Solar episode 1 - Volcano
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00:00So far, we've set foot on one world beyond our own.
00:15We discovered a desolate, barren rock.
00:20An ancient, unchanging, cratered world.
00:27And the footprints we left there could last for millions of years.
00:35Our only direct personal experience of an alien world is of our moon.
00:39Beautiful, but a dead, inactive world, frozen in time.
00:44Whereas our planet is active and alive.
00:48If you come to the right places on Earth, it's literally seething with energy beneath
00:56our feet.
01:07For a long time, we wondered if all this activity is unique to our planet.
01:14But now, thanks to a fleet of spacecraft, we know our world is not alone.
01:27We currently have over 40 probes exploring the solar system, relaying a stream of information
01:34to Earth, allowing us to see our sister worlds in unprecedented detail.
01:49They're revealing planets and moons covered with volcanoes, dwarfing anything seen on
01:55our planet.
02:01Alien landscapes bursting with fire.
02:07And ice.
02:12Eruptions so violent, they reach into space.
02:22So why are some worlds vibrant and alive, while others are cold and dead?
02:32Now that question is deeper than it first sounds, because answering it will have profound
02:36implications for our understanding of our place in the universe.
02:41See, geological activity, the flow of energy from the interior of a world outwards, is
02:46necessary for the origin of life.
02:50And that's why finding and understanding those worlds is a necessary first step in the search
02:56for life beyond Earth.
03:10Let's begin a journey to the volcano worlds, by leaving Earth, heading away from the sun,
03:38and setting a course to the planet next door, the most visited of them all.
04:04For almost two decades, the Mars Reconnaissance Orbiter has pointed its cameras at the red
04:10planet.
04:20And the images it has sent back have revealed volcanoes on a staggering scale.
04:31One so wide, it would span the UK.
04:41And one so tall, it rises up through Mars' atmosphere, almost to the edge of space.
04:59Over time, these mega-volcanoes have flooded the Martian surface with a billion, billion
05:05tonnes of lava.
05:13So much that they've tipped the entire planet over by 20 degrees.
05:28So what drives a planet's volcanism?
05:48Iceland's one of the most volcanically active places on Earth.
05:52This is the Icelandic Met Office, so this is the weather forecasting site.
05:56But it also gives you a real-time update on earthquakes, and earthquakes are precursors
06:03for volcanic eruptions.
06:04These dots are all earthquakes that have happened in the last few hours, actually.
06:10And we, at the moment, are driving along the roads in there.
06:17So is that OK, by the way?
06:20Oh, yeah, that's normal.
06:22It's normal?
06:23Yeah.
06:24Yeah.
06:25When you have a collection of earthquakes like this, a lot in the same place at the
06:30same time, it's called the Järðhreyringar.
06:32Järðhreyringar.
06:33Järðhreyringar.
06:34Järðhreyringar.
06:35Järðhreyringar.
06:36Yeah.
06:37So it's basically stirring the Earth.
06:38Stirring the Earth, yeah.
06:47But recently, the land here did more than stir.
07:08Just last year, over 10 million cubic metres of lava flowed out down this valley, creating
07:15brand new land.
07:17This is planet-building in action.
07:28Activity so recent, you can still see the afterglow.
07:40So there's the old volcano in the distance, which is old and cold.
07:46And then there's all this new land.
07:48And look, it's glowing.
07:54To drive volcanism on this scale takes an enormous amount of energy.
08:01So where does it all come from?
08:06Think about what was happening here about four and a half billion years ago.
08:13So this would have been a cloud of gas and dust and rocks, and all those rocks falling
08:21together under the influence of gravity, ultimately to form the primordial Earth.
08:30During our planet's formation, that gravitational energy was transformed into heat, adding to
08:38the heat released by the decay of radioactive elements.
08:45Heat is a form of energy.
08:47Now there's a law of physics, a law of thermodynamics, called the first law of thermodynamics, and
08:53it says that energy is neither created nor destroyed.
08:56So the energy released when all those rocks were smashing together to form the primordial
09:01Earth is still here.
09:04It's stored, trapped ever since.
09:14Just below the surface there, down in that crack, it's just glowing hot.
09:29Mars formed at the same time and in the same way.
09:33The planet trapping enough heat to raise the largest volcanoes in the solar system.
