kind of thing we could look for on Mars.

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Right? To see if there was any lava-ice interactions on Mars.

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Can you hear it?

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As the lava cools, it contracts,

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and it makes little pops like breakfast cereal.

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Pop, pop.

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Yep.

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That's amazing.

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The artificial volcano confirms that

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lava behaves very differently when it meets ice.

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But what happens out in the real world?

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One of the most distinctive types of volcano in Iceland is called a tuya.

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The team believe they can help explain the mountains

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with a similar shape on Mars.

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Wherever we see volcanoes that look like this,

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on Iceland we know that the ice has been there,

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and if we see the same sorts of volcanoes on Mars,

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we've got a good idea or a very good idea that there was ice present.

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There are two polar ice caps on Mars today.

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But millions of years ago,

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they were far more extensive.

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Mapping the tuyas on Mars reveals

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the coverage and depth of the ancient ice sheets.

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That's amazing, that you can actually say something about

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ice thickness in the past on a different planet,

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after the ice has gone.

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Which may have been three and a half billion years ago, as well.

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-Yeah.

-It's similar processes on different planets but it's yielding

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valuable information. It's telling us about what most planets...

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how they were evolving and what was happening at the time.

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Today, Mars and our own moon are cold and desolate planetary bodies.

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Geologically inert.

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While Earth has retained active volcanoes.

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To understand how we got here,

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we need to find out what Earth was like four billion years ago.

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And scientists think they've found the perfect place to look,

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a moon far out in the solar system.

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Ashley Davies is a top planetary volcanologist.

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He's fascinated by a moon of Jupiter called Io.

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One of the most important images that's ever been collected by any

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spacecraft was obtained by Voyager at Io.

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The image revealed this crescent rising above Io's surface,

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no-one knew quite what this was.

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Could it be another moon behind Io, or some artefact in the image?

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And then it was realised that this was actually a huge volcanic plume

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rising up from Io's surface.

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For me, this was

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an image that I think shaped the rest of my life,

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because from this point...

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I was a schoolboy and I realised this was a huge step in an unknown

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direction for astronomy and planetary science.

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And in a way, this actually put me on the path through school and into

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scientific research, and finally brought me here to study

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this absolutely astonishing little world.

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We now know that crammed into Io, the same size as our moon,

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are over 400 active volcanoes.

0:24:360:24:39

Compare this to just 60 on the whole of Earth.

0:24:410:24:45

The most powerful eruption was seen at a volcano called Surtr,

0:24:490:24:54

which is actually named after an Icelandic giant.

0:24:540:24:58

A fissure opened up and a huge volume of lava literally gushed out

0:24:580:25:03

of the ground to form large lava fountains kilometres high.

0:25:030:25:07

It must have been an absolutely incredible sight to see

0:25:070:25:10

if you were there to witness it, but not from too close by.

0:25:100:25:13

When Surtr roars,

0:25:140:25:16

it sends plumes of lava and ash over 500km into space.

0:25:160:25:22

Io proved for the first time

0:25:310:25:33

that Earth wasn't alone in having active volcanoes.

0:25:330:25:36

And, perhaps more importantly,

0:25:420:25:44

Io offered a clue as to the conditions

0:25:440:25:47

that existed as the Earth formed.

0:25:470:25:49

But first, scientists needed to discover

0:25:510:25:54

where the heat driving Io's volcanism came from.

0:25:540:25:57

The reason why Io is so active

0:25:590:26:02

is it's caught in this gravitational tug-of-war between Jupiter, Io,

0:26:020:26:09

Europa and Ganymede,

0:26:090:26:11

and this pumps a lot of energy into the system.

0:26:110:26:13

What happens to a squash ball is just like Io,

0:26:200:26:25

as it's pulled between gigantic Jupiter and her other moons.

0:26:250:26:30

A thermal camera reveals the temperature of the squash ball

0:26:320:26:36

as the rallies progress.

0:26:360:26:38

We hit the ball against the wall and it heated up.

0:26:390:26:44

And it heated up because it was being compressed,

0:26:460:26:48

twisted and turned.

0:26:480:26:50

And Io is very much like that.

0:26:510:26:54

With Io, it's being twisted and turned and squeezed by gravitational

0:26:550:27:00

forces, and the gravitational forces

0:27:000:27:03

cause a lot of interior heating and the heating manifests at the surface

0:27:030:27:07

as huge volcanoes.

