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00:00Asteroids are the Earth's nemesis.
00:06They've blitzed our world for billions of years.
00:11This takes a few seconds to create.
00:1450,000 years ago was a very bad day for anybody living nearby.
00:18Yet asteroids are also a valuable resource.
00:23Giant boulders rich with valuable metals.
00:28I see miniature worlds with more fresh water than Earth.
00:34Ultimately, asteroids may be a stepping stone by which we can one day leave the entire solar system.
00:41Asteroids are planet builders.
00:44Without them, our world would not be here.
00:48We owe our very existence to these things.
00:51They are the givers and takers of life.
01:07The night sky is full of stars, galaxies, planets, and asteroids.
01:15Asteroid actually means star-like.
01:17They're the very best telescopes. They look like nothing more than just points of light in the sky.
01:22They're cosmic boulders, and there are trillions of them.
01:27From the size of a car to giants hundreds of miles across.
01:34Together, they tell the story of how we came to be.
01:40The Earth was made by asteroids.
01:48Four and a half billion years ago, the solar system is a vast cosmic whirlpool.
01:58Dust sticks together to create asteroids.
02:04In our own solar system, and in every solar system, the first objects to form,
02:08the first large rocks before planets form, are essentially asteroids.
02:13There are no planets yet.
02:17Instead, trillions of rocks and stones swirl around the newly born sun.
02:25It would have been a very strange place, kind of like a merry-go-round of all these objects orbiting around the sun.
02:32And there are millions of these asteroids that are just in different sizes and different shapes.
02:38These ancient asteroids will shape the solar system and build the planet we live on.
02:47Asteroids are so much more than just rocks in space. They're the building blocks of our very own planet.
02:55Billions of small asteroids must clump together to make a planet.
03:02But asteroids move at thousands of miles per hour.
03:09Getting them to stick is hard.
03:16We're here at the stock car race. See what the early solar system may have looked like.
03:23High-speed car collisions cause damage.
03:28Parts smash off.
03:31Asteroid collisions are the same.
03:35To join together, somehow, they must collide and stick.
03:42Stock cars show how this happens.
03:46They move fast, but all in the same direction.
03:51Just like the asteroids in the early solar system.
03:57When collisions happen, they're relatively gentle.
04:03Instead of smashing apart, they join together.
04:09These are planets in the making.
04:13They're going around almost at the same speed.
04:16And they begin to stick together, and that's how planets begin to form.
04:22Asteroids gather into rock piles.
04:27Like two cars locked together.
04:32As more asteroids collide, the rock piles grow.
04:38Building whole planets this way would take billions of years.
04:44Yet the planets formed in just a few million years.
04:49How?
04:51When the rock piles reach mountain size, gravity speeds up the process.
04:58Gravity started to become important when they were about the size of one of the Rocky Mountains, like Pikes Peak behind me.
05:04It was when they were several miles across that they had enough mass that their gravity could start to draw material in.
05:11Now, if the Earth weren't here, and it were just Pikes Peak over there a few miles away,
05:15I would very slowly start to drift toward it, faster and faster, accelerating the whole way, until I actually impacted it.
05:22The gravity would draw me in, it would pull on me, until I actually hit the mountain itself.
05:30Large asteroids are mountains in space.
05:36The early solar system is full of them.
05:40And their gravity pulls other asteroids toward them.
05:47The larger an asteroid becomes, the more rocks it pulls in.
05:53And the faster it grows.
05:56At that point, the events happen very quickly.
05:59It would actually draw that stuff in and grow very rapidly.
06:03One of these early space mountains keeps on growing, until there are no rocks left to pull in.
06:13It's no longer an asteroid.
06:16It's a young planet.
06:19The Earth.
06:22All of the planets, even the Earth, they owe their existence to the fact that there were asteroids back then.
06:30This is how all rocky planets form.
06:34Asteroids join together until there are no more left.
06:40Mercury, Venus, Earth, and Mars are all overgrown asteroids.
06:52But beyond Mars, something went wrong.
06:57No rocky planets.
06:59Instead, billions of rocks and boulders that never joined together.
07:06The asteroid belt.
07:12Out here, construction came to a halt before a rocky planet could form.
