0:00:07 > 0:00:12Ice is one of the most mesmerising and beguiling substances in the world.
0:00:14 > 0:00:19It's very familiar and yet never ceases to be other-worldly.
0:00:19 > 0:00:22Always a little bit strange.
0:00:26 > 0:00:28Ice is full of contradictions.
0:00:28 > 0:00:30It's transparent
0:00:30 > 0:00:33but it can glow with colour like nothing on earth.
0:00:33 > 0:00:36It's powerful enough to shatter rock and sink ships.
0:00:37 > 0:00:41But can just melt away in the blink of an eye.
0:00:47 > 0:00:50I'm Dr Gabrielle Walker.
0:00:50 > 0:00:54I trained as a chemist, but now I'm a science writer.
0:00:54 > 0:00:58And for a long time, I've been obsessed by ice.
0:00:59 > 0:01:01Ever since I first set foot on Arctic sea ice,
0:01:01 > 0:01:03I've been drawn back year after year.
0:01:05 > 0:01:11I've been trying to discover the secrets hidden deep within ice.
0:01:11 > 0:01:14I think the ice crystal has something extraordinary to reveal
0:01:14 > 0:01:16about how the world works.
0:01:16 > 0:01:19How it does that
0:01:19 > 0:01:23and what it tells us is what I want to explore in this programme.
0:01:23 > 0:01:25- This is it.- Wow!
0:01:25 > 0:01:29- Welcome to Nigarsbreen. - It's magnificent!
0:01:29 > 0:01:36I'm going to find out how something so ephemeral is powerful enough to carve solid rock.
0:01:37 > 0:01:43How ice has led to the evolution of some of the most extraordinary creatures on our planet.
0:01:43 > 0:01:45This is a really small one.
0:01:46 > 0:01:51How ice in space might lead us to discover extra-terrestrial life.
0:01:51 > 0:01:56If we've got an ocean underneath the surface of the moon,
0:01:56 > 0:01:58that's a place to search for life.
0:01:58 > 0:02:02And how its astonishing ability to store ancient atmospheres
0:02:02 > 0:02:05is helping us understand our climate.
0:02:06 > 0:02:10When they invaded Britain in 1066, this is the air they were breathing!
0:02:10 > 0:02:12Do your worst!
0:02:13 > 0:02:17And I reveal how its power to preserve our past
0:02:17 > 0:02:18and inform our future
0:02:18 > 0:02:21lies deep within the ice crystal.
0:02:36 > 0:02:39First of all, I've come to southern Norway...
0:02:40 > 0:02:44..to visit an enormous glacier called Jostedalsbreen.
0:02:48 > 0:02:51It's the biggest piece of ice in continental Europe.
0:02:53 > 0:02:56It covers nearly 500 square kilometres of mountain.
0:03:03 > 0:03:07Glaciers are one of the most powerful forces in nature.
0:03:07 > 0:03:12They turn fragile ice into enormous grinding machines
0:03:12 > 0:03:14that can erode mountains.
0:03:18 > 0:03:24I'm going to explore one of Jostedalsbreen's many glacial tongues, Nigardsbreen.
0:03:25 > 0:03:29I'm meeting local glaciologist, Evan Lowe.
0:03:29 > 0:03:31Hello, Evan!
0:03:31 > 0:03:33- Hello. Welcome to Jostedalsbreen. - Thank you.
0:03:33 > 0:03:35Gosh, it's gorgeous!
0:03:35 > 0:03:38We have a kayak to take us across the lake.
0:03:47 > 0:03:51I want to find out exactly what makes glaciers so powerful.
0:03:52 > 0:03:54How something as malleable as ice
0:03:54 > 0:03:58can carve out such a spectacular landscape.
0:03:58 > 0:04:00From the sculpted walls of the valley
0:04:00 > 0:04:02to the colour of the lake.
0:04:10 > 0:04:13- And full speed onto land. - Full speed.
0:04:18 > 0:04:22Even though it's just ten per cent of the Jostedalsbreen's glacier,
0:04:22 > 0:04:27Nigardsbreen covers nearly 50 square kilometres of mountain.
0:04:27 > 0:04:31It rises steeply to almost two kilometres above sea level.
0:04:35 > 0:04:39Down here in the valley, where the temperatures are warmer than in the high mountains,
0:04:39 > 0:04:42the glacier melts abruptly in a ragged wall.
0:04:44 > 0:04:49It's only when you get this much ice that you can witness something spectacular.
0:04:49 > 0:04:51- This is it!- Wow!
0:04:51 > 0:04:53'Its full range of colours.'
0:04:53 > 0:04:58It's magnificent! The blue colour is absolutely amazing.
0:04:58 > 0:05:01It's like looking into the heart of the glacier.
0:05:01 > 0:05:06Yes, it goes from completely white and all the way to very dark blue,
0:05:06 > 0:05:09depending on how the light hits the surface
0:05:09 > 0:05:12and how far into the ice the light penetrates
0:05:12 > 0:05:15before it's reflected to us.
0:05:20 > 0:05:22The surface of the glacier looks white
0:05:22 > 0:05:26because its jagged crystals are deflecting sunlight in all directions.
0:05:28 > 0:05:31Close up, the ice seems transparent.
0:05:31 > 0:05:33But it's not.
0:05:33 > 0:05:38Pure ice crystals absorb light at the red end of the spectrum.
0:05:40 > 0:05:42So as sunlight travels deeper into the ice,
0:05:42 > 0:05:45a new blue light is reflected back.
0:05:50 > 0:05:54When it's in a huge chunk like a glacier, it looks blue.
0:05:54 > 0:05:59But if you grab a chunk of it, it's just white, ordinary boring ice!
0:05:59 > 0:06:01Ice is never boring. Never, ever!
0:06:04 > 0:06:09The ice in this front wall is at the end of its journey down the mountain.
0:06:09 > 0:06:12It's now at the point of melting away.
0:06:12 > 0:06:15Every moment it's changing,
0:06:15 > 0:06:17like a moving sculpture.
0:06:22 > 0:06:24Melt water is raining down on me
0:06:24 > 0:06:27and it's making the most amazing shapes.
0:06:27 > 0:06:30You can see it's eating into the walls here
0:06:30 > 0:06:33and making all these curves and round parts
0:06:33 > 0:06:38and that's why it looks like the moon outside with all those incredible curves.
0:06:38 > 0:06:39It's beautiful.
0:06:46 > 0:06:48Although glacial ice is a solid,
0:06:48 > 0:06:50it actually flows like a river.
0:06:50 > 0:06:53It's incredible to think that this much ice
0:06:53 > 0:06:55is constantly on the move.
0:06:57 > 0:07:00I've been climbing up to see what drives the glacier.
0:07:02 > 0:07:06And it's the phenomenal weight of this enormous ice pack,
0:07:06 > 0:07:07over nine kilometres long,
0:07:07 > 0:07:10and up to 500 metres deep.
0:07:10 > 0:07:15Millions of tonnes of ice crammed into this valley.
0:07:18 > 0:07:20Built up from layer upon layer of snow,
0:07:20 > 0:07:25this monumental river of ice is constantly being topped up
0:07:25 > 0:07:26by fresh snowfall.
0:07:26 > 0:07:29And that keeps it flowing downhill.
