If a massive asteroid collides with Earth, it could end life on the planet as one knows it; new discoveries reveal just how close civilization is to apocalypse and what it would take for the world's leading space agencies to stop it.
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LearningTranscript
00:00:00a dangerous asteroid is heading towards earth it's the size of the Empire State Building
00:00:09and it's traveling at 16,000 miles an hour it's called Apophis after the Egyptian god of chaos
00:00:19it will fly close to us in 2029 it won't hit us this time but when it returns
00:00:29in 2068 that could be another story if it blows up over a city millions of people will die
00:00:38this could be the most devastating single event in US history earth is stuck in the crosshairs of a
00:00:48potential asteroid strike Apophis is one of around 2,000 potentially hazardous asteroids
00:00:55that present a real and present danger asteroids have hit us before and they will hit us again
00:01:04as far as cosmic dangers go they're number one on the list this is not a drill if we do nothing
00:01:16this is our future
00:01:21December 2018 the US military detect a huge explosion in the earth's atmosphere
00:01:45high over the Bering Sea off the coast of Alaska when an explosion of this magnitude is detected
00:01:55everyone's mind goes to the same thing nukes but when the real answer was found and it was determined
00:02:02that it didn't even originate from earth that was even more shocking the cause of the blast an asteroid
00:02:09this asteroid was 30 feet across something like that over a thousand tons but it was moving at 20 miles
00:02:19per second over 70,000 miles an hour this asteroid was small and it exploded in the atmosphere over the ocean so nobody was hurt
00:02:30but if it had been bigger or it had come in over a different place or it had been moving a lot
00:02:39faster this could have been a dangerous object but the scariest thing about it is that we didn't see it
00:02:45coming
00:02:51so far we've been lucky
00:02:54but near misses happen all the time
00:02:57about once a year we get something the equivalent of a nuclear bomb going off in our atmosphere and
00:03:07while that sounds horrible most of these happen tens of miles up over open ocean where we go on completely oblivious
00:03:19we may be oblivious to most of the threats from space
00:03:25but they are very real we're going to get hit over a certain amount of time an asteroid impact is inevitable it will happen 100% absolute certainty
00:03:40NASA considers the threat from the skies so severe it has made protection from asteroids a top priority
00:04:01these events are not rare they happen and of course it's up to us to make sure that we are detecting and characterizing tracking all of the near-earth objects that potentially could be a threat
00:04:16this is not about Hollywood it's not about movies this is about ultimately protecting the only planet we know right now to host life and that is the planet Earth
00:04:28to help plan protecting our home we carry out Earth defense simulations
00:04:35for three days 200 scientists at the planetary defense conference battle a simulated asteroid 20 times larger than the Bering Sea space rock
00:04:47we practice all right what if this hits a major city what would we need to do
00:04:54by running potential impact scenarios we can prepare for a real asteroid strike
00:05:01this is like a fire drill that you would do at school or at work where you practice and think about
00:05:07okay what if where are the exits how do I get out how fast do I get out
00:05:11the drill starts with the discovery of a simulated earthbound asteroid
00:05:18so the first information is there's a big asteroid coming towards the earth then we get a better estimate of how big it is how fast it's going and where it's going to hit
00:05:30the asteroid is heading straight for earth with Denver Colorado in its sights
00:05:35the planetary defense scientists send up a simulated spacecraft to smash into the asteroid and push it off its path
00:05:45but it's a big gamble you can push it the wrong way you can potentially have unintended consequences
00:05:58in the simulation the spacecraft strikes the asteroid
00:06:03deflecting it away from earth but the impact dislodges a 200-foot chunk which is now heading straight towards the eastern seaboard
00:06:14so there's this one last piece that is now going to hit New York
00:06:20we know that something that size is going to have citywide consequences
00:06:27that is huge that's a horrible impact
00:06:31when you're actually in the conference room and you understand eventually that New York City is going to be destroyed
00:06:37and you're having strategies about how to evacuate people all the timing
00:06:41when you're doing the simulation you're in your head you're thinking about these things you're trying to reason them out
00:06:46but can you imagine the feeling in your gut in your heart if this was real
00:06:51if this were real the chunk of asteroid would strike Earth's atmosphere at 43,000 miles an hour
00:06:58as the space rock hurtles down it collides with molecules in the atmosphere which buffet the falling rock
00:07:11it's kind of like doing a belly flop into a pool right you're going from the vacuum of space into the dense lower atmosphere in mere seconds
00:07:19and that's an incredible amount of pressure to put on the object
00:07:24the asteroid slams into the air ahead of it compressing it violently
00:07:30the surface of the asteroid gets hotter and brighter
00:07:34it's actually the air itself that's glowing luminously from the heating of the shockwave
00:07:39the world's most intense sonic boom if you will
00:07:42that heats the air to incandescence as the object passes through
00:07:46so that's the source of that brilliant illumination
00:07:50this bright burning asteroid is called a bolide
00:07:55we witnessed one descending over the Russian city of Chelyabinsk in 2013
00:08:00all of a sudden there was a huge fireball streaking through the sky
00:08:04and people had no idea what they were witnessing because it looked like the sky was on fire
00:08:09it was insanity
00:08:12as the asteroid descends the compression of the denser air beneath it starts to flatten and even disrupt the falling rock
00:08:21there's a high pressure on the front there's no pressure on the back and it's being super heated
00:08:27and that intense temperature causes the air to glow which is how we see the streak of a meteor
00:08:33and it also disintegrates the asteroid itself it's hot enough to literally melt rock
00:08:39this can often lead to them exploding
00:08:42the combination of heat and pressure invade the falling asteroid causing it to blow up
00:08:48most asteroids don't reach the ground before they completely disintegrate in a tremendous release of energy
00:08:57this is what we call an air burst and we learned a lot about these while we were testing nuclear weapons after world war 2
00:09:03some of these bombs were blown up underground and on the ground but they found out when they blew up bombs above the ground
00:09:12it actually did more damage it was more widespread damage
00:09:15the explosion of the chelyabinsk asteroid sent out a powerful shockwave at thousands of miles an hour
00:09:22the blast traveled over a hundred miles
00:09:29it damaged seven thousand buildings and put fifteen hundred people in the hospital
00:09:34all of the injuries pretty much came from people who saw oh what's that bright flash in the sky
00:09:40the sky and they came close to a window to look and see what it was and then the pressure wave hit and blew glass in their face
00:09:47the chelyabinsk asteroid was only 65 feet across
00:09:54the rock in the defense simulation is three times more massive and it's heading straight for New York City
00:10:03imagine what would happen if an explosion a thousand times greater than that over Hiroshima hit New York
00:10:10we're talking about an utter complete destruction of the city and millions of people
00:10:18with so little warning the only option would be to evacuate New York City
00:10:24how do we get everybody out of New York City within just a few days
00:10:30that's where panic sets in that's where fear would really become the dominant emotion
00:10:35anyone left in New York City would see the bolide racing in
00:10:45followed by a blinding light
00:10:47as the asteroid explodes above the city
00:10:50the blast would be equivalent to the largest nuclear weapon ever detonated on earth
00:10:58buildings would be flattened melted there would be fires for miles around
00:11:04in the first moments of the explosion a million people could be killed instantly