0:27:070:27:09

Io heats up so much that it might erupt

0:27:130:27:16

an extremely rare and hot form of lava called ultramafic.

0:27:160:27:21

Ultramafic lava was abundant 4.5 billion years ago,

0:27:250:27:29

when the Earth formed,

0:27:290:27:33

but no longer.

0:27:330:27:34

To discover this primitive lava on Io

0:27:360:27:39

would offer scientists a window on the past.

0:27:390:27:42

Volcanologist Rosaly Lopes does her research in Hawaii.

0:27:520:27:57

We're studying volcanoes on Hawaii not because of Hawaii itself,

0:27:570:28:01

but because Hawaiian volcanoes are such a good analogue,

0:28:010:28:07

or a mirror if you like, for volcanoes on Jupiter's moon, Io.

0:28:070:28:11

And it's really understanding the volcanoes on Io

0:28:110:28:16

that we are after.

0:28:160:28:18

Hawaii has more active volcanoes than anywhere on Earth.

0:28:230:28:27

In fact, the islands are a chain of shield volcanoes,

0:28:290:28:33

built up from the ocean floor.

0:28:330:28:35

Rosaly looks for the most active lava flows.

0:28:360:28:39

It's challenging, it's beautiful.

0:28:410:28:44

I think a volcano in activity

0:28:440:28:46

is just the most beautiful thing that anyone can see.

0:28:460:28:50

Io is like Dante's Inferno, it's absolutely volcanoes everywhere.

0:28:520:28:58

Sulphur everywhere, hot lavas everywhere,

0:29:000:29:04

it is a volcanologist's paradise,

0:29:040:29:07

but it would be absolute hell if you were actually there.

0:29:070:29:10

Rosaly will measure the cooling rate of the lava here in Hawaii,

0:29:180:29:22

and then apply it to the volcanoes of Io.

0:29:220:29:25

In this way she hopes to find out if

0:29:270:29:30

Io has the especially hot ultramafic lava.

0:29:300:29:33

The team use a thermal camera.

0:29:350:29:37

-These should be nice images.

-Very nice, very nice.

0:29:390:29:42

And then just really hot in the middle,

0:29:420:29:44

where that's cooling so fast.

0:29:440:29:47

That's beautiful, just spectacular.

0:29:470:29:49

The hottest lava is the moment it emerges.

0:29:510:29:54

If Jenny manages to break through the surface,

0:29:550:29:58

you are going to see the hot lava spilling out.

0:29:580:30:02

Oh, there we go. So that's the heart of the lava flow.

0:30:020:30:07

The thermal camera reveals how quickly

0:30:080:30:12

the lava cools here on Earth.

0:30:120:30:13

Even on the hottest parts, it was only about 910 Celsius.

0:30:140:30:19

The melting temperature of this rock is about 1,200 Celsius,

0:30:190:30:24

so that tells you that even in those red hot parts, the lava has cooled,

0:30:240:30:30

you know, more than a couple of hundred Celsius,

0:30:300:30:33

so lava cools very, very fast.

0:30:330:30:36

Rosaly suspects this also happens on Io.

0:30:380:30:41

Space probes to Io have revealed that the surface hot spots

0:30:440:30:48

are 1,200 degrees.

0:30:480:30:50

When we get measurements of the temperatures on Io,

0:30:510:30:55

we know that those temperatures likely have cooled

0:30:550:30:58

by at least a couple of hundred degrees Celsius.

0:30:580:31:01

It means the temperature of the lava just below the surface of Io

0:31:030:31:08

must be around 1,400 degrees.

0:31:080:31:11

Lava this hot is strong evidence it's ultramafic.

0:31:130:31:17

An exciting finding,

0:31:240:31:26

as it means Io could hold the secrets of the Earth's past.

0:31:260:31:30

Io is a model of the early Earth,

0:31:340:31:36

because the lavas on Io may be of the ultramafic type,

0:31:360:31:42

and those are lavas that are very hot,

0:31:420:31:44

very primitive and they erupted on Earth billions of years ago.

0:31:440:31:48

The more we research Io,

0:31:530:31:55

the more we find out what the Earth was like as it was forming -

0:31:550:31:59

the type of lava flows, the form of volcanism,

0:31:590:32:02

the tremendous density of volcanoes.