0:07:30 > 0:07:35It makes very slow progress. But there is a way to see it move.
0:07:45 > 0:07:49A time-lapse camera shows that Nigardsbreen's surface ice
0:07:49 > 0:07:53travels at around 275 metres per year,
0:07:53 > 0:07:56carving away the rock as it goes.
0:08:03 > 0:08:07When you're here, the only clues you see of the glacier's movement
0:08:07 > 0:08:09are crevasses.
0:08:10 > 0:08:13Deep gashes that split open the surface of the ice.
0:08:15 > 0:08:17These open up at the top of the ice.
0:08:17 > 0:08:21One of the reasons is the top of the ice is brittle and tough.
0:08:21 > 0:08:25Further down, where it's been squeezed, it's plastic and soft.
0:08:25 > 0:08:28But as the glacier moves, the brittle part breaks open
0:08:28 > 0:08:30and creates these great crevasses.
0:08:34 > 0:08:37When a crevasse has opened up in the ice, melt water can gather in it
0:08:37 > 0:08:41and start hollowing its way down towards the bedrock.
0:08:43 > 0:08:48Here, it carves out a hidden world of icy caverns deep within the glacier.
0:08:51 > 0:08:57I'm going to try to abseil right into the heart of the glacier
0:08:57 > 0:08:59to see for myself how it moves.
0:09:10 > 0:09:12That was amazing!
0:09:18 > 0:09:20We're in the engine room of the glacier.
0:09:20 > 0:09:25You can see just down here right where the ice melts the ground.
0:09:25 > 0:09:28And this is where everything important happens.
0:09:28 > 0:09:31I'm getting wet with the melting water,
0:09:31 > 0:09:34but it's that that helps the glacier slide on its belly,
0:09:34 > 0:09:37one of the things that makes it so dynamic.
0:09:39 > 0:09:41Nigardsbreen's temperate mountain climate
0:09:41 > 0:09:47means the ice at the lower end of the glacier exists very close to melting point.
0:09:48 > 0:09:51As well as the melt water flowing beneath the ice,
0:09:51 > 0:09:55which helps lubricate the glacier on its journey down the mountain,
0:09:55 > 0:09:58there's melt water within the ice itself,
0:09:58 > 0:10:01seeping out of these walls.
0:10:02 > 0:10:07That melting water also makes this cave, and other caves like it all around.
0:10:07 > 0:10:11I bet this cave wasn't here last year and it probably won't be here next.
0:10:11 > 0:10:16It's transient, part of the signs that the glacier is dynamic
0:10:16 > 0:10:19and moving and changing all the time.
0:10:27 > 0:10:30When you look at the slick blue ice in these caves,
0:10:30 > 0:10:33it's hard to imagine it began its life as snowflakes.
0:10:35 > 0:10:37But hundreds of years of compression
0:10:37 > 0:10:41have gradually turned it into this glittering mass of ice crystals.
0:10:47 > 0:10:49Look at that!
0:10:49 > 0:10:52The sides of the ice here are just like they were in the cave.
0:10:52 > 0:10:57They really look like solid squashed together lumps and cubes.
0:10:57 > 0:11:00And here you can really see that.
0:11:00 > 0:11:04Like someone's taken a bunch of cubes and squeezed them together.
0:11:05 > 0:11:09And that's what I'm walking on. Like walking on a giant Slushie!
0:11:16 > 0:11:20Every single one of these ice crystals has an unusual property.
0:11:21 > 0:11:25If you throw them into water, they float.
0:11:26 > 0:11:29That's something we take completely for granted.
0:11:29 > 0:11:32But it's incredibly rare in nature.
0:11:34 > 0:11:37It's what helps to make ice special.
0:11:37 > 0:11:41And what gives it the power to transform our world.
0:11:46 > 0:11:49The secret lies at the heart of the ice crystal.
0:11:50 > 0:11:54I'm going to witness the very instant it forms,
0:11:54 > 0:12:00with chemist and fellow ice enthusiast, Dr Andrea Sella.
0:12:01 > 0:12:05Ice breaks all the rules that we learn.
0:12:05 > 0:12:10Andrea believes this moment is key to understanding the mysterious world of the ice crystal
0:12:10 > 0:12:17because of the curious way that water turns from liquid to solid ice.
0:12:17 > 0:12:19Let me show you something really amazing.
0:12:19 > 0:12:23We've got some mineral water here that we've been cooling for a bit.
0:12:23 > 0:12:26I want you to take these bottles quite gingerly.
0:12:26 > 0:12:29- Take this and bang it on the table. - Just bang it?- Bang it.
0:12:30 > 0:12:33- There it goes! Look at that! - Instant ice!
0:12:33 > 0:12:37It's spreading out these fingers and shards of ice all the way down.
0:12:37 > 0:12:41It's quite amazing. You can see the crystals growing before your very eyes!
0:12:45 > 0:12:49Ice is a crystal in which the water molecules are very carefully arranged.
0:12:49 > 0:12:52If you think of guards on parade,
0:12:52 > 0:12:57all lined up in neat rows, that's what a crystal is, and that's what ice is.
0:13:00 > 0:13:05Like any crystal, ice doesn't form spontaneously,
0:13:05 > 0:13:07even in this super-cooled water,
0:13:07 > 0:13:10which is well below zero degrees centigrade.
0:13:10 > 0:13:13It needs a seed, a template.
0:13:16 > 0:13:19You need someone to kind of blow the whistle
0:13:19 > 0:13:22and provide an initial point, saying start here.
0:13:23 > 0:13:29- So I bang it, you get bubbles and each of those bubbles is a place for the crystals to form.- Absolutely.
0:13:30 > 0:13:33You can do it in other ways, too.
0:13:33 > 0:13:36Take another bottle, and this time what we'll do
0:13:36 > 0:13:39is try dropping another piece of ice into it.
0:13:39 > 0:13:41Just pop it in.
0:13:41 > 0:13:43Ready, steady...
0:13:45 > 0:13:49It's really the ice which is acting as the initial starting point
0:13:49 > 0:13:51on which the rest of the ice grows.
0:14:00 > 0:14:04It's the way the ice crystal forms that is the key to why it floats.
0:14:07 > 0:14:10Water molecules are loosely held together by bonds
0:14:10 > 0:14:13which are constantly making and breaking.
0:14:13 > 0:14:16When the temperature drops to zero,
0:14:16 > 0:14:19these bonds begin to hold. Fast.
0:14:19 > 0:14:23Creating a hexagonal lattice, an ice crystal.
0:14:27 > 0:14:31In the lattice, the bonds hold the molecules far apart.
0:14:32 > 0:14:34It's that sudden opening out
0:14:34 > 0:14:38that makes ice lighter, less dense, than liquid water.
0:14:41 > 0:14:43In water, the approaches are quite close.
0:14:43 > 0:14:46When we get to ice, suddenly it expands a bit.
0:14:46 > 0:14:51And we end up with a strangely spacious open structure
0:14:51 > 0:14:55which is less dense and therefore it floats.
0:14:55 > 0:14:56It's really quite miraculous.
0:14:56 > 0:15:00- That's all down to the structure of the crystal?- Absolutely.
0:15:00 > 0:15:02Ice is incredibly special.
0:15:02 > 0:15:05The irony is that to us it's completely common.
