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Narrator:
FOR THOUSANDS OF YEARS,
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PLANET MERCURY
HAS BAFFLED ASTRONOMERS,
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00:00:06,874 --> 00:00:11,110
BUT NOW ITS SECRETS
HAVE BEEN REVEALED.
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00:00:11,112 --> 00:00:15,547
IT'S A BIZARRE WORLD
UNLIKE ANY OTHER.
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00:00:15,549 --> 00:00:17,883
WHEN YOU LOOK AT
THE FAMILY OF PLANETS
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00:00:17,885 --> 00:00:19,385
THAT MAKE UP OUR
SOLAR SYSTEM, YOU KNOW,
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00:00:19,387 --> 00:00:23,389
MERCURY DOES SEEM TO BE
A LITTLE BIT OF A WEIRDO.
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00:00:23,391 --> 00:00:26,892
Narrator:
THIS IS ONE TOUGH WORLD,
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00:00:26,894 --> 00:00:32,164
SURVIVING BRUTAL ATTACKS
FROM COMETS, THE SUN,
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00:00:32,166 --> 00:00:35,234
AND EVEN OTHER PLANETS.
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00:00:35,236 --> 00:00:37,236
YOU COULD SEE BY
THE SURFACE OF MERCURY
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00:00:37,238 --> 00:00:39,505
THAT IT HAS A LOT
OF BATTLE SCARS.
13
00:00:39,507 --> 00:00:42,641
THE SOLAR SYSTEM
DID NOT TREAT IT WELL.
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00:00:42,643 --> 00:00:44,143
Narrator: AND YET, THIS WORLD
15
00:00:44,145 --> 00:00:47,212
HAS BEEN BROUGHT TO LIFE
WITH WATER ICE,
16
00:00:47,214 --> 00:00:50,115
VOLCANISM,
AND TECTONIC ACTIVITY.
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00:00:51,786 --> 00:00:53,852
IF I HAD TO DESCRIBE
MERCURY IN A WORD,
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00:00:53,854 --> 00:00:55,888
IT WOULD BE "SURPRISING."
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Thaller: AT FIRST, IT MAY SEEM
THAT YOU COULD WRITE THIS OFF
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AS A DULL, LITTLE DEAD ROCK
CLOSE TO THE SUN,
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00:01:01,562 --> 00:01:04,163
BUT MERCURY HAS A STORY TO TELL.
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00:01:04,165 --> 00:01:05,964
Narrator:
AND THIS STORY COULD END
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00:01:05,966 --> 00:01:07,900
WITH MERCURY THREATENING
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00:01:07,902 --> 00:01:11,503
THE VERY EXISTENCE
OF PLANET EARTH.
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00:01:11,505 --> 00:01:14,973
IGNORE IT AT YOUR PERIL
BECAUSE THERE MAY COME A DAY
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00:01:14,975 --> 00:01:18,777
WHEN MERCURY MAKES ITS PRESENCE
VERY WELL KNOWN INDEED.
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-- Captions by VITAC --
www.vitac.com
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CAPTIONS PAID FOR BY
DISCOVERY COMMUNICATIONS
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♪♪
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Narrator:
2015, THE MESSENGER SPACECRAFT
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COMPLETES ITS FINAL ORBIT
AROUND PLANET MERCURY.
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♪♪
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AND THE IMAGES
SENT BACK TO EARTH
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DURING ITS MISSION
LEFT SCIENTISTS STUNNED.
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00:02:00,387 --> 00:02:03,889
OUR VIEW OF MERCURY FROM BEFORE
AND AFTER THE MESSENGER PROBE
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00:02:03,891 --> 00:02:06,091
IS LIKE HAVING TERRIBLE
VISION YOUR WHOLE LIFE
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00:02:06,093 --> 00:02:08,627
AND THEN FINALLY GOING
TO THE OPTOMETRIST
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00:02:08,629 --> 00:02:11,964
AND GETTING GLASSES
THAT CLEAR EVERYTHING UP,
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00:02:11,966 --> 00:02:13,966
AND IT COMPLETELY
OPENED OUR EYES
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00:02:13,968 --> 00:02:15,901
TO WHAT THIS PLANET LOOKS LIKE.
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Narrator: MERCURY ORBITS
THE INNERMOST SOLAR SYSTEM,
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THE CLOSEST PLANET TO THE SUN...
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...AROUND THREE TIMES CLOSER
THAN EARTH,
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00:02:28,949 --> 00:02:33,085
IN A SCORCHING ENVIRONMENT
OF LETHAL HEAT AND RADIATION.
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00:02:35,856 --> 00:02:38,557
CAPTURING IMAGES WAS
A MONUMENTAL CHALLENGE
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00:02:38,559 --> 00:02:42,427
FOR THE MESSENGER MISSION
TEAM LED BY SEAN SOLOMAN.
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MERCURY HAS BEEN AMONG
THE MOST DIFFICULT PLANETS
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IN THE SOLAR SYSTEM TO STUDY.
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00:02:48,669 --> 00:02:52,404
THE HUBBLE SPACE TELESCOPE
IS FORBIDDEN FROM VIEWING
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PLANET MERCURY BECAUSE IT'S
TOO CLOSE TO THE SUN,
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00:02:55,776 --> 00:02:58,677
AND THEIR OPTICS WOULD BE
SEVERELY DAMAGED.
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Narrator: MESSENGER LOOKS CLOSER
THAN WE EVER HAVE BEFORE.
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IT REVEALS A STRANGE WORLD,
JUST 5% THE MASS OF THE EARTH,
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CLOSER IN SIZE TO OUR MOON.
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00:03:13,961 --> 00:03:15,794
AT FIRST GLANCE,
MERCURY AND EARTH,
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THEY'RE NOTHING ALIKE, RIGHT?
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THEY'RE BOTH MADE OF ROCKS.
THAT'S ABOUT IT.
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THEY'RE BOTH ORBITING
THE SAME SUN,
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00:03:20,734 --> 00:03:23,702
BUT WHEN YOU START LOOKING
A LITTLE BIT CLOSER AT MERCURY,
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00:03:23,704 --> 00:03:26,071
YOU START TO SEE SOME
REALLY SURPRISING SIMILARITIES
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TO EARTH.
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Narrator:
WHEN SCIENTISTS LOOK AT MERCURY,
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THEY SPOT SOMETHING
THAT SHOULDN'T BE THERE.
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MERCURY HAS WATER ON IT,
WHICH IF YOU WERE GOING TO MAKE
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00:03:38,752 --> 00:03:41,053
A LONG LIST OF ALL
THE DISCOVERIES ABOUT MERCURY,
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I THINK WATER WOULD BE RIGHT
AT THE TOP OF
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"WHAT? WHAT? SERIOUSLY?"
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IF YOU THOUGHT IN ADVANCE
OF THE LAST PLACE IN THE WORLD
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TO FIND WATER,
YOU'D THINK OF MERCURY
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00:03:50,497 --> 00:03:53,532
BECAUSE IT'S SO CLOSE
TO THE SUN.
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00:03:53,534 --> 00:03:55,701
Narrator: IT GETS EVEN STRANGER.
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THE WATER EXISTS
IN THE FORM OF ICE.
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THERE COULD EVEN BE
A TRILLION TONS OF IT,
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ENOUGH TO ENCASE
WASHINGTON, D.C.,
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IN A FROZEN BLOCK 2 MILES THICK.
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SO HOW DO YOU GET FROZEN WATER
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ONTO THE CLOSEST PLANET
TO THE SUN?
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FOR ME, I THINK THE MOST
INTERESTING THING ABOUT MERCURY
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IS THE FACT THAT WHAT SHOULD BE
THE HOTTEST PLANET
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00:04:23,998 --> 00:04:25,230
IN THE SOLAR SYSTEM IS,
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00:04:25,232 --> 00:04:27,833
IN SOME PARTS,
AMONG THE COLDEST,
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00:04:27,835 --> 00:04:33,505
AND I LOVE THAT PARADOX
BECAUSE I LOVE THE UNEXPECTED.
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Narrator: MERCURY IS A WORLD
OF BRUTAL EXTREMES.
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THE SUN-FACING SIDE IS BLASTED
BY SOLAR RADIATION...
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00:04:44,018 --> 00:04:48,387
WITH TEMPERATURES ROCKETING
TO 800 DEGREES FAHRENHEIT,
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HOT ENOUGH TO MELT LEAD,
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BUT THE SIDE FACING AWAY
PLUMMETS TO -300.
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IT'S ALL BECAUSE OF MERCURY'S
ALMOST NONEXISTENT ATMOSPHERE.
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00:05:02,870 --> 00:05:06,238
PLANETARY SCIENTIST DAN DURDA
DEMONSTRATES THE EFFECT
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00:05:06,240 --> 00:05:08,640
THIS HAS USING A CAMPFIRE.
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00:05:10,644 --> 00:05:13,512
SO RIGHT NOW, WITH THIS JACKET
ON, HOLDING THE WARMTH IN,
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00:05:13,514 --> 00:05:15,881
I'M A BIT LIKE A PLANET
WITH AN ATMOSPHERE.
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THE ATMOSPHERE OF A PLANET,
IT'S A THERMAL BLANKET,
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00:05:17,718 --> 00:05:18,984
A THERMAL INSULATOR,
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THAT HELPS MAKE MORE UNIFORM
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THE TEMPERATURE
OF THE ENTIRE PLANET.
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00:05:21,822 --> 00:05:23,855
SO AT THE MOMENT,
I'M PRETTY WARM UNIFORMLY,
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BUT IF I TAKE MY JACKET
OFF ALTOGETHER,
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WELL, YOU KNOW, I CAN ALREADY
FEEL MY BACK COOLING OFF.
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SITTING HERE WITHOUT MY JACKET,
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00:05:35,169 --> 00:05:36,902
WITHOUT AN ATMOSPHERE,
IF YOU WILL,
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I'M LIKE THE PLANET MERCURY
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WHICH HAS NO EFFECTIVE
ATMOSPHERE,
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AND THEREFORE THE ONLY WARMTH
THAT IT CAN HOLD
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IS THE WARMTH RADIATING DIRECTLY
ON IT FROM THE SUN ITSELF.
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ANY PARTS OF MERCURY FACING
AWAY FROM THE SUN
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VERY RAPIDLY RADIATE
THAT HEAT OFF TO SPACE
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AND COOL TO VERY,
VERY CHILLY TEMPERATURES.
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Narrator: SO COULD WATER ICE
SURVIVE ON THE SIDE OF MERCURY
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FACING AWAY FROM THE SUN?
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00:06:04,998 --> 00:06:07,933
THE NIGHTTIME SIDE IS
VERY BITTERLY COLD.
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00:06:07,935 --> 00:06:10,502
IF THAT WERE THE END
OF THE STORY,
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YOU MIGHT BE ABLE TO HAVE,
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00:06:12,339 --> 00:06:15,741
YOU KNOW, FROZEN WATER,
ICY WATER, ON THE SIDE
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OF MERCURY FACING AWAY
FROM THE SUN.
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BUT MERCURY DOESN'T KEEP ONE
SIDE ALWAYS LOCKED TO THE SUN
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AND ONE SIDE ALWAYS FACING AWAY.
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IT ACTUALLY DOES ROTATE.
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IT ROTATES THREE TIMES
FOR EVERY TWO TRIPS
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IT TAKES AROUND THE SUN.
