1
00:00:03,167 --> 00:00:05,867
Narrator:
COMETS ARE A CELESTIAL MYSTERY.

2
00:00:08,333 --> 00:00:11,233
THEY ARE MESSENGERS
FROM DEEP SPACE ITSELF --

3
00:00:11,233 --> 00:00:13,767
TIME MACHINES
FROM THE EARLY UNIVERSE.

4
00:00:13,767 --> 00:00:18,767
Narrator: COMETS COULD UNLOCK THE
DEEPEST SECRETS OF OUR COSMOS.

5
00:00:21,067 --> 00:00:23,700
IF WE CAN ESTABLISH
A CORRELATION

6
00:00:23,700 --> 00:00:26,300
BETWEEN AMINO ACIDS ON COMETS
AND LIFE ON EARTH,

7
00:00:26,300 --> 00:00:29,900
THAT WOULD BE ONE OF THE MOST
SIGNIFICANT FINDINGS IN SCIENCE.

8
00:00:29,900 --> 00:00:33,700
Narrator:
THEY THREATEN OUR VERY SURVIVAL.

9
00:00:33,700 --> 00:00:36,067
WE'RE TALKING ABOUT SOMETHING
THE SIZE OF A MOUNTAIN,

10
00:00:36,067 --> 00:00:37,500
SO THE AMOUNT OF ENERGY

11
00:00:37,500 --> 00:00:39,500
THAT THIS THING WOULD RELEASE
UPON IMPACT IS DEVASTATING.

12
00:00:40,967 --> 00:00:42,133
Narrator:
YET WITHOUT COMETS,

13
00:00:42,133 --> 00:00:45,400
WE MIGHT NOT BE HERE.

14
00:00:45,400 --> 00:00:47,633
WE MAY OWE
A GREAT COSMIC DEBT TO COMETS

15
00:00:47,633 --> 00:00:49,433
BECAUSE
THEY MAY HAVE BEEN RESPONSIBLE

16
00:00:49,433 --> 00:00:51,733
FOR BRINGING THE CHEMICALS
THAT WE REQUIRE FOR LIFE

17
00:00:51,733 --> 00:00:53,000
TO THE EARTH.

18
00:00:53,000 --> 00:00:56,000
-- Captions by VITAC --
www.vitac.com

19
00:00:56,000 --> 00:00:59,000
CAPTIONS PAID FOR BY
DISCOVERY COMMUNICATIONS

20
00:01:06,800 --> 00:01:10,333
[ DRAMATIC MUSIC PLAYS ]

21
00:01:18,267 --> 00:01:21,367
Narrator: A DRAMATIC STREAK
OF LIGHT ACROSS THE SKY,

22
00:01:21,367 --> 00:01:28,433
A PASSING COMET
IS AN ASTONISHING SIGHT.

23
00:01:28,433 --> 00:01:29,767
Dr. Plait: THEY'RE BEAUTIFUL,

24
00:01:29,767 --> 00:01:32,667
THESE FUZZY, GLOWING BALLS
WITH THE TAIL COMING OFF.

25
00:01:32,667 --> 00:01:34,067
IT'S REALLY SOMETHING.

26
00:01:34,067 --> 00:01:37,100
YOU JUST DON'T GET TO SEE
AN OBJECT LIKE THAT VERY OFTEN.

27
00:01:37,100 --> 00:01:38,367
COMETS ARE EXTRAORDINARY.

28
00:01:38,367 --> 00:01:40,833
IF YOU GET TO SEE A COMET
FOR THE VERY FIRST TIME,

29
00:01:40,833 --> 00:01:42,333
IT'LL STICK WITH YOU FOREVER.

30
00:01:42,333 --> 00:01:46,100
THE JOURNEY OF A COMET AS IT
SAILS THROUGH THE SOLAR SYSTEM

31
00:01:46,100 --> 00:01:49,367
IS THE MOST FANTASTIC
OF ALL ASTRONOMICAL OBJECTS.

32
00:01:53,900 --> 00:01:57,700
Narrator: IT LOOPS IN TOWARD THE
SUN FROM THE DEPTHS OF SPACE --

33
00:01:57,700 --> 00:02:01,667
AN ODYSSEY THAT CAN LAST
MILLIONS OF YEARS.

34
00:02:03,733 --> 00:02:09,267
MANY PASS BY THE EARTH SO OFTEN,
THEY'RE ALMOST LIKE OLD FRIENDS.

35
00:02:13,067 --> 00:02:17,467
EVERY COMET IS A FROZEN MASS
OF ROCK AND ICE

36
00:02:17,467 --> 00:02:19,667
SEVERAL MILES ACROSS.

37
00:02:19,667 --> 00:02:24,933
BUT ALL WE SEE
IS A GLOWING BALL OF LIGHT...

38
00:02:24,933 --> 00:02:27,967
AND A LONG, SWEEPING TAIL.

39
00:02:33,067 --> 00:02:37,867
YET COMETS
ARE MORE THAN COSMIC FIREWORKS.

40
00:02:37,867 --> 00:02:39,633
THEY COULD HELP UNLOCK

41
00:02:39,633 --> 00:02:42,867
SOME OF THE DEEPEST MYSTERIES
IN SCIENCE.

42
00:02:46,500 --> 00:02:49,333
WE'RE TRYING TO FIGURE OUT, AS
SCIENTISTS, WHERE WE CAME FROM,

43
00:02:49,333 --> 00:02:52,333
AND THAT MEANS EVERYTHING FROM
THE BEGINNING OF THE UNIVERSE

44
00:02:52,333 --> 00:02:55,200
TO THE BEGINNING OF THE SOLAR
SYSTEM TO HOW LIFE STARTED.

45
00:02:55,200 --> 00:02:56,867
COMETS REALLY FIT INTO THAT.

46
00:02:56,867 --> 00:03:00,433
THEY REALLY GIVE US CLUES ABOUT
HOW THE SOLAR SYSTEM FORMED.

47
00:03:00,433 --> 00:03:02,233
IF WE CAN'T UNDERSTAND COMETS,

48
00:03:02,233 --> 00:03:04,500
WE DON'T UNDERSTAND
HOW WE GOT HERE.

49
00:03:08,067 --> 00:03:11,333
Narrator: COMETS MAY EVEN BE
THE SOURCE OF LIFE ITSELF.

50
00:03:13,333 --> 00:03:16,300
WE MAY OWE OUR EXISTENCE
TO THE FACT THAT COMETS,

51
00:03:16,300 --> 00:03:17,800
BILLIONS OF YEARS AGO,

52
00:03:17,800 --> 00:03:21,167
CAME TO EARTH AND BROUGHT THE
NECESSARY INGREDIENTS FOR LIFE.

53
00:03:21,167 --> 00:03:25,333
Narrator: THEY CAN ALSO CAUSE
ENORMOUS DESTRUCTION.

54
00:03:35,933 --> 00:03:39,200
COMETS COULD KILL US ALL.

55
00:03:39,200 --> 00:03:42,333
IF A COMET WERE
TO HIT THE EARTH, WATCH OUT.

56
00:03:42,333 --> 00:03:44,300
IT WOULD BE A PLANET-BUSTER.

57
00:03:44,300 --> 00:03:47,233
IT WOULD BE AN OBJECT SUFFICIENT
TO WIPE OUT

58
00:03:47,233 --> 00:03:49,800
ALL LIFE AS WE KNOW IT
ON THE PLANET.

59
00:03:49,800 --> 00:03:53,067
Narrator: LEARN ABOUT COMETS,

60
00:03:53,067 --> 00:03:56,733
AND JUST MAYBE WE WILL LEARN
HOW TO SURVIVE THEM...

61
00:03:58,367 --> 00:04:02,367
...AND BEGIN TO UNDERSTAND
HOW THE UNIVERSE WORKS.

62
00:04:05,600 --> 00:04:07,067
Dr. Plait:
WHEN WE STUDY THEM,

63
00:04:07,067 --> 00:04:08,933
WE'RE LEARNING
WHAT THE SOLAR SYSTEM WAS LIKE

64
00:04:08,933 --> 00:04:10,367
WHEN IT WAS FIRST FORMING.

65
00:04:10,367 --> 00:04:13,300
AND WE CAN LEARN ABOUT WHAT
OTHER SOLAR SYSTEMS WERE LIKE,

66
00:04:13,300 --> 00:04:14,667
AS WELL.

67
00:04:14,667 --> 00:04:16,667
AND, HOPEFULLY, THAT WILL TEACH
US A TREMENDOUS AMOUNT

68
00:04:16,667 --> 00:04:18,867
ABOUT HOW STARS FORM
AND HOW PLANETS FORM

69
00:04:18,867 --> 00:04:21,400
AND HOW COMETS THEMSELVES
WERE ORIGINALLY FORMED.

70
00:04:21,400 --> 00:04:25,933
[ DRAMATIC MUSIC PLAYS ]

71
00:04:25,933 --> 00:04:29,267
Narrator: COMETS DATE BACK TO
THE BIRTH OF OUR SOLAR SYSTEM

72
00:04:29,267 --> 00:04:33,433
4 1/2 BILLION YEARS AGO.

73
00:04:37,933 --> 00:04:43,067
THEY WERE MADE BY THE SAME FORCE
THAT CREATED THE SOLAR SYSTEM --

74
00:04:43,067 --> 00:04:46,067
GRAVITY.

75
00:04:46,067 --> 00:04:48,900
IT BEGAN
IN A MAELSTROM OF CHAOS.

76
00:04:51,300 --> 00:04:54,300
A GIANT CLOUD OF GAS AND DUST

77
00:04:54,300 --> 00:04:58,067
COLLAPSED TO FORM
A WHIRLING DISC.

78
00:04:58,067 --> 00:05:01,167
CLOSE TO THE SUN,
IT WAS BURNING HOT.

79
00:05:03,767 --> 00:05:05,533
BUT FURTHER OUT,

80
00:05:05,533 --> 00:05:09,067
IT WAS COOL ENOUGH FOR GAS
CLOUDS TO CONDENSE AND FREEZE.

81
00:05:10,933 --> 00:05:14,833
ICE CRYSTALS FUSED
WITH GRAINS OF DUST.

82
00:05:16,933 --> 00:05:21,367
THEY SLOWLY PULL TOGETHER
INTO LARGER AND LARGER MASSES.

83
00:05:23,433 --> 00:05:25,433
OVER TIME,
THESE SORT OF SNOWBALLED,

84
00:05:25,433 --> 00:05:26,900
LIKE A SNOWBALL
ROLLING DOWNHILL,

85
00:05:26,900 --> 00:05:29,067
PICKING UP MORE AND MORE
AND MORE MATERIAL.

86
00:05:31,567 --> 00:05:34,800
Narrator: EVENTUALLY,
THEY FORMED GAS GIANTS

87
00:05:34,800 --> 00:05:38,067
LIKE JUPITER AND SATURN.

88
00:05:38,067 --> 00:05:43,067
BUT NOT ALL THE DEBRIS IN
THE DISK TURNED INTO PLANETS.