0:15:05 > 0:15:09We take an ice cube and drop it into a drink and it floats.
0:15:09 > 0:15:11Well, it is almost unique
0:15:11 > 0:15:16in the enormous, the millions of compounds and materials that we know about,
0:15:16 > 0:15:19in being a solid that floats on its melt.
0:15:26 > 0:15:31If ice didn't float, the world would be a very different place.
0:15:32 > 0:15:35Instead of forming on the surface of the ocean,
0:15:35 > 0:15:39allowing marine life to survive beneath,
0:15:39 > 0:15:42ice would form on the sea bed,
0:15:42 > 0:15:45oceans would freeze from the bottom up
0:15:45 > 0:15:49and life as we know it might never have evolved at all.
0:15:53 > 0:15:58We also wouldn't have developed an elegant British pastime
0:15:58 > 0:16:02that began on frozen lakes and rivers hundreds of years ago.
0:16:10 > 0:16:14Every Sunday morning, members of the Royal Skating Club
0:16:14 > 0:16:19meet at Guildford ice rink to skate in what is called "the English style".
0:16:23 > 0:16:27Once considered England's highest form of skating art,
0:16:27 > 0:16:31"the English style" originates from the early 19th century.
0:16:31 > 0:16:35It combines a Victorian sense of elegance and understatement
0:16:35 > 0:16:38with a high level of skill.
0:16:38 > 0:16:41Around a centre marked by an orange,
0:16:41 > 0:16:45the skaters perform perfectly-shaped geometric figures
0:16:45 > 0:16:52in absolute unison, holding their bodies stiff and straight.
0:16:52 > 0:16:55Centre change, sub circle.
0:16:58 > 0:17:02In keeping with the Victorian horror of showing off,
0:17:02 > 0:17:06the challenge is to make these complex manoeuvres look graceful
0:17:06 > 0:17:08and effortless.
0:17:12 > 0:17:13These are lovely.
0:17:13 > 0:17:18Elaine Hooper, historian for the National Ice Skating Association,
0:17:18 > 0:17:21has some Victorian pictures of the English Style.
0:17:21 > 0:17:26It was very much a more polite style of skating. It was very dignified.
0:17:26 > 0:17:32The ladies had long dresses and big hats on and the men had top hats in Victorian times.
0:17:32 > 0:17:34That was the style of skating
0:17:34 > 0:17:37that evolved on the frozen lakes and rivers
0:17:37 > 0:17:39as early as the 1600s.
0:17:39 > 0:17:45Over the years, different moves were added when people wanted to make it more difficult.
0:17:47 > 0:17:50The English Style developed amongst the upper classes
0:17:50 > 0:17:54while Britain was experiencing what became known as "the little ice age".
0:17:54 > 0:17:59From the 13th century to the middle of the 19th century,
0:17:59 > 0:18:03British winters were up to two degrees cooler.
0:18:03 > 0:18:06Many lakes and rivers regularly froze over.
0:18:08 > 0:18:12Pepys himself talks about skating with Nell Gwyn on the Thames
0:18:12 > 0:18:17in one of the great frost fairs where they would roast hogs and skate.
0:18:17 > 0:18:20It was just a way of life then. It was much colder.
0:18:20 > 0:18:24The Thames doesn't tend to freeze over now so we can't have that again.
0:18:30 > 0:18:32We can skate because of another quality of ice.
0:18:32 > 0:18:34Its slipperiness.
0:18:39 > 0:18:43This may seem completely normal, but it's actually very rare for a solid.
0:18:47 > 0:18:52The reason we can skate is to do with what happens when ice is squeezed by a blade.
0:18:54 > 0:18:56The way it reacts to pressure.
0:19:01 > 0:19:05So Andrea Sella and I are going to put ice under a lot of pressure
0:19:05 > 0:19:07in a classic experiment.
0:19:09 > 0:19:15OK, we need to lift it up and get it onto our platform.
0:19:15 > 0:19:17- It is pretty heavy. - I'm strong, don't worry!
0:19:17 > 0:19:19Good. There we are.
0:19:19 > 0:19:22So now we need to unpack things.
0:19:24 > 0:19:26- Ooh, that's lovely!- Gorgeous!
0:19:28 > 0:19:30I'll lift it and you pull.
0:19:30 > 0:19:31That's great.
0:19:33 > 0:19:37What we're going to do is sling this wire over the top
0:19:37 > 0:19:42and hang these two really rather heavy weights,
0:19:42 > 0:19:45we're talking about seven kilos here.
0:19:45 > 0:19:46There we go.
0:19:46 > 0:19:49It's now suspended.
0:19:49 > 0:19:53What we have to do is wait for the pressure of the wire
0:19:53 > 0:19:55to work its magic on the ice.
0:20:01 > 0:20:04As we wait, the wire works its way through the ice.
0:20:04 > 0:20:06Almost cutting it in two.
0:20:08 > 0:20:11And behind the wire, the ice is sealing up again.
0:20:11 > 0:20:14Something very strange is going on.
0:20:19 > 0:20:21It's amazing. Look at it!
0:20:21 > 0:20:23So how's it gone through the ice like this?
0:20:23 > 0:20:29Of course, the wire has the weight on it. And because the wire's very thin,
0:20:29 > 0:20:32what it does is apply really quite a large pressure
0:20:32 > 0:20:34on a local area of the ice.
0:20:34 > 0:20:37We know that ice expands when it freezes
0:20:37 > 0:20:42so if you squeeze it, you can drive it back towards that molten state.
0:20:42 > 0:20:45So when you put pressure on it, it turns it back to water.
0:20:45 > 0:20:47You can re-melt it back to water.
0:20:51 > 0:20:54That's one of the key reasons we can skate.
0:20:54 > 0:20:59The pressure of the blades is enough to melt the top layer of ice into water
0:20:59 > 0:21:02which lubricates the skates.
0:21:04 > 0:21:07Friction can also help melt the ice.
0:21:09 > 0:21:13In our experiment, as the wire passed through the block,
0:21:13 > 0:21:16the ice sealed up behind.
0:21:16 > 0:21:21This shows how ice can engulf something solid
0:21:21 > 0:21:23leaving barely a trace.
0:21:25 > 0:21:30I was expecting the wire to cut through it. And it's completely sealed.
0:21:30 > 0:21:35- It looks as though it ought to fall apart.- It's an extraordinary process.
0:21:35 > 0:21:39Effectively, underneath the wire, the ice melts
0:21:39 > 0:21:42and then behind it, it re-freezes again.
0:21:42 > 0:21:44So this whole process is making the ice
0:21:44 > 0:21:48move between those two points on that knife-edge between liquid and solid.
0:21:48 > 0:21:51The pressure squeezes it,
0:21:51 > 0:21:54- take the pressure off and it freezes again.- Absolutely.
0:21:58 > 0:22:02This formidable ability to swallow up another solid
0:22:02 > 0:22:05is a real insight into just how peculiar ice is.
0:22:05 > 0:22:11It also explains how ice can do seemingly impossible things
0:22:11 > 0:22:13in nature.
0:22:20 > 0:22:23In Norway, at the foot of Nigardsbreen,
0:22:23 > 0:22:27glaciologist Evan Lowe has some local stories to tell
0:22:27 > 0:22:32of how glaciers can engulf things much bigger than a thin metal wire.