00:11:09and many more would die later in the rubble in the ruins of what would happen there
00:11:15everything within nine miles of the blast epicenter would be completely destroyed
00:11:21the intense heat and pressure would wreck buildings
00:11:33it's the worst possible day for New Yorkers and not just the city itself
00:11:39there's something like 15 million people living in the New York area
00:11:44the shock wave would race out over 250 square miles
00:11:51this would certainly be the worst disaster that the US has ever experienced
00:11:56we're talking about millions and millions of people
00:11:59displaced affected within an instant
00:12:02this scenario is just a simulation
00:12:12for now
00:12:18the asteroid Apophis is heading our way
00:12:22if it hits earth
00:12:25it might not just kill a city
00:12:27it could kill a whole region
00:12:30it could kill a whole region
00:12:31I wouldn't exactly want to be there when that happens
00:12:33I want to be very very far away
00:12:38Apophis will skim earth in 2029
00:12:43but its path could change
00:12:46possibly turning a future miss into a direct hit
00:12:50April 13th, 2029
00:12:57a speck of light races towards the earth
00:13:11it's an 1100 foot wide asteroid called Apophis
00:13:14we are about to have an extremely close shave
00:13:25it's the closest approach of any asteroid that didn't actually hit us
00:13:30for a long long time
00:13:32it will be 10 times closer than the moon itself
00:13:35it will be so close it will be brighter than some stars
00:13:39the football stadium sized Apophis will race over the Atlantic
00:13:46if it were sitting on the surface of the earth
00:13:48it would weigh about 50 million tons
00:13:50something like that
00:13:52and that is not the place you want it to be
00:13:55you want it to be in space and far away
00:14:00when we discovered Apophis in 2004
00:14:03we thought it might be on a collision course with earth
00:14:06with a potential impact
00:14:08greater than the largest atomic bomb ever exploded
00:14:13the largest nuclear device
00:14:15atomic device ever detonated on our planet
00:14:17was the Tsar Bomba bomb in Russia
00:14:19so something like 55 or 56 megatons
00:14:22when Krakatoa exploded in 1883
00:14:26that was something like 200 megatons
00:14:28Apophis impact would be 450 megatons
00:14:31if something like that were to happen over New York City
00:14:34or Washington DC
00:14:36you're going to lose the city
00:14:40the impact would be at least 10 times greater
00:14:42than the simulated asteroid strike on New York
00:14:53when you put it in those terms
00:14:55that's just plain scary
00:14:58in a word
00:14:59an impact from an Apophis sized asteroid would be bad
00:15:04very, very bad
00:15:07Apophis's orbit will cross earth
00:15:09every seven years this century
00:15:12it won't hit us in 2029
00:15:14but this close encounter
00:15:16could change Apophis's orbit
00:15:18when a small asteroid encounters a bigger body like a planet
00:15:24it's like a bunch of roller derby players
00:15:30most of them are clumped together
00:15:32but maybe there's one just on their own particular orbit
00:15:35and as they circle around
00:15:37as they get close to that larger clump
00:15:39there'll be some interactions
00:15:41potentially violent interactions
00:15:42that will change the future trajectory of that lone roller derby skater
00:15:48and the next time around
00:15:50it might be a wide miss
00:15:52or it might be a head on impact
00:15:55it's the same in the solar system
00:16:00the combined gravity of the earth and moon
00:16:03creates what's called a gravitational keyhole
00:16:07a gravitational sweet spot
00:16:10which could change Apophis's orbit
00:16:13that will change the potential future trajectory of this rock
00:16:19and might make it totally harmless
00:16:21or might increase the chances of an impact even further in the future
00:16:28because of the gravitational keyhole
00:16:30there's still a small chance that Apophis will hit earth in 2068
00:16:36that is the important lesson that Apophis taught us
00:16:43you can miss the earth
00:16:45but if you pass through one of these keyholes
00:16:47at some time later
00:16:49you will hit the earth
00:16:51we now know Apophis will miss the keyhole in 2029
00:16:55but there are other keyholes and other close passes
00:16:59Apophis is not a lone threat
00:17:11there are an estimated 832,500 asteroids orbiting the sun
00:17:19most asteroids live their lives perfectly peacefully
00:17:24past the orbit of Mars or trailing Jupiter
00:17:27and don't mind anybody else
00:17:30don't cause any troubles
00:17:31but some asteroids are on very particular orbits
00:17:35that cross the orbit of the earth
00:17:40these asteroids have left the stable orbit of the asteroid belt
00:17:44and moved into orbits that get near our own
00:17:48these asteroids are called near earth asteroids
00:17:51or NEAs for short
00:17:53the near-earth asteroid population is interesting
00:17:56and potentially dangerous
00:17:57because they're the ones that actually cross the orbit of the earth
00:18:00so they're most likely to have
00:18:02at some point in the future
00:18:04an impact with the earth
00:18:06most NEAs pose little or no threat to earth
00:18:11but we've detected over 2,000
00:18:14including the 1,200 foot Apophis
00:18:16that do
00:18:19these are called PHAs
00:18:21potentially hazardous asteroids
00:18:23the difference between a near-earth asteroid
00:18:27and a potentially hazardous asteroid
00:18:29is distance and size
00:18:32anything can get near the earth
00:18:34and that could be 20 million miles away
00:18:37something like that
00:18:38and be a near-earth asteroid
00:18:39but a potentially hazardous one can hit us
00:18:42and it's big enough to do damage
00:18:48so something that over the next hundred years or so
00:18:51has a chance of hitting us
00:18:52and doing damage when it does
00:18:54that's a potentially hazardous object
00:18:58PHAs are asteroids that are 460 feet or larger
00:19:02that could collide with earth
00:19:04take a 400 foot asteroid
00:19:09if it hits
00:19:10it would release as much energy
00:19:12as 3,000 Hiroshima nuclear bombs
00:19:22in July of 2018
00:19:23NASA published a map
00:19:25of all the known NEAs and PHAs
00:19:28the animation tracks their discovery
00:19:34from 1999 through 2018
00:19:37every time I look at this animation
00:19:41it does make my heart stop a little bit
00:19:43because it looks like we're in the middle of the swarm
00:19:45of angry bees circling all around us
00:19:47in 1999 we'd identified under 300 NEAs
00:19:53scattered through the inner solar system
00:19:5510 years later
00:19:57we'd found 500 more
00:20:00by 2018
00:20:01we'd discovered
00:20:0218,000 near-earth asteroids
00:20:05but we estimate
00:20:06there are millions out there
00:20:09it seems like we could never find all the asteroids
00:20:12they just keep coming
00:20:13it's like we're fighting an army of zombies
00:20:16zombies that keep hurtling our way
00:20:20hitting the earth at up to 64,000 miles an hour
00:20:24that is very very fast
00:20:28that is much faster than a rifle bullet
00:20:30and that's the key to its destructive power
00:20:36when a really fast and really large asteroid hits
00:20:39the impact is off the charts
00:20:43the blast is so intense
00:20:45it can melt or even vaporize rock
00:20:54you've seen the light
00:21:04January 2019
00:21:06a total eclipse of the moon
00:21:08astronomers train their telescopes
00:21:10on the darkening lunar surface
00:21:14they capture a bright flash
00:21:17that lasts around a quarter of a second
00:21:19of a second it was recorded there were a lot of live webcasts and things like that going on at the
00:21:24time and you can see this flash of light what the heck was that at first the cause of the flash was
00:21:33a mystery it turns out it was actually a meteorite hitting the surface of the moon and because it was
00:21:41dark and because we were all looking at it we could actually see it the moon's dark surface
00:21:48gave us a unique view of what happens when an asteroid strikes what was so exciting about
00:21:53being able to see this impact on the moon in a dark area is that we could actually look at the light
00:21:59that it produced and then back calculate exactly what the size of the impactor was
00:22:04we worked out that the impacting asteroid was just 20 inches wide the crater it blew out was 45 feet
00:22:12across how can something so small be so destructive the two things that matter the most are how fast
00:22:21it's going and how massive is the thing the more massive the bigger the boom the faster the bigger
00:22:26the boom speed and weight are two very important factors to assess how much damage an asteroid will