89
00:05:43,067 --> 00:05:48,733
TRILLIONS OF LUMPS OF DIRTY ICE
WERE LEFT BEHIND -- THE COMETS.

90
00:05:48,733 --> 00:05:51,800
YOU COULD ALMOST THINK OF COMETS
AS SORT OF THE FROZEN LEFTOVERS

91
00:05:51,800 --> 00:05:53,733
OF THE FORMATION
OF THE SOLAR SYSTEM.

92
00:05:53,733 --> 00:05:58,433
Narrator: THEY'RE ALMOST
UNCHANGED TO THIS DAY.

93
00:05:58,433 --> 00:06:00,500
THEY'RE PRISTINE TIME CAPSULES,

94
00:06:00,500 --> 00:06:03,667
AND IF YOU COULD CRACK ONE OPEN
AND SEE WHAT WAS INSIDE,

95
00:06:03,667 --> 00:06:05,067
YOU COULD LITERALLY SEE

96
00:06:05,067 --> 00:06:07,600
WHAT THE SOLAR SYSTEM
WAS FIRST MADE OUT OF.

97
00:06:07,600 --> 00:06:08,700
THAT'S REMARKABLE.

98
00:06:08,700 --> 00:06:12,067
Narrator:
BUT THE COMETS DID NOT STAY PUT.

99
00:06:12,067 --> 00:06:15,067
SEVERAL HUNDRED MILLION
YEARS LATER,

100
00:06:15,067 --> 00:06:20,433
THE SOLAR SYSTEM PLUNGED
INTO TURMOIL ONCE AGAIN.

101
00:06:20,433 --> 00:06:25,067
ENCOUNTERS WITH DEBRIS PULLED
THE GAS GIANTS OUT OF POSITION.

102
00:06:25,067 --> 00:06:27,267
THE GIANTS' IMMENSE GRAVITY

103
00:06:27,267 --> 00:06:30,467
THEN HURLED COMETS
IN EVERY DIRECTION,

104
00:06:30,467 --> 00:06:33,233
FLINGING TRILLIONS OF TONS
OF MATERIAL

105
00:06:33,233 --> 00:06:35,633
FROM THE DAWN
OF THE SOLAR SYSTEM

106
00:06:35,633 --> 00:06:38,267
INTO THE COLD
OUTER REACHES OF SPACE.

107
00:06:40,533 --> 00:06:43,333
SOME COMETS SETTLED IN A REGION

108
00:06:43,333 --> 00:06:46,767
4,000 MILLION MILES
FROM THE SUN --

109
00:06:46,767 --> 00:06:48,433
THE KUIPER BELT.

110
00:06:48,433 --> 00:06:52,433
BUT MOST WERE TOSSED
EVEN FARTHER OUT

111
00:06:52,433 --> 00:06:57,400
TO FORM A GIANT SPHERE
AROUND THE ENTIRE SOLAR SYSTEM.

112
00:06:59,567 --> 00:07:03,067
WE CALL IT THE OORT CLOUD.

113
00:07:05,133 --> 00:07:07,200
THIS IS A REGION
OF OUR SOLAR SYSTEM

114
00:07:07,200 --> 00:07:09,133
THAT'S FARTHEST AWAY
FROM THE SUN.

115
00:07:09,133 --> 00:07:11,967
THE SUN IS JUST A TINY
LITTLE DOT, ONE OF MANY STARS.

116
00:07:11,967 --> 00:07:15,700
AND THE WHOLE AREA OF SPACE
AROUND YOU IS VIRTUALLY EMPTY.

117
00:07:15,700 --> 00:07:18,133
THERE'S NOTHING THERE --
VERY LITTLE.

118
00:07:18,133 --> 00:07:20,967
AND JUST OCCASIONALLY,
YOU'LL FIND THE ODD COMET

119
00:07:20,967 --> 00:07:23,200
FLOATING OUT THERE
IN DEEP FREEZE --

120
00:07:23,200 --> 00:07:25,067
COLD, DARK, AND VERY MUCH ALONE.

121
00:07:29,400 --> 00:07:31,867
Narrator:
IN THIS REMOTE ICE CLOUD,

122
00:07:31,867 --> 00:07:34,533
THERE ARE MORE
THAN A TRILLION COMETS.

123
00:07:34,533 --> 00:07:38,900
THEY CAN TAKE MILLIONS OF YEARS
TO ORBIT THE SUN.

124
00:07:38,900 --> 00:07:41,267
BUT THEY DON'T ALWAYS STAY HERE.

125
00:07:41,267 --> 00:07:46,400
THE ORBIT OF EVERY COMET IS A
DELICATE GRAVITATIONAL BALANCE.

126
00:07:46,400 --> 00:07:49,800
THE SMALLEST NUDGE
CAN TIP THE SCALE.

127
00:07:51,267 --> 00:07:54,067
MOST COMETS
SPEND THEIR ENTIRE LIFE-SPAN

128
00:07:54,067 --> 00:07:56,067
BILLIONS OF MILES FROM THE SUN

129
00:07:56,067 --> 00:07:57,333
MOTIONLESS, INERT,

130
00:07:57,333 --> 00:08:00,100
SIMPLY WAITING
FOR SOMETHING TO HAPPEN.

131
00:08:00,100 --> 00:08:03,333
BUT THEN, PERHAPS,
A RANDOM COLLISION TAKES PLACE.

132
00:08:03,333 --> 00:08:05,633
PERHAPS A PASSING STAR
NUDGES IT,

133
00:08:05,633 --> 00:08:08,533
AND THEN THE GRAVITATIONAL
FORCE OF THE SUN

134
00:08:08,533 --> 00:08:11,800
INEVITABLY PULLS IT TOWARD
THE INNER SOLAR SYSTEM.

135
00:08:20,400 --> 00:08:23,800
Narrator: GRAVITY, THE FORCE
THAT CREATED THE COMETS,

136
00:08:23,800 --> 00:08:26,967
THEN FLUNG THEM
TO THE EDGE OF THE SOLAR SYSTEM,

137
00:08:26,967 --> 00:08:30,600
NOW PULLS THEM BACK IN.

138
00:08:30,600 --> 00:08:34,100
OUR COMET BEGINS
ITS EPIC ODYSSEY

139
00:08:34,100 --> 00:08:38,900
TO SPREAD LIFE OR DEATH
ACROSS THE SOLAR SYSTEM.

140
00:08:48,567 --> 00:08:51,867
Narrator: MORE THAN A TRILLION
COMETS CIRCLE THE SUN

141
00:08:51,867 --> 00:08:55,367
AT THE FROZEN EDGES
OF OUR SOLAR SYSTEM.

142
00:08:55,367 --> 00:08:58,233
BUT MANY DO NOT STAY HERE.

143
00:08:58,233 --> 00:09:01,267
THE SMALLEST
GRAVITATIONAL DISRUPTION

144
00:09:01,267 --> 00:09:04,067
CAN KNOCK THEM
OUT OF THEIR ORBIT.

145
00:09:04,067 --> 00:09:06,067
IT COULD BE
A NEARBY STAR GOING BY.

146
00:09:06,067 --> 00:09:09,167
IT COULD BE US GOING THROUGH
A DENSER PART OF THE GALAXY.

147
00:09:09,167 --> 00:09:10,367
ANYTHING THAT JUST GIVES

148
00:09:10,367 --> 00:09:12,300
A LITTLE GRAVITATIONAL HIT
TO A COMET

149
00:09:12,300 --> 00:09:14,133
CAN CAUSE IT
TO FALL IN TOWARDS US.

150
00:09:14,133 --> 00:09:18,167
Narrator:
OUR COMET HAS BEEN DISTURBED.

151
00:09:18,167 --> 00:09:22,167
NOW THE SUN'S IMMENSE GRAVITY
TAKES OVER.

152
00:09:25,833 --> 00:09:28,367
YOU COULD THINK OF THE GRAVITY
OF OUR SOLAR SYSTEM

153
00:09:28,367 --> 00:09:29,667
SORT OF LIKE BEING A HILLSIDE.

154
00:09:29,667 --> 00:09:31,067
AT THE BOTTOM, THERE'S THE SUN.

155
00:09:31,067 --> 00:09:33,267
AND COMETS ARE WAY
AT THE TOP OF THAT HILL.

156
00:09:33,267 --> 00:09:36,267
WHEN THEY GET DISLODGED, THERE'S
ONLY ONE WAY FOR THEM TO GO.

157
00:09:36,267 --> 00:09:38,433
THEY HAVE TO FALL DOWN IN
TOWARDS THE SUN.

158
00:09:40,733 --> 00:09:43,900
Narrator: OUR COMET
ACCELERATES TOWARDS THE SUN,

159
00:09:43,900 --> 00:09:46,367
BUT ITS PATH
IS FAR FROM STRAIGHT.

160
00:09:48,333 --> 00:09:52,200
GRAVITY FROM THE PLANETS
CAN THROW COMETS OFF COURSE

161
00:09:52,200 --> 00:09:55,733
OR OUT OF THE SOLAR SYSTEM
COMPLETELY.

162
00:09:55,733 --> 00:09:58,433
IF THEY ESCAPE THESE OBSTACLES,

163
00:09:58,433 --> 00:10:01,800
COMETS CONTINUE THEIR JOURNEY
TOWARD THE SUN.

164
00:10:01,800 --> 00:10:05,867
NOW THEY BEGIN ONE OF THE MOST
REMARKABLE TRANSFORMATIONS

165
00:10:05,867 --> 00:10:08,967
KNOWN TO SCIENCE.

166
00:10:08,967 --> 00:10:11,067
Dr. Thaller:
A CHRYSALIS TO A BUTTERFLY.

167
00:10:11,067 --> 00:10:12,933
THEY BECOME
THE MOST SPECTACULAR THINGS

168
00:10:12,933 --> 00:10:14,133
THE UNIVERSE HAS TO OFFER.

169
00:10:16,600 --> 00:10:21,267
Narrator: AS IT PASSES JUPITER,
OUR COMET BEGINS TO CHANGE.

170
00:10:24,100 --> 00:10:26,500
AS IT STARTS TO MOVE
A LITTLE BIT FASTER

171
00:10:26,500 --> 00:10:29,033
AND STARTS GETTING CLOSER
AND CLOSER TO THE SUN

172
00:10:29,033 --> 00:10:31,367
AND IT STARTS FEELING
THE HEAT OF THE SUN,

173
00:10:31,367 --> 00:10:34,300
THAT'S WHEN THINGS
REALLY START TO CHANGE.

174
00:10:39,900 --> 00:10:42,767
Narrator:
500 MILLION MILES FROM THE SUN,

175
00:10:42,767 --> 00:10:45,667
HEAT BRINGS OUR COMET TO LIFE.

176
00:10:45,667 --> 00:10:48,667
FROZEN GASES START TO VAPORIZE.

177
00:10:48,667 --> 00:10:52,867
GRAINS OF ICE AND DUST
RISE FROM THE SURFACE.

178
00:10:55,200 --> 00:10:57,767
AS THE COMET
CONTINUES TO APPROACH THE SUN

179
00:10:57,767 --> 00:10:58,833
AND GETS WARMER,

180
00:10:58,833 --> 00:11:00,667
MORE AND MORE GAS IS RELEASED.

