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00:00:03,838 --> 00:00:07,742
Narrator: Our solar system
is a savage place.
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00:00:07,744 --> 00:00:11,282
From the ice volcanoes
of Saturn's moon Enceladus,
3
00:00:11,284 --> 00:00:15,127
to the vast lava fields
of Jupiter's Io,
4
00:00:15,129 --> 00:00:18,263
to our own world, the Earth,
5
00:00:18,265 --> 00:00:20,463
volcanoes destroy.
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00:00:20,465 --> 00:00:22,329
They also create.
7
00:00:22,331 --> 00:00:25,031
It is literally true that,
if there weren't volcanoes here,
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00:00:25,033 --> 00:00:26,431
we would not be here either.
9
00:00:26,433 --> 00:00:29,766
Narrator: Volcanoes shape
and change our climate.
10
00:00:29,768 --> 00:00:33,702
Volcanoes are the giver of life
and, also, the takers of life.
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00:00:33,704 --> 00:00:37,972
Narrator: Today's space probes
and telescopes
12
00:00:37,974 --> 00:00:42,676
reveal volcanoes
on worlds we once thought dead.
13
00:00:42,678 --> 00:00:47,314
Finding volcanoes on an object
that's smaller than our own Moon
14
00:00:47,316 --> 00:00:48,649
was a huge shock.
15
00:00:48,651 --> 00:00:52,420
Narrator: If volcanoes
exist on other worlds,
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00:00:52,422 --> 00:00:55,757
could we find life there, too?
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00:00:55,778 --> 00:00:59,778
♪ How the Universe Works 2x01 ♪
Volcanoes
Original Air Date on July 11, 2012
18
00:00:59,783 --> 00:01:03,783
== sync, corrected by elderman ==
19
00:01:16,670 --> 00:01:21,975
Planet Earth -- a jewel
in the darkness of space.
20
00:01:21,977 --> 00:01:26,949
Our home is timeless...
21
00:01:26,951 --> 00:01:28,951
beautiful...
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00:01:28,953 --> 00:01:33,217
and incredibly violent.
23
00:01:33,219 --> 00:01:37,088
Volcanoes are one of the most
powerful natural phenomena
24
00:01:37,090 --> 00:01:38,489
on the planet.
25
00:01:38,491 --> 00:01:41,159
They create new land,
26
00:01:41,161 --> 00:01:45,130
destroy the old.
27
00:01:45,132 --> 00:01:49,467
They blast out gases that
transform the air we breathe.
28
00:01:52,638 --> 00:01:54,373
Deep in our oceans,
29
00:01:54,375 --> 00:01:59,077
volcanic heat
fuels strange new life.
30
00:01:59,079 --> 00:02:02,447
Volcanoes help power
the living Earth.
31
00:02:05,151 --> 00:02:09,021
Now we search for signs of life
on alien worlds.
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00:02:11,158 --> 00:02:12,925
We know life needs water.
33
00:02:12,927 --> 00:02:15,862
We know it needs energy.
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00:02:15,864 --> 00:02:19,533
And that's where volcanoes
come in --
35
00:02:19,535 --> 00:02:22,937
they pump out
vast amounts of energy.
36
00:02:22,939 --> 00:02:26,775
Find volcanoes
on other worlds,
37
00:02:26,777 --> 00:02:29,078
and we might find life.
38
00:02:41,193 --> 00:02:43,528
The search starts here --
39
00:02:43,530 --> 00:02:47,065
the planet
orbiting closest to Earth...
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00:02:47,067 --> 00:02:51,604
Venus, a world that appears
very much like ours.
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00:02:55,942 --> 00:02:57,810
Venus and Earth
are roughly the same mass.
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00:02:57,812 --> 00:02:59,978
They're roughly the same
distance away from the Sun.
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00:02:59,980 --> 00:03:01,513
So they're kind of like twins.
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00:03:06,754 --> 00:03:08,655
Narrator:
3 billion years ago,
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00:03:08,657 --> 00:03:11,325
Earth and Venus
were very similar...
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00:03:14,062 --> 00:03:19,601
...new land, new oceans,
an atmosphere.
47
00:03:19,603 --> 00:03:22,403
Both planets
were perfect for life.
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00:03:22,405 --> 00:03:24,706
[ Thunder rumbling ]
49
00:03:24,708 --> 00:03:28,243
But on Venus,
something went wrong.
50
00:03:33,717 --> 00:03:35,018
Something made Venus
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00:03:35,020 --> 00:03:37,754
diverge radically
from the history of the Earth.
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00:03:37,756 --> 00:03:41,024
Venus took a definite turn to
the dark side a long time ago.
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00:03:41,026 --> 00:03:45,396
Venus is a hellhole,
our evil twin.
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00:03:47,500 --> 00:03:51,403
Narrator: Today, Venus' surface
is like a furnace.
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00:03:53,873 --> 00:03:56,876
Dr. Plait: It's 900 degrees
Fahrenheit on the surface.
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00:03:56,878 --> 00:03:59,345
It's hot enough to melt,
actually, some metals,
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00:03:59,347 --> 00:04:00,946
so you wouldn't stand a chance.
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00:04:00,948 --> 00:04:04,749
Narrator:
Venus is a greenhouse world.
59
00:04:04,751 --> 00:04:08,086
Its atmosphere
is thick with carbon dioxide.
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00:04:08,088 --> 00:04:10,021
[ Thunder crashing ]
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00:04:13,326 --> 00:04:17,897
It traps heat from the Sun
like a blanket.
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00:04:17,899 --> 00:04:20,934
These actual images
of Venus' surface
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00:04:20,936 --> 00:04:24,104
reveal a barren,
superheated wasteland.
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00:04:27,742 --> 00:04:31,613
Venus' thick blanket of CO2
killed the planet.
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00:04:37,419 --> 00:04:41,022
The CO2 came from volcanoes.
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00:04:46,662 --> 00:04:49,264
Orbiting space probes
gave the first clues.
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00:04:51,534 --> 00:04:55,237
Radar punched
through Venus' thick clouds...
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00:04:57,340 --> 00:05:02,512
...and revealed volcanic
formations across the planet...
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00:05:09,719 --> 00:05:14,523
...like formations we also see
right here on Earth --
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00:05:14,525 --> 00:05:17,626
the shield volcanoes of Hawaii.
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00:05:19,829 --> 00:05:24,064
Shield volcanoes get their name
from their round, flat shape.
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00:05:27,102 --> 00:05:31,774
These volcanoes ooze.
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00:05:31,776 --> 00:05:36,112
But they ooze
for thousands of years.
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00:05:36,114 --> 00:05:40,550
Once we were able to map
the entire surface of Venus
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00:05:40,552 --> 00:05:42,485
using cloud-penetrating radar,
76
00:05:42,487 --> 00:05:44,354
we started to study
the landforms there,
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00:05:44,356 --> 00:05:46,523
and we saw a lot
that was actually very familiar.
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00:05:46,525 --> 00:05:49,059
In particular,
we saw giant shield volcanoes
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00:05:49,061 --> 00:05:51,828
that are very similar to the
shield volcanoes here in Hawaii.