0:22:33 > 0:22:40From where we're sitting now we can see a place where a farm used to be, 250 years ago.
0:22:40 > 0:22:45Until it was knocked down by this glacier behind us
0:22:45 > 0:22:49and all the buildings and farm were just swallowed by the glacier.
0:22:49 > 0:22:52If something goes into the ice, what happens to it?
0:22:52 > 0:22:56A bit further south, there's a plane with a pilot who crashed in the '70s
0:22:56 > 0:22:58on top of the glacier.
0:22:58 > 0:23:03Before the rescuers could get there, the whole thing was covered by snow.
0:23:03 > 0:23:06And it never appeared again.
0:23:06 > 0:23:10Some guy calculated that it should come out of the glacier
0:23:10 > 0:23:15some 25 years later, but they're still waiting for it.
0:23:15 > 0:23:20- No-one's seen any trace of it. - So there's a plane, body and everything.
0:23:20 > 0:23:21Somewhere!
0:23:21 > 0:23:25That's a spooky ghost story to tell just before bed!
0:23:37 > 0:23:39When it comes to a glacier shaping the landscape,
0:23:39 > 0:23:42this ability of ice to absorb things
0:23:42 > 0:23:44is a real secret to its strength.
0:23:47 > 0:23:52Ice on its own is far too fragile to leave any mark on solid rock.
0:23:52 > 0:23:55It can only carve out a valley by picking up tools.
0:23:58 > 0:24:04The ice engulfs rocks and boulders as it moves down the mountainside.
0:24:04 > 0:24:08They pass through the ice and get dragged along in its underbelly.
0:24:08 > 0:24:13Together they scrape and chip away at the rock beneath.
0:24:16 > 0:24:21It's easy to imagine that this was once just one big mountain.
0:24:21 > 0:24:25And now all this space that we are in now
0:24:25 > 0:24:27is the result of the glacier
0:24:27 > 0:24:32taking its bites like this during thousands of years.
0:24:32 > 0:24:37I like the way you say, "taking bites". The rocks are the teeth of the glacier
0:24:37 > 0:24:39and that's what it's using to grind away.
0:24:39 > 0:24:44It's still doing it up there, making the valley bigger and wider.
0:24:44 > 0:24:48If it were some other solid like steel or rock,
0:24:48 > 0:24:51it would just sit there. It couldn't do this.
0:24:51 > 0:24:53That's one of the secrets of the ice
0:24:53 > 0:24:56that it's strong enough to carry big rocks to work on the surface
0:24:56 > 0:24:59but it's also soft enough to move.
0:25:08 > 0:25:14Over the thousands of years that Nigardsbreen has been advancing and retreating,
0:25:14 > 0:25:16it's been grinding down the rock
0:25:16 > 0:25:18like an enormous sheet of sand paper.
0:25:20 > 0:25:25Gradually, it's turned boulders and bedrock into dust so fine
0:25:25 > 0:25:27that when it's washed into the lake,
0:25:27 > 0:25:29it remains suspended there.
0:25:29 > 0:25:32And it's the minerals in this dust
0:25:32 > 0:25:35that give the lake its colour.
0:25:47 > 0:25:49So that piece of ice there has done everything.
0:25:49 > 0:25:52It's shaped and smoothed these rocks
0:25:52 > 0:25:54and it's made these scrape marks and teeth marks
0:25:54 > 0:26:00and down there, the bigger boulders and the pebbles and the silt
0:26:00 > 0:26:02all the way through to the colour of the lake,
0:26:02 > 0:26:04even the shape of the valley,
0:26:04 > 0:26:08everything about everything I see has been dictated and defined by the ice.
0:26:16 > 0:26:19But ice itself is ruled by temperature.
0:26:20 > 0:26:24That's what determines everything from how long it lasts
0:26:24 > 0:26:26to how and where it forms.
0:26:26 > 0:26:30And nowhere is this more true than in the sky,
0:26:30 > 0:26:33where ice is at its most unpredictable.
0:26:36 > 0:26:38Clouds are usually made of water vapour.
0:26:38 > 0:26:43But if it's cold enough, you can get clouds entirely made of ice crystals.
0:26:43 > 0:26:46When you get ice in the sky, that can cause havoc with the weather.
0:26:50 > 0:26:53One of the most treacherous forms of icy weather
0:26:53 > 0:26:55is an ice storm.
0:26:58 > 0:27:0211 Canadians have been killed and two million are without electricity
0:27:02 > 0:27:05after devastating ice storms swept the country.
0:27:05 > 0:27:10In 1998, eastern Canada was hit by a massive ice storm,
0:27:10 > 0:27:12its worst on record.
0:27:15 > 0:27:20Over five days, freezing rain turned into a slick glaze of ice
0:27:20 > 0:27:24and built up to 7.5 centimetres thick in some places.
0:27:27 > 0:27:32It became heavy enough to bring down trees and power lines.
0:27:35 > 0:27:40The ice storm forced the government to declare a state of emergency.
0:27:48 > 0:27:53Ice storms can begin high in the atmosphere.
0:27:55 > 0:27:59Here, ice crystals grow into delicate snowflakes
0:27:59 > 0:28:02with stunningly symmetrical branches.
0:28:07 > 0:28:11If snowflakes fall into a warmer band of air,
0:28:11 > 0:28:14they'll melt away into rain.
0:28:14 > 0:28:18But in the unusual circumstances that lead to an ice storm,
0:28:18 > 0:28:22there's much colder air beneath this warm layer
0:28:22 > 0:28:24and it's very close to the ground.
0:28:27 > 0:28:29As the rain falls through this cold air,
0:28:29 > 0:28:31it becomes super-cooled,
0:28:31 > 0:28:34ready to freeze again in an instant.
0:28:35 > 0:28:38It crystallises as soon as it touches something,
0:28:38 > 0:28:43creating layer upon hazardous layer of ice.
0:28:45 > 0:28:48MAN: Millions of people here in Montreal are affected.
0:28:48 > 0:28:51- WOMAN:- It's like a war scene, almost.
0:28:51 > 0:28:57We're going round house to house suggesting to people that it'll be a while before the power's back
0:28:57 > 0:29:01and it might be wise to relocate to a shelter.
0:29:05 > 0:29:07The damage cost the country 3 billion.
0:29:07 > 0:29:11In some areas, the ice didn't melt for three months.
0:29:22 > 0:29:25Temperature is truly the master of ice.
0:29:25 > 0:29:29And there's a mysterious phenomenon called hot ice,
0:29:29 > 0:29:32which freezes at room temperature.
0:29:34 > 0:29:39Hot ice is created by putting water under enormous pressure,
0:29:39 > 0:29:42far greater than any glacier on our planet.
0:29:44 > 0:29:47This is ice that we wouldn't normally find anywhere on Earth.
0:29:52 > 0:29:57Professor Paul Macmillan is going to show me how to make this high-pressure ice.
0:29:57 > 0:30:01What we've got is a little drop of liquid water
0:30:01 > 0:30:03and it's placed between two diamonds.
0:30:03 > 0:30:09Inside here we've got two tiny diamonds that are pressing together.
0:30:09 > 0:30:12You're going to turn this knob here very gently.
0:30:12 > 0:30:17Because otherwise you'll force the two diamonds together too fast and they'll break.