00:22:31do just like a boxer if a tiny person like me were to swing a punch it would do a lot less damage than
00:22:37a heavyweight champion same thing with asteroids the bigger they are the bigger the punch but the
00:22:42same thing is fast right if i hit you really slowly it's not going to hurt i have to really wind back
00:22:47and pop that's what happens with an asteroid the damage from an asteroid strike is determined by its
00:22:54kinetic energy kinetic energy depends on two things speed and weight
00:22:59of the two speed matters most
00:23:08if you double the mass you double the kinetic energy but if you double the velocity you get four
00:23:14times the kinetic energy three times the speed nine times the impact energy ten times as fast it has a
00:23:19hundred times the energy so the velocity is what's really critical here
00:23:24the lunar asteroid weighed only a hundred pounds but it was traveling at 38 000 miles an hour
00:23:34carrying a huge kinetic energy which gouged out the crater
00:23:40it's the same principle for impacts on earth
00:23:4650 000 years ago a 150 foot asteroid hit what is now arizona
00:23:54the impact blasted out an impressive hole now called behringer crater it's about three
00:24:00quarters of a mile across over 500 feet deep you could put the washington monument in the bottom
00:24:05of the crater and the top of the monument wouldn't quite clear the rim it's a pretty impressive hole in
00:24:10the ground
00:24:15in 2016 impact specialist kathy plesco visited behringer crater to see firsthand what mass and speed
00:24:23due to the surface of the earth
00:24:29this is awe-inspiring to stand on the rim of a crater like this understanding just
00:24:37how much energy it must have taken to excavate this much rock
00:24:42the asteroid came in at about 27 000 miles an hour
00:24:53it comes slamming into the surface and just explodes anywhere nearby here would have seen winds of
00:24:59thousands of miles an hour as the shockwave came out
00:25:09the immense power of an asteroid impact comes from the kinetic energy being transferred from the space
00:25:15rock into the surface rock
00:25:20it's an extremely violent process and it starts with the moment of contact of the projectile with the surface itself
00:25:26it pushes into the crust and at first it's just almost punching like like sticking your thumb into dough
00:25:37it's only about as wide as the object is
00:25:39it's going straight down in but then it's meeting resistance from the surface of the earth
00:25:45and so it squishes squishes squishes until it runs out of momentum but then it's very compressed
00:25:51and all of that energy is in a very small space as it releases it detonates like a bomb and that's what makes the impact crater
00:25:58simulations of an asteroid strike in the lab reveal the impact in slow motion
00:26:10as the high speed pellet hits the surface the sand compresses downwards then rebounds
00:26:19and as that rebound is occurring that's when the material is being ejected out of the crater itself
00:26:25you'll see the surface erupting outwards like the blooming petals of some big rocky flower as all
00:26:32this debris goes spraying out in every direction
00:26:39the 150 foot behringer asteroid turned the rock to powder
00:26:4666 million years ago an asteroid around 200 times larger and moving one and a half times faster than
00:26:53beringer hit earth this asteroid impact called kpg had so much energy it turned rock to liquid
00:27:03this thing was immense it's really hard to wrap your head around just how big it is
00:27:08when it hits the back end of it is so far back that it's where a modern jetliner would fly
00:27:14the kpg asteroid hit the ground with a lethal combination of mass and speed a trillion tons
00:27:25traveling at 45 000 miles an hour
00:27:30some rock is completely vaporized it just becomes a gas you have some rock that it's melted you have
00:27:37some that's thrown out into space
00:27:39this material goes up through that and then falls down and settles down over a huge area that might
00:27:47be dust it might be pulverized rock it might be vaporized metal it's all of this hot material raining
00:27:53down everywhere some of the rock exploded skywards but rock below the surface was slammed by a shock wave
00:28:03that was completely off the charts rock stopped behaving like rock we experience rocks as solid
00:28:13objects but if you hit a rock hard enough it flows like water the kpg asteroid hit so hard it pulverized
00:28:21the rock turning it into liquid almost like ripples on a pond moving away from a stone that's been dropped
00:28:28in it it's almost like a splash in the solid body of the earth itself and
00:28:33like a water droplet splashing in water you'll see that that central peak will kind of splash up
00:28:39and rise to a high altitude and then come back down again we think a process very similar to that
00:28:44probably happened in the rock itself at the center of the crater rising up as high as the himalayas
00:28:50before relaxing back down into their current position again the material slumps and so these ripples
00:28:56are frozen in the rock and there are other fragments that go away radially almost like the spiderweb
00:29:02pattern in glass that you get after it's shot with a bullet the kpg impact blew out a crater 111 miles
00:29:12wide it is the third largest confirmed impact structure on earth a large and fast asteroid heading
00:29:22our way is always going to be a problem so what do we do wait for oblivion or fight back
00:29:32the space in the inner solar system seems calm stable and empty it's not
00:29:57there are tens of thousands of near-earth objects just whizzing around earth now space is big they're
00:30:06not going to hit us every time they orbit the sun but this does set up the possibility that one of
00:30:13these years we're going to end up at the same spot in space at the same time as that asteroid and then
00:30:20it's going to be an impact we're living in a cosmic shooting gallery asteroids strike the earth all the
00:30:28time through uh through history and it's going to happen again scientists are developing strategies to
00:30:34stop an asteroid from hitting our planet our options destroy or deflect the space rock
00:30:42but first we need to detect any dangerous asteroids heading our way it's a little bit unnerving to know
00:30:49that we haven't yet detected all of the asteroids that exist that could possibly cross our path we've
00:30:55discovered a lot of asteroids now but we typically discover the big ones but for asteroids that are
00:31:02below 100 feet there's a lot still out there that we haven't discovered and as such an asteroid can do
00:31:08some real damage if it were to explode over a populated area to prevent such a catastrophe we need to find
00:31:16all asteroids whose orbits cross our own detection is crucial in our defense against asteroids and the
00:31:23reason is the earlier they're detected the easier it is to deflect them away from hitting the earth
00:31:30you want to do deflection the first step is detection
00:31:35the problem is asteroids are very hard to detect finding asteroids and cataloging all their orbits is
00:31:43really challenging they can move quite fast across the sky and they might go away on the
00:31:48other side of the sun for years and years and years
00:31:53so we can't see them
00:31:56and even when they are on this side of the sun they're hard to spot
00:32:02but the problem is they're very small and they're very dark and when i say very dark i mean
00:32:07really dark like a lump of coal so how do you find a small dark rock just wandering around out there in the solar system
00:32:19the catalina sky survey has the answer
00:32:24the huge telescope in the mountains above tucson arizona takes a series of images over a 20-minute period
00:32:31of the sky in the sky it's hunting for anything that moves because stars don't move but asteroids do
00:32:42if it's a really bright asteroid we will see some bright points of light tracking across the four images
00:32:51ah here we go this is a real object you can see it's moving across the sky here from the lower
00:32:59right to the upper left we are very very excited to have discovered one tonight because this is an
00:33:05object that's approaching nearer space likely in the neighborhood of earth
00:33:14catalina has limitations it can only see visible light so a particularly dim asteroid could be missed
00:33:23asteroids are very cold they're usually quite far away from the sun but amazingly the best way we have
00:33:30to find these is infrared light because things that are cold by human scales can still be very warm to