181
00:11:00,667 --> 00:11:02,500
THE COMET BECOMES A FUZZY BALL.

182
00:11:02,500 --> 00:11:05,500
THERE'S A SOLID PART IN THERE,
BUT IT'S SURROUNDED

183
00:11:05,500 --> 00:11:08,167
BY A MUCH LARGER
SORT OF CLOUD OF MATERIAL.

184
00:11:08,167 --> 00:11:11,433
Narrator:
THIS CLOUD OF DUST AND GAS

185
00:11:11,433 --> 00:11:16,300
FORMS AN ATMOSPHERE,
OR COMA, AROUND THE COMET.

186
00:11:16,300 --> 00:11:20,167
AND IT ALSO CREATES
THE COMET'S HUGE TAIL.

187
00:11:20,167 --> 00:11:22,967
IT'S ALL DRIVEN BY THE SUN,

188
00:11:22,967 --> 00:11:26,367
AND IT'S NOT OVER YET.

189
00:11:26,367 --> 00:11:28,633
Dr. Thaller: THERE'S SOMETHING
CALLED THE SOLAR WIND.

190
00:11:28,633 --> 00:11:31,267
IT'S ACTUALLY A HUGE WAVE
OF CHARGED PARTICLES

191
00:11:31,267 --> 00:11:32,700
ORIGINATING FROM THE SUN.

192
00:11:32,700 --> 00:11:34,233
THIS FILLS OUR SOLAR SYSTEM,

193
00:11:34,233 --> 00:11:36,933
AND AS A COMET BEGINS TO MOVE
FURTHER AND FURTHER

194
00:11:36,933 --> 00:11:38,067
IN TOWARDS THE SUN,

195
00:11:38,067 --> 00:11:39,633
THE SOLAR WIND GETS STRONGER.

196
00:11:39,633 --> 00:11:42,700
Narrator:
LIKE A COSMIC HURRICANE,

197
00:11:42,700 --> 00:11:45,733
THE SOLAR WIND BLASTS
GAS MOLECULES

198
00:11:45,733 --> 00:11:48,167
FROM OUR COMET OUT INTO SPACE.

199
00:11:50,733 --> 00:11:53,833
THEY FORM A SECOND GIANT TAIL.

200
00:11:59,067 --> 00:12:00,333
THE SOLID PART OF THE COMET

201
00:12:00,333 --> 00:12:02,067
MIGHT ONLY BE
A FEW MILES ACROSS,

202
00:12:02,067 --> 00:12:03,533
AND THE FUZZY PART MIGHT BE

203
00:12:03,533 --> 00:12:06,500
A FEW THOUSAND OR TENS
OF THOUSANDS OF MILES ACROSS.

204
00:12:06,500 --> 00:12:08,100
THE TAIL THAT GETS SWEPT BACK

205
00:12:08,100 --> 00:12:10,733
AS THAT MATERIAL IS BLOWN OFF
BY THE SOLAR WIND

206
00:12:10,733 --> 00:12:13,533
CAN BE MILLIONS OR
TENS OF MILLIONS OF MILES LONG.

207
00:12:15,867 --> 00:12:21,067
Narrator: OUR COMET HURTLES THROUGH
SPACE AT 50,000 MILES AN HOUR.

208
00:12:21,067 --> 00:12:25,500
IT'S ABOUT TO ENTER THE MOST
VIOLENT PHASE OF ITS JOURNEY.

209
00:12:25,500 --> 00:12:27,633
200 MILLION MILES FROM THE SUN,

210
00:12:27,633 --> 00:12:32,067
WATER ICE BEGINS TO VAPORIZE.

211
00:12:32,067 --> 00:12:34,133
THE GROUND WOULD START
TO SHIFT AND QUAKE,

212
00:12:34,133 --> 00:12:37,400
AND AS THE MATERIAL BENEATH
MY FEET IS LITERALLY THAWING,

213
00:12:37,400 --> 00:12:39,933
WE'D HAVE GREAT BIG JETS
OF CARBON DIOXIDE

214
00:12:39,933 --> 00:12:42,100
AND WATER ICE
STARTING TO COME OUT,

215
00:12:42,100 --> 00:12:44,567
AND THAT WOULD NOT BE A VERY
GOOD PLACE TO BE STANDING.

216
00:12:44,567 --> 00:12:48,200
Narrator:
THE SURFACE CRACKS OPEN.

217
00:12:48,200 --> 00:12:50,233
GASES EXPLODE.

218
00:12:50,233 --> 00:12:55,067
DEBRIS FIRES IN ALL DIRECTIONS.

219
00:12:55,067 --> 00:12:57,533
THE FORCE OF THESE ERUPTIONS

220
00:12:57,533 --> 00:13:00,933
MAKES THE COMET TUMBLE
ERRATICALLY.

221
00:13:00,933 --> 00:13:02,400
EVERY JET THAT TURNS ON

222
00:13:02,400 --> 00:13:05,133
IS LITERALLY LIKE A LITTLE JET
ENGINE ATTACHED TO THE COMET.

223
00:13:07,667 --> 00:13:10,067
Narrator:
LIKE A DRAGSTER ON A RACETRACK,

224
00:13:10,067 --> 00:13:12,867
OUR COMET EXPLODES TO LIFE.

225
00:13:12,867 --> 00:13:14,667
[ ENGINE REVS ]

226
00:13:22,200 --> 00:13:23,967
INCREDIBLE SPEED,

227
00:13:23,967 --> 00:13:28,733
IRRESISTIBLE ENERGY,
AND A VAST PLUME OF DEBRIS.

228
00:13:28,733 --> 00:13:34,067
OUR COMET TRANSFORMS
INTO A COSMIC HOT ROD,

229
00:13:34,067 --> 00:13:38,133
BUT SPEED AND ENERGY
ARE A VOLATILE MIX.

230
00:13:38,133 --> 00:13:42,467
OUR COMET COULD BLOW APART
AT ANY MOMENT.

231
00:13:51,767 --> 00:13:55,367
THE CLOUD AROUND OUR COMET
IS NOW BIGGER THAN JUPITER.

232
00:13:55,367 --> 00:14:00,467
ITS TAIL STRETCHES
FOR 100 MILLION MILES.

233
00:14:03,067 --> 00:14:08,633
AN OBJECT 4.5 BILLION YEARS OLD
EMERGES FROM THE DARK.

234
00:14:11,100 --> 00:14:14,300
EVERY ARRIVAL OF A NEW COMET IS
LIKE A GIFT FROM THE UNIVERSE.

235
00:14:14,300 --> 00:14:17,400
WE'VE NEVER SEEN THIS LITTLE BIT
OF THE SOLAR SYSTEM BEFORE,

236
00:14:17,400 --> 00:14:20,167
THIS LITTLE BUILDING BLOCK,
THIS LITTLE BABY PICTURE.

237
00:14:20,167 --> 00:14:21,567
IT'S COMPLETELY NEW TO US.

238
00:14:23,467 --> 00:14:27,767
Narrator: IT'S A CHANCE TO STUDY
THE ORIGIN OF OUR SOLAR SYSTEM,

239
00:14:27,767 --> 00:14:31,567
AND WHAT WE'RE LEARNING
IS A REVELATION.

240
00:14:33,367 --> 00:14:39,567
COMETS ARE FAR MORE HOSTILE
AND ALIEN THAN WE IMAGINED.

241
00:14:50,233 --> 00:14:52,800
Narrator:
WITH MODERN TELESCOPES,

242
00:14:52,800 --> 00:14:56,500
WE CAN STUDY COMETS
IN MORE DETAIL THAN EVER BEFORE.

243
00:14:56,500 --> 00:14:59,200
BUT TO REALLY UNDERSTAND THEM,

244
00:14:59,200 --> 00:15:03,300
WE NEED TO GET CLOSE
TO THE VERY HEART OF A COMET --

245
00:15:03,300 --> 00:15:06,067
ITS NUCLEUS.

246
00:15:06,067 --> 00:15:09,533
ONE OF THE HOLY GRAILS OF COMET
SCIENCE IS TO REALLY UNDERSTAND

247
00:15:09,533 --> 00:15:11,067
WHAT IS IN A COMET'S NUCLEUS.

248
00:15:11,067 --> 00:15:12,567
WHAT IS ACTUALLY ON THE SURFACE?

249
00:15:12,567 --> 00:15:14,367
WHAT IS
THE CHEMICAL COMPOSITION?

250
00:15:14,367 --> 00:15:17,400
WHAT ARE THE CHARACTERISTICS OF
THE ROCKS AND THE MATERIALS --

251
00:15:17,400 --> 00:15:19,433
THE VOLATILES
THAT ARE ON THAT SURFACE?

252
00:15:24,267 --> 00:15:26,567
THE NUCLEUS IS
THE FUNDAMENTAL BUILDING BLOCK

253
00:15:26,567 --> 00:15:27,900
OF THE SOLAR SYSTEM

254
00:15:27,900 --> 00:15:30,100
THAT WE, AS SCIENTISTS,
REALLY WANT TO INVESTIGATE.

255
00:15:30,100 --> 00:15:32,100
THAT'S WHERE
THE MYSTERIES REALLY ARE.

256
00:15:32,100 --> 00:15:36,600
Narrator: THERE HAVE BEEN MORE
THAN A DOZEN MISSIONS TO COMETS

257
00:15:36,600 --> 00:15:38,600
IN THE PAST THREE DECADES.

258
00:15:38,600 --> 00:15:41,800
EVERY ONE OF THEM
HAS BEEN A REVELATION.

259
00:15:43,567 --> 00:15:44,833
WE'VE LEARNED
ABOUT THE CHEMISTRY OF THEM.

260
00:15:44,833 --> 00:15:45,967
WE'VE LEARNED ABOUT

261
00:15:45,967 --> 00:15:47,967
THE PHYSICAL INTERACTION
THEY HAVE WITH THE SUN.

262
00:15:47,967 --> 00:15:50,567
WE'VE LEARNED ABOUT THEIR
PHYSICAL SURFACE, THEIR TERRAIN,

263
00:15:50,567 --> 00:15:52,067
AND HOW THEY'RE DIFFERENT,

264
00:15:52,067 --> 00:15:54,433
EVEN IF YOU WERE TO GO FROM
ONE SPOT ON A COMET TO ANOTHER.

265
00:15:54,433 --> 00:15:55,600
SO, WE'RE REALLY LEARNING

266
00:15:55,600 --> 00:15:57,667
THAT THESE THINGS
ARE WORLDS UNTO THEMSELVES.

267
00:16:01,533 --> 00:16:04,533
Narrator: SCIENTISTS THOUGHT
COMETS WERE WHITE LIKE A SNOWBALL.

268
00:16:09,633 --> 00:16:14,200
THAT CHANGED IN 1986,
WHEN THE GIOTTO SPACE PROBE

269
00:16:14,200 --> 00:16:18,233
BEAMED BACK
THESE IMAGES OF HALLEY'S COMET.