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Narrator: AS MERCURY TURNS,
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THE SUN WOULD VAPORIZE
ANY WATER ICE FACING IT.
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BUT ARE THERE SECRET
HIDING PLACES
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WHERE THE SUN CANNOT REACH?
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TO FIND THE ANSWER,
PLANETARY SCIENTIST NINA LANZA
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SEARCHES FISSURES IN ICELAND.
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SO HERE WE CAN SEE,
AT THE SURFACE, THERE'S NO ICE.
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IT'S TOO WARM, BUT IF WE LOOK
DOWN IN THIS FISSURE HERE,
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IT'S ONLY ABOUT 20 FEET DEEP,
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00:06:58,652 --> 00:07:02,788
BUT AT THE BOTTOM,
THERE'S ACTUALLY SOME ICE.
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00:07:02,790 --> 00:07:06,091
SO IF WE MEASURE A ROCK
THAT'S BEEN IN THE SUN,
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00:07:06,093 --> 00:07:10,328
LET'S SAY THIS ONE, WE CAN SEE
IT'S ACTUALLY PRETTY WARM.
133
00:07:10,330 --> 00:07:13,198
IT'S ABOUT 61 DEGREES
FAHRENHEIT,
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00:07:13,200 --> 00:07:14,566
BUT IF WE AIM, NOW,
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00:07:14,568 --> 00:07:16,668
FOR THE BOTTOM OF THIS HOLLOW,
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00:07:16,670 --> 00:07:20,405
WE CAN SEE NOW,
IT'S ABOUT 33 -- NOPE.
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IT'S DROPPING.
IT'S 32 DEGREES FAHRENHEIT,
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00:07:23,143 --> 00:07:25,544
AND THIS IS BECAUSE
THE SUN DOESN'T REALLY
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GET TO THE BOTTOM OF THIS PLACE,
AND THAT'S THE KEY.
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Narrator: WHILE THIS ICE
IS HIDDEN IN A FISSURE,
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ON MERCURY THE ICE
SURVIVES IN CRATERS
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ON THE PLANET'S NORTH POLE,
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00:07:41,161 --> 00:07:44,696
FOREVER SAFE FROM THE GLARE
OF DIRECT SUNLIGHT,
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00:07:44,698 --> 00:07:50,235
BECAUSE THESE CRATERS
SIT IN A PERFECT SPOT.
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00:07:50,237 --> 00:07:53,905
MERCURY'S AXIS DOESN'T TILT
VERY MUCH COMPARED TO THE SUN.
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00:07:53,907 --> 00:07:56,107
THE EARTH'S AXIS TILTS
ABOUT 23 DEGREES,
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00:07:56,109 --> 00:07:58,310
BUT MERCURY IS PRETTY MUCH
STRAIGHT UP AND DOWN,
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00:07:58,312 --> 00:08:01,513
AND THAT MEANS THAT AS LARGE
AS THE SUN IS IN THE SKY,
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00:08:01,515 --> 00:08:05,517
THERE ARE CRATERS ON THE POLES
THAT SUNLIGHT NEVER GETS TO.
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00:08:05,519 --> 00:08:07,452
THEY'RE ALWAYS COLD.
151
00:08:07,454 --> 00:08:09,654
SO THE SURFACE OF
MERCURY IS HEATED
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00:08:09,656 --> 00:08:12,023
AND THEN COOLED
AS IT MOVES AROUND THE SUN,
153
00:08:12,025 --> 00:08:16,161
BUT THERE ARE CRATERS THAT ARE
ALWAYS DARK AND ALWAYS COLD.
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Narrator: AGAINST ALL THE ODDS,
DESPITE EVERYTHING THAT SUGGESTS
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THIS SHOULDN'T HAPPEN,
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MERCURY IS A SAFE HAVEN
FOR THIS WATER ICE.
157
00:08:27,774 --> 00:08:30,742
THE BOTTOMS OF THESE CRATERS
ARE CALLED COLD TRAPS
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00:08:30,744 --> 00:08:32,477
BECAUSE THEY'RE SO COLD
THAT ANY WATER
159
00:08:32,479 --> 00:08:35,280
THAT GETS THERE STAYS
THERE BASICALLY FOREVER.
160
00:08:35,282 --> 00:08:37,883
IT CAN LAST LITERALLY
FOR BILLIONS OF YEARS.
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00:08:37,885 --> 00:08:39,985
BUT WHERE WOULD IT
HAVE COME FROM?
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00:08:41,955 --> 00:08:45,690
IT PROBABLY CAME FROM
COMETS AND ASTEROIDS.
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COMETS ARE GIANT CHUNKS OF ICE.
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00:08:48,362 --> 00:08:49,761
SO IF A COMET HITS MERCURY,
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00:08:49,763 --> 00:08:51,596
THAT'S GOING TO DELIVER
A LOT OF ICE,
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00:08:51,598 --> 00:08:53,031
AND, IN FACT, WE KNOW
A LOT OF ASTEROIDS
167
00:08:53,033 --> 00:08:54,566
HAVE ICE ON THEM AS WELL.
168
00:08:54,568 --> 00:08:58,136
SO BOTH OF THESE THINGS
COULD DELIVER WATER TO MERCURY.
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00:09:00,374 --> 00:09:02,741
Narrator: COMETS AND ASTEROIDS
BROUGHT WATER ICE
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00:09:02,743 --> 00:09:05,610
TO THE INNERMOST PLANETS
OF THE SOLAR SYSTEM.
171
00:09:07,648 --> 00:09:09,915
THIS SAME WATER DELIVERY SYSTEM
172
00:09:09,917 --> 00:09:15,153
GAVE EARTH THE ELEMENTS
NEEDED FOR LIFE.
173
00:09:15,155 --> 00:09:18,657
AND THOUGH MERCURY HAS
POCKETS OF FROZEN WATER,
174
00:09:18,659 --> 00:09:23,862
THE PLANET CAN NEVER USE IT
TO DEVELOP LIVING ORGANISMS.
175
00:09:23,864 --> 00:09:27,132
WHAT MERCURY IS REALLY
SHOWING US IS THAT YOU CAN START
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00:09:27,134 --> 00:09:30,502
WITH THE SAME BASIC BUILDING
BLOCKS FOR PLANETS, RIGHT?
177
00:09:30,504 --> 00:09:33,104
YOU CAN HAVE ESSENTIALLY
THE SAME MATERIALS,
178
00:09:33,106 --> 00:09:36,508
BUT END UP WITH VERY
DIFFERENT ENVIRONMENTS.
179
00:09:38,512 --> 00:09:40,312
Narrator:
COMPARED TO THE OTHER PLANETS,
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00:09:40,314 --> 00:09:44,716
MERCURY ENDED UP AS
THE RUNT OF THE LITTER.
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00:09:44,718 --> 00:09:48,520
BUT THERE'S EVIDENCE
THIS WASN'T ALWAYS THE CASE.
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00:09:48,522 --> 00:09:53,825
COULD THIS LITTLE WORLD HAVE
ONCE BEEN MUCH, MUCH BIGGER?
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00:10:02,836 --> 00:10:06,771
♪♪
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00:10:06,773 --> 00:10:09,941
Narrator: WE HAVE THEORIES FOR
HOW THE PLANETS FIRST FORMED
185
00:10:09,943 --> 00:10:13,044
IN OUR SOLAR SYSTEM,
186
00:10:13,046 --> 00:10:16,414
BUT MERCURY JUST DOESN'T FIT IN.
187
00:10:16,416 --> 00:10:18,950
WHEN YOU LOOK AT
THE FAMILY OF PLANETS
188
00:10:18,952 --> 00:10:20,485
THAT MAKE UP OUR SOLAR SYSTEM,
YOU KNOW,
189
00:10:20,487 --> 00:10:24,222
MERCURY DOES SEEM TO BE
A LITTLE BIT OF A WEIRDO.
190
00:10:24,224 --> 00:10:26,992
Plait: ON EARTH, WE HAVE
A RELATIVELY SMALL CORE
191
00:10:26,994 --> 00:10:29,227
AND A THICK MANTLE
AND A THIN CRUST.
192
00:10:29,229 --> 00:10:31,696
SO YOU COMPARE THE CORE OF THE
EARTH TO THE SIZE OF THE EARTH,
193
00:10:31,698 --> 00:10:33,031
IT'S RELATIVELY SMALL.
194
00:10:33,033 --> 00:10:35,700
IF YOU LOOK AT MERCURY,
IT'S NOT THAT WAY AT ALL.
195
00:10:35,702 --> 00:10:40,205
THE CORE IS ABSOLUTELY HUGE
COMPARED TO THE PLANET ITSELF.
196
00:10:40,207 --> 00:10:43,141
Narrator: MERCURY'S HUGE
IRON CORE IS SURROUNDED
197
00:10:43,143 --> 00:10:46,778
BY AN UNUSUALLY
THIN MANTLE OF ROCK.
198
00:10:46,780 --> 00:10:49,114
IT JUST LOOKS ODD.
199
00:10:49,116 --> 00:10:50,615
IT'S FUNNY.
200
00:10:50,617 --> 00:10:53,118
YOU DON'T EXPECT TO GET
A CORE THAT LARGE
201
00:10:53,120 --> 00:10:54,586
IN A PLANET THAT SMALL.
202
00:10:54,588 --> 00:10:58,590
IT'S ALMOST AS IF MERCURY LOST
SOME OF ITS MANTLE SOMEWHERE.
203
00:10:58,592 --> 00:11:00,925
I MEAN, MAYBE IT LEFT IT
BEHIND THE COUCH.
204
00:11:00,927 --> 00:11:02,827
WHO KNOWS?
BUT IT'S GONE NOW.
205
00:11:04,531 --> 00:11:08,366
Narrator: BUT HOW CAN THIS
MATERIAL JUST VANISH?
206
00:11:08,368 --> 00:11:10,969
Plait: MERCURY COULD BE
THE WAY IT IS NOW
207
00:11:10,971 --> 00:11:13,605
BECAUSE IT STARTED AS
A MUCH LARGER PLANET
208
00:11:13,607 --> 00:11:17,475
AND THEN SOMETHING HAPPENED TO
STRIP AWAY THE TOP LAYER OF IT,
209
00:11:17,477 --> 00:11:19,511
AND THE ONLY WAY
WE KNOW HOW TO DO THAT
210
00:11:19,513 --> 00:11:21,379
ON A PLANETARY SCALE
211
00:11:21,381 --> 00:11:23,381
IS WITH PLANETARY IMPACTS.
212
00:11:23,383 --> 00:11:27,786
♪♪
213
00:11:27,788 --> 00:11:33,324
Narrator:
PICTURE THE EARLY SOLAR SYSTEM
WHEN MERCURY IS STILL FORMING.
214
00:11:33,326 --> 00:11:37,629
IT'S COMPLETELY DIFFERENT FROM
THE LITTLE WORLD WE KNOW NOW.
215
00:11:37,631 --> 00:11:43,768
UP TO FOUR TIMES MORE MASSIVE,
TWICE THE MASS OF MARS,
216
00:11:43,770 --> 00:11:46,638
BUT IT ORBITS
IN A SHOOTING GALLERY.