00:33:36an infrared telescope so even if asteroids are just a few tens of degrees above absolute zero that's still
00:33:42enough heat to detect them when the infrared space telescope neowise turned its gaze onto asteroids
00:33:50it had immediate results neowise has now detected close to 160 000 new asteroids and comets in our
00:33:59solar system and about 780 of those are things that are near the earth 10 of those near objects have been
00:34:06classified as phas potentially hazardous asteroids without neowise we would have missed them using an
00:34:16infrared space telescope as a is a way of of better detecting some of the smaller asteroids and
00:34:23comets in the near earth vicinity detection is an important first step but it only tells us that
00:34:30there's another asteroid out there once we've spotted an asteroid all we know is that it's a tiny dot of
00:34:37light we don't know anything else about it so when a new asteroid is discovered the most important thing
00:34:43is to determine its path to track it to figure out exactly how it's orbiting around the sun and how
00:34:48close it's going to get to earth for that we have to know where they are now so its current location
00:34:53and measure how fast it's going in which direction is traveling all of these things together are really
00:34:59important for tracking where it's going to be next and whether or not they're going to hit us
00:35:05to get this information we need something much bigger and more powerful
00:35:09the arecibo observatory once catalina or another telescope detects a near-earth asteroid in our
00:35:19cosmic neighborhood arecibo's thousand foot dish swings into action they discovered these asteroids and
00:35:28then once we know where they were we can try and point the radio telescope and see where they are at the
00:35:35moment and measure their exact location and their trajectory arecibo achieves this level of
00:35:42precision by using radio detection and ranging more commonly known as radar the planetary radar system
00:35:50at the arecibo observatory is the most powerful radar system in the world we focus on potentially
00:35:56hazardous asteroids which are those that have a high probability of impacting earth arecibo sends out
00:36:04radio signals toward the newly detected asteroid emanates radio signals some of them hit the asteroid
00:36:11just like a radar gun from a cop might hit the side of your car it's pretty similar but instead of doing
00:36:18it with a radar gun on a small scale we're doing at a really big scale with one megawatt power hitting
00:36:24objects that are tens of lunar distances away and then those radio waves bounce back to earth and we detect
00:36:31them again and by comparing the differences between what we sent and what we received we can get a map of
00:36:40the asteroid itself and we can get where it's moving and how fast it's moving
00:36:46speed size and location of strike determine the outcome of an asteroid impact
00:36:51effect but the type of asteroid is another factor it can mean the difference between survival or complete
00:37:01annihilation
00:37:11the bering sea asteroid blew up in the atmosphere but the beringer crater asteroid hit the ground intact
00:37:27with its full force
00:37:31why do different asteroids behave differently and what will apophis do when it heads our way
00:37:38arecibo's radar may have the answer when we bounce radar waves off of these objects we can get
00:37:48effectively imagery of the surface of some of these small objects that we just cannot do with optical telescopes
00:37:56this is the radar image of apophis it's so far away that all they could image were a few pixels
00:38:02so this is our most recent radar image of asteroid apophis
00:38:11and you can see it's only a few pixels but it does give us information on what it actually is
00:38:20these few pixels are enough to work out how big apophis is
00:38:24from this image we can constrain the size to be about 1000 feet which is about the same size as the
00:38:34our receiver radio telescope all of that from a weird bunch of pixels
00:38:46knowing the size and mass of an asteroid is critical to understanding what an asteroid is made of
00:38:52if we have the size and the mass we get the density if we have the density we know what it's made of
00:38:59rock has some density metal has a different density so we can determine a huge amount about the asteroid
00:39:06simply by pinging it with radar
00:39:11arecibo's data reveals that not all asteroids are alike
00:39:15there's not just one kind of asteroid there are actually several kinds and this is important to
00:39:22understand because they behave differently they behave differently if they impact us and they behave
00:39:27differently if we're trying to prevent them from impacting us we need to know what these asteroids
00:39:34are made of if they're gonna hit the earth because that drastically alters the potential effects
00:39:40asteroids come in different shapes different sizes and different compositions and we think that is
00:39:46because they are the leftovers of planet formation to understand how each asteroid formed
00:39:52and their threat level we have to go back 4.6 billion years to the start of the solar system
00:40:00the reason that there are all these asteroids floating around
00:40:03in our solar system today is just because of the early violence of the solar system as it was forming
00:40:10at the birth of the solar system the sun ignites leaving a disk of gas and dust
00:40:23slowly over time planets form lots of planets the early solar system was a messy place there were a lot
00:40:34more planets a lot more forming planets they would crash into each other they would merge they would
00:40:39disintegrate they would reform this process of accretion of building planetary worlds was
00:40:49not just you know kind of gentle and happy it was it was violent it was like a giant cosmic game of pool
00:40:57planet smashing into planet
00:40:59the leftovers from this violence formed a ring of junk between mars and jupiter
00:41:09and now we call that junk asteroids they're just basically rubble left over from the formation of the solar system
00:41:20rocky leftovers became c-type or chondrite asteroids
00:41:25they're quite dense so big ones can punch through the atmosphere and hit the ground
00:41:35radar reveals a rarer type of asteroid
00:41:40some of them really stand out because their density is so much higher than the rest of the other asteroids
00:41:45these asteroids are m-type or metal
00:41:53because their mass is great they carry more kinetic energy during a strike
00:41:57by far the worst one is this iron meteorite this is really heavy so the difference if you were being
00:42:07hit by this would be the difference between being hit by a rock and being hit by a metal hammer
00:42:14we think that both the behringer and the kpg dinosaur killer were caused by metal asteroids
00:42:24but there's another more mysterious type floating through space
00:42:27the moon
00:42:34december 2018 nasa's spacecraft osiris rex approached the near-earth asteroid benu
00:42:44over time it drifted out of the main asteroid belt made its way into the inner solar system
00:42:49until it became a near-earth asteroid accessible for our spacecraft to go and visit
00:42:53the new planet osiris trained its camera on bennu
00:43:04one of the biggest surprises on arrival at bennu was the large number of large boulders on its surface
00:43:11bennu is really littered with huge boulders and littered with medium-sized boulders and littered with
00:43:16small boulders bennu is not a solid lump of rock it's made up of thousands of bits of
00:43:23of rock forming what we call a rubble pile.
00:43:27These asteroids aren't big, singular, spherical balls of rock,
00:43:32but rather they're literally piles of rubble.
00:43:34They're all sorts of pieces and fragments
00:43:36from another asteroid that had previously been disrupted
00:43:39and have all come back together and formed literally
00:43:42a pile of rocks held together by their own gravity.
00:43:45We think rubble piles formed from collisions
00:43:48inside the asteroid belt.
00:43:50Each impact blasted bits off.
00:43:53Then, over time, they came back together
00:43:56to form a loose pile of rocks.
00:43:59Imagine taking a big cosmic dump truck full of gravel and rubble
00:44:03and dumping it out there into space
00:44:05and letting gravity weakly hold it together.
00:44:11When scientists probe deeper into Bennu,
00:44:14they found another surprise.
00:44:15It's full of holes, like Swiss cheese.
00:44:19If you could slice open one of these asteroids,
00:44:22you'd see there are a lot of voids.