07:19Because of Jupiter.
07:23The gas giant had already formed nearby.
07:29Jupiter is humongous.
07:31It's the 800 pound gorilla.
07:33It dominates everything gravitationally.
07:36Four and a half billion years ago, Jupiter's gravity causes havoc.
07:43It flings asteroids in every direction.
07:48Giant boulders scatter from their regular orbits onto extreme, chaotic paths.
07:57The stock car race ends, and the demolition derby begins.
08:05Once Jupiter had gotten formed, the solar system began to look like a demolition derby.
08:10Things colliding with each other, going in all sorts of different directions.
08:16A cosmic pileup.
08:19Rocks smash into each other from every direction.
08:23Violent, chaotic collisions.
08:28These rocks don't clump together.
08:32They shatter and create the asteroid belt.
08:39Violent collisions still rock the asteroid belt today.
08:44In 2010, the Hubble Space Telescope captured this.
08:51The aftermath of a hypervelocity collision.
08:58Asteroids can both create and destroy.
09:03If many of them come together gently, you get planets.
09:08Too much violence, and you get the asteroid belt.
09:14Billions of rocks and boulders.
09:17A graveyard for a planet that never formed.
09:23The asteroid belt is a mysterious realm, full of danger and full of promise.
09:33A new frontier just waiting to be explored.
09:50Asteroids are as diverse as planets or moons.
09:56Some are metallic.
09:59Some rocky.
10:01Some icy.
10:06Some even have their own moons.
10:11They come in all shapes and sizes.
10:16From boulders, all the way to miniature worlds.
10:25And they're everywhere.
10:28Distant solar systems have their own asteroid belts.
10:34The star, Epsilon Eridani, is just 10 light years away.
10:40It has not one, but two asteroid belts.
10:46Another star has a belt 25 times larger than our own.
10:52If you're actually living on a planet in that solar system,
10:55the asteroid belt would look like a much brighter than the Milky Way,
10:59a big streak across the night sky.
11:02Asteroid belts are the scraps left over after planets have formed.
11:08So they tell us a lot about their solar system.
11:14Our asteroid belt is full of variety.
11:19Millions of strange asteroids.
11:23Each with a story to tell.
11:27Yet we have barely explored it at all.
11:32That's about to change.
11:36The first mission to the asteroid belt is underway.
11:41The Dawn Probe.
11:44Its goal? To explore a mysterious, distant realm.
11:51We're going to learn more about the main belt asteroids from this one mission
11:54than we will have since we've discovered the asteroid belt in the first place.
11:59In July 2011, Dawn arrived at its first target.
12:05And sent back these pictures.
12:10Vesta is the second largest asteroid in the belt.
12:15It almost became a planet.
12:19Then Jupiter's massive gravity stunted its growth.
12:25Today, it's a miniature world.
12:29One of the common misconceptions about the asteroid belt is that things are fairly small.
12:33But some of the largest asteroids are really more correctly thought of as minor planets.
12:38They're several hundred miles across.
12:41Vesta even has a mountain three times higher than Everest.
12:47Mark Sykes is co-investigator of the mission.
12:52It's just a real excitement because you're seeing a new world for the first time.
12:57And you know just enough to be dangerous in trying to explain what it is that you're seeing.
13:02Vesta is like a snapshot of the infant Earth.
13:07When it was just as wide as Arizona.
13:12We're seeing perhaps what an embryonic, early terrestrial planet like Earth looked like
13:19in the first few million years of its history.
13:25The Dawn probe has already found that Vesta has an iron core like the Earth.
13:32Evidence that the Earth's core formed when the planet was still young.
13:40This stunted world offers us a window on the Earth's distant past.
13:48We're seeing things that we didn't necessarily expect, but that's what makes it fun.
13:56After Vesta, the Dawn mission will head into the asteroid belt's outer reaches
14:03to explore an icy, primeval world four times bigger than Vesta.
14:13There, Dawn aims to settle another mystery about the Earth's past.
14:22Where did our oceans come from?
14:34The asteroid belt is ancient, violent, and remote.
14:41Hundreds of millions of miles from Earth.
14:46But not all asteroids stay in the asteroid belt.