0:32:020:32:05

By studying Io,

0:32:080:32:09

we look at volcanism on a scale that has not happened on Earth

0:32:090:32:14

for billions of years.

0:32:140:32:15

So, Io reveals what primitive Earth was like...

0:32:160:32:19

..Dante's volcanic Inferno.

0:32:220:32:25

Volcanoes have played a key role

0:32:340:32:36

in the evolution of planets in another way -

0:32:360:32:40

by creating their atmosphere.

0:32:400:32:41

And the best way of looking at that

0:32:440:32:46

is the most extreme example of all - Venus.

0:32:460:32:50

The planet Venus is a very hot climate.

0:32:510:32:53

The atmosphere is dense

0:32:530:32:56

and its primary constituent is carbon dioxide.

0:32:560:32:59

It has the densest atmosphere anywhere in the solar system.

0:33:040:33:08

And one of the hottest.

0:33:120:33:14

This extreme atmosphere was almost certainly created by volcanism.

0:33:160:33:21

It pumps out these gases.

0:33:230:33:25

But the thick atmosphere

0:33:270:33:29

also hid what was happening on the planet's surface.

0:33:290:33:32

So, we really didn't have much of an idea of what was beneath those

0:33:380:33:41

clouds, and it was a bit of guesswork.

0:33:410:33:43

You know, you send the probes down, are they going to survive,

0:33:430:33:45

what's the atmospheric pressure going to be, how hot is it going to be?

0:33:450:33:49

So when the first probes went down onto the surface,

0:33:500:33:52

they didn't last very long.

0:33:520:33:54

But a new generation of probes, armed with radar,

0:34:000:34:04

eventually peered through the veil of Venus

0:34:040:34:07

to reveal an astonishing landscape.

0:34:070:34:09

More volcanic cones and craters

0:34:120:34:14

than any other planet of the solar system.

0:34:140:34:17

When they eventually got

0:34:190:34:21

the correct sort of radar going through the clouds

0:34:210:34:23

and seeing what was going on, then it got really exciting.

0:34:230:34:26

Then we thought, "This is a planet with a lot of volcanoes on it,

0:34:260:34:29

"and even more fascinating,

0:34:290:34:31

"volcanoes unlike any we see on the Earth."

0:34:310:34:33

These volcanoes are unique to Venus.

0:34:340:34:37

Some are 65km across,

0:34:390:34:42

surrounded by cliffs over 1000 metres high.

0:34:420:34:46

Almost perfectly circular, they're known as pancake domes.

0:34:480:34:53

The pancake domes were very much a mystery.

0:34:540:34:55

What we saw on the surface of Venus were just large, basically pancakes,

0:34:550:35:00

stuck on top of these flat plains.

0:35:000:35:02

It was just, "What are these things?"

0:35:020:35:04

They are so untypical of what else we saw on Venus,

0:35:040:35:07

and that's when people started thinking, "Well, the sort of lava flows on Earth,

0:35:070:35:10

"where we actually have these same features,

0:35:100:35:12

"and these lava flows we have in places like Iceland."

0:35:120:35:15

What could pancake domes tell us about volcanism on Earth?

0:35:180:35:22

These are the extraordinary lava flows at Torfajokull in Iceland.

0:35:250:35:30

They end in cliffs,

0:35:340:35:36

similar to the pancake domes, but on a smaller scale.

0:35:360:35:39

It's like walking across a mossy Venus, isn't it?

0:35:390:35:43

Dave and Ian have come here to discover

0:35:450:35:47

more about the lava that created these landscapes.

0:35:470:35:51

One of the things I want to do quite soon

0:35:520:35:55

is to find a nice piece of this lovely lava to hit with my hammer,

0:35:550:36:00

so we can have a good look at what's inside it.

0:36:000:36:03

I'm going to hit this bit here, OK?

0:36:080:36:10

It makes a lovely noise as well, doesn't it?

0:36:180:36:20

It does indeed. And a nice smell, actually.

0:36:200:36:22

I love the smell of rhyolite in the afternoon!

0:36:220:36:25

So, you can see lots of little white crystals actually aligned in that

0:36:250:36:30

particular direction.