00:44:24In fact, 60% of what we're looking at is a void space.
00:44:28So they're actually really fluffy.
00:44:30So even though they're made of rocks,
00:44:32they're sort of the lint of rocks.
00:44:35Bennu helps us understand Apophis.
00:44:38Radar data shows that Apophis is also a rubble pile.
00:44:42If you look at Apophis, we really want to know how its orbit will evolve in the future.
00:44:47What we learn at Bennu about similar-sized rubble pile asteroids
00:44:51might help us understand the future of an asteroid like Apophis.
00:44:55So what would happen if the rubble pile called Apophis hits Earth?
00:44:59You probably don't want that to hit you still,
00:45:01but it definitely makes it a lot weaker than something like a solid rock,
00:45:05or even more, a chunk of nickel-iron metal.
00:45:10Does its composition make it any less of a threat?
00:45:14A rubble pile like Apophis is especially unnerving
00:45:17because we don't know when it interacts with the atmosphere
00:45:20if it's going to stay as one solid piece.
00:45:22Will it break up?
00:45:24When these rubble piles start interacting with planets,
00:45:27if they fly near a planet, they can get pulled apart into all of their little pieces.
00:45:32Or if they enter the atmosphere of a planet to impact the surface,
00:45:36they might slowly get pulled apart as they enter the atmosphere
00:45:40and end up being an array of little impacts instead of one big single impact.
00:45:45But what would happen if these impacts occur at sea?
00:45:58Will our oceans save us?
00:46:00Or will a giant tsunami wipe us out?
00:46:042019, U.S. researchers discover deposits of fossils.
00:46:23They contain both the remains of land and sea creatures.
00:46:29You see things that are all jumbled together,
00:46:32so you'll have fossils of sea creatures.
00:46:35You'll have ocean deposits that are mixed up with coastal deposits
00:46:41and onshore deposits.
00:46:42And you see those deposits in places that are very, very far away
00:46:47from where you would expect them to be.
00:46:49And so this material was obviously thrown very far inland.
00:46:55The jumbled deposits suggest that the creatures were killed at the same time
00:46:59in a huge and violent event.
00:47:03Something powerful enough to sweep ocean-dwelling creatures far inland.
00:47:09A tsunami.
00:47:11Tsunamis are usually created when the ocean floor moves suddenly.
00:47:17The ground picks up the entire ocean and shakes it up and down.
00:47:21And it's sort of like taking a rope and shaking it.
00:47:24And it moves all across the ocean floor and ocean surface until it reaches land.
00:47:29The biggest recent tsunami was caused by the Earth's crust at the bottom of the ocean lifting slightly.
00:47:36So this means that that entire length of crust that lifted displaced the water above it.
00:47:42So the waves, the tsunamis that result, are really long and wide.
00:47:47And it can travel across the ocean at tremendous speeds and up on land.
00:47:54Is this what happened to the fossilized creatures?
00:47:57Were they killed by a huge tsunami?
00:48:01Clues come from dating the preserved remains.
00:48:05They're 66 million years old.
00:48:08From the same time, a six-mile-wide asteroid crashed into the sea off the Yucatan Peninsula in Mexico.
00:48:19Are the two events connected?
00:48:21Do ocean-impacting asteroids trigger tsunamis?
00:48:26We used to think that a big asteroid impacting in the ocean would drive a tremendous tsunami,
00:48:31a huge wall of water, out at very rapid speeds, which would basically scour clean everything.
00:48:38Now, new research from 2018 suggests a very different scenario.
00:48:44Scientists use supercomputers to model asteroids hitting the deep ocean
00:48:49to work out how much of the asteroid's kinetic energy is converted into a tsunami.
00:48:55In the simulations, a 1,600-foot asteroid hits the ocean at 20,000 miles an hour and dives into the water.
00:49:08As it goes deeper in, of course, it's meeting a lot of resistance,
00:49:12and it slows down and it compresses up, it compresses and compresses and compresses,
00:49:17and then finally it runs out of momentum, and it's at an extremely high pressure.
00:49:22The huge pressure causes the asteroid to vaporize.
00:49:28Temperatures hotter than the surface of the sun turn trillions of gallons of water into steam.
00:49:34The blast creates a huge short-lived cavity in the water's surface, and a splash curtain, a wall of water that leaps up several miles.
00:49:47This curtain then collapses, and water falls back into the cavity, shooting a column of water five miles up.
00:49:55This very tall column can't support its own weight, and collapses back down.
00:50:02The collapse of so much water triggers a wave 1,200 feet high.
00:50:08Could this become a huge tsunami?
00:50:10If we think about a meteor striking the ocean, we want to understand how far the waves might propagate from this site.
00:50:22We could actually just use a stone and throw it into a pond.
00:50:25And you might think, okay, well, it's a big stone, it's going to make a really big splash,
00:50:29and that's just going to extend out a long distance.
00:50:31But it turns out the splash stays the biggest, really close to where it impacts, and then the ripples die down after that.
00:50:37So let's try that.
00:50:40Big splash in the middle.
00:50:43And we see the ripples going outward, but they're really pretty small compared with that initial big splash.
00:50:47It's the same with an ocean impacting asteroid.
00:50:53The impact creates surface waves that die away quickly, because only a small amount of the asteroid's kinetic energy gets into the water.
00:51:03It's actually pretty tough to make a tsunami like that.
00:51:06The energy of the asteroid doesn't couple well with the water to drive this wave.
00:51:10Instead, most of the energy goes into vaporizing the asteroid itself, as well as all of the water around it.
00:51:18Only 1% of the asteroid's kinetic energy goes into making a wave.
00:51:23So, only low energy waves form, too weak to become giant tsunamis traveling hundreds of miles.
00:51:33So what caused the jumbled fossil deposits found thousands of miles away from the impact site?
00:51:38We don't think there could be that much energy still transmitted that far away from the impact site.
00:51:45Instead, there has to be a different source of energy that created different waves right about the same time as that impact event.
00:51:53Research from 2019 may have the answer.
00:51:58The KPG asteroid struck on the continental shelf, the shallow region between land and deep ocean.
00:52:05The impact triggered a localized tsunami, large enough to kill creatures in the region.
00:52:12But it also sent a huge shockwave into the bedrock.
00:52:16There's going to be a shockwave driven through the ground.
00:52:20That probably would have killed anything in the area.
00:52:23If you had a dinosaur that was standing on the Gulf Coast of what is now the United States, that animal would have experienced a seismic pulse, an earthquake, that is stronger than anything on our current Richter scale.
00:52:43It would have actually driven its legs up into its body cavity, killing it instantly.
00:52:46There's all manner of mayhem and death taking place at this time. There was no escape in this event.
00:52:54The initial shockwave smashed into the ground rock and traveled through the Earth's crust.
00:53:00The impact would have shaken the crust of the Earth, which also would have triggered earthquakes around the world, which themselves may have triggered secondary tsunamis.
00:53:13Secondary tsunamis, thousands of miles from the impact site, killed both land and sea creatures.
00:53:22The KPG impact went on to wipe out 70% of all life on Earth.
00:53:31So how did one asteroid strike cause a global kill zone?
00:53:5266 million years ago, 70% of life on Earth died after the KPG asteroid strike.
00:54:07How could one space rock hitting the sea cause a global catastrophe?
00:54:12When you have a big rock hitting the ocean, the biggest danger is not from the waves, but actually from the steam that it creates.
00:54:22The impact vaporized trillions of tons of seawater.