217
00:11:46,640 --> 00:11:50,608
IMPACTS ARE INEVITABLE,
AND BEFORE LONG,
218
00:11:50,610 --> 00:11:55,547
AN OBJECT THE SIZE OF OUR MOON
SMASHES INTO MERCURY
219
00:11:55,549 --> 00:11:58,083
IN A GIANT IMPACT EVENT.
220
00:12:00,687 --> 00:12:01,920
Plait: THIS IS APOCALYPTIC.
221
00:12:01,922 --> 00:12:04,823
THIS IS THE SWEATIEST
NIGHTMARE YOU CAN HAVE.
222
00:12:04,825 --> 00:12:08,493
YOU'RE RESURFACING
AN ENTIRE PLANET.
223
00:12:08,495 --> 00:12:10,161
THE ENERGIES ARE VAST.
224
00:12:10,163 --> 00:12:12,831
ONE OF THESE GIANT IMPACTS
PROBABLY WOULD HAVE REMELTED IT
225
00:12:12,833 --> 00:12:14,032
ALL THE WAY THROUGH.
226
00:12:14,034 --> 00:12:15,900
WHAT'S GOING TO REMAIN
AFTER IT'S DONE
227
00:12:15,902 --> 00:12:17,068
IS COMPLETELY
DIFFERENT
228
00:12:17,070 --> 00:12:19,471
THAN WHAT STARTED
IN THE FIRST PLACE.
229
00:12:19,473 --> 00:12:26,745
IT'S HARD TO OVERSTATE JUST
HOW IMPACTFUL THESE EVENTS ARE.
230
00:12:26,747 --> 00:12:30,949
Narrator:
HUGE CHUNKS OF MERCURY'S MANTLE
ARE FLUNG INTO SPACE.
231
00:12:30,951 --> 00:12:33,384
THE RESULT?
232
00:12:33,386 --> 00:12:38,456
TWO-THIRDS OF ITS MASS
ARE NOW MADE UP BY ITS CORE,
233
00:12:38,458 --> 00:12:41,760
BUT WHERE DID THE REST OF IT GO?
234
00:12:41,762 --> 00:12:43,561
BILLIONS OF YEARS AGO,
THERE WAS A PLANET
235
00:12:43,563 --> 00:12:45,029
THAT WE WILL NEVER KNOW,
236
00:12:45,031 --> 00:12:48,666
A PLANET THAT WAS DESTROYED WHEN
THE CURRENT MERCURY WAS FORMED.
237
00:12:48,668 --> 00:12:52,570
IS IT POSSIBLE THAT SOME OF IT
MAY STILL BE OUT THERE?
238
00:12:55,475 --> 00:12:58,810
Narrator: THE LOST MANTLE DEBRIS
COULD STILL EXIST
239
00:12:58,812 --> 00:13:02,080
IN THE INNERMOST SOLAR SYSTEM.
240
00:13:02,082 --> 00:13:07,585
SCIENTISTS CALL THESE
HYPOTHETICAL OBJECTS VULCANOIDS.
241
00:13:07,587 --> 00:13:09,654
VULCANOIDS CAN BE VERY VALUABLE
242
00:13:09,656 --> 00:13:11,823
FOR UNDERSTANDING
THE FORMATION OF MERCURY
243
00:13:11,825 --> 00:13:13,391
BECAUSE SOME OF THESE VULCANOIDS
244
00:13:13,393 --> 00:13:17,095
MAY BE PIECES OF
MERCURY'S MISSING MANTLE.
245
00:13:17,097 --> 00:13:19,063
Narrator:
BUT IN ORDER TO SURVIVE,
246
00:13:19,065 --> 00:13:21,900
THESE VULCANOIDS
WOULD HAVE TO ORBIT
247
00:13:21,902 --> 00:13:24,736
ON A GRAVITATIONAL TIGHTROPE.
248
00:13:24,738 --> 00:13:27,305
YOU KNOW, LIKE THIS MARSHMALLOW,
VULCANOIDS EXIST
249
00:13:27,307 --> 00:13:31,676
IN KIND OF A PRECARIOUS
POSITION IN THE SOLAR SYSTEM,
250
00:13:31,678 --> 00:13:35,814
A LITTLE TOO CLOSE TO THE FIRE,
A LITTLE TOO CLOSE TO THE SUN,
251
00:13:35,816 --> 00:13:38,016
THOSE OBJECTS ACTUALLY
WOULD VAPORIZE AWAY,
252
00:13:38,018 --> 00:13:39,117
KIND OF LIKE THAT.
253
00:13:39,119 --> 00:13:41,753
[ LAUGHS ]
254
00:13:41,755 --> 00:13:43,288
IF YOU ORBIT TOO FAR
FROM THE SUN,
255
00:13:43,290 --> 00:13:45,290
YOU'RE GOING TO APPROACH
TOO CLOSELY TO MERCURY
256
00:13:45,292 --> 00:13:47,158
AND HAVE GRAVITATIONAL
ENCOUNTERS,
257
00:13:47,160 --> 00:13:50,995
MAYBE GET FLUNG OUT OF THE SOLAR
SYSTEM OR MAYBE JUST IMPACT
258
00:13:50,997 --> 00:13:53,565
MERCURY ITSELF
AND GET EATEN, IF YOU WILL.
259
00:13:55,902 --> 00:13:57,969
BUT IN-BETWEEN
THOSE TWO EXTREMES,
260
00:13:57,971 --> 00:14:00,138
AT JUST THE RIGHT
DISTANCE FROM THE SUN,
261
00:14:00,140 --> 00:14:02,140
A LITTLE CLOSER
TO THE SUN THAN MERCURY,
262
00:14:02,142 --> 00:14:04,375
BUT NOT SO CLOSE
THAT YOU GET FRIED,
263
00:14:04,377 --> 00:14:08,580
IS THIS VULCANOID REGION WHERE
OBJECTS IN ORBIT AROUND THE SUN
264
00:14:08,582 --> 00:14:10,615
COULD REMAIN
GRAVITATIONALLY STABLE
265
00:14:10,617 --> 00:14:12,784
OVER THE ENTIRE AGE
OF THE SOLAR SYSTEM.
266
00:14:12,786 --> 00:14:15,720
THAT'S THE PLACE TO LOOK
FOR THIS POTENTIAL POPULATION
267
00:14:15,722 --> 00:14:18,089
OF LITTLE ASTEROID-LIKE OBJECTS.
268
00:14:20,627 --> 00:14:22,694
Narrator:
WE KNOW WHERE THEY SHOULD BE,
269
00:14:22,696 --> 00:14:25,697
BUT THERE'S A PROBLEM.
270
00:14:25,699 --> 00:14:27,298
YOU MAY WONDER WHY HAVEN'T
271
00:14:27,300 --> 00:14:29,801
WE SEEN THESE VULCANOIDS
IF THEY ACTUALLY EXIST?
272
00:14:29,803 --> 00:14:32,303
IF THEY'RE ACTUALLY ORBITING,
WHY DON'T WE JUST LOOK FOR THEM?
273
00:14:32,305 --> 00:14:36,074
WELL, IT'S BECAUSE THEY'RE
REALLY CLOSE TO THE SUN.
274
00:14:36,076 --> 00:14:38,076
Durda: UNLIKE THE ASTEROIDS
OR THE KUIPER BELT OBJECTS
275
00:14:38,078 --> 00:14:40,778
WHERE WE'RE LOOKING OUT
AWAY FROM THE SUN
276
00:14:40,780 --> 00:14:42,113
FROM OUR PERSPECTIVE
HERE ON THE EARTH,
277
00:14:42,115 --> 00:14:44,749
WE'RE LOOKING OUT INTO
THE DARK NIGHTTIME SKY,
278
00:14:44,751 --> 00:14:46,551
IN THE CASE OF THE VULCANOIDS,
WE'RE LOOKING FOR SOMETHING
279
00:14:46,553 --> 00:14:48,219
VERY, VERY CLOSE TO THE SUN,
280
00:14:48,221 --> 00:14:51,256
IN CLOSE TO THAT REALLY
BRILLIANT LIGHT SOURCE.
281
00:14:53,059 --> 00:14:58,229
Narrator: OUR SUN IS AROUND
900,000 MILES ACROSS.
282
00:14:58,231 --> 00:15:02,000
MERCURY IS JUST 3,000.
283
00:15:02,002 --> 00:15:06,271
WHEN OUR TELESCOPES SEE MERCURY
PASSING IN FRONT OF THE SUN,
284
00:15:06,273 --> 00:15:09,674
IT'S LITTLE MORE
THAN A PINPRICK.
285
00:15:09,676 --> 00:15:12,176
WITH VULCANOIDS, WE'RE SEARCHING
FOR SOMETHING
286
00:15:12,178 --> 00:15:16,681
THOUSANDS OF TIMES
SMALLER THAN MERCURY.
287
00:15:16,683 --> 00:15:20,551
IF VULCANOIDS EXIST,
THEY ORBIT IN A BLIND SPOT,
288
00:15:22,989 --> 00:15:26,357
BUT SCIENTISTS WILL KEEP
SEARCHING FOR THEM
289
00:15:26,359 --> 00:15:30,395
BECAUSE THEY COULD BE
THE LAST SURVIVING REMNANTS
290
00:15:30,397 --> 00:15:33,231
OF MERCURY'S LOST MANTLE.
291
00:15:33,233 --> 00:15:36,868
IF WE WERE TO DISCOVER
VULCANOIDS, THAT WOULD OFFER US
292
00:15:36,870 --> 00:15:39,771
AN ENTIRELY NEW POPULATION
OF OBJECTS TO STUDY.
293
00:15:39,773 --> 00:15:42,774
THIS MATERIAL COULD OFFER
SOME RATHER UNIQUE INSIGHT
294
00:15:42,776 --> 00:15:45,009
INTO THE FORMATION
OF MERCURY ITSELF.
295
00:15:47,113 --> 00:15:51,983
Narrator: A GIANT HEAD-ON IMPACT
HAS BEEN OUR BEST EXPLANATION
296
00:15:51,985 --> 00:15:54,152
FOR MERCURY'S WEIRD STRUCTURE.
297
00:15:54,154 --> 00:15:58,790
♪♪
298
00:15:58,792 --> 00:16:01,159
BUT NOW THERE'S A
STARTLING NEW THEORY
299
00:16:01,161 --> 00:16:03,361
FOR MERCURY'S MISSING MANTLE.
300
00:16:05,198 --> 00:16:09,334
IT WAS STOLEN,
BUT WHO IS THE THIEF?
301
00:16:17,377 --> 00:16:20,812
♪♪
302
00:16:20,814 --> 00:16:23,915
Narrator: FOR YEARS,
WE ASSUMED THAT MERCURY LOST
303
00:16:23,917 --> 00:16:27,752
MOST OF ITS MANTLE
IN A GIANT HEAD-ON COLLISION.
304
00:16:27,754 --> 00:16:32,323
♪♪
305
00:16:32,325 --> 00:16:36,127
BUT THE MESSENGER SPACECRAFT
TURNED EVERYTHING ON ITS HEAD.
306
00:16:37,731 --> 00:16:39,497
ONE OF THE EXCITING THINGS
THAT WE'VE LEARNED
307
00:16:39,499 --> 00:16:40,732
ABOUT MERCURY RECENTLY
308
00:16:40,734 --> 00:16:42,500
BY SENDING PROBES
TO STUDY ITS SURFACE
309
00:16:42,502 --> 00:16:44,235
IS THAT ITS SURFACE
IS LITTERED WITH MATERIAL
310
00:16:44,237 --> 00:16:46,704
THAT WE DIDN'T THINK
SHOULD BE THERE,
311
00:16:46,706 --> 00:16:49,440
THINGS THAT WE'D CALL VOLATILES.
