Aliens Wonders of the Solar System


Aliens

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We live on a world of wonders.

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A place of astonishing beauty and complexity.

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There are vast oceans and incredible weather.

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Giant mountains

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and stunning landscapes.

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I'm a physicist, and I'm fascinated by the way that the universal laws of nature

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that made all this, also created such diverse and different worlds

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out there in the solar system.

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I think we're living through the greatest age of discovery our civilisation has known.

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We've voyaged to the farthest reaches of the solar system.

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We've photographed strange new worlds,

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stood in unfamiliar landscapes, tasted alien air.

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But the one thing we haven't found on those worlds

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is the thing that makes our planet unique.

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Life.

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But is that really true?

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Is the Earth the only place in the solar system that could support life?

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In this film we will search the solar system for worlds that harbour the conditions to support life.

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What we find on these worlds may help us answer the question, are we alone in the universe?

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That's not only one of the great fundamental questions for science,

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but one of the great unanswered questions in human history.

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Floating in the Sea of Cortez off the cost of Mexico is the research vessel Atlantis,

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the mother ship for the exploration of one of the most alien worlds we know.

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But it's an alien world on our planet.

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The Atlantis is the launch vessel for Alvin,

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one of the world's most rugged submarines.

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Built like a spacecraft,

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it's designed to explore the deepest depths of the ocean.

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And I'm lucky enough to have hitched a ride down to the sea floor,

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two kilometres beneath the surface.

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That has got to be the closest thing to going into space that you can do.

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And, given that I'm not going to go into space any time soon, I think it's the next best thing.

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See you in eight hours.

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Roger, Alvin. Your checks are good. Permission to dive.

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Roger. Alvin diving.

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The parallels to spaceflight are obvious.

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As the tiny capsule descends, we are leaving the familiar world

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of the surface of our planet, and entering a strange, hostile world.

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If anything goes wrong, we will be completely on our own.

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MACHINE BEEPS

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Beeping is never good.

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'Fortunately, Alvin is one of only a handful of submarines

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'that can withstand the colossal pressure of the deep ocean.'

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At the Earth's surface, we're used to one atmosphere of pressure.

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As we descend, the pressure increases by another atmosphere every ten metres.

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And it soon adds up.

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We're approaching a kilometre deep. The pressure outside there is now

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100 atmospheres, that's higher than the atmospheric pressure on the surface of Venus.

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Without knowing, if you were asked a question, could life exist down here, 100 atmospheres,

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cold, dark no sign of sunlight at all,

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it's pitch black there, you would say no.

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Well, I would say no.

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But the depths of the ocean are not lifeless.

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Illuminated by Alvin's lights,

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we find oases of life in the deserts of the ocean floor.

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So we have landed, after about an hour of descent.

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We've just stopped in the most incredible place.

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Look at those.

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We've landed on top of the tube worms.

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Amazing things.

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This underwater city is one of the most bizarre environments on our planet.

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It's built around a hydrothermal vent, a volcanic opening in the Earth's crust

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that pumps out clouds of sulphurous chemicals and water heated to nearly 300 Celsius.

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And somehow, life has found a way to thrive in these most extreme conditions.

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This is a genuinely remarkable place.

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There are mats,

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carpets of yellow bacteria.

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Look at that. It's not only just bacterial blobs,

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there is real complex organisms.

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Alien. I want to say that word, alien environment.

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It really is alien to us.

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For me, the fascinating thing about finding life down here

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is that the conditions on the

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deep ocean floor are more similar in many ways to the conditions on

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worlds hundreds of millions of kilometres away out there

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in the solar system than they are to the conditions just two kilometres from my head on the Earth's surface.

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It's incredibly dark, there is no sunlight,

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there's a brutal mixture of hot and cold water,

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and just rock and minerals.

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So, if life can not only survive but even flourish in these conditions,

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then you've got to feel that it's much more likely that life can

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also survive and flourish out there in the solar system.

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Ever since the invention of the telescope 400 years ago,

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we have looked to our neighbouring worlds for signs of life.

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As technology has improved, we've been able to search the planets in more and more detail,

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and we have found nothing.

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But that doesn't mean the rest of the solar system is dead,

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because we're only beginning to scratch the surface of what's out there.

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There are literally hundreds of other worlds.

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Planets and their moons which we have barely explored.

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Among them may be worlds that hold the conditions to support life.

