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SUB BY : DENI AUROR@
https://aurorarental.blogspot.com/
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For thousands of years,
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planet Mercury
has baffled astronomers,
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but now its secrets
have been revealed.
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It's a bizarre world
unlike any other.
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When you look at
the family of planets
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that make up our
solar system, you know,
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Mercury does seem to be
a little bit of a weirdo.
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This is one tough world,
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surviving brutal attacks
from comets, the Sun,
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and even other planets.
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You could see by
the surface of Mercury
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that it has a lot
of battle scars.
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The solar system
did not treat it well.
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And yet, this world
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has been brought to life
with water ice,
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volcanism,
and tectonic activity.
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If I had to describe
Mercury in a word,
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it would be "surprising."
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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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but Mercury has a story to tell.
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And this story could end
with Mercury threatening
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the very existence
of planet Earth.
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Ignore it at your peril
because there may come a day
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when Mercury makes its presence
very well known indeed.
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2015, the messenger spacecraft
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completes its final orbit
around planet Mercury.
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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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Our view of Mercury from before
and after the messenger probe
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is like having terrible
vision your whole life
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and then finally going
to the optometrist
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and getting glasses
that clear everything up,
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and it completely
opened our eyes
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to what this planet looks like.
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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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in a scorching environment
of lethal heat and radiation.
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Capturing images was
a monumental challenge
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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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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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and their optics would be
severely damaged.
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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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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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but when you start looking
a little bit closer at Mercury,
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you start to see some
really surprising similarities
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to Earth.
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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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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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because it's so close
to the Sun.
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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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in the solar system is,
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in some parts,
among the coldest,
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and I love that paradox
because I love the unexpected.
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Mercury is a world
of brutal extremes.
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The Sun-facing side is blasted
by solar radiation...
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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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Planetary scientist Dan Durda
demonstrates the effect
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this has using a campfire.
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So right now, with this jacket
on, holding the warmth in,
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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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a thermal insulator, that
helps make more uniform
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the temperature
of the entire planet.
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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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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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So could water ice
survive on the side of Mercury
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facing away from the Sun?
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The nighttime side is
very bitterly cold.
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If that were the end
of the story,
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you might be able to have,
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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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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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but at the bottom,
there's actually some ice.
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So if we measure a rock
that's been in the Sun,
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let's say this one, we can see
it's actually pretty warm.
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It's about 61 degrees
Fahrenheit,
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but if we aim, now, for the
bottom of this hollow,
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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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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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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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forever safe from the glare
of direct sunlight,
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because these craters
sit in a perfect spot.
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Mercury's axis doesn't tilt
very much compared to the Sun.
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The Earth's axis tilts
about 23 degrees,
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but Mercury is pretty much
straight up and down,
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and that means that as large
as the Sun is in the sky,
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there are craters on the poles
that sunlight never gets to.
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They're always cold.
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So the surface of
Mercury is heated
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and then cooled
as it moves around the Sun,
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but there are craters that are
always dark and always cold.
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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.
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The bottoms of these craters
are called cold traps
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because they're so cold
that any water
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that gets there stays
there basically forever.
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It can last literally
for billions of years.
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But where would it
have come from?
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It probably came from
comets and asteroids.
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Comets are giant chunks of ice.
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So if a comet hits Mercury,
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that's going to deliver
a lot of ice,
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and, in fact, we know
a lot of asteroids
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have ice on them as well.
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So both of these things
could deliver water to Mercury.
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Comets and asteroids
brought water ice
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to the innermost planets
of the solar system.
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This same water delivery system
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gave Earth the elements
needed for life.
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And though Mercury has
pockets of frozen water,
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the planet can never use it
to develop living organisms.
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What Mercury is really
showing us is that you can start
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with the same basic building
blocks for planets, right?
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You can have essentially
the same materials,
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but end up with very
different environments.
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Compared to the other planets,
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Mercury ended up as
the runt of the litter.
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But there's evidence
this wasn't always the case.
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Could this little world have
once been much, much bigger?
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We have theories for
how the planets first formed
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in our solar system,
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but Mercury just doesn't fit in.
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When you look at
the family of planets
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that make up our solar system,
you know,
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Mercury does seem to be
a little bit of a weirdo.
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On Earth, we have
a relatively small core
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and a thick mantle
and a thin crust.
