Would you like to inspect the original subtitles? These are the user uploaded subtitles that are being translated:
1
00:00:02,803 --> 00:00:07,239
Narrator: A dangerous asteroid
is heading towards earth.
2
00:00:07,241 --> 00:00:09,975
It's the size of
the empire state building,
3
00:00:09,977 --> 00:00:15,714
and it's travelling at
16,000 miles an hour.
4
00:00:15,716 --> 00:00:20,686
It's called apophis,
after the egyptian god of chaos.
5
00:00:20,688 --> 00:00:25,657
It will fly close to us
in 2029.
6
00:00:25,659 --> 00:00:27,860
It won't hit us...This time,
7
00:00:27,862 --> 00:00:31,430
but when it returns
in 2068,
8
00:00:31,432 --> 00:00:34,400
that could be another story.
9
00:00:34,402 --> 00:00:39,171
If it blows up over a city,
millions of people will die.
10
00:00:41,208 --> 00:00:43,942
This could be the most
devastating single event
11
00:00:43,944 --> 00:00:45,978
in u.S. History.
12
00:00:45,980 --> 00:00:48,280
Narrator: Earth is stuck
in the crosshairs
13
00:00:48,282 --> 00:00:50,816
of a potential asteroid strike.
14
00:00:50,818 --> 00:00:55,821
Apophis is one of around 2,000
potentially hazardous asteroids
15
00:00:55,823 --> 00:01:00,292
that present
a real and present danger.
16
00:01:00,294 --> 00:01:05,531
Asteroids have hit us before,
and they will hit us again.
17
00:01:08,702 --> 00:01:11,537
As far as cosmic dangerous go,
18
00:01:11,539 --> 00:01:13,738
they're number one
on the list.
19
00:01:13,740 --> 00:01:15,841
Narrator: This is not a drill.
20
00:01:15,843 --> 00:01:19,078
If we do nothing...
21
00:01:19,080 --> 00:01:21,380
This is our future.
22
00:01:21,382 --> 00:01:28,387
♪
23
00:01:28,389 --> 00:01:31,356
-- captions by vitac --
www.Vitac.Com
24
00:01:31,358 --> 00:01:34,393
captions paid for by
discovery communications
25
00:01:38,866 --> 00:01:41,800
December 2018.
26
00:01:41,802 --> 00:01:44,636
The u.S. Military detect
a huge explosion
27
00:01:44,638 --> 00:01:47,039
in the earth's atmosphere
28
00:01:47,041 --> 00:01:48,674
high over the bering sea
29
00:01:48,676 --> 00:01:52,277
off the coast of alaska.
30
00:01:52,279 --> 00:01:54,980
When an explosion of this
magnitude is detected,
31
00:01:54,982 --> 00:01:58,283
everyone's mind
goes to the same thing -- nukes.
32
00:01:58,285 --> 00:02:02,521
But when the real answer
was found and it was determined
33
00:02:02,523 --> 00:02:04,723
that it didn't even
originate from earth,
34
00:02:04,725 --> 00:02:07,059
that was even more shock.
35
00:02:07,061 --> 00:02:09,027
Narrator:
The cause of the blast --
36
00:02:09,029 --> 00:02:11,597
an asteroid.
37
00:02:11,599 --> 00:02:13,699
This asteroid was
30 feet across --
38
00:02:13,701 --> 00:02:14,500
something like that --
39
00:02:14,502 --> 00:02:16,702
over a thousand tons,
40
00:02:16,704 --> 00:02:19,805
but it was moving
at 20 miles per second,
41
00:02:19,807 --> 00:02:23,408
over 70,000 miles an hour.
42
00:02:23,410 --> 00:02:26,545
Narrator: This asteroid was
small, and it exploded
43
00:02:26,547 --> 00:02:28,947
in the atmosphere
over the ocean,
44
00:02:28,949 --> 00:02:30,582
so nobody was hurt.
45
00:02:33,988 --> 00:02:35,821
But if it had been bigger
46
00:02:35,823 --> 00:02:38,090
or it had come
in over a different place
47
00:02:38,092 --> 00:02:39,591
or it had been moving
a lot faster,
48
00:02:39,593 --> 00:02:41,793
this could have been
a dangerous object.
49
00:02:41,795 --> 00:02:43,729
But the scariest thing
about it
50
00:02:43,731 --> 00:02:46,031
is that
we didn't see it coming.
51
00:02:46,033 --> 00:02:51,370
♪
52
00:02:51,372 --> 00:02:54,740
narrator:
So far, we've been lucky.
53
00:02:54,742 --> 00:02:57,643
But near misses happen
all the time.
54
00:03:00,147 --> 00:03:02,414
About once a year,
we get something
55
00:03:02,416 --> 00:03:06,318
the equivalent of a nuclear bomb
going off in our atmosphere.
56
00:03:06,320 --> 00:03:08,620
And while that
sounds horrible,
57
00:03:08,622 --> 00:03:13,659
most of these happen
tens of miles up...
58
00:03:13,661 --> 00:03:18,864
Over open ocean, where we go
on completely oblivious.
59
00:03:21,435 --> 00:03:26,271
Narrator:
We may be oblivious to most
of the threats from space,
60
00:03:26,273 --> 00:03:28,440
but they are very real.
61
00:03:28,442 --> 00:03:30,075
We're going to get hit.
62
00:03:30,077 --> 00:03:32,244
Over a certain amount of time,
63
00:03:32,246 --> 00:03:34,613
an asteroid impact
is inevitable.
64
00:03:34,615 --> 00:03:38,150
It will happen 100%,
absolute certainty.
65
00:03:38,152 --> 00:03:40,219
[ dog barking in distance ]
66
00:03:40,221 --> 00:03:44,890
♪
67
00:03:44,892 --> 00:03:47,359
[ rumbling, car alarm blaring ]
68
00:03:47,361 --> 00:03:53,899
♪
69
00:03:53,901 --> 00:03:57,402
narrator:
Nasa considers the threat
from the skies so severe
70
00:03:57,404 --> 00:04:03,108
it has made protection
from asteroids a top priority.
71
00:04:03,110 --> 00:04:06,578
These events are not rare.
They happen.
72
00:04:06,580 --> 00:04:10,782
And of course it's up to us to
make sure that we are detecting
73
00:04:10,784 --> 00:04:14,253
and characterizing, tracking
all of the near-earth objects
74
00:04:14,255 --> 00:04:16,722
that potentially
could be a threat.
75
00:04:16,724 --> 00:04:19,191
This is not about hollywood.
It's not about movies.
76
00:04:19,193 --> 00:04:22,828
This is about ultimately
protecting the only planet
77
00:04:22,830 --> 00:04:25,497
we know right now to host life,
78
00:04:25,499 --> 00:04:27,466
and that is the planet earth.
79
00:04:30,237 --> 00:04:32,170
To help plan
protecting our home,
80
00:04:32,172 --> 00:04:36,575
we carry out
earth defense simulations.
81
00:04:36,577 --> 00:04:37,843
For three days,
82
00:04:37,845 --> 00:04:40,879
200 scientist at the planetary
defense conference
83
00:04:40,881 --> 00:04:45,217
battle a simulated
asteroid 20 times larger
84
00:04:45,219 --> 00:04:48,353
than the bering sea space rock.
85
00:04:48,355 --> 00:04:52,791
We practice, "alright,
what if this hits a major city?
86
00:04:52,793 --> 00:04:55,994
What would we need to do?"
87
00:04:55,996 --> 00:04:58,730
narrator: By running
potential impact scenarios,
88
00:04:58,732 --> 00:05:02,934
we can prepare
for a real asteroid strike.
89
00:05:02,936 --> 00:05:05,170
This is like a fire drill
that you would do at school
90
00:05:05,172 --> 00:05:06,805
or at work,
where you practice
91
00:05:06,807 --> 00:05:08,073
and think about, okay,
what if?
92
00:05:08,075 --> 00:05:10,108
Where are the exits?
How do I get out?
93
00:05:10,110 --> 00:05:12,177
How fast do I get out?
94
00:05:14,281 --> 00:05:16,648
Narrator: The drill starts
with the discovery
95
00:05:16,650 --> 00:05:20,452
of a simulated
earthbound asteroid.
96
00:05:20,454 --> 00:05:23,055
So, the first information
is there's a big asteroid
97
00:05:23,057 --> 00:05:24,523
coming towards the earth.
98
00:05:24,525 --> 00:05:25,824
Then we get a better estimate
99
00:05:25,826 --> 00:05:28,026
of how big it is,
how fast it's going,
100
00:05:28,028 --> 00:05:29,795
and where it's going to hit.
101
00:05:29,797 --> 00:05:32,631
Narrator: The asteroid
is heading straight for earth
102
00:05:32,633 --> 00:05:36,034
with denver, colorado,
in its sights.
103
00:05:38,138 --> 00:05:40,105
The planetary defense
scientists
104
00:05:40,107 --> 00:05:44,576
send up a simulated spacecraft
to smash into the asteroid
105
00:05:44,578 --> 00:05:46,545
and push it off its path.
106
00:05:46,547 --> 00:05:48,780
But it's a big gamble.
107
00:05:48,782 --> 00:05:50,816
You can push it
the wrong way.
108
00:05:50,818 --> 00:05:55,354
You can potentially
have unintended consequences.
109
00:05:57,658 --> 00:05:58,757
Narrator:
In the simulation,
110
00:05:58,759 --> 00:06:03,395
the spacecraft
strikes the asteroid...
111
00:06:03,397 --> 00:06:06,698
Deflecting it away from earth.
112
00:06:06,700 --> 00:06:10,302
But the impact dislodge
is a 200-foot chunk,
113
00:06:10,304 --> 00:06:15,207
which is now heading straight
towards the eastern seaboard.
114
00:06:15,209 --> 00:06:17,275
So there's this one
last piece
115
00:06:17,277 --> 00:06:20,512
that is now
going to hit new york.
116
00:06:20,514 --> 00:06:23,382
We know that something that size
117
00:06:23,384 --> 00:06:27,219
is going to have
citywide consequences.
118
00:06:27,221 --> 00:06:31,857
That is huge.
That's a horrible impact.
119
00:06:31,859 --> 00:06:33,325
Thaller: When you're actually
in the conference room
120
00:06:33,327 --> 00:06:34,993
and you understand eventually
121
00:06:34,995 --> 00:06:37,829
that new york city
is going to be destroyed...
122
00:06:37,831 --> 00:06:40,532
And you're having strategies
about how to evacuate people,
123
00:06:40,534 --> 00:06:43,068
all the timing,
when you're doing the simulation
124
00:06:43,070 --> 00:06:44,136
you're in your head.
125
00:06:44,138 --> 00:06:45,303
You're thinking
about these things.
126
00:06:45,305 --> 00:06:47,038
You're trying to
reason them out,
127
00:06:47,040 --> 00:06:50,342
but can you imagine the feeling
in your gut, in your heart,
128
00:06:50,344 --> 00:06:53,011
if this was real?
129
00:06:53,013 --> 00:06:55,180
Narrator: If this were real,
the chunk of asteroid
130
00:06:55,182 --> 00:06:57,149
would strike earth's atmosphere
131
00:06:57,151 --> 00:06:59,451
at 43,000 miles an hour.
132
00:07:03,223 --> 00:07:05,824
As the space rock hurtles
down, it collides
133
00:07:05,826 --> 00:07:10,695
with molecules in the atmosphere
which buffet the falling rock.
134
00:07:10,697 --> 00:07:13,565
It's kind of like doing
a belly flop into a pool, right?
135
00:07:13,567 --> 00:07:15,400
You're going from
the vacuum of space
136
00:07:15,402 --> 00:07:19,471
into the dense lower atmosphere
in mere seconds.
137
00:07:19,473 --> 00:07:21,440
And that's an incredible
amount of pressure
138
00:07:21,442 --> 00:07:23,842
to put on the object.
139
00:07:23,844 --> 00:07:26,011
Narrator:
The asteroid slams into the air
140
00:07:26,013 --> 00:07:29,881
ahead of it,
compressing it violently.
141
00:07:29,883 --> 00:07:34,286
The surface of the asteroid
gets hotter and brighter.
142
00:07:34,288 --> 00:07:36,955
Durda:
It's actually the air itself
that's glowing luminously
143
00:07:36,957 --> 00:07:38,757
from the heating
of the shockwave,
144
00:07:38,759 --> 00:07:41,159
the world's most
intense sonic boom if you will,
145
00:07:41,161 --> 00:07:44,062
that heats the air
to incandescence
146
00:07:44,064 --> 00:07:45,630
as the object passes through.
147
00:07:45,632 --> 00:07:50,001
So that's the source
of that brilliant illumination.
148
00:07:50,003 --> 00:07:55,040
Narrator: This bright, burning
asteroid is called a bolide.
149
00:07:55,042 --> 00:07:57,709
We witnessed one descending
over the russian city
150
00:07:57,711 --> 00:08:00,545
of chelyabinsk in 2013.
151
00:08:00,547 --> 00:08:02,681
All of a sudden, there was
a huge fireball
152
00:08:02,683 --> 00:08:03,949
streaking through the sky,
153
00:08:03,951 --> 00:08:06,451
and people had no idea
what they were witnessing
154
00:08:06,453 --> 00:08:09,488
because it looked like the sky
was on fire.
155
00:08:09,490 --> 00:08:11,423
It was insanity.
156
00:08:11,425 --> 00:08:13,658
Narrator: As the asteroid
descends,
157
00:08:13,660 --> 00:08:16,428
the compression
of the denser air beneath it
158
00:08:16,430 --> 00:08:21,266
starts to flatten and even
disrupt the falling rock.
159
00:08:21,268 --> 00:08:23,001
Oluseyi: There's a high pressure
on the front,
160
00:08:23,003 --> 00:08:24,603
there's no pressure on the back
161
00:08:24,605 --> 00:08:26,404
and it's being super heated.
162
00:08:26,406 --> 00:08:30,509
Sutter:
And that intense temperature
causes the air to glow,
163
00:08:30,511 --> 00:08:32,811
which is how we see
this streak of a meteor.
164
00:08:32,813 --> 00:08:35,847
And it also disintegrates
the asteroid itself.
165
00:08:35,849 --> 00:08:39,150
It's hard enough
to literally melt rock.
166
00:08:39,152 --> 00:08:42,454
This can often
lead to them exploding.
167
00:08:42,456 --> 00:08:44,623
Narrator: The combination
of heat and pressure invade
168
00:08:44,625 --> 00:08:47,526
the falling asteroid,
causing it to blow up.
169
00:08:47,528 --> 00:08:49,995
[ explosion ]
170
00:08:49,997 --> 00:08:52,664
most asteroids
don't reach the ground
171
00:08:52,666 --> 00:08:54,366
before they
completely disintegrate
172
00:08:54,368 --> 00:08:56,902
in a tremendous release
of energy.
173
00:08:56,904 --> 00:08:58,270
Plait: This is what we call
an air burst,
174
00:08:58,272 --> 00:09:00,338
and we learned a lot about these
175
00:09:00,340 --> 00:09:05,911
while we were testing nuclear
weapons after world war ii.
176
00:09:05,913 --> 00:09:07,345
Some of these bombs
were blown up
177
00:09:07,347 --> 00:09:09,147
underground and on the ground,
178
00:09:09,149 --> 00:09:12,050
but they found out when they
blew up bombs above the ground,
179
00:09:12,052 --> 00:09:13,518
it actually did more damage.
180
00:09:13,520 --> 00:09:16,454
It was more widespread damage.
181
00:09:16,456 --> 00:09:18,924
Narrator: The explosion of
the chelyabinsk asteroid
182
00:09:18,926 --> 00:09:22,928
sent out a powerful shockwave
at thousands of miles an hour.
183
00:09:26,500 --> 00:09:30,001
The blast traveled
over 100 miles.
184
00:09:30,003 --> 00:09:32,671
It damaged 7,000 buildings
185
00:09:32,673 --> 00:09:35,840
and put 1,500 people
in the hospital.
186
00:09:35,842 --> 00:09:38,143
All of the injuries
pretty much came from people
187
00:09:38,145 --> 00:09:40,745
who saw, "oh, what's
that bright flash in the sky?"
188
00:09:40,747 --> 00:09:44,349
and they came close to a window
to look and see what it was,
189
00:09:44,351 --> 00:09:47,419
and then the pressure wave hit
and blew glass in their face.
190
00:09:50,223 --> 00:09:54,292
Narrator:
The chelyabinsk asteroid
was only 65 feet across.
191
00:09:56,530 --> 00:09:58,597
The rock in the
defense simulation
192
00:09:58,599 --> 00:10:00,765
is three times more massive,
193
00:10:00,767 --> 00:10:05,870
and it's heading straight
for new york city.
194
00:10:05,872 --> 00:10:09,341
Imagine what would happen
if an explosion a thousand times
195
00:10:09,343 --> 00:10:13,845
greater than that over hiroshima
hit new york.
196
00:10:13,847 --> 00:10:17,582
We're talking about an utter
complete destruction of the city
197
00:10:17,584 --> 00:10:21,019
and millions of people.
198
00:10:21,021 --> 00:10:22,253
Narrator:
With so little warning,
199
00:10:22,255 --> 00:10:27,158
the only option would be
to evacuate new york city.
200
00:10:27,160 --> 00:10:29,194
How do we get everybody out
of new york city
201
00:10:29,196 --> 00:10:30,795
within just a few days?