14:52They can roam all over the solar system.
14:58The Moon's surface records a violent past.
15:03A massive, cosmic bombardment.
15:07We see evidence every night when the Moon comes out.
15:11What do we see? A pockmarked, barren world.
15:14Evidence that there was an intense rain of asteroids and debris that came from outer space,
15:20completely disfiguring the surface of the Moon.
15:26Millions of craters cover the Moon,
15:30including the largest in the solar system,
15:351,500 miles across.
15:39Itself scarred by thousands of smaller craters.
15:45A storm of asteroids blasted the Moon four billion years ago.
15:53And if that happened to the Moon, it must also have happened to Earth.
16:01The Earth is a much bigger, more massive target in space.
16:05For every one of those craters you see on the Moon,
16:07you've got to imagine 50 or 60 craters here on the planet Earth.
16:14The impacts back then must have been horrendous.
16:18Within a few weeks, a gigantic object hurling from outer space,
16:23gouging out a huge chunk of the planet Earth.
16:28We call it the Late Heavy Bombardment.
16:34For 200 million years, fireballs rain from the sky.
16:44The impacts trigger earthquakes bigger than any in recorded history.
16:5210,000-mile-per-hour hurricanes rip through Earth's primitive atmosphere.
17:04But asteroids also bring a new substance to Earth.
17:10Some asteroids contain ice, frozen water that melts on impact.
17:20Each asteroid brings a little more.
17:26But could asteroids really bring enough water to cover two-thirds of our planet?
17:33One of the questions we have is, how did water get to the Earth?
17:36Because the original Earth, we think, was very hot and very dry.
17:41NASA's Dawn probe aims to find out.
17:46The asteroid belt still contains icy asteroids to this day,
17:52in the coldest, most distant part.
17:57In 2015, Dawn will arrive at the solar system's largest asteroid, Ceres.
18:05Ceres is one-third the mass of the entire asteroid belt
18:09and four times as large as any other known asteroid.
18:13A lot of it looks like pure ice.
18:19Ceres has a rocky interior and ice-rich mantle.
18:24It's far enough away from the sun, it's cold enough, that it's stable.
18:30Ceres is just 600 miles wide.
18:34Yet there may be more frozen water here than all the fresh water on Earth.
18:42The Dawn mission will find out for sure.
18:47If Ceres really does hold so much ice,
18:51it could help explain why the Earth has so much water.
18:58When asteroids bombarded the Earth four billion years ago,
19:05massive icy bodies like Ceres could have brought vast amounts of water.
19:13Water itself, in the form of ice, came down from the heavens
19:17to create the lush oceans of the Earth.
19:22And not just the oceans.
19:25Clouds, rivers, glaciers may all have come from space.
19:35The Dawn mission may uncover something even more significant on Ceres.
19:42It may find an ocean underneath the ice,
19:48an inner mantle of liquid water,
19:51melted by heat from the dwarf planet's core.
19:58Life as we know it depends on water.
20:02Wherever we find water, we may find the spark of life.
20:09If there is a liquid water ocean underneath the surface today,
20:12that begs the question of whether there could be life there.
20:15Extraterrestrial life could have started in the asteroid belt.
20:24Ceres could be home to basic life forms,
20:28flourishing in a subsurface ocean.
20:37If asteroids like Ceres can support life,
20:42that could reveal how life started on Earth.
20:48Four billion years ago, asteroids bombarded the young Earth.
20:57They brought water, and they may have brought life.
21:05From the asteroid belt to Earth's new oceans,
21:12primitive organisms that thrived and ultimately evolved
21:17into all the Earth's creatures.
21:22A planet that brims with life.
21:27Our earliest ancestors may have arrived from the asteroid belt.
21:34Perhaps these little worlds could be incubators of life
21:37throughout our solar system,
21:39maybe even in other solar systems around other stars.
21:44Asteroids may bring life to worlds throughout the universe.
21:50They may also bring death.
22:02Asteroids are crucial to life in the universe.
22:07But once life gets started, asteroids can also end it.
22:15Asteroids really have two sides to them.
22:17They're sort of creation and destruction all wrapped up together.