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00:05:51,830 --> 00:05:54,998
Narrator:
The radar images of Venus
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00:05:55,000 --> 00:05:59,737
were dead ringers for
the shield volcanoes on Hawaii.
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00:05:59,739 --> 00:06:04,609
Sometime in the past,
Venus had volcanoes.
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00:06:07,279 --> 00:06:11,983
For the first time, we had
a picture of Venus revealed,
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00:06:11,985 --> 00:06:14,919
and, boy, were we shocked.
85
00:06:14,921 --> 00:06:20,257
We found a scarred surface,
a volcanic surface.
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00:06:20,259 --> 00:06:23,794
There are at least a thousand
volcanoes that are very large
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00:06:23,796 --> 00:06:26,730
and maybe tens or even hundreds
of thousands of smaller ones.
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00:06:29,634 --> 00:06:34,571
Narrator: 3/4 of Venus' surface
is lava plains,
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00:06:34,573 --> 00:06:38,642
evidence
of an ancient cataclysm.
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00:06:38,644 --> 00:06:42,913
This could have been
a home for life.
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00:06:42,915 --> 00:06:46,583
Instead,
it was engulfed by fire.
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00:06:46,585 --> 00:06:51,321
Volcanoes belched trillions
of tons of carbon dioxide
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00:06:51,323 --> 00:06:53,557
into Venus' atmosphere.
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00:06:56,561 --> 00:06:58,662
Temperatures soared.
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00:06:58,664 --> 00:07:00,865
The seas boiled dry.
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00:07:00,867 --> 00:07:04,769
A runaway greenhouse process
began.
97
00:07:04,771 --> 00:07:06,571
Dr. Thaller:
On Earth, carbon dioxide
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00:07:06,573 --> 00:07:08,239
is able to absorb
into the rocks.
99
00:07:08,241 --> 00:07:10,341
It's able
to absorb into the ocean.
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00:07:10,343 --> 00:07:11,809
But on Venus, you have no water,
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00:07:11,811 --> 00:07:13,411
and it's now so hot
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00:07:13,413 --> 00:07:16,214
the carbon dioxide can't even
combine with the rocks.
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00:07:16,216 --> 00:07:20,084
So as carbon dioxide
was released into the atmosphere
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00:07:20,086 --> 00:07:22,153
by volcanoes a long time ago,
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00:07:22,155 --> 00:07:24,722
over time, there was
less and less of a method
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00:07:24,724 --> 00:07:26,591
to take it back
out of the atmosphere.
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Narrator:
If Venus ever had life,
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volcanoes
sterilized the entire world.
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Earth remains the only
living world we know of.
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That may change.
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This is the gas giant Jupiter,
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00:07:54,353 --> 00:07:57,120
its moons frozen and dead...
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...or so we thought.
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00:08:00,426 --> 00:08:05,296
Look closer,
and a mystery emerges...
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00:08:08,334 --> 00:08:14,906
...a cloud hanging
over a cold and lifeless world.
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[ Rumbling ]
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Narrator: On Venus,
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00:08:32,499 --> 00:08:37,102
volcanoes turned an earth-like
world into a superheated hell.
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00:08:38,765 --> 00:08:41,734
Finding volcanoes
on an earth-like world
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00:08:41,736 --> 00:08:45,171
was no surprise.
121
00:08:45,173 --> 00:08:49,943
But spotting volcanoes
on a moon was a shock.
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00:08:49,945 --> 00:08:51,345
[ Static crackles ]
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00:08:51,347 --> 00:08:54,581
In March 1979,
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00:08:54,583 --> 00:08:56,082
the Voyager 1 space probe
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00:08:56,084 --> 00:09:01,021
gave us our first close-up view
of Jupiter's tiny moon Io...
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00:09:01,023 --> 00:09:03,123
[ Whirring ]
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00:09:03,125 --> 00:09:06,593
...a world we once thought
cold and dead.
128
00:09:09,864 --> 00:09:12,065
Dr. Plait: And they saw
something really weird.
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00:09:12,067 --> 00:09:14,600
They saw this arc
next to the moon,
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00:09:14,602 --> 00:09:15,835
and it looked almost
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00:09:15,837 --> 00:09:18,171
as if like there was
another moon behind it.
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Kaku: And we scratched our heads
and said,
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00:09:19,741 --> 00:09:21,107
"Well, what could that be?
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00:09:21,109 --> 00:09:26,212
Everybody knows that io is dead,
boring, uninteresting."
135
00:09:26,214 --> 00:09:29,081
And then people realized,
"Oh, my God.
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It's a volcanic eruption."
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00:09:31,619 --> 00:09:34,587
We found that it's covered
with volcanoes.
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00:09:34,589 --> 00:09:36,823
It is tremendously
geologically active.
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00:09:36,825 --> 00:09:39,459
There are volcanoes
erupting all the time.
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00:09:39,461 --> 00:09:41,794
And what they're erupting
is a lot of sulfur,
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00:09:41,796 --> 00:09:43,229
and it gets very hot.
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00:09:43,231 --> 00:09:45,998
And sulfur, when it changes
temperature, changes color.
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It can be red or orange
or yellow or black.
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00:09:48,470 --> 00:09:50,737
And so these pictures
of the face of Io
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00:09:50,739 --> 00:09:52,038
make it look like a pizza
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00:09:52,040 --> 00:09:54,507
covered with different kinds
of cheese and olives
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00:09:54,509 --> 00:09:57,010
where the little black spots
are.
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Narrator:
Io is not dead.
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00:10:00,015 --> 00:10:03,917
It's alive and kicking.
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00:10:03,919 --> 00:10:07,387
It has
over 400 active volcanoes.
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00:10:11,424 --> 00:10:16,393
The largest, Pele, erupts
from a gigantic lava lake.
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00:10:18,628 --> 00:10:22,563
It reaches
nearly 250 miles into space.
153
00:10:24,966 --> 00:10:27,100
If we could stand
on the edge of that lava lake
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00:10:27,102 --> 00:10:30,603
and watch that plume shooting
off into the blackness of space,
155
00:10:30,605 --> 00:10:33,839
that would be
an incredible sight.
156
00:10:39,244 --> 00:10:45,313
Narrator: Pele's eruptions are
so huge because Io is so small.
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00:10:45,315 --> 00:10:48,082
There's nothing
to hold the lava back --
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00:10:48,084 --> 00:10:51,886
virtually no atmosphere
and very little gravity.
159
00:10:55,790 --> 00:10:57,323
These vast eruptions
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00:10:57,325 --> 00:11:01,093
make Earth volcanoes
look like firecrackers.
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00:11:01,095 --> 00:11:02,961
[ Rumbling ]
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00:11:05,765 --> 00:11:10,968
How can such a tiny moon
be so volcanic?
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00:11:10,970 --> 00:11:14,471
The answer is Jupiter.
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00:11:14,473 --> 00:11:18,407
Just as the Moon
raises tides in Earth's oceans,
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Jupiter raises tides on Io --
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00:11:22,379 --> 00:11:25,112
tides of solid rock.