0:30:17 > 0:30:19I'll be very careful.
0:30:21 > 0:30:24I'm about to put a tiny drop of water under more pressure
0:30:24 > 0:30:28than occurs naturally anywhere on the Earth's surface.
0:30:28 > 0:30:30When this gets to around 12,
0:30:30 > 0:30:33- I want you to start to watch the screen.- OK.
0:30:33 > 0:30:35- Nine and a half now.- Yes.
0:30:35 > 0:30:38So what's happening is the pressure is going on
0:30:38 > 0:30:41- and the diamonds are squeezing that drop of water.- Yes.
0:30:41 > 0:30:45- It's close to 12.- I would slow it down just a wee bit.
0:30:45 > 0:30:51At the moment this is liquid water, but it's really squeezed now.
0:30:51 > 0:30:53The pressure's going up...
0:30:53 > 0:30:55Look at that!
0:30:55 > 0:30:56It's crystals!
0:30:56 > 0:31:01- Yeah.- Oh, that is cool.- You've just made ice crystals in there.
0:31:01 > 0:31:03They're growing as well, not just sitting there.
0:31:03 > 0:31:06It's a whole faceful of tiny crystals.
0:31:08 > 0:31:12The ice has formed even though it's way above zero degrees.
0:31:13 > 0:31:17See the room temperature is 25 degrees.
0:31:17 > 0:31:20- So we've made water freeze at 25 degrees C?- Yes.
0:31:20 > 0:31:24These are icebergs floating in dense water.
0:31:26 > 0:31:29'The hot ice is at a pressure of 15,000 atmospheres.
0:31:29 > 0:31:33'That's 15 times more pressure
0:31:33 > 0:31:37'than you find at the bottom of the deepest ocean on Earth.'
0:31:37 > 0:31:41What would it be like, then? I know we can't take it out and look at it
0:31:41 > 0:31:43or do things with it because it's under that pressure.
0:31:43 > 0:31:46But how is it different from real, normal ice?
0:31:46 > 0:31:51The first thing is that it doesn't melt at normal temperatures.
0:31:51 > 0:31:58This one here, you'd have to take this up to well over 100 degrees centigrade
0:31:58 > 0:32:00for it even to start to melt.
0:32:00 > 0:32:03So you can go above boiling point and it doesn't melt?
0:32:03 > 0:32:06Exactly. This is a high-density form of ice.
0:32:06 > 0:32:10The structure is very like a little cube.
0:32:10 > 0:32:14You would never get the hexagon snowflake shapes
0:32:14 > 0:32:17that you get with normal ice.
0:32:17 > 0:32:22'This kind of ice might occur naturally out in space.'
0:32:23 > 0:32:28We think that it probably does exist in the solar system,
0:32:28 > 0:32:32deep inside some of the icy moons out there
0:32:32 > 0:32:36like Titan, which is the large moon of Saturn.
0:32:36 > 0:32:39And we know that the pressure inside
0:32:39 > 0:32:41gets to these pressure values.
0:32:41 > 0:32:46- So it's like having a telescope to look into the heart of Saturn's moon.- Exactly.
0:32:49 > 0:32:53We know already that the surfaces of some of the moons of Jupiter and Saturn
0:32:53 > 0:32:58are covered in more normal ice, the type we're familiar with on Earth.
0:33:01 > 0:33:04Recently, we've been able to get close enough to see it
0:33:04 > 0:33:06in more detail.
0:33:06 > 0:33:09And that's revealed something startling.
0:33:09 > 0:33:14It might be protecting oceans of liquid water out in space.
0:33:17 > 0:33:22Professor Michele Dougherty is a space physicist who explores these outer planets.
0:33:27 > 0:33:29It was Jupiter's moon, Europa,
0:33:29 > 0:33:32that first attracted her attention
0:33:32 > 0:33:36thanks to a surprising photograph taken by the Galileo spacecraft.
0:33:39 > 0:33:43This image shows us what looks like an ice shelf
0:33:43 > 0:33:45which is floating on a liquid.
0:33:45 > 0:33:49We could almost say it was the Antarctic or Greenland.
0:33:49 > 0:33:55What you can clearly see are these icebergs which look as if they're moving around on the surface.
0:33:55 > 0:33:59The only way for that to happen is for there to be liquid underneath
0:33:59 > 0:34:02that's helping shift them around on the icy surface.
0:34:06 > 0:34:08By studying data from Galileo,
0:34:08 > 0:34:12scientists reckon that Europa's ice is covering an ocean
0:34:12 > 0:34:13of liquid water.
0:34:17 > 0:34:20If true, this will be an amazing discovery.
0:34:20 > 0:34:25But frustratingly, there's no way yet of penetrating the surface
0:34:25 > 0:34:27to confirm it.
0:34:34 > 0:34:36However, in 1997,
0:34:36 > 0:34:39an unmanned probe called Cassini
0:34:39 > 0:34:41was sent into space.
0:34:42 > 0:34:48Its mission, to explore Saturn, 700 million miles from Earth.
0:34:50 > 0:34:55When it flew by a tiny ice-covered moon called Enceladus,
0:34:55 > 0:35:00it gave a reading that Michele and her team simply couldn't explain.
0:35:01 > 0:35:07So she asked the mission planners if Cassini could make a closer fly-by.
0:35:08 > 0:35:09And this revealed a spectacle
0:35:09 > 0:35:12that had never been seen before
0:35:12 > 0:35:14anywhere in the solar system.
0:35:16 > 0:35:20This is the image we took when we went really close to Enceladus.
0:35:20 > 0:35:23You can clearly see this large plume of water vapour
0:35:23 > 0:35:26coming off from the south pole. A gorgeous image!
0:35:26 > 0:35:32As Cassini has shown us that water definitely exists under Enceladus's ice,
0:35:32 > 0:35:38that makes it a fantastic place to search for evidence of extra-terrestrial life.
0:35:39 > 0:35:43The reason that this discovery is so amazing
0:35:43 > 0:35:48is that it's telling us there's water under the surface of Enceladus
0:35:48 > 0:35:51and in the plume itself there is water vapour,
0:35:51 > 0:35:53there are ice crystals
0:35:53 > 0:35:56and there are organic compounds - nitrogen, carbon, hydrogen -
0:35:56 > 0:36:00all the things that you need for the basic building blocks of life.
0:36:02 > 0:36:07Michele and her colleagues are currently working on building much smaller probes
0:36:07 > 0:36:11that will be able to analyse the plumes jetting out from Enceladus.
0:36:13 > 0:36:15They'll look for more evidence of life.
0:36:16 > 0:36:21Ice in space may bring us one step closer to finding out
0:36:21 > 0:36:24if other life forms have evolved in our solar system.
0:36:40 > 0:36:43Although icy environments even on our own planet
0:36:43 > 0:36:45seem too hostile to support life,
0:36:45 > 0:36:50in fact they can be a very favourable place for life to flourish.
0:36:53 > 0:36:57Under the sea ice around the edges of the Antarctic continent,
0:36:57 > 0:37:00at temperatures that would kill most living things,
0:37:00 > 0:37:03live some of the most intriguing creatures on Earth.
0:37:05 > 0:37:08In total, I've been to the Antarctic 13 times.