270
00:16:21,400 --> 00:16:23,600
FOR THE FIRST TIME IN HISTORY,

271
00:16:23,600 --> 00:16:27,367
WE HAD A SNAPSHOT OF
THE VERY CENTER OF THAT COMET,

272
00:16:27,367 --> 00:16:30,600
THAT COMET THAT ENTERED
HUMAN HISTORY ON MANY OCCASIONS,

273
00:16:30,600 --> 00:16:32,700
AND WE FOUND A COLD, DEAD WORLD.

274
00:16:32,700 --> 00:16:35,500
WE FOUND AN OBJECT
SHAPED LIKE A PEANUT.

275
00:16:38,900 --> 00:16:41,467
Narrator:
HALLEY WAS NO SNOWBALL.

276
00:16:41,467 --> 00:16:44,933
A THICK LAYER OF BLACK DUST
COVERED ITS SURFACE.

277
00:16:44,933 --> 00:16:48,067
THERE WERE PITS AND HILLS,

278
00:16:48,067 --> 00:16:51,867
AND HALLEY WAS 9 MILES LONG,

279
00:16:51,867 --> 00:16:54,767
FAR BIGGER THAN ANYONE EXPECTED.

280
00:16:57,667 --> 00:17:01,333
SCIENTISTS THOUGHT
THAT ALL COMETS WERE THE SAME.

281
00:17:01,333 --> 00:17:03,333
THEY WERE WRONG.

282
00:17:03,333 --> 00:17:08,600
IN 2004, THE STARDUST PROBE FLEW
INTO THE TAIL

283
00:17:08,600 --> 00:17:12,367
OF COMET WILD 2

284
00:17:12,367 --> 00:17:16,400
AND CAPTURED THOUSANDS
OF TINY DUST PARTICLES.

285
00:17:16,400 --> 00:17:20,367
WHEN STARDUST BROUGHT
THOSE SAMPLES BACK ON EARTH,

286
00:17:20,367 --> 00:17:23,167
WE REALIZED THAT, IN FACT,
EVERY COMET IS A UNIQUE OBJECT.

287
00:17:23,167 --> 00:17:25,067
JUST LIKE
EVERY PLANET IS DIFFERENT,

288
00:17:25,067 --> 00:17:27,067
IT LOOKS LIKE
EVERY COMET IS DIFFERENT.

289
00:17:27,067 --> 00:17:28,567
IT HAS ITS OWN HISTORY TO TELL.

290
00:17:28,567 --> 00:17:30,800
DIFFERENT MATERIALS
WENT INTO ITS FORMATION.

291
00:17:30,800 --> 00:17:33,467
DIFFERENT HEAT SOURCES
WERE INJECTED INTO ITS INTERIOR.

292
00:17:33,467 --> 00:17:36,433
DIFFERENT CHEMICAL PROCESSES
AND GEOLOGIC PROCESSES OCCURRED.

293
00:17:36,433 --> 00:17:38,933
EACH ONE IS A UNIQUE WORLD
WAITING TO BE EXPLORED.

294
00:17:41,667 --> 00:17:45,267
Narrator:
SOME COMETS ARE TRULY STRANGE.

295
00:17:48,933 --> 00:17:52,200
THESE ARE REAL IMAGES
OF HARTLEY 2,

296
00:17:52,200 --> 00:17:55,533
A COMET SO WEIRD,

297
00:17:55,533 --> 00:17:58,567
IT SNOWS.

298
00:17:58,567 --> 00:18:00,133
Dr. Mainzer:
IT'S SO STRANGE.

299
00:18:00,133 --> 00:18:01,333
WE WERE ABLE TO SEE

300
00:18:01,333 --> 00:18:03,400
THAT THERE ARE GOLF-BALL-SIZED
CHUNKS OF DRY ICE

301
00:18:03,400 --> 00:18:05,200
THAT ARE FOLLOWING
THE COMET AROUND

302
00:18:05,200 --> 00:18:07,333
UP TO A MILLION MILES AWAY
FROM THE NUCLEUS.

303
00:18:07,333 --> 00:18:09,200
THIS THING
IS JUST MAKING A BIG MESS.

304
00:18:09,200 --> 00:18:10,300
[ CHUCKLES ]

305
00:18:10,300 --> 00:18:11,667
HARTLEY 2 IS JUST AMAZING!

306
00:18:11,667 --> 00:18:14,367
IT LOOKED LIKE YOU WERE
IN THE MIDDLE OF A SNOW GLOBE

307
00:18:14,367 --> 00:18:17,733
AND YOU SHOOK IT UP AND THERE
WERE ALL THESE LITTLE THINGS,

308
00:18:17,733 --> 00:18:20,167
KIND OF LIKE FLIES
BUZZING AROUND FOOD,

309
00:18:20,167 --> 00:18:22,333
JUST KIND OF FLOATING OUT THERE.

310
00:18:22,333 --> 00:18:23,667
THAT'S JUST NOT RIGHT.

311
00:18:26,100 --> 00:18:29,933
Narrator: HARTLEY 2
IS A HYPERACTIVE COMET.

312
00:18:29,933 --> 00:18:33,300
IT TUMBLES FASTER
AND SPITS OUT MORE DEBRIS

313
00:18:33,300 --> 00:18:35,500
THAN MOST OTHERS ITS SIZE.

314
00:18:37,833 --> 00:18:40,167
COMETS ARE ALIEN WORLDS.

315
00:18:41,967 --> 00:18:43,833
ON COMET TEMPEL 1,

316
00:18:43,833 --> 00:18:48,600
THERE ARE SMOOTH PLATEAUS...

317
00:18:48,600 --> 00:18:52,367
CRATERS,
AND CLIFFS 60 FEET HIGH,

318
00:18:52,367 --> 00:18:55,833
LAYERS OF ROCK
LIE ON TOP OF EACH OTHER

319
00:18:55,833 --> 00:18:57,633
LIKE A STACK OF PANCAKES.

320
00:19:00,400 --> 00:19:04,533
EACH COMET SEEMS TO HAVE
ITS OWN UNIQUE HISTORY.

321
00:19:06,700 --> 00:19:12,167
TEMPEL 1 GAVE SCIENTISTS
THEIR BIGGEST BREAKTHROUGH.

322
00:19:12,167 --> 00:19:16,267
IN 2005,
THE DEEP IMPACT SPACE PROBE

323
00:19:16,267 --> 00:19:19,900
SLAMMED A PROJECTILE
INTO ITS SURFACE.

324
00:19:19,900 --> 00:19:23,533
THE EXPLOSION DUG OUT A CRATER

325
00:19:23,533 --> 00:19:26,400
150 YARDS ACROSS.

326
00:19:26,400 --> 00:19:27,967
TALK ABOUT
A SPECTACULAR 4th OF JULY.

327
00:19:27,967 --> 00:19:29,667
I MEAN,
CAN YOU IMAGINE ANYTHING BETTER?

328
00:19:29,667 --> 00:19:31,167
WE ACTUALLY BLEW A HOLE
IN A COMET.

329
00:19:31,167 --> 00:19:33,367
I MEAN, THAT'S GOT TO BE
ONE OF THE MORE AMAZING THINGS

330
00:19:33,367 --> 00:19:34,367
THAT NASA HAS EVER DONE.

331
00:19:35,933 --> 00:19:37,633
Narrator:
THE MATERIAL THE IMPACT EJECTED

332
00:19:37,633 --> 00:19:41,100
ALLOWED US TO SEE
INSIDE A COMET'S NUCLEUS

333
00:19:41,100 --> 00:19:42,733
FOR THE FIRST TIME.

334
00:19:42,733 --> 00:19:45,067
Thaller:
IT WAS COMPLETELY UNEXPECTED.

335
00:19:45,067 --> 00:19:47,933
WE FOUND THINGS LIKE RUBIES
AND PERIDOT, GEMSTONES --

336
00:19:47,933 --> 00:19:51,200
TINY LITTLE THINGS
INSIDE THE COMET.

337
00:19:51,200 --> 00:19:52,933
AND WE FOUND
ALL KINDS OF ORGANIC MOLECULES,

338
00:19:52,933 --> 00:19:55,433
THE VERY SORTS OF THINGS
WE'RE MADE OF.

339
00:19:58,767 --> 00:20:01,067
Narrator:
SCIENTISTS NOW BELIEVE

340
00:20:01,067 --> 00:20:04,033
THAT COMETS PLAY A CRITICAL ROLE
IN OUR UNIVERSE.

341
00:20:07,033 --> 00:20:09,833
Kaku: WHERE DO THE INGREDIENTS
OF LIFE COME FROM?

342
00:20:09,833 --> 00:20:11,967
WHERE WERE THEY ALL MIXED
TOGETHER?

343
00:20:11,967 --> 00:20:14,467
WHERE DID ALL THIS LIQUID WATER
COME FROM?

344
00:20:14,467 --> 00:20:15,900
COMETS COULD HOLD THE KEY

345
00:20:15,900 --> 00:20:18,433
TO UNDERSTANDING
THE NATURE OF LIFE ITSELF.

346
00:20:18,433 --> 00:20:24,033
Narrator: BUT OPPORTUNITIES TO
STUDY THEM UP CLOSE ARE RARE.

347
00:20:24,033 --> 00:20:27,300
OUR COMET IS NOW MOVING
AT INCREDIBLE SPEED

348
00:20:27,300 --> 00:20:31,067
TOWARD A PLACE WHERE NO
SPACECRAFT COULD EVER SURVIVE --

349
00:20:31,067 --> 00:20:34,067
THE SUN.

350
00:20:43,667 --> 00:20:46,033
Narrator:
4 BILLION YEARS AGO,

351
00:20:46,033 --> 00:20:51,033
GRAVITY HURLED COMETS TO
THE EDGES OF OUR SOLAR SYSTEM.

352
00:20:51,033 --> 00:20:54,633
THE SAME FORCE
CAN PULL THEM BACK IN.

353
00:20:54,633 --> 00:20:57,000
OUR COMET PASSES EARTH

354
00:20:57,000 --> 00:21:02,100
AND ENTERS THE MOST VIOLENT
STAGE OF ITS JOURNEY.

355
00:21:02,100 --> 00:21:08,200
IT ROCKETS TOWARD THE SUN
AT 100,000 MILES PER HOUR.

356
00:21:10,700 --> 00:21:13,133
THE SURFACE OF THE COMET
IS NOW SIZZLING,

357
00:21:13,133 --> 00:21:14,500
SIZZLING WITH ACTIVITY.

358
00:21:14,500 --> 00:21:17,067
BLISTERING TEMPERATURES
ARE BEING CREATED.

359
00:21:17,067 --> 00:21:19,700
ENORMOUS GEYSERS
OF ICE CRYSTALS AND GAS

360
00:21:19,700 --> 00:21:21,467
BEING SHOT OFF THE SURFACE.

361
00:21:21,467 --> 00:21:24,100
JETS ARE ERUPTING ALL OVER
THE PLACE, IT'S TUMBLING,

362
00:21:24,100 --> 00:21:25,900
THE ROTATIONAL STATE
IS CHANGING,

363
00:21:25,900 --> 00:21:29,067
AND THE VERY SURFACE IS KIND OF
CRACKING UP UNDERNEATH OUR FEET.