22:20Planet Earth is right in the firing line.
22:24We've come to realize in recent years
22:26that we live in this kind of a cosmic shooting gallery.
22:30Astronauts witness this firsthand.
22:34When I flew on Apollo 9 and I went outside the spacecraft,
22:38it's very likely that I was hit by a very, very small asteroid.
22:44And it will make a hole in a space suit.
22:48Most objects in the Earth's vicinity are tiny,
22:53but they move at thousands of miles per hour.
22:58So the suits are very, very well built,
23:01the result of which is they're very heavy.
23:03But, you know, we've never had one penetrated yet.
23:08The Earth, too, has built-in protection from small asteroids.
23:15The atmosphere.
23:18When asteroids hit the atmosphere, they burn.
23:22I can remember one night when we were looking down at the dark Earth,
23:26and I kept thinking I saw an occasional flash of light, but I wasn't sure.
23:32And then suddenly we're realizing, of course, you know,
23:35we're looking at shooting stars.
23:43Most people don't realize that on a given night,
23:45if you lie in the grass and look up at the night sky,
23:48you'll see shooting stars, many of them each hour.
23:53Most shooting stars are the size of grains of sand.
23:59These burn up.
24:03But larger space rocks can punch right through to the ground.
24:10Here's the proof.
24:12Meteor crater in Arizona.
24:16Gouged out by an asteroid just 150 feet across.
24:23You can see the huge force that excavated this,
24:26and you can also see the layers of material that were turned over
24:31as the crater was excavated.
24:34And so some of these rocks around here are kind of upside down from where they started.
24:41There have been millions of impacts like this in Earth's past.
24:47There will be more.
24:50Imagine a city where Meteor Crater is now.
24:55You'd see a fireball coming through the sky very quickly.
24:58You know, this thing is moving at eight miles a second,
25:01and so it wouldn't take very long for it to move across the sky and strike the ground.
25:07Heat from the fireball scorches the surface,
25:11but most damage comes after the impact.
25:17Once it strikes the ground, this takes a few seconds to create.
25:21So very short time, very large amount of energy, and very devastating effects.
25:28The asteroid is obliterated.
25:32A mighty shock wave generates winds six times more powerful than a hurricane.
25:40You have the blast that comes out, probably for several miles,
25:44a large debris that would crush buildings and homes.
25:51If it hit today, the asteroid from Meteor Crater would be a city killer.
25:58But the Meteor Crater asteroid was small.
26:04It was likely a fragment from a much larger asteroid.
26:10Whatever it is that hit in Meteor Crater wasn't very big.
26:14It was probably 50 yards across, so not even as big as a football field.
26:20There are millions of much larger asteroids.
26:24These would cause even more carnage, country killers, and worse.
26:34Asteroids over a half mile wide could end our civilization.
26:40Worldwide killers.
26:43We know because it happened already.
26:52There are traces everywhere.
26:57There's evidence of giant impacts all over the world,
27:00and it's right underneath your feet.
27:02In fact, in some places, it's pretty easy to spot.
27:09Like here in southern Colorado.
27:17So this layer of light-colored rock, that's the K-T boundary.
27:22It's called a boundary because it marks the boundary between two different time periods.
27:27Everything that was put down here, underneath the K-T boundary, had dinosaurs in it.
27:32Everything above it, no dinosaurs.
27:35So it really marks that point in time when the dinosaurs went away.
27:42The layer is rich in an element called iridium.
27:47It's rare on the Earth's surface, but common in asteroids.
27:53So if a giant asteroid came in, smacked into the Earth, blew out dust everywhere,
27:59the iridium inside the asteroid would have settled down into a layer all over the Earth,
28:03and that's exactly what we see right here.
28:08The clear fingerprint of an asteroid.
28:12There must have been some perfect morning before the asteroid impact,
28:16when the land of the dinosaurs was still very much as it had been for millions of years.
28:20Then there would be something sighted up in the sky, something very bright, very hot.
28:26The asteroid is six miles long, big enough to devastate the planet.
28:35The asteroid that came in and formed this layer here was very massive and was moving very fast.
28:40And so when it impacted the Earth, that energy was turned into boom, very, very big boom.