312
00:16:49,442 --> 00:16:53,978
Narrator:
THE VOLATILES ARE CHEMICAL
ELEMENTS LIKE POTASSIUM.
313
00:16:53,980 --> 00:16:56,647
THEY'RE CALLED VOLATILE...
314
00:16:56,649 --> 00:16:58,549
BECAUSE THEY EVAPORATE EASILY
315
00:16:58,551 --> 00:17:00,651
IN HIGH TEMPERATURES,
316
00:17:00,653 --> 00:17:06,524
JUST THE SORTS OF TEMPERATURES
GENERATED BY A GIANT IMPACT.
317
00:17:06,526 --> 00:17:08,626
Oluseyi: IF I HAD TO DESCRIBE
MERCURY IN A WORD,
318
00:17:08,628 --> 00:17:11,129
IT WOULD BE "SURPRISING."
319
00:17:11,131 --> 00:17:14,665
THE IDEA WAS THAT A SMALLER
OBJECT RAN INTO MERCURY
320
00:17:14,667 --> 00:17:16,334
AND KNOCKED OFF MATERIAL.
321
00:17:16,336 --> 00:17:19,237
WELL, THAT ACTUALLY WOULD WORK
TO MAKE IT LOSE MATERIAL,
322
00:17:19,239 --> 00:17:21,439
BUT IT WOULD ALSO GENERATE
A LOT OF HEAT,
323
00:17:21,441 --> 00:17:24,208
AND BECAUSE OF THAT, THE
VOLATILE MATERIALS ON MERCURY
324
00:17:24,210 --> 00:17:26,010
WOULD ALSO HAVE BEEN LOST.
325
00:17:26,012 --> 00:17:27,979
BUT TODAY, WE SEE THAT
THEY'RE STILL THERE.
326
00:17:27,981 --> 00:17:32,417
SO IT MEANT THAT MOST OF THE
BASIC SCENARIOS THAT HAVE BEEN
327
00:17:32,419 --> 00:17:35,753
LAID OUT FOR HOW MERCURY WAS
ASSEMBLED HAD BEEN DISPROVEN.
328
00:17:37,824 --> 00:17:40,091
WE HAD TO GO BACK
TO THE DRAWING BOARD
329
00:17:40,093 --> 00:17:42,760
AND RETHINK HOW
MERCURY WAS ASSEMBLED
330
00:17:42,762 --> 00:17:45,396
AND HOW MERCURY EVOLVED.
331
00:17:45,398 --> 00:17:48,299
Narrator:
HOW DID MERCURY LOSE ITS MANTLE
332
00:17:48,301 --> 00:17:51,369
BUT RETAIN THESE VOLATILES?
333
00:17:51,371 --> 00:17:53,604
MERCURY IS LIKE
A DETECTIVE CASE.
334
00:17:53,606 --> 00:17:55,573
WE HAVE THE BODY.
WE HAVE SOME CLUES,
335
00:17:55,575 --> 00:17:58,309
BUT WE REALLY HAVE TO
PIECE IT TOGETHER.
336
00:17:58,311 --> 00:18:00,912
Narrator: PLANETARY SCIENTIST
ERIK ASPHAUG
337
00:18:00,914 --> 00:18:03,514
TACKLES THIS GIANT RIDDLE.
338
00:18:03,516 --> 00:18:05,016
THE ORIGINAL IDEA WAS THAT
339
00:18:05,018 --> 00:18:08,419
MERCURY WAS HIT BY SOMETHING
SMALLER THAN ITSELF.
340
00:18:08,421 --> 00:18:10,788
BUT WHATEVER PROCESS
MADE MERCURY
341
00:18:10,790 --> 00:18:14,192
SOMEHOW PRESERVED
ALL THESE VOLATILES
342
00:18:14,194 --> 00:18:17,295
THAT SHOULD HAVE
VAPORIZED AND GONE.
343
00:18:17,297 --> 00:18:20,731
Narrator:
ERIK HAS A BOLD ALTERNATIVE,
344
00:18:20,733 --> 00:18:23,601
A HIT-AND-RUN COLLISION.
345
00:18:23,603 --> 00:18:26,070
IN THE HIT-AND-RUN COLLISION
IDEA, YOU ACTUALLY HAVE
346
00:18:26,072 --> 00:18:28,840
MERCURY HITTING SOMETHING
BIGGER THAN ITSELF
347
00:18:28,842 --> 00:18:31,642
WITHOUT LOSING
ALL OF ITS VOLATILES.
348
00:18:33,746 --> 00:18:37,815
Narrator: HITTING SOMETHING
BIGGER MAY SOUND EVEN WORSE,
349
00:18:37,817 --> 00:18:40,451
BUT IT ALL DEPENDS
ON HOW YOU HIT IT.
350
00:18:42,355 --> 00:18:47,658
IN THE EARLY SOLAR SYSTEM,
THERE WERE A LOT OF PLAYERS,
351
00:18:47,660 --> 00:18:51,662
AND JUST LIKE A HOCKEY MATCH,
THINGS GOT BRUTAL.
352
00:18:53,666 --> 00:18:57,735
YOU WOULD HAVE HAD PLANETESIMALS
GROWING THROUGH COLLISIONS.
353
00:18:57,737 --> 00:18:59,837
THE BIGGER OBJECTS
WOULD HAVE DOMINATED
354
00:18:59,839 --> 00:19:02,707
BECAUSE NOT ONLY ARE THEY
RUNNING INTO SMALLER OBJECTS,
355
00:19:02,709 --> 00:19:05,610
THEY'RE DRAWING THEM
TO THEMSELVES GRAVITATIONALLY,
356
00:19:05,612 --> 00:19:08,813
AND TWO OBJECTS WILL SWEEP UP
MOST OF THE MATTER.
357
00:19:08,815 --> 00:19:11,983
THOSE TWO OBJECTS
BECAME VENUS AND EARTH.
358
00:19:13,253 --> 00:19:15,353
Narrator: EARTH AND VENUS
ARE THE ENFORCERS
359
00:19:15,355 --> 00:19:18,022
OF THE INNER SOLAR SYSTEM,
360
00:19:18,024 --> 00:19:19,824
WIPING OUT MOST
OF THE COMPETITION.
361
00:19:19,826 --> 00:19:23,361
WHOO!
362
00:19:23,363 --> 00:19:26,964
Narrator: LITTLE MERCURY IS ONE
OF THE LAST PLAYERS LEFT,
363
00:19:26,966 --> 00:19:30,835
AND IT COULD HAVE
A FACEOFF WITH EARTH.
364
00:19:30,837 --> 00:19:33,437
MERCURY IS THE LITTLE GUY
IN THIS THING,
365
00:19:33,439 --> 00:19:36,140
AND THIS HOCKEY PUCK
IS OUR VOLATILES.
366
00:19:36,142 --> 00:19:40,011
♪♪
367
00:19:40,013 --> 00:19:42,213
THE LITTLE GUY COMES IN
AT A HIGH SPEED
368
00:19:42,215 --> 00:19:45,550
AND HAS A HEAD-ON COLLISION
WITH THE BIG GUY.
369
00:19:45,552 --> 00:19:47,351
IT IS CATASTROPHIC.
370
00:19:47,353 --> 00:19:50,888
♪♪
371
00:19:50,890 --> 00:19:52,957
BUT SUPPOSE NOW,
INSTEAD OF HITTING HIM
372
00:19:52,959 --> 00:19:54,358
IN A HEAD-ON COLLISION,
373
00:19:54,360 --> 00:19:56,160
HE HITS HIM IN A GLANCING BLOW.
374
00:19:56,162 --> 00:20:03,467
♪♪
375
00:20:03,469 --> 00:20:05,937
SO HE MIGHT KNOCK OFF
A LITTLE BIT OF EQUIPMENT,
376
00:20:05,939 --> 00:20:09,240
BUT MERCURY JUST KEEPS ON GOING
AND KEEPS HIS HOCKEY PUCK.
377
00:20:09,242 --> 00:20:12,677
♪♪
378
00:20:12,679 --> 00:20:16,447
Narrator:
A HEAD-ON IMPACT WOULD SEND
A SHOCKWAVE ACROSS MERCURY,
379
00:20:16,449 --> 00:20:18,883
MELTING THE ENTIRE SURFACE.
380
00:20:18,885 --> 00:20:22,220
♪♪
381
00:20:22,222 --> 00:20:25,957
BUT A GLANCING BLOW
IS LESS FEROCIOUS.
382
00:20:25,959 --> 00:20:27,959
THE MORE GRAZING
YOU HIT SOMETHING,
383
00:20:27,961 --> 00:20:32,897
THE LESS ENERGY YOU BRING
TO BEAR, THE LESS VIOLENT IT IS.
384
00:20:32,899 --> 00:20:35,933
IN THE GRAZING COLLISION
IS WHERE PIECE OF THE SURFACE
385
00:20:35,935 --> 00:20:38,302
HAS GRAZED OFF
AND BLASTED INTO SPACE,
386
00:20:38,304 --> 00:20:41,739
AND THE OTHER HEMISPHERE OF
THE BODY IS LARGELY UNAFFECTED
387
00:20:41,741 --> 00:20:44,108
AND ALLOWED SOME
PRIMORDIAL MATERIAL
388
00:20:44,110 --> 00:20:46,377
TO REMAIN ON THE SURFACE.
389
00:20:46,379 --> 00:20:51,182
Narrator: MOST OF MERCURY'S
MANTLE IS STRIPPED AWAY,
390
00:20:51,184 --> 00:20:53,117
BUT THIS GRAZING IMPACT
391
00:20:53,119 --> 00:20:56,554
DOESN'T SEND A SHOCKWAVE
THROUGH THE PLANET,
392
00:20:56,556 --> 00:21:01,692
AND SO THE VOLATILES REMAIN
ALONG WITH ENOUGH OF THE MANTLE
393
00:21:01,694 --> 00:21:06,197
TO RESHAPE THIS WORLD
WITH A THIN OUTER LAYER OF ROCK.
394
00:21:06,199 --> 00:21:09,867
♪♪
395
00:21:09,869 --> 00:21:13,204
MERCURY WAS TRANSFORMED
INTO THE SMALLEST PLANET
396
00:21:13,206 --> 00:21:16,140
IN THE SOLAR SYSTEM,
397
00:21:16,142 --> 00:21:20,811
AND ITS LOST MANTLE WAS STOLEN
BY AN UNEXPECTED THIEF.
398
00:21:22,515 --> 00:21:25,016
THAT MANTLE ACCRETES ONTO
THE BIGGEST OBJECT AROUND,
399
00:21:25,018 --> 00:21:29,020
BUT THE BIGGEST OBJECT
AROUND ISN'T MERCURY.
400
00:21:29,022 --> 00:21:32,189
Oluseyi:
WHEN MERCURY'S MANTLE GOT
KNOCKED OFF IN THIS COLLISION,
401
00:21:32,191 --> 00:21:33,391
IT HAD TO GO SOMEWHERE.