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So you compare the core of the
Earth to the size of the Earth,
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it's relatively small.
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If you look at Mercury,
it's not that way at all.
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The core is absolutely huge
compared to the planet itself.
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Mercury's huge
iron core is surrounded
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by an unusually
thin mantle of rock.
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It just looks odd.
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It's funny.
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You don't expect to get
a core that large
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in a planet that small.
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It's almost as if Mercury lost
some of its mantle somewhere.
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I mean, maybe it left it
behind the couch.
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Who knows?
But it's gone now.
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But how can this
material just vanish?
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Mercury could be
the way it is now
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because it started as
a much larger planet
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and then something happened to
strip away the top layer of it,
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and the only way
we know how to do that
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on a planetary scale is
with planetary impacts.
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Picture the early solar system
when Mercury is still forming.
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It's completely different from
the little world we know now.
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Up to four times more massive,
twice the mass of Mars,
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but it orbits
in a shooting gallery.
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Impacts are inevitable,
and before long,
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an object the size of our moon
smashes into Mercury
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in a giant impact event.
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This is apocalyptic.
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This is the sweatiest
nightmare you can have.
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You're resurfacing
an entire planet.
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The energies are vast.
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One of these giant impacts
probably would have remelted it
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all the way through.
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What's going to remain
after it's done
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is completely different
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than what started
in the first place.
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It's hard to overstate just
how impactful these events are.
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Huge chunks of Mercury's mantle
are flung into space.
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The result?
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Two-thirds of its mass
are now made up by its core,
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but where did the rest of it go?
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Billions of years ago,
there was a planet
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that we will never know,
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a planet that was destroyed when
the current Mercury was formed.
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Is it possible that some of it
may still be out there?
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The lost mantle debris
could still exist
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in the innermost solar system.
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Scientists call these
hypothetical objects vulcanoids.
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Vulcanoids can be very valuable
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for understanding
the formation of Mercury
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because some of these vulcanoids
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may be pieces of
Mercury's missing mantle.
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00:13:23,210 --> 00:13:25,180
But in order to survive,
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these vulcanoids
would have to orbit
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on a gravitational tightrope.
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00:13:30,850 --> 00:13:33,420
You know, like this marshmallow,
vulcanoids exist
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in kind of a precarious
position in the solar system,
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a little too close to the fire,
a little too close to the Sun,
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00:13:41,930 --> 00:13:44,130
those objects actually
would vaporize away,
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kind of like that.
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00:13:47,870 --> 00:13:49,400
If you orbit too far
from the Sun,
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00:13:49,410 --> 00:13:51,410
you're going to approach
too closely to Mercury
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and have gravitational
encounters,
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00:13:53,280 --> 00:13:57,110
maybe get flung out of the solar
system or maybe just impact
247
00:13:57,110 --> 00:13:59,680
Mercury itself
and get eaten, if you will.
248
00:14:02,020 --> 00:14:04,090
But in-between
those two extremes,
249
00:14:04,090 --> 00:14:06,250
at just the right
distance from the Sun,
250
00:14:06,260 --> 00:14:08,260
a little closer
to the Sun than Mercury,
251
00:14:08,260 --> 00:14:10,490
but not so close
that you get fried,
252
00:14:10,490 --> 00:14:14,700
is this vulcanoid region where
objects in orbit around the Sun
253
00:14:14,700 --> 00:14:16,730
could remain
gravitationally stable
254
00:14:16,730 --> 00:14:18,900
over the entire age
of the solar system.
255
00:14:18,900 --> 00:14:21,840
That's the place to look
for this potential population
256
00:14:21,840 --> 00:14:24,210
of little asteroid-like objects.
257
00:14:26,740 --> 00:14:28,810
We know where they should be,
258
00:14:28,810 --> 00:14:31,810
but there's a problem.
259
00:14:31,820 --> 00:14:33,410
You may wonder why haven't
260
00:14:33,420 --> 00:14:35,920
we seen these vulcanoids
if they actually exist?
261
00:14:35,920 --> 00:14:38,420
If they're actually orbiting,
why don't we just look for them?
262
00:14:38,420 --> 00:14:42,190
Well, it's because they're
really close to the Sun.