167
00:11:28,515 --> 00:11:32,017
Io's orbit around Jupiter
is not a circle.
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Sometimes, it's closer.
169
00:11:33,854 --> 00:11:36,221
Sometimes, farther away.
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Jupiter gives Io
a gravitational pounding.
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00:11:42,227 --> 00:11:44,027
Dr. Plait:
And so, Jupiter's gravity
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00:11:44,029 --> 00:11:46,296
pulls on it a little bit harder
and a little bit weaker.
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00:11:46,298 --> 00:11:49,965
And what happens is
the moon stretches, like this.
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00:11:49,967 --> 00:11:51,266
It's called a tidal force.
175
00:11:51,268 --> 00:11:52,600
And it doesn't stretch
this much --
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00:11:52,602 --> 00:11:53,902
it's only a little bit.
177
00:11:53,904 --> 00:11:56,437
But, in fact,
it's enough to heat it up.
178
00:11:56,439 --> 00:11:57,905
It's just friction.
179
00:11:57,907 --> 00:12:00,007
It's the same way when you rub
your hands together really fast,
180
00:12:00,009 --> 00:12:00,974
they begin to feel warm.
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00:12:00,976 --> 00:12:02,008
Friction creates heat.
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00:12:02,010 --> 00:12:04,644
Narrator:
Jupiter's gravity
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00:12:04,646 --> 00:12:07,213
stretches and squeezes Io.
184
00:12:07,215 --> 00:12:09,181
In every two-day orbit,
185
00:12:09,183 --> 00:12:14,119
the ground rises and falls
by nearly 300 feet.
186
00:12:16,956 --> 00:12:21,759
This pummeling generates intense
heat and gigantic pressure.
187
00:12:25,564 --> 00:12:28,866
Wherever there's a weak part in
the crust, the lava rushes out.
188
00:12:28,868 --> 00:12:32,137
So the volcanism
is on a planetary scale.
189
00:12:32,139 --> 00:12:33,338
Unlike here on Earth,
190
00:12:33,340 --> 00:12:35,240
where there are certain bits
that are active
191
00:12:35,242 --> 00:12:37,242
around the plates
or in weak spots,
192
00:12:37,244 --> 00:12:41,479
this is an entire moon
that's one active hot spot.
193
00:12:41,481 --> 00:12:44,982
Narrator: Thanks to the
incredible power of gravity,
194
00:12:44,984 --> 00:12:47,985
Io is the most
volcanically active world
195
00:12:47,987 --> 00:12:49,787
in the solar system.
196
00:12:49,789 --> 00:12:53,458
The volcanism on Io
taught us something new.
197
00:12:53,460 --> 00:12:56,561
It taught us
that internal sources of energy
198
00:12:56,563 --> 00:12:58,530
can drive volcanism
199
00:12:58,532 --> 00:13:01,199
in a way that's different
from that on Earth.
200
00:13:01,201 --> 00:13:03,702
In outer space, tidal forces,
201
00:13:03,704 --> 00:13:07,339
the differential squeezing
of the moons of a gas giant,
202
00:13:07,341 --> 00:13:10,677
can also create
volcanic activity --
203
00:13:10,679 --> 00:13:13,179
that was a game-changer.
204
00:13:17,918 --> 00:13:23,423
Narrator: Io is a lava world,
superheated and violent.
205
00:13:23,425 --> 00:13:28,095
It's hard to imagine
anything surviving there.
206
00:13:28,097 --> 00:13:34,033
Yet the volcanic principle here
is the same as on Earth --
207
00:13:34,035 --> 00:13:38,237
pressurized, superheated magma
below the surface
208
00:13:38,239 --> 00:13:41,574
blasts through fissures
in the crust.
209
00:13:41,576 --> 00:13:45,877
But not all volcanoes
need magma.
210
00:13:45,879 --> 00:13:48,613
They don't even need to be hot.
211
00:13:52,317 --> 00:13:54,051
[ Rumbling ]
212
00:13:58,590 --> 00:14:03,961
Travel out past Jupiter
into the outer solar system,
213
00:14:03,963 --> 00:14:07,767
and it gets cold -- really cold.
214
00:14:09,737 --> 00:14:12,739
The distant moon Triton
is so cold
215
00:14:12,741 --> 00:14:16,476
that much of its tenuous
atmosphere can freeze solid.
216
00:14:19,147 --> 00:14:23,016
Yet there are volcanoes here --
217
00:14:23,018 --> 00:14:27,254
volcanoes that may hold
the secret of alien life.
218
00:14:35,233 --> 00:14:36,967
[ Rumbling ]
219
00:14:41,773 --> 00:14:45,843
Narrator: We think of volcanoes
as mountains of solid rock.
220
00:14:53,753 --> 00:14:58,357
Deep beneath,
rock is so hot and pressurized
221
00:14:58,359 --> 00:15:02,428
that it bursts violently out
as lava.
222
00:15:08,768 --> 00:15:11,669
But not all volcanoes
work this way.
223
00:15:14,607 --> 00:15:17,442
There are volcanoes
on other worlds
224
00:15:17,444 --> 00:15:20,078
that don't use molten rock
at all.
225
00:15:20,080 --> 00:15:26,051
Right at the frontiers
of the sun's planetary system,
226
00:15:26,053 --> 00:15:29,321
Triton orbits
the ice giant Neptune.
227
00:15:31,191 --> 00:15:34,093
2 1/2 billion miles
from the Sun,
228
00:15:34,095 --> 00:15:38,964
the temperature is
a frigid 390 degrees below zero.
229
00:15:42,569 --> 00:15:46,306
When NASA's Voyager probe
flew past,
230
00:15:46,308 --> 00:15:50,643
it revealed a world covered
mostly with frozen nitrogen ice.
231
00:15:50,645 --> 00:15:51,644
[ Static hisses ]
232
00:15:53,547 --> 00:15:57,216
But the probe
found something else.
233
00:15:57,218 --> 00:16:00,520
Dr. Thaller: When Voyager flew
by, it saw these black smudges,
234
00:16:00,522 --> 00:16:03,089
and all of the smudges
were going in one direction,
235
00:16:03,091 --> 00:16:04,724
almost as if there was a wind
236
00:16:04,726 --> 00:16:07,960
blowing dark material, dust,
in one direction.
237
00:16:07,962 --> 00:16:11,030
Narrator:
Signs of activity
238
00:16:11,032 --> 00:16:15,034
on a world so cold,
it freezes nitrogen --
239
00:16:15,036 --> 00:16:19,473
volcanoes at almost 400 degrees
below zero.
240
00:16:25,513 --> 00:16:28,015
Forget molten rock.
241
00:16:28,017 --> 00:16:31,818
Triton spews out a mixture
of nitrogen and moon dust.
242
00:16:37,425 --> 00:16:40,094
Dr. Thaller: And the geyser
not only has liquid nitrogen,
243
00:16:40,096 --> 00:16:41,328
which is in a fluid form,
244
00:16:41,330 --> 00:16:43,330
but, also, sort of dusty stuff
that's lighter,
245
00:16:43,332 --> 00:16:45,899
that can even go farther
in the weak winds.