402
00:21:33,393 --> 00:21:35,726
SO IF YOU'RE LOOKING FOR
MERCURY'S MISSING MANTLE,
403
00:21:35,728 --> 00:21:37,962
LOOK NO FURTHER THAN RIGHT
UNDER YOUR FEET.
404
00:21:39,465 --> 00:21:45,369
Narrator: TO THIS DAY, PART OF
MERCURY COULD BE PART OF EARTH,
405
00:21:45,371 --> 00:21:48,139
STOLEN IN A HIT-AND-RUN
COLLISION.
406
00:21:49,876 --> 00:21:53,044
MERCURY WAS ABLE TO SURVIVE THE
FORMATION OF THE SOLAR SYSTEM,
407
00:21:53,046 --> 00:21:54,345
BUT IT PAID A COST.
408
00:21:54,347 --> 00:21:57,915
IT WAS BATTERED.
409
00:21:57,917 --> 00:22:02,520
Narrator: SINCE DAY ONE,
MERCURY HAS HAD A TOUGH RIDE.
410
00:22:02,522 --> 00:22:06,957
IT'S BEEN POUNDED BY THE SUN
AND PLANETS,
411
00:22:06,959 --> 00:22:09,393
AND THINGS HAVE NOT
IMPROVED SINCE.
412
00:22:09,395 --> 00:22:11,295
YOU CAN SEE BY THE SURFACE
OF MERCURY
413
00:22:11,297 --> 00:22:13,664
THAT IT HAS A LOT
OF BATTLE SCARS.
414
00:22:13,666 --> 00:22:16,067
THE SOLAR SYSTEM DID NOT
TREAT IT WELL.
415
00:22:17,870 --> 00:22:23,040
Narrator: THE PLANET HAS BEEN
BOMBARDED AND FRIED,
416
00:22:23,042 --> 00:22:25,676
BUT THESE EVENTS
COULD HELP EXPLAIN
417
00:22:25,678 --> 00:22:28,846
ONE OF MERCURY'S
BIGGEST MYSTERIES.
418
00:22:28,848 --> 00:22:32,216
WHY IS THE PLANET SO DARK?
419
00:22:41,627 --> 00:22:43,794
♪♪
420
00:22:43,796 --> 00:22:48,132
Narrator:
THE SOLAR SYSTEM IS FULL OF
BEAUTIFUL, COLORFUL PLANETS...
421
00:22:50,236 --> 00:22:54,171
...BUT MERCURY IS DIFFERENT.
422
00:22:54,173 --> 00:22:58,976
ITS DARK GRAY SURFACE
BAFFLES SCIENTISTS.
423
00:22:58,978 --> 00:23:00,344
ONE OF THE MOST
INTRIGUING THINGS
424
00:23:00,346 --> 00:23:03,047
IS HOW DARK THE SURFACE
OF MERCURY IS.
425
00:23:03,049 --> 00:23:05,416
A BIG MYSTERY IN
THE SOLAR SYSTEM IS WHY?
426
00:23:05,418 --> 00:23:07,718
WHY IS MERCURY LIKE THAT?
427
00:23:07,720 --> 00:23:11,222
Narrator:
THE ROCKY INNER PLANETS
ALL FORMED IN THE SAME REGION
428
00:23:11,224 --> 00:23:15,726
OF THE SOLAR SYSTEM
FROM SIMILAR MATERIALS,
429
00:23:15,728 --> 00:23:20,231
AND YET MERCURY IS DARKER
THAN ALL OF THEM.
430
00:23:20,233 --> 00:23:24,969
SOME OF THE DARKEST SURFACES
HERE ON EARTH ARE LAVA FIELDS.
431
00:23:24,971 --> 00:23:29,440
PLANETARY SCIENTIST NINA LANZA
VISITS ONE IN ICELAND
432
00:23:29,442 --> 00:23:33,010
TO FIND SOME COMMON GROUND.
433
00:23:33,012 --> 00:23:35,946
THE SURFACE OF A PLANET
RECORDS THE HISTORY
434
00:23:35,948 --> 00:23:38,449
OF ALL THE PROCESSES
THAT HAVE ACTED UPON IT.
435
00:23:38,451 --> 00:23:40,384
SO WHEN WE LOOK AT
THE SURFACE OF MERCURY,
436
00:23:40,386 --> 00:23:42,820
WE CAN PIECE
TOGETHER THAT STORY.
437
00:23:42,822 --> 00:23:47,425
RIGHT NOW, WE'RE STANDING
ON A BASALT LAVA FLOW.
438
00:23:47,427 --> 00:23:49,794
BASALT IS A TYPE
OF VOLCANIC ROCK
439
00:23:49,796 --> 00:23:52,196
THAT'S THE BUILDING
BLOCK OF ALL PLANETS,
440
00:23:52,198 --> 00:23:55,299
SO WE KNOW JUST BY SEEING
THIS BASALT HERE,
441
00:23:55,301 --> 00:23:57,668
THERE WAS VOLCANIC ACTIVITY.
442
00:24:00,506 --> 00:24:04,542
Narrator:
ON EARTH, MOST BASALTIC ROCK
IS COVERED BY OCEANS.
443
00:24:04,544 --> 00:24:08,579
ON MERCURY,
THE BASALT IS EXPOSED.
444
00:24:08,581 --> 00:24:11,048
OLD LIQUID LAVA FLOWS
ARE VISIBLE
445
00:24:11,050 --> 00:24:15,386
AS SMOOTH CHANNELS
OF SOLID ROCK.
446
00:24:15,388 --> 00:24:18,789
FOR A BILLION YEARS
AFTER MERCURY'S FORMATION,
447
00:24:18,791 --> 00:24:22,259
LAVA EXPLODES
FROM VOLCANIC VENTS
448
00:24:22,261 --> 00:24:24,528
AND LEAKS OUT FROM FISSURES.
449
00:24:26,799 --> 00:24:30,468
COULD THE VOLCANISM EXPLAIN
THE DARK WORLD WE SEE TODAY?
450
00:24:32,405 --> 00:24:35,139
Lanza: BASALT IS A PRETTY
DARK ROCK ALREADY,
451
00:24:35,141 --> 00:24:36,807
BUT WHAT'S SO INTERESTING
ABOUT MERCURY
452
00:24:36,809 --> 00:24:40,077
IS THAT IT'S ACTUALLY
DARKER THAN BASALT.
453
00:24:40,079 --> 00:24:43,614
SO FROM THE RECENT
MESSENGER MISSION TO MERCURY,
454
00:24:43,616 --> 00:24:47,451
WE HAD SOME IDEAS ABOUT WHAT MAY
BE MAKING THE SURFACE SO DARK,
455
00:24:47,453 --> 00:24:48,586
AND IT'S REALLY STRANGE.
456
00:24:48,588 --> 00:24:51,922
IT'S ACTUALLY CARBON
IN THE FORM OF GRAPHITE,
457
00:24:51,924 --> 00:24:54,725
THE MINERAL GRAPHITE, WHICH
IS WHAT YOU FIND IN A PENCIL.
458
00:24:54,727 --> 00:24:59,396
SO THAT MATERIAL IS ALL OVER
THE SURFACE OF MERCURY,
459
00:24:59,398 --> 00:25:02,299
AND IT'S INCORPORATED
INTO THE ROCKS.
460
00:25:02,301 --> 00:25:06,070
Narrator: CARBON DOESN'T COME
FROM BASALTIC ROCK,
461
00:25:06,072 --> 00:25:08,072
BUT THERE IS SOMETHING ELSE
462
00:25:08,074 --> 00:25:12,443
THAT COULD HAVE BROUGHT
CARBON TO MERCURY --
463
00:25:12,445 --> 00:25:14,545
COMETS.
464
00:25:14,547 --> 00:25:18,482
THESE DIRTY ICE BALLS
CONTAIN CARBON,
465
00:25:18,484 --> 00:25:22,920
AND THEY'VE BOMBARDED THE PLANET
FOR BILLIONS OF YEARS.
466
00:25:22,922 --> 00:25:27,157
THE EVIDENCE OF THESE ATTACKS
IS ETCHED INTO THE SURFACE.
467
00:25:28,628 --> 00:25:31,896
IT'S HARD TO LOOK AT MERCURY
AND NOT WINCE ON OCCASION.
468
00:25:31,898 --> 00:25:34,598
IT IS REALLY COVERED
WITH CRATERS.
469
00:25:34,600 --> 00:25:37,067
IT HAS BEEN BATTERED
AND BRUISED.
470
00:25:37,069 --> 00:25:39,370
IT REALLY HAS JUST
BEEN TERRIBLY,
471
00:25:39,372 --> 00:25:42,907
TERRIBLY MISTREATED
OVER ITS LIFETIME.
472
00:25:42,909 --> 00:25:47,811
Narrator: MERCURY HAS BEEN HIT
OFTEN AND HARD.
473
00:25:47,813 --> 00:25:49,547
Plait:
MERCURY IS MOVING MORE RAPIDLY
474
00:25:49,549 --> 00:25:51,115
AROUND THE SUN
THAN THE EARTH IS,
475
00:25:51,117 --> 00:25:53,918
SO A HEAD-ON IMPACT
IS GOING TO BE FASTER
476
00:25:53,920 --> 00:25:56,487
THAN A HEAD-ON IMPACT
OF A COMET IN THE EARTH.
477
00:25:56,489 --> 00:25:59,623
SO POUND FOR POUND,
A COMET IMPACT ON MERCURY
478
00:25:59,625 --> 00:26:01,058
IS MUCH MORE ENERGETIC,
479
00:26:01,060 --> 00:26:04,128
WILL DO MUCH MORE DAMAGE
THAN AN IMPACT ON EARTH.
480
00:26:06,799 --> 00:26:09,233
IF YOU'VE EVER BEEN TO, LIKE,
METEOR CRATER IN ARIZONA
481
00:26:09,235 --> 00:26:11,902
IN THE UNITED STATES,
IT'S AROUND A MILE ACROSS.
482
00:26:11,904 --> 00:26:13,771
IT'S THIS HUGE CRATER.
483
00:26:13,773 --> 00:26:17,775
IF YOU WERE TO STICK THAT CRATER
ON MERCURY, IT WOULD DISAPPEAR.
484
00:26:17,777 --> 00:26:20,511
MERCURY HAS SO MANY CRATERS
THAT ARE SO MUCH BIGGER
485
00:26:20,513 --> 00:26:22,813
THAN A MILE ACROSS.
486
00:26:22,815 --> 00:26:26,984
Narrator: MERCURY'S BIGGEST
IMPACT SITE IS CALORIS BASIN.
487
00:26:26,986 --> 00:26:30,120
OVER 1,000 TIMES LARGER
THAN METEOR CRATER,
488
00:26:30,122 --> 00:26:35,859
IT'S SO BIG THERE ARE NOW OTHER,
NEWER CRATERS INSIDE IT...
489
00:26:35,861 --> 00:26:39,363
AND CALORIS BASIN
IS COATED IN CARBON.
490
00:26:41,100 --> 00:26:42,866
Plait: COMETS HAVE A LOT
OF CARBON IN THEM,
491
00:26:42,868 --> 00:26:45,235
AND WE KNOW THAT
COMETS HIT PLANETS.
492
00:26:45,237 --> 00:26:47,204
SO IT'S KIND OF OBVIOUS TO SAY,
493
00:26:47,206 --> 00:26:48,272
"WHERE DID THE CARBON
COME FROM?"