28:50It has the force of five billion Hiroshima bombs.
28:55Large pieces of Earth blow out into space.
29:01Then rain back down.
29:04A storm of fireballs.
29:08Wildfires rage across the globe.
29:16In the K-T boundary layer is a layer of soot.
29:20And that's an indication that there were global fires,
29:23that everything on Earth was basically on fire after this happened.
29:29The Earth plunges into darkness.
29:34An impact winter.
29:37Mass extinction.
29:41Basically you can think of this as every environmental catastrophe all happening at the same time.
29:46It was an incredibly bad day for planet Earth.
29:49A chilling reminder of the threat from space.
29:55Asteroids this big will hit us again.
30:01We will go the way the dinosaurs.
30:03We will be survived most likely by the bugs, the cockroaches.
30:08They will be the ones who will inherit this Earth.
30:11But hopefully that's going to be a long time from now.
30:15Is mankind doomed?
30:19Or can we dodge fate?
30:23NASA Jet Propulsion Laboratory, California Institute of Technology
30:30Asteroids built our world.
30:36They brought water.
30:39They killed the dinosaurs.
30:44And made room for new species.
30:49But asteroids are also a threat.
30:56We know absolutely for certain that there will be large impacts in the future.
31:00So it's not a question of if, it's only a question of when.
31:03Large meteor impacts happen once every 60 to 100 million years.
31:08We're due for one soon perhaps.
31:11If we want to survive, we need to prepare.
31:17We must find the asteroids.
31:20Determine if they're heading for Earth.
31:24Then stop them.
31:27That's not easy.
31:29But it may be possible.
31:32Happily there's a difference between us and dinosaurs.
31:34We have telescopes.
31:36And we can get advanced notice of an impact.
31:42But asteroids are much smaller than stars and planets.
31:47It's hard to see them coming.
31:52To track asteroids, you need a giant telescope.
31:58Like the Arecibo Observatory in Puerto Rico.
32:04Right now I'm on top of the largest telescope in the world.
32:07And this place may actually be our best defense
32:09against getting hit by one of these near-Earth asteroids.
32:14The vast bowl is 1,000 feet across.
32:20And it's not only the world's biggest telescope.
32:24It's also the world's biggest radar dish.
32:28When you think about using radar to keep track of all the airplanes that are up in the sky,
32:32well, this one is so powerful, it can actually track near-Earth objects millions of miles away.
32:39Unlike a telescope, radar can directly measure an object's distance.
32:45And reveal exactly where it is.
32:49That's perfect for tracking asteroids.
32:54In 2004, astronomers spot a stadium-sized asteroid heading toward Earth.
33:03Its name, Apophis, after the Egyptian god of destruction.
33:12The day it might hit us, April 13, 2029.
33:19Friday the 13th.
33:23Apophis was the first near-Earth object of the modern era that had astronomers honestly scared.
33:27There seemed to be a 1 in 30 chance of something catastrophic happening.
33:32Arecibo springs into action against the biggest threat from space ever detected.
33:41Apophis could devastate entire countries.
33:46But the asteroid's path is still uncertain.
33:50It might hit, or it might just miss.
33:55Only Arecibo can tell us for sure.
33:59The Arecibo telescope was able to reduce the uncertainty of Apophis by 98%.
34:04It told us that there was no chance this thing would hit us in 2029.
34:12It will be close.
34:15Apophis will pass closer to the Earth than the Moon.
34:20Closer even than some communications satellites.
34:29We have powerful tools to detect asteroids.
34:35Someday we'll find one that will hit the Earth.
34:40How can we protect ourselves?
34:44The obvious strategy is to destroy the asteroid before it destroys us.
34:51But that could be risky.
34:54You don't want to blow it up because you may end up breaking it into two or three or five pieces,
35:00which then end up hitting all around the Earth and wiping out many, many people.
35:07Exploding an asteroid could cause more harm than good.
35:13Better to make it miss completely.
35:17When an asteroid is headed for Earth, their future paths cross.
35:24And they'll both reach that point at the same time.
35:30Imagine the Earth is a freight train and the asteroid is a car,
35:38both heading for a railroad crossing.