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And the best way to find out what those conditions are

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is to look at the one place we know life flourishes.

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The Earth.

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Life is pretty much only chemistry.

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It's just the reactions between atoms and molecules.

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And so for life to exist, you only really need three things.

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First of all, you need the right chemistry set.

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Now, I'm made of something like 40 elements,

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almost half of the known elements, which is pretty complicated.

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But actually 96% of me is only made of four of them, carbon, nitrogen, oxygen and hydrogen.

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Secondly, you need a power source.

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You need a battery, something to make a flow of electrons

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that powers the processes of life.

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Now here on Earth, most life uses the power of the sun.

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And thirdly, you need some kind of medium for life to play itself out in,

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for processes to happen.

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And here on Earth,

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you don't have to look very far at all to find that medium, that solvent.

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Because it's this, water.

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If you want to see how important water is to life,

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there's no better place to come than the Atacama desert in Chile.

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The soil here is more sterile than a hospital operating theatre.

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In fact, scientists have looked for the most basic form of life, bacteria,

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in some parts of the Atacama, and they found absolutely nothing.

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All deserts are characterised by a lack of moisture.

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But the Atacama takes that to the extremes.

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The Sahara is 50 times wetter than the Atacama.

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There are weather stations here that have measured 1mm of rainfall in 10 years.

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There are river valleys that have been dry for 120,000 years.

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There are rocks that haven't seen rainfall for 20 million years.

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It's this dryness that explains why nothing can survive here.

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Even the most primitive form of life on Earth, the bacteria,

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need water for their survival.

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And there are no exceptions.

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And this seemingly fundamental link between water and life

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is driving the search for life out there in the solar system.

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Because, wherever we find water,

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that will be the best place to look for life beyond the Earth.

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The Earth is the only planet that currently has liquid water on its surface.

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The other planets are either too close to the sun,

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like Mercury, and baked dry.

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Or they are too far away.

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Saturn's rings are made of water, but in the depths of space, it's frozen into lumps of solid ice.

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But that doesn't mean that liquid water has never existed elsewhere in the solar system.

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And if it has, we should be able to find the evidence,

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because wherever water goes, it leaves its footprints.

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These are the Scablands, a remote part of the North Western United States.

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It's one of the most spectacular places to come to see how water

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carves its signature into the landscape.

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The largest flood on Earth went through this area here.

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Jim Rice is an astro-geologist. He believes that understanding the events that created this landscape

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can help in the search for water on other planets.

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We are kind of like CSI arriving at the scene of a crime, this is the evidence left here.

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-We've come to piece it together.

-I can see this is not a normal river system.

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You can see, because it is so straight.

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There is no meandering of a river here, it's just a big hole.

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This entire landscape was created at the end of the last Ice Age.

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200 miles to the east lay a huge lake, held in place by a wall of glacial ice.

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When that wall ruptured, over 2,000 cubic kilometres of water swept out in a single catastrophic event.

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The flood waters were at least 400 feet deep here.

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But actually they were another 200 feet stacked on top of that, coming across here.

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So we would be under 200 feet of water standing right here.

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So am I to imagine a wave?

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Yeah, a massive wave rolling, rumbling, this water would

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be charged full of big chunks of ice from that ice dam.

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It would be loaded with big chunks of the salt bed rock being gouged, ripped out of here.

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It would be an impressive sight.

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As the floodwaters tore across the landscape, they carved out this 20 mile long canyon.

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And at its head, it left these giant horseshoes.

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At over 400 feet high and five miles across,

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this was the largest waterfall the world has ever known.

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The easiest way of thinking about it is if you took every river in the world, put them in

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the same location, had them flowing at the same time, these floods are 10 times larger than that.

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And how long do we think it took to sculpt this landscape?

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48 hours to a week.

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It's instantaneous, geologically.

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The Scablands reveal the characteristic signature

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that water carves into the landscape.

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It's a signature that can be seen from space, and not just on the Earth.

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When we turn our telescopes on our next door neighbour and prime candidate for finding

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alien life, the planet Mars,

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we find almost identical features cut into its surface.

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The Red Planet is covered in outflow channels.

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Straight, wide canyons, exactly like the Scablands.

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And they are filled with identical geological features.

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It all suggests that similar huge floods once tore across the surface of Mars.

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This is a picture of here from the air.

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I am sat somewhere around here.

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And here are the horseshoe shapes of the dry folds which are just over there.