202
00:10:30,797 --> 00:10:32,430
That's where panic sets in.
203
00:10:32,432 --> 00:10:35,433
That's where fear would really
become the dominant emotion.
204
00:10:38,005 --> 00:10:39,838
Narrator: Anyone left
in new york city
205
00:10:39,840 --> 00:10:42,407
would see the bolide
racing in...
206
00:10:45,445 --> 00:10:48,146
...Followed
by a blinding light...
207
00:10:48,148 --> 00:10:52,617
As the asteroid explodes
above the city.
208
00:10:52,619 --> 00:10:56,921
The blast would be equivalent
to the largest nuclear weapon
209
00:10:56,923 --> 00:10:59,257
ever detonated on earth.
210
00:10:59,259 --> 00:11:01,660
Plait: Buildings would be
flattened, melted.
211
00:11:01,662 --> 00:11:04,362
There would be fires
for miles around
212
00:11:04,364 --> 00:11:06,698
in the first moments
of the explosion.
213
00:11:06,700 --> 00:11:09,534
A million people
could be killed instantly
214
00:11:09,536 --> 00:11:11,503
and many more would die later
in the rubble,
215
00:11:11,505 --> 00:11:15,540
in the ruins
of what would happen there.
216
00:11:15,542 --> 00:11:19,444
Narrator:
Everything within nine miles
of the blast epicenter
217
00:11:19,446 --> 00:11:21,713
would be completely destroyed.
218
00:11:21,715 --> 00:11:28,853
♪
219
00:11:28,855 --> 00:11:33,758
the intense heat and
pressure would wreck buildings.
220
00:11:33,760 --> 00:11:37,295
Sutter: It's the worst possible
day for new yorkers,
221
00:11:37,297 --> 00:11:39,597
and not just the city itself.
222
00:11:39,599 --> 00:11:42,767
There's something like
15 million people
223
00:11:42,769 --> 00:11:44,936
living in the new york area.
224
00:11:48,675 --> 00:11:53,712
Narrator:
The shock wave would race
out over 250 square miles.
225
00:11:53,714 --> 00:11:55,680
This would certainly be
the worst disaster
226
00:11:55,682 --> 00:11:57,148
that the u.S.
Has ever experienced.
227
00:11:57,150 --> 00:12:00,185
We're talking about millions
and millions of people
228
00:12:00,187 --> 00:12:02,754
displaced,
affected within an instant.
229
00:12:02,756 --> 00:12:09,394
♪
230
00:12:09,396 --> 00:12:13,398
narrator: This scenario is
just a simulation...For now.
231
00:12:13,400 --> 00:12:18,536
♪
232
00:12:18,538 --> 00:12:21,940
the asteroid apophis
is heading our way.
233
00:12:24,611 --> 00:12:26,077
If it hits earth,
234
00:12:26,079 --> 00:12:28,413
it might not just kill a city.
235
00:12:28,415 --> 00:12:31,216
It could kill a whole region.
236
00:12:31,218 --> 00:12:32,851
I wouldn't exactly
want to be there
237
00:12:32,853 --> 00:12:38,089
when that happens --
want to be very, very far away.
238
00:12:38,091 --> 00:12:43,561
Narrator: Apophis will skim
earth in 2029.
239
00:12:43,563 --> 00:12:46,698
But its path could change,
240
00:12:46,700 --> 00:12:49,868
possibly turning
a future miss...
241
00:12:49,870 --> 00:12:51,536
Into a direct hit.
242
00:12:51,538 --> 00:12:56,674
♪
243
00:13:07,521 --> 00:13:10,221
♪
244
00:13:10,223 --> 00:13:13,057
narrator: April 13, 2029,
245
00:13:13,059 --> 00:13:16,060
a speck of light
races towards the earth.
246
00:13:16,062 --> 00:13:20,165
It's an 1,100 foot wide asteroid
called apophis.
247
00:13:20,167 --> 00:13:24,969
We are about to have
an extremely close shave.
248
00:13:26,072 --> 00:13:28,640
It's the closest approach
of any asteroid
249
00:13:28,642 --> 00:13:32,477
that didn't actually hit us
for a long, long time.
250
00:13:32,479 --> 00:13:36,047
It will be 10 times closer
than the moon itself.
251
00:13:36,049 --> 00:13:38,283
It'll be so close that
it will be brighter
252
00:13:38,285 --> 00:13:40,485
than some stars.
253
00:13:40,487 --> 00:13:43,421
Narrator: The football-stadium
sized apophis
254
00:13:43,423 --> 00:13:46,291
will race over the atlantic.
255
00:13:46,293 --> 00:13:48,059
Plait: If it were sitting on
the surface of the earth,
256
00:13:48,061 --> 00:13:50,161
it would weigh
about 50 million tons,
257
00:13:50,163 --> 00:13:51,830
something like that,
258
00:13:51,832 --> 00:13:55,200
and that is not the place
you want it to be.
259
00:13:55,202 --> 00:14:00,171
You want it to be in space
and far away.
260
00:14:00,173 --> 00:14:03,208
Narrator: When we discovered
apophis in 2004,
261
00:14:03,210 --> 00:14:06,344
we thought it might be
on a collision course with earth
262
00:14:06,346 --> 00:14:08,112
with a potential impact
263
00:14:08,114 --> 00:14:12,750
greater than the largest
atomic bomb ever exploded.
264
00:14:12,752 --> 00:14:15,687
Durda: The largest nuclear
device, atomic device
265
00:14:15,689 --> 00:14:19,424
ever detonated on our planet was
the tsar bomba bomb in russia,
266
00:14:19,426 --> 00:14:22,427
so something like
55 or 56 megatons.
267
00:14:22,429 --> 00:14:26,764
When krakatoa
exploded in 1883
268
00:14:26,766 --> 00:14:29,000
that was something
like 200 megatons.
269
00:14:29,002 --> 00:14:32,136
Apophis' impact
would be 450 megatons.
270
00:14:32,138 --> 00:14:34,439
If something like that were
to happen over new york city
271
00:14:34,441 --> 00:14:39,677
or washington d.C.,
you're going to lose the city.
272
00:14:39,679 --> 00:14:42,714
Narrator: The impact would be
at least 10 times greater
273
00:14:42,716 --> 00:14:45,583
than the simulated
asteroid strike on new york.
274
00:14:45,585 --> 00:14:52,790
♪
275
00:14:52,792 --> 00:14:55,693
sutter: Well, when you put it
in those terms,
276
00:14:55,695 --> 00:14:57,762
that's just plain scary.
277
00:14:57,764 --> 00:15:02,000
In a word, an impact
from an apophis-sized asteroid
278
00:15:02,002 --> 00:15:07,005
would be bad --
very, very bad.
279
00:15:07,007 --> 00:15:09,374
Narrator: Apophis' orbit
will cross earth
280
00:15:09,376 --> 00:15:12,977
every seven years
this century.
281
00:15:12,979 --> 00:15:15,179
It won't hit us in 2029,
282
00:15:15,181 --> 00:15:20,351
but this close encounter
could change apophis' orbit.
283
00:15:20,353 --> 00:15:25,156
When a small asteroid encounters
a bigger body like a planet,
284
00:15:25,158 --> 00:15:28,159
it's like a bunch
of roller derby players.
285
00:15:30,363 --> 00:15:31,996
Most of them
are clumped together,
286
00:15:31,998 --> 00:15:35,800
but maybe there's one just on
their own particular orbit,
287
00:15:35,802 --> 00:15:37,302
and as they circle around,
288
00:15:37,304 --> 00:15:39,270
as they get close
to that larger clump,
289
00:15:39,272 --> 00:15:41,005
there'll be some interactions --
290
00:15:41,007 --> 00:15:42,874
potentially violent
interactions --
291
00:15:42,876 --> 00:15:46,210
that will change
the future trajectory
292
00:15:46,212 --> 00:15:49,147
of that lone
roller derby skater.
293
00:15:49,149 --> 00:15:50,515
And the next time around,
294
00:15:50,517 --> 00:15:54,852
it might be a wide miss
or it might be a head-on impact.
295
00:15:58,959 --> 00:16:01,693
Narrator: It's the same
in the solar system.
296
00:16:01,695 --> 00:16:04,295
The combined gravity
of the earth and moon
297
00:16:04,297 --> 00:16:09,000
creates what's called
a gravitational keyhole,
298
00:16:09,002 --> 00:16:12,003
a gravitational sweet spot,
299
00:16:12,005 --> 00:16:15,873
which could change
apophis' orbit.
300
00:16:15,875 --> 00:16:19,310
That will change the potential
future trajectory of this rock
301
00:16:19,312 --> 00:16:21,813
and might make it
totally harmless
302
00:16:21,815 --> 00:16:23,982
or might increase the chances
303
00:16:23,984 --> 00:16:28,419
of an impact
even further in the future.
304
00:16:28,421 --> 00:16:30,822
Narrator: Because of the
gravitational keyhole,
305
00:16:30,824 --> 00:16:32,256
there's still a small chance
306
00:16:32,258 --> 00:16:36,661
that apophis will hit earth
in 2068.
307
00:16:40,967 --> 00:16:43,901
Plait: That is the important
lesson that apophis taught us --
308
00:16:43,903 --> 00:16:45,470
you can miss the earth,
309
00:16:45,472 --> 00:16:47,572
but if you pass through
one of these keyholes,
310
00:16:47,574 --> 00:16:51,642
at some time later,
you will hit the earth.
311
00:16:51,644 --> 00:16:56,547
Narrator: We now know apophis
will miss the keyhole in 2029,
312
00:16:56,549 --> 00:16:59,951
but there are other keyholes
and other close passes.
313
00:16:59,953 --> 00:17:07,392
♪
314
00:17:07,394 --> 00:17:11,629
apophis is not a lone threat.
315
00:17:11,631 --> 00:17:16,234
There are an estimated
832,500 asteroids
316
00:17:16,236 --> 00:17:19,003
orbiting the sun.
317
00:17:19,005 --> 00:17:21,839
Most asteroids live
their lives
318
00:17:21,841 --> 00:17:25,743
perfectly peacefully
past the orbit of mars
319
00:17:25,745 --> 00:17:29,747
or trailing jupiter
and don't mind anybody else,
320
00:17:29,749 --> 00:17:33,117
don't cause any troubles,
but some asteroids
321
00:17:33,119 --> 00:17:35,653
are on very particular orbits
322
00:17:35,655 --> 00:17:40,258
that cross the orbit
of the earth.
323
00:17:40,260 --> 00:17:42,693
Narrator: These asteroids
have left the stable orbit
324
00:17:42,695 --> 00:17:44,228
of the asteroid belt
325
00:17:44,230 --> 00:17:48,433
and moved into orbits
that get near our own.
326
00:17:48,435 --> 00:17:51,769
These asteroids are called
near earth asteroids
327
00:17:51,771 --> 00:17:54,472
or n.E.A.S for short.
328
00:17:54,474 --> 00:17:56,941
Walsh: The near earth asteroid
population is interesting
329
00:17:56,943 --> 00:17:58,810
and potentially dangerous
because they are the ones
330
00:17:58,812 --> 00:18:00,545
that actually cross
the orbit of the earth.
331
00:18:00,547 --> 00:18:03,314
So they're most likely
to have, at some point
332
00:18:03,316 --> 00:18:06,017
in the future,
an impact with the earth.
333
00:18:07,987 --> 00:18:12,423
Narrator: Most n.E.A.S pose
little or no threat to earth.
334
00:18:12,425 --> 00:18:14,492
But we've detected over 2,000,
335
00:18:14,494 --> 00:18:19,363
including the 1,200 foot apophis
that do.
336
00:18:19,365 --> 00:18:21,599
These are called p.H.A.S --
337
00:18:21,601 --> 00:18:25,736
potentially hazardous asteroids.
338
00:18:25,738 --> 00:18:27,872
The difference between
a near earth asteroid
339
00:18:27,874 --> 00:18:33,578
and a potentially hazardous
asteroid is distance and size.
340
00:18:33,580 --> 00:18:35,079
Anything can get near the earth,
341
00:18:35,081 --> 00:18:37,448
and that could be
20 million miles away,
342
00:18:37,450 --> 00:18:39,884
something like that,
and be a near earth asteroid,
343
00:18:39,886 --> 00:18:42,787
but a potentially hazardous one
can hit us,
344
00:18:42,789 --> 00:18:45,056
and it's big enough
to do damage.
345
00:18:48,995 --> 00:18:51,329
So something that over
the next hundred years or so
346
00:18:51,331 --> 00:18:54,765
has a chance of hitting us
and doing damage when it does --
347
00:18:54,767 --> 00:18:57,068
that's a potentially
hazardous object.
348
00:18:59,105 --> 00:19:03,274
Narrator: P.H.A.S are asteroids
that are 460 feet or larger
349
00:19:03,276 --> 00:19:04,976
that could collide with earth.
350
00:19:07,213 --> 00:19:10,348
Take a 400-foot asteroid --
if it hits,
351
00:19:10,350 --> 00:19:12,316
it would release as much energy
352
00:19:12,318 --> 00:19:15,953
as 3,000
hiroshima nuclear bombs.
353
00:19:22,095 --> 00:19:23,561
Narrator: In July of 2018,
354
00:19:23,563 --> 00:19:25,530
nasa published a map
355
00:19:25,532 --> 00:19:29,300
of all the known
n.E.A.S and p.H.A.S.
356
00:19:32,438 --> 00:19:34,605
The animation tracks
their discovery
357
00:19:34,607 --> 00:19:38,009
from 1999 through 2018.
358
00:19:40,046 --> 00:19:41,445
Every time I look
at this animation,
359
00:19:41,447 --> 00:19:43,481
it does make my heart
stop a little bit
360
00:19:43,483 --> 00:19:45,449
because it looks like
we're in the middle of a swarm
361
00:19:45,451 --> 00:19:49,353
of angry bees
circling all around us.
362
00:19:49,355 --> 00:19:51,656
Narrator: In 1999,
we'd identified
363
00:19:51,658 --> 00:19:53,658
under 300 n.E.A.S
364
00:19:53,660 --> 00:19:56,427
scattered through
the inner solar system.
365
00:19:56,429 --> 00:20:00,598
10 years later,
we'd found 500 more.
366
00:20:00,600 --> 00:20:05,937
By 2018, we'd discovered 18,000
near earth asteroids,
367
00:20:05,939 --> 00:20:10,241
but we estimate
there are millions out there.
368
00:20:10,243 --> 00:20:12,977
It seems like we could
never find all the asteroids.
369
00:20:12,979 --> 00:20:14,278
They just keep coming.
370
00:20:14,280 --> 00:20:17,248
It's like we're fighting
an army of zombies.
371
00:20:17,250 --> 00:20:21,118
Narrator: Zombies that keep
hurtling our way,
372
00:20:21,120 --> 00:20:26,891
hitting the earth at up
to 64,000 miles an hour.
373
00:20:26,893 --> 00:20:28,526
That is very, very fast.
374
00:20:28,528 --> 00:20:30,695
That is much faster
than a rifle bullet.
375
00:20:30,697 --> 00:20:33,497
And that's the key
to its destructive power.
376
00:20:36,769 --> 00:20:40,238
Narrator: When a really fast
and really large asteroid hits,
377
00:20:40,240 --> 00:20:43,941
the impact is off the charts.
378
00:20:43,943 --> 00:20:46,110
The blast is so intense,
379
00:20:46,112 --> 00:20:49,513
it can melt
or even vaporize rock.
380
00:21:01,294 --> 00:21:04,295
♪
381
00:21:04,297 --> 00:21:06,497
narrator: January 2019,
382
00:21:06,499 --> 00:21:08,799
a total eclipse
of the moon.
383
00:21:08,801 --> 00:21:10,568
Astronomers train
their telescopes
384
00:21:10,570 --> 00:21:12,937
on the darkening lunar surface.
385
00:21:14,741 --> 00:21:17,608
They capture a bright flash
386
00:21:17,610 --> 00:21:21,145
that lasts around a quarter
of a second.
387
00:21:21,147 --> 00:21:23,281
It was recorded. There were
a lot of live webcasts
388
00:21:23,283 --> 00:21:25,616
and things like that going on
at the time,
389
00:21:25,618 --> 00:21:27,685
and you can see
this flash of light.
390
00:21:27,687 --> 00:21:29,320
What the heck was that?
391
00:21:31,257 --> 00:21:35,459
Narrator: At first, the cause
of the flash was a mystery.
392
00:21:35,461 --> 00:21:39,730
It turns out it was actually
a meteorite hitting
393
00:21:39,732 --> 00:21:42,300
the surface of the moon,
and because it was dark
394
00:21:42,302 --> 00:21:43,668
and because we were all looking
at it,
395
00:21:43,670 --> 00:21:46,804
we could actually see it.
396
00:21:46,806 --> 00:21:49,473
Narrator: The moon's dark
surface gave us a unique view
397
00:21:49,475 --> 00:21:52,376
of what happens
when an asteroid strikes.
398
00:21:52,378 --> 00:21:53,844
What was so exciting
about being able
399
00:21:53,846 --> 00:21:57,381
to see this impact
on the moon in a dark area
400
00:21:57,383 --> 00:22:00,351
is that we could actually look
at the light that it produced
401
00:22:00,353 --> 00:22:01,952
and then back-calculate
402
00:22:01,954 --> 00:22:04,855
exactly what the size
of the impactor was.