246
00:16:45,901 --> 00:16:49,537
So you have this wonderful sort
of double plume of an icy area
247
00:16:49,539 --> 00:16:51,438
and then a darker, smudgy area,
248
00:16:51,440 --> 00:16:53,741
basically made of dust,
like moon dust.
249
00:16:53,743 --> 00:16:58,145
Narrator: Triton's surface
is nitrogen ice.
250
00:16:58,147 --> 00:17:01,548
Underneath, there are lakes
of liquid nitrogen.
251
00:17:01,550 --> 00:17:03,684
How?
252
00:17:03,686 --> 00:17:08,089
Scientists believe it's because
nitrogen ice lets light in,
253
00:17:08,091 --> 00:17:10,291
but doesn't let heat out.
254
00:17:10,293 --> 00:17:12,794
[ Ice cracking ]
255
00:17:12,796 --> 00:17:14,896
There's almost a bit
of a greenhouse effect
256
00:17:14,898 --> 00:17:16,231
going on on Triton,
257
00:17:16,233 --> 00:17:19,134
that there's a layer of
nitrogen ice that's transparent.
258
00:17:19,136 --> 00:17:21,770
And just like a greenhouse here
on Earth, when you have glass,
259
00:17:21,772 --> 00:17:23,472
light can pass through it,
260
00:17:23,474 --> 00:17:26,075
but then the heat
is trapped by the glass.
261
00:17:26,077 --> 00:17:30,379
Narrator: The Sun
shines through the surface
262
00:17:30,381 --> 00:17:32,548
and warms the nitrogen beneath.
263
00:17:37,521 --> 00:17:38,889
Just a few degrees
264
00:17:38,891 --> 00:17:42,593
is all it takes
to turn nitrogen ice into gas.
265
00:17:45,330 --> 00:17:48,099
A temperature gradient,
a change in that temperature --
266
00:17:48,101 --> 00:17:49,501
that's what's important.
267
00:17:49,503 --> 00:17:51,737
And that's enough to melt
the nitrogen
268
00:17:51,739 --> 00:17:53,172
underneath the surface on Triton
269
00:17:53,174 --> 00:17:55,341
and have it burst through
as a geyser.
270
00:18:00,748 --> 00:18:03,149
Narrator:
This is a cryovolcano,
271
00:18:03,151 --> 00:18:05,651
so cold
that the material it erupts
272
00:18:05,653 --> 00:18:08,554
would freeze water
as hard as rock.
273
00:18:12,692 --> 00:18:16,895
The solar system is more active
than we ever imagined.
274
00:18:20,065 --> 00:18:24,401
We have found weird eruptions
on many planets and moons.
275
00:18:28,573 --> 00:18:30,841
But so far, the only world
276
00:18:30,843 --> 00:18:35,078
where volcanoes
are linked to life is ours...
277
00:18:35,080 --> 00:18:36,914
or so we thought.
278
00:18:43,622 --> 00:18:47,492
This is Europa.
279
00:18:47,494 --> 00:18:52,363
It orbits Jupiter nearly
500 million miles from the Sun,
280
00:18:52,365 --> 00:18:57,002
a frozen 2,000-mile-wide
rock-hard ball of ice.
281
00:18:59,505 --> 00:19:03,509
From a distance,
its surface looks smooth.
282
00:19:03,511 --> 00:19:06,579
Up close,
it's a different story.
283
00:19:08,615 --> 00:19:12,785
Jupiter's enormous gravity
gives Europa a pounding,
284
00:19:12,787 --> 00:19:16,522
just like its neighbor, Io.
285
00:19:16,524 --> 00:19:19,091
The surface heaves and flexes,
286
00:19:19,093 --> 00:19:23,629
creating ridges
and deep crevices.
287
00:19:23,631 --> 00:19:27,566
When we first got close-up
images of Jupiter's moon Europa,
288
00:19:27,568 --> 00:19:29,668
they looked a little familiar,
289
00:19:29,670 --> 00:19:31,671
and it turns out
it looks like ice floes
290
00:19:31,673 --> 00:19:34,106
that you see
when you fly over the Arctic.
291
00:19:34,108 --> 00:19:37,109
And it turns out
it's the same thing.
292
00:19:37,111 --> 00:19:41,915
Europa has a several-mile-thick
shell of ice on its surface,
293
00:19:41,917 --> 00:19:46,386
and beneath that
is a global liquid ocean.
294
00:19:50,958 --> 00:19:54,595
Narrator: Magnetic readings
suggest Europa has an ocean
295
00:19:54,597 --> 00:19:57,130
that's a staggering
60 miles deep.
296
00:20:00,735 --> 00:20:04,537
Jupiter's gravitational pounding
297
00:20:04,539 --> 00:20:09,076
heats the rocky core
and melts the ice above.
298
00:20:09,078 --> 00:20:12,079
It's not unreasonable
to think that, as the core
299
00:20:12,081 --> 00:20:16,250
is being stretched by tides and
heated up, possibly even molten,
300
00:20:16,252 --> 00:20:17,418
there's some boundary
301
00:20:17,420 --> 00:20:20,821
between a hot core
and a liquid-water ocean.
302
00:20:28,696 --> 00:20:30,698
Narrator: On Earth,
303
00:20:30,700 --> 00:20:35,269
underwater eruptions
are surrounded by life.
304
00:20:35,271 --> 00:20:39,106
The same could happen on Europa.
305
00:20:41,343 --> 00:20:46,314
Here, the darkness is total...
306
00:20:46,316 --> 00:20:51,186
the pressure -- a crushing
2,000 earth atmospheres.
307
00:20:51,188 --> 00:20:55,624
A brutal world,
but perhaps a cradle for life.
308
00:20:57,894 --> 00:21:02,231
If life got off the ground here
on Earth, why not on Europa?
309
00:21:02,233 --> 00:21:04,333
All the ingredients are there --
310
00:21:04,335 --> 00:21:07,202
an energy source --
volcanic activity --
311
00:21:07,204 --> 00:21:10,072
a universal solvent --
liquid water --
312
00:21:10,074 --> 00:21:12,307
a rich hydrocarbon chemistry.
313
00:21:12,309 --> 00:21:15,143
We have this mixing bowl
of ingredients
314
00:21:15,145 --> 00:21:17,913
that happened on the Earth
3 1/2 billion years ago,
315
00:21:17,915 --> 00:21:20,749
and we have similar conditions
on Europa.
316
00:21:20,751 --> 00:21:22,118
So some people are saying,
317
00:21:22,120 --> 00:21:24,754
"If it happened here,
why not there?"
318
00:21:27,924 --> 00:21:32,728
Narrator: Life on Europa would
be hard, but not impossible.
319
00:21:32,730 --> 00:21:36,966
On Earth, there is life
at every extreme --
320
00:21:36,968 --> 00:21:41,337
searing heat, crushing pressure,
total darkness.