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This is a picture taken of the surface of Mars,

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and you see those typical horseshoe shapes of the folds.

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Also, you see the structures upstream of the folds, these grooves cut into the landscape.

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And you see that here, grooves cut into the landscape as the water

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cascades down and then flows over the folds

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and cuts the gigantic valleys out as it moves downstream.

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So, all this adds up, I think, to an overwhelming smoking gun

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that there were vast amounts of water that flowed very quickly

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over the surface of Mars at some point in the past.

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But although the outflow channels are proof that liquid water once flowed across Mars,

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it may not point to the existence of life.

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Because if the Martian landscapes were formed by the same processes that formed the Scablands on Earth,

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the floods that created them may only have lasted a matter of days.

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For life to get a foothold, you need more than that.

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You need areas of standing water.

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Lakes and rivers that persist for millions of years.

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In order to look for evidence of that standing water, we've done the only thing we can,

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we have sent an army of robotic explorers to the surface of the planet.

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We have touch down, we have touch down.

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Over the last 35 years,

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we've landed six robot probes on Mars.

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And one of them, Opportunity, is still rolling across the surface, investigating the Martian geology.

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The Mars rovers has really captured our imaginations.

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I suppose, because they genuinely are explorers in the old-fashioned sense.

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They are the extension of our senses to the surface of another world.

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But they have also been very important scientifically, because

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you can't really get to know another planet from orbit.

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You have got to get down to the surface, you've got to touch it,

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you've got to dig down and examine it microscopically.

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And the Rovers really have, by doing that,

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made some extremely important scientific discoveries.

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One of the most significant of those discoveries was made in November 2004.

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The Opportunity rover was examining an impact feature called the Endurance crater,

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when it detected deposits of a remarkable mineral.

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This is the world's largest salt works on the Baha peninsula in Mexico.

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And what they do here is pump sea water into these lagoons and let it evaporate.

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What they're after is this stuff, which is sodium chloride, table salt.

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But, at different stages, different salts, different minerals, crystallise out.

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So all the things really that are in sea water emerge, crystallise out

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at different stages of the process.

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In one of the lagoons, pond number nine, the sea water is at exactly the right concentration

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to precipitate out these beautiful crystals that cover the entire floor of the lagoon.

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This is gypsum,

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and it's exactly the same stuff that Opportunity found on the surface of Mars.

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Now, what's interesting about that discovery is how you make gypsum.

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You see, its chemical formula is CaSO4.

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So it's calcium sulphate.

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Dihydrate, 2H2O.

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That's water.

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So, the only way we know of, the only way to make gypsum here on Earth, is to have calcium

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and sulphate ions in the presence of liquid water.

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So, large deposits of gypsum on the surface of Mars tells you

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that there must have been big areas of water present for a very long time.

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The discovery of gypsum has helped to build a picture

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of an ancient Mars that was much warmer and wetter.

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Subsequent discoveries of gypsum in networks of sand dunes

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suggest that large areas of Mars were once covered in standing water.

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And where there is standing water, there is the chance of life.

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This area of the salt flats is, we think,

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very similar to areas that have been seen on Mars.

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And it certainly looks extremely inhospitable.

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It's hard at first sight to see how anything could live here.

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But, if you just dig

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a tiny bit below the surface,

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then you see that this layer of gypsum is only a few millimetres thick,

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and then immediately the ground beneath it turns this greeny colour.

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It's green because that is bacteria that thrive in these seemingly inhospitable conditions.

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Now if these bacteria can survive here,

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then there seems to be no good reason why they couldn't also have survived and even flourished on Mars

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when there was water present at some point in the very distant past.

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But although it may once have been more hospitable,

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any liquid water has long since disappeared from the surface of Mars.

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About three billion years ago, it died as a planet.

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Its core froze and the volcanoes that had produced its atmosphere seized up.

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The solar wind stripped away the remains of that atmosphere.

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Any liquid water would have evaporated

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or soaked into the soil where it froze.

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It left the surface of Mars too cold, too exposed

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and too dry to support life.

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It's highly unlikely that there will be life on the surface of Mars today.

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But that's not to say that life couldn't exist somewhere on the Red Planet,

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maybe we're just looking in the wrong place.

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There are other potential habitats for life on Mars.

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Detailed pictures of the surface show the entrances to caves,

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revealing the existence of a world beneath the Martian surface.

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We know there may be water down there.