403
00:22:04,857 --> 00:22:07,391
Narrator: We worked out that
the impacting asteroid
404
00:22:07,393 --> 00:22:09,960
was just 20 inches wide.
405
00:22:09,962 --> 00:22:14,265
The crater it blew out
was 45 feet across.
406
00:22:14,267 --> 00:22:18,969
How can something so small
be so destructive?
407
00:22:18,971 --> 00:22:21,839
The two things that matter
the most are how fast it's going
408
00:22:21,841 --> 00:22:23,240
and how massive is the thing.
409
00:22:23,242 --> 00:22:24,842
The more massive,
the bigger the boom,
410
00:22:24,844 --> 00:22:26,677
the faster the bigger the boom.
411
00:22:26,679 --> 00:22:29,013
Speed and weight
are two very important factors
412
00:22:29,015 --> 00:22:31,782
to assess how much damage
an asteroid will do.
413
00:22:31,784 --> 00:22:34,018
Just like a boxer --
if a tiny person like me
414
00:22:34,020 --> 00:22:35,453
were to swing a punch,
415
00:22:35,455 --> 00:22:38,989
it would do a lot less damage
than a heavyweight champion.
416
00:22:38,991 --> 00:22:40,157
Bullock:
Same thing with asteroids.
417
00:22:40,159 --> 00:22:41,992
The bigger they are,
the bigger the punch.
418
00:22:41,994 --> 00:22:43,828
But the same thing
is fast, right?
419
00:22:43,830 --> 00:22:46,097
If I hit you really slowly,
it's not gonna hurt.
420
00:22:46,099 --> 00:22:48,399
I have to really wind back
and pap.
421
00:22:48,401 --> 00:22:51,569
That's what happens
with an asteroid.
422
00:22:51,571 --> 00:22:53,270
Narrator: The damage from
an asteroid strike
423
00:22:53,272 --> 00:22:55,606
is determined
by its kinetic energy.
424
00:22:55,608 --> 00:22:57,942
Kinetic energy depends
on two things --
425
00:22:57,944 --> 00:23:00,044
speed and weight.
426
00:23:02,615 --> 00:23:05,883
Of the two, speed matters most.
427
00:23:08,488 --> 00:23:11,255
If you double the mass,
you double the kinetic energy,
428
00:23:11,257 --> 00:23:12,990
but if you double the velocity,
429
00:23:12,992 --> 00:23:15,226
you get four times
the kinetic energy.
430
00:23:15,228 --> 00:23:17,895
Three times the speed,
nine times the impact energy.
431
00:23:17,897 --> 00:23:19,163
10 times as fast,
432
00:23:19,165 --> 00:23:21,465
it has a hundred times
the energy,
433
00:23:21,467 --> 00:23:24,135
so the velocity
is what's really critical here.
434
00:23:26,773 --> 00:23:29,340
Narrator: The lunar asteroid
weighed only 100 pounds,
435
00:23:29,342 --> 00:23:34,445
but it was traveling
at 38,000 miles an hour.
436
00:23:34,447 --> 00:23:38,716
Carrying a huge kinetic energy,
which gouged out the crater.
437
00:23:40,753 --> 00:23:45,656
It's the same principle
for impacts on earth.
438
00:23:45,658 --> 00:23:49,293
50,000 years ago,
a 150-foot asteroid
439
00:23:49,295 --> 00:23:51,595
hit what is now arizona.
440
00:23:53,800 --> 00:23:56,667
The impact blasted out
an impressive hole
441
00:23:56,669 --> 00:23:59,136
now called barringer crater.
442
00:23:59,138 --> 00:24:01,906
Durda: It's about
3/4 of a mile across,
443
00:24:01,908 --> 00:24:03,240
over 500 feet deep.
444
00:24:03,242 --> 00:24:04,842
You could put
the washington monument
445
00:24:04,844 --> 00:24:06,343
in the bottom of the crater,
446
00:24:06,345 --> 00:24:09,146
and the top of the monument
wouldn't quite clear the rim.
447
00:24:09,148 --> 00:24:11,382
It's a pretty impressive hole
in the ground.
448
00:24:15,321 --> 00:24:18,489
Narrator: In 2016,
impact specialist cathy plesko
449
00:24:18,491 --> 00:24:20,157
visited barringer crater
450
00:24:20,159 --> 00:24:23,360
to see firsthand
what mass and speed
451
00:24:23,362 --> 00:24:25,329
do to the surface of the earth.
452
00:24:25,331 --> 00:24:29,667
♪
453
00:24:29,669 --> 00:24:35,206
this is awe-inspiring to stand
on the rim of a crater like this
454
00:24:35,208 --> 00:24:38,642
understanding
just how much energy
455
00:24:38,644 --> 00:24:42,780
it must have taken
to excavate this much rock.
456
00:24:46,152 --> 00:24:51,121
The asteroid came in
at about 27,000 miles an hour.
457
00:24:53,292 --> 00:24:54,992
It comes slamming
into the surface
458
00:24:54,994 --> 00:24:56,494
and just explodes.
459
00:24:56,496 --> 00:24:58,362
Anywhere nearby here
460
00:24:58,364 --> 00:25:00,898
would have seen winds
of thousands of miles an hour
461
00:25:00,900 --> 00:25:02,833
as the shockwave came out.
462
00:25:02,835 --> 00:25:08,939
♪
463
00:25:08,941 --> 00:25:11,475
narrator: The immense power
of an asteroid impact
464
00:25:11,477 --> 00:25:13,377
comes from the kinetic energy
465
00:25:13,379 --> 00:25:17,448
being transferred from the space
rock into the surface rock.
466
00:25:19,952 --> 00:25:22,486
It's an extremely
violent process,
467
00:25:22,488 --> 00:25:24,555
and it starts with the moment
of contact
468
00:25:24,557 --> 00:25:28,759
of the projectile
with the surface itself.
469
00:25:28,761 --> 00:25:31,595
Plesko:
It pushes into the crust,
470
00:25:31,597 --> 00:25:35,399
and at first,
it's just almost punching, like,
471
00:25:35,401 --> 00:25:36,834
sticking your thumb into dough.
472
00:25:36,836 --> 00:25:39,403
It's only about
as wide as the object is.
473
00:25:39,405 --> 00:25:41,105
It's going straight down in,
474
00:25:41,107 --> 00:25:45,643
but then it's meeting resistance
from the surface of the earth.
475
00:25:45,645 --> 00:25:47,778
And so it squishes,
squishes, squishes,
476
00:25:47,780 --> 00:25:51,615
until it runs out of momentum,
but then it's very compressed
477
00:25:51,617 --> 00:25:54,184
and all of that energy is in
a very small space.
478
00:25:54,186 --> 00:25:56,787
As it releases,
it detonates like a bomb.
479
00:25:56,789 --> 00:26:01,792
And that's what makes
the impact crater.
480
00:26:01,794 --> 00:26:04,562
Narrator: Simulations of
an asteroid strike in the lab
481
00:26:04,564 --> 00:26:07,164
reveal the impact
in slow motion.
482
00:26:10,570 --> 00:26:14,138
As the high speed pellet
hits the surface,
483
00:26:14,140 --> 00:26:19,410
the sand compresses downwards,
then rebounds.
484
00:26:19,412 --> 00:26:21,245
And as that rebound
is occurring,
485
00:26:21,247 --> 00:26:23,614
that's when the material
is being ejected
486
00:26:23,616 --> 00:26:26,717
out of the crater itself.
487
00:26:26,719 --> 00:26:28,686
You'll see the surface
erupting outwards
488
00:26:28,688 --> 00:26:31,889
like the blooming petals
of some big rocky flower
489
00:26:31,891 --> 00:26:34,792
as all this debris goes
spraying out in every direction.
490
00:26:34,794 --> 00:26:39,830
♪
491
00:26:39,832 --> 00:26:42,399
narrator: The 150-foot
barringer asteroid
492
00:26:42,401 --> 00:26:46,036
turned the rock to powder.
493
00:26:46,038 --> 00:26:48,172
66 million years ago,
494
00:26:48,174 --> 00:26:50,975
an asteroid
around 200 times larger
495
00:26:50,977 --> 00:26:53,310
and moving
one and a half times faster
496
00:26:53,312 --> 00:26:55,846
than barringer hit earth.
497
00:26:55,848 --> 00:26:59,083
This asteroid impact --
called k-pg --
498
00:26:59,085 --> 00:27:00,651
had so much energy,
499
00:27:00,653 --> 00:27:03,520
it turned rock
to liquid.
500
00:27:03,522 --> 00:27:05,489
This thing was immense.
It's really hard to wrap
501
00:27:05,491 --> 00:27:08,125
your head around
just how big it is.
502
00:27:08,127 --> 00:27:11,929
When it hits the back end of it,
it is so far back,
503
00:27:11,931 --> 00:27:15,265
that it's where
a modern jetliner would fly.
504
00:27:17,703 --> 00:27:19,703
Narrator: The k-pg asteroid
hit the ground
505
00:27:19,705 --> 00:27:23,907
with a lethal combination
of mass and speed.
506
00:27:23,909 --> 00:27:28,646
A trillion tons traveling
at 45,000 miles an hour.
507
00:27:30,583 --> 00:27:32,549
Some rock is
completely vaporized.
508
00:27:32,551 --> 00:27:34,251
It just becomes a gas.
509
00:27:34,253 --> 00:27:36,587
You have some rock
that is melted.
510
00:27:36,589 --> 00:27:39,823
You have some
that's thrown out into space.
511
00:27:41,661 --> 00:27:44,461
This material goes up
through that and then falls down
512
00:27:44,463 --> 00:27:46,730
and settles down
over a huge area.
513
00:27:46,732 --> 00:27:49,466
That might be dust.
It might be pulverized rock.
514
00:27:49,468 --> 00:27:51,669
It might be vaporized metal.
515
00:27:51,671 --> 00:27:55,005
It's all of this hot material
raining down everywhere.
516
00:27:57,276 --> 00:28:00,277
Narrator: Some of the rock
exploded skywards,
517
00:28:00,279 --> 00:28:03,814
but rock below the surface
was slammed by a shockwave
518
00:28:03,816 --> 00:28:06,650
that was completely
off the charts.
519
00:28:06,652 --> 00:28:11,255
Rock stopped behaving
like rock.
520
00:28:11,257 --> 00:28:14,224
We experience rocks
as solid objects,
521
00:28:14,226 --> 00:28:15,726
but if you hit a rock
hard enough,
522
00:28:15,728 --> 00:28:17,828
it flows like water.
523
00:28:17,830 --> 00:28:20,664
Narrator: The k-pg asteroid
hit so hard,
524
00:28:20,666 --> 00:28:22,566
it pulverized the rock,
525
00:28:22,568 --> 00:28:24,568
turning it into liquid.
526
00:28:24,570 --> 00:28:26,737
Almost like ripples
on a pond moving away
527
00:28:26,739 --> 00:28:29,173
from a stone
that's been dropped in it.
528
00:28:29,175 --> 00:28:30,574
Durda: It's almost like a splash
529
00:28:30,576 --> 00:28:32,876
in the solid body
of the earth itself,
530
00:28:32,878 --> 00:28:35,546
and like water droplets
splashing in water,
531
00:28:35,548 --> 00:28:39,016
you'll see that central peak
will kind of splash up
532
00:28:39,018 --> 00:28:41,719
and rise to a high altitude
and then come back down again.
533
00:28:41,721 --> 00:28:44,521
We think a process very similar
to that probably happened
534
00:28:44,523 --> 00:28:47,424
in the rock itself
at the center of the crater,
535
00:28:47,426 --> 00:28:49,960
rising up
as high as the himalayas
536
00:28:49,962 --> 00:28:53,063
before relaxing back down
to their current position again.
537
00:28:53,065 --> 00:28:56,600
Plesko: The material slumps,
and so these ripples
538
00:28:56,602 --> 00:28:58,302
are frozen in the rock,
539
00:28:58,304 --> 00:29:01,171
and there are other fragments
that go away radially,
540
00:29:01,173 --> 00:29:03,540
almost like the spider web
pattern in glass
541
00:29:03,542 --> 00:29:06,977
that you get after
it's shot with a bullet.
542
00:29:06,979 --> 00:29:10,581
Narrator: The k-pg impact
blew out a crater
543
00:29:10,583 --> 00:29:13,317
111 miles wide.
544
00:29:13,319 --> 00:29:15,786
It is the third largest
confirmed
545
00:29:15,788 --> 00:29:18,222
impact structure on earth.
546
00:29:20,493 --> 00:29:23,727
A large and fast asteroid
heading our way
547
00:29:23,729 --> 00:29:26,130
is always going to be a problem.
548
00:29:26,132 --> 00:29:28,465
So what do we do?
549
00:29:28,467 --> 00:29:32,035
Wait for oblivion?
550
00:29:32,037 --> 00:29:33,670
Or fight back?
551
00:29:47,887 --> 00:29:49,853
♪
552
00:29:49,855 --> 00:29:51,989
narrator: The space
in the inner solar system
553
00:29:51,991 --> 00:29:56,193
seems calm, stable, and empty.
554
00:29:56,195 --> 00:29:59,096
It's not.
555
00:29:59,098 --> 00:30:01,398
There are tens of thousands
of near earth objects
556
00:30:01,400 --> 00:30:03,033
just whizzing around earth.
557
00:30:03,035 --> 00:30:05,636
Now, space is big.
558
00:30:05,638 --> 00:30:09,940
They're not gonna hit us
every time they orbit the sun,
559
00:30:09,942 --> 00:30:12,309
but this does set up
the possibility
560
00:30:12,311 --> 00:30:14,545
that, one of these years,
561
00:30:14,547 --> 00:30:17,581
we're gonna end up
at the same spot in space
562
00:30:17,583 --> 00:30:20,551
at the same time
as that asteroid,
563
00:30:20,553 --> 00:30:22,186
and then it's gonna be
an impact.
564
00:30:24,623 --> 00:30:26,256
We're living in a cosmic
shooting gallery.
565
00:30:26,258 --> 00:30:28,258
Asteroids strike the earth
all the time
566
00:30:28,260 --> 00:30:29,860
through history,
567
00:30:29,862 --> 00:30:31,829
and it's gonna happen again.
568
00:30:31,831 --> 00:30:33,664
Narrator: Scientists are
developing strategies
569
00:30:33,666 --> 00:30:37,701
to stop an asteroid
from hitting our planet.
570
00:30:37,703 --> 00:30:42,773
Our options -- destroy
or deflect the space rock.
571
00:30:42,775 --> 00:30:46,276
But first, we need to detect
any dangerous asteroids
572
00:30:46,278 --> 00:30:48,145
heading our way.
573
00:30:48,147 --> 00:30:49,613
Stricker: It's a little bit
unnerving to know
574
00:30:49,615 --> 00:30:52,249
that we haven't yet detected
all of the asteroids
575
00:30:52,251 --> 00:30:55,085
that exist that could
possibly cross our path.
576
00:30:55,087 --> 00:30:57,221
We've discovered
a lot of asteroids now,
577
00:30:57,223 --> 00:31:01,091
but we typically discover
the big ones.
578
00:31:01,093 --> 00:31:03,894
But for asteroids
that are below 100 feet,
579
00:31:03,896 --> 00:31:06,763
there's a lot still out there
that we haven't discovered.
580
00:31:06,765 --> 00:31:09,399
And such an asteroid
can do some real damage
581
00:31:09,401 --> 00:31:13,470
if it were to explode
over a populated area.
582
00:31:13,472 --> 00:31:15,272
Narrator: To prevent
such a catastrophe,
583
00:31:15,274 --> 00:31:19,576
we need to find all asteroids
whose orbits cross our own.
584
00:31:19,578 --> 00:31:22,813
Detection is crucial in
our defense against asteroids.
585
00:31:22,815 --> 00:31:25,883
And the reason is the earlier
they're detected,
586
00:31:25,885 --> 00:31:29,853
the easier it is to deflect them
away from hitting the earth.
587
00:31:29,855 --> 00:31:32,923
You want to do deflection,
the first step is detection.
588
00:31:35,194 --> 00:31:37,728
Narrator: The problem is,
asteroids are very hard
589
00:31:37,730 --> 00:31:39,563
to detect.
590
00:31:39,565 --> 00:31:42,165
Finding asteroids
and cataloging all their orbits
591
00:31:42,167 --> 00:31:44,167
is really challenging.
592
00:31:44,169 --> 00:31:46,403
They can move quite fast
across the sky,
593
00:31:46,405 --> 00:31:48,305
and they might go away
594
00:31:48,307 --> 00:31:53,110
on the other side of the sun
for years and years and years.
595
00:31:53,112 --> 00:31:56,613
Narrator: So we can't see them.
596
00:31:56,615 --> 00:31:59,316
And even when they are
on this side of the sun,
597
00:31:59,318 --> 00:32:02,085
they're hard to spot.
598
00:32:02,087 --> 00:32:03,921
But the problem is,
they're very small
599
00:32:03,923 --> 00:32:05,322
and they're very dark,
600
00:32:05,324 --> 00:32:07,491
and when I say very dark,
I mean really dark,
601
00:32:07,493 --> 00:32:08,825
like a lump of coal.
602
00:32:08,827 --> 00:32:11,194
So how do you find
a small, dark rock
603
00:32:11,196 --> 00:32:13,830
just wandering around out there
in the solar system?