494
00:26:48,274 --> 00:26:51,375
WELL, COMETS, BUT MAYBE NOT.
495
00:26:53,479 --> 00:26:58,816
Narrator:
IN 2016, THE MESSENGER TEAM
REVEALS AN EXCITING NEW THEORY.
496
00:26:58,818 --> 00:27:01,185
ARE THE LARGEST IMPACT CRATERS
497
00:27:01,187 --> 00:27:05,155
ACTUALLY EXPOSING
SOMETHING DEEPER?
498
00:27:05,157 --> 00:27:08,759
IMPACT CRATERS ARE WINDOWS
INTO THE LOWER PARTS
499
00:27:08,761 --> 00:27:10,694
OF THE CRUST OF A PLANET,
500
00:27:10,696 --> 00:27:12,029
AND THE LARGER
THE IMPACT CRATER,
501
00:27:12,031 --> 00:27:14,131
THE DEEPER THE IMPACT EVENT
502
00:27:14,133 --> 00:27:17,134
HAS EXCAVATED
MATERIAL FROM DEPTH
503
00:27:17,136 --> 00:27:20,904
AND BROUGHT IT TO WHERE
WE CAN SEE IT AT THE SURFACE.
504
00:27:20,906 --> 00:27:24,808
Narrator:
THE CRATERS REVEAL A TWIST.
505
00:27:24,810 --> 00:27:27,411
THE CARBON THAT MAKES
MERCURY SO DARK
506
00:27:27,413 --> 00:27:30,347
HAD BEEN THERE ALL ALONG
507
00:27:30,349 --> 00:27:34,151
AS PART OF THE MATERIAL
THAT FIRST FORMED THE PLANET.
508
00:27:34,153 --> 00:27:39,023
♪♪
509
00:27:39,025 --> 00:27:41,892
WHEN YOUNG MERCURY IS HIT,
PARTS OF THE SURFACE
510
00:27:41,894 --> 00:27:46,597
ARE TRANSFORMED
INTO AN OCEAN OF MOLTEN ROCK.
511
00:27:46,599 --> 00:27:50,401
AS THIS MAGMA OCEAN COOLS,
IT SOLIDIFIES,
512
00:27:50,403 --> 00:27:54,505
FORMING A CRUST,
513
00:27:54,507 --> 00:27:58,075
AND SITTING ON TOP
OF THIS CRUST, GRAPHITE,
514
00:27:58,077 --> 00:28:02,246
THE CRYSTALLIZED FORM OF CARBON.
515
00:28:02,248 --> 00:28:03,914
Durda: CARBON CONTAINING
MINERALS LIKE GRAPHITE
516
00:28:03,916 --> 00:28:05,516
WOULD END UP NEAR
THE SURFACE OF MERCURY
517
00:28:05,518 --> 00:28:07,117
AT THE TOP OF THAT MAGMA OCEAN
518
00:28:07,119 --> 00:28:10,320
BECAUSE THOSE MINERALS
ARE A LOT LESS DENSE
519
00:28:10,322 --> 00:28:12,556
THAN THE CONVENTIONAL
ROCKY MINERALS
520
00:28:12,558 --> 00:28:13,624
THAT CONTAIN A LOT OF,
YOU KNOW,
521
00:28:13,626 --> 00:28:15,659
IRON AND NICKEL.
THOSE ARE MORE DENSE.
522
00:28:15,661 --> 00:28:17,895
THEY TEND TO SINK TO
THE CENTER OF THE PLANET.
523
00:28:17,897 --> 00:28:19,963
THOSE LIGHTER ELEMENTS
LIKE GRAPHITE
524
00:28:19,965 --> 00:28:21,665
WOULD TEND TO FLOAT TO THE TOP.
525
00:28:24,236 --> 00:28:26,470
Narrator: BUT VOLCANISM COVERS
THE PLANET
526
00:28:26,472 --> 00:28:29,740
IN NEW BASALT LAVA FLOWS
527
00:28:29,742 --> 00:28:32,443
COMING FROM DEEP
BELOW THE SURFACE
528
00:28:32,445 --> 00:28:35,946
WHERE THE CARBON DIDN'T SINK,
529
00:28:35,948 --> 00:28:40,751
AND THIS LAVA BURIES
MERCURY'S ANCIENT CRUST.
530
00:28:40,753 --> 00:28:42,720
OVER TIME, THAT CARBON
IS COVERED UP
531
00:28:42,722 --> 00:28:44,621
BY SUBSEQUENT LAVA FLOWS,
532
00:28:44,623 --> 00:28:46,056
BUT THERE WAS
THIS LAYER OF CARBON
533
00:28:46,058 --> 00:28:48,525
WAITING UNDERNEATH
THE SURFACE OF MERCURY,
534
00:28:48,527 --> 00:28:52,496
AND AS OBJECTS HIT MERCURY AND
GOUGED OUT HOLES IN THE SURFACE,
535
00:28:52,498 --> 00:28:57,234
IT EXPOSED THIS HIDDEN
DARKER LAYER UNDERNEATH.
536
00:28:57,236 --> 00:29:00,671
Narrator: COVERED BY A BILLION
YEARS OF LAVA FLOWS
537
00:29:00,673 --> 00:29:04,341
AND REVEALED
BY GIANT IMPACT EVENTS,
538
00:29:04,343 --> 00:29:05,976
ONE THIS IS FOR SURE --
539
00:29:05,978 --> 00:29:11,381
MERCURY'S SURFACE HAS BEEN
A TRULY HELLISH LANDSCAPE.
540
00:29:11,383 --> 00:29:13,250
IMAGINE THAT WE'RE ON
THE SURFACE OF MERCURY
541
00:29:13,252 --> 00:29:15,285
DURING THAT FIRST BILLION YEARS
542
00:29:15,287 --> 00:29:19,456
WHEN VOLCANISM WAS VERY ACTIVE.
543
00:29:19,458 --> 00:29:23,227
RAINING DOWN FROM THE SKY,
ALL THESE COMETS AND METEORITES
544
00:29:23,229 --> 00:29:26,630
JUST PELTING
THE SURFACE MERCILESSLY,
545
00:29:26,632 --> 00:29:28,932
AND THEN, BENEATH YOUR FEET,
546
00:29:28,934 --> 00:29:33,137
THERE'LL BE ALL THIS
MOLTEN ROCK BUBBLING UP.
547
00:29:33,139 --> 00:29:36,006
REALLY AN AWFUL PLACE TO BE
548
00:29:36,008 --> 00:29:38,041
IN THAT FIRST BILLION YEARS
ON MERCURY.
549
00:29:40,312 --> 00:29:42,179
Narrator:
OVER BILLIONS OF YEARS,
550
00:29:42,181 --> 00:29:48,018
COMETS AND VOLCANISM RESHAPED
THE SURFACE OF MERCURY,
551
00:29:48,020 --> 00:29:52,055
AND THIS PLANET
IS NOT DONE YET.
552
00:29:52,057 --> 00:29:57,928
SCIENTISTS FIND GIANT CLIFFS
STRETCHING HUNDREDS OF MILES.
553
00:29:57,930 --> 00:30:01,832
IT SEEMS MERCURY IS ALIVE.
554
00:30:09,108 --> 00:30:13,710
♪♪
555
00:30:13,712 --> 00:30:18,882
Narrator: MERCURY, A SMALL,
DARK WORLD COVERED IN CRATERS
556
00:30:18,884 --> 00:30:22,052
AND ANCIENT LAVA FLOWS,
557
00:30:22,054 --> 00:30:26,190
BUT SCIENTISTS FIND
SOMETHING ELSE ON THE SURFACE.
558
00:30:26,192 --> 00:30:32,429
TOWERING CLIFFS AROUND 2 MILES
HIGH KNOWN AS FAULT SCARPS.
559
00:30:32,431 --> 00:30:34,398
Thaller: IF YOU WERE WALKING
ALONG ONE OF THESE SCARPS
560
00:30:34,400 --> 00:30:35,866
ON THE SURFACE OF MERCURY,
561
00:30:35,868 --> 00:30:37,668
THERE WOULD BE
THIS GIANT CLIFF FACE
562
00:30:37,670 --> 00:30:41,038
THAT WOULD GO ON FOR MILES
AND MILES WELL OVER THE HORIZON,
563
00:30:41,040 --> 00:30:44,975
SO YOU WOULD BE WALKING NEXT
TO AN ALMOST ENDLESS CLIFF.
564
00:30:44,977 --> 00:30:50,080
Narrator: THE LARGEST FAULT
SCARP IS ENTERPRISE RUPES.
565
00:30:50,082 --> 00:30:54,585
AT OVER 600 MILES LONG, IT WOULD
SPAN THE WIDTH OF TEXAS.
566
00:30:56,422 --> 00:30:59,323
WE SEE FAULT SCARPS ON EARTH,
567
00:30:59,325 --> 00:31:01,925
EVIDENCE OF TECTONIC ACTIVITY.
568
00:31:04,463 --> 00:31:07,865
PLANETARY SCIENTIST
JANI RADEBAUGH VISITS A SCARP
569
00:31:07,867 --> 00:31:10,133
IN DEATH VALLEY
TO DEMONSTRATE.
570
00:31:12,304 --> 00:31:14,972
Radebaugh: THIS LONG, STRAIGHT
LINE OF SHADOWS BEHIND ME
571
00:31:14,974 --> 00:31:18,075
FORMED BECAUSE DEATH VALLEY
IS STILL SPREADING APART
572
00:31:18,077 --> 00:31:19,810
AND THE MATERIAL ON THE RIGHT
573
00:31:19,812 --> 00:31:22,012
HAS DROPPED DOWN FROM
THE MATERIAL ON THE LEFT
574
00:31:22,014 --> 00:31:25,082
AND LEFT A REALLY
SHARP FAULT SCARP.
575
00:31:25,084 --> 00:31:26,817
THE FAULT SCARP
YOU SEE BEHIND ME,
576
00:31:26,819 --> 00:31:31,054
AND THE ONES WE SEE ON MERCURY,
ARE FORMED BY TECTONIC FORCES,
577
00:31:31,056 --> 00:31:32,990
AND THIS JUST MEANS
THAT THERE ARE FORCES
578
00:31:32,992 --> 00:31:34,625
INSIDE OF THE PLANETS,
579
00:31:34,627 --> 00:31:38,595
AND THOSE FORCES CAUSE
BREAKS IN THE CRUST.
580
00:31:38,597 --> 00:31:41,531
♪♪
581
00:31:41,533 --> 00:31:44,735
Narrator: ON EARTH, TRANSFER
OF HEAT FROM THE MANTLE
582
00:31:44,737 --> 00:31:49,273
DRIVES THE MOVEMENT
OF CONTINENTAL PLATES.
583
00:31:49,275 --> 00:31:52,509
THESE PLATES MOVE AROUND
THE SURFACE OF THE PLANET,
584
00:31:52,511 --> 00:31:54,211
INTERACTING WITH EACH OTHER...
585
00:31:54,213 --> 00:31:57,514
♪♪
586
00:31:57,516 --> 00:32:00,183
...BUILDING MOUNTAINS,
RIFT VALLEYS,
587
00:32:00,185 --> 00:32:01,618
EVEN CONTINENTS.