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Satellite data shows permafrost, ice frozen in the soil.

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Deep below the surface, that ice may melt to form liquid water.

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It all hints at an undiscovered subterranean world

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that may be a more likely place to find life.

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If you were to imagine the perfect habitat for life,

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then it would surely be somewhere like this.

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A warm climate, lots of liquid water,

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a beautiful, dense atmosphere.

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You see the results everywhere, just life everywhere you look.

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All the life we're familiar with thrives in pretty much the same

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conditions that we do, driven by the heat and light of the sun.

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But this is by no means the only life on Earth.

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There's another living planet hidden beneath the surface

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that exists in completely different conditions.

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It raises fascinating possibilities for the caves on Mars.

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This is the Cueva de Villa Luz in Tabasco, Mexico,

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the Cave of the House of Light.

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And it is the definition of a hostile environment to me.

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Because (HE SNIFFS) it's full of hydrogen sulphide gas, hence

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the gas monitor which says at the moment one part per million hydrogen sulphide, very toxic for me,

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which is why I have got this gas mask in case it all gets too much.

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So, it's a place where you, at first sight,

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would not expect a great many life forms to survive and flourish.

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Although the cave is a death-trap for us, that doesn't mean that nothing lives here.

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In fact, it's teeming with life.

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Look at these fish, just everywhere in the cave water. And they're

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adapted to live in these conditions.

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In fact, if you look at them closely,

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they're quite pink.

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That's thought to be because they've got lots of haemoglobin

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because there's not much oxygen down here,

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so they need to have an efficient way of moving oxygen around their bodies.

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Beautiful.

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But the really interesting life is found in the depths of the caves,

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where the concentration of poisonous gas is high enough to set off my alarm.

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Down here, far from the light of the sun,

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are organisms whose energy source comes from the air around them.

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They use the hydrogen sulphide gas bubbling up through these springs.

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The same gas that could be fatally poisonous to me

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is their source of life.

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These things are what I came deep underground to see.

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These are snottites. And you can see why they're called that.

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They're really one of the most alien life forms that I can conceive of

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on the Earth

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Because they metabolise hydrogen sulphide, so they metabolise this

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faintly acidic and nasty gas that I'm just breathing in now.

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You can almost feel it on your tongue, actually, the acidity of it.

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They metabolise it, they react it with oxygen, and they produce sulphuric acid.

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So their breathing process, if you like, their version of what I do,

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I breathe in oxygen, react that with sugars and breathe out CO2 and get energy

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these guys breathe in hydrogen sulphide and oxygen and produce sulphuric acid.

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In fact, I can test it here with this.

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Yes, you see, look at that.

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That, well, what looks like water, that secretion of dripping off the snottites, has actually got a pH...

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well, it's now about between 0.5 and 0.

0:32:240:32:29

That's strong acid.

0:32:290:32:30

That's as strong as battery acid.

0:32:300:32:33

It's actually highly concentrated sulphuric acid.

0:32:330:32:37

So, what a strange organism.

0:32:370:32:41

Alien in every sense of the word.

0:32:410:32:43

Except that it's present on, well, just below the surface, of our planet.

0:32:430:32:48

And the snottites are not alone.

0:32:520:32:55

Organisms that can extract energy from the minerals around them

0:32:550:32:59

are found under the ground all over the world.

0:32:590:33:01

In fact, this way of life is so successful that it's thought there

0:33:030:33:08

may be more life living beneath the Earth's surface than there is on it.

0:33:080:33:13

And that raises an intriguing possibility.

0:33:150:33:18

If life can thrive below the Earth's surface,

0:33:180:33:22

why couldn't organisms like snottites survive and flourish

0:33:220:33:27

beneath the surface of Mars?

0:33:270:33:29

If you think about it, living below the surface of Mars might actually

0:33:330:33:37

be quite a good idea, because the surface is incredibly hostile.

0:33:370:33:41

It's subjected to intense ultraviolet radiation from the sun.

0:33:410:33:45

It's a very cold place, and the atmospheric pressure doesn't

0:33:450:33:48

allow liquid water to exist on the surface.

0:33:480:33:52

But, if there is life below the surface of Mars, then obviously we have a problem.

0:33:520:33:57

How could you possibly detect it?

0:33:570:33:59

Well, actually, there is a perhaps tantalising clue that

0:33:590:34:03

there might be something interesting going on below the Martian surface.