604
00:32:18,671 --> 00:32:22,306
Narrator: The catalina
sky survey has the answer.
605
00:32:24,643 --> 00:32:28,345
The huge telescope in the
mountains above tucson, arizona,
606
00:32:28,347 --> 00:32:33,116
takes a series of images
over a 20-minute period.
607
00:32:33,118 --> 00:32:35,986
It's hunting
for anything that moves
608
00:32:35,988 --> 00:32:39,756
because stars don't move,
but asteroids do.
609
00:32:42,261 --> 00:32:44,394
Man: If it's a really
bright asteroid,
610
00:32:44,396 --> 00:32:46,730
we will see some bright points
611
00:32:46,732 --> 00:32:50,901
of light
tracking across the four images.
612
00:32:50,903 --> 00:32:53,670
Ah, here we go.
613
00:32:53,672 --> 00:32:55,605
This is a real object.
614
00:32:55,607 --> 00:32:58,275
You can see it's moving
across the sky here
615
00:32:58,277 --> 00:33:00,777
from the lower right
to the upper left.
616
00:33:00,779 --> 00:33:04,081
We are very, very excited
to have discovered one tonight
617
00:33:04,083 --> 00:33:07,985
because this is an object
that's approaching near space,
618
00:33:07,987 --> 00:33:10,887
likely in the neighborhood
of earth.
619
00:33:14,560 --> 00:33:16,793
Narrator: Catalina
has limitations.
620
00:33:16,795 --> 00:33:19,596
It can only see visible light,
621
00:33:19,598 --> 00:33:25,202
so a particularly dim asteroid
could be missed.
622
00:33:25,204 --> 00:33:26,703
Thaller:
Asteroids are very cold.
623
00:33:26,705 --> 00:33:28,638
They're usually quite far away
from the sun,
624
00:33:28,640 --> 00:33:30,073
but amazingly, the best way
625
00:33:30,075 --> 00:33:32,843
we have to find these
is infrared light
626
00:33:32,845 --> 00:33:35,278
because things that are cold
by human scales
627
00:33:35,280 --> 00:33:37,914
can still be very warm
to an infrared telescope.
628
00:33:37,916 --> 00:33:40,684
So even if asteroids are just
a few tens of degrees
629
00:33:40,686 --> 00:33:41,818
above absolute zero,
630
00:33:41,820 --> 00:33:45,522
that's still enough heat
to detect them.
631
00:33:45,524 --> 00:33:48,225
Narrator: When the infrared
space telescope neowise
632
00:33:48,227 --> 00:33:51,361
turned its gaze
onto asteroids,
633
00:33:51,363 --> 00:33:53,864
it had immediate results.
634
00:33:53,866 --> 00:33:55,365
Thaller:
Neowise has now detected
635
00:33:55,367 --> 00:34:00,237
close to 160,000 new asteroids
and comets in our solar system,
636
00:34:00,239 --> 00:34:02,139
and about 780 of those
637
00:34:02,141 --> 00:34:04,307
are things
that are near the earth.
638
00:34:04,309 --> 00:34:07,110
Narrator: 10 of those near
objects have been classified
639
00:34:07,112 --> 00:34:12,616
as p.H.A.S --
potentially hazardous asteroids.
640
00:34:12,618 --> 00:34:15,986
Without neowise,
we would have missed them.
641
00:34:15,988 --> 00:34:17,487
Using an infrared
space telescope
642
00:34:17,489 --> 00:34:22,792
is a way of of better detecting
some of the smaller asteroids
643
00:34:22,794 --> 00:34:26,263
and comets
in the near earth vicinity.
644
00:34:26,265 --> 00:34:29,066
Narrator: Detection is
an important first step,
645
00:34:29,068 --> 00:34:30,333
but it only tells us
646
00:34:30,335 --> 00:34:32,969
that there is
another asteroid out there.
647
00:34:32,971 --> 00:34:34,905
Once we've spotted
an asteroid,
648
00:34:34,907 --> 00:34:37,774
all we know is that
it's a tiny dot of light.
649
00:34:37,776 --> 00:34:40,210
We don't know anything else
about it.
650
00:34:40,212 --> 00:34:42,145
So when a new asteroid
is discovered,
651
00:34:42,147 --> 00:34:43,413
the most important thing is
652
00:34:43,415 --> 00:34:45,916
to determine its path,
to track it, to figure out
653
00:34:45,918 --> 00:34:47,751
exactly how it's orbiting
around the sun
654
00:34:47,753 --> 00:34:49,519
and how close
it's gonna get to earth.
655
00:34:49,521 --> 00:34:51,254
For that, we have to know
where they are now --
656
00:34:51,256 --> 00:34:54,925
so its current location --
and measure how fast it's going
657
00:34:54,927 --> 00:34:57,060
and which direction
it's travelling.
658
00:34:57,062 --> 00:34:59,162
All of these things together
are really important
659
00:34:59,164 --> 00:35:00,997
for tracking
where it's gonna be next
660
00:35:00,999 --> 00:35:03,166
and whether or not
they're gonna hit us.
661
00:35:05,370 --> 00:35:06,636
Narrator:
To get this information,
662
00:35:06,638 --> 00:35:09,539
we need something much bigger
and more powerful.
663
00:35:11,910 --> 00:35:14,911
The arecibo observatory.
664
00:35:14,913 --> 00:35:16,947
Once catalina
or another telescope
665
00:35:16,949 --> 00:35:20,717
detects a near earth asteroid
in our cosmic neighborhood,
666
00:35:20,719 --> 00:35:26,056
arecibo's thousand-foot dish
swings into action.
667
00:35:26,058 --> 00:35:27,824
They discover
these asteroids,
668
00:35:27,826 --> 00:35:30,827
and then once we know
where they were,
669
00:35:30,829 --> 00:35:33,530
we can try and point
the radio telescope
670
00:35:33,532 --> 00:35:35,365
and see where they are
at the moment
671
00:35:35,367 --> 00:35:40,570
and measure their exact location
and their trajectory.
672
00:35:40,572 --> 00:35:43,540
Narrator: Arecibo achieves
this level of precision
673
00:35:43,542 --> 00:35:46,510
by using radio detection
and ranging,
674
00:35:46,512 --> 00:35:49,246
more commonly known
as radar.
675
00:35:49,248 --> 00:35:51,948
The planetary radar system
at arecibo observatory
676
00:35:51,950 --> 00:35:55,051
is the most powerful
radar system in the world.
677
00:35:55,053 --> 00:35:58,054
We focus on
potentially hazardous asteroids,
678
00:35:58,056 --> 00:36:03,393
which are those that have a high
probability of impacting earth.
679
00:36:03,395 --> 00:36:05,328
Narrator: Arecibo sends out
radio signals
680
00:36:05,330 --> 00:36:07,330
toward the newly
detected asteroid.
681
00:36:07,332 --> 00:36:09,466
Sutter:
It emanates radio signals.
682
00:36:09,468 --> 00:36:14,137
Some of them hit the asteroid
just like a radar gun from a cop
683
00:36:14,139 --> 00:36:16,139
might hit the side of your car.
684
00:36:16,141 --> 00:36:17,374
Zambrano-marin:
That's pretty similar,
685
00:36:17,376 --> 00:36:19,209
but instead of doing it
with a radar gun
686
00:36:19,211 --> 00:36:21,945
on the small scale, we're
doing at a really big scale
687
00:36:21,947 --> 00:36:25,115
with one megawatt power
hitting objects that are
688
00:36:25,117 --> 00:36:27,350
tens of lunar distances away.
689
00:36:27,352 --> 00:36:30,887
Sutter: And then those radio
waves bounce back to earth
690
00:36:30,889 --> 00:36:35,158
and we detect them again,
and by comparing the differences
691
00:36:35,160 --> 00:36:38,195
between what we sent
and what we received,
692
00:36:38,197 --> 00:36:41,765
we can get a map
of the asteroid itself
693
00:36:41,767 --> 00:36:46,603
and we can get where it's moving
and how fast it's moving.
694
00:36:46,605 --> 00:36:49,639
Narrator: Speed, size,
and location of strike
695
00:36:49,641 --> 00:36:53,710
determine the outcome
of an asteroid impact.
696
00:36:53,712 --> 00:36:57,180
But the type of asteroid
is another factor.
697
00:36:57,182 --> 00:36:59,950
It can mean the difference
between survival
698
00:36:59,952 --> 00:37:02,686
or complete annihilation.
699
00:37:15,601 --> 00:37:19,803
♪
700
00:37:19,805 --> 00:37:23,440
narrator:
The bering sea asteroid
blew up in the atmosphere,
701
00:37:23,442 --> 00:37:27,544
but the barringer crater
asteroid hit the ground intact
702
00:37:27,546 --> 00:37:29,179
with its full force.
703
00:37:31,516 --> 00:37:35,018
Why do different asteroids
behave differently?
704
00:37:35,020 --> 00:37:38,521
And what will apophis do
when it heads our way?
705
00:37:40,692 --> 00:37:44,594
Arecibo's radar
may have the answer.
706
00:37:44,596 --> 00:37:47,631
When we bounce radar waves
off of these objects,
707
00:37:47,633 --> 00:37:51,034
we can get effectively imagery
of the surface
708
00:37:51,036 --> 00:37:52,602
of some of these small objects
709
00:37:52,604 --> 00:37:56,406
that we just cannot do
with optical telescopes.
710
00:37:56,408 --> 00:37:59,242
Narrator: This is
the radar image of apophis.
711
00:37:59,244 --> 00:38:02,912
It's so far away that all they
could image were a few pixels.
712
00:38:05,751 --> 00:38:08,418
So this is our most recent
radar image
713
00:38:08,420 --> 00:38:11,421
of asteroid apophis.
714
00:38:11,423 --> 00:38:14,791
And you can see
it's only a few pixels,
715
00:38:14,793 --> 00:38:16,893
but it does give us
information
716
00:38:16,895 --> 00:38:20,563
on what it actually is.
717
00:38:20,565 --> 00:38:23,133
Narrator: These few pixels
are enough to work out
718
00:38:23,135 --> 00:38:26,736
how big apophis is.
719
00:38:26,738 --> 00:38:29,739
Virkki: From this image,
we can constrain the size
720
00:38:29,741 --> 00:38:32,042
to be about 1,000 feet,
721
00:38:32,044 --> 00:38:34,678
which is about the same size
as the arecibo
722
00:38:34,680 --> 00:38:37,080
radio telescope.
723
00:38:37,082 --> 00:38:40,517
All of that from what were
a bunch of pixels.
724
00:38:43,455 --> 00:38:46,222
♪
725
00:38:46,224 --> 00:38:48,391
narrator: Knowing the size
and mass of an asteroid
726
00:38:48,393 --> 00:38:53,730
is critical to understanding
what an asteroid is made of.
727
00:38:53,732 --> 00:38:56,499
If we have the size and
the mass, we get the density.
728
00:38:56,501 --> 00:38:58,935
If we have the density,
we know what it's made of.
729
00:38:58,937 --> 00:39:02,939
Rock has some density.
Metal has a different density.
730
00:39:02,941 --> 00:39:06,009
So we can determine
a huge amount about the asteroid
731
00:39:06,011 --> 00:39:08,578
simply by pinging it
with radar.
732
00:39:11,550 --> 00:39:13,083
Narrator: Arecibo's data reveals
733
00:39:13,085 --> 00:39:15,518
that not all asteroids
are alike.
734
00:39:17,522 --> 00:39:19,556
There's not just
one kind of asteroid.
735
00:39:19,558 --> 00:39:21,324
There are actually
several kinds,
736
00:39:21,326 --> 00:39:23,226
and this is important
to understand
737
00:39:23,228 --> 00:39:25,095
because they behave differently.
738
00:39:25,097 --> 00:39:27,163
They behave differently
if they impact us,
739
00:39:27,165 --> 00:39:29,766
and they behave differently
if we're trying to prevent them
740
00:39:29,768 --> 00:39:31,101
from impacting us.
741
00:39:31,103 --> 00:39:34,637
We need to know what these
asteroids are made of
742
00:39:34,639 --> 00:39:36,005
if they're gonna hit
the earth
743
00:39:36,007 --> 00:39:40,310
because that drastically alters
the potential effects.
744
00:39:40,312 --> 00:39:43,446
Asteroids come in different
shapes, different sizes,
745
00:39:43,448 --> 00:39:46,383
and different compositions,
and we think that is
746
00:39:46,385 --> 00:39:49,953
because they are the leftovers
of planet formation.
747
00:39:49,955 --> 00:39:52,822
Narrator: To understand how
each asteroid formed
748
00:39:52,824 --> 00:39:54,758
and their threat level,
we have to go back
749
00:39:54,760 --> 00:40:00,130
4.6 billion years to the start
of the solar system.
750
00:40:00,132 --> 00:40:02,132
The reason that there are
all these asteroids
751
00:40:02,134 --> 00:40:04,501
floating around
in our solar system today
752
00:40:04,503 --> 00:40:07,370
is just because of the early
violence of the solar system
753
00:40:07,372 --> 00:40:09,005
as it was forming.
754
00:40:11,810 --> 00:40:13,410
Narrator: At the birth
of the solar system,
755
00:40:13,412 --> 00:40:16,446
the sun ignites,
756
00:40:16,448 --> 00:40:19,449
leaving a disk of gas and dust.
757
00:40:22,988 --> 00:40:27,056
Slowly, over time,
planets form.
758
00:40:27,058 --> 00:40:29,692
Lots of planets.
759
00:40:29,694 --> 00:40:33,096
Sutter: The early solar system
was a messy place.
760
00:40:33,098 --> 00:40:36,466
There were a lot more planets,
a lot more forming planets.
761
00:40:36,468 --> 00:40:38,168
They would crash in
to each other,
762
00:40:38,170 --> 00:40:40,203
they would merge,
they would disintegrate,
763
00:40:40,205 --> 00:40:42,472
they would re-form.
764
00:40:45,210 --> 00:40:48,445
This process of accretion
of building planetary worlds
765
00:40:48,447 --> 00:40:51,848
was not just, you know,
kind of gentle and happy.
766
00:40:51,850 --> 00:40:54,250
It was violent.
767
00:40:54,252 --> 00:40:57,220
Narrator: It was like a giant
cosmic game of pool --
768
00:40:57,222 --> 00:40:59,889
planet smashing into planet.
769
00:41:03,128 --> 00:41:05,361
The leftovers
from this violence
770
00:41:05,363 --> 00:41:09,632
formed a ring of junk
between mars and jupiter.
771
00:41:09,634 --> 00:41:12,068
And now we call
that junk asteroids.
772
00:41:12,070 --> 00:41:13,837
They're just basically
rubble left over
773
00:41:13,839 --> 00:41:16,005
from the formation
of the solar system.
774
00:41:20,345 --> 00:41:23,112
Narrator: Rocky leftovers
became c-type
775
00:41:23,114 --> 00:41:26,749
or chondrite asteroids.
776
00:41:26,751 --> 00:41:30,353
They're quite dense, so big ones
can punch through the atmosphere
777
00:41:30,355 --> 00:41:31,955
and hit the ground.
778
00:41:35,327 --> 00:41:40,296
Radar reveals
a rarer type of asteroid.
779
00:41:40,298 --> 00:41:42,899
Some of them really stand out
because their density
780
00:41:42,901 --> 00:41:46,970
is so much higher than the rest
of the other asteroids.
781
00:41:46,972 --> 00:41:50,540
Narrator: These asteroids
are m-type or metal.
782
00:41:53,178 --> 00:41:55,144
Because their mass is great,
783
00:41:55,146 --> 00:41:59,449
they carry more kinetic energy
during a strike.
784
00:41:59,451 --> 00:42:03,152
By far, the worst one
is this iron meteorite.
785
00:42:03,154 --> 00:42:06,222
This is really heavy,
so the difference --
786
00:42:06,224 --> 00:42:07,690
if you were being hit
by this,
787
00:42:07,692 --> 00:42:09,993
it would be the difference
between being hit by a rock
788
00:42:09,995 --> 00:42:14,330
and being hit
by a metal hammer.
789
00:42:14,332 --> 00:42:16,332
Narrator: We think that both
the barringer
790
00:42:16,334 --> 00:42:18,668
and the k-pg dinosaur killer
791
00:42:18,670 --> 00:42:21,104
were caused by metal asteroids.
792
00:42:23,975 --> 00:42:26,643
But there's another more
mysterious type
793
00:42:26,645 --> 00:42:28,344
floating through space.
794
00:42:28,346 --> 00:42:34,651
♪
795
00:42:34,653 --> 00:42:36,619
December 2018,
796
00:42:36,621 --> 00:42:39,856
nasa's spacecraft osiris-rex
approached
797
00:42:39,858 --> 00:42:43,660
the near earth asteroid bennu.
798
00:42:43,662 --> 00:42:46,696
Walsh: Over time, it drifted out
of the main asteroid belt,
799
00:42:46,698 --> 00:42:48,865
made its way into
the inner solar system,
800
00:42:48,867 --> 00:42:51,000
until it became
a near earth asteroid,
801
00:42:51,002 --> 00:42:54,837
accessible for our spacecraft
to go and visit.
802
00:42:54,839 --> 00:42:57,574
Narrator: Osiris trained
its camera on bennu.