00:54:27This steam rose up into the atmosphere, where it condensed into water vapor.
00:54:32Water vapor is a greenhouse gas, so that's then going up into the upper atmosphere, and it's trapping heat, but at different layers it's making clouds, it's just throwing everything off kilter.
00:54:47Water is a very effective greenhouse gas, as you will actually affect some very significant climate change very quickly as a result of that impact.
00:54:55Within weeks of the asteroid strike, water vapor in the atmosphere caused temperatures to rise.
00:55:05But that was only the start.
00:55:08The impact also blew out 10 trillion tons of rock, ash, and dust.
00:55:16This asteroid is so big, six miles wide, it's punched a hole in the air.
00:55:21There's like a column of low density, a chimney, that goes from the ground up to the top of the atmosphere.
00:55:27And that means there's very little air resistance in that tunnel.
00:55:31These rocks can actually blast up into the chimney and find it easier to get up out of the atmosphere.
00:55:37It sent that material flying up halfway to the orbit of the moon, circled around the Earth.
00:55:43All this ring of material falling back onto the Earth, and it was like the sky itself was on fire.
00:55:51So you not only do you have rocks falling on you, but they're molten.
00:55:55And these rocks will start catching plants and anything else on fire.
00:55:58Soot and ash rose into the atmosphere, blocking out the sun.
00:56:13Material was thrown into the atmosphere, plunging the planet into a nuclear winter.
00:56:18It was complete chaos, and it went dark for two full years.
00:56:22Without sunlight, temperatures dropped.
00:56:27Just months after the impact, the planet cooled by 20 degrees.
00:56:33In the immediate area, there's just tremendous destruction, just everything gets destroyed.
00:56:39But over the long term, you're talking about ash kicked up in the atmosphere, extremely cold weather, basically a global ice age.
00:56:47The freezing temperatures killed off most plant life.
00:56:53Imagine how that affected life on Earth.
00:56:56No plants, and the base of the ecosystem collapses.
00:57:04This dark nuclear winter lasted two years, and prevented plants from photosynthesizing.
00:57:09So if plants can no longer use photosynthesis to live, they'll die.
00:57:16And then with no plants, then you have no food for these larger animals.
00:57:21And so anything that eats those animals will also die.
00:57:24If you lose your plants, you're going to lose your large scale life.
00:57:27First, the plant-eating herbivores died off, followed by the meat-eating carnivores.
00:57:33Most of the dinosaurs were just unable to find food and to survive through the cold, long night.
00:57:42The global devastation wasn't over yet.
00:57:46The rock of the continental shelf, where the asteroid hit, contained carbon and sulfur.
00:57:51These carbonate rocks were heated and vaporized and released carbon dioxide into the atmosphere, yet another greenhouse gas.
00:58:03So you're vaporizing a lot of sulfur, a lot of salts of different kinds that are then lofted up into the upper atmosphere that then plays havoc on the climate.
00:58:13These greenhouse gases built up in the atmosphere, forming a warming blanket, triggering the next phase of destruction, global warming on steroids.
00:58:36Temperatures rose 10 degrees above normal.
00:58:41Then, the oceans warmed as well.
00:58:46Oxygen levels dropped, and the seas became toxic to simple life forms.
00:58:53It actually made it impossible for certain microbes to actually live, and they're the basis of the food system.
00:59:00So really, it changed what could actually live in the ocean, and how much could live there.
00:59:07Dead zones appeared in the oceans, just as they had on land.
00:59:13Nearly three-quarters of all life on Earth died.
00:59:17All from one asteroid impact.
00:59:22To prevent it from happening again, we need to track all potentially dangerous asteroids.
00:59:33But that isn't easy, because these space rocks can change direction.
00:59:39To prevent it from happening again, we need to change direction.
00:59:50Sari Cicek, Turkey.
00:59:56Security cameras record a flash in the sky.
01:00:01The flash? A three-foot asteroid exploding in the atmosphere.
01:00:16It blew up in the atmosphere and rained down.
01:00:18And people saw that. It was very noticeable.
01:00:21And they went and they collected those meteorites.
01:00:24And then, they tried to figure out what they were looking at.
01:00:27The debris was sent for fragment analysis.
01:00:35I have a piece of one here.
01:00:37So first, on the outside, you can see it has a really black fusion crust.
01:00:40This is from when it fell into the Earth's atmosphere, so it was melted.
01:00:44But, when you look on the inside, it reveals this beautiful, very light-toned, fine-grained material.
01:00:50And so these meteorites are incredibly distinctive and really beautiful.
01:00:54The meteorites are rocky.
01:00:57Their beautiful color comes from a mineral called Howardite.
01:01:01It's rare, and it doesn't form on Earth.
01:01:04Howardite meteorites come from the asteroid Vesta.
01:01:09And we know that because of the Dawn mission that actually went to Vesta and took a look at it very carefully.
01:01:14So we know the composition very well.
01:01:17And so now, suddenly, here was a new kind of meteorite that's in Turkey that matches the Vesta family of meteorites.
01:01:25But how can we be sure that these bits of space rock came from Vesta, an asteroid over a hundred million miles away?
01:01:33It was a fall meteorite. And so what that means is that someone saw it. You know, we saw it fall. And so we knew its trajectory. So we could actually work backwards to say, where did that meteorite come from?
01:01:47Retracing the trajectory of the Turkish meteorites took the scientists all the way back to the 328-mile-wide Vesta.
01:02:01When they studied Vesta's surface, they found further evidence.
01:02:05On the surface of Vesta, there's actually a very large and fresh impact crater that is around the same age of the Turkish meteorite. So that really clinched it. This thing is definitely from Vesta, and we proved it.
01:02:20So how did bits of Vesta end up here on Earth?
01:02:2422 million years ago, some very large impactor struck Vesta and made a huge crater. And some of the rocks from that crater actually escaped from Vesta's gravity and were lofted into space.
01:02:39Some of these rocks from Vesta went into orbits that intersected with Earth.
01:02:4522 million years later, one blew up over Sari Cicic.
01:02:50The Sari Cicic meteor shows that the asteroid belt is an unstable environment.
01:03:01Asteroids frequently strike other asteroids.
01:03:07That's actually happening all the time. Things are running into each other in our solar system right now.
01:03:12And so that makes it really hard for us to track all of those objects, because we don't actually know what happens after they collide with each other,
01:03:19now things are totally different. That changes the whole system.
01:03:24Each collision makes more asteroids.
01:03:28There's many different possibilities of what could happen when asteroids collide.
01:03:33Imagine a roller derby situation.
01:03:38You have two groups of players that run into each other.
01:03:41That could be like two asteroids running into each other.
01:03:44And one possible outcome is that one stays intact while the other is completely blown apart.
01:03:51That sends fragments flying all through the main asteroid belt.
01:03:57And then those little asteroid fragments are on their own independent orbits around the sun.
01:04:01A problem with asteroid impacts is that we're always making new asteroids.
01:04:08There are big asteroids out there, and they get hit by other asteroids, and then you get shrapnel.
01:04:13And now you've got not one big one and one smaller one.
01:04:16You've got one big one, one smaller one, and millions of little ones.
01:04:19Now most of these aren't very big, but some of them might be bigger and could be potentially hazardous.
01:04:23As the solar system ages, the number of asteroids increases.
01:04:30Each new space rock travels on a new course, which could intersect with Earth.
01:04:36So we're constantly producing new asteroids and big collisions in the main asteroid belt.
01:04:42And these are producing the small asteroids that will eventually drift inward in the solar system.