0:34:030:34:10

These are termites, or white ants.

0:34:210:34:25

And they're very unusual animals because they eat wood.

0:34:250:34:31

This is their food.

0:34:310:34:33

There are many, many species of these, billions of individuals across the planet.

0:34:330:34:40

And, in the process of digesting wood, they produce the gas methane.

0:34:400:34:45

Because there are so many of them, they actually produce an estimated

0:34:450:34:49

50 million tonnes of methane

0:34:490:34:51

and pump it into the Earth's atmosphere every year.

0:34:510:34:56

And it's not just termites.

0:34:560:34:59

There's lots of methane naturally in our atmosphere.

0:34:590:35:03

It's all produced either biologically...

0:35:030:35:06

or by active geological processes like mud volcanoes.

0:35:080:35:13

And that makes it all the more surprising that methane

0:35:190:35:22

has been detected in the atmosphere of the supposedly dead planet Mars.

0:35:220:35:28

It was telescopes on Earth, using infrared spectroscopy,

0:35:320:35:37

that first identified methane in Mars's tenuous atmosphere.

0:35:370:35:41

Those first measurements appeared to show only tiny amounts.

0:35:460:35:51

But closer observations have revealed that the gas

0:35:510:35:55

is concentrated in a handful of plumes that vary with the seasons.

0:35:550:36:01

In the warmer summer months,

0:36:020:36:04

thousands of tonnes of the gas is released from vents in the surface.

0:36:040:36:10

Something under the surface of Mars must be producing it.

0:36:100:36:15

It may be coming from previously unknown geological processes.

0:36:150:36:20

But it could be that it's coming from a biological source.

0:36:230:36:27

Now no-one, I don't think, is seriously suggesting that there

0:36:280:36:32

are termites running around beneath the surface of Mars.

0:36:320:36:36

But it's not actually the termites that are particularly interesting about this story.

0:36:360:36:41

It's the way they digest the wood.

0:36:410:36:44

You see, they use symbiotic bacteria, bacteria that live in their guts, called Archaea.

0:36:440:36:50

And Archaea, these bacteria that can digest wood and produce methane,

0:36:500:36:56

are the most common organisms beneath the surface of the Earth.

0:36:560:37:01

The snottites are members of the Archaea,

0:37:030:37:08

as are many of the microorganisms found living around deep-sea hydrothermal vents.

0:37:080:37:16

In fact, it's Archaea that we find thriving in many of the Earth's most extreme environments.

0:37:160:37:23

So I think it's quite a fascinating prospect that the methane we see

0:37:260:37:32

in Mars's atmosphere might just be produced by organisms like Archaea,

0:37:320:37:39

living below the Martian surface.

0:37:390:37:42

But while Mars remains a tantalising possibility,

0:37:440:37:48

it's no longer the only place in the solar system

0:37:480:37:52

we think could harbour alien life.

0:37:520:37:54

Far out, a billion kilometres from the sun,

0:38:000:38:04

the solar system becomes a very different place.

0:38:040:38:08

The planets, like Saturn, are made of gas, not rock.

0:38:100:38:14

There's plenty of water out here, but it's frozen solid.

0:38:180:38:21

The planets are surrounded by networks of moons, carved from ice.

0:38:240:38:30

They're cold and desolate.

0:38:300:38:33

They don't seem likely places to find life.

0:38:350:38:40

Any places on Earth remotely similar are completely barren.

0:38:400:38:45

This is central Iceland.

0:39:040:39:06

And, at this time of year, in mid-November, it's an increasingly inhospitable place.

0:39:060:39:12

It's about 3 o'clock in the afternoon, it's already well below freezing.

0:39:120:39:16

The sun is dipping below the horizon.

0:39:160:39:19

And it will stay this way for another six months.

0:39:190:39:22

And there's pretty much no visible life here at all.

0:39:220:39:29

There are no trees, no grass, and just listen.

0:39:290:39:34

SILENCE

0:39:340:39:36

No insects, no birds.

0:39:380:39:41

Nothing.

0:39:410:39:43

But it's because these places are so cold and inhospitable

0:39:470:39:51

that they're of increasing interest to astro-biologists.

0:39:510:39:55

Because discoveries in these frozen places of Earth have raised new hope

0:39:570:40:01

of finding life among the icy worlds of the outer solar system.

0:40:010:40:07

And in those frozen wastes

0:40:090:40:11

we have found one world that is of particular interest.