803
00:42:57,576 --> 00:43:04,747
♪
804
00:43:04,749 --> 00:43:07,350
one of the biggest surprises
on arrival of bennu
805
00:43:07,352 --> 00:43:11,120
was the large number of
large boulders on its surface.
806
00:43:11,122 --> 00:43:13,590
Bennu is really littered
with huge boulders
807
00:43:13,592 --> 00:43:15,925
and littered
with medium-sized boulders
808
00:43:15,927 --> 00:43:18,161
and littered
with small boulders.
809
00:43:18,163 --> 00:43:20,830
Narrator: Bennu is not
a solid lump of rock.
810
00:43:20,832 --> 00:43:23,533
It's made up of thousands
of bits of rock
811
00:43:23,535 --> 00:43:27,136
forming what we call
a rubble pile.
812
00:43:27,138 --> 00:43:31,007
These asteroids aren't big,
singular, spherical balls
813
00:43:31,009 --> 00:43:32,141
of rock,
814
00:43:32,143 --> 00:43:34,644
but rather they're literally
piles of rubble.
815
00:43:34,646 --> 00:43:36,379
They're all sorts
of pieces and fragments
816
00:43:36,381 --> 00:43:38,214
from another asteroid
that had previously
817
00:43:38,216 --> 00:43:41,217
been disrupted
that have all come back together
818
00:43:41,219 --> 00:43:43,987
and formed literally a pile
of rocks held together
819
00:43:43,989 --> 00:43:45,555
by their own gravity.
820
00:43:45,557 --> 00:43:48,324
Narrator: We think rubble piles
formed from collisions
821
00:43:48,326 --> 00:43:53,563
inside the asteroid belt
each impact blasted bits off.
822
00:43:53,565 --> 00:43:56,332
Then, over time,
they came back together
823
00:43:56,334 --> 00:43:59,335
to form a loose pile of rocks.
824
00:43:59,337 --> 00:44:01,738
Durda: Imagine taking
a big cosmic dump truck
825
00:44:01,740 --> 00:44:03,673
full of gravel and rubble
826
00:44:03,675 --> 00:44:05,541
and dumping it
out there in the space
827
00:44:05,543 --> 00:44:08,611
and letting gravity
weakly hold it together.
828
00:44:10,782 --> 00:44:13,750
Narrator: When scientists probe
deeper into bennu,
829
00:44:13,752 --> 00:44:15,652
they found another surprise.
830
00:44:15,654 --> 00:44:19,656
It's full of holes,
like swiss cheese.
831
00:44:19,658 --> 00:44:22,191
If you could slice open
one of these asteroids,
832
00:44:22,193 --> 00:44:24,327
you'd see there are
a lot of voids.
833
00:44:24,329 --> 00:44:28,231
In fact, 60% of what we're
looking at is a void space,
834
00:44:28,233 --> 00:44:30,199
so they're actually
really fluffy.
835
00:44:30,201 --> 00:44:31,567
So even though
they're made of rocks,
836
00:44:31,569 --> 00:44:35,104
they're sort of
the lint of rocks.
837
00:44:35,106 --> 00:44:38,041
Narrator: Bennu helps us
understand apophis.
838
00:44:38,043 --> 00:44:43,079
Radar data shows that
apophis is also a rubble pile.
839
00:44:43,081 --> 00:44:44,781
If you look at apophis,
we really want to know
840
00:44:44,783 --> 00:44:47,083
how its orbit will evolve
in the future.
841
00:44:47,085 --> 00:44:49,419
What we learn at bennu
about similar-sized
842
00:44:49,421 --> 00:44:51,954
rubble-pile asteroids
might help us understand
843
00:44:51,956 --> 00:44:54,991
the future of an asteroid
like apophis.
844
00:44:54,993 --> 00:44:57,060
Narrator: So what would happen
if the rubble pile
845
00:44:57,062 --> 00:44:59,062
called apophis hits earth?
846
00:44:59,064 --> 00:45:00,963
Durda: You probably don't want
that to hit you still,
847
00:45:00,965 --> 00:45:03,166
but it definitely
makes it a lot weaker
848
00:45:03,168 --> 00:45:05,435
than something like a solid rock
849
00:45:05,437 --> 00:45:10,206
or even more, a chunk
of nickel iron metal.
850
00:45:10,208 --> 00:45:14,043
Narrator: Does its composition
make it any less of a threat?
851
00:45:14,045 --> 00:45:17,246
A rubble pile like apophis
is especially unnerving
852
00:45:17,248 --> 00:45:19,916
because we don't know, when it
interacts with the atmosphere,
853
00:45:19,918 --> 00:45:21,984
if it's gonna stay
as one solid piece,
854
00:45:21,986 --> 00:45:24,353
will it break up.
855
00:45:24,355 --> 00:45:27,724
When these rubble piles
start interacting with planets,
856
00:45:27,726 --> 00:45:30,293
if they fly near a planet,
they can get pulled apart
857
00:45:30,295 --> 00:45:32,128
into all of their little pieces.
858
00:45:32,130 --> 00:45:34,697
Or if they enter
the atmosphere of a planet
859
00:45:34,699 --> 00:45:38,301
to impact the surface, they
might slowly get pulled apart
860
00:45:38,303 --> 00:45:40,036
as they enter the atmosphere
861
00:45:40,038 --> 00:45:42,505
and end up being
an array of little impacts
862
00:45:42,507 --> 00:45:44,407
instead of one big
single impact.
863
00:45:46,344 --> 00:45:53,549
♪
864
00:45:53,551 --> 00:45:59,322
narrator: But what would happen
if these impacts occur at sea?
865
00:45:59,324 --> 00:46:01,290
Will our oceans save us,
866
00:46:01,292 --> 00:46:05,161
or will a giant tsunami
wipe us out?
867
00:46:17,375 --> 00:46:19,041
Narrator: 2019,
868
00:46:19,043 --> 00:46:23,613
u.S. Researchers
discover deposits of fossils.
869
00:46:23,615 --> 00:46:29,452
They contain both the remains
of land and sea creatures.
870
00:46:29,454 --> 00:46:31,854
You see things that
are all jumbled together,
871
00:46:31,856 --> 00:46:35,224
so you'll have fossils
of sea creatures.
872
00:46:35,226 --> 00:46:39,328
You'll have ocean deposits
that are mixed up
873
00:46:39,330 --> 00:46:42,799
with coastal deposits
and onshore deposits,
874
00:46:42,801 --> 00:46:45,902
and you see those deposits
in places
875
00:46:45,904 --> 00:46:47,270
that are very, very far away
876
00:46:47,272 --> 00:46:49,672
from where you would
expect them to be.
877
00:46:49,674 --> 00:46:51,908
And so this material was
obviously thrown
878
00:46:51,910 --> 00:46:54,877
very far inland.
879
00:46:54,879 --> 00:46:56,245
Narrator: The jumbled deposits
880
00:46:56,247 --> 00:46:59,649
suggest that the creatures
were killed at the same time
881
00:46:59,651 --> 00:47:02,919
in a huge and violent event,
882
00:47:02,921 --> 00:47:04,554
something powerful enough
883
00:47:04,556 --> 00:47:09,692
to sweep ocean-dwelling
creatures far inland.
884
00:47:09,694 --> 00:47:11,861
A tsunami.
885
00:47:11,863 --> 00:47:14,030
Tsunamis are usually created
886
00:47:14,032 --> 00:47:17,033
when the ocean floor
moves suddenly.
887
00:47:17,035 --> 00:47:19,869
The ground picks up
the entire ocean
888
00:47:19,871 --> 00:47:21,771
and shakes it up and down,
889
00:47:21,773 --> 00:47:24,040
and it's sort of like
taking a rope and shaking it,
890
00:47:24,042 --> 00:47:26,642
and it moves all across
the ocean floor
891
00:47:26,644 --> 00:47:29,145
and ocean surface
until it reaches land.
892
00:47:29,147 --> 00:47:33,482
The biggest recent tsunami
was caused by the earth's crust
893
00:47:33,484 --> 00:47:35,985
at the bottom of the ocean
lifting slightly,
894
00:47:35,987 --> 00:47:39,188
so this means that
that entire length of crust
895
00:47:39,190 --> 00:47:42,358
that lifted displaced
the water above it,
896
00:47:42,360 --> 00:47:45,361
so the waves,
the tsunamis that result,
897
00:47:45,363 --> 00:47:47,496
are really long and wide,
898
00:47:47,498 --> 00:47:49,732
and it can travel
across the ocean
899
00:47:49,734 --> 00:47:54,537
at tremendous speeds
and up on land.
900
00:47:54,539 --> 00:47:57,139
Narrator: Is this what happened
to the fossilized creatures?
901
00:47:57,141 --> 00:48:01,611
Were they killed
by a huge tsunami?
902
00:48:01,613 --> 00:48:05,615
Clues come from dating
the preserved remains.
903
00:48:05,617 --> 00:48:09,252
They're 66 million years old.
904
00:48:09,254 --> 00:48:11,821
From the same time
a six-mile-wide asteroid
905
00:48:11,823 --> 00:48:16,359
crashed into the sea off
the yucatán peninsula in mexico.
906
00:48:20,131 --> 00:48:22,331
Are the two events connected?
907
00:48:22,333 --> 00:48:26,869
Do ocean-impacting asteroids
trigger tsunamis?
908
00:48:26,871 --> 00:48:28,371
We used to think
that a big asteroid
909
00:48:28,373 --> 00:48:31,941
impacting in the ocean would
drive a tremendous tsunami,
910
00:48:31,943 --> 00:48:35,745
a huge wall of water
out at very rapid speeds,
911
00:48:35,747 --> 00:48:38,848
which would basically
scour clean everything.
912
00:48:38,850 --> 00:48:41,817
Narrator: Now new research
from 2018 suggests
913
00:48:41,819 --> 00:48:44,353
a very different scenario.
914
00:48:44,355 --> 00:48:47,957
Scientists use super computers
to model asteroids
915
00:48:47,959 --> 00:48:51,560
hitting the deep ocean
to work out how much of
916
00:48:51,562 --> 00:48:55,865
the asteroid's kinetic energy
is converted into a tsunami.
917
00:48:58,770 --> 00:49:02,271
In the simulations,
a 1,600-foot asteroid
918
00:49:02,273 --> 00:49:05,408
hits the ocean at
20,000 miles an hour
919
00:49:05,410 --> 00:49:08,978
and dives into the water.
920
00:49:08,980 --> 00:49:12,548
As it goes deeper in,
of course it's meeting a lot
921
00:49:12,550 --> 00:49:15,484
of resistance and it slows down
and it compresses up.
922
00:49:15,486 --> 00:49:18,921
It compresses and compresses
and compresses, and then finally
923
00:49:18,923 --> 00:49:20,589
it runs out of momentum,
924
00:49:20,591 --> 00:49:23,326
and it's at an extremely
high pressure.
925
00:49:24,395 --> 00:49:28,931
Narrator: The huge pressure
causes the asteroid to vaporize.
926
00:49:28,933 --> 00:49:31,867
Temperatures hotter than
the surface of the sun
927
00:49:31,869 --> 00:49:35,938
turn trillions
of gallons of water into steam.
928
00:49:36,541 --> 00:49:40,142
The blast creates a huge
short lived cavity
929
00:49:40,144 --> 00:49:42,511
in the water's surface
930
00:49:42,513 --> 00:49:44,947
and a splash curtain,
a wall of water,
931
00:49:44,949 --> 00:49:47,850
that leaps up several miles.
932
00:49:47,852 --> 00:49:50,786
This curtain then collapses
and water falls
933
00:49:50,788 --> 00:49:54,223
back into the cavity,
shooting a column of water
934
00:49:54,225 --> 00:49:56,759
five miles up.
935
00:49:56,761 --> 00:49:59,628
Plesko: This very tall column
can't support its own weight
936
00:49:59,630 --> 00:50:02,999
and collapses back down.
937
00:50:03,001 --> 00:50:05,534
Narrator: The collapse of
so much water triggers
938
00:50:05,536 --> 00:50:08,671
a wave 1,200 feet high.
939
00:50:08,673 --> 00:50:12,074
Could this become
a huge tsunami?
940
00:50:16,614 --> 00:50:18,714
If we think about a meteor
striking the ocean,
941
00:50:18,716 --> 00:50:21,017
we want to understand
how far the waves
942
00:50:21,019 --> 00:50:22,585
might propagate from the site.
943
00:50:22,587 --> 00:50:25,821
We could actually just use a
stone and throw it into a pond,
944
00:50:25,823 --> 00:50:27,957
and you might think,
"okay, well, it's a big stone,
945
00:50:27,959 --> 00:50:29,325
it's going to make
a really big splash,
946
00:50:29,327 --> 00:50:31,794
and that's just going to
extend out a long distance."
947
00:50:31,796 --> 00:50:34,964
but it turns out the splash
stays the biggest really close
948
00:50:34,966 --> 00:50:36,098
to where it impacts.
949
00:50:36,100 --> 00:50:37,566
And then the ripples
die down after that.
950
00:50:37,568 --> 00:50:39,268
So let's try that.
951
00:50:40,571 --> 00:50:43,105
Big splash in the middle.
952
00:50:43,107 --> 00:50:44,573
And we see the ripples
going outward,
953
00:50:44,575 --> 00:50:45,941
but they're really
pretty small compared
954
00:50:45,943 --> 00:50:48,277
with that initial big splash.
955
00:50:49,680 --> 00:50:53,749
Narrator: It's the same with
an ocean impacting asteroid.
956
00:50:53,751 --> 00:50:58,020
The impact creates surface
waves that die away quickly
957
00:50:58,022 --> 00:51:01,590
because only a small amount
of the asteroid's kinetic energy
958
00:51:01,592 --> 00:51:03,292
gets into the water.
959
00:51:03,294 --> 00:51:05,361
Plait: It's actually
pretty tough to make
960
00:51:05,363 --> 00:51:06,629
a tsunami like that.
961
00:51:06,631 --> 00:51:08,931
The energy of the asteroid
doesn't couple well
962
00:51:08,933 --> 00:51:11,467
with the water
to drive this wave.
963
00:51:11,469 --> 00:51:12,968
Instead, most of the energy
964
00:51:12,970 --> 00:51:15,871
goes into vaporizing
the asteroid itself
965
00:51:15,873 --> 00:51:19,075
as well as all of the water
around it.
966
00:51:19,077 --> 00:51:21,844
Narrator: Only 1% of
the asteroid's kinetic energy
967
00:51:21,846 --> 00:51:24,013
goes into making a wave.
968
00:51:24,015 --> 00:51:28,451
So only low energy waves form,
too weak to become
969
00:51:28,453 --> 00:51:32,855
giant tsunamis
traveling hundreds of miles.
970
00:51:32,857 --> 00:51:35,558
So what caused
the jumbled fossil deposits
971
00:51:35,560 --> 00:51:39,829
found thousands of miles away
from the impact site?
972
00:51:39,831 --> 00:51:41,797
Radebaugh: We don't think there
could be that much energy
973
00:51:41,799 --> 00:51:45,768
still transmitted that far away
from the impact site.
974
00:51:45,770 --> 00:51:48,637
Instead, there has to be
a different source of energy
975
00:51:48,639 --> 00:51:50,639
that created different waves
976
00:51:50,641 --> 00:51:53,676
right about the same time
as that impact event.
977
00:51:55,480 --> 00:51:58,814
Narrator: Research from 2019
may have the answer.
978
00:51:58,816 --> 00:52:02,685
The kpg asteroid struck
on the continental shelf,
979
00:52:02,687 --> 00:52:06,222
the shallow region between land
and deep ocean.
980
00:52:06,224 --> 00:52:10,159
The impact triggered a localized
tsunami large enough
981
00:52:10,161 --> 00:52:13,095
to kill creatures in the region.
982
00:52:13,097 --> 00:52:16,532
But it also sent a huge
shock wave into the bedrock.
983
00:52:18,402 --> 00:52:20,035
There's going to be
a shock wave driven
984
00:52:20,037 --> 00:52:21,303
through the ground.
985
00:52:21,305 --> 00:52:23,772
That probably would have
killed anything in the area.
986
00:52:23,774 --> 00:52:28,511
If you had a dinosaur
that was standing on
987
00:52:28,513 --> 00:52:33,149
the gulf coast of what is now
the united states,
988
00:52:33,151 --> 00:52:38,621
that animal would have
experienced a seismic pulse,
989
00:52:38,623 --> 00:52:41,390
an earthquake that is stronger
than anything
990
00:52:41,392 --> 00:52:43,225
on our current richter scale.
991
00:52:43,227 --> 00:52:46,428
It would have actually driven
its legs up into its body cavity
992
00:52:46,430 --> 00:52:47,596
killing it instantly.
993
00:52:47,598 --> 00:52:50,499
There's all manner of mayhem
and death
994
00:52:50,501 --> 00:52:51,901
taking place at this time.
995
00:52:51,903 --> 00:52:53,903
There was no escaping
this event.
996
00:52:55,573 --> 00:52:59,275
Narrator: The initial shock wave
smashed into the ground rock
997
00:52:59,277 --> 00:53:03,045
and traveled through
the earth's crust.
998
00:53:03,047 --> 00:53:06,682
The impact would have shaken
the crust of the earth,
999
00:53:06,684 --> 00:53:09,618
which also would have triggered
earthquakes around the world,
1000
00:53:09,620 --> 00:53:13,622
which themselves may have
triggered secondary salamis.