321
00:21:43,039 --> 00:21:48,744
Alien life on Europa
might look surprisingly similar.
322
00:21:48,746 --> 00:21:52,514
If life exists
under the ice cover of Europa,
323
00:21:52,516 --> 00:21:56,652
they would be aquatic,
but without eyes,
324
00:21:56,654 --> 00:21:58,087
because there's no light
to speak of.
325
00:21:58,089 --> 00:21:59,321
They would probably use sonar
326
00:21:59,323 --> 00:22:04,293
in order to make sense
of their surroundings --
327
00:22:04,295 --> 00:22:09,999
organisms that literally feed
off the energy from the volcano.
328
00:22:10,001 --> 00:22:14,671
Narrator: On Europa, volcanoes
could be the source of new life.
329
00:22:17,242 --> 00:22:20,978
It's even possible
that Europa is normal,
330
00:22:20,980 --> 00:22:25,850
that this is how worlds
with life generally are.
331
00:22:25,852 --> 00:22:29,287
Earth could be the exception.
332
00:22:32,024 --> 00:22:34,525
Think of it --
Europa could be a template
333
00:22:34,527 --> 00:22:39,429
for billions of moons out there
that have liquid oceans on them.
334
00:22:39,431 --> 00:22:40,730
So, all of a sudden,
335
00:22:40,732 --> 00:22:45,068
our horizons have expanded
several billion times
336
00:22:45,070 --> 00:22:47,403
by looking
at the moons of Jupiter.
337
00:22:47,405 --> 00:22:49,071
What a shock.
338
00:22:57,380 --> 00:23:02,218
Narrator: Our solar system alone
has over 170 moons.
339
00:23:02,220 --> 00:23:05,021
Multiply that
across the Universe,
340
00:23:05,023 --> 00:23:08,591
and that's a lot of places
where life might take hold.
341
00:23:10,794 --> 00:23:14,631
All it takes is liquid water
and a source of energy.
342
00:23:14,633 --> 00:23:18,702
Potentially,
volcanoes provide both.
343
00:23:20,638 --> 00:23:23,307
And they are everywhere.
344
00:23:26,277 --> 00:23:30,581
This is Saturn, twice as far
from the Sun as Jupiter.
345
00:23:32,317 --> 00:23:35,152
Yet it, too, has volcanic moons.
346
00:23:37,055 --> 00:23:42,826
And just like Jupiter's Europa,
these moons could harbor life.
347
00:23:58,128 --> 00:24:00,964
Narrator: This is one
of the strangest worlds
348
00:24:00,966 --> 00:24:05,601
in our solar system -- Saturn --
349
00:24:05,603 --> 00:24:09,973
a ring system
600,000 miles wide,
350
00:24:09,975 --> 00:24:13,543
an amazing 62 moons,
351
00:24:13,545 --> 00:24:16,112
and one with a secret.
352
00:24:17,682 --> 00:24:21,018
Enceladus is one of Saturn's
smaller, more distant moons.
353
00:24:21,020 --> 00:24:23,520
And it's been known for a long
time that it's covered in ice,
354
00:24:23,522 --> 00:24:25,222
because it's very bright,
very reflective.
355
00:24:25,224 --> 00:24:28,225
But when the Cassini spacecraft
went there,
356
00:24:28,227 --> 00:24:30,293
it discovered something amazing.
357
00:24:30,295 --> 00:24:35,533
Narrator: The Cassini probe
revealed something incredible --
358
00:24:35,535 --> 00:24:40,504
not on the planet itself,
but on Enceladus.
359
00:24:44,609 --> 00:24:50,514
Backlit by the sun, a gigantic
plume bursts out into space --
360
00:24:50,516 --> 00:24:54,886
a sure sign
of volcanic activity.
361
00:24:54,888 --> 00:24:57,122
[ Rumbling ]
362
00:25:01,727 --> 00:25:05,230
It was an amazing discovery,
363
00:25:05,232 --> 00:25:07,365
and it helped answer a question
364
00:25:07,367 --> 00:25:10,602
that has puzzled scientists
for decades --
365
00:25:10,604 --> 00:25:14,273
the mystery
of Saturn's "E" ring.
366
00:25:17,444 --> 00:25:20,646
Saturn's outermost ring is vast,
367
00:25:20,648 --> 00:25:24,416
almost 200,000 miles across,
368
00:25:24,418 --> 00:25:26,919
and it shouldn't exist.
369
00:25:28,521 --> 00:25:31,524
The ice particles
that make up most of the ring
370
00:25:31,526 --> 00:25:35,461
are too far from Saturn
to stay in orbit.
371
00:25:35,463 --> 00:25:38,665
They constantly drift away
into space.
372
00:25:41,068 --> 00:25:44,972
Something
replenishes the ring --
373
00:25:44,974 --> 00:25:50,043
the ice volcanoes of Enceladus.
374
00:25:50,045 --> 00:25:52,212
Dr. Plait: Those plumes
375
00:25:52,214 --> 00:25:54,381
that are ejected
from Enceladus' south pole --
376
00:25:54,383 --> 00:25:56,617
it turns out
that those are going into space.
377
00:25:56,619 --> 00:25:58,218
And they're not just going away.
378
00:25:58,220 --> 00:26:01,888
They're feeding a ring
around Saturn, the "E" ring.
379
00:26:04,125 --> 00:26:05,358
So this little moon
380
00:26:05,360 --> 00:26:08,328
is giving something back
to its parent planet.
381
00:26:17,338 --> 00:26:21,342
Narrator: Water blasts
from Enceladus' volcanoes,
382
00:26:21,344 --> 00:26:23,877
hits the vacuum of space,
383
00:26:23,879 --> 00:26:28,449
and instantly freezes
into tiny ice crystals,
384
00:26:28,451 --> 00:26:31,151
creating the vast "E" ring.
385
00:26:34,956 --> 00:26:38,225
One mystery solved.
386
00:26:38,227 --> 00:26:40,560
Another replaces it.
387
00:26:40,562 --> 00:26:43,563
What creates
the volcanic plumes?
388
00:26:45,967 --> 00:26:49,637
Cassini's cameras zoom in
on the moon's south pole
389
00:26:49,639 --> 00:26:54,841
and capture these huge chasms
scarring the surface.
390
00:26:54,843 --> 00:26:57,878
There are
these wonderfully huge cracks
391
00:26:57,880 --> 00:26:59,547
at the south pole of Enceladus,
392
00:26:59,549 --> 00:27:01,682
and as Enceladus
goes around Saturn,
393
00:27:01,684 --> 00:27:04,452
these cracks open and shut
as the tides go by.
394
00:27:04,454 --> 00:27:06,621
Now, these cracks are huge.
395
00:27:06,623 --> 00:27:08,423
They're hundreds of miles long.
396
00:27:08,425 --> 00:27:11,892
And when they begin to open,
you would have this big crevasse
397
00:27:11,894 --> 00:27:14,829
opening at maybe 100 miles
an hour down the length of that.
398
00:27:14,831 --> 00:27:17,265
It'd be incredibly spectacular.