09:46But unlike the Earth, these giant volcanoes fell silent millions of years ago.
10:02Nothing happened to Mars's inner heat.
10:17And in the north of the planet, Mars Reconnaissance Orbiter spotted a clue.
10:27An impact crater, whose walls appear to be built from an intricate array of pillars.
10:47So perfect, they look almost engineered.
10:54They aren't, of course, the work of Martian sculptors.
11:01They're also found here on Earth.
11:09Just look at these beautiful geometric shapes.
11:14They look almost carved into the rock.
11:19They are a beautiful example of one of, actually perhaps in some sense, the most fundamental
11:27law of nature in action, the second law of thermodynamics.
11:34The second law of thermodynamics, put really simply, is that if you get a hot thing, high
11:38temperature, and bring it into contact with a cold thing, low temperature, then it is
11:44inevitable that energy will be transferred from the hot thing to the cold thing until
11:50they reach the same temperature.
11:52That's absolutely fundamental.
11:56That's what's happened here.
11:57The hot lava has come out from underneath the ground, that inner heat.
12:02It's met the cold atmosphere and it's cooled down.
12:06It's lost energy.
12:07And what's true here on Earth is also true on Mars.
12:15On both planets, the pillars started life as hot, molten rock.
12:24As the lava cooled, it contracted, causing cracks to form on the surface that then grew
12:30downwards, creating the symmetrical columns.
12:38They are a direct consequence of the second law in action, as the lava released enormous
12:44amounts of heat, ultimately, out into space.
12:53But the pillars on Mars are likely millions of years older.
12:59The flows that built them died, just as Mars' volcanoes did.
13:07Mars lost its inner heat far faster than Earth.
13:13The question is, why?
13:17Gosh, it's the single simplest invention in human history.
13:31If I'd have been the caveman, we wouldn't have even domesticated animals.
13:36Ah, success.
13:45Take one Earth-sized rock, add a smaller Mars-sized one, and roast for 30 minutes.
14:13These two rocks have been in the fire, they've been heating up.
14:18And I've just got them out of the fire at the moment, they're at the same temperature.
14:24You can see there, they're both about 200 degrees.
14:31But now I've removed them from the fire in accord with the second law of thermodynamics,
14:37they're going to start losing energy.
14:40So if we wait, then the rocks will cool down.
14:54Well now these two rocks have been out of the fire for about 20 minutes or so, and not
14:59surprisingly, they've cooled down, because they're in contact with a colder environment.
15:04The big one has cooled down to about 150, 155 degrees or so.
15:14But the little rock has cooled down way more.
15:17It's now only at a temperature of about 50 degrees or so, I can pretty much touch it
15:22with my finger.
15:25And that's because the small one is small, to be more specific.
15:32These rocks are losing heat to the environment through their surface area, and the small
15:36one has got much more surface area in relation to its volume than the large one.
15:44That means that it loses heat more quickly, it cools down.
15:48And this is exactly what's happened to Earth and Mars.
15:59Earth is large enough to have held on to much of its internal heat, but Mars' radius
16:08is about half that of Earth's.
16:12So since the glory days, when its volcanoes were raised on a scale seen nowhere else,
16:21Mars' inner heat has escaped, lost to the cold of space, bringing the grandest volcanism
16:29the solar system has ever seen, to an end.
16:46Size then sets a powerful limit on volcanic activity, yet the next volcano world seems
16:56to break this rule.
17:04Out beyond the asteroid belt lies the first of the gas giants.
17:20Jupiter commands its own system of moons, over 90 at the last count, including one that
17:31is truly unique.
17:38Io.
17:58NASA's Juno probe has been circling Jupiter since 2016.
18:07Its orbit taking it ever closer to Io.
18:18Its infrared camera saw a world consumed by fire, each bright patch a volcanic eruption.
18:34Right now, rivers of lava are pouring across its tortured surface.
18:43In places, the volcanic eruptions are so violent, they throw columns of gas and dust far out
18:53into space.
19:02Io is the most volcanically active world in the solar system, yet its radius is just over
19:11half that of Mars.
19:19Remember that scene in Alien, where John hurts and all the astronauts descend into
19:36the cave?
19:37And remember what happens to them?
19:39See, isn't that just a bit of that feel?