1001
00:53:16,694 --> 00:53:19,929
Narrator: Secondary tsunamis
thousands of miles from
1002
00:53:19,931 --> 00:53:24,099
the impact site killed both
land and sea creatures.
1003
00:53:24,101 --> 00:53:31,507
The kpg impact went on to wipe
out 70% of all life on earth.
1004
00:53:31,509 --> 00:53:37,146
So how did one asteroid
strike cause a global kill zone?
1005
00:53:37,148 --> 00:53:39,348
♪
1006
00:53:46,023 --> 00:53:55,364
♪
1007
00:53:55,366 --> 00:54:00,402
narrator: 66 million years ago,
70% of life on earth died
1008
00:54:00,404 --> 00:54:03,639
after the kpg asteroid strike.
1009
00:54:07,345 --> 00:54:10,980
How could one space rocket
hitting the sea cause
1010
00:54:10,982 --> 00:54:13,082
a global catastrophe?
1011
00:54:14,485 --> 00:54:17,253
Lanza: When you have a big rock
hitting the ocean,
1012
00:54:17,255 --> 00:54:19,855
the biggest danger
is not from the waves
1013
00:54:19,857 --> 00:54:23,559
but actually from the steam
that it creates.
1014
00:54:23,561 --> 00:54:27,630
Narrator: The impact vaporized
trillions of tons of seawater.
1015
00:54:27,632 --> 00:54:30,566
This steam rose up
into the atmosphere
1016
00:54:30,568 --> 00:54:34,236
where it condensed
into water vapor.
1017
00:54:34,238 --> 00:54:36,305
Water vapor is a greenhouse gas.
1018
00:54:36,307 --> 00:54:39,408
So that's done going up
into the upper atmosphere,
1019
00:54:39,410 --> 00:54:42,177
and it's trapping heat,
1020
00:54:42,179 --> 00:54:44,413
but at different layers
it's making clouds.
1021
00:54:44,415 --> 00:54:47,049
It's just throwing
everything off kilter.
1022
00:54:47,051 --> 00:54:49,485
Water is a very effective
greenhouse gas as you
1023
00:54:49,487 --> 00:54:52,988
will actually affect some very
significant climate change
1024
00:54:52,990 --> 00:54:55,591
very quickly
as a result of that impact.
1025
00:54:57,495 --> 00:54:59,695
Narrator: Within weeks
of the asteroid strike,
1026
00:54:59,697 --> 00:55:03,999
water vapor in the atmosphere
caused temperatures to rise.
1027
00:55:05,102 --> 00:55:07,703
But that was only the start.
1028
00:55:08,873 --> 00:55:13,042
The impact also blew out
10 trillion tons of rock,
1029
00:55:13,044 --> 00:55:15,311
ash, and dust.
1030
00:55:16,681 --> 00:55:20,115
This asteroid is so big,
six miles wide.
1031
00:55:20,117 --> 00:55:21,784
It's punched a hole in the air.
1032
00:55:21,786 --> 00:55:24,486
There's like a column
of low density, a chimney,
1033
00:55:24,488 --> 00:55:27,523
that goes from the ground up to
the top of the atmosphere.
1034
00:55:27,525 --> 00:55:29,858
And that means there's
very little air resistance
1035
00:55:29,860 --> 00:55:31,427
in that tunnel.
1036
00:55:31,429 --> 00:55:34,196
These rocks can actually
blast up into the chimney
1037
00:55:34,198 --> 00:55:36,899
and find it easier
to get up out of the atmosphere.
1038
00:55:36,901 --> 00:55:40,369
It sent that material
flying up halfway
1039
00:55:40,371 --> 00:55:43,739
to the orbit of the moon,
circled around the earth.
1040
00:55:43,741 --> 00:55:47,843
All this ring of material
falling back on to the earth.
1041
00:55:47,845 --> 00:55:51,580
And it was like the sky itself
was on fire.
1042
00:55:51,582 --> 00:55:53,549
Lanza: So not only do you
have rocks falling on you,
1043
00:55:53,551 --> 00:55:56,085
but they're molten,
and these rocks
1044
00:55:56,087 --> 00:56:00,556
will start catching plants
and anything else on fire.
1045
00:56:00,558 --> 00:56:05,494
♪
1046
00:56:05,496 --> 00:56:09,331
narrator: Soot and ash rose
into the atmosphere
1047
00:56:09,333 --> 00:56:11,633
blocking out the sun.
1048
00:56:13,604 --> 00:56:16,004
Material was thrown
into the atmosphere,
1049
00:56:16,006 --> 00:56:18,507
plunging the planet
into a nuclear winter.
1050
00:56:18,509 --> 00:56:24,780
It was complete chaos, and it
went dark for two full years.
1051
00:56:24,782 --> 00:56:27,816
Narrator: Without sunlight,
temperatures dropped.
1052
00:56:29,587 --> 00:56:34,957
Just months after the impact,
the planet cooled by 20 degrees.
1053
00:56:35,726 --> 00:56:38,560
In the immediate area, there's
just tremendous destruction.
1054
00:56:38,562 --> 00:56:40,462
Just everything gets destroyed.
1055
00:56:40,464 --> 00:56:43,031
But over the long term,
you're talking about ash
1056
00:56:43,033 --> 00:56:46,602
kicked up in the atmosphere,
extremely cold weather,
1057
00:56:46,604 --> 00:56:48,871
basically a global ice age.
1058
00:56:50,040 --> 00:56:52,174
Narrator: The freezing
temperatures killed off
1059
00:56:52,176 --> 00:56:54,143
most plant life.
1060
00:56:54,145 --> 00:56:56,678
Oluseyi: Imagine how that
affected life on earth.
1061
00:56:56,680 --> 00:57:00,682
No plants and the base
of the ecosystem collapses.
1062
00:57:04,388 --> 00:57:07,923
Narrator: This dark nuclear
winter lasted two years
1063
00:57:07,925 --> 00:57:12,027
and prevented plants
from photosynthesizing.
1064
00:57:12,029 --> 00:57:14,630
So if plants can no longer
use photosynthesis
1065
00:57:14,632 --> 00:57:16,632
to live, they'll die.
1066
00:57:16,634 --> 00:57:19,368
And then with no plants,
then you have no food
1067
00:57:19,370 --> 00:57:21,036
for these larger animals.
1068
00:57:21,038 --> 00:57:23,972
And so anything that eats
those animals will also die.
1069
00:57:23,974 --> 00:57:25,207
If you lose your plants,
1070
00:57:25,209 --> 00:57:28,410
you're going to lose
your large scale life.
1071
00:57:28,412 --> 00:57:31,547
Narrator: First the plant eating
herbivores died off,
1072
00:57:31,549 --> 00:57:35,384
followed by the meat eating
carnivores.
1073
00:57:35,386 --> 00:57:39,021
Most of the dinosaurs
were just unable to find food
1074
00:57:39,023 --> 00:57:42,024
and to survive through
the cold long night.
1075
00:57:43,794 --> 00:57:46,829
Narrator: The global devastation
wasn't over yet.
1076
00:57:46,831 --> 00:57:50,199
The rock of the continental
shelf where the asteroid hit
1077
00:57:50,201 --> 00:57:52,801
contained carbon and sulfur.
1078
00:57:54,405 --> 00:57:58,006
Lanza: These carbonate rocks
were heated and vaporized
1079
00:57:58,008 --> 00:58:00,876
and released carbon dioxide
into the atmosphere.
1080
00:58:00,878 --> 00:58:02,978
Yet another greenhouse gas.
1081
00:58:02,980 --> 00:58:05,981
So you're vaporizing
a lot of sulfur,
1082
00:58:05,983 --> 00:58:08,817
a lot of salts
of different kinds
1083
00:58:08,819 --> 00:58:12,554
that are then lofted up
into the upper atmosphere,
1084
00:58:12,556 --> 00:58:15,324
that then plays havoc
on the climate.
1085
00:58:19,463 --> 00:58:23,265
Narrator: These greenhouse gases
built up in the atmosphere
1086
00:58:23,267 --> 00:58:25,667
forming a warming blanket.
1087
00:58:28,672 --> 00:58:31,740
Triggering the next phase
of destruction.
1088
00:58:34,578 --> 00:58:37,279
Global warming on steroids.
1089
00:58:39,583 --> 00:58:44,253
Temperatures rose 10 degrees
above normal.
1090
00:58:44,255 --> 00:58:48,357
Then the oceans warmed,
as well.
1091
00:58:48,359 --> 00:58:51,894
Oxygen levels dropped,
and the seas became toxic
1092
00:58:51,896 --> 00:58:55,297
to simple life forms.
1093
00:58:55,299 --> 00:58:58,300
It actually made it impossible
for certain microbes
1094
00:58:58,302 --> 00:59:01,803
to actually live, and they're
the basis of the food system.
1095
00:59:01,805 --> 00:59:05,807
So really it changed what could
actually live in the ocean
1096
00:59:05,809 --> 00:59:09,444
and how much could live there.
1097
00:59:09,446 --> 00:59:11,680
Narrator: Dead zones appeared
in the oceans
1098
00:59:11,682 --> 00:59:14,583
just as they had on land.
1099
00:59:14,585 --> 00:59:20,455
Nearly three quarters
of all life on earth died,
1100
00:59:20,457 --> 00:59:23,659
all from one asteroid impact.
1101
00:59:27,765 --> 00:59:29,765
To prevent it
from happening again,
1102
00:59:29,767 --> 00:59:33,635
we need to track all
potentially dangerous asteroids.
1103
00:59:35,806 --> 00:59:37,105
But that isn't easy
1104
00:59:37,107 --> 00:59:40,676
because these space rocks
can change direction.
1105
00:59:54,391 --> 00:59:57,192
♪
1106
00:59:57,194 --> 00:59:59,761
narrator: Saricicek, turkey.
1107
00:59:59,763 --> 01:00:02,998
Security cameras record
a flash in the sky.
1108
01:00:04,902 --> 01:00:10,138
The flash -- a 3-foot asteroid
exploding in the atmosphere.
1109
01:00:10,140 --> 01:00:16,078
♪
1110
01:00:16,080 --> 01:00:18,880
lanza: It blew up in
the atmosphere and rained down,
1111
01:00:18,882 --> 01:00:20,148
and people saw that.
1112
01:00:20,150 --> 01:00:21,650
It was very noticeable.
1113
01:00:21,652 --> 01:00:24,219
And they went, and they
collected those meteorites.
1114
01:00:24,221 --> 01:00:27,990
And then they tried to figure
out what they were looking at.
1115
01:00:30,494 --> 01:00:34,129
Narrator: The debris was sent
for fragment analysis.
1116
01:00:35,432 --> 01:00:38,300
I have a piece of one here.
So first, on the outside,
1117
01:00:38,302 --> 01:00:40,702
you can see it has
a really black fusion crust.
1118
01:00:40,704 --> 01:00:42,604
This is from when it fell
into the earth's atmosphere,
1119
01:00:42,606 --> 01:00:44,039
so it was melted.
1120
01:00:44,041 --> 01:00:46,375
But when you look on
the inside, it reveals
1121
01:00:46,377 --> 01:00:50,612
this beautiful, very light tone,
fine grained material.
1122
01:00:50,614 --> 01:00:53,515
And so these meteorites
are incredibly distinctive
1123
01:00:53,517 --> 01:00:55,417
and really beautiful.
1124
01:00:55,419 --> 01:00:57,352
Narrator:
The meteorites are rocky.
1125
01:00:57,354 --> 01:01:01,657
They're beautiful color comes
from a mineral called howardite.
1126
01:01:01,659 --> 01:01:06,528
It's rare, and it doesn't
form on earth.
1127
01:01:06,530 --> 01:01:09,931
Howardite meteorites come from
the asteroid vesta,
1128
01:01:09,933 --> 01:01:12,701
and we know that because
of the dawn mission
1129
01:01:12,703 --> 01:01:14,836
that actually went to vesta
and took a look at it
1130
01:01:14,838 --> 01:01:17,906
very carefully, so we know
the composition very well.
1131
01:01:17,908 --> 01:01:20,676
And so now suddenly here
was a new kind of meteorite
1132
01:01:20,678 --> 01:01:26,114
that's in turkey that matches
the vesta family of meteorites
1133
01:01:26,950 --> 01:01:30,118
narrator: But how can we be sure
that these bits of space rock
1134
01:01:30,120 --> 01:01:35,724
came from vesta, an asteroid
over 100 million miles away.
1135
01:01:35,726 --> 01:01:38,427
It was a fall meteorite,
and so what that means
1136
01:01:38,429 --> 01:01:41,296
is that someone saw it,
you know, we saw it fall.
1137
01:01:41,298 --> 01:01:43,265
And so we knew its trajectory.
1138
01:01:43,267 --> 01:01:46,034
So we could actually
work backwards to say,
1139
01:01:46,036 --> 01:01:48,837
where did that meteorite
come from?
1140
01:01:48,839 --> 01:01:50,806
Narrator: Retracing
the trajectory of
1141
01:01:50,808 --> 01:01:54,943
the turkish meteorites took
the scientists all the way back
1142
01:01:54,945 --> 01:01:57,946
to the 328-mile wide vesta.
1143
01:02:02,086 --> 01:02:04,086
Where they studied
vesta's surface,
1144
01:02:04,088 --> 01:02:06,621
they found further evidence.
1145
01:02:06,623 --> 01:02:09,725
On the surface of vesta,
there's actually a very large
1146
01:02:09,727 --> 01:02:13,295
and fresh impact crater
that is around the same age
1147
01:02:13,297 --> 01:02:14,963
of the turkish meteorite.
1148
01:02:14,965 --> 01:02:17,099
So that really clinched it.
1149
01:02:17,101 --> 01:02:20,802
This thing is definitely
from vesta, and we proved it.
1150
01:02:20,804 --> 01:02:25,006
Narrator: So how did bits of
vesta end up here on earth?
1151
01:02:25,008 --> 01:02:29,044
22 million years ago,
some very large impactor
1152
01:02:29,046 --> 01:02:32,013
struck vesta,
made a huge crater,
1153
01:02:32,015 --> 01:02:34,883
and some of the rocks
from that crater actually
1154
01:02:34,885 --> 01:02:40,589
escaped from vesta's gravity
and were lofted into space.
1155
01:02:40,591 --> 01:02:43,325
Narrator: Some of these rocks
from vesta went into orbits
1156
01:02:43,327 --> 01:02:45,894
that intersected with earth.
1157
01:02:46,430 --> 01:02:51,133
22 million years later,
one blew up over saricicek.
1158
01:02:54,204 --> 01:02:57,372
This saricicek meteor shows
that the asteroid belt
1159
01:02:57,374 --> 01:02:59,174
is an unstable environment.
1160
01:03:01,945 --> 01:03:05,347
Asteroids frequently strike
other asteroids.
1161
01:03:08,051 --> 01:03:09,451
Lanza: That's actually
happening all the time.
1162
01:03:09,453 --> 01:03:10,986
Things are running
into each other
1163
01:03:10,988 --> 01:03:13,121
in our solar system right now.
1164
01:03:13,123 --> 01:03:14,890
And so that makes it
really hard for us
1165
01:03:14,892 --> 01:03:18,026
to track all of those objects
because we don't actually know
1166
01:03:18,028 --> 01:03:20,228
what happens after they collide
with each other.
1167
01:03:20,230 --> 01:03:21,897
Now things are
totally different.
1168
01:03:21,899 --> 01:03:24,566
And that changes
the whole system.
1169
01:03:24,568 --> 01:03:29,137
Narrator: Each collision
makes more asteroids.
1170
01:03:29,139 --> 01:03:30,806
Oluseyi: There's many
different possibilities
1171
01:03:30,808 --> 01:03:33,308
of what could happen
when asteroids collide.
1172
01:03:33,310 --> 01:03:36,211
Imagine a roller derby
situation.
1173
01:03:38,649 --> 01:03:40,682
If you have two
groups of players
1174
01:03:40,684 --> 01:03:42,050
that run into each other,
1175
01:03:42,052 --> 01:03:45,253
that could be like two asteroids
running into each other.
1176
01:03:45,255 --> 01:03:49,257
And one possible outcome
is that one stays intact
1177
01:03:49,259 --> 01:03:51,693
while the other
is completely blown apart.
1178
01:03:54,698 --> 01:03:58,099
That sends fragments flying all
through the main asteroid belt,
1179
01:03:58,101 --> 01:04:00,068
and then there's
a little asteroid fragments
1180
01:04:00,070 --> 01:04:03,138
are on their own independent
orbits around the sun.
1181
01:04:04,374 --> 01:04:06,675
A problem with
asteroid impacts is that
1182
01:04:06,677 --> 01:04:08,677
we're always making
new asteroids.
1183
01:04:08,679 --> 01:04:10,445
There are big asteroids
out there,
1184
01:04:10,447 --> 01:04:11,947
and they get hit
by other asteroids,
1185
01:04:11,949 --> 01:04:13,415
and then you get shrapnel.
1186
01:04:13,417 --> 01:04:16,117
And now you've got not one
big one and one smaller one,
1187
01:04:16,119 --> 01:04:17,853
you've got one big one,
one smaller one,
1188
01:04:17,855 --> 01:04:19,621
and millions of little ones.