0:36:300:36:31

These only line up when you've got something that's very,

0:36:310:36:34

very sticky, and forcing crystals

0:36:340:36:36

to actually line up in the one direction.

0:36:360:36:39

And in this case, I know these crystals tell me

0:36:390:36:41

this rock is very high in silica.

0:36:410:36:43

Silica thickens the lava, and Dave and Ian believe this was what

0:36:460:36:50

created the pancake domes of Venus.

0:36:500:36:53

It behaves differently from thin lava.

0:36:550:36:58

The most common type of lava we have in the solar system is basalt,

0:37:010:37:05

and the entire surface of the moon and the entire surface of Mars

0:37:050:37:08

is covered in basalt.

0:37:080:37:10

I'm going to illustrate that by using oil.

0:37:100:37:13

It spreads out where it wants to go,

0:37:170:37:19

beautiful little fingers coming down thin and fast.

0:37:190:37:23

However, in some parts of the Earth and these pancake domes on Venus,

0:37:240:37:28

which is very exciting, we have this much thicker lava flow and I'm going

0:37:280:37:31

to illustrate that with treacle, and let's see how that goes.

0:37:310:37:35

Beautiful.

0:37:390:37:40

See how slow and how thick it is?

0:37:400:37:43

That's exactly what we expect to see

0:37:430:37:45

when we have these thicker lava flows

0:37:450:37:47

that are much richer in silica.

0:37:470:37:48

The forward edge is very thick

0:37:480:37:50

because everything is getting compressed

0:37:500:37:52

and squeezed forward at that forward edge.

0:37:520:37:54

If this was a real lava flow,

0:37:540:37:57

you would actually see blocks falling off the front of it.

0:37:570:38:00

On this sort of surface that's sloping,

0:38:000:38:02

you will see something that looks a little elongate,

0:38:020:38:04

as we can see here. But if you pour it onto a perfectly flat surface,

0:38:040:38:08

you will get, basically, a pancake, a circular pancake.

0:38:080:38:10

It's utterly fascinating,

0:38:220:38:23

because until recently, I thought these planets

0:38:230:38:26

were very, very boring, just had basalt,

0:38:260:38:28

but having found this particular type of rock on Venus,

0:38:280:38:32

it excites me personally,

0:38:320:38:33

because I've been working on them for 30 years.

0:38:330:38:35

But are any volcanoes on Venus still active?

0:38:370:38:40

Some exciting circumstantial evidence has recently been discovered.

0:38:420:38:46

They found that Venus had hot spots within it that occurred over quite

0:38:470:38:53

a short time interval, and this was the first evidence we had of perhaps

0:38:530:38:56

something active on Venus.

0:38:560:38:58

This image of the planet's surface was taken on June 22nd 2008.

0:39:010:39:07

The hottest parts are yellow and red.

0:39:070:39:10

And the same area, just two days later.

0:39:110:39:14

The best explanation of these new hot spots is erupting lava.

0:39:150:39:21

We're also seeing unexplained spikes of sulphur in the atmosphere,

0:39:210:39:26

which are probably related to these bursts of hot activity

0:39:260:39:28

appearing on the surface.

0:39:280:39:30

That really is quite exciting, to actually see these.

0:39:310:39:33

It's these active volcanoes

0:39:330:39:36

that create the dense atmosphere of Venus.

0:39:360:39:39

But why haven't all the volcanoes of Earth led to a similar dense

0:39:480:39:52

and hostile atmosphere on our own planet?

0:39:520:39:54

Claire Cousins is an astrobiologist.

0:40:060:40:09

She's been coming to Iceland for ten years,

0:40:090:40:12

as this is the ideal place to find out

0:40:120:40:15

how volcanoes can help support life.

0:40:150:40:17

Claire and her colleagues

0:40:200:40:21

are tapping into the gases of a volcanic vent.

0:40:210:40:24

Oh, that's interesting. That looks good, that looks good.

0:40:280:40:31

Nice.

0:40:310:40:33

So what kind of volcanic gases do we typically get from these systems?

0:40:350:40:39

It's about 2% CO2, carbon dioxide.

0:40:390:40:42

About 1% H2S, hydrogen sulphide,

0:40:420:40:45

and all of the other gases are in trace amounts.

0:40:450:40:48

Many of these gases are highly toxic.