588
00:32:01,620 --> 00:32:04,488
♪♪
589
00:32:04,490 --> 00:32:06,590
DO THE FAULT SCARPS
ON MERCURY
590
00:32:06,592 --> 00:32:10,327
MEAN IT ALSO HAS
PLATE TECTONICS?
591
00:32:10,329 --> 00:32:12,362
WHEN YOU THINK ABOUT
THE EARTH'S PLATE TECTONICS,
592
00:32:12,364 --> 00:32:14,431
THERE ARE MULTIPLE
PLATES OF ROCK
593
00:32:14,433 --> 00:32:18,402
THAT ARE MOVING AROUND
ON A LAYER OF LIQUID ROCK BELOW.
594
00:32:18,404 --> 00:32:21,405
MERCURY, HOWEVER, HAS BASICALLY
JUST ONE BIG PLATE.
595
00:32:21,407 --> 00:32:24,441
THERE'S A SOLID SURFACE
THAT COVERS THE ENTIRE PLANET.
596
00:32:26,912 --> 00:32:31,915
Narrator: MERCURY HAS A
DIFFERENT KIND OF TECTONICS.
597
00:32:31,917 --> 00:32:35,819
OVER BILLIONS OF YEARS,
ITS LIQUID CORE COOLS,
598
00:32:37,856 --> 00:32:43,961
AND AS THE INTERIOR COOLS, THE
PLANET SHRINKS AROUND 9 MILES.
599
00:32:43,963 --> 00:32:46,330
WHEN SOMETHING COOLS,
IT CONTRACTS.
600
00:32:46,332 --> 00:32:49,499
IT ACTUALLY BECOMES SMALLER.
601
00:32:49,501 --> 00:32:54,071
Narrator:
BECAUSE OF THIS CONTRACTION,
THE ROCK AND THE CRUST WRINKLES,
602
00:32:54,073 --> 00:32:56,740
CREATING MASSIVE SCARPS.
603
00:32:56,742 --> 00:32:59,609
YOU CAN IMAGINE, IF YOU TAKE
A BALLOON AND COVER IT IN MUD
604
00:32:59,611 --> 00:33:01,111
AND LET THE MUD DRY,
605
00:33:01,113 --> 00:33:03,080
AND THEN YOU LET A LITTLE BIT
OF AIR OUT OF THE BALLOON,
606
00:33:03,082 --> 00:33:04,314
WHAT'S GOING TO HAPPEN?
607
00:33:04,316 --> 00:33:05,983
WELL, THAT MUD IS GOING TO
TRY TO CONTRACT AS WELL,
608
00:33:05,985 --> 00:33:09,720
BUT IT CAN'T, AND SO IT'LL CRACK
AND SNAP LIKE THAT,
609
00:33:09,722 --> 00:33:12,756
AND YOU'LL GET THESE
THRUST FAULTS, THESE SCARPS.
610
00:33:14,660 --> 00:33:17,928
Narrator: BUT FOR MERCURY,
THE STORY DOESN'T END THERE.
611
00:33:20,132 --> 00:33:22,966
WE UNDERSTAND THAT THE LARGE
FAULT SCARPS ON MERCURY FORMED
612
00:33:22,968 --> 00:33:25,435
A LONG TIME AGO
WHEN THE PLANET WAS COOLING
613
00:33:25,437 --> 00:33:28,171
AND THE CRUST WAS
SHRINKING AND BUCKLING,
614
00:33:28,173 --> 00:33:31,241
BUT MORE RECENTLY, MESSENGER
HAS COME VERY CLOSE TO MERCURY
615
00:33:31,243 --> 00:33:34,911
AND HAS FOUND REALLY
SMALL FAULT SCARPS.
616
00:33:34,913 --> 00:33:37,381
Narrator: UNLIKE THE GIANT
MILE-HIGH SCARPS,
617
00:33:37,383 --> 00:33:41,918
THESE SMALL ONES ARE LESS
THAN 200 FEET IN LENGTH.
618
00:33:41,920 --> 00:33:43,553
WHAT DOES THIS MEAN?
619
00:33:43,555 --> 00:33:46,990
THESE ARE SMALL SCARPS,
AND THE THING IS,
620
00:33:46,992 --> 00:33:48,725
IF THOSE WERE REALLY OLD,
621
00:33:48,727 --> 00:33:50,460
IMPACTS WOULD HAVE ERASED THEM,
622
00:33:50,462 --> 00:33:53,430
AND SO THESE SHOULD BE
LONG GONE OFF THE SURFACE.
623
00:33:53,432 --> 00:33:55,399
SO THAT MEANS THAT
THEY'RE RECENT.
624
00:33:55,401 --> 00:33:56,400
THEY'RE NEW.
625
00:33:56,402 --> 00:33:58,035
RIGHT NOW, MERCURY
HAS THE RECORD
626
00:33:58,037 --> 00:34:01,038
OF BEING THE SMALLEST OFFICIAL
PLANET IN THE SOLAR SYSTEM,
627
00:34:01,040 --> 00:34:04,408
BUT IS IT POSSIBLE THE SMALLEST
PLANET IS STILL SHRINKING?
628
00:34:06,412 --> 00:34:10,113
Narrator: THROUGHOUT ITS LIFE,
MERCURY HAS BEEN BOMBARDED.
629
00:34:12,184 --> 00:34:17,587
IMPACTS HAVE CRATERED
THE LARGE, OLD FAULT SCARPS.
630
00:34:17,589 --> 00:34:22,793
THE SMALL SCARPS SHOULD BE
COVERED IN IMPACT SCARS AS WELL,
631
00:34:22,795 --> 00:34:28,031
BUT THEY'RE PRISTINE, WHICH
MEANS THAT THEY'RE YOUNG,
632
00:34:28,033 --> 00:34:33,203
AND THAT MEANS MERCURY
IS STILL SHRINKING.
633
00:34:33,205 --> 00:34:36,373
MERCURY IS ACTUALLY
STILL TECTONICALLY ACTIVE.
634
00:34:36,375 --> 00:34:37,774
SO THE EARTH IS NO LONGER
635
00:34:37,776 --> 00:34:40,444
THE ONLY TECTONICALLY ACTIVE
PLANET IN THE SOLAR SYSTEM.
636
00:34:40,446 --> 00:34:43,180
WE'VE SEEN THAT MERCURY
HAS A SURPRISING HISTORY.
637
00:34:43,182 --> 00:34:46,383
THE THING IS, THE PLANET
ITSELF IS STILL COOLING,
638
00:34:46,385 --> 00:34:49,786
STILL CONTRACTING, EVEN AFTER
ALL OF THESE BILLIONS
639
00:34:49,788 --> 00:34:52,689
OF YEARS AFTER IT FORMED.
THAT'S AMAZING.
640
00:34:52,691 --> 00:34:54,858
AT FIRST, IT MAY SEEM
THAT YOU COULD WRITE THIS OFF
641
00:34:54,860 --> 00:34:58,028
AS A DULL, LITTLE, DEAD ROCK
CLOSE TO THE SUN,
642
00:34:58,030 --> 00:35:01,031
BUT MERCURY HAS A STORY TO TELL.
643
00:35:01,033 --> 00:35:04,367
Narrator: A STORY THAT CONTINUES
TO THIS DAY
644
00:35:04,369 --> 00:35:07,437
DESPITE EVERYTHING THE
PLANET HAS GONE THROUGH.
645
00:35:09,808 --> 00:35:11,775
Plait: MERCURY HAS HAD IT PRETTY
ROUGH. IT'S HAD A TOUGH TIME
646
00:35:11,777 --> 00:35:14,377
OVER THE HISTORY
OF THE SOLAR SYSTEM.
647
00:35:14,379 --> 00:35:16,546
IT HAS BEEN TOSSED
AROUND BY PLANETS.
648
00:35:16,548 --> 00:35:19,883
IT HAS BEEN IMPACTED BY
GIGANTIC ASTEROIDS AND COMETS.
649
00:35:19,885 --> 00:35:21,051
IT IS SHRINKING.
650
00:35:21,053 --> 00:35:23,086
IT'S BOMBARDED
BY SOLAR RADIATION.
651
00:35:23,088 --> 00:35:25,188
THAT WOULD TICK ANYBODY OFF,
652
00:35:25,190 --> 00:35:27,757
AND IT'S ENTIRELY POSSIBLE
THAT IN THE FUTURE,
653
00:35:27,759 --> 00:35:30,093
MERCURY WILL GET ITS REVENGE.
654
00:35:32,264 --> 00:35:35,866
Narrator: MERCURY COULD HAVE
A FINAL TRICK UP ITS SLEEVE,
655
00:35:35,868 --> 00:35:39,469
ONE THAT THREATENS
OUR VERY EXISTENCE.
656
00:35:47,846 --> 00:35:53,850
♪♪
657
00:35:53,852 --> 00:35:57,254
Narrator: MESSENGER COMPLETES
ITS FINAL ORBIT OF MERCURY...
658
00:35:59,591 --> 00:36:03,627
...AND CRASHES INTO
THE PLANET'S SURFACE,
659
00:36:03,629 --> 00:36:05,996
A FITTING CONCLUSION FOR A WORLD
660
00:36:05,998 --> 00:36:08,498
WITH A HISTORY OF IMPACTS.
661
00:36:08,500 --> 00:36:10,967
AT THE END OF
THE MESSENGER MISSION,
662
00:36:10,969 --> 00:36:15,238
OUR VIEW OF MERCURY HAD
BEEN SUBSTANTIALLY CHANGED.
663
00:36:15,240 --> 00:36:17,908
WE SUDDENLY HAD A PICTURE
OF A COMPLETE WORLD,
664
00:36:17,910 --> 00:36:20,844
A PLACE THAT HAD HELLISHLY
HIGH TEMPERATURES
665
00:36:20,846 --> 00:36:23,113
AND YET ICES OF WATER,
666
00:36:23,115 --> 00:36:25,215
AN EVOLUTION THAT DIDN'T MATCH
667
00:36:25,217 --> 00:36:29,252
THAT OF ANY OF ITS
SIBLING PLANETS.
668
00:36:29,254 --> 00:36:34,391
Narrator:
COULD MERCURY'S FUTURE BE JUST
AS UNPREDICTABLE AS ITS PAST?
669
00:36:34,393 --> 00:36:38,428
RIGHT NOW, THE FUTURE
OF MERCURY LOOKS BRIGHT --
670
00:36:38,430 --> 00:36:42,632
VERY, VERY BRIGHT.
671
00:36:42,634 --> 00:36:46,336
Narrator: IT'S ALL THANKS TO
MERCURY'S MASSIVE NEIGHBOR.
672
00:36:46,338 --> 00:36:48,905
Thaller: THE SUN IS A GIANT BALL
OF HYDROGEN AND HELIUM,
673
00:36:48,907 --> 00:36:52,008
AND IN THE CORE, THERE'S
A NUCLEAR FUSION REACTION,
674
00:36:52,010 --> 00:36:55,612
BUT OVER TIME, THE FUEL THAT
THE SUN RUNS ON, HYDROGEN,
675
00:36:55,614 --> 00:36:57,080
WILL BEGIN TO DIE OUT.
676
00:36:57,082 --> 00:36:59,449
IT WILL ACTUALLY BURN
THROUGH ALL OF ITS FUEL.