0:37:08 > 0:37:12'At the laboratories of the British Antarctic Survey,
0:37:12 > 0:37:16'Professor Lloyd Peck studies these creatures to find out
0:37:16 > 0:37:17'just how they survive
0:37:17 > 0:37:22'and what makes the icy ocean so advantageous for some forms of life.'
0:37:23 > 0:37:25If we move down here,
0:37:25 > 0:37:27we can see some of our really special animals.
0:37:27 > 0:37:30These little fish are called the plunder fish.
0:37:30 > 0:37:32I haven't seen this.
0:37:32 > 0:37:36- That's a beauty! Is it all right? - Yeah, they're fine.
0:37:36 > 0:37:41If a predator comes along, they open their mouth, push their gill cases out
0:37:41 > 0:37:43and push their spines out to stop being eaten.
0:37:43 > 0:37:49They breed in our tank. They're one of the classic types of Antarctic fish.
0:37:49 > 0:37:52- How cold is it? - The water is below zero degrees.
0:37:52 > 0:37:54But it's sea water so it doesn't freeze.
0:37:54 > 0:37:57What you see here is, those animals living there
0:37:57 > 0:38:00are permanently living below zero degrees.
0:38:00 > 0:38:03- Why don't they freeze? - Well, the fish would freeze
0:38:03 > 0:38:08except for the fact they've got antifreeze in their blood, their tissues and their bodies.
0:38:08 > 0:38:11They need antifreeze to live in these temperatures.
0:38:11 > 0:38:17- They have antifreeze in their blood? - They make their own antifreeze. They have antifreeze proteins.
0:38:17 > 0:38:20There's antifreeze everywhere because without it,
0:38:20 > 0:38:24ice crystals would grow inside their cells and inside their blood
0:38:24 > 0:38:26and it would rip their tissues apart.
0:38:28 > 0:38:31OK. I've got another animal here to show you.
0:38:31 > 0:38:33This is a sea spider.
0:38:33 > 0:38:35Oh, look at him!
0:38:35 > 0:38:38In Antarctica, the sea spiders get really big.
0:38:38 > 0:38:42The biggest ones are 40 centimetres from leg tip to leg tip.
0:38:42 > 0:38:45- So that's twice the size of this one?- About twice the size.
0:38:45 > 0:38:48And the biggest sea spiders in the Antarctic
0:38:48 > 0:38:51are a thousand, maybe two thousand, three thousand times heavier
0:38:51 > 0:38:55- than the biggest sea spiders in Europe.- Why do they get so big?
0:38:55 > 0:38:59Well, the reason they get big is because it's cold!
0:38:59 > 0:39:02Two things happen when sea water gets cold.
0:39:02 > 0:39:06One is that the amount of oxygen you get in the water goes up.
0:39:06 > 0:39:11There's nearly twice as much oxygen in the sea in Antarctica as in the tropics.
0:39:11 > 0:39:16Because it's cold, their metabolic rates run much slower than animals elsewhere.
0:39:16 > 0:39:18So it's like live cheaper, grow bigger?
0:39:18 > 0:39:22Live cheaper, grow bigger. And it's not just the sea spiders.
0:39:22 > 0:39:25This is a 40-arm starfish.
0:39:25 > 0:39:29- Its Latin name is Labidiaster. - Oh, my God!
0:39:29 > 0:39:31Have a hold of that.
0:39:31 > 0:39:33OK? This is a really small one.
0:39:33 > 0:39:39The big ones get up to 70, 80 centimetres across. They're huge.
0:39:39 > 0:39:43They're one of the big predators in the Antarctic on the sea bed.
0:39:43 > 0:39:48There's his stomach. They crawl over the top of animals, put their stomachs out and eat them.
0:39:49 > 0:39:54What is it about the ice that makes all these weird adaptations and strange animals?
0:39:54 > 0:39:57The ice helps keep the temperature constant in the seas.
0:39:57 > 0:40:01What it's done is kept that temperature low and constant
0:40:01 > 0:40:03for maybe 25 million years.
0:40:03 > 0:40:06So it's not just cold, it's also steady.
0:40:06 > 0:40:11It is. The Antarctic Ocean is possibly the most constant temperature place on Earth.
0:40:11 > 0:40:16And it's been there for such a long time that animals have been able to adapt to it
0:40:16 > 0:40:20in a very fine-scaled way, in a way that hasn't happened anywhere else on Earth.
0:40:24 > 0:40:27These creatures are the product of a unique eco-system
0:40:27 > 0:40:30that revolves around ice.
0:40:31 > 0:40:35By studying how they managed not just to adapt, but to thrive,
0:40:35 > 0:40:38we can learn about the impact of cold
0:40:38 > 0:40:41and how well icy environments can support life.
0:40:50 > 0:40:55Antarctica is the coldest, windiest continent on the planet.
0:40:56 > 0:41:01It's covered by the largest single mass of ice on Earth.
0:41:16 > 0:41:19Back in the 1950s,
0:41:19 > 0:41:22a team of scientists set out with a seemingly impossible dream,
0:41:22 > 0:41:26to discover how thick the Antarctic ice sheet was
0:41:26 > 0:41:29and what might be lying beneath.
0:41:32 > 0:41:37Part of that team was glaciologist, Dr Charles Swithinbank.
0:41:39 > 0:41:42He's a legend in the world of Antarctic science.
0:41:42 > 0:41:46He's spent a lifetime exploring the heart of the white continent.
0:41:48 > 0:41:50- That's it.- That's you?
0:41:50 > 0:41:53That's me. I was mad keen and always have been.
0:41:53 > 0:41:58Here was a chance of real adventure and real exploring
0:41:58 > 0:42:02in a really unknown part of the Antarctic.
0:42:06 > 0:42:09It was Charles' job to try to measure the depth of the ice.
0:42:10 > 0:42:14Taking a sled loaded with dynamite out onto the ice,
0:42:14 > 0:42:19he and his colleagues set off an explosion at the surface.
0:42:21 > 0:42:24They measured how long it took for its echo to bounce back.
0:42:24 > 0:42:28From this, they could work out how far it had travelled
0:42:28 > 0:42:31and how thick the ice sheet was.
0:42:33 > 0:42:37We found thicknesses up to 2,500 metres.
0:42:37 > 0:42:42That's nothing nowadays. People have found a lot deeper.
0:42:42 > 0:42:44But it staggered us
0:42:44 > 0:42:47because here we were, walking over solid ice
0:42:47 > 0:42:50without any idea how thick it was.
0:42:52 > 0:42:55But as it took a day to make one single measurement,
0:42:55 > 0:42:59mapping the whole continent was going to take decades.
0:43:02 > 0:43:08Until another ice secret was unlocked by American army engineer, Amory Waite.
0:43:11 > 0:43:17In the 1950s, experienced pilots were crashing into the Antarctic ice sheet and no-one knew why.
0:43:20 > 0:43:25Waite knew the planes' altimeters used radar to measure how high they were above the ground.
0:43:26 > 0:43:31He started hitting ice with different frequencies of radio waves
0:43:31 > 0:43:35and realised some of them were going straight through the ice.
0:43:35 > 0:43:39This could have given the pilots a false reading of their height.
0:43:41 > 0:43:44Waite realised that despite being a solid,
0:43:44 > 0:43:47ice was transparent to radar.