19:51The scale of volcanism on Io is hard to comprehend, to visualize, until you come to a place like
19:57this.
19:58Here's a photograph of the surface of Io, and you see all those colors, all those beautiful
20:04yellows and oranges.
20:06Now look at the walls of this cave.
20:09Same colors.
20:10And that's because these are the same chemical elements.
20:13It's elements like sulfur.
20:14Now, in this case, they were deposited on the walls of the cave when the magma seeped
20:19away around 5,000 years ago.
20:22But here, on the surface of Io, they're being constantly replenished.
20:27Look at the scale of it.
20:29Imagine that, all on a small world, no bigger than our moon.
20:37Its small size means that Io's heat of formation has long gone.
20:43Something else is fueling these fires.
20:50The giant planet that looms so large in its skies.
21:05Io orbits around Jupiter, and Jupiter, being a very massive planet, raises tides on Io.
21:11And that's pretty much the same mechanism by which the moon raises the tides on Earth.
21:16But Jupiter is extremely massive, and so the tides on Io are extremely violent.
21:23It actually raises the tides in the rock of something like 100 meters.
21:28It's not in water, it's in rock.
21:31It's about the height of this cavern.
21:35But Io's orbit is not circular, it's elliptical.
21:41So that means that the moon comes close to Jupiter and far away.
21:46Close and far away, at once every 42 hours.
21:51So that 100 meter rock tide is going up and down and up and down every 42 hours as Io
21:59goes around Jupiter.
22:01So imagine the friction as that rock tide rises and falls and rises and falls.
22:08That introduces immense amounts of heat into the moon.
22:12It's actually about half the energy that we know is needed to power the volcanoes.
22:21But it's only about half.
22:22So where does the other half come from?
22:25Well, that's where it gets really cool.
22:29So let's say Jupiter is there, and let's say that Io is orbiting around Jupiter.
22:39I'm going to exaggerate it a lot.
22:43Orbiting around Jupiter in an elliptical orbit.
22:48So Io is moving around like this.
22:53In an elliptical orbit, there are two foci.
22:57The cross out here in empty space, which we call the empty focus, and the other centred
23:03on the planet.
23:06And it turns out that Io, it can be shown that, that's what you say when I'm not going
23:12to show it because it's a load of mathematics, but it can be shown that Io is locked to the
23:19empty focus of the ellipse, the other focus, not the planet.
23:26The tide is raised by Jupiter's gravity.
23:30So that big sort of huge towering tide in the rock always points towards the planet.
23:38As Io goes around, that tide is dragged backwards and forwards across the face of the moon.
23:46So not only have you got this big hundred metre tide in the rock going up and down as
23:50it goes around, it's going side to side, being dragged backwards and forwards across
23:56the face of the moon.
23:58That also injects a tremendous amount of energy into the moon.
24:02And that's the other half of the energy that's required to power Io's volcanoes.
24:14These colossal tides are what enabled Io, despite its size, to become so violently volcanic.
24:24The friction may even have melted so much of the moon that there's a global ocean of
24:30magma just below the surface.
24:36But there's another twist to Io's tale.
24:51This is a series of photographs of Io taken a few months ago now, over a period of several
24:58weeks.
24:59And you see the volcanoes, you see all that activity there, hotspots switching on and
25:03switching off.
25:04This is an infrared photograph, so what you're seeing here is heat, which is a useless energy
25:10being radiated off into space.
25:13Energy is being removed from Io's orbit.
25:17Now, if you remove energy from an elliptical orbit, it gets more and more circular.
25:22And if the orbit was circular, then the tidal heating would die away, and the volcanoes
25:28would fall silent.
25:30So if all there was was Jupiter and Io, then Io would not look like that.
25:42Io's extreme activity should have killed off the tides that create its internal heat.
25:50So there must be something else beyond the squeezing of the moon, keeping its fires alive.
26:01Io is not alone in orbits around Jupiter.
26:03It's one of the four big moons known as the Galilean satellites.
26:08And Io orbits in what's called an orbital resonance with two of them, Europa and Ganymede.
26:14So here's Jupiter, and for every four orbits of Io, Europa goes around twice, and Ganymede
26:24goes around exactly once.