263
00:14:42,190 --> 00:14:44,190
Unlike the asteroids
or the Kuiper belt objects
264
00:14:44,190 --> 00:14:46,890
where we're looking out
away from the Sun
265
00:14:46,900 --> 00:14:48,230
from our perspective
here on the Earth,
266
00:14:48,230 --> 00:14:50,870
we're looking out into
the dark nighttime sky,
267
00:14:50,870 --> 00:14:52,670
in the case of the vulcanoids,
we're looking for something
268
00:14:52,670 --> 00:14:54,340
very, very close to the Sun,
269
00:14:54,340 --> 00:14:57,370
in close to that really
brilliant light source.
270
00:14:59,180 --> 00:15:04,350
Our sun is around
900,000 miles across.
271
00:15:04,350 --> 00:15:08,120
Mercury is just 3,000.
272
00:15:08,120 --> 00:15:12,390
When our telescopes see Mercury
passing in front of the Sun,
273
00:15:12,390 --> 00:15:15,790
it's little more
than a pinprick.
274
00:15:15,790 --> 00:15:18,290
With vulcanoids, we're searching
for something
275
00:15:18,290 --> 00:15:22,800
thousands of times
smaller than Mercury.
276
00:15:22,800 --> 00:15:26,670
If vulcanoids exist,
they orbit in a blind spot,
277
00:15:29,110 --> 00:15:32,470
but scientists will keep
searching for them
278
00:15:32,480 --> 00:15:36,510
because they could be
the last surviving remnants
279
00:15:36,510 --> 00:15:39,350
of Mercury's lost mantle.
280
00:15:39,350 --> 00:15:42,980
If we were to discover
vulcanoids, that would offer us
281
00:15:42,990 --> 00:15:45,890
an entirely new population
of objects to study.
282
00:15:45,890 --> 00:15:48,890
This material could offer
some rather unique insight
283
00:15:48,890 --> 00:15:51,130
into the formation
of Mercury itself.
284
00:15:53,230 --> 00:15:58,100
A giant head-on impact
has been our best explanation
285
00:15:58,100 --> 00:16:00,270
for Mercury's weird structure.
286
00:16:04,910 --> 00:16:07,280
But now there's a
startling new theory
287
00:16:07,280 --> 00:16:09,480
for Mercury's missing mantle.
288
00:16:11,310 --> 00:16:15,450
It was stolen,
but who is the thief?
289
00:16:32,230 --> 00:16:35,330
For years,
we assumed that Mercury lost
290
00:16:35,330 --> 00:16:39,170
most of its mantle
in a giant head-on collision.
291
00:16:43,740 --> 00:16:47,540
But the messenger spacecraft
turned everything on its head.
292
00:16:49,150 --> 00:16:50,910
One of the exciting things
that we've learned
293
00:16:50,920 --> 00:16:52,150
about Mercury recently
294
00:16:52,150 --> 00:16:53,920
by sending probes
to study its surface
295
00:16:53,920 --> 00:16:55,650
is that its surface
is littered with material
296
00:16:55,650 --> 00:16:58,120
that we didn't think
should be there,
297
00:16:58,120 --> 00:17:00,860
things that we'd call volatiles.
298
00:17:00,860 --> 00:17:05,390
The volatiles are chemical
elements like potassium.
299
00:17:05,400 --> 00:17:08,060
They're called volatile...
300
00:17:08,070 --> 00:17:12,070
Because they evaporate
easily in high temperatures,
301
00:17:12,070 --> 00:17:17,940
just the sorts of temperatures
generated by a giant impact.
302
00:17:17,940 --> 00:17:20,040
If I had to describe
Mercury in a word,
303
00:17:20,040 --> 00:17:22,550
it would be "surprising."
304
00:17:22,550 --> 00:17:26,080
The idea was that a smaller
object ran into Mercury
305
00:17:26,080 --> 00:17:27,750
and knocked off material.
306
00:17:27,750 --> 00:17:30,650
Well, that actually would work
to make it lose material,
307
00:17:30,660 --> 00:17:32,860
but it would also generate
a lot of heat,
308
00:17:32,860 --> 00:17:35,620
and because of that, the
volatile materials on Mercury
309
00:17:35,630 --> 00:17:37,430
would also have been lost.
310
00:17:37,430 --> 00:17:39,400
But today, we see that
they're still there.