35:42If they reach that crossing at the same time, they will collide.
35:48The best way to avoid the impact is not to swerve away from the train.
35:54It's to hit the gas or the brakes.
35:58If you can cross the tracks before the train gets there,
36:01or wait for the train to pass and then cross them,
36:04that's what we want to do with asteroids,
36:06just to make sure that the asteroid and the Earth aren't at the same place at the same time.
36:18By simply slowing down the car, we're going to miss.
36:22That's the way to avert a collision.
36:27But asteroids don't come with brakes.
36:31We need another way to change their speed.
36:37One approach is to use the asteroid's gravity.
36:42For a small enough asteroid, all you need to do is park a large spacecraft next to the asteroid.
36:49A spaceship would hover above the asteroid's surface.
36:54You can thrust with your spacecraft to keep it from falling onto the surface of the asteroid.
36:59And so it's like a little gravity tractor, using gravity as the tow line to move the asteroid out of the way.
37:05Over time, the gravity between them would slow down the asteroid just enough for it to miss the Earth.
37:17Asteroids could shape our future in another way.
37:22We could turn them from a deadly threat into a precious resource.
37:43Asteroids are a creative force.
37:47They build planets.
37:49They bring water.
37:52But they're also destructive.
37:56Asteroids are both a boon and a threat.
37:59Early on, they bring the materials for life.
38:01Later on, they can destroy life.
38:03Asteroids bring violence and death.
38:07But life may not always be in danger.
38:12Ultimately, if life becomes intelligent enough, it could send objects out to deflect or destroy the impending asteroids.
38:21We now have the technology to divert asteroids.
38:26That means we can treat them not as a threat, but an opportunity.
38:33We could mine them.
38:36Many of them are just ripe for the taking in these wonderful mineral resources.
38:39And so the asteroids in some ways are literally gold mines in the sky.
38:43They're not just gold mines.
38:46They're zinc mines, aluminum mines, platinum mines.
38:53Just one average-sized asteroid could contain minerals worth thousands of billions of dollars.
39:03But first, we have to reach the asteroids.
39:10On April 15, 2010, President Obama announced a new plan.
39:20By 2025, we expect new spacecraft designed for long journeys to allow us to begin the first ever crewed missions beyond the moon into deep space.
39:32We'll start by sending astronauts to an asteroid for the first time in history.
39:38Ironically, the easiest asteroids to reach are the same ones that threaten the Earth.
39:49As they pass by, a spaceship could rendezvous with the asteroid.
39:56Yet even when asteroids come so close, asteroid mining may be too good to be true.
40:05The reason why we're not mining the asteroid belt today and letting the space program pay for itself is because of cost.
40:14It takes an enormous amount of rocket fuel and expertise to bring back an asteroid from outer space.
40:22But perhaps we don't need to bring the minerals back to Earth.
40:28We could use the resources of asteroids to build settlements out in space.
40:37You don't have to build a space station. It's already there.
40:42You don't need shielding because you can simply drill right into the soil and use the rocky material as shielding against radiation and micrometeorites.
40:52So in some sense, think of an asteroid as a ready-made space station.
40:58Low gravity makes it easy to come and go.
41:03There's plenty of water and all the construction materials that colonizers could ever need.
41:15So one day when we have colonies in the asteroid belt and we need to build cities there,
41:21that's where we're going to find valuable deposits of metals in the asteroid belt itself.
41:28A vast band of cities in space, strung across a billion miles.
41:37And not just cities, but factories to turn metal from the asteroids into spaceships.
41:47Perhaps asteroids could actually provide the metal, the real structure to build our spacecraft.
41:52So somewhere up there between Mars and Jupiter, there may be the makings of our future spaceships.
41:58Ultimately, asteroids may be a stepping stone by which we can one day leave the entire solar system.
42:06Asteroids made the Earth.
42:10Perhaps they even brought life here.
42:14And in the future, asteroids could help humans escape the Earth and colonize the galaxy.
42:26So in a way, asteroids are drawing us out into space, whether to protect ourselves or to expand where we live.
42:38Advanced civilizations all over the universe may use asteroids as stepping stones to the stars.
42:51Mankind may soon enter the Age of Asteroids.