26:29That means on every fourth orbit, the moons line up, and they give a gravitational kick
26:35to Io.
26:36They put energy into the orbit, which keeps the orbit elliptical.
26:41And so, whereas here on Earth, the volcanoes are driven by the primordial heat down at
26:47the Earth's core, Io's volcanoes ultimately are driven by gravity.
26:59This bizarre volcanic moon, locked in a seemingly endless cycle of eruptions by its sister moons,
27:15is the furthest world from the sun, where we've seen molten rock erupting onto the surface.
27:30But, beyond Jupiter, another mission has encountered an entirely different type of volcano.
27:48Crossing the great gulf of space, we encounter the next planet.
27:59Saturn's rings loop for hundreds of thousands of kilometres through space.
28:14And just beyond them lies a glittering gem.
28:23A frozen moon, perhaps the last place you'd expect to find a volcano.
28:41Enceladus' surface is a hard mantle of frozen water at a deathly minus 200 degrees Celsius.
28:53On such a cold world, everything should be frigid, unchanging.
29:05Yet, in 2005, the Cassini probe witnessed an extraordinary sight.
29:23Explosive jets roar from the surface, reaching hundreds of kilometres into space.
29:38The largest volcanic plumes in the solar system.
29:43How are such epic eruptions possible, on a tiny frozen moon?
30:14Even on Earth, eruptions don't have to be molten rock.
30:33The geothermal activity so close to the surface here in Iceland,
30:39is kind of a double-edged sword.
30:44On the one hand, it can be dangerous.
30:48But here, that geothermal activity is also used for the benefit of the population of Iceland.
30:56Here you see thermodynamics in action.
31:00This is a power station.
31:02These two power stations in this region provide over 400 megawatts of power.
31:08That's enough to power Reykjavik, and also half its hot water.
31:13You can feel the energy, that primordial energy of the Earth,
31:18rising to the surface and heading off into the cold of the atmosphere.
31:23This is precisely what's happening out there on Enceladus.
31:31You do get a sense of the raw power,
31:36just sitting just a few, not far, in this case, below our feet, actually.
31:46But this is nothing compared to Enceladus.
31:52Where over 300 kilograms of water vapour and ice
31:58erupts every second from giant cryovolcanoes.
32:22It was Cassini that first spotted something odd about the motion of Enceladus.
32:30As it orbits Saturn, it wobbles on its axis
32:36by a very small, but it turns out very significant, 0.12 degrees.
32:52Consider an egg.
32:57Now, when you spin an object, so when an object spins on its axis,
33:02it rotates around what's called its centre of mass.
33:05And for solid objects, like this hard-boiled egg,
33:08if I spin it, it spins nice and evenly, uniformly.
33:16But now, look what happens if I take an egg that hasn't been hard-boiled,
33:22so it's filled with fluid.
33:24If I spin this, it wobbles all over the place
33:30because the fluid inside is sloshing around.
33:34Because this egg is raw, the shell and liquid inside
33:38move independently of each other when spun, making the egg wobble.
33:47So the reason that Enceladus wobbles is because it's not completely solid.
33:53And we now think, by high-precision measurements and simulations
33:57of exactly how Enceladus wobbles, that there is a global liquid ocean
34:02beneath the frozen, icy surface of Enceladus.
34:06And we infer that because the laws of physics that apply to eggs here on Earth
34:12also apply to moons.
34:20I mean, Enceladus isn't going to do that.
34:32So Enceladus has an outer shell of ice,
34:36sitting on top of a global ocean of water.
34:43But how is that water managing to force its way
34:48through five kilometres of solid ice?
34:55To find out, Cassini took a much closer look at the moon's south pole.
35:12Oh, wow. That's changed, hasn't it?
35:15It's changed. I don't know if it's changed for good or bad.
35:18Crikey.
35:21We found a really nice, relaxing place to explain some complicated physics.
35:27Now, here, about two kilometres down below my feet,
35:31there's a hot reservoir of water that's under pressure.
35:35Now, under normal circumstances, that couldn't escape.
35:39But we've drilled a borehole.
35:42And the moment that that borehole is present,
35:45then those pressure and temperature differences will equalise.
35:49And in this case, the water comes out of the borehole as superheated steam.
35:56Now, here is a photograph of Enceladus' south pole from Cassini.