311
00:17:39,400 --> 00:17:43,830
So it meant that most of the
basic scenarios that have been
312
00:17:43,840 --> 00:17:47,170
laid out for how Mercury was
assembled had been disproven.
313
00:17:49,240 --> 00:17:51,510
We had to go back
to the drawing board
314
00:17:51,510 --> 00:17:54,180
and rethink how
Mercury was assembled
315
00:17:54,180 --> 00:17:56,810
and how Mercury evolved.
316
00:17:56,810 --> 00:17:59,720
How did Mercury lose its mantle
317
00:17:59,720 --> 00:18:02,790
but retain these volatiles?
318
00:18:02,790 --> 00:18:05,020
Mercury is like
a detective case.
319
00:18:05,020 --> 00:18:06,990
We have the body.
We have some clues,
320
00:18:06,990 --> 00:18:09,730
but we really have to
piece it together.
321
00:18:09,730 --> 00:18:12,330
Planetary scientist Erik Asphaug
322
00:18:12,330 --> 00:18:14,930
tackles this giant riddle.
323
00:18:14,930 --> 00:18:16,430
The original idea was that
324
00:18:16,430 --> 00:18:19,840
Mercury was hit by something
smaller than itself.
325
00:18:19,840 --> 00:18:22,200
But whatever process
made Mercury
326
00:18:22,210 --> 00:18:25,610
somehow preserved
all these volatiles
327
00:18:25,610 --> 00:18:28,710
that should have
vaporized and gone.
328
00:18:28,710 --> 00:18:32,150
Erik has a bold alternative,
329
00:18:32,150 --> 00:18:35,020
a hit-and-run collision.
330
00:18:35,020 --> 00:18:37,490
In the hit-and-run collision
idea, you actually have
331
00:18:37,490 --> 00:18:40,260
Mercury hitting something
bigger than itself
332
00:18:40,260 --> 00:18:43,060
without losing
all of its volatiles.
333
00:18:45,160 --> 00:18:49,230
Hitting something
bigger may sound even worse,
334
00:18:49,230 --> 00:18:51,870
but it all depends
on how you hit it.
335
00:18:53,770 --> 00:18:59,070
In the early solar system,
there were a lot of players,
336
00:18:59,080 --> 00:19:03,080
and just like a hockey match,
things got brutal.
337
00:19:05,080 --> 00:19:09,150
You would have had planetesimals
growing through collisions.
338
00:19:09,150 --> 00:19:11,250
The bigger objects
would have dominated
339
00:19:11,260 --> 00:19:14,120
because not only are they
running into smaller objects,
340
00:19:14,130 --> 00:19:17,030
they're drawing them
to themselves gravitationally,
341
00:19:17,030 --> 00:19:20,230
and two objects will sweep up
most of the matter.
342
00:19:20,230 --> 00:19:23,400
Those two objects
became Venus and Earth.
343
00:19:24,670 --> 00:19:26,770
Earth and Venus
are the enforcers
344
00:19:26,770 --> 00:19:29,440
of the inner solar system,
345
00:19:29,440 --> 00:19:31,240
wiping out most
of the competition.
346
00:19:31,240 --> 00:19:34,780
Whoo!
347
00:19:34,780 --> 00:19:38,380
Little Mercury is one
of the last players left,
348
00:19:38,380 --> 00:19:42,250
and it could have
a faceoff with Earth.
349
00:19:42,250 --> 00:19:44,850
Mercury is the little guy
in this thing,
350
00:19:44,860 --> 00:19:47,560
and this hockey puck
is our volatiles.
351
00:19:51,430 --> 00:19:53,630
The little guy comes in
at a high speed
352
00:19:53,630 --> 00:19:56,970
and has a head-on collision
with the big guy.
353
00:19:56,970 --> 00:19:58,770
It is catastrophic.
354
00:20:02,310 --> 00:20:04,370
But suppose now,
instead of hitting him
355
00:20:04,380 --> 00:20:05,770
in a head-on collision,
356
00:20:05,780 --> 00:20:07,580
he hits him in a glancing blow.
357
00:20:14,890 --> 00:20:17,350
So he might knock off
a little bit of equipment,
358
00:20:17,360 --> 00:20:20,660
but Mercury just keeps on going
and keeps his hockey puck.