01:04:46Tracking this constantly evolving population of asteroids gives scientists a huge headache.
01:04:56If they break apart, then that gives you even more pieces of the asteroid to track.
01:05:01It's not a simple thing to track and predict the orbits of asteroids and their movements.
01:05:06Because one tiny little change can have huge dramatic impacts for its possible future.
01:05:17Figuring out exactly where they're going to go and keeping track of how they interact with each other.
01:05:22This is a huge endeavor.
01:05:24The sheer volume of asteroids can affect the behavior of other asteroids as they gravitationally interact.
01:05:31Think about your roller derby player, skating in circles.
01:05:36The path they're going to follow would evolve the more people you plop down on that track.
01:05:41They start interacting with each other and their trajectory will change.
01:05:46The more crowded you make the solar system, the more things there are to change your orbit of your individual asteroid.
01:05:55It's not like air traffic control where there's a known amount of airplanes and they all follow a plan.
01:05:59This situation is further complicated because asteroid orbits can be affected by other more subtle forces.
01:06:09One of these is called the Yarkovsky or the Yorp effect.
01:06:14Honestly, Yorp is more fun to say.
01:06:17The Yorp effect is caused by sunlight hitting an asteroid.
01:06:21Light is made up of photons that are traveling and these photons actually have momentum.
01:06:26So, when light shines on something, it actually pushes on it.
01:06:32When sunlight hits an asteroid, the photons give it a tiny push.
01:06:37Enough to change the space rock's trajectory.
01:06:48When we know an asteroid is really heading our way, it's time to fight back.
01:06:52So, we've got an asteroid that's headed at us, what do we do?
01:06:56Two main possibilities.
01:06:58We deflect it, we nudge it a little bit so it misses, or we blow it up, we destroy it.
01:07:02Which of those do you want to do?
01:07:03Which of those do you want to do?
01:07:11It's a tough choice.
01:07:13Get it wrong, and we could end up being hit by a swarm of radioactive space rocks.
01:07:33An asteroid is heading our way, and it may hit us in 2068.
01:07:47How do we prevent such a catastrophe, and stop it from ever getting close?
01:07:53Well, you just don't want to get anywhere near us in the first place.
01:07:57So, what do you do?
01:07:59Well, you can destroy them, or you can push them out of the way.
01:08:03This is something where our science fiction ideas have gotten almost entirely wrong.
01:08:07If you're in a bad movie, a really, really bad movie, you can send astronauts to an asteroid, put a nuclear bomb in it, and blow it up into lots of little bits that then burn up harmlessly in our atmosphere.
01:08:22Yeah, it doesn't work that way.
01:08:24Blowing up an asteroid would make the problem much worse.
01:08:27Much worse. You're no longer dealing with just one space rock.
01:08:31My issue with this is that you may have turned one problem into 50.
01:08:36Instead of one regular-sized asteroid, now you have a whole bunch of littler ones, and these may still hit the Earth and cause damage.
01:08:43And you know what? That's not much less fun than just having a single big asteroid.
01:08:48Now you've just taken all that devastation and spread it out for everybody to enjoy.
01:08:51The problem with using a nuclear device is that the products that rain down on Earth are now radioactive.
01:09:07If a dangerous asteroid was on its way, blowing it up would be a last resort.
01:09:12A less risky method is to deflect it off its collision course.
01:09:19A small nudge early enough can change an asteroid's trajectory away from Earth.
01:09:25You don't have to nudge it very much for it to miss, right?
01:09:30So if it's headed straight at it, just touch it slightly. By the time it gets to Earth, it's way off course.
01:09:34NASA is investigating ways to change an asteroid's path, including using a nuclear burst.
01:09:45In a nuclear burst, what we do is we don't actually hit it.
01:09:51We come up to it with the device on a spacecraft, and then the device would be detonated at a certain height above the surface.
01:10:00That heats up the surface of the asteroid, which vaporizes.
01:10:04You get vaporized rock or metal, which blasts off the surface, and that's how a rocket works.
01:10:09So you blow up a bomb here, and it winds up pushing the asteroid in the other direction.
01:10:14To prevent any potential nuclear fallout, NASA would detonate the bomb a long way from Earth.
01:10:20Any deflection attempt has to be done years in advance, which means it would be done on the other side of the solar system from us, on the opposite side of the object's orbit.
01:10:33That means that all of the vapor made during the explosion gets blown away by the solar wind.
01:10:38NASA is investigating other, less explosive methods of deflecting an asteroid.
01:10:44D-star would blast the asteroid with a laser.
01:10:49We hit it with the laser, material vaporizes and flies off the asteroid, and because of Newton's third law, which is that for every action there's an opposite and equal reaction, this means that vaporized material moving off in one direction moves the asteroid in the opposite direction.
01:11:05Both the laser and the nuclear burst are still just ideas on the drawing board.
01:11:15But one asteroid deflection mission, called Double Asteroid Redirection Test, or DART for short, is already up and running and scheduled for launch in 2021.
01:11:27DART is a kinetic impactor and will try to knock an asteroid off course.
01:11:33At NASA, for the longest time, all we've been able to do is theorize about how we change their path.
01:11:40But now for the first time, we're actually going to practice it.
01:11:44Leading this groundbreaking mission to bump an asteroid off its orbit is Dr. Andy Chang.
01:11:51DART is the first planetary defense mission that we've ever done, where we take a spacecraft, we fly the spacecraft into the asteroid to change its course,
01:12:02and make it miss the Earth.
01:12:04DART's target is a 525-foot space rock orbiting the large, near-Earth asteroid, Didymus.
01:12:12We picked the near-Earth asteroid, Didymus, as a target for the DART mission because it's, although it's a near-Earth asteroid,
01:12:17it's one that's very safely parked away out there in space.
01:12:20There's no way we can move Didymus or its moon in any way big enough to cause a problem for the Earth.
01:12:27The Didymun asteroid weighs around ten and a half billion pounds.
01:12:32So how do you knock such a large lump of rock off its path?
01:12:53We're sending a spacecraft to knock the Didymun asteroid off course.
01:12:57The asteroid is moving at over 36,000 miles an hour and is around seven million miles away.
01:13:06So, how do you move a ten and a half billion pound space rock?
01:13:11You need to hit it really hard to change its orbit.
01:13:15So it's going to be coming in at a super high velocity in order to impart a bunch of energy and momentum to that moon.
01:13:22DART will hit the target at around 14,000 miles an hour.
01:13:29The speed of the DART impact will be more than nine times the speed of the rifle bullet from AK-47.
01:13:39The impact will give the asteroid a small push.
01:13:43To work out how big a push, we test impacts with the Ames vertical gun.
01:13:48At the NASA Ames Research Center in California, there's a very special facility called the Ames Vertical Gun Range.
01:13:55It's a hypervelocity gas gun that allows us to shoot little metal BBs at rock targets at speeds up to like 13, 14,000 miles per hour.
01:14:05The gun replicates the impact the DART mission will make.
01:14:09It reveals that an impact will blow off a small amount of debris, but at extremely high speed, enough to give the asteroid an additional kick.
01:14:19The impact will blow off pieces of the asteroid.
01:14:23So the pieces are thrown off the back, and so that process acts like a little rocket engine.
01:14:28That provides an additional momentum change, momentum push, to the target itself.
01:14:34The combined push from the kinetic impactor and the ejected debris is tiny, around nine ten thousandths of a mile per hour.