399
00:27:17,267 --> 00:27:21,603
Narrator:
Huge gravitational forces
400
00:27:21,605 --> 00:27:25,773
crack the surface open
and closed at enormous speeds.
401
00:27:27,742 --> 00:27:30,777
Like Europa and Io's orbits
'round Jupiter,
402
00:27:30,779 --> 00:27:34,546
Enceladus' orbit 'round Saturn
is elliptical.
403
00:27:38,584 --> 00:27:41,952
This helps generate the heat
to melt ice
404
00:27:41,954 --> 00:27:46,857
and create oceans of water
beneath the surface.
405
00:27:46,859 --> 00:27:49,159
Dr. Thaller:
The conditions of the water
406
00:27:49,161 --> 00:27:50,760
underneath Enceladus' surface
407
00:27:50,762 --> 00:27:52,228
are absolutely perfect for life.
408
00:27:52,230 --> 00:27:53,729
It's the right temperature.
409
00:27:53,731 --> 00:27:55,363
It'd be a good pressure
for life.
410
00:27:55,365 --> 00:27:58,132
Liquid water would be just
like seawater here on Earth.
411
00:27:58,134 --> 00:27:59,601
And the chemistry of the water
412
00:27:59,603 --> 00:28:01,436
we see shooting
out of these vents
413
00:28:01,438 --> 00:28:04,205
suggests that it is
very similar -- there's salt.
414
00:28:04,207 --> 00:28:06,507
There's organic material in it,
as well.
415
00:28:06,509 --> 00:28:08,743
So we've identified a place
in the solar system
416
00:28:08,745 --> 00:28:10,979
where there very well
may be life right now.
417
00:28:16,485 --> 00:28:20,521
Narrator: Cassini has detected
complex carbon molecules
418
00:28:20,523 --> 00:28:22,223
in the ice plumes.
419
00:28:22,225 --> 00:28:25,293
Combined with liquid water,
420
00:28:25,295 --> 00:28:28,029
they suggest
that just maybe life
421
00:28:28,031 --> 00:28:31,566
could survive deep
within this enigmatic moon.
422
00:28:37,439 --> 00:28:40,208
Enceladus may not be alone.
423
00:28:40,210 --> 00:28:44,513
Another of Saturn's moons
might also harbor life --
424
00:28:44,515 --> 00:28:49,952
Titan, one of the largest moons
in our solar system,
425
00:28:49,954 --> 00:28:53,088
the only moon
with a thick atmosphere...
426
00:28:55,691 --> 00:28:57,692
...a frozen world --
427
00:28:57,694 --> 00:29:02,163
ice as hard as rock,
lakes of liquid methane.
428
00:29:04,199 --> 00:29:08,168
Yet here, too, we might find
evidence of volcanoes
429
00:29:08,170 --> 00:29:11,939
and the tantalizing prospect
of alien life.
430
00:29:23,403 --> 00:29:27,239
Narrator: A raging inferno
on the surface of Io,
431
00:29:27,241 --> 00:29:30,976
eruptions of ice and nitrogen
on Triton...
432
00:29:32,879 --> 00:29:35,782
Volcanoes are one
of the most destructive forces
433
00:29:35,784 --> 00:29:38,150
in our Universe.
434
00:29:41,856 --> 00:29:47,660
But out of annihilation
comes the possibility of life,
435
00:29:47,662 --> 00:29:53,466
even here on Saturn's
mysterious moon Titan.
436
00:29:55,001 --> 00:29:59,738
It's 3,000 miles across,
437
00:29:59,740 --> 00:30:02,941
larger than the planet Mercury.
438
00:30:02,943 --> 00:30:06,344
It's the only moon
in our solar system
439
00:30:06,346 --> 00:30:09,347
with a thick atmosphere.
440
00:30:09,349 --> 00:30:15,286
There is weather here -- storms,
winds, rain, even lakes --
441
00:30:15,288 --> 00:30:20,391
all so cold that liquid methane
takes the place of water.
442
00:30:21,660 --> 00:30:26,063
And it's loaded with chemicals
that life needs to survive.
443
00:30:27,699 --> 00:30:29,934
Titan has turned out to be
absolutely one
444
00:30:29,936 --> 00:30:32,936
of the most interesting places
in the solar system.
445
00:30:32,938 --> 00:30:35,072
It's an active world.
446
00:30:35,074 --> 00:30:37,708
It's the only moon
with a thick atmosphere --
447
00:30:37,710 --> 00:30:39,243
an atmosphere
very much like Earth,
448
00:30:39,245 --> 00:30:40,744
because it's mostly nitrogen,
449
00:30:40,746 --> 00:30:44,081
and it turns out, an atmosphere
loaded with organic molecules.
450
00:30:47,018 --> 00:30:49,887
Narrator: Methane gas
high in Titan's atmosphere
451
00:30:49,889 --> 00:30:51,722
reacts with sunlight
452
00:30:51,724 --> 00:30:55,459
and creates the kind
of chemicals life depends on.
453
00:30:58,096 --> 00:31:03,866
But if sunlight converts methane
into organics continuously,
454
00:31:03,868 --> 00:31:06,335
why doesn't the methane run out?
455
00:31:09,939 --> 00:31:11,406
The atmosphere's
full of methane,
456
00:31:11,408 --> 00:31:12,741
and yet we know methane
457
00:31:12,743 --> 00:31:14,943
is being destroyed by sunlight
on a short time scale,
458
00:31:14,945 --> 00:31:16,111
so it shouldn't be there.
459
00:31:16,113 --> 00:31:19,315
There needs to be
a source of methane.
460
00:31:19,317 --> 00:31:20,882
Narrator:
Something on Titan
461
00:31:20,884 --> 00:31:23,986
pumps out a continuous
supply of methane.
462
00:31:26,189 --> 00:31:30,359
Cassini has detected
what looks like a crater.
463
00:31:30,361 --> 00:31:34,763
Its interior
is as deep as the Grand Canyon.
464
00:31:34,765 --> 00:31:37,465
Infrared cameras
reveal different types
465
00:31:37,467 --> 00:31:41,536
of materials
surrounding the crater.
466
00:31:41,538 --> 00:31:46,440
Scientists believe the green
areas could be volcanic,
467
00:31:46,442 --> 00:31:51,245
perhaps plains of lava
ejected from Titan's interior.
468
00:31:55,250 --> 00:31:56,884
If it exists,
469
00:31:56,886 --> 00:32:02,190
lava Titan-style
is a superchilled icy slush.
470
00:32:03,392 --> 00:32:06,060
But compared
to the rest of Titan,
471
00:32:06,062 --> 00:32:09,497
even ice slush is scalding hot.
472
00:32:09,499 --> 00:32:12,500
On Titan, the hot liquid
spewing from volcanoes
473
00:32:12,502 --> 00:32:15,303
might be ammonia or water.
474
00:32:15,305 --> 00:32:17,739
Normally, those are frozen solid
on the surface,
475
00:32:17,741 --> 00:32:19,641
but if they're heated
beneath the surface somehow,
476
00:32:19,643 --> 00:32:21,409
they could erupt out.