36:00And you can immediately see there's something interesting here,
36:03interesting geology.
36:05Cracks in the thin ice of the south pole.
36:08These became known as the tiger stripes.
36:15They are revealed most clearly by Cassini's infrared instruments.
36:24The red shows freshly deposited ice crystals.
36:29Hints of activity along the entire length of the cracks.
36:34But the real insight comes when you measure their temperature.
36:40Because those tiger stripes are hot, really hot, compared to the surface.
36:46The surface of Enceladus is minus 200, maybe minus 220 degrees Celsius.
36:52These tiger stripes are at minus 80 degrees Celsius.
36:56You might say, well, it's still cold.
36:59It is cold, but it's a lot hotter than the surface surrounding those structures.
37:05And so what you can see here is high-temperature,
37:08high-pressure ocean beneath the surface.
37:11And there's a cold, low-pressure environment of space above.
37:16And there's a weakness here in the surface.
37:19That allows that gradient to equalise.
37:22It's exactly what you see there.
37:24Other than there, someone has drilled a hole down into the deep underneath the Earth.
37:30Whereas here, the ice happened to be thinner.
37:38We're not really sure why, actually.
37:40It could have been that there was some kind of impact here.
37:43But the upshot is the same.
37:45You get plumes of water, ice, in this case, erupting out into space.
37:55TIGER STRIPES
38:00The tiger stripes also create a window into Enceladus's interior.
38:08As Cassini flew through the plumes,
38:10it detected traces of molecular hydrogen and silicon dioxide,
38:17chemistry that most likely comes from ocean water
38:21interacting with hot volcanic rock.
38:27This suggests that the ocean beneath Enceladus's icy shell
38:31has something that on Earth we call hydrothermal vents.
38:47The discovery of active geology on Enceladus, I think, took everybody by surprise.
38:52Nobody expected to see it on such a small world.
38:55But there might be more to Enceladus than just geology.
38:59See, hydrothermal vents of the kind we think might be present on Enceladus
39:04are one of the prime candidates for the cradle of life on Earth.
39:10The reason is that if you think about what the origin of life has to offer,
39:14if you think about what the origin of life has to be,
39:17it has to be, in a sense, a transition from geochemistry to biochemistry,
39:22from active geology to active biology.
39:26So all the conditions seem to be present on Enceladus for the origin of life,
39:31and we don't even need to land or find some way of getting into that ocean
39:35to test that hypothesis,
39:37because Enceladus is throwing the evidence potentially out into space.
39:42All we need to do is fly a spacecraft through those plumes.
39:46So Enceladus has to be one of the prime candidates
39:50for exploration in the solar system
39:52to search for the origin of life beyond Earth.
40:01Enceladus is not the only world with cryovolcanoes.
40:13Even at the furthest planet from the sun...
40:20..we found evidence of them.
40:26Only one ship has ever made the journey.
40:38It was on one of Neptune's frozen moons
40:41that Voyager 2 caught a glimpse of recent activity.
40:57Its camera sent back images of dark smudges on Triton's face.
41:11Trails left by plumes erupting from its surface...
41:24..making Triton the most distant
41:27of the active volcanic worlds that we've witnessed.
41:42It seemed that the inventory of the solar system's
41:46active volcano worlds was complete.
41:53But recently, we found something we'd missed far closer to home.
42:12Venus is shrouded in thick clouds of sulphur dioxide...
42:22..making it very difficult to see the surface.
42:28So the spacecraft deployed here use radar
42:31to peer through the dense atmosphere.
42:42Magellan's radar imagery revealed Venus to be a hellish world.
42:49Its landscapes dominated by volcanoes.
42:54Over 85,000 at the last count.
43:02Including truly bizarre examples with deeply rutted sides...
43:09..and lines of flattened volcanic domes like chains of pancakes.
43:18But with only snapshots from orbit to go on,
43:22no-one knew if any of these volcanoes were active.
43:29Until, in 2023, a new analysis of the Magellan data
43:36revealed, on a volcano the size of Mount Everest,
43:41an eruption along its northern flank.
43:48Proof, after all, that there's activity
43:51on the most volcano-ridden planet in the solar system.
43:57So why does Venus have such strange and diverse volcanoes
44:02littered across its surface?