1189
01:04:19,623 --> 01:04:22,591
Now, most of these aren't very
big, but some of them might be
1190
01:04:22,593 --> 01:04:25,160
bigger and could be
potentially hazardous.
1191
01:04:26,563 --> 01:04:28,463
Narrator:
As the solar system ages,
1192
01:04:28,465 --> 01:04:31,166
the number of
asteroids increases.
1193
01:04:31,168 --> 01:04:34,369
Each new space rock
travels on a new course
1194
01:04:34,371 --> 01:04:38,006
which could intersect
with earth.
1195
01:04:38,008 --> 01:04:40,575
So we're constantly producing
new asteroids
1196
01:04:40,577 --> 01:04:42,944
and big collisions
in the main asteroid belt.
1197
01:04:42,946 --> 01:04:44,746
And these are producing
the small asteroids
1198
01:04:44,748 --> 01:04:49,050
that will eventually drift
inward in the solar system.
1199
01:04:49,052 --> 01:04:51,686
Narrator: Tracking this
constantly evolving population
1200
01:04:51,688 --> 01:04:55,924
of asteroids gives scientists
a huge headache.
1201
01:04:55,926 --> 01:04:58,126
If they break apart,
then that gives you
1202
01:04:58,128 --> 01:05:00,629
even more pieces
of the asteroid to track.
1203
01:05:00,631 --> 01:05:04,032
It's not a simple thing
to track and predict
1204
01:05:04,034 --> 01:05:07,502
the orbits of asteroids
and their movements,
1205
01:05:07,504 --> 01:05:11,673
because one tiny little change
1206
01:05:11,675 --> 01:05:17,746
can have huge dramatic impacts
for its possible future.
1207
01:05:17,748 --> 01:05:19,714
Bullock: Figuring out exactly
where they're going to go
1208
01:05:19,716 --> 01:05:22,050
and keeping track of how
they interact with each other,
1209
01:05:22,052 --> 01:05:24,386
this is a huge endeavor.
1210
01:05:24,388 --> 01:05:27,122
Narrator: The sheer volume
of asteroids can affect
1211
01:05:27,124 --> 01:05:29,157
the behavior of other asteroids
1212
01:05:29,159 --> 01:05:32,627
as they gravitationally
interact.
1213
01:05:32,629 --> 01:05:36,464
Think about your roller derby
player skating in circles.
1214
01:05:36,466 --> 01:05:38,266
The path they're going
to follow would evolve
1215
01:05:38,268 --> 01:05:41,136
the more people you plop down
on the track
1216
01:05:41,138 --> 01:05:42,604
they start interacting
with each other,
1217
01:05:42,606 --> 01:05:44,839
and their trajectory
will change.
1218
01:05:46,109 --> 01:05:48,410
The more crowded you make
the solar system,
1219
01:05:48,412 --> 01:05:50,845
the more things are
to change your orbit
1220
01:05:50,847 --> 01:05:53,848
of your individual asteroid.
1221
01:05:55,052 --> 01:05:56,851
It's not like
air traffic control,
1222
01:05:56,853 --> 01:05:58,920
where there's a known
amount of airplanes
1223
01:05:58,922 --> 01:06:00,755
and they all follow a plan.
1224
01:06:02,225 --> 01:06:04,859
Narrator: This situation is
further complicated because
1225
01:06:04,861 --> 01:06:09,898
asteroid orbits can be affected
by other more subtle forces.
1226
01:06:10,834 --> 01:06:14,636
One of these is called the
yarkovsky or the yorp effect.
1227
01:06:14,638 --> 01:06:17,272
Honestly yorp
is more fun to say.
1228
01:06:17,274 --> 01:06:19,941
Narrator: The yorp effect is
caused by sunlight
1229
01:06:19,943 --> 01:06:22,110
hitting an asteroid.
1230
01:06:22,112 --> 01:06:24,646
Light is made up of photons
that are traveling,
1231
01:06:24,648 --> 01:06:27,115
and these photons
actually have momentum.
1232
01:06:27,117 --> 01:06:29,084
So when light shines
on something,
1233
01:06:29,086 --> 01:06:31,086
it actually pushes on it.
1234
01:06:33,023 --> 01:06:34,990
Narrator: When sunlight
hits an asteroid,
1235
01:06:34,992 --> 01:06:38,259
the photons give it
a tiny push...
1236
01:06:39,396 --> 01:06:43,031
...Enough to change
the space rock's trajectory.
1237
01:06:43,033 --> 01:06:48,670
♪
1238
01:06:48,672 --> 01:06:51,539
when we know an asteroid
is really heading our way,
1239
01:06:51,541 --> 01:06:54,075
it's time to fight back.
1240
01:06:54,077 --> 01:06:56,011
So we've got an asteroid
that's headed at us.
1241
01:06:56,013 --> 01:06:57,112
What do we do?
1242
01:06:57,114 --> 01:06:59,147
Two main possibilities --
we deflect it,
1243
01:06:59,149 --> 01:07:01,116
we nudge it a little bit
so it misses,
1244
01:07:01,118 --> 01:07:03,418
or we blow it up,
we destroy it.
1245
01:07:03,420 --> 01:07:05,487
Which of those
do you want to do?
1246
01:07:05,489 --> 01:07:11,059
♪
1247
01:07:11,061 --> 01:07:13,628
narrator: It's a tough choice.
1248
01:07:13,630 --> 01:07:18,166
Get it wrong, and we could
end up being hit by a swarm
1249
01:07:18,168 --> 01:07:20,802
of radioactive space rocks.
1250
01:07:20,804 --> 01:07:28,009
♪
1251
01:07:38,021 --> 01:07:41,756
♪
1252
01:07:41,758 --> 01:07:44,559
narrator:
An asteroid is heading our way,
1253
01:07:44,561 --> 01:07:47,295
and it may hit us in 2068.
1254
01:07:48,165 --> 01:07:50,732
How do we prevent
such a catastrophe
1255
01:07:50,734 --> 01:07:54,569
and stop it
from ever getting close?
1256
01:07:54,571 --> 01:07:56,337
Well, you just don't want
to take get anywhere near us
1257
01:07:56,339 --> 01:07:57,605
in the first place.
1258
01:07:57,607 --> 01:07:58,706
So what do you do?
1259
01:07:58,708 --> 01:08:01,309
Well, you can destroy them,
1260
01:08:01,311 --> 01:08:04,512
or you can push them
out of the way.
1261
01:08:04,514 --> 01:08:06,748
This is something where our
science fiction ideas
1262
01:08:06,750 --> 01:08:08,716
have got it almost
entirely wrong.
1263
01:08:08,718 --> 01:08:13,354
If you're in a bad movie,
a really, really bad movie,
1264
01:08:13,356 --> 01:08:16,024
you can send astronauts
to an asteroid,
1265
01:08:16,026 --> 01:08:17,559
put a nuclear bomb in it,
1266
01:08:17,561 --> 01:08:19,427
and blow it up
into lots of little bits
1267
01:08:19,429 --> 01:08:21,896
that then burn up harmlessly
in our atmosphere.
1268
01:08:21,898 --> 01:08:24,666
Yeah, it doesn't work that way.
1269
01:08:24,668 --> 01:08:26,134
Narrator:
Blowing up an asteroid
1270
01:08:26,136 --> 01:08:28,503
would make the problem
much worse.
1271
01:08:28,505 --> 01:08:31,906
We are no longer dealing with
just one space rock.
1272
01:08:31,908 --> 01:08:34,375
My issue with this is that
you may have turned
1273
01:08:34,377 --> 01:08:36,344
one problem into 50.
1274
01:08:36,346 --> 01:08:38,546
Instead of one
regular sized asteroid,
1275
01:08:38,548 --> 01:08:40,615
now you have a whole bunch
of littler ones,
1276
01:08:40,617 --> 01:08:42,784
and these may still hit
the earth and cause damage.
1277
01:08:42,786 --> 01:08:45,520
And you know what?
That's not much less fun
1278
01:08:45,522 --> 01:08:47,789
than just having
a single big asteroid.
1279
01:08:47,791 --> 01:08:49,424
Now you've just taken
all that devastation
1280
01:08:49,426 --> 01:08:52,494
and spread it out
for everybody to enjoy.
1281
01:08:52,496 --> 01:08:55,330
Stricker: The problem with using
a nuclear device is that
1282
01:08:55,332 --> 01:08:59,200
the products that rain down
on earth are now radioactive.
1283
01:08:59,202 --> 01:09:07,709
♪
1284
01:09:07,711 --> 01:09:10,845
narrator: If a dangerous
asteroid was on its way,
1285
01:09:10,847 --> 01:09:13,581
blowing it up
would be a last resort.
1286
01:09:14,751 --> 01:09:17,452
A less risky method
is to deflect it off
1287
01:09:17,454 --> 01:09:19,621
its collision course.
1288
01:09:19,623 --> 01:09:21,823
A small nudge early enough
1289
01:09:21,825 --> 01:09:25,493
can change in asteroid's
trajectory away from earth.
1290
01:09:26,863 --> 01:09:30,265
You don't have to nudge it
very much for it to miss, right?
1291
01:09:30,267 --> 01:09:32,000
So if it's headed
straight at it,
1292
01:09:32,002 --> 01:09:33,301
I just touch it slightly,
1293
01:09:33,303 --> 01:09:36,204
by the time it gets to earth,
its way off course.
1294
01:09:38,141 --> 01:09:40,742
Narrator: Nasa is investigating
ways to change
1295
01:09:40,744 --> 01:09:46,748
an asteroid's path,
including using a nuclear burst.
1296
01:09:46,750 --> 01:09:51,886
In a nuclear burst, what we do
is we don't actually hit it.
1297
01:09:51,888 --> 01:09:56,257
We come up to it with the device
on a spacecraft,
1298
01:09:56,259 --> 01:09:58,993
and then the device would be
detonated at a certain height
1299
01:09:58,995 --> 01:10:01,329
above the surface.
1300
01:10:01,331 --> 01:10:03,298
Plait: That heats up
the surface of the asteroid,
1301
01:10:03,300 --> 01:10:04,799
which vaporizes.
1302
01:10:04,801 --> 01:10:07,502
You get vaporized rock or metal
which blasts off the surface,
1303
01:10:07,504 --> 01:10:09,437
and that's how a rocket works.
1304
01:10:09,439 --> 01:10:11,906
So you blow up a bomb here,
and it winds up
1305
01:10:11,908 --> 01:10:15,610
pushing the asteroid
in the other direction
1306
01:10:15,612 --> 01:10:18,313
narrator: To prevent
any potential nuclear fallout,
1307
01:10:18,315 --> 01:10:21,749
nasa would detonate the bomb
a long way from earth
1308
01:10:23,186 --> 01:10:26,754
plesko: Any deflection attempt
has to be done years in advance,
1309
01:10:26,756 --> 01:10:28,356
which means it would be done
on the other side
1310
01:10:28,358 --> 01:10:30,291
of the solar system from us
1311
01:10:30,293 --> 01:10:33,061
on the opposite side
of the object's orbit.
1312
01:10:33,063 --> 01:10:35,697
That means that all of
the vapor made during
1313
01:10:35,699 --> 01:10:38,299
the explosion gets blown away
by the solar wind.
1314
01:10:39,869 --> 01:10:43,605
Narrator: Nasa is investigating
other less explosive methods
1315
01:10:43,607 --> 01:10:45,807
of deflecting an asteroid.
1316
01:10:45,809 --> 01:10:49,777
De-star would blast the asteroid
with a laser.
1317
01:10:49,779 --> 01:10:52,747
Oluseyi: We hit it with
the laser, material vaporizes
1318
01:10:52,749 --> 01:10:54,882
and flies off the asteroid,
1319
01:10:54,884 --> 01:10:56,784
and because
of newton's third law,
1320
01:10:56,786 --> 01:10:58,753
which is that for every action
there is an opposite
1321
01:10:58,755 --> 01:11:02,423
an equal reaction, this means
that vaporize material
1322
01:11:02,425 --> 01:11:04,926
moving off in one direction
moves the asteroid
1323
01:11:04,928 --> 01:11:07,228
in the opposite direction.
1324
01:11:08,665 --> 01:11:10,732
Narrator: Both the laser
and the nuclear burst
1325
01:11:10,734 --> 01:11:13,568
are still just ideas
on the drawing board.
1326
01:11:16,306 --> 01:11:19,340
But one asteroid
deflection mission called
1327
01:11:19,342 --> 01:11:23,544
double asteroid redirection
test, or dart for short,
1328
01:11:23,546 --> 01:11:28,049
is already up and running and
scheduled for launch in 2021.
1329
01:11:29,619 --> 01:11:31,586
Dart is a kinetic impactor
1330
01:11:31,588 --> 01:11:35,089
and will try to knock
an asteroid off course.
1331
01:11:36,593 --> 01:11:38,826
Thaller: At nasa for the longest
time, all we've been able to do
1332
01:11:38,828 --> 01:11:41,262
is theorize about how
we change their path.
1333
01:11:41,264 --> 01:11:42,363
But now for the first time,
1334
01:11:42,365 --> 01:11:44,866
we're actually gonna
practice in.
1335
01:11:44,868 --> 01:11:47,035
Narrator: Leading this
groundbreaking mission to bump
1336
01:11:47,037 --> 01:11:51,572
an asteroid off its orbit
is dr. Andy chang.
1337
01:11:51,574 --> 01:11:54,876
Chang: Dart is the first
planetary defense mission
1338
01:11:54,878 --> 01:11:57,478
that we've ever done,
where we take a spacecraft,
1339
01:11:57,480 --> 01:12:01,649
we fly the spacecraft into
the asteroid to change
1340
01:12:01,651 --> 01:12:04,585
its course and make it
miss the earth.
1341
01:12:04,587 --> 01:12:07,955
Narrator: Dart's target
is a 525 foot space rock
1342
01:12:07,957 --> 01:12:12,894
orbiting the large
near earth asteroid didymos.
1343
01:12:12,896 --> 01:12:15,129
We pick the near earth asteroid
didymos as a target
1344
01:12:15,131 --> 01:12:16,998
for the dart mission because
although it's
1345
01:12:17,000 --> 01:12:19,334
a near earth asteroid,
it's one that's very safely
1346
01:12:19,336 --> 01:12:20,868
parked away out there in space.
1347
01:12:20,870 --> 01:12:23,104
There's no way we can move
didymos or its moon
1348
01:12:23,106 --> 01:12:25,740
in any way big enough to cause
a problem for the earth.
1349
01:12:27,677 --> 01:12:29,877
Narrator: The diddy-moon
asteroid weighs
1350
01:12:29,879 --> 01:12:33,381
around 10 1/2 billion pounds.
1351
01:12:33,383 --> 01:12:36,551
So how do you knock such
a large lump of rock
1352
01:12:36,553 --> 01:12:38,853
off its path?
1353
01:12:50,266 --> 01:12:53,301
♪
1354
01:12:53,303 --> 01:12:54,736
narrator:
We're sending a spacecraft
1355
01:12:54,738 --> 01:12:58,206
to knock the diddy-moon
asteroid off course.
1356
01:12:59,342 --> 01:13:02,944
The asteroid is moving at
over 36,000 miles an hour
1357
01:13:02,946 --> 01:13:06,681
and is around
seven million miles away.
1358
01:13:06,683 --> 01:13:10,151
So how do you move
a 10 and a half billion pound
1359
01:13:10,153 --> 01:13:12,687
space rock?
1360
01:13:12,689 --> 01:13:15,790
You need to hit it really hard
to change its orbit,
1361
01:13:15,792 --> 01:13:19,861
so it's going to be coming in
at a super high velocity
1362
01:13:19,863 --> 01:13:23,164
in order to impart a bunch
of energy momentum to that moon.
1363
01:13:25,001 --> 01:13:26,868
Narrator:
Dart will hit the target
1364
01:13:26,870 --> 01:13:29,570
at around 14,000 miles an hour.
1365
01:13:29,572 --> 01:13:33,674
The speed of the dart impact
will be more than nine times
1366
01:13:33,676 --> 01:13:37,078
the speed of the rifle bullet
from an ak-47.
1367
01:13:39,015 --> 01:13:42,550
Narrator: The impact will give
the asteroid a small push.
1368
01:13:42,552 --> 01:13:44,852
To work out how big a push,
1369
01:13:44,854 --> 01:13:49,323
we test impacts
with the ames vertical gun.
1370
01:13:49,325 --> 01:13:51,759
Durda: At the nasa ames
research center in california,
1371
01:13:51,761 --> 01:13:53,394
there's a very special
facility called
1372
01:13:53,396 --> 01:13:55,496
the ames vertical gun range.
1373
01:13:55,498 --> 01:13:57,732
It's a hyper velocity gas gun
that allows us
1374
01:13:57,734 --> 01:14:01,869
to shoot little metal bbs
at rock targets at speeds
1375
01:14:01,871 --> 01:14:05,940
up to like 13,000, 14,000
miles per hour.
1376
01:14:05,942 --> 01:14:07,875
Narrator: The gun replicates
the impact
1377
01:14:07,877 --> 01:14:09,977
the dart mission will make.
1378
01:14:09,979 --> 01:14:12,513
It reveals that an impact
will blow off
1379
01:14:12,515 --> 01:14:16,484
a small amount of debris
but at extremely high speed,
1380
01:14:16,486 --> 01:14:20,354
enough to give the asteroid
an additional kick.