359
00:20:24,100 --> 00:20:27,860
A head-on impact would send
a shockwave across Mercury,
360
00:20:27,870 --> 00:20:30,300
melting the entire surface.
361
00:20:33,640 --> 00:20:37,370
But a glancing blow
is less ferocious.
362
00:20:37,380 --> 00:20:39,380
The more grazing
you hit something,
363
00:20:39,380 --> 00:20:44,310
the less energy you bring
to bear, the less violent it is.
364
00:20:44,320 --> 00:20:47,350
In the grazing collision
is where piece of the surface
365
00:20:47,350 --> 00:20:49,720
has grazed off
and blasted into space,
366
00:20:49,720 --> 00:20:53,160
and the other hemisphere of
the body is largely unaffected
367
00:20:53,160 --> 00:20:55,520
and allowed some
primordial material
368
00:20:55,530 --> 00:20:57,790
to remain on the surface.
369
00:20:57,800 --> 00:21:02,600
Most of Mercury's
mantle is stripped away,
370
00:21:02,600 --> 00:21:04,530
but this grazing impact
371
00:21:04,540 --> 00:21:07,970
doesn't send a shockwave
through the planet,
372
00:21:07,970 --> 00:21:13,110
and so the volatiles remain
along with enough of the mantle
373
00:21:13,110 --> 00:21:17,610
to reshape this world
with a thin outer layer of rock.
374
00:21:21,290 --> 00:21:24,620
Mercury was transformed
into the smallest planet
375
00:21:24,620 --> 00:21:27,560
in the solar system,
376
00:21:27,560 --> 00:21:32,230
and its lost mantle was stolen
by an unexpected thief.
377
00:21:33,930 --> 00:21:36,430
That mantle accretes onto
the biggest object around,
378
00:21:36,430 --> 00:21:40,440
but the biggest object
around isn't Mercury.
379
00:21:40,440 --> 00:21:43,610
When Mercury's mantle got
knocked off in this collision,
380
00:21:43,610 --> 00:21:44,810
it had to go somewhere.
381
00:21:44,810 --> 00:21:47,140
So if you're looking for
Mercury's missing mantle,
382
00:21:47,140 --> 00:21:49,380
look no further than right
under your feet.
383
00:21:50,880 --> 00:21:56,790
To this day, part of
Mercury could be part of Earth,
384
00:21:56,790 --> 00:21:59,560
stolen in a hit-and-run
collision.
385
00:22:01,290 --> 00:22:04,460
Mercury was able to survive the
formation of the solar system,
386
00:22:04,460 --> 00:22:05,760
but it paid a cost.
387
00:22:05,760 --> 00:22:09,330
It was battered.
388
00:22:09,330 --> 00:22:13,940
Since day one,
Mercury has had a tough ride.
389
00:22:13,940 --> 00:22:18,370
It's been pounded by the Sun
and planets,
390
00:22:18,380 --> 00:22:20,810
and things have not
improved since.
391
00:22:20,810 --> 00:22:22,710
You can see by the surface
of Mercury
392
00:22:22,710 --> 00:22:25,080
that it has a lot
of battle scars.
393
00:22:25,080 --> 00:22:27,480
The solar system did not
treat it well.
394
00:22:29,290 --> 00:22:34,460
The planet has been
bombarded and fried,
395
00:22:34,460 --> 00:22:37,090
but these events
could help explain
396
00:22:37,090 --> 00:22:40,260
one of Mercury's
biggest mysteries.
397
00:22:40,260 --> 00:22:43,630
Why is the planet so dark?
398
00:23:00,610 --> 00:23:04,950
The solar system is full of
beautiful, colorful planets...
399
00:23:07,050 --> 00:23:10,990
but Mercury is different.
400
00:23:10,990 --> 00:23:15,790
Its dark gray surface
baffles scientists.
401
00:23:15,790 --> 00:23:17,160
One of the most
intriguing things
402
00:23:17,160 --> 00:23:19,860
is how dark the surface
of Mercury is.
403
00:23:19,870 --> 00:23:22,230
A big mystery in
the solar system is why?
404
00:23:22,230 --> 00:23:24,530
Why is Mercury like that?
405
00:23:24,540 --> 00:23:28,040
The rocky inner planets
all formed in the same region
406
00:23:28,040 --> 00:23:32,540
of the solar system
from similar materials,
407
00:23:32,540 --> 00:23:37,050
and yet Mercury is darker
than all of them.