0:40:490:40:52

So, we wear these gas masks while we're sampling these volcanic gases

0:40:540:41:00

because they're what we call acidic gases,

0:41:000:41:02

so they're things like carbon dioxide or hydrogen sulphide,

0:41:020:41:05

and they're basically gases that we just don't want to be breathing in.

0:41:050:41:08

They're really poisonous.

0:41:080:41:10

But surprisingly, the most abundant gas is actually water vapour -

0:41:130:41:18

97% at this site.

0:41:180:41:20

Across the entire Earth, all these gases have a global effect.

0:41:220:41:26

Volcanoes, they're not just destructive processes.

0:41:280:41:31

In the long-term, especially, they produce a huge amount

0:41:310:41:34

of essential ingredients for life, basically.

0:41:340:41:37

Particularly water vapour,

0:41:370:41:39

we're just surrounded at the moment by all this

0:41:390:41:41

volcanic gas and the vast majority of it is water.

0:41:410:41:43

Earth's early atmosphere and oceans were created by volcanism,

0:41:470:41:52

pumping water and gas into the primeval sky.

0:41:520:41:55

But because the tectonic plates of the Earth

0:41:570:42:00

dragged so much of this water

0:42:000:42:01

and gases back inside the planet...

0:42:010:42:03

..the right amount of atmosphere remained up above

0:42:050:42:09

for life to evolve.

0:42:090:42:10

Through this whole process,

0:42:130:42:14

volcanoes actually deliver to the surface

0:42:140:42:16

of the planet many fundamental ingredients required by life.

0:42:160:42:19

In contrast, Venus, without plate tectonics,

0:42:190:42:23

pumped ever more gases into her atmosphere.

0:42:230:42:26

Over time, this dense atmosphere created a hell planet.

0:42:280:42:32

All life that we know of needs heat,

0:42:390:42:42

liquid water, and an energy-rich foodstuff.

0:42:420:42:45

On Earth, volcanoes provide all three.

0:42:470:42:50

If they can do this for life here,

0:42:530:42:55

volcanoes might support life beyond Earth.

0:42:550:42:59

At a volcanic hot spot in Iceland,

0:43:010:43:04

Claire is searching for unusual life forms that can survive here.

0:43:040:43:07

Our perspective of what's extreme is incredibly human-centric.

0:43:140:43:19

We think that living at, you know, 20 Celsius

0:43:190:43:22

in an oxygen-rich atmosphere is,

0:43:220:43:24

that's what we like,

0:43:240:43:25

and we see anything that's different to that as, you know, extreme.

0:43:250:43:29

But in reality,

0:43:290:43:30

that's just what we've evolved to live in,

0:43:300:43:32

and microbes that live in these

0:43:320:43:34

very hot or very acidic environments,

0:43:340:43:36

they've evolved to live here

0:43:360:43:38

and they wouldn't actually grow in our conditions.

0:43:380:43:40

Mars had very similar environments where volcanism met ice.

0:43:450:43:49

This makes it a good candidate for evidence of extraterrestrial life.

0:43:510:43:55

Iceland acts as a useful parallel,

0:44:010:44:04

and here Claire tests the water for sulphur,

0:44:040:44:06

which certain bacteria can feed on.

0:44:060:44:08

The intensity of the blue tells you

0:44:110:44:13

how much sulphide is dissolved in the water.

0:44:130:44:16

How much food there is for the microbes to eat.

0:44:160:44:18

And we also get microbes which actually store the sulphur inside

0:44:180:44:24

their cells for future use,

0:44:240:44:25

like packing a sandwich into your bag for later.

0:44:250:44:28

And they use that sulphur when

0:44:280:44:29

they can't find any sulphur in the environment.

0:44:290:44:32

She collects the microorganisms to study them more closely.

0:44:360:44:40

We can read the DNA of these microorganisms and, you know,

0:44:410:44:45

we can identify what they are,

0:44:450:44:47

we can see what genes they have, you know, for certain lifestyles.

0:44:470:44:50

Whether they can eat sulphur or not, for example.

0:44:500:44:53

And we can really get a handle on the microbiology of these sites.

0:44:530:44:56

Claire believes that life on Earth and possibly Mars

0:44:560:45:00

could have originated in a volcanic hot spot just like this.