0:43:49 > 0:43:52Once this was known, planes stopped crashing,
0:43:52 > 0:43:54saving countless lives.
0:43:55 > 0:43:59But it also revolutionised Charles Swithinbank's job
0:43:59 > 0:44:03of surveying the Antarctic ice sheet and the land beneath.
0:44:05 > 0:44:09His team could now criss-cross the continent in a plane,
0:44:09 > 0:44:12using radar to see through the ice
0:44:12 > 0:44:15by bouncing radio waves off the bedrock below.
0:44:15 > 0:44:20And he could now take hundreds of readings every second.
0:44:25 > 0:44:26It was staggeringly exciting
0:44:26 > 0:44:30because we were getting a cross-section of the ice sheet as we flew over it.
0:44:30 > 0:44:36We went to a number of places where I'd worked on the ground
0:44:36 > 0:44:38and dreamed and wondered how thick the ice was.
0:44:38 > 0:44:41And in the matter of a minute -
0:44:41 > 0:44:44pow! - we'd measured how thick it was.
0:44:44 > 0:44:46It was very, very exciting.
0:44:48 > 0:44:51Beneath the white and pristine Antarctic surface,
0:44:51 > 0:44:53an entire new world was uncovered.
0:44:54 > 0:44:58A world made of valleys, mountains and plateaus
0:44:58 > 0:45:02hidden in parts by ice more than four kilometres thick.
0:45:05 > 0:45:09And all laid bare thanks to discovering another secret of the ice crystal.
0:45:19 > 0:45:22While the Antarctic lies on mountainous bedrock,
0:45:22 > 0:45:26on the other side of the world, the Arctic is a treacherous ocean
0:45:26 > 0:45:28of floating sea ice,
0:45:28 > 0:45:32where exploration has often been driven by commerce.
0:45:42 > 0:45:47For hundreds of years, sailors searched for a short and lucrative trade route through these waters
0:45:47 > 0:45:50between Europe and the Pacific.
0:45:50 > 0:45:54One that would be cheaper than the long route via India and China.
0:45:54 > 0:45:58The elusive North-West Passage.
0:46:03 > 0:46:08For the expedition that found it, there was a prize of thousands of pounds.
0:46:09 > 0:46:13I'm interested in the story of one particular expedition.
0:46:13 > 0:46:16It was led by a celebrated naval officer, Sir John Franklin.
0:46:16 > 0:46:22But it turned out to be the worst disaster in the history of British polar exploration.
0:46:25 > 0:46:26What draws me to this story
0:46:26 > 0:46:29is that it plays out like a detective mystery
0:46:29 > 0:46:32with ice as the key witness.
0:46:33 > 0:46:39And some of the clues are here, at the Scott Polar Research Institute.
0:46:40 > 0:46:43This is the leader of the expedition, Sir John Franklin.
0:46:43 > 0:46:47In 1845, he was already 59 years old.
0:46:47 > 0:46:50He'd fought with Nelson at the Battle of Trafalgar.
0:46:50 > 0:46:53He'd been to the Arctic three times and mapped thousands of miles of coastline.
0:46:53 > 0:46:57The British public had been captivated by stories of how he and his men
0:46:57 > 0:47:00staved off hunger by eating their own leather boots.
0:47:04 > 0:47:06Franklin was clearly the man for the job.
0:47:07 > 0:47:13Before he set off, he arranged to have portraits taken of himself and his senior officers
0:47:13 > 0:47:15with the very latest technology.
0:47:17 > 0:47:22Curator Heather Lane has these precious early daguerreotypes
0:47:22 > 0:47:23for me to see.
0:47:23 > 0:47:26- If you'd like to pick it up and open it.- I'd love to.
0:47:26 > 0:47:28Very happy.
0:47:28 > 0:47:31And there he is.
0:47:31 > 0:47:38Quite extraordinary to think you're seeing him on the day they set off.
0:47:39 > 0:47:44'Franklin had assembled a team of experienced officers to sail with him to the Arctic,
0:47:44 > 0:47:47'many of whom had been there before.'
0:47:47 > 0:47:52- They all look quite sure of themselves.- Franklin had been sensible.
0:47:52 > 0:47:55He's pulled together a team he knows will actually obey orders
0:47:55 > 0:47:59in what are likely to be quite difficult circumstances.
0:48:03 > 0:48:07In total, 133 men set sail with Franklin from Kent
0:48:07 > 0:48:11in two sturdy ships, the Erebus and the Terror,
0:48:11 > 0:48:15both of which had seen service in the Polar regions before.
0:48:17 > 0:48:20They were expecting to sail from the Atlantic Ocean
0:48:20 > 0:48:23through the ice-bound islands of Northern Canada
0:48:23 > 0:48:28to the Pacific Ocean, and return within three years.
0:48:31 > 0:48:36They'd refitted these ships with state-of-the-art equipment. They were steam-powered,
0:48:36 > 0:48:40they had water purification, they had central heating on board.
0:48:40 > 0:48:44They really put a huge amount of effort into ensuring
0:48:44 > 0:48:50that this was the expedition that was going to make it all the way through the North-West Passage.
0:48:50 > 0:48:53Then suddenly, they disappear.
0:48:53 > 0:48:56The ice has swallowed this expedition whole.
0:48:56 > 0:49:02And it's the beginning of a great Victorian mystery - what has happened to Franklin and his men?
0:49:03 > 0:49:05Over the next few years,
0:49:05 > 0:49:10more than 30 rescue missions searched the icy Arctic for survivors
0:49:10 > 0:49:11but failed to find any.
0:49:14 > 0:49:19It wasn't until 1858 that the likely fate of Franklin's men was confirmed
0:49:19 > 0:49:25by a message discovered in a can on a small uninhabited island.
0:49:28 > 0:49:30Written by two senior officers,
0:49:30 > 0:49:35it announced that Sir John Franklin had died in 1847,
0:49:35 > 0:49:37two years after he'd set sail.
0:49:39 > 0:49:42Both ships had been abandoned in the ice
0:49:42 > 0:49:48and second-in-command Captain Crozier was attempting to lead 105 survivors to safety.
0:49:50 > 0:49:55But why had an expedition with experienced Polar navigators
0:49:55 > 0:49:57in state-of-the-art ships,
0:49:57 > 0:49:59ended up like this?
0:50:00 > 0:50:02Well, although the records end here,
0:50:02 > 0:50:05the detective story doesn't.
0:50:05 > 0:50:09What I find fascinating about the Franklin story
0:50:09 > 0:50:13is it doesn't seem to die. Clues keep on showing up in the ice.
0:50:15 > 0:50:20And eventually, it would be the ice that would provide the answer.
0:50:27 > 0:50:31In 1986, a team of forensic archaeologists
0:50:31 > 0:50:35travelled to Beachy Island in northern Canada.
0:50:35 > 0:50:37This was where, in 1850,
0:50:37 > 0:50:41a search party had found empty food cans,
0:50:41 > 0:50:43evidence that the expedition had wintered here.
0:50:46 > 0:50:50And not far from them, three graves.
0:50:55 > 0:50:58Over two intense weeks, Dr Owen Beatty and his team
0:50:58 > 0:51:01exhumed the bodies of able seaman John Hartnell
0:51:01 > 0:51:03and Private William Brain
0:51:03 > 0:51:05to try to find out how they'd died.