408
00:23:37,050 --> 00:23:41,790
Some of the darkest surfaces
here on Earth are lava fields.
409
00:23:41,790 --> 00:23:46,260
Planetary scientist Nina Lanza
visits one in Iceland
410
00:23:46,260 --> 00:23:49,830
to find some common ground.
411
00:23:49,830 --> 00:23:52,760
The surface of a planet
records the history
412
00:23:52,760 --> 00:23:55,270
of all the processes
that have acted upon it.
413
00:23:55,270 --> 00:23:57,200
So when we look at
the surface of Mercury,
414
00:23:57,200 --> 00:23:59,640
we can piece
together that story.
415
00:23:59,640 --> 00:24:04,240
Right now, we're standing
on a basalt lava flow.
416
00:24:04,240 --> 00:24:06,610
Basalt is a type
of volcanic rock
417
00:24:06,610 --> 00:24:09,010
that's the building
block of all planets,
418
00:24:09,010 --> 00:24:12,120
so we know just by seeing
this basalt here,
419
00:24:12,120 --> 00:24:14,480
there was volcanic activity.
420
00:24:17,320 --> 00:24:21,360
On Earth, most basaltic rock
is covered by oceans.
421
00:24:21,360 --> 00:24:25,400
On Mercury,
the basalt is exposed.
422
00:24:25,400 --> 00:24:27,860
Old liquid lava flows
are visible
423
00:24:27,870 --> 00:24:32,200
as smooth channels
of solid rock.
424
00:24:32,200 --> 00:24:35,610
For a billion years
after Mercury's formation,
425
00:24:35,610 --> 00:24:39,080
lava explodes
from volcanic vents
426
00:24:39,080 --> 00:24:41,340
and leaks out from fissures.
427
00:24:43,620 --> 00:24:47,280
Could the volcanism explain
the dark world we see today?
428
00:24:49,220 --> 00:24:51,960
Basalt is a pretty
dark rock already,
429
00:24:51,960 --> 00:24:53,620
but what's so interesting
about Mercury
430
00:24:53,630 --> 00:24:56,890
is that it's actually
darker than basalt.
431
00:24:56,900 --> 00:25:00,430
So from the recent
messenger mission to Mercury,
432
00:25:00,430 --> 00:25:04,270
we had some ideas about what may
be making the surface so dark,
433
00:25:04,270 --> 00:25:05,400
and it's really strange.
434
00:25:05,400 --> 00:25:08,740
It's actually carbon
in the form of graphite,
435
00:25:08,740 --> 00:25:11,540
the mineral graphite, which
is what you find in a pencil.
436
00:25:11,540 --> 00:25:16,210
So that material is all over
the surface of Mercury,
437
00:25:16,210 --> 00:25:19,120
and it's incorporated
into the rocks.
438
00:25:19,120 --> 00:25:22,890
Carbon doesn't come
from basaltic rock,
439
00:25:22,890 --> 00:25:24,890
but there is something else
440
00:25:24,890 --> 00:25:29,260
that could have brought
carbon to Mercury...
441
00:25:29,260 --> 00:25:31,360
Comets.
442
00:25:31,360 --> 00:25:35,300
These dirty ice balls
contain carbon,
443
00:25:35,300 --> 00:25:39,740
and they've bombarded the planet
for billions of years.
444
00:25:39,740 --> 00:25:43,970
The evidence of these attacks
is etched into the surface.
445
00:25:45,440 --> 00:25:48,710
It's hard to look at Mercury
and not wince on occasion.
446
00:25:48,710 --> 00:25:51,410
It is really covered
with craters.
447
00:25:51,420 --> 00:25:53,880
It has been battered
and bruised.
448
00:25:53,890 --> 00:25:56,190
It really has just
been terribly,
449
00:25:56,190 --> 00:25:59,720
terribly mistreated
over its lifetime.
450
00:25:59,730 --> 00:26:04,630
Mercury has been hit
often and hard.
451
00:26:04,630 --> 00:26:06,360
Mercury is moving more rapidly
452
00:26:06,370 --> 00:26:07,930
around the Sun
than the Earth is,
453
00:26:07,930 --> 00:26:10,730
so a head-on impact
is going to be faster
454
00:26:10,740 --> 00:26:13,300
than a head-on impact
of a comet in the Earth.