477
00:32:21,411 --> 00:32:26,415
On Titan, what comes out of
volcanoes is methane and ethane,
478
00:32:26,417 --> 00:32:27,883
and that's probably the reason
479
00:32:27,885 --> 00:32:31,053
why we have
this very thick cloud cover,
480
00:32:31,055 --> 00:32:33,089
this orange haze around Titan.
481
00:32:33,091 --> 00:32:34,524
This haze
482
00:32:34,526 --> 00:32:37,994
probably came from outgassing
from the volcanoes of Titan.
483
00:32:39,998 --> 00:32:44,902
Even for volcanoes on a world
as cold as Titan, you need heat.
484
00:32:44,904 --> 00:32:49,173
That's what turns ice into
liquid and generates eruptions.
485
00:32:52,377 --> 00:32:56,447
On Titan,
that heat has two sources.
486
00:32:58,583 --> 00:33:02,053
Radioactive materials
warm the interior.
487
00:33:05,024 --> 00:33:09,928
And Saturn's huge gravity
massages the moon,
488
00:33:09,930 --> 00:33:12,364
just like Enceladus.
489
00:33:14,400 --> 00:33:17,002
These two forces
generate enough heat
490
00:33:17,004 --> 00:33:19,404
to turn ice into water
491
00:33:19,406 --> 00:33:23,075
and liquid methane to gas.
492
00:33:23,077 --> 00:33:26,445
We think of volcanoes
as being hot and ice as cold,
493
00:33:26,447 --> 00:33:30,716
and yet if you're out on Titan,
494
00:33:30,718 --> 00:33:32,417
where you're a billion miles
from the Sun
495
00:33:32,419 --> 00:33:34,252
and it's -- it's quite cold,
496
00:33:34,254 --> 00:33:36,088
then those floes
497
00:33:36,090 --> 00:33:38,990
of just-barely-above-freezing
water ammonia ice --
498
00:33:38,992 --> 00:33:41,059
they might be
the hottest things around.
499
00:33:41,061 --> 00:33:42,794
So "hot" is a relative term,
500
00:33:42,796 --> 00:33:44,596
depending on where
in the solar system you are.
501
00:33:48,368 --> 00:33:50,603
Narrator:
Could volcanoes on Titan
502
00:33:50,605 --> 00:33:54,240
give life a chance
to survive here?
503
00:33:54,242 --> 00:33:57,143
Life as we know it
needs an atmosphere...
504
00:33:59,914 --> 00:34:02,815
...a solid surface...
505
00:34:02,817 --> 00:34:04,617
liquid water...
506
00:34:04,619 --> 00:34:08,288
and the heat to drive
chemical reactions.
507
00:34:08,290 --> 00:34:13,526
On Titan, volcanoes
could provide them all.
508
00:34:13,528 --> 00:34:17,930
If you have a volcano on Titan,
you'll have heat added to that,
509
00:34:17,932 --> 00:34:19,899
and all of a sudden,
you'll have liquid water
510
00:34:19,901 --> 00:34:22,268
surrounded
by organic material --
511
00:34:22,270 --> 00:34:24,971
I mean, literally, anything
you need for the start of life.
512
00:34:24,973 --> 00:34:28,808
Narrator:
If life does exist on Titan,
513
00:34:28,810 --> 00:34:31,777
it would be truly alien.
514
00:34:31,779 --> 00:34:35,614
It would breathe hydrogen
in place of oxygen,
515
00:34:35,616 --> 00:34:39,151
perhaps swimming through lakes
of liquid methane
516
00:34:39,153 --> 00:34:42,354
at 300 degrees below zero.
517
00:34:43,924 --> 00:34:46,158
Kaku: Perhaps there are
oceans of ethane.
518
00:34:46,160 --> 00:34:47,994
Perhaps there are tide pools
519
00:34:47,996 --> 00:34:52,165
and perhaps volcanic activity
and hydrothermal activity.
520
00:34:52,167 --> 00:34:54,000
Perhaps there are hot springs.
521
00:34:54,002 --> 00:34:55,869
Perhaps volcanic heat
522
00:34:55,871 --> 00:35:01,242
could generate enough to get
life off the ground in Titan.
523
00:35:01,244 --> 00:35:04,312
That's a speculation,
but it can't be ruled out.
524
00:35:06,615 --> 00:35:09,050
Narrator: But we may not need
to travel this far
525
00:35:09,052 --> 00:35:11,452
to find signs of life.
526
00:35:11,454 --> 00:35:16,657
We may find it on a volcanic
world much closer to home...
527
00:35:18,394 --> 00:35:22,030
...the red planet, Mars.
528
00:35:36,048 --> 00:35:38,648
Narrator:
Volcanoes are everywhere
529
00:35:38,652 --> 00:35:40,585
across the solar system.
530
00:35:42,955 --> 00:35:46,158
Worlds like Io,
Titan, and Triton
531
00:35:46,160 --> 00:35:49,829
are complex, dynamic,
and violent.
532
00:35:53,367 --> 00:35:55,569
Once, we thought that Earth
533
00:35:55,571 --> 00:36:00,374
was the only planet
with volcanoes and with life.
534
00:36:02,711 --> 00:36:05,046
Now we find volcanoes
everywhere,
535
00:36:05,048 --> 00:36:09,083
but we have yet
to find alien life.
536
00:36:09,085 --> 00:36:14,555
Volcanoes embody the sheer power
of creation and destruction.
537
00:36:14,557 --> 00:36:16,157
They go hand in hand.
538
00:36:16,159 --> 00:36:18,960
It is literally true that,
if there weren't volcanoes here,
539
00:36:18,962 --> 00:36:20,561
we would not be here either.
540
00:36:20,563 --> 00:36:23,631
In the caldrons of volcanoes
is the origin of life.
541
00:36:26,835 --> 00:36:30,004
Narrator:
Volcanoes create new landscapes,
542
00:36:30,006 --> 00:36:33,573
seed the atmosphere
with complex chemicals,
543
00:36:33,575 --> 00:36:37,477
replace the old with the new.
544
00:36:39,880 --> 00:36:43,683
If volcanoes are bound up
with the processes of life,
545
00:36:43,685 --> 00:36:47,320
then where is the life
on other worlds?
546
00:36:54,727 --> 00:36:58,630
Perhaps the answer
originates in deep time,
547
00:36:58,632 --> 00:37:00,832
when the solar system
was young...
548
00:37:03,702 --> 00:37:08,640
...on a young planet
much like our own.
549
00:37:08,642 --> 00:37:12,744
This is Mars.
550
00:37:12,746 --> 00:37:18,383
3 billion years ago,
it had active volcanoes.
551
00:37:18,385 --> 00:37:21,286
One still remains --
552
00:37:21,288 --> 00:37:24,590
the largest volcano
in the solar system.
553
00:37:27,394 --> 00:37:33,031
The cliffs leading to it
are over 6 miles high.