0:51:08 > 0:51:12The forensic team had no idea what to expect. What condition the bodies would be in.
0:51:12 > 0:51:15They had to pick-axe their way through the frozen ground
0:51:15 > 0:51:21which is what the grave-diggers must have had to do when they buried the bodies in the Arctic winter.
0:51:25 > 0:51:29They found that the ice had preserved the bodies almost perfectly.
0:51:29 > 0:51:33When they released them, using warm water,
0:51:33 > 0:51:38there was so little decay, it was relatively easy to investigate how they'd died.
0:51:40 > 0:51:46John Hartnell had had tuberculosis, but he was also incredibly thin.
0:51:46 > 0:51:50He had no food in his stomach or intestines.
0:51:53 > 0:51:58Scattered around the camp, Beatty had found empty cans that had been soldered with lead.
0:51:58 > 0:52:01He put two and two together.
0:52:01 > 0:52:03He tested the men's bodies
0:52:03 > 0:52:06and found dangerously high levels of lead
0:52:06 > 0:52:09in their hair, bones and soft tissue.
0:52:12 > 0:52:15To date, about 17 more of Franklin's men
0:52:15 > 0:52:19have been found to have had toxic levels of lead in their bones.
0:52:22 > 0:52:26New research suggest the lead might not have come from the cans at all
0:52:26 > 0:52:32but is more likely to have leeched out of the new lead piping in the ship's water system
0:52:32 > 0:52:34and contaminated their water.
0:52:40 > 0:52:43Lead poisoning is a horrible way to die.
0:52:43 > 0:52:47It paralyses your muscles and eats away at your brain and central nervous system.
0:52:47 > 0:52:51So then what you get is disorientation and anorexia.
0:52:51 > 0:52:55The worst things that can happen if you're trying to survive an Arctic winter.
0:53:09 > 0:53:12We know so much about the tragic fate of Franklin and his men
0:53:12 > 0:53:15because of the miraculous ability of ice to preserve.
0:53:15 > 0:53:19But it doesn't just preserve history by slowing down decomposition.
0:53:19 > 0:53:24It also has the ability to preserve something much more delicate than bodies.
0:53:24 > 0:53:28And one that might prove even more valuable.
0:53:35 > 0:53:40In the Antarctic, teams of scientists have been reaching back into history.
0:53:42 > 0:53:46They've been drilling thousands of metres into the ice sheet
0:53:46 > 0:53:50to remove columns of ice that can bear witness to our past.
0:53:53 > 0:53:59These ice cores preserve air from hundreds of thousands of years ago.
0:54:01 > 0:54:06They're helping us understand one of the most complex aspects of nature,
0:54:06 > 0:54:07our climate.
0:54:12 > 0:54:15I'm with Dr Robert Mulvaney
0:54:15 > 0:54:19at the British Antarctic Survey's ice core freezer in Cambridge
0:54:19 > 0:54:21where he studies this ancient ice.
0:54:27 > 0:54:28So if I take a piece of this out.
0:54:28 > 0:54:31Let's put that down on here.
0:54:35 > 0:54:38You can probably make out the tiny air balls in there.
0:54:38 > 0:54:42It's the magic of the ice that it's able to take these air molecules
0:54:42 > 0:54:47- into its matrix without altering them, and release them back to us later.- A storage box.- Yes.
0:54:47 > 0:54:51What we'll do is cut a piece off and see if we can see the air bubbles.
0:54:52 > 0:54:55The deeper you go, the older the ice gets.
0:54:55 > 0:54:58Scientists are able to date each layer of ice
0:54:58 > 0:55:01from chemical markers within the ice crystal itself.
0:55:03 > 0:55:07It's starting to clear. I think you can see the air bubbles in that.
0:55:07 > 0:55:10Fantastic, isn't it?
0:55:10 > 0:55:12This air is about 1,000 years old!
0:55:12 > 0:55:15So when they were invading Britain in 1066,
0:55:15 > 0:55:18this is the air they would have been breathing!
0:55:18 > 0:55:20- The Saxons and Normans. - Saxons and Normans.
0:55:20 > 0:55:22- That is wild!- It is, isn't it?
0:55:24 > 0:55:26This is quite a long way down in the ice sheet.
0:55:26 > 0:55:31This is about 80,000 years old. You can probably see the air in that.
0:55:31 > 0:55:35So this is before... This fell as snow and trapped air
0:55:35 > 0:55:37before human civilisation?
0:55:37 > 0:55:40That's right. Fascinating, isn't it?
0:55:42 > 0:55:44As well as preserving past atmospheres,
0:55:44 > 0:55:48the ice crystals preserve another important secret.
0:55:48 > 0:55:51Tiny variations in their chemistry
0:55:51 > 0:55:55reveal the temperature of the climate when they originally formed.
0:55:55 > 0:55:59This has allowed us to see in more detail than ever before
0:55:59 > 0:56:02how our climate has changed throughout history.
0:56:04 > 0:56:07It's also enabled us to explore a link
0:56:07 > 0:56:10between temperature and levels of atmospheric carbon dioxide.
0:56:13 > 0:56:17Our oldest ice core goes back 800,000 years.
0:56:17 > 0:56:20In that period, we've been in and out of an ice age eight times.
0:56:20 > 0:56:26And all through that period, the atmosphere and the temperature have been very closely linked.
0:56:26 > 0:56:31So as we go into an ice age, the levels of carbon dioxide, greenhouse gases, decrease,
0:56:31 > 0:56:34and as come out of an ice age they start to increase.
0:56:34 > 0:56:41The ice core record shows that there was a strong relationship between temperature and carbon dioxide.
0:56:41 > 0:56:46They've moved in tandem throughout history for 800,000 years.
0:56:49 > 0:56:54To many scientists, this historical record supports current theories of global warming,
0:56:54 > 0:56:58suggesting that if carbon dioxide levels rise, as they're doing today,
0:56:58 > 0:57:01temperatures will also rise.
0:57:01 > 0:57:05It's a warning from the past that many find hard to ignore.
0:57:05 > 0:57:09And all because of the unique ability of ice
0:57:09 > 0:57:11to capture air and preserve it.
0:57:20 > 0:57:24Ice is one of the most enigmatic substances in nature.
0:57:24 > 0:57:29A solid can pass through it, without leaving a trace.
0:57:31 > 0:57:34It can shatter rock and sculpt our planet.
0:57:37 > 0:57:41In space, its protective shell may conceal life forms
0:57:41 > 0:57:43just waiting to be discovered.
0:57:45 > 0:57:48It can last for millions of years
0:57:48 > 0:57:50or just melt in an instant.
0:57:54 > 0:57:56I'm drawn to ice because of its contradictions.
0:57:56 > 0:58:02Although is seems so fragile, it's capable of carving out landscapes and preserving histories,
0:58:02 > 0:58:05even giving us warnings about the future of our world.
0:58:05 > 0:58:08But what's really struck me about making this programme
0:58:08 > 0:58:11is discovering where all that power comes from.
0:58:11 > 0:58:15Because actually, the very thing that makes ice seem fragile and vulnerable,
0:58:15 > 0:58:18the fact that it's always on the point of disappearing
0:58:18 > 0:58:21turns out to be the source of all its strength.
0:58:49 > 0:58:52Subtitles by Red Bee Media Ltd