0:45:000:45:04

But Mars is not the only planetary body

0:45:070:45:10

where volcanism is closely linked to ice.

0:45:100:45:13

Linda Spilker is head of the team that runs the Cassini probe that's

0:45:280:45:32

been exploring Saturn and her moons.

0:45:320:45:35

Linda is most interested in the moon called Enceladus.

0:45:360:45:41

Enceladus is only about 500km across,

0:45:410:45:44

and that's only about one seventh the size of our own moon.

0:45:440:45:47

And that tiny moon, we think, should have been frozen solid.

0:45:470:45:51

And if you look carefully,

0:45:510:45:53

you notice it doesn't look like our moon at all.

0:45:530:45:56

Our moon is covered with craters and it's dark,

0:45:560:45:58

but this is bright, icy white, and very few craters.

0:45:580:46:01

As the Cassini probe approached Enceladus,

0:46:030:46:06

Linda observed something never seen before on a planetary body.

0:46:060:46:10

If you look carefully, you can actually see individual geysers

0:46:130:46:17

coming up and shooting out into space.

0:46:170:46:20

And what a surprise.

0:46:200:46:22

Everyone was in awe and amazement to see this level of activity.

0:46:220:46:26

And we knew for the first time, this wasn't a dead moon.

0:46:300:46:34

Enceladus was an active world.

0:46:340:46:37

These eruptions are not molten rock.

0:46:500:46:53

They are geysers, water and ice,

0:46:560:46:58

fountaining over 700km into space.

0:46:580:47:02

It means that liquid water

0:47:050:47:07

deep below the surface is being forced upwards by heat.

0:47:070:47:11

The material erupts so high

0:47:130:47:15

that it's actually become part of Saturn's rings.

0:47:150:47:19

So, all along, visible evidence of volcanic activity

0:47:230:47:28

was present in the rings of Saturn,

0:47:280:47:30

but scientists hadn't even realised.

0:47:300:47:33

Coming out of the geysers,

0:47:370:47:39

there's water vapour, there's tiny particles.

0:47:390:47:42

If you'd stand near one of these cracks on Enceladus

0:47:420:47:46

and put out your hand,

0:47:460:47:47

it would almost be like it was snowing.

0:47:470:47:49

These tiny particles would fall back down.

0:47:490:47:52

And that's why there's no craters.

0:47:520:47:54

That these particles go and fill in with fresh snow, on Enceladus,

0:47:540:47:59

fill in all of the craters,

0:47:590:48:01

and so, some pieces of Enceladus' surface are only minutes old.

0:48:010:48:06

Covered by these tiny particles, falling in from space.

0:48:060:48:10

So, how are these extraordinary geysers of ice and water formed?

0:48:110:48:16

Again, Iceland provides a powerful analogy.

0:48:210:48:24

This is the Strokkur geyser.

0:48:320:48:34

Claire loves to witness its raw power.

0:48:390:48:42

A great natural wonder of the world.

0:48:450:48:47

So what we have here,

0:48:500:48:51

rather than molten lava coming out of the ground,

0:48:510:48:54

as you typically get for your regular volcano,

0:48:540:48:57

what we have here is actually just water,

0:48:570:48:59

just ground water which is within the ground.

0:48:590:49:02

And it's being heated up by these magma chambers,

0:49:020:49:04

which are actually much further, deeper underground.

0:49:040:49:07

And this water gets superheated

0:49:070:49:09

until it just can't stay underground any more,

0:49:090:49:11

and all that steam and all that energy,

0:49:110:49:14

just like in a normal volcano,

0:49:140:49:15

will erupt all of that water to the surface.

0:49:150:49:17

Just before the eruption, what we see is a kind of bubble forming,

0:49:220:49:26

where we get this really beautiful,

0:49:260:49:28

kind of almost glassy-looking dome of water,

0:49:280:49:31

which is all this superheated water just coming up to the surface

0:49:310:49:35

until it finally erupts.

0:49:350:49:36

A thermal camera measures the heat of the water.

0:49:370:49:40

What we can do when we look at the thermal camera here,

0:49:420:49:45

we can get an idea of how high temperature the system is.

0:49:450:49:49

It's about 70 Celsius.

0:49:490:49:51

For me, Enceladus is one of the most exciting places, I think,

0:49:510:49:55

in the solar system to go out and explore. It's...