01:14:43But hopefully, it's enough to change the asteroid's orbit.
01:14:47If DART works, we could then use a similar mission to defend Earth when the time comes.
01:14:53This isn't some small rock prototype that we're doing this test on.
01:14:58This is a real dress rehearsal for an asteroid that could destroy cities or even maybe send the Earth in chaos.
01:15:06The moon of Didymus is a solid lump of rock.
01:15:10Will a kinetic impactor like DART work with a rubble pile asteroid like Apophis?
01:15:16When you shoot a rubble pile with a projectile, it's a little bit more like trying to punch a sandbag.
01:15:19You get a lot more of the energy that's absorbed into just moving the sand around inside the bag than ejecting it.
01:15:26And so rubble piles might be a little harder to move by this method.
01:15:30We don't know if we can deflect a rubble pile asteroid like Apophis.
01:15:36They remain a clear and present danger, and something we might not survive.
01:15:42But there may be a space lifeboat.
01:15:50In 2018, scientists re-examined rocks collected by Apollo 14 astronauts from the moon.
01:15:57Buried in the samples was a rock that shouldn't be there.
01:16:12They got something they didn't expect, and that was an Earth rock.
01:16:20They actually picked up a rock from Earth on the moon.
01:16:24They didn't bring it with them.
01:16:26It's very likely that it was something that was lofted up when something hit Earth,
01:16:31threw up a bunch of rocks, some of those rocks fell onto the moon.
01:16:35And that's a meteorite on the moon, but it's from Earth.
01:16:45Supercomputer simulations of the KPG asteroid strike reveal how the impact had so much energy
01:16:53that it catapulted rocks out of Earth's atmosphere and into space.
01:16:58They were then caught by the moon's gravity and pulled down to the lunar surface.
01:17:02We now know that material ejected into space from asteroid impacts can travel to other planets as well,
01:17:11which would explain the 100 Mars meteorites we found here on Earth.
01:17:19We think that there was probably the exchange of a huge amount of material between different bodies,
01:17:25Earth to the moon and back again into Mars.
01:17:26With each impact that occurs in our solar system, that ejects all types of material that allows material to swap from planet to planet,
01:17:38moon to planet, moon to moon.
01:17:40And so there's all of this material that eventually travels from place to place.
01:17:43Should another giant asteroid hit our planet, this planetary interchange may give life on Earth a lifeline.
01:17:54If you think about such an impact today, you know, the chances are high that a lot of life will be wiped out.
01:18:01Much of life, probably all of human life.
01:18:03It's certainly possible that a big enough asteroid strike could completely sterilize a planet.
01:18:10Talking about no life whatsoever.
01:18:12Not to put too fine a point on it, but if there's a dinosaur killer asteroid out there and it hits the Earth,
01:18:18the chance of humanity's survival of such a thing as a species, hmm, not great.
01:18:22Humans may not survive, but some scientists believe that simple life forms could.
01:18:52Asteroids have hit our planet many times in the past.
01:19:01One giant strike wiped out 70% of all life on Earth.
01:19:06If another huge asteroid hits us, can life survive?
01:19:11If a giant rock hits the Earth and kills almost all life on Earth, there is a slim line of hope.
01:19:26And that's because the dirt, the rocks on Earth are infused with bacterial life, with microscopic life.
01:19:34And in the event of a giant impact, some of these bits of rock will be ejected into space and might float around.
01:19:43After an asteroid impact, whatever ejected into the atmosphere could contain microbial life
01:19:49that, when it falls back down onto the ground, could reseed the life on that planet.
01:19:53Some bacteria can survive the harsh conditions of space and can cope with an asteroid strike, re-entry, and landing back on Earth's surface.
01:20:09I think in terms of life on planet Earth, I think we've learned that we live on a very resilient planet.
01:20:25And I think life in some form, even if it has to crawl its way back from bacterial stage,
01:20:31I think life on this planet is going to eke through.
01:20:33Life is pretty good at figuring out a way of surviving.
01:20:40We know that life first formed on the Earth well over four billion years ago,
01:20:45and has never been wiped out in all of that time.
01:20:48There's always been something after every major mass extinction.
01:20:52So life will continue. It just won't necessarily be us.
01:20:57An asteroid strike on another world may be how life on Earth started in the future.
01:21:03In the first place.
01:21:04There's an interesting idea that an asteroid strike on another planet could have actually seeded life on Earth.
01:21:10And the way this works is, you have life that's somehow gotten a foothold on some other planet like Mars.
01:21:16A big asteroid strike hits that planet and knocks a piece of it off,
01:21:20eventually rains down on Earth, carrying with it life.
01:21:22We may owe the existence of life here to asteroid impacts.
01:21:29That's speculative, but it's kind of a cool thought.
01:21:34Life seeding asteroids may have hit us in the past, and other asteroids will hit us in the future.
01:21:43One of those may be a pofis, arriving in less than half a century.
01:21:54Maybe we'll deflect it.
01:21:57Maybe it'll miss us all on its own.
01:22:01Either way, we need to keep tabs on it.
01:22:04The best thing we can do as a species, and it's funny because it almost sounds like I'm advocating for more jobs for astronomers,
01:22:12we need to keep looking at the sky.
01:22:14We need to look at the sky longer and deeper with more sensitive instruments,
01:22:18and get more of a sense of what out there is around us.
01:22:20That's what our species needs to do to ultimately survive.
01:22:22Because now we have the ability to see these things a little bit better, we have the ability to protect ourselves better.
01:22:30It doesn't have to be a surprise.
01:22:32You know, the first time we see a big impact doesn't have to be as it's bearing down, destroying our planet.
01:22:37We can actually see it before it gets to us and decide what we want to do about it.
01:22:42Earth's history is littered with asteroid strikes.
01:22:47Some wiped out millions of species.
01:22:50Some may have seeded life in the first place.
01:22:55What the future holds in our relationship with these space rocks, no one knows.
01:23:01Even though the chances of something really large hitting the Earth are pretty small, the consequences are dire.
01:23:10It would really destroy our planet, or at least life as we understand it.
01:23:15And so in many ways, asteroids are the greatest threat that we face.
01:23:19Life is fragile.
01:23:21So of course we live in a larger environment where something could come and hit us at any time.
01:23:26That's part of being alive.
01:23:28There's no guarantee tomorrow will happen.
01:23:30But what there is, is a high likelihood that you'll still be safe tomorrow.
01:23:34Impacts from space are rare, but if they do happen, it's a huge deal.
01:23:43And so you got to put those two things together.
01:23:45That means we got to pay attention.
01:23:46Those impacts have happened many times in the past, and they're going to continue to happen many times in the future.
01:23:54Fortunately, it's not probably in our immediate future.
01:23:57Impacts are rare, but the Earth lives a long time.
01:24:00So you're unlikely to get in a car accident, but if you drive enough, you're going to get in a car accident.
01:24:10Over a century timescale, yes, we should be concerned about these.
01:24:13But over the daily, weekly, monthly, even yearly timescale, I wouldn't sweat it too much.
01:24:18I wouldn't say we should lose sleep over an asteroid or comet striking Earth, but the reality is, it will happen again.
01:24:28So when you think about asteroid strikes, remember this wonderful, dramatic universe you find yourself in.
01:24:34We're here because stars died and exploded.
01:24:37Life on Earth wouldn't be the same if we didn't find ourselves in this dramatic and even dangerous environment in space.
01:24:42But this is who we are. This is nothing new.
01:24:46And this will continue for the future of our planet.