44:16A clue can be found in Iceland's remote volcanic interior.
44:22In 1783, in front of a period of eight months,
44:25one of the most catastrophic volcanic eruptions
44:28in human history happened here.
44:3315 cubic kilometres of lava emerged from these eruptions.
44:42And it's not just the lava.
44:46You see this, it's a remarkable landscape, a line of volcanoes.
44:51And they're really classic volcanoes,
44:54like a child has drawn a volcano.
44:59And then everywhere else that you look across this valley,
45:02it's just lava.
45:06The fact that such a violent eruption happened here
45:10is not down to chance.
45:19If I take a map of the Earth and draw all the volcanoes,
45:24then they form a very distinct pattern.
45:28So there's a line all the way down North and South America
45:32on the Pacific coast, and then the other side,
45:35all the way down North and South America on the Pacific coast.
45:39And then the other side of the Pacific,
45:41there's another line of volcanoes through places like Indonesia,
45:46down here in the Rift Valley, Tanzania and Ethiopia.
45:50And then there's a line of volcanoes through Iceland
45:54and actually under the ocean,
45:57down the middle of the North and South Atlantic.
46:00So there's a very distinct pattern here,
46:03and that's because the surface of the Earth is not just one big slab.
46:07It's carved up into plates.
46:10The Earth has what's known as plate tectonics.
46:13So here, for example, down the Pacific coast of North and South America,
46:18the Pacific Ocean crust, the floor of the Pacific,
46:22is moving down this way, underneath the continent.
46:27And you get eruptions, you get volcanoes.
46:30In the Atlantic, here, through Iceland, the opposite is happening.
46:35The Earth's crust is spreading.
46:38You can see it, actually. I'm sat on it.
46:41So over there in the west is North America, the North American plate,
46:46and over there in the east is the Eurasian plate.
46:50They're spreading apart here, literally here,
46:53and that's why there's a line of volcanoes moving down through here
46:58and straight onwards down into the South Atlantic.
47:02So Earth's pattern of volcanoes is telling us
47:05that there's what's called plate tectonics on the Earth.
47:10Now look at a map of the volcanoes on Venus.
47:15Look at that.
47:17It's absolutely covered, completely randomly,
47:20in pretty much every kind of volcano you can imagine,
47:24scattered across the entire face of the planet.
47:27And the reason for that is that there are no plate tectonics on Venus.
47:41We don't fully understand why Venus and Earth are so different.
47:48Why Earth developed plate tectonics and Venus didn't.
47:54But we do know that Venus's outer crust is much thinner.
48:04The planets Venus and Earth are roughly the same size.
48:07They probably started life with about the same amount of internal heat.
48:11But it's how the heat escapes that makes all the difference.
48:15So here on Earth, it escapes mainly at those boundaries between the plates.
48:21But Venus has a much softer and thinner crust, a lithosphere, than Earth.
48:26And so the heat can escape anywhere.
48:29And that's why you see this surface covered in a plethora of volcanoes.
48:40With less of a barrier, Venus's inner heat has built vast lava flows
48:47that run for thousands of kilometres.
48:57And we now think that at least one of its volcanoes,
49:01and we suspect many more, remain active to this day.
49:07But only further missions will reveal just how alive
49:11volcanoes on our sister planet really are.
49:37Our exploration of the solar system has shown us
49:40that there's active geology in the strangest and most unexpected of places.
49:45The ice fountains of Enceladus.
49:48The Galilean moons of Jupiter.
49:51Even the frozen atmosphere of Mars.
49:55And even the ice floes of Mars.
49:58And even the ice floes of Mars.
50:01The Galilean moons of Jupiter.
50:04Even the frozen outer moon of the solar system, Triton.
50:10But amongst all those geologically active worlds scattered across the solar system,
50:15it still remains the case that there's only one place where we know for certain
50:20that the active geology became biology.
50:23And that's here on Earth.
50:25And if that really is the case, if we're alone here on Earth,
50:29then I think that raises a deep and very profound question.
50:32It's why? What is so special, possibly, about this place?
50:44Wonderfully, at least part of the answer
50:48appears to be a consequence of plate tectonics.
50:53Volcanoes, when they erupt,
50:56emit huge amounts of greenhouse gases like carbon dioxide.