0:40:110:40:15

It's one of Jupiter's moons.

0:40:160:40:18

Jupiter has a vast network of moons.

0:40:250:40:29

The four largest have been known

0:40:290:40:32

since they were discovered by Galileo in 1610.

0:40:320:40:36

And they're a varied bunch.

0:40:360:40:38

Closest to the planet is the tortured moon Io.

0:40:410:40:45

It's torn apart by volcanoes that carpet its surface with bright yellow sulphur.

0:40:450:40:52

In total contrast to the heat of Io comes its neighbour,

0:40:580:41:03

the ice moon Europa.

0:41:030:41:06

It's about the same size as our moon.

0:41:090:41:13

And it's the smoothest body in the solar system.

0:41:130:41:16

Its surface is made of an unbroken shell of ice.

0:41:190:41:25

Though it's etched with a network of mysterious red markings.

0:41:250:41:30

It exists at a chilly minus 160 Celsius.

0:41:340:41:39

It seems an incredibly unlikely home for life.

0:41:390:41:43

The photographs of Europa from space

0:41:500:41:54

reveal a vast, icy wilderness.

0:41:540:41:59

But, if you look more closely, then you start to see surface features.

0:42:000:42:06

And those features tell you a lot about what's going on deep beneath the ice.

0:42:060:42:13

Close-up, we can see deep cracks that criss-cross the surface of Europa.

0:42:210:42:26

At higher magnification

0:42:300:42:32

we see areas where the ice has been broken into icebergs

0:42:320:42:36

and jumbled up before refreezing.

0:42:360:42:39

We see the same formations in sea ice on Earth,

0:42:420:42:46

where the movements of the ocean have caused the ice to bend and crack.

0:42:460:42:51

It suggests something similar may be happening on Europa.

0:42:530:42:57

But it's the way the cracks are broken and fractured that provide

0:42:590:43:03

the compelling evidence that there is liquid water on Europa.

0:43:030:43:08

You see, as Europa orbits around Jupiter,

0:43:120:43:15

Jupiter's intense gravity stretches and squashes the moon.

0:43:150:43:20

And that stresses the ice and causes it to fracture and crack.

0:43:200:43:25

But the position of those cracks is not quite where you would expect it to be.

0:43:250:43:30

And the explanation for that is that the icy surface of Europa

0:43:300:43:35

has shifted, it's moved relative to the rocky core.

0:43:350:43:39

And the only way that could happen is if there's a layer, or an ocean of liquid water,

0:43:390:43:46

surrounding the rocky core that allows the outer ice surface to slip around.

0:43:460:43:52

Measurements of Europa's magnetic field have confirmed that its icy shell

0:43:560:44:01

is sitting on top of a salty ocean that may be a staggering 100km deep.

0:44:010:44:09

That would mean that there is more than twice as much life-giving

0:44:240:44:28

liquid water on this tiny moon than there is on planet Earth.

0:44:280:44:34

But it's not just the discovery of the hidden ocean

0:44:380:44:41

that makes us believe that Europa may be the most likely home to alien life.

0:44:410:44:47

And that's why I've come to this spectacular ice cave in the Vatnajokull glacier.

0:44:480:44:55

You see, the laws of nature are universal.

0:44:550:44:58

That may not only apply to laws of physics, but also to the laws of biology as well.

0:44:580:45:03

And if that's the case,

0:45:030:45:05

then what we find in these ice caves of Iceland may tell us something

0:45:050:45:11

about what we could expect to find below the frozen surface of Europa.

0:45:110:45:16

It's hard to describe this place.

0:45:420:45:45

It's absolutely magnificent.

0:45:470:45:50

Visually, the quality of the ice, it's just completely

0:45:500:45:55

transparent and clear.

0:45:550:45:58

You can see straight through it.

0:45:580:46:01

The cave tunnels into the heart of the glacier,

0:46:030:46:07

where the ice has been frozen for a thousand years.

0:46:070:46:12

It's what astro-biologists find in this ice

0:46:120:46:16

that makes us think that Europa could be teeming with life.

0:46:160:46:22

NASA scientist Richard Hoover

0:46:300:46:33

has spent his career looking for life in unlikely places.

0:46:330:46:37

Well, that went very well.

0:46:400:46:42

-OK.

-So, will any organisms that you find in that ice be living in a sense that I would understand it?