455
00:26:13,310 --> 00:26:16,440
So pound for pound,
a comet impact on Mercury
456
00:26:16,440 --> 00:26:17,870
is much more energetic,
457
00:26:17,880 --> 00:26:20,940
will do much more damage
than an impact on Earth.
458
00:26:23,620 --> 00:26:26,050
If you've ever been to, like,
meteor crater in Arizona
459
00:26:26,050 --> 00:26:28,720
in the United States,
it's around a mile across.
460
00:26:28,720 --> 00:26:30,590
It's this huge crater.
461
00:26:30,590 --> 00:26:34,590
If you were to stick that crater
on Mercury, it would disappear.
462
00:26:34,590 --> 00:26:37,330
Mercury has so many craters
that are so much bigger
463
00:26:37,330 --> 00:26:39,630
than a mile across.
464
00:26:39,630 --> 00:26:43,800
Mercury's biggest
impact site is Caloris basin.
465
00:26:43,800 --> 00:26:46,940
Over 1,000 times larger
than meteor crater,
466
00:26:46,940 --> 00:26:52,680
it's so big there are now other,
newer craters inside it...
467
00:26:52,680 --> 00:26:56,180
And Caloris basin
is coated in carbon.
468
00:26:57,920 --> 00:26:59,680
Comets have a lot
of carbon in them,
469
00:26:59,680 --> 00:27:02,050
and we know that
comets hit planets.
470
00:27:02,050 --> 00:27:04,020
So it's kind of obvious to say,
471
00:27:04,020 --> 00:27:05,090
"where did the carbon
come from?"
472
00:27:05,090 --> 00:27:08,190
Well, comets, but maybe not.
473
00:27:10,300 --> 00:27:15,630
In 2016, the messenger team
reveals an exciting new theory.
474
00:27:15,630 --> 00:27:18,000
Are the largest impact craters
475
00:27:18,000 --> 00:27:21,970
actually exposing
something deeper?
476
00:27:21,970 --> 00:27:25,580
Impact craters are windows
into the lower parts
477
00:27:25,580 --> 00:27:27,510
of the crust of a planet,
478
00:27:27,510 --> 00:27:28,850
and the larger
the impact crater,
479
00:27:28,850 --> 00:27:30,950
the deeper the impact event
480
00:27:30,950 --> 00:27:33,950
has excavated
material from depth
481
00:27:33,950 --> 00:27:37,720
and brought it to where
we can see it at the surface.
482
00:27:37,720 --> 00:27:41,620
The craters reveal a twist.
483
00:27:41,630 --> 00:27:44,230
The carbon that makes
Mercury so dark
484
00:27:44,230 --> 00:27:47,160
had been there all along
485
00:27:47,170 --> 00:27:50,970
as part of the material
that first formed the planet.
486
00:27:55,840 --> 00:27:58,710
When young Mercury is hit,
parts of the surface
487
00:27:58,710 --> 00:28:03,410
are transformed
into an ocean of molten rock.
488
00:28:03,420 --> 00:28:07,220
As this magma ocean cools,
it solidifies,
489
00:28:07,220 --> 00:28:11,320
forming a crust,
490
00:28:11,320 --> 00:28:14,890
and sitting on top
of this crust, graphite,
491
00:28:14,890 --> 00:28:19,060
the crystallized form of carbon.
492
00:28:19,060 --> 00:28:20,730
Carbon containing
minerals like graphite
493
00:28:20,730 --> 00:28:22,330
would end up near
the surface of Mercury
494
00:28:22,330 --> 00:28:23,930
at the top of that magma ocean
495
00:28:23,940 --> 00:28:27,140
because those minerals
are a lot less dense
496
00:28:27,140 --> 00:28:29,370
than the conventional
rocky minerals
497
00:28:29,370 --> 00:28:30,440
that contain a lot of, you know,
498
00:28:30,440 --> 00:28:32,480
iron and nickel.
Those are more dense.
499
00:28:32,480 --> 00:28:34,710
They tend to sink to
the center of the planet.
500
00:28:34,710 --> 00:28:36,780
Those lighter elements
like graphite
501
00:28:36,780 --> 00:28:38,480
would tend to float to the top.