51:00And as we all know, greenhouse gases heat a planet up.
51:05Now, Earth has a natural regulatory system.
51:10When it rains, the carbon dioxide is dissolved in the water
51:14and falls on the ground.
51:19And the carbon dioxide reacts with the rock of the mountains to form minerals.
51:24Then plate tectonics can take those rocks
51:28and send them back down into the Earth.
51:32So there's a cycle from volcano to atmosphere
51:37to land and back into the interior of the planet.
51:49Over geological time, this wonderful relationship
51:53between volcanoes, plate tectonics and our atmosphere
51:57has kept Earth's climate in check.
52:06And that stability has helped sustain an unbroken chain of life
52:11that stretches back almost four billion years.
52:18It's only here on Earth that a range of geological processes
52:22from volcanoes to plate tectonics and hydrothermal vents
52:26have conspired together to produce an environment
52:30that not only allowed life to begin,
52:33but also was stable enough to allow life to flourish.
52:37From the simplest living organisms to the endless forms most beautiful
52:41that we see covering the surface of the Earth today,
52:45what is, how special is Earth?
52:49Well, I think the answer might be found in this giant laboratory,
52:53the solar system, in exploring the eclectic and diverse collection
52:58of worlds that we find orbiting the sun.
53:16The Solar System
53:27Current velocity is 145 meters per second
53:31at an altitude of about nine and a half kilometers above the surface.
53:37In February 2021,
53:41an astonishing new piece of hardware
53:45arrived on the surface of Mars.
53:53Perseverance is looking for evidence of ancient life
53:57which may have started on the planet
54:00thanks in part to its giant volcanoes.
54:07Volcanism played such an important role
54:11in the history of our planet,
54:15but also in the origin of life and evolution of life.
54:21Mars is like Earth's cousin.
54:25Very early in their history, if they had these volcanic activities,
54:29we found evidence that Mars had liquid water on its surface,
54:33it had a thicker atmosphere.
54:37So at that time, when life was emerging on Earth,
54:41Mars also was creating similar environments.
54:45So it's possible that there was the potential for life on Mars.
54:51Mars' volcanism faded away,
54:55and so did the water on its surface
54:59and the chance for life to flourish on the Red Planet.
55:05But if life did at least get started,
55:09crucial evidence could be locked in the Martian rocks,
55:13waiting to be discovered.
55:17Perseverance, or as team members called it, Percy,
55:21went to Mars, to a crater known Jezero,
55:25which used to be an ancient lake.
55:28Percy is looking for evidence
55:32about the habitability of this environment.
55:36We're looking for signatures that there was life on the planet,
55:40but it would be absolutely amazing if we actually found cells
55:44or something similar in these rocks
55:48that indicated that there is life on Mars today.
55:58As it makes its way across the dry lake bed,
56:02Perseverance leaves behind a series of small,
56:06carefully sealed rock samples.
56:10The plan is to analyse these in a lab here on Earth.
56:14But right now, they're stuck
56:18on the surface of Mars.
56:22Retrieving our samples from Mars
56:26is not going to be any easy task.
56:30First we have to land on the surface.
56:34Then we have to pick the samples up,
56:38make sure they're packed into the spacecraft,
56:42and make sure that the spacecraft gets back to Earth.
56:46So there's quite a bit of coordination that has to be done.
56:50The schedule is still uncertain.
56:54But NASA's hope is to return the canisters back to Earth
56:58in the mid-2030s.
57:02It's exciting to me because I study these rocks,
57:06and so this would be a unique opportunity
57:10for me to be able to do that.
57:14It's exciting to me because I study these rocks,
57:18and so this would be a unique opportunity to have samples
57:22directly collected from the surface that I could analyse.
57:26Being able to have samples from a planet is so much better
57:30than just having to look at a planet through a telescope
57:34or through data sent back by a spacecraft.
57:38So regardless of all the effort it's going to take to get the samples back from Mars,
57:42it's definitely going to be worth it.
57:46We will have a piece of Mars in our hands.
57:58Next time, we venture to the hidden realms of our solar system.
58:06The dark worlds.
58:10Where mysteries lurk in the shadows.
58:16And a distant hinterland
58:20sends unexpected visitors hurtling towards Earth.
58:46Music
58:50Music
58:54Music