0:49:550:49:57

LOUD WHOOSH

0:49:570:49:59

For reasons exactly like that,

0:49:590:50:00

it's one of the other places in the solar system where we actually have

0:50:000:50:03

this active hydrothermal activity, where we have these plumes which are

0:50:030:50:08

massive in scale compared to what we have here.

0:50:080:50:10

The geysers of Enceladus are so powerful,

0:50:160:50:20

there must be an ocean of heated water hidden below the icy surface.

0:50:200:50:25

Linda Spilker has ingeniously found out what's in this ocean.

0:50:280:50:32

The Cassini spacecraft, since we can get so close to Enceladus,

0:50:340:50:39

we can literally skim, fly through the jets and make measurements.

0:50:390:50:44

We can measure the gas, we can measure the particles coming out,

0:50:440:50:48

and figure out what they're made of.

0:50:480:50:50

And the clues inside those particles, those composition,

0:50:500:50:54

tells us about the ocean underneath.

0:50:540:50:57

It is full of salts and organic compounds.

0:50:590:51:02

Some of the key building blocks of life.

0:51:020:51:05

So, we wonder, could Enceladus also have life

0:51:080:51:12

very similar to the life on Earth?

0:51:120:51:16

Is it like the same kind of life we have here on Earth?

0:51:160:51:19

Is it something totally different that we can't imagine?

0:51:190:51:22

We've had volcanism on Mars,

0:51:320:51:34

we've had volcanism on Enceladus and its various different geysers.

0:51:340:51:37

To find evidence of life on another planet would be...

0:51:370:51:40

It would just be absolutely ground-breaking

0:51:400:51:42

in terms of our understanding

0:51:420:51:44

of our place, not just in the solar system,

0:51:440:51:46

but in the universe as well, right?

0:51:460:51:48

The hunt for volcanoes elsewhere

0:51:520:51:54

continues to produce amazing breakthroughs.

0:51:540:51:57

This is one of the remotest and most distant parts of the solar system.

0:52:010:52:05

Pluto.

0:52:070:52:09

After a nine-year odyssey,

0:52:110:52:13

the New Horizons probe finally reached Pluto in July 2015.

0:52:130:52:18

What it discovered was astonishing.

0:52:210:52:24

The New Horizons spacecraft that just visited Pluto

0:52:260:52:29

found features that have every indication of being cryovolcanic,

0:52:290:52:33

mountains, shield-like mountains,

0:52:330:52:37

flows on the surface.

0:52:370:52:39

Completely unexpected.

0:52:390:52:41

And just an extraordinary discovery

0:52:410:52:43

which just shows us how exciting the game can be.

0:52:430:52:45

This is Wright Mons on Pluto.

0:52:470:52:50

At 150km across, and 4km high,

0:52:510:52:56

it's believed to be the largest cryovolcano of the solar system.

0:52:560:53:00

It's driven by a similar process of mountain formation as on Earth,

0:53:020:53:08

but instead of molten rock, it's built up from flowing ice.

0:53:080:53:12

In the case of Pluto, it's so cold.

0:53:150:53:18

It's not water ice,

0:53:180:53:20

it's actually... can be nitrogen ice that can be there.

0:53:200:53:22

Or methane ice.

0:53:220:53:24

Other things that can be ice in that very cold environment of Pluto.

0:53:240:53:28

And there are some tantalising features

0:53:280:53:30

that perhaps are cryovolcanoes - maybe something has flowed out.

0:53:300:53:33

You mix a little bit of water and ammonia together and it can actually

0:53:330:53:36

flow on the surface.

0:53:360:53:38

A rare event on Earth called frazil ice

0:53:400:53:44

reveals how freezing water can sometimes behave

0:53:440:53:47

in a similar way to lava.

0:53:470:53:49

During winter, it's occasionally observed in Yosemite National Park.

0:53:510:53:55

A slowly flowing river of chunks of ice, given the right conditions,

0:53:570:54:02

suddenly freezes solid.

0:54:020:54:05

What happens when we see frazil ice on Earth,

0:54:070:54:09

is it is so close to its freezing point.

0:54:090:54:11

That's why it's filled with ice crystals.