364
00:21:31,833 --> 00:21:33,833
Narrator: INSIDE THE COMET,

365
00:21:33,833 --> 00:21:38,767
POCKETS OF GAS EXPLODE
AND FLING HUGE ROCKS INTO SPACE.

366
00:21:38,767 --> 00:21:40,333
Dr. Mainzer: IT'S LOSING MASS.

367
00:21:40,333 --> 00:21:41,500
IT'S SHRINKING.

368
00:21:41,500 --> 00:21:43,067
AND AS WE GET CLOSER AND CLOSER
TO THE SUN

369
00:21:43,067 --> 00:21:44,733
AND MORE AND MORE
OF THE VOLATILES

370
00:21:44,733 --> 00:21:46,633
ARE STARTING TO COME OFF
OF ITS SURFACE,

371
00:21:46,633 --> 00:21:49,067
THIS CAN ACTUALLY CHANGE THE
ROTATIONAL STATE OF THE COMET.

372
00:21:49,067 --> 00:21:50,200
IT CAN MAKE IT TUMBLE.

373
00:21:50,200 --> 00:21:51,767
IT CAN ACTUALLY EVEN PUSH IT
IN ITS ORBIT.

374
00:21:51,767 --> 00:21:53,700
IT CAN ACTUALLY CHANGE THE ORBIT
OF THE COMET.

375
00:21:53,700 --> 00:21:59,133
Narrator: COMETS CAN SHED 50 TONS
OF ICE AND GAS EVERY SECOND.

376
00:21:59,133 --> 00:22:03,667
ENORMOUS PRESSURES BUILD UP
INSIDE THE NUCLEUS.

377
00:22:03,667 --> 00:22:05,467
Kaku:
IT COULD BECOME UNSTABLE.

378
00:22:05,467 --> 00:22:09,067
IT COULD EVEN BREAK APART
INTO PIECES AT ANY TIME.

379
00:22:09,067 --> 00:22:14,167
Narrator: AS COMETS REACH
THEIR CLOSEST POINT TO THE SUN,

380
00:22:14,167 --> 00:22:17,400
THEIR EXISTENCE
IS ON A KNIFE EDGE.

381
00:22:17,400 --> 00:22:20,233
MANY WILL NOT SURVIVE.

382
00:22:21,600 --> 00:22:24,333
WE'VE BEEN ABLE TO ACTUALLY SEE
IMAGES OF COMETS

383
00:22:24,333 --> 00:22:26,400
JUST GETTING
SWALLOWED UP BY THE SUN,

384
00:22:26,400 --> 00:22:29,100
AND YOU CAN ACTUALLY SEE THEM
JUST PELTING IN THERE.

385
00:22:29,100 --> 00:22:30,333
AND THE WHOLE BODY,

386
00:22:30,333 --> 00:22:32,633
WHETHER IT'S A MILE ACROSS
OR 10 MILES ACROSS,

387
00:22:32,633 --> 00:22:34,967
JUST GETS COMPLETELY
AND UTTERLY DESTROYED.

388
00:22:37,167 --> 00:22:41,933
Narrator: A SOLAR OBSERVATORY
RECORDED THESE EXTRAORDINARY IMAGES.

389
00:22:41,933 --> 00:22:45,067
THEY SHOW SMALL COMETS
CALLED "SUN GRAZERS"

390
00:22:45,067 --> 00:22:46,767
DIVING TOWARDS THE SUN.

391
00:22:49,067 --> 00:22:51,067
[ DRAMATIC MUSIC PLAYS ]

392
00:22:51,067 --> 00:22:54,333
HERE THEY'RE EXPOSED
TO IMMENSE GRAVITY

393
00:22:54,333 --> 00:22:58,233
AND TORCHED BY
THE FEROCIOUS HEAT OF THE SUN.

394
00:23:04,700 --> 00:23:07,233
MANY ARE VAPORIZED.

395
00:23:14,767 --> 00:23:16,200
EVEN IN DEEP SPACE,

396
00:23:16,200 --> 00:23:20,067
VAST EXPLOSIONS
CAN TEAR COMETS APART.

397
00:23:22,300 --> 00:23:26,967
IN 2007, COMET HOLMES WAS
HEADING AWAY FROM THE SUN

398
00:23:26,967 --> 00:23:29,300
WHEN SOMETHING EXTRAORDINARY
HAPPENED.

399
00:23:29,300 --> 00:23:34,533
IN LESS THAN A DAY, IT GREW
HALF A MILLION TIMES BRIGHTER.

400
00:23:34,533 --> 00:23:38,933
THE CLOUD AROUND IT
BALLOONED INTO SPACE.

401
00:23:38,933 --> 00:23:41,833
IT'S ACTUALLY RELATIVELY
COMMON FOR A COMA --

402
00:23:41,833 --> 00:23:43,800
THE FUZZY PART AROUND A COMET --

403
00:23:43,800 --> 00:23:46,900
TO EXPAND LARGE ENOUGH
TO BE BIGGER THAN JUPITER,

404
00:23:46,900 --> 00:23:48,300
100,000 MILES ACROSS.

405
00:23:48,300 --> 00:23:51,300
BUT THAT CAN TAKE DAYS AND WEEKS
AND MONTHS TO BUILD UP.

406
00:23:51,300 --> 00:23:53,967
TO HAVE A SINGLE EVENT,
SOMETHING THAT HAPPENED,

407
00:23:53,967 --> 00:23:56,067
BOOM, ALL AT ONCE,
SOME CATASTROPHE

408
00:23:56,067 --> 00:23:59,067
TO CREATE THIS SHELL
AROUND COMET HOLMES

409
00:23:59,067 --> 00:24:02,767
THAT COULD BE BIGGER
THAN JUPITER IS AMAZING TO ME.

410
00:24:02,767 --> 00:24:05,833
WE HAD NEVER SEEN
SOMETHING LIKE THIS BEFORE.

411
00:24:05,833 --> 00:24:07,833
IN FACT, THE COMA OF THE COMET

412
00:24:07,833 --> 00:24:10,600
WAS ACTUALLY LARGER
THAN THE SUN ITSELF.

413
00:24:10,600 --> 00:24:13,133
BRIEFLY,
IT WAS THE LARGEST OBJECT

414
00:24:13,133 --> 00:24:15,067
IN THE ENTIRE SOLAR SYSTEM,

415
00:24:15,067 --> 00:24:17,533
SOMETHING
THAT WAS UNPRECEDENTED.

416
00:24:20,633 --> 00:24:25,367
Narrator: WITHOUT WARNING,
COMET HOLMES BLEW APART --

417
00:24:25,367 --> 00:24:28,300
THE LARGEST COMETARY EXPLOSION

418
00:24:28,300 --> 00:24:32,200
EVER RECORDED.

419
00:24:32,200 --> 00:24:36,600
THE DEBRIS STRETCHED
FOR A MILLION MILES.

420
00:24:36,600 --> 00:24:40,533
WHAT CAUSED IT IS STILL UNCLEAR.

421
00:24:40,533 --> 00:24:43,333
ONE THEORY IS
THAT PERHAPS COMET HOLMES

422
00:24:43,333 --> 00:24:46,100
SLAMMED INTO AN ASTEROID
OF SOME SORT,

423
00:24:46,100 --> 00:24:49,500
CREATING THIS GIGANTIC MEGAFLARE
IN OUTER SPACE.

424
00:24:49,500 --> 00:24:53,133
ANOTHER POSSIBILITY IS
PERHAPS THE COMET WAS UNSTABLE

425
00:24:53,133 --> 00:24:55,600
AND PERHAPS
THERE WAS AN EXPLOSION

426
00:24:55,600 --> 00:24:59,467
CAUSED BY EXPANDING GAS AND
RIPPED THE ENTIRE COMET APART.

427
00:24:59,467 --> 00:25:02,100
AT THE PRESENT TIME,
WE SIMPLY DON'T KNOW.

428
00:25:04,533 --> 00:25:10,233
Narrator: THE LIFE OF ALL COMETS
HANGS BY A THREAD.

429
00:25:10,233 --> 00:25:14,967
OUR COMET SURVIVES
ITS ENCOUNTER WITH THE SUN...

430
00:25:14,967 --> 00:25:17,233
BUT IT'S PAID A PRICE.

431
00:25:17,233 --> 00:25:20,467
ITS GEOGRAPHY
HAS BEEN TOTALLY REARRANGED.

432
00:25:20,467 --> 00:25:24,667
HUGE CHUNKS, MOUNTAINTOPS'
WORTH, OF ROCK HAVE DISAPPEARED.

433
00:25:24,667 --> 00:25:28,400
AN OBJECT WHICH COULD BE
PERHAPS 10, 20 MILES ACROSS

434
00:25:28,400 --> 00:25:32,167
HAS LOST LITERALLY HUNDREDS,
PERHAPS THOUSANDS OF TONS

435
00:25:32,167 --> 00:25:34,300
OF ROCK AND ICE ON ITS JOURNEY.

436
00:25:34,300 --> 00:25:39,100
Narrator: AS OUR COMET
LEAVES THE SUN BEHIND,

437
00:25:39,100 --> 00:25:42,967
ACTIVITY ON ITS SURFACE
SUBSIDES.

438
00:25:42,967 --> 00:25:46,300
ON ITS OUTWARD JOURNEY, A COMET
GRADUALLY BEGINS TO SHUT DOWN.

439
00:25:46,300 --> 00:25:49,467
IT BECOMES COOLER, LESS ACTIVE,
THE JETS BEGIN TO TURN OFF,

440
00:25:49,467 --> 00:25:51,067
THE COMA BEGINS TO BLOW AWAY.

441
00:25:51,067 --> 00:25:54,067
AND YOU'RE LEFT WITH THIS
LITTLE BALL OF ICE AND DIRT.

442
00:25:56,067 --> 00:25:58,933
Narrator: IT RETURNS
TO THE DEPTHS OF SPACE,

443
00:25:58,933 --> 00:26:05,367
DORMANT ONCE AGAIN.

444
00:26:05,367 --> 00:26:09,900
BUT THE SUN
IS JUST ONE OF MANY CHALLENGES.

445
00:26:09,900 --> 00:26:12,767
COMETS MUST ALSO SURVIVE

446
00:26:12,767 --> 00:26:17,400
THE GRAVITATIONAL PULL
OF THE PLANETS.

447
00:26:17,400 --> 00:26:21,200
OUR GRAVITY IS WAY TOO SMALL TO
HAVE ANY EFFECT ON THIS COMET.

448
00:26:21,200 --> 00:26:23,800
BUT JUPITER
IS A VERY LARGE PLANET.

449
00:26:23,800 --> 00:26:26,667
IT HAS 300 TIMES
THE MASS OF THE EARTH.

450
00:26:26,667 --> 00:26:30,933
IF THE COMET PASSES WITHIN EVEN
A FEW MILLION MILES OF JUPITER,

451
00:26:30,933 --> 00:26:32,767
THAT CAN CHANGE ITS ORBIT.