677
00:36:59,451 --> 00:37:03,019
WHEN THAT HAPPENS,
IN THE FINAL PHASES OF ITS LIFE,
678
00:37:03,021 --> 00:37:06,056
THE SUN WILL BLOAT UP
TO BECOME A RED GIANT STAR,
679
00:37:06,058 --> 00:37:08,692
HUNDREDS OF TIMES THE SIZE
THAT IT CURRENTLY IS.
680
00:37:10,295 --> 00:37:15,198
Narrator: AS THE SUN EXPANDS,
IT WILL ENGULF MERCURY.
681
00:37:15,200 --> 00:37:18,635
BEING ON THE SURFACE OF MERCURY
IS BAD ENOUGH RIGHT NOW.
682
00:37:18,637 --> 00:37:21,137
NOW PUT IT INSIDE OF A STAR.
683
00:37:21,139 --> 00:37:24,941
♪♪
684
00:37:24,943 --> 00:37:26,943
ALL OF THAT HEAT
BOMBARDING THE PLANET
685
00:37:26,945 --> 00:37:29,479
WILL LITERALLY BOIL IT AWAY.
686
00:37:31,550 --> 00:37:34,651
Narrator: BUT IS THERE A CHANCE
THAT MERCURY COULD ESCAPE
687
00:37:34,653 --> 00:37:37,687
THIS ROASTING?
688
00:37:37,689 --> 00:37:39,589
THERE'S NOT JUST
THE EVOLUTION OF THE SUN
689
00:37:39,591 --> 00:37:41,157
THAT WE HAVE TO TAKE
INTO ACCOUNT.
690
00:37:41,159 --> 00:37:44,294
THE PLANETS THEMSELVES
AND THEIR ORBITS ARE EVOLVING.
691
00:37:44,296 --> 00:37:46,863
THEY LOOK STABLE,
BUT OVER LONG TIME PERIODS,
692
00:37:46,865 --> 00:37:48,465
THEY CAN CHANGE DRASTICALLY.
693
00:37:48,467 --> 00:37:52,535
♪♪
694
00:37:52,537 --> 00:37:55,872
Narrator: THE SUN EXERTS THE
STRONGEST GRAVITATIONAL PULL
695
00:37:55,874 --> 00:37:59,309
OF ANY OBJECT
IN THE SOLAR SYSTEM.
696
00:37:59,311 --> 00:38:03,146
IT'S WHY THE PLANETS ORBIT IT,
697
00:38:03,148 --> 00:38:07,284
BUT PLANETS CAN ALSO
PULL ON EACH OTHER.
698
00:38:07,286 --> 00:38:10,754
MERCURY IS TINY,
MAKING IT MOST VULNERABLE
699
00:38:10,756 --> 00:38:14,491
TO THESE GRAVITATIONAL TUGS.
700
00:38:14,493 --> 00:38:19,963
AFTER THE SUN, THE NEXT
BIGGEST OBJECT IS JUPITER.
701
00:38:19,965 --> 00:38:22,432
Plait: WE CAN TAKE COMPUTER
MODELS AND SIMULATE
702
00:38:22,434 --> 00:38:24,734
MERCURY'S ORBIT
AS IT'S AFFECTED BY JUPITER
703
00:38:24,736 --> 00:38:26,703
TO SEE WHAT HAPPENS TO MERCURY,
704
00:38:26,705 --> 00:38:28,071
AND DEPENDING
ON INITIAL CONDITIONS,
705
00:38:28,073 --> 00:38:29,839
A LOT OF DIFFERENT
THINGS CAN HAPPEN.
706
00:38:29,841 --> 00:38:33,176
BUT IN SOME PERCENTAGE
OF THE MODELS, WHAT CAN HAPPEN
707
00:38:33,178 --> 00:38:36,579
IS MERCURY'S ORBIT
CHANGES SO MUCH
708
00:38:36,581 --> 00:38:38,448
THAT IT ACTUALLY SWINGS OUT
709
00:38:38,450 --> 00:38:41,918
AND CAN REACH THE ORBIT
OF THE EARTH.
710
00:38:41,920 --> 00:38:46,189
♪♪
711
00:38:46,191 --> 00:38:50,660
Narrator:
JUPITER IS OFTEN SEEN AS THE
BULLY OF THE SOLAR SYSTEM.
712
00:38:50,662 --> 00:38:53,930
HERE, IT'S MERCURY'S BODYGUARD.
713
00:38:53,932 --> 00:38:56,366
OVER TIME, ITS
GRAVITATIONAL INFLUENCE
714
00:38:56,368 --> 00:39:01,504
STRETCHES MERCURY'S ORBIT
OUT FARTHER AND FARTHER,
715
00:39:01,506 --> 00:39:04,341
AND THE LITTLE WORLD ESCAPES
THE SUN'S CLUTCHES
716
00:39:04,343 --> 00:39:08,078
LONG BEFORE IT EXPANDS
TO A RED GIANT.
717
00:39:10,148 --> 00:39:14,384
BUT THIS TALE
HAS ONE FINAL TWIST.
718
00:39:14,386 --> 00:39:18,688
Plait:
IT'S EASY TO DISMISS MERCURY
IN THE PANTHEON OF PLANETS,
719
00:39:18,690 --> 00:39:22,192
BUT IGNORE IT AT YOUR PERIL
BECAUSE THERE MAY COME A DAY
720
00:39:22,194 --> 00:39:27,664
WHEN MERCURY MAKES ITS PRESENCE
VERY WELL KNOWN INDEED.
721
00:39:27,666 --> 00:39:30,667
Lanza:
I'D LIKE TO THINK THAT MERCURY
DOES NOT BEAR THE SOLAR SYSTEM
722
00:39:30,669 --> 00:39:33,103
ANY ILL WILL FOR
ALL THE HARD TIME
723
00:39:33,105 --> 00:39:36,106
IT'S BEEN GIVEN OVER
THE LAST 4.5 BILLION YEARS,
724
00:39:36,108 --> 00:39:40,443
BUT, YOU KNOW, THAT'S A LONG
TIME TO BUILD UP A GRUDGE.
725
00:39:40,445 --> 00:39:42,579
Thaller: MERCURY HAS HAD
SUCH A DIFFICULT PAST.
726
00:39:42,581 --> 00:39:46,082
IT'S BEEN BEAT ON BY THE SUN,
COLLIDED WITH OTHER PLANETS.
727
00:39:46,084 --> 00:39:48,918
NOW MERCURY COULD COME IN AND
START WREAKING HAVOC WITH US,
728
00:39:48,920 --> 00:39:51,755
SO MAYBE WE CAN THINK OF THIS
AS SORT OF MERCURY'S REVENGE.
729
00:39:53,792 --> 00:39:55,492
Narrator: BILLIONS OF YEARS AGO,
730
00:39:55,494 --> 00:39:57,460
EARTH COULD WELL HAVE COLLIDED
731
00:39:57,462 --> 00:40:00,130
WITH THE YOUNG MERCURY,
732
00:40:00,132 --> 00:40:02,232
CHANGING MERCURY FOREVER.
733
00:40:02,234 --> 00:40:06,703
♪♪
734
00:40:06,705 --> 00:40:11,141
AND NOW, IT COMES FACE-TO-FACE
WITH EARTH ONCE AGAIN...
735
00:40:11,143 --> 00:40:14,978
♪♪
736
00:40:14,980 --> 00:40:20,483
...SMASHING INTO OUR PLANET
IN ONE, FINAL IMPACT,
737
00:40:20,485 --> 00:40:24,220
WIPING OUT ANY TRACE
OF THE WORLD WE KNOW AND LOVE.
738
00:40:26,024 --> 00:40:28,057
IT WOULD MELT OUR ENTIRE CRUST.
739
00:40:28,059 --> 00:40:31,461
IT WOULD WIPE OUT ALL LIFE
ON OUR PLANET.
740
00:40:31,463 --> 00:40:35,899
♪♪
741
00:40:35,901 --> 00:40:39,369
Narrator: SO HOW WORRIED SHOULD
WE BE ABOUT THIS THREAT?
742
00:40:39,371 --> 00:40:42,005
THE ODDS OF THIS HAPPENING
AREN'T THAT HIGH,
743
00:40:42,007 --> 00:40:43,940
AND IF IT HAPPENS,
IT'S GOING TO HAPPEN
744
00:40:43,942 --> 00:40:45,575
BILLIONS OF YEARS IN THE FUTURE.
745
00:40:45,577 --> 00:40:49,279
SO I'M NOT TERRIBLY WORRIED
ABOUT IT ON A PERSONAL SCALE,
746
00:40:49,281 --> 00:40:53,483
BUT AS AN ASTRONOMER AND AS
A SCIENTIST, THAT'S FASCINATING.
747
00:40:53,485 --> 00:40:57,854
♪♪
748
00:40:57,856 --> 00:41:00,356
Narrator: MERCURY MAY CONTINUE
TO SURPRISE US,
749
00:41:00,358 --> 00:41:03,059
EVEN TO ITS DYING DAY,
750
00:41:03,061 --> 00:41:09,999
A WORLD BORN IN FIRE THAT
MIGHT ALSO GO DOWN IN FLAMES.
751
00:41:10,001 --> 00:41:12,001
BUT THE FACT THAT
IT MADE IT THIS FAR
752
00:41:12,003 --> 00:41:15,271
IS NOTHING SHORT OF REMARKABLE.
753
00:41:15,273 --> 00:41:17,874
LIVING IN THE TOUGHEST
NEIGHBORHOOD IMAGINABLE,
754
00:41:17,876 --> 00:41:22,145
MERCURY HAS MADE IT THROUGH
THE HISTORY OF THE SOLAR SYSTEM,
755
00:41:22,147 --> 00:41:25,648
BEATEN, BUT NOT BROKEN.
756
00:41:25,650 --> 00:41:28,785
MERCURY IS ONE OF THE SOLAR
SYSTEM'S GREAT SURVIVORS.
757
00:41:28,787 --> 00:41:30,753
DESPITE ALL OF THE THINGS
THAT HAPPENED TO IT,
758
00:41:30,755 --> 00:41:33,256
IT'S STILL HANGING IN THERE.
759
00:41:33,258 --> 00:41:35,358
IT'S BEEN SUBJECT TO
THE HARSHEST ENVIRONMENT
760
00:41:35,360 --> 00:41:36,559
IN THE SOLAR SYSTEM,
761
00:41:36,561 --> 00:41:38,895
AND IT'S STILL AROUND.
762
00:41:38,897 --> 00:41:42,765
Lanza:
MERCURY, YOU KNOW, HAS BEEN
ATTACKED FROM ALL SIDES, RIGHT?
763
00:41:42,767 --> 00:41:44,667
IT'S BEEN ROASTED BY THE SUN.
764
00:41:44,669 --> 00:41:48,872
IT'S BEEN PUMMELED BY IMPACTORS,
AND YET IT'S STILL THERE,
765
00:41:48,874 --> 00:41:50,573
STILL BEING A GREAT PLANET,
766
00:41:50,575 --> 00:41:54,210
THIS PLUCKY, LITTLE SURVIVOR
WHO'S STILL ORBITING
767
00:41:54,212 --> 00:41:56,346
DESPITE EVERYTHING
IT'S GONE THROUGH.
768
00:42:01,586 --> 00:42:01,651
THIS PLUCKY, LITTLE SURVIVOR
WHO'S STILL ORBITING
69071
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