1381
01:14:20,356 --> 01:14:22,957
The impact will blow off pieces
of the asteroid,
1382
01:14:22,959 --> 01:14:25,293
so the pieces
are thrown off the back.
1383
01:14:25,295 --> 01:14:28,963
And so that that process acts
like a little rocket engine.
1384
01:14:28,965 --> 01:14:31,966
That provides an additional
momentum change,
1385
01:14:31,968 --> 01:14:34,836
momentum push
to the target itself.
1386
01:14:34,838 --> 01:14:37,205
Narrator: The combined push
from the kinetic impactor
1387
01:14:37,207 --> 01:14:40,274
and the ejected debris is tiny,
1388
01:14:40,276 --> 01:14:43,444
around 0.0009 of
a mile per hour.
1389
01:14:43,446 --> 01:14:46,981
But hopefully it's enough
to change the asteroid's orbit.
1390
01:14:46,983 --> 01:14:50,418
If dart works, we could
then use a similar mission
1391
01:14:50,420 --> 01:14:53,287
to defend earth
when the time comes.
1392
01:14:54,257 --> 01:14:56,757
This isn't some
small rock prototype
1393
01:14:56,759 --> 01:14:58,259
that we're doing this test on.
1394
01:14:58,261 --> 01:15:01,496
This is a real dress rehearsal
for an asteroid
1395
01:15:01,498 --> 01:15:03,564
that could destroy cities
1396
01:15:03,566 --> 01:15:06,901
or even maybe send
the earth in chaos.
1397
01:15:06,903 --> 01:15:10,271
Narrator: The moon of didymos
is a solid lump of rock.
1398
01:15:10,273 --> 01:15:13,040
Will a kinetic impactor
like dart work
1399
01:15:13,042 --> 01:15:16,143
with a rubble pile asteroid
like apophis?
1400
01:15:16,145 --> 01:15:18,145
When you shoot a rubble pile
with a projectile,
1401
01:15:18,147 --> 01:15:20,047
it's a little bit more
like trying to punch a sandbag.
1402
01:15:20,049 --> 01:15:22,750
You get a lot more a lot more
the energy is absorbed
1403
01:15:22,752 --> 01:15:25,620
into just moving the sand
around inside the bag
1404
01:15:25,622 --> 01:15:27,755
than ejecting it,
and so rubble piles
1405
01:15:27,757 --> 01:15:30,892
might be a little harder
to move by this method.
1406
01:15:31,895 --> 01:15:34,896
Narrator: We don't know if we
can deflect a rubble pile
1407
01:15:34,898 --> 01:15:36,998
asteroid like apophis.
1408
01:15:37,000 --> 01:15:40,101
They remain a clear
and present danger.
1409
01:15:40,970 --> 01:15:43,938
And something
we might not survive.
1410
01:15:47,310 --> 01:15:50,845
But there may be
a space lifeboat.
1411
01:15:55,718 --> 01:16:00,855
In 2018, scientists reexamined
rocks collected by apollo 14
1412
01:16:00,857 --> 01:16:02,990
astronauts from the moon.
1413
01:16:02,992 --> 01:16:09,363
♪
1414
01:16:09,365 --> 01:16:14,168
buried in the samples was a rock
that shouldn't be there.
1415
01:16:15,471 --> 01:16:18,272
They got something
they didn't expect,
1416
01:16:18,274 --> 01:16:20,641
and that was an earth rock.
1417
01:16:20,643 --> 01:16:24,679
They actually picked up
a rock from earth on the moon.
1418
01:16:24,681 --> 01:16:26,347
They didn't bring it with them.
1419
01:16:26,349 --> 01:16:29,383
It's very likely that it was
something that was lofted up
1420
01:16:29,385 --> 01:16:34,121
when something hit earth,
throw up a bunch of rocks.
1421
01:16:34,123 --> 01:16:36,324
Some of those rocks
fell on to the moon,
1422
01:16:36,326 --> 01:16:39,327
and that's a meteorite
on the moon,
1423
01:16:39,329 --> 01:16:41,562
but it's from earth.
1424
01:16:45,568 --> 01:16:47,435
Narrator: Super computer
simulations of
1425
01:16:47,437 --> 01:16:52,206
the kpg asteroid strike revealed
how the impact had so much
1426
01:16:52,208 --> 01:16:56,510
energy that it catapulted rocks
out of earth's atmosphere
1427
01:16:56,512 --> 01:16:58,412
and into space.
1428
01:16:58,414 --> 01:17:00,581
They were then caught
by the moon's gravity
1429
01:17:00,583 --> 01:17:03,718
and pulled down
to the lunar surface.
1430
01:17:03,720 --> 01:17:09,557
We now know the material ejected
into space from asteroid impacts
1431
01:17:09,559 --> 01:17:12,093
can travel to other planets,
as well,
1432
01:17:12,095 --> 01:17:15,796
which would explain
the 100 mars meteorites
1433
01:17:15,798 --> 01:17:17,431
we've found here on earth.
1434
01:17:20,069 --> 01:17:22,637
We think that there was probably
the exchange of a huge amount
1435
01:17:22,639 --> 01:17:24,705
of material
between different bodies,
1436
01:17:24,707 --> 01:17:27,508
earth to the moon
and back again and to mars.
1437
01:17:30,647 --> 01:17:33,147
With each impact that occurs
in our solar system
1438
01:17:33,149 --> 01:17:36,751
that ejects all types of
material that allows material
1439
01:17:36,753 --> 01:17:40,354
to swap from planet to planet,
moon to planet, moon to moon.
1440
01:17:40,356 --> 01:17:41,856
And so there's all
of this material
1441
01:17:41,858 --> 01:17:44,959
that eventually travels
from place to place.
1442
01:17:44,961 --> 01:17:48,062
Narrator: Should another giant
asteroid hit our planet,
1443
01:17:48,064 --> 01:17:52,833
this planetary interchange
may give life on earth
1444
01:17:52,835 --> 01:17:54,802
a lifeline.
1445
01:17:54,804 --> 01:17:57,471
Lanza: If you think about
such an impact today,
1446
01:17:57,473 --> 01:18:00,675
you know, the chances are high
that a lot of life would be
1447
01:18:00,677 --> 01:18:05,079
wiped out, much of life,
probably all of human life.
1448
01:18:05,081 --> 01:18:08,249
It's certainly possible that
a big enough asteroid strike
1449
01:18:08,251 --> 01:18:10,251
could completely sterilize
the planet.
1450
01:18:10,253 --> 01:18:13,187
Talking about
no life whatsoever.
1451
01:18:13,189 --> 01:18:14,922
Not to put too fine
a point on it,
1452
01:18:14,924 --> 01:18:16,991
but if there's a dinosaur killer
asteroid out there
1453
01:18:16,993 --> 01:18:19,460
and it hits the earth,
the chance of humanity's
1454
01:18:19,462 --> 01:18:23,531
survival of such a thing
as a species, mm, not great.
1455
01:18:27,270 --> 01:18:29,503
Narrator:
Humans may not survive.
1456
01:18:29,505 --> 01:18:35,109
But some scientists believe
that simple life forms could.
1457
01:18:35,111 --> 01:18:39,346
♪
1458
01:18:50,193 --> 01:18:55,696
♪
1459
01:18:55,698 --> 01:18:58,566
narrator: Asteroids have hit
our planet many times
1460
01:18:58,568 --> 01:19:00,134
in the past.
1461
01:19:01,637 --> 01:19:06,540
One giant strike wiped out
70% of all life on earth.
1462
01:19:07,477 --> 01:19:12,113
If another huge asteroid
hits us, can life survive?
1463
01:19:12,115 --> 01:19:17,017
♪
1464
01:19:17,019 --> 01:19:20,287
sutter: If a giant rock hits
the earth and kills almost
1465
01:19:20,289 --> 01:19:25,960
all life on earth,
there is a slim line of hope.
1466
01:19:25,962 --> 01:19:29,864
And that's because the dirt,
the rocks on earth
1467
01:19:29,866 --> 01:19:35,369
are infused with bacterial life,
with microscopic life.
1468
01:19:35,371 --> 01:19:37,905
And in the event
of a giant impact,
1469
01:19:37,907 --> 01:19:42,009
some of these bits of rock
will be ejected into space
1470
01:19:42,011 --> 01:19:43,477
and might float around.
1471
01:19:43,479 --> 01:19:46,347
After an asteroid impact,
whatever ejected
1472
01:19:46,349 --> 01:19:49,216
into the atmosphere
could contain microbial life
1473
01:19:49,218 --> 01:19:51,852
that when it falls back down
on to the ground
1474
01:19:51,854 --> 01:19:54,488
could re-seed the life
on that planet.
1475
01:19:54,490 --> 01:19:59,426
♪
1476
01:19:59,428 --> 01:20:02,229
narrator: Some bacteria can
survive the harsh conditions
1477
01:20:02,231 --> 01:20:06,934
of space and can cope with
an asteroid strike, reentry,
1478
01:20:06,936 --> 01:20:10,037
and landing back
on earth's surface.
1479
01:20:10,039 --> 01:20:19,246
♪
1480
01:20:19,248 --> 01:20:22,616
I think in terms of life
on planet earth,
1481
01:20:22,618 --> 01:20:25,319
I think we've learned that we
live on a very resilient planet.
1482
01:20:25,321 --> 01:20:28,222
And I think life in some form,
even if it has to crawl
1483
01:20:28,224 --> 01:20:31,091
its way back
from bacterial stage,
1484
01:20:31,093 --> 01:20:34,862
I think life on this planet is
going to going to eke through.
1485
01:20:36,232 --> 01:20:40,634
Plait: Life is pretty good at
figuring out a way of surviving.
1486
01:20:40,636 --> 01:20:43,070
We know that life
first formed on the earth
1487
01:20:43,072 --> 01:20:45,239
well over 4 billion years ago
1488
01:20:45,241 --> 01:20:48,275
and has never been wiped out
in all of that time.
1489
01:20:48,277 --> 01:20:49,777
There's always been something
1490
01:20:49,779 --> 01:20:52,146
after every major
mass extinction.
1491
01:20:52,148 --> 01:20:57,117
So life will continue.
It just won't necessarily be us.
1492
01:20:58,120 --> 01:21:00,754
Narrator: An asteroid strike
on another world
1493
01:21:00,756 --> 01:21:04,124
may be how life on earth
started in the first place.
1494
01:21:04,126 --> 01:21:07,061
Bullock: There's an interesting
idea that an asteroid strike
1495
01:21:07,063 --> 01:21:10,164
on another planet could have
actually seeded life on earth.
1496
01:21:10,166 --> 01:21:12,233
And the way this works is,
you have a life
1497
01:21:12,235 --> 01:21:15,803
that's somehow gotten a foothold
on some other planet like mars,
1498
01:21:15,805 --> 01:21:18,038
a big asteroid strike hits
that planet
1499
01:21:18,040 --> 01:21:21,208
and knocks a piece of it off,
eventually rains down on earth,
1500
01:21:21,210 --> 01:21:25,112
carrying with it life.
1501
01:21:25,114 --> 01:21:30,451
We may owe the existence of life
here to asteroid impacts.
1502
01:21:32,855 --> 01:21:35,789
That's speculative,
but it's kind of a cool thought.
1503
01:21:38,094 --> 01:21:41,228
Narrator: Life seeding asteroids
may have hit us in the past,
1504
01:21:41,230 --> 01:21:44,465
and other asteroids
will hit us in the future.
1505
01:21:47,737 --> 01:21:50,004
One of those maybe apophis,
1506
01:21:50,006 --> 01:21:53,107
arriving in less than
half a century.
1507
01:21:54,477 --> 01:21:57,678
Maybe we'll deflect it.
1508
01:21:57,680 --> 01:22:02,116
Maybe it'll miss us
all on its own.
1509
01:22:02,118 --> 01:22:05,252
Either way, we need
to keep tabs on it.
1510
01:22:06,622 --> 01:22:08,789
Thaller: The best thing we can
do as a species, and it's funny
1511
01:22:08,791 --> 01:22:10,457
because it almost sounds
like I'm advocating
1512
01:22:10,459 --> 01:22:12,293
for more jobs for astronomers.
1513
01:22:12,295 --> 01:22:14,028
We need to keep looking
at the sky.
1514
01:22:14,030 --> 01:22:16,196
We need look at the sky
longer and deeper,
1515
01:22:16,198 --> 01:22:17,898
with more sensitive instruments
1516
01:22:17,900 --> 01:22:20,567
and get more of a sense
of what out there is around us.
1517
01:22:20,569 --> 01:22:24,738
That's what our species needs
to do to ultimately survive.
1518
01:22:24,740 --> 01:22:26,507
Because now we have
the ability
1519
01:22:26,509 --> 01:22:28,809
to see these things
a little bit better,
1520
01:22:28,811 --> 01:22:30,678
we have the ability
to protect ourselves better.
1521
01:22:30,680 --> 01:22:32,613
It doesn't have
to be a surprise.
1522
01:22:32,615 --> 01:22:35,049
You know, the first time we see
a big impact doesn't have to be
1523
01:22:35,051 --> 01:22:37,318
as it's bearing down
destroying our planet.
1524
01:22:37,320 --> 01:22:39,853
We can actually see it
before it gets to us
1525
01:22:39,855 --> 01:22:42,389
and decide
what we want to do about it.
1526
01:22:43,526 --> 01:22:47,828
Narrator: Earth's history is
littered with asteroid strikes.
1527
01:22:47,830 --> 01:22:51,598
Some wiped out
millions of species.
1528
01:22:51,600 --> 01:22:55,803
Some may have seeded life
in the first place.
1529
01:22:55,805 --> 01:22:58,205
What the future holds
and our relationship
1530
01:22:58,207 --> 01:23:01,942
with these space rocks,
no one knows.
1531
01:23:02,678 --> 01:23:06,447
Even though the chances of
something really large hitting
1532
01:23:06,449 --> 01:23:10,384
the earth are pretty small,
the consequences are dire.
1533
01:23:10,386 --> 01:23:13,420
It would really destroy
our planet or at least life
1534
01:23:13,422 --> 01:23:15,155
as we understand it.
1535
01:23:15,157 --> 01:23:18,425
And so in many ways,
asteroids are the greatest
1536
01:23:18,427 --> 01:23:20,060
threat that we face.
1537
01:23:20,062 --> 01:23:24,398
Life is fragile, so of course
we live in a larger environment
1538
01:23:24,400 --> 01:23:26,834
where something could come
and hit us at any time.
1539
01:23:26,836 --> 01:23:28,402
That's part of being alive.
1540
01:23:28,404 --> 01:23:30,704
There's no guarantee tomorrow
will happen.
1541
01:23:30,706 --> 01:23:33,340
But what there is
is a high likelihood
1542
01:23:33,342 --> 01:23:35,209
that you'll still be
safe tomorrow.
1543
01:23:37,947 --> 01:23:40,748
Bullock: Impacts from
space are rare,
1544
01:23:40,750 --> 01:23:43,384
but if they do happen,
it's a huge deal.
1545
01:23:43,386 --> 01:23:45,619
And so you've got to put those
two things together.
1546
01:23:45,621 --> 01:23:48,489
That means we got to
pay attention.
1547
01:23:48,491 --> 01:23:51,191
Durda: Those impacts have
happened many times in the past,
1548
01:23:51,193 --> 01:23:54,128
and they're going to continue to
happen many times in the future.
1549
01:23:54,130 --> 01:23:57,464
Fortunately it's not probably
in our immediate future.
1550
01:23:57,466 --> 01:24:02,002
Impacts are rare, but the earth
lives a long time.
1551
01:24:02,004 --> 01:24:04,271
So you're unlikely to get
in a car accident,
1552
01:24:04,273 --> 01:24:07,441
but if you drive enough, you're
going to get in a car accident.
1553
01:24:10,212 --> 01:24:11,779
Plait: Over a century
time scale,
1554
01:24:11,781 --> 01:24:14,048
yes, we should be concerned
about these.
1555
01:24:14,050 --> 01:24:17,317
But over the daily, weekly,
monthly, even yearly time scale,
1556
01:24:17,319 --> 01:24:19,153
I wouldn't sweat it too much.
1557
01:24:19,155 --> 01:24:21,688
I wouldn't say we should lose
sleep over an asteroid
1558
01:24:21,690 --> 01:24:23,257
or comet striking earth,
1559
01:24:23,259 --> 01:24:26,260
but the reality is
it will happen again.
1560
01:24:28,864 --> 01:24:31,031
Thaller: So when you think
about asteroid strikes,
1561
01:24:31,033 --> 01:24:33,000
remember this wonderful
dramatic universe
1562
01:24:33,002 --> 01:24:34,435
you find yourself in.
1563
01:24:34,437 --> 01:24:37,171
We're here because
stars died and exploded.
1564
01:24:37,173 --> 01:24:39,173
Life on earth wouldn't
be the same
1565
01:24:39,175 --> 01:24:41,208
if we didn't find ourselves
in this dramatic
1566
01:24:41,210 --> 01:24:43,510
and even dangerous environment
in space.
1567
01:24:43,512 --> 01:24:46,213
But this is who we are.
This is nothing new.
1568
01:24:46,215 --> 01:24:49,083
And this will continue
for the future of our planet.
1569
01:24:49,085 --> 01:24:55,989
♪
141360
Can't find what you're looking for?
Get subtitles in any language from opensubtitles.com, and translate them here.