452
00:26:35,633 --> 00:26:39,700
Narrator: THE CONSEQUENCES
CAN BE CATASTROPHIC.

453
00:26:39,700 --> 00:26:44,167
IN 1994, A COMET
CALLED SHOEMAKER-LEVY 9

454
00:26:44,167 --> 00:26:47,200
FLEW TOO CLOSE TO JUPITER.

455
00:26:47,200 --> 00:26:53,433
SCIENTISTS WATCHED THE PLANET'S
IMMENSE GRAVITY TEAR IT APART.

456
00:26:53,433 --> 00:26:57,933
THE REMAINS
HEADED STRAIGHT TOWARD JUPITER.

457
00:26:57,933 --> 00:26:59,633
Dr. Mainzer: MANY PEOPLE THOUGHT
THAT THE IMPACTS

458
00:26:59,633 --> 00:27:01,800
WOULDN'T DO ANYTHING TO JUPITER,

459
00:27:01,800 --> 00:27:03,433
THAT JUPITER WOULD JUST SORT OF
SWALLOW IT UP WITHOUT A BURP.

460
00:27:03,433 --> 00:27:04,967
AND THAT'S
NOT WHAT HAPPENED AT ALL.

461
00:27:04,967 --> 00:27:07,567
Narrator:
21 COMET FRAGMENTS

462
00:27:07,567 --> 00:27:11,667
SMASHED
INTO JUPITER'S ATMOSPHERE.

463
00:27:14,200 --> 00:27:17,167
EACH IMPACT RELEASED MORE ENERGY

464
00:27:17,167 --> 00:27:21,667
THAN ALL THE WORLD'S
NUCLEAR ARSENALS COMBINED.

465
00:27:21,667 --> 00:27:24,733
COMET SHOEMAKER-LEVY 9 WAS NOT
A PARTICULARLY MASSIVE COMET,

466
00:27:24,733 --> 00:27:26,733
AND IT WASN'T
EVEN A VERY DENSE ONE.

467
00:27:26,733 --> 00:27:29,233
IT ACTUALLY HAD THE CONSISTENCY
OF COTTON CANDY.

468
00:27:29,233 --> 00:27:32,167
YOU COULD HAVE PULLED BITS OF IT
APART WITH YOUR FINGERS.

469
00:27:32,167 --> 00:27:34,467
BUT THIS RATHER TENUOUS
LITTLE ICY CREATURE

470
00:27:34,467 --> 00:27:36,333
CREATED
UNIMAGINABLE DESTRUCTION.

471
00:27:36,333 --> 00:27:40,800
Narrator: THE IMPACTS
HURLED PLUMES OF DEBRIS

472
00:27:40,800 --> 00:27:43,367
THOUSANDS OF MILES HIGH...

473
00:27:43,367 --> 00:27:47,633
AND SCARRED JUPITER'S ATMOSPHERE
WITH DARK LESIONS.

474
00:27:49,567 --> 00:27:52,867
THE EVENT ROCKED
THE SCIENTIFIC COMMUNITY.

475
00:27:55,067 --> 00:27:57,067
TO ACTUALLY SEE IT
FOR OURSELVES,

476
00:27:57,067 --> 00:27:59,733
TO ACTUALLY SEE
THE IMMENSE DESTRUCTIVE POWER

477
00:27:59,733 --> 00:28:03,233
BY AN OBJECT THAT'S REALLY
NOT THAT MUCH BIGGER THAN A HILL

478
00:28:03,233 --> 00:28:04,933
WAS REALLY PRETTY TERRIFYING.

479
00:28:04,933 --> 00:28:06,633
EVEN THOUGH WE KNEW THE MATH,

480
00:28:06,633 --> 00:28:08,900
TO SEE IT FOR OURSELVES
WAS AMAZING.

481
00:28:08,900 --> 00:28:12,233
THE SHOEMAKER-LEVY 9 IMPACT
REALLY WOKE ASTRONOMERS UP

482
00:28:12,233 --> 00:28:14,767
TO THE FACT
THAT IMPACTS CAN HAPPEN NOW

483
00:28:14,767 --> 00:28:16,800
AND THEY CAN HAPPEN HERE.

484
00:28:16,800 --> 00:28:22,400
Narrator: IF A COMET JUST A FEW
MILES ACROSS HIT OUR PLANET,

485
00:28:22,400 --> 00:28:24,967
THE RESULT
WOULD BE CATASTROPHIC.

486
00:28:24,967 --> 00:28:27,733
TIDAL WAVES
WOULD DEVASTATE THE LAND.

487
00:28:27,733 --> 00:28:32,200
DEBRIS WOULD RAIN FROM THE SKY.

488
00:28:35,100 --> 00:28:38,933
LIFE AS WE KNOW IT WOULD END.

489
00:28:38,933 --> 00:28:43,100
YET COMET IMPACTS
CAN ALSO BE A CREATIVE FORCE.

490
00:28:45,700 --> 00:28:49,833
THEY COULD EVEN TRIGGER
THE BIRTH OF LIFE ITSELF.

491
00:29:11,500 --> 00:29:14,100
Narrator:
ACROSS THE UNIVERSE,

492
00:29:14,100 --> 00:29:16,800
COMETS CAUSE
MASSIVE DESTRUCTION.

493
00:29:19,200 --> 00:29:22,167
THEY COULD BE MOVING
50 OR MORE TIMES FASTER

494
00:29:22,167 --> 00:29:23,200
THAN A RIFLE BULLET.

495
00:29:23,200 --> 00:29:24,967
AND WE'RE TALKING
ABOUT SOMETHING

496
00:29:24,967 --> 00:29:26,133
THE SIZE OF A MOUNTAIN.

497
00:29:26,133 --> 00:29:27,567
SO, THE AMOUNT OF ENERGY

498
00:29:27,567 --> 00:29:30,067
THAT THIS THING WOULD RELEASE
UPON IMPACT IS DEVASTATING.

499
00:29:30,067 --> 00:29:34,100
Narrator: BUT THEY'RE
NOT ALWAYS DESTRUCTIVE.

500
00:29:34,100 --> 00:29:36,167
THEY HAVE ANOTHER SIDE.

501
00:29:36,167 --> 00:29:41,167
SCIENTISTS BELIEVE
THEY CAN SHAPE ENTIRE WORLDS.

502
00:29:44,300 --> 00:29:48,600
THIS IS TITAN --
THE LARGEST OF SATURN'S MOONS.

503
00:29:48,600 --> 00:29:53,767
IT'S THE ONLY MOON IN OUR SOLAR
SYSTEM WITH A THICK ATMOSPHERE.

504
00:29:53,767 --> 00:29:57,467
RIVERS AND LAKES
OF LIQUID METHANE

505
00:29:57,467 --> 00:30:02,267
COVER ITS SURFACE.

506
00:30:02,267 --> 00:30:07,900
TITAN WAS TRANSFORMED BY COMETS.

507
00:30:07,900 --> 00:30:12,767
RADAR IMAGES REVEAL A MOON
SHAPED BY A BLIZZARD OF COMETS

508
00:30:12,767 --> 00:30:16,600
THAT RAINED DOWN
OVER MILLIONS OF YEARS.

509
00:30:18,067 --> 00:30:21,500
EACH COMET
VAPORIZED WHEN IT HIT,

510
00:30:21,500 --> 00:30:25,533
RELEASING GASES
FROM INSIDE ITS NUCLEUS.

511
00:30:25,533 --> 00:30:30,133
GRADUALLY, THEY BUILT UP
A RICH ORGANIC ATMOSPHERE

512
00:30:30,133 --> 00:30:34,167
AND THIS STRANGE
LIQUID LANDSCAPE.

513
00:30:34,167 --> 00:30:39,633
COMETS TURNED A SPACE ROCK
INTO AN EARTH-LIKE WORLD.

514
00:30:39,633 --> 00:30:42,367
COMETS, IN SOME SENSE,
ARE THE ULTIMATE ENGINEERS

515
00:30:42,367 --> 00:30:43,733
OF THE SOLAR SYSTEM.

516
00:30:43,733 --> 00:30:46,600
COMETARY IMPACTS COULD GIVE US
THE CHEMICALS

517
00:30:46,600 --> 00:30:49,567
WHICH GIVE US THE ATMOSPHERE
NOT JUST OF TITAN

518
00:30:49,567 --> 00:30:52,000
BUT EVEN, PERHAPS,
THE EARTH ITSELF.

519
00:30:52,000 --> 00:30:57,733
Narrator: SO, IF COMETS HAVE THE
POWER TO RESHAPE ENTIRE WORLDS,

520
00:30:57,733 --> 00:31:02,167
WHAT PART DID THEY PLAY IN
THE HISTORY OF OUR OWN PLANET?

521
00:31:02,167 --> 00:31:03,733
TO FIND OUT,

522
00:31:03,733 --> 00:31:07,800
WE NEED TO GET CLOSER
TO A COMET THAN EVER BEFORE.

523
00:31:09,933 --> 00:31:14,733
WE NEED TO LAND ON ONE.

524
00:31:14,733 --> 00:31:19,867
IN MARCH 2004,
THE ROSETTA MISSION LAUNCHED.

525
00:31:22,233 --> 00:31:26,500
THE ROSETTA MISSION IS NAMED
AFTER THE ROSETTA STONE

526
00:31:26,500 --> 00:31:28,600
BECAUSE JUST LIKE THE STONE

527
00:31:28,600 --> 00:31:32,333
GAVE LINGUISTS THE KEYS
TO THE ANCIENT LANGUAGE,

528
00:31:32,333 --> 00:31:35,933
WE'RE HOPING THAT THE COMET
WILL GIVE US THE KEYS

529
00:31:35,933 --> 00:31:38,567
TO UNDERSTANDING
THE ANCIENT SOLAR SYSTEM.

530
00:31:38,567 --> 00:31:41,433
Narrator:
NOVEMBER 11, 2014,

531
00:31:41,433 --> 00:31:45,267
WILL BE A LANDMARK
IN SPACE EXPLORATION.

532
00:31:45,267 --> 00:31:47,400
FOR THE VERY FIRST TIME,

533
00:31:47,400 --> 00:31:52,067
A SPACECRAFT WILL TOUCH DOWN
ON THE SURFACE OF A COMET.

534
00:31:57,067 --> 00:32:00,300
PREVIOUS MISSIONS TO COMETS
WERE BASICALLY FLYBYS,

535
00:32:00,300 --> 00:32:02,967
AND THEY BASICALLY GAVE US
TANTALIZING EVIDENCE

536
00:32:02,967 --> 00:32:05,800
THAT THERE WAS A GREATER MYSTERY
YET TO BE SOLVED.

537
00:32:05,800 --> 00:32:08,067
NOW WE'RE GONNA LAND ON A COMET.

538
00:32:08,067 --> 00:32:10,533
WE'RE GONNA BE
UP CLOSE AND DIRTY

539
00:32:10,533 --> 00:32:13,967
WITH A LIVE COMET
STREAMING THROUGH OUTER SPACE,

540
00:32:13,967 --> 00:32:15,833
AND THIS IS UNPRECEDENTED.