0:54:110:54:13

And if it cools down just enough, just another half a degree Celsius,

0:54:130:54:17

a quarter of a degree Celsius,

0:54:170:54:19

suddenly all the water that's liquid between those ice crystals freezes,

0:54:190:54:24

and it happens just like that.

0:54:240:54:25

And it's entirely possible that that same process could be happening

0:54:270:54:30

on the surface of Pluto.

0:54:300:54:32

It's towards the end of the Iceland expedition,

0:54:400:54:43

and the team gather to discuss their findings.

0:54:430:54:46

Key to this is the fascinating paradox -

0:54:500:54:53

volcanoes are a violent and destructive force,

0:54:530:54:57

while also essential to life.

0:54:570:54:59

Whenever we find volcanism on Earth,

0:55:020:55:03

we find all sorts of kind of crazy chemistry, really,

0:55:030:55:06

which can just support microbial life, as it is on Earth.

0:55:060:55:09

And the real question is whether

0:55:090:55:11

these same kinds of processes that happen on Mars or on Enceladus,

0:55:110:55:14

whether those can actually support microbial life in the same way.

0:55:140:55:17

There's a lot of similarities between this type of environment,

0:55:170:55:20

that we've obviously got life in, we know that.

0:55:200:55:23

So this is the type of environment that would be a great target

0:55:230:55:27

-to look for on Mars.

-Yeah.

0:55:270:55:29

But volcanoes of the solar system also give us a window

0:55:330:55:38

on what might happen to our own planet in the future.

0:55:380:55:41

What I think is really fascinating,

0:55:430:55:45

when you look throughout the solar system,

0:55:450:55:47

is that you have this diversity of bodies, and each of these bodies,

0:55:470:55:52

all of them, or most of them show volcanism.

0:55:520:55:55

And then you see that they have been developing in different ways,

0:55:550:56:00

each of the bodies.

0:56:000:56:01

In about a billion years,

0:56:030:56:05

it's predicted that the plate tectonics of Earth could end.

0:56:050:56:10

A catastrophe for life here.

0:56:120:56:15

Plate tectonics and volcanism replenish the atmosphere

0:56:190:56:22

with what we need, but won't you just lose the atmosphere

0:56:220:56:25

if you stop plate tectonics?

0:56:250:56:27

If Earth just literally kind of grinds to a halt, then, yeah,

0:56:270:56:30

eventually the atmosphere will be stripped away by the solar wind,

0:56:300:56:34

it will be just lost into space and, yeah,

0:56:340:56:37

basically I think we'll end up becoming very much like Mars,

0:56:370:56:39

just a very cold and dry, barren, rocky planet.

0:56:390:56:42

Earth as Mars is one option.

0:56:450:56:48

But another scenario is possible.

0:56:500:56:52

Even if plate tectonics ended, volcanism might continue unabated,

0:56:560:57:03

and our atmosphere would become thicker and hotter.

0:57:030:57:07

It could go the other way and end up like Venus,

0:57:070:57:12

where we have all this carbon dioxide in the atmosphere,

0:57:120:57:14

and, you know, either way, the options aren't looking that great.

0:57:140:57:17

So the interesting thing is

0:57:170:57:19

we've got these three planets next to each other,

0:57:190:57:21

and they've all got these incredibly different scenes at the present day,

0:57:210:57:25

that they may be telling us a lot about the potential futures for

0:57:250:57:30

the Earth, as well, and volcanoes are a big part of that story.

0:57:300:57:34

So you can see the higher life forms on Earth, like human beings,

0:57:340:57:37

dying out as the conditions become much more difficult for them.

0:57:370:57:42

Perhaps we'll lose our atmosphere,

0:57:420:57:44

perhaps actually we start losing our water.

0:57:440:57:46

It's going to be very difficult for human beings to adapt to those

0:57:460:57:49

-conditions, but the microbes will love them.

-Yeah.

0:57:490:57:51

Microbes will inherit the Earth.

0:57:510:57:54

Fortunately, all this is a billion years from now.

0:57:570:58:00

Way back in the ninth century, Vikings discovered Iceland,

0:58:030:58:07

its landscape sculpted by volcanoes.

0:58:070:58:10

Today, a new generation of explorers are looking out into space,

0:58:140:58:20

discovering how volcanoes have shaped not just our planet,

0:58:200:58:24

but other extraordinary worlds.

0:58:240:58:27

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