554
00:37:33,033 --> 00:37:38,035
Mount Everest would sit
comfortably in their shadow,
555
00:37:38,037 --> 00:37:41,573
and those are
just the foothills.
556
00:37:41,575 --> 00:37:47,513
This is
the awe-inspiring Olympus Mons.
557
00:37:47,515 --> 00:37:51,351
It covers an area
the size of Arizona.
558
00:37:51,353 --> 00:37:56,590
Its crater alone
is 53 miles wide.
559
00:37:56,592 --> 00:38:01,194
A goliath like this takes
millions of years to build,
560
00:38:01,196 --> 00:38:04,364
time that volcanoes
here on Earth never get.
561
00:38:10,604 --> 00:38:13,807
On Earth,
the crust is always moving.
562
00:38:16,911 --> 00:38:18,945
[ Cracking ]
563
00:38:18,947 --> 00:38:21,549
Deep below, a single hot spot
564
00:38:21,551 --> 00:38:23,784
pushes magma
through the surface,
565
00:38:23,786 --> 00:38:27,054
building a new volcanic island.
566
00:38:27,056 --> 00:38:31,725
But while the hot spot stays
still, the surface is moving.
567
00:38:31,727 --> 00:38:35,529
The new island
moves away from the hot spot,
568
00:38:35,531 --> 00:38:38,999
and a new volcanic island
takes its place.
569
00:38:42,070 --> 00:38:44,071
Mars is different.
570
00:38:44,073 --> 00:38:47,675
The crust is locked solid.
571
00:38:47,677 --> 00:38:50,711
On Mars, there's just none
of that tectonic activity.
572
00:38:50,713 --> 00:38:52,946
The crust
is one big solid plate,
573
00:38:52,948 --> 00:38:54,281
and so if there's a hot spot,
574
00:38:54,283 --> 00:38:57,151
it just sits there and builds
and builds and builds.
575
00:38:57,153 --> 00:38:59,520
And you get a bigger
and bigger and bigger volcano.
576
00:38:59,522 --> 00:39:02,189
And that's why Olympus Mons
is so huge.
577
00:39:09,998 --> 00:39:12,099
Narrator:
Olympus Mons today
578
00:39:12,101 --> 00:39:16,003
is a frozen relic
of a distant, warmer past.
579
00:39:20,943 --> 00:39:23,611
Mars' shrunken atmosphere
580
00:39:23,613 --> 00:39:29,083
means that Olympus
now reaches almost into space --
581
00:39:29,085 --> 00:39:34,755
a true colossus, an extinct
volcano on a dying world.
582
00:39:41,462 --> 00:39:44,530
But Mars'
ancient volcanic terrain
583
00:39:44,532 --> 00:39:47,533
could, one day,
harbor life again.
584
00:39:50,537 --> 00:39:54,407
The evidence
is right here on Earth.
585
00:39:57,110 --> 00:39:58,811
On Hawaii, volcanoes
586
00:39:58,813 --> 00:40:05,283
have created mysterious tunnels
called lava tubes,
587
00:40:05,285 --> 00:40:07,085
channels left behind
588
00:40:07,087 --> 00:40:10,755
when torrents of molten rock
surge into the sea.
589
00:40:15,195 --> 00:40:18,463
But some are now empty,
590
00:40:18,465 --> 00:40:21,033
and that offers us
an opportunity.
591
00:40:24,104 --> 00:40:28,108
Lava tubes are formed when
you have an underground river
592
00:40:28,110 --> 00:40:33,948
of hot basaltic lava,
2,000-degree magma, molten rock.
593
00:40:33,950 --> 00:40:38,820
And picture it
like a frozen river of water,
594
00:40:38,822 --> 00:40:40,888
with the ice crust
forming on the top.
595
00:40:40,890 --> 00:40:41,956
It's the same thing,
596
00:40:41,958 --> 00:40:44,592
only here,
the crust is solid rock
597
00:40:44,594 --> 00:40:47,596
and the river keeps flowing
underneath and makes this cave,
598
00:40:47,598 --> 00:40:49,064
this lava tube.
599
00:40:49,066 --> 00:40:52,167
Narrator:
Extraordinary recent images
600
00:40:52,169 --> 00:40:58,541
suggest Mars' volcanoes also
may have created lava tubes.
601
00:40:58,543 --> 00:41:02,112
Any planet with basaltic
volcanism, any rocky planet,
602
00:41:02,114 --> 00:41:03,847
will probably have lava tubes.
603
00:41:03,849 --> 00:41:06,950
And now we've found
a couple of them on Mars,
604
00:41:06,952 --> 00:41:08,452
in places
where there are skylights,
605
00:41:08,454 --> 00:41:10,887
places where the roof
has collapsed
606
00:41:10,889 --> 00:41:14,023
and you can see from orbit
right into those lava tubes.
607
00:41:14,025 --> 00:41:17,059
Narrator:
If some tubes have collapsed,
608
00:41:17,061 --> 00:41:19,495
perhaps many others
are still intact,
609
00:41:19,497 --> 00:41:24,433
the ancient relics
of Mars' volcanic past.
610
00:41:27,737 --> 00:41:32,008
Now, after lying dormant
for perhaps millions of years,
611
00:41:32,010 --> 00:41:37,681
these lava tubes could bring
life back to the red planet.
612
00:41:37,683 --> 00:41:41,951
That life will be us.
613
00:41:44,588 --> 00:41:48,725
One of the challenges of
living on Mars for future humans
614
00:41:48,727 --> 00:41:50,593
will be
the radiation environment.
615
00:41:50,595 --> 00:41:53,229
And in particular,
when there are solar storms,
616
00:41:53,231 --> 00:41:57,133
the cosmic rays coming in
can be deadly.
617
00:41:57,135 --> 00:42:02,572
And having a storm shelter
under some large mass of rock
618
00:42:02,574 --> 00:42:03,874
is really the best way
619
00:42:03,876 --> 00:42:06,376
to protect yourself
from cosmic rays.
620
00:42:09,413 --> 00:42:13,616
Narrator: The tubes and caves
of Mars' extinct volcanoes
621
00:42:13,618 --> 00:42:17,454
might one day
make a perfect home --
622
00:42:17,456 --> 00:42:23,192
holding in air, shielding us
from deadly radiation.
623
00:42:23,194 --> 00:42:25,362
A long-dead volcano
624
00:42:25,364 --> 00:42:29,499
could help fill a world
with new life.
625
00:42:33,737 --> 00:42:38,441
Volcanoes can destroy,
but they can also create.
626
00:42:38,443 --> 00:42:44,914
From the superheated vents
of Europa's 60-mile-deep ocean
627
00:42:44,916 --> 00:42:49,285
to the water volcanoes of Titan
and the rock volcanoes of Earth,
628
00:42:49,287 --> 00:42:53,156
vast geologic processes
629
00:42:53,158 --> 00:42:56,893
shape our worlds,
our imaginations,
630
00:42:56,895 --> 00:43:00,197
and perhaps
the very stuff of life.
631
00:43:00,222 --> 00:43:04,222
== sync, corrected by