0:46:440:46:50

They're actually alive now, and metabolising?

0:46:500:46:53

For a long time it was thought that ice microorganisms

0:46:530:46:59

were present only in a state of what is called deep anabiosis.

0:46:590:47:03

Suspended animation. It's now becoming quite clear that that isn't necessarily

0:47:030:47:08

the case for all the microorganisms, there may be others that are actually actively living in the ice.

0:47:080:47:15

So in this glacier, the whole place, this whole cave

0:47:150:47:19

may be populated by living things, not frozen things?

0:47:190:47:24

Things existing, living, cell dividing, reproducing, all the things you do?

0:47:240:47:29

All of this.

0:47:290:47:30

It's this prospect of finding things living in solid ice

0:47:360:47:40

that has had the greatest impact

0:47:400:47:42

on our ideas of where life could survive in the solar system.

0:47:420:47:47

OK, we're at lowest magnification.

0:47:490:47:51

So, that is 100,000 millionths of a metre?

0:47:510:47:53

Yes. We have bacteria.

0:47:530:47:57

So, these are organisms that have been trapped in that glacier for thousands of years?

0:47:590:48:04

Yes, look at this.

0:48:040:48:06

Beautiful. You're seeing life in ice.

0:48:060:48:09

We now know that some microorganisms

0:48:090:48:13

are capable of actually causing the ice to melt,

0:48:130:48:18

because they generate, essentially, anti-freeze proteins.

0:48:180:48:23

They change the temperature at which ice goes from a solid state to a liquid state.

0:48:230:48:29

And they could have been forming little tiny pockets,

0:48:290:48:32

maybe only a few microns in diameter,

0:48:320:48:34

but if he can make a two or three micron diameter ball of liquid water,

0:48:340:48:39

and he has the ability to move,

0:48:390:48:41

then that bacterium is now not in a glacier, but he's in an ocean.

0:48:410:48:47

What are the implications of these discoveries?

0:48:470:48:51

The fact that you've got living bacteria inside ice on Earth, what are the implications for Europa?

0:48:510:48:58

You can clearly have bacteria like this in the frozen ice near the surface crust.

0:48:580:49:04

And the thing that is most exciting to me,

0:49:040:49:07

is that surface crust of Europa has a wide variety of colours

0:49:070:49:12

that are highly suggestive of microbial life.

0:49:120:49:16

And so there is a very, very strong possibility

0:49:160:49:21

that the ice of Europa may contain viable, living microorganisms.

0:49:210:49:26

It's a controversial idea, but it is a dizzying thought

0:49:300:49:35

that the mysterious red stains on the surface of Europa

0:49:350:49:39

could be the visible signs of alien life.

0:49:390:49:44

The discovery of the huge ocean of liquid water

0:49:490:49:53

under the surface of this tiny moon, combined with the potential for life in ice,

0:49:530:49:59

and the intriguing red markings that criss-cross its surface,

0:49:590:50:04

have made Europa the most fascinating and important alien world we know.

0:50:040:50:10

A true wonder of the solar system,

0:50:200:50:23

because it's our best hope of finding extraterrestrial life.

0:50:230:50:29

That question, are we alone in the universe?

0:50:470:50:50

Is this the only planet amongst the billions of planets in our galaxy,

0:50:500:50:57

amongst the billions of galaxies in the universe, that harbours life?

0:50:570:51:02

Is, I think, one of the most important questions,

0:51:020:51:07

perhaps THE most important question that we can ask.

0:51:070:51:10

Think about what it would mean for us

0:51:100:51:13

if the answer was that there was no other life in the solar system,

0:51:130:51:18

in our galaxy, perhaps even in the universe.

0:51:180:51:21

How valuable would that make planet Earth?

0:51:210:51:25

How valuable would that make us?

0:51:250:51:27

But then imagine that the answer is that, on every moon of every planet

0:51:270:51:33

where the conditions are right, then life survives and flourishes.

0:51:330:51:38

That makes us part of a wider cosmic community,

0:51:380:51:43

if the universe is teeming with life.

0:51:430:51:47

If knowing the answer to the question is so profoundly important,

0:51:480:51:53

then surely striving to find the answer should be of overwhelming importance.

0:51:530:51:59

I believe it's the most important question you can possibly ask.

0:51:590:52:03

Because we have a chance of answering it.