541
00:32:19,567 --> 00:32:23,133
Narrator: ROSETTA IS
AROUND THE SIZE OF A CAR.

542
00:32:23,133 --> 00:32:28,233
IT'S FLYING THROUGH SPACE
AT 20,000 MILES PER HOUR.

543
00:32:30,500 --> 00:32:32,433
IT'S HEADING FOR THIS...

544
00:32:34,767 --> 00:32:38,233
...A COMET WITH A NUCLEUS
3 MILES WIDE

545
00:32:38,233 --> 00:32:42,133
ORBITING THE SUN
EVERY 6 1/2 YEARS.

546
00:32:46,100 --> 00:32:50,067
A ROBOTIC LANDER
WILL DROP DOWN TO THE SURFACE,

547
00:32:50,067 --> 00:32:55,500
BEGINNING THE MOST DETAILED
STUDY OF A COMET EVER ATTEMPTED.

548
00:32:57,667 --> 00:33:00,167
IT'S GOING TO LOOK AT
WHAT THE SURFACE LOOKS LIKE.

549
00:33:00,167 --> 00:33:01,467
IT'S GOING TO TAKE SAMPLES.

550
00:33:01,467 --> 00:33:03,233
IT'S GOING TO LOOK
AT THE TERRAIN.

551
00:33:03,233 --> 00:33:05,933
IT'S GOING TO BE ABLE TO
ACTUALLY PROBE INSIDE THE COMET

552
00:33:05,933 --> 00:33:08,433
AND SEE WHAT IT'S MADE OF
AND HOW IT'S PUT TOGETHER.

553
00:33:08,433 --> 00:33:11,500
WE'RE HOPEFULLY GOING TO LEARN
MORE FROM THIS MISSION

554
00:33:11,500 --> 00:33:12,733
ABOUT ONE COMET

555
00:33:12,733 --> 00:33:15,233
THAN WE HAVE ABOUT
JUST EVERYTHING WE'VE KNOWN

556
00:33:15,233 --> 00:33:16,833
ABOUT COMETS FOR CENTURIES.

557
00:33:20,900 --> 00:33:25,067
Narrator: ROSETTA SHOULD ANSWER
SOME VERY SIMPLE QUESTIONS.

558
00:33:27,633 --> 00:33:29,800
Dr. Alexander:
IS IT POROUS?

559
00:33:29,800 --> 00:33:31,267
IS IT LIKE A SPONGE?

560
00:33:31,267 --> 00:33:34,300
IS IT LIKE A BUNCH OF TUBES?

561
00:33:34,300 --> 00:33:36,867
IS IT LIKE A SNOWFLAKE,

562
00:33:36,867 --> 00:33:41,067
YOU KNOW, WITH THIS SORT OF
FAIRY-CASTLE STRUCTURE?

563
00:33:41,067 --> 00:33:43,433
THESE THINGS
WILL HELP US TO UNDERSTAND

564
00:33:43,433 --> 00:33:44,967
HOW THE HEAT FLOWS WITHIN

565
00:33:44,967 --> 00:33:47,700
AND MAYBE WHAT CAUSES
CERTAIN PORTIONS OF IT

566
00:33:47,700 --> 00:33:50,133
TO BECOME A JET
AND OTHER PORTIONS NOT.

567
00:33:50,133 --> 00:33:53,400
Narrator:
BUT THIS IS JUST THE BEGINNING.

568
00:33:53,400 --> 00:33:57,133
FOR AN ENTIRE YEAR,
ROSETTA WILL STUDY THE COMET

569
00:33:57,133 --> 00:34:00,933
ON ITS EPIC JOURNEY
'ROUND THE SUN,

570
00:34:00,933 --> 00:34:03,533
USING TECHNOLOGY SO ADVANCED,

571
00:34:03,533 --> 00:34:07,700
IT MIMICS THE FIVE HUMAN SENSES.

572
00:34:07,700 --> 00:34:11,467
Dr. Alexander: WE'VE GOT
INSTRUMENTS THAT CAN SEE.

573
00:34:11,467 --> 00:34:14,300
WE'VE GOT A KIND OF
AN ULTRASOUND EXPERIMENT,

574
00:34:14,300 --> 00:34:17,400
INSTRUMENTS THAT ARE
THE EQUIVALENT OF YOUR HANDS.

575
00:34:17,400 --> 00:34:20,600
SO, WE'D LIKE TO UNDERSTAND
EVERYTHING POSSIBLE

576
00:34:20,600 --> 00:34:23,433
ABOUT THIS COMET'S JOURNEY
AROUND THE SUN

577
00:34:23,433 --> 00:34:26,967
FROM WHEN IT'S QUIET TO
WHEN IT'S AT ITS MOST ACTIVE.

578
00:34:29,500 --> 00:34:32,067
Narrator: BUT WE'LL HAVE TO
GET THERE FIRST.

579
00:34:32,067 --> 00:34:34,400
JUST TO REACH THE COMET,

580
00:34:34,400 --> 00:34:39,233
SCIENTISTS MUST OVERCOME
ENORMOUS TECHNICAL CHALLENGES.

581
00:34:39,233 --> 00:34:43,933
ROSETTA MUST HIT A TARGET
JUST 3 MILES WIDE,

582
00:34:43,933 --> 00:34:48,933
TRAVELING
AT 34,000 MILES PER HOUR.

583
00:34:48,933 --> 00:34:52,367
LANDING ON IT
WILL BE EVEN HARDER.

584
00:34:52,367 --> 00:34:55,267
COMETS HAVE VERY LITTLE GRAVITY.

585
00:34:59,400 --> 00:35:02,700
THERE'S NOT ANYTHING THAT YOU
KNOW IS GONNA PULL YOU DOWN

586
00:35:02,700 --> 00:35:03,700
TO THE SURFACE.

587
00:35:03,700 --> 00:35:05,533
AND THERE'S NO ATMOSPHERE,

588
00:35:05,533 --> 00:35:07,700
SO YOU CAN'T UNFURL A PARACHUTE

589
00:35:07,700 --> 00:35:10,600
AND JUST SAIL DOWN
UNTIL YOU TOUCH DOWN.

590
00:35:10,600 --> 00:35:13,600
YOU'VE GOT TO FIGURE OUT A WAY

591
00:35:13,600 --> 00:35:19,667
TO GET YOUR LANDER TO ACTUALLY
RESIDE AND REST ON THE SURFACE.

592
00:35:22,467 --> 00:35:25,800
Narrator: TECHNICIANS
HAVE AN INGENIOUS SOLUTION.

593
00:35:25,800 --> 00:35:31,933
THE LANDER IS EQUIPPED WITH
SHOCK ABSORBERS AND A HARPOON.

594
00:35:31,933 --> 00:35:33,833
Dr. Alexander: WHEN IT MAKES
CONTACT WITH THE SURFACE,

595
00:35:33,833 --> 00:35:35,100
AT THE SAME TIME,

596
00:35:35,100 --> 00:35:39,333
THE HARPOON WILL BE RELEASED
DOWN INTO THE SUBSTRATE,

597
00:35:39,333 --> 00:35:41,767
AND IT WILL HAVE PRONGS
THAT WILL OPEN

598
00:35:41,767 --> 00:35:43,667
THAT WILL PREVENT IT
FROM COMING BACK UP.

599
00:35:48,767 --> 00:35:51,600
Narrator:
ROSETTA WILL ATTEMPT TO SOLVE

600
00:35:51,600 --> 00:35:54,267
SOME OF SCIENCE'S
DEEPEST MYSTERIES.

601
00:35:56,733 --> 00:35:58,300
WE WOULD VERY MUCH LIKE TO KNOW

602
00:35:58,300 --> 00:36:01,167
WHY IS IT THAT EARTH HAS
LIQUID WATER AND SO MUCH OF IT

603
00:36:01,167 --> 00:36:03,633
COMPARED TO ANY PLACE ELSE
THAT WE'VE EVER SEEN.

604
00:36:03,633 --> 00:36:05,767
SO HOW IS IT
THAT THE WATER GOT HERE?

605
00:36:05,767 --> 00:36:07,500
NOW, THERE IS A THEORY THAT SAYS

606
00:36:07,500 --> 00:36:10,400
THAT COMETS DELIVERED THE WATER
TO THE EARTH LONG AGO,

607
00:36:10,400 --> 00:36:12,967
BUT THE QUESTION IS,
CAN WE ACTUALLY PROVE IT?

608
00:36:16,267 --> 00:36:17,767
Narrator: TO FIND OUT,

609
00:36:17,767 --> 00:36:20,400
THE LANDER
WILL COLLECT WATER MOLECULES

610
00:36:20,400 --> 00:36:22,733
TO COMPARE WITH WATER
FROM EARTH.

611
00:36:22,733 --> 00:36:26,267
BUT SCIENTISTS
HOPE TO GO EVEN FURTHER.

612
00:36:26,267 --> 00:36:31,233
WE'RE ON THE BRINK OF MAKING
AN EXTRAORDINARY DISCOVERY.

613
00:36:31,233 --> 00:36:33,367
WE MAY FIND PROOF

614
00:36:33,367 --> 00:36:37,067
THAT LIFE ITSELF
HAS AN EXTRATERRESTRIAL ORIGIN,

615
00:36:37,067 --> 00:36:40,633
THAT IT WAS BROUGHT TO EARTH
BY COMETS.

616
00:36:52,300 --> 00:36:54,300
Narrator:
LIFE HAS EXISTED ON OUR PLANET

617
00:36:54,300 --> 00:36:58,700
FOR AT LEAST
3 1/2 BILLION YEARS.

618
00:36:58,700 --> 00:37:02,967
BUT WE STILL DON'T UNDERSTAND
ITS BEGINNINGS.

619
00:37:02,967 --> 00:37:08,433
WE USED TO THINK
LIFE ORIGINATED ON EARTH ITSELF,

620
00:37:08,433 --> 00:37:11,800
THAT VOLCANIC GASES
AND WATER VAPOR

621
00:37:11,800 --> 00:37:14,233
FORMED OCEANS AND AN ATMOSPHERE.

622
00:37:14,233 --> 00:37:20,400
LIGHTNING ADDED THE CREATIVE
SPARK FOR EARLY LIFE TO BEGIN.

623
00:37:20,400 --> 00:37:26,133
NOW WE THINK THAT'S WRONG,
AND THE EVIDENCE IS IN SPACE.

624
00:37:30,067 --> 00:37:34,067
IN 1997,
COMET HALE-BOPP APPEARED,

625
00:37:34,067 --> 00:37:38,800
ONE OF THE BIGGEST AND
BRIGHTEST COMETS EVER RECORDED.

626
00:37:38,800 --> 00:37:44,333
SCIENTISTS FOUND IT WAS PACKED
WITH WATER, GASES, AND CARBON --

627
00:37:44,333 --> 00:37:46,667
THE BASIC INGREDIENTS FOR LIFE.

628
00:37:48,800 --> 00:37:53,067
THAT DISCOVERY
RAISED PROFOUND QUESTIONS.