0:52:030:52:06

What we've learned from the extreme places on Earth

0:52:210:52:24

is that, if there is life out there in the solar system, it will almost certainly be simple.

0:52:240:52:30

Single-celled organisms like bacteria eking out an existence in the most hostile of environments.

0:52:300:52:38

One thing seems certain.

0:52:500:52:52

The only place in the solar system where there is complex life,

0:52:520:52:57

life that can build a civilisation,

0:52:570:53:00

is here on planet Earth.

0:53:000:53:03

But how did that happen? What is it that makes our world so special?

0:53:040:53:11

Because, after all, everything in the solar system shares the same genesis.

0:53:110:53:18

It was all created out of nothing more than a spinning cloud of gas and dust 4.5 billion years ago.

0:53:200:53:29

Solid worlds condensed out of the swirling mists.

0:53:380:53:42

But those worlds were radically different.

0:53:420:53:46

Around the solar system, there are worlds that erupt with volcanoes of sulphur.

0:53:500:53:56

And others with geysers of ice.

0:53:580:54:00

There are worlds with rich atmospheres and swirling storms.

0:54:030:54:08

And there are moons carved from ice

0:54:110:54:14

that hide huge oceans of liquid water.

0:54:140:54:17

But there's only one world where the laws of physics have conspired

0:54:220:54:27

to combine all these features in one place.

0:54:270:54:30

On Earth, the temperature and atmospheric pressure are just right

0:54:330:54:38

to allow oceans of liquid water to exist on the surface of the planet.

0:54:380:54:43

And it's big enough to have retained its molten core

0:54:460:54:51

that not only powers geysers and volcanoes,

0:54:510:54:54

but also produces our magnetic field

0:54:540:54:58

that fends off the solar wind and protects our thick, nurturing atmosphere.

0:54:580:55:03

It's the combination of all those wonders in one place

0:55:120:55:16

that allowed life to begin and to get a foothold here on Earth.

0:55:160:55:21

But, to allow that life to evolve into such complex creatures as ourselves

0:55:210:55:27

requires one more ingredient.

0:55:270:55:30

And that's time. Deep time.

0:55:300:55:33

The kind of time over which mountains rise and fall, and planets are formed and stars live and die.

0:55:330:55:41

And it's perhaps that that makes the earth so rare and so precious in the cosmos.

0:55:410:55:48

Because it's been stable enough for long enough for life to evolve

0:55:480:55:53

into such magnificent complexity.

0:55:530:55:56

The life we have on Earth today is the result of millions of years of stability.

0:56:050:56:11

And the pinnacle of that is us, humankind.

0:56:130:56:17

A species that has developed to the point where we can bend

0:56:190:56:23

and shape and change the world around us.

0:56:230:56:28

We have even left our own planet behind

0:56:300:56:34

to begin exploring our cosmic surroundings.

0:56:340:56:38

You could take the view that our exploration of the universe

0:56:490:56:54

has made us somehow insignificant.

0:56:540:56:57

One tiny planet around one star amongst hundreds of billions.

0:56:570:57:04

But I don't take that view.

0:57:040:57:06

Because we've discovered that it takes the rarest combination of chance, and the laws of nature,

0:57:060:57:13

to produce a planet that can support a civilisation.

0:57:130:57:18

That most magnificent structure

0:57:180:57:21

that allows us to explore and understand the universe.

0:57:210:57:26

And that's why, for me, our civilisation is THE wonder of the solar system.

0:57:260:57:33

MUSIC: "Calling Occupants Of Interplanetary Craft" by the Carpenters

0:57:340:57:38

# Calling occupants of interplanetary craft

0:57:390:57:43

# Calling occupants...

0:57:460:57:48

And if you were to be looking at the Earth from outside the solar system,

0:57:480:57:54

that much would be obvious.

0:57:540:57:56

# Calling occupants of interplanetary craft...

0:57:570:58:01

We have written the evidence of our existence onto the surface of our planet.

0:58:040:58:11

Our civilisation has become a beacon that identifies our planet as home to life.

0:58:110:58:18

# We'd like to make a contact with you

0:58:180:58:23

# Calling occupants of interplanetary, anti-adversary craft

0:58:290:58:36

# We are your friends

0:58:410:58:45

# We are your friends...#

0:58:490:58:52

If you'd like to know more about the solar system,

0:58:570:59:01

go to bbc.co.uk/science.

0:59:010:59:06

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0:59:060:59:09

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