629
00:37:54,633 --> 00:37:57,233
WE'RE ALL USED TO THE IDEA THAT
LIFE ORIGINATED HERE ON EARTH,

630
00:37:57,233 --> 00:37:59,633
AND IT PROBABLY DID --
AT LEAST, COMPLEX LIFE.

631
00:37:59,633 --> 00:38:02,067
BUT WHERE DID
THE BUILDING BLOCKS COME FROM?

632
00:38:02,067 --> 00:38:04,233
WHERE DID THE WATER
THAT MAKES UP OUR BODY,

633
00:38:04,233 --> 00:38:07,333
THE ORGANIC MOLECULES THAT MAKE
UP THE VERY ESSENCE OF LIFE --

634
00:38:07,333 --> 00:38:08,900
THEY ACTUALLY MAY NOT HAVE BEEN

635
00:38:08,900 --> 00:38:11,267
INTRINSICALLY PART OF THE EARTH
TO BEGIN WITH.

636
00:38:11,267 --> 00:38:12,767
THEY CAME FROM SOMEWHERE ELSE.

637
00:38:12,767 --> 00:38:14,467
[ FLUTES PLAY DISSONANTLY ]

638
00:38:17,467 --> 00:38:21,600
Narrator: HALE-BOPP SUGGESTED
THAT THE RAW MATERIALS FOR LIFE

639
00:38:21,600 --> 00:38:25,067
MIGHT HAVE
AN EXTRATERRESTRIAL ORIGIN.

640
00:38:27,067 --> 00:38:31,067
SINCE THEN, SCIENTISTS
HAVE FOUND FURTHER EVIDENCE.

641
00:38:33,067 --> 00:38:36,067
ASTROBIOLOGIST DANTE LAURETTA

642
00:38:36,067 --> 00:38:41,100
DISCOVERED THAT DUST FROM COMET
WILD 2 CONTAINED MINERALS

643
00:38:41,100 --> 00:38:44,533
THAT COULD ONLY FORM
IN HEAT AND LIQUID WATER.

644
00:38:45,667 --> 00:38:48,433
Lauretta: WE HAD THE SULFIDE
MINERALS, WE HAD IRON OXIDES,

645
00:38:48,433 --> 00:38:49,867
WE HAD CARBONATE MINERALS --

646
00:38:49,867 --> 00:38:51,800
WHICH ARE THE SAME KIND OF
MATERIALS THAT MARINE ORGANISMS

647
00:38:51,800 --> 00:38:53,133
USE TO BUILD THEIR SHELLS --

648
00:38:53,133 --> 00:38:55,533
UNLIKE ANYTHING WE THOUGHT
WAS POSSIBLE TO BE FORMED

649
00:38:55,533 --> 00:38:56,733
IN THE EARLY SOLAR SYSTEM.

650
00:38:59,600 --> 00:39:01,833
Narrator:
SCIENTISTS HAVE EVEN FOUND

651
00:39:01,833 --> 00:39:07,233
THAT COMET WILD 2
CONTAINS AMINO ACIDS.

652
00:39:07,233 --> 00:39:08,767
THAT'S INCREDIBLY EXCITING,

653
00:39:08,767 --> 00:39:11,900
BECAUSE AMINO ACIDS ARE
THE BUILDING BLOCKS OF PROTEINS,

654
00:39:11,900 --> 00:39:14,200
AND PROTEINS
ARE ESSENTIAL BIOMOLECULES

655
00:39:14,200 --> 00:39:15,500
FOR ALL LIFE ON EARTH.

656
00:39:18,067 --> 00:39:20,733
Narrator: THESE DISCOVERIES
HAVE TRANSFORMED

657
00:39:20,733 --> 00:39:22,933
OUR UNDERSTANDING OF COMETS.

658
00:39:25,633 --> 00:39:27,767
MANY SCIENTISTS NOW BELIEVE

659
00:39:27,767 --> 00:39:31,233
THEY'RE MORE THAN
JUST FROZEN TIME CAPSULES.

660
00:39:32,733 --> 00:39:38,433
PERHAPS THEY PLAY A CENTRAL ROLE
IN THE HISTORY OF OUR PLANET.

661
00:39:38,433 --> 00:39:41,233
WE HAVE LEARNED
FROM A STUDY OF A SINGLE COMET

662
00:39:41,233 --> 00:39:43,100
AND THE RESULTS
OF THE STARDUST MISSION

663
00:39:43,100 --> 00:39:45,067
THAT THEY ARE
COMPLEX CHEMICAL LABORATORIES

664
00:39:45,067 --> 00:39:47,667
WHERE THE INGREDIENTS OF LIFE
COULD FORM.

665
00:39:47,667 --> 00:39:50,167
THESE MATERIALS
LIKELY DID NOT ARISE NATURALLY

666
00:39:50,167 --> 00:39:51,600
ON THE SURFACE OF THE EARTH

667
00:39:51,600 --> 00:39:53,600
FROM PROCESSES ON OUR PLANET.

668
00:39:53,600 --> 00:39:56,100
INSTEAD, THEY HAD TO BE
DELIVERED BY THESE MESSENGERS

669
00:39:56,100 --> 00:39:57,433
FROM THE OUTER SOLAR SYSTEM.

670
00:39:57,433 --> 00:40:01,500
Narrator: THE IDEA
THAT WE MAY OWE OUR EXISTENCE

671
00:40:01,500 --> 00:40:04,667
TO COMET IMPACTS IS ASTOUNDING.

672
00:40:04,667 --> 00:40:07,867
BUT NOT EVERYONE IS CONVINCED.

673
00:40:07,867 --> 00:40:10,467
THERE'S PRETTY GOOD
CIRCUMSTANTIAL EVIDENCE

674
00:40:10,467 --> 00:40:13,467
THAT A COMET MIGHT HAVE BEEN
IMPORTANT TO LIFE,

675
00:40:13,467 --> 00:40:15,167
BUT WE DON'T REALLY HAVE --

676
00:40:15,167 --> 00:40:16,233
IF WE'RE C.S.I.,

677
00:40:16,233 --> 00:40:18,433
IF WE'RE
THE COMET SCIENCE INVESTIGATORS

678
00:40:18,433 --> 00:40:19,567
TRYING TO PROVE IT,

679
00:40:19,567 --> 00:40:21,767
WE HAVEN'T GOT THE PROOF
LINED UP YET.

680
00:40:25,367 --> 00:40:28,433
IT'S QUITE POSSIBLE
THAT WHAT WE HAVE OUT THERE

681
00:40:28,433 --> 00:40:31,700
HAS NOTHING TO DO WITH LIFE
AS WE KNOW IT ON EARTH.

682
00:40:34,733 --> 00:40:39,433
Narrator: SCIENTISTS HOPE THE ROSETTA
MISSION WILL RESOLVE THE ISSUE.

683
00:40:42,600 --> 00:40:44,667
IF WE CAN ESTABLISH
A CORRELATION

684
00:40:44,667 --> 00:40:46,733
BETWEEN AMINO ACIDS ON COMETS

685
00:40:46,733 --> 00:40:50,500
AND THE AMINO ACIDS
WE HAVE ON EARTH, LIFE ON EARTH,

686
00:40:50,500 --> 00:40:54,067
THAT WOULD BE ONE OF THE MOST
SIGNIFICANT FINDINGS IN SCIENCE.

687
00:40:56,500 --> 00:41:02,367
Narrator: THE STORY OF LIFE ON EARTH
BEGAN 4 1/2 BILLION YEARS AGO.

688
00:41:02,367 --> 00:41:08,067
WHEN OUR PLANET FORMED,
IT WAS A BARREN, HOSTILE WORLD.

689
00:41:08,067 --> 00:41:10,967
700 MILLION YEARS LATER,

690
00:41:10,967 --> 00:41:13,467
THE SOLAR SYSTEM
PLUNGED INTO TURMOIL.

691
00:41:13,467 --> 00:41:16,833
GRAVITY RIPPED COMETS
FROM THEIR ORBITS

692
00:41:16,833 --> 00:41:19,200
AND HURLED THEM
IN ALL DIRECTIONS,

693
00:41:19,200 --> 00:41:22,500
MANY INTO
THE INNER SOLAR SYSTEM.

694
00:41:24,500 --> 00:41:26,533
THEY RAINED DOWN
ON THE EARLY EARTH

695
00:41:26,533 --> 00:41:29,733
FOR 300 MILLION YEARS.

696
00:41:32,333 --> 00:41:36,500
THEY RELEASED
GASES AND ORGANIC MATERIAL,

697
00:41:36,500 --> 00:41:39,533
CREATING AN ATMOSPHERE
AND THE OCEANS.

698
00:41:39,533 --> 00:41:43,833
FINALLY, LIFE COULD BEGIN.

699
00:41:48,700 --> 00:41:51,067
IT'S A DRAMATIC STORY.

700
00:41:51,067 --> 00:41:54,867
BUT IS IT TRUE?

701
00:41:54,867 --> 00:41:56,067
ONLY TIME IS GONNA TELL,

702
00:41:56,067 --> 00:41:57,900
IF WE KEEP STUDYING
THESE MYSTERIOUS OBJECTS,

703
00:41:57,900 --> 00:42:00,467
WHETHER OR NOT WE CAN REALLY PIN
DOWN EXACTLY THE MECHANISMS

704
00:42:00,467 --> 00:42:02,467
AND FIND OUT
HOW IT ALL GOT STARTED.

705
00:42:02,467 --> 00:42:04,367
Dr. Alexander:
IN 100 YEARS' TIME,

706
00:42:04,367 --> 00:42:06,300
HOPEFULLY,
WE'LL LOOK BACK AND SAY,

707
00:42:06,300 --> 00:42:09,467
"WOULDN'T IT BE COOL TO
HAVE BEEN LIVING AT THAT TIME,

708
00:42:09,467 --> 00:42:10,933
"TO BE A WITNESS,

709
00:42:10,933 --> 00:42:14,067
TO BE ONE OF THE FIRST TO MAKE
THESE INCREDIBLE DISCOVERIES"?

710
00:42:14,067 --> 00:42:16,633
Narrator: IN THE MEANTIME,

711
00:42:16,633 --> 00:42:19,967
THE SEARCH FOR PROOF CONTINUES.

712
00:42:22,700 --> 00:42:26,133
I CAN'T SAY FOR SURE
IF COMETS BROUGHT

713
00:42:26,133 --> 00:42:28,667
ALL OF THESE RAW INGREDIENTS
TO THE EARTH

714
00:42:28,667 --> 00:42:31,200
AND THAT WE EVOLVED
FROM THESE MATERIALS,

715
00:42:31,200 --> 00:42:33,133
BUT IT'S CERTAINLY POSSIBLE,

716
00:42:33,133 --> 00:42:35,467
AND IT'S ABSOLUTELY POETIC

717
00:42:35,467 --> 00:42:38,967
TO THINK THAT WE CAME
FROM OUT THERE.

718
00:42:38,967 --> 00:42:42,067
[ DRAMATIC MUSIC PLAYS ]