502
00:28:41,050 --> 00:28:43,290
But volcanism covers the planet
503
00:28:43,290 --> 00:28:46,560
in new basalt lava flows
504
00:28:46,560 --> 00:28:49,260
coming from deep
below the surface
505
00:28:49,260 --> 00:28:52,760
where the carbon didn't sink,
506
00:28:52,760 --> 00:28:57,570
and this lava buries
Mercury's ancient crust.
507
00:28:57,570 --> 00:28:59,540
Over time, that carbon
is covered up
508
00:28:59,540 --> 00:29:01,440
by subsequent lava flows,
509
00:29:01,440 --> 00:29:02,870
but there was
this layer of carbon
510
00:29:02,870 --> 00:29:05,340
waiting underneath
the surface of Mercury,
511
00:29:05,340 --> 00:29:09,310
and as objects hit Mercury and
gouged out holes in the surface,
512
00:29:09,310 --> 00:29:14,050
it exposed this hidden
darker layer underneath.
513
00:29:14,050 --> 00:29:17,490
Covered by a billion
years of lava flows
514
00:29:17,490 --> 00:29:21,160
and revealed
by giant impact events,
515
00:29:21,160 --> 00:29:22,790
one this is for sure...
516
00:29:22,790 --> 00:29:28,200
Mercury's surface has been
a truly hellish landscape.
517
00:29:28,200 --> 00:29:30,070
Imagine that we're on
the surface of Mercury
518
00:29:30,070 --> 00:29:32,100
during that first billion years
519
00:29:32,100 --> 00:29:36,270
when volcanism was very active.
520
00:29:36,270 --> 00:29:40,040
Raining down from the sky,
all these comets and meteorites
521
00:29:40,050 --> 00:29:43,450
just pelting
the surface mercilessly,
522
00:29:43,450 --> 00:29:45,750
and then, beneath your feet,
523
00:29:45,750 --> 00:29:49,950
there'll be all this
molten rock bubbling up.
524
00:29:49,960 --> 00:29:52,820
Really an awful place to be
525
00:29:52,820 --> 00:29:54,860
in that first billion years
on Mercury.
526
00:29:57,130 --> 00:29:59,000
Over billions of years,
527
00:29:59,000 --> 00:30:04,830
comets and volcanism reshaped
the surface of Mercury,
528
00:30:04,840 --> 00:30:08,870
and this planet is not done yet.
529
00:30:08,870 --> 00:30:14,740
Scientists find giant cliffs
stretching hundreds of miles.
530
00:30:14,750 --> 00:30:18,650
It seems Mercury is alive.
531
00:30:35,930 --> 00:30:41,100
Mercury, a small,
dark world covered in craters
532
00:30:41,100 --> 00:30:44,270
and ancient lava flows,
533
00:30:44,270 --> 00:30:48,410
but scientists find
something else on the surface.
534
00:30:48,410 --> 00:30:54,650
Towering cliffs around 2 miles
high known as fault scarps.
535
00:30:54,650 --> 00:30:56,610
If you were walking
along one of these scarps
536
00:30:56,620 --> 00:30:58,080
on the surface of Mercury,
537
00:30:58,080 --> 00:30:59,880
there would be
this giant cliff face
538
00:30:59,890 --> 00:31:03,250
that would go on for miles
and miles well over the horizon,
539
00:31:03,260 --> 00:31:07,190
so you would be walking next
to an almost endless cliff.
540
00:31:07,190 --> 00:31:12,300
The largest fault
scarp is enterprise Rupes.
541
00:31:12,300 --> 00:31:16,800
At over 600 miles long, it would
span the width of Texas.
542
00:31:18,640 --> 00:31:21,540
We see fault scarps on Earth,
543
00:31:21,540 --> 00:31:24,140
evidence of tectonic activity.
544
00:31:26,680 --> 00:31:30,080
Planetary scientist
Jani Radebaugh visits a scarp
545
00:31:30,080 --> 00:31:32,350
in death valley to demonstrate.
546
00:31:34,520 --> 00:31:37,190
This long, straight
line of shadows behind me
547
00:31:37,190 --> 00:31:40,290
formed because death valley
is still spreading apart
548
00:31:40,290 --> 00:31:42,030
and the material on the right
549
00:31:42,030 --> 00:31:44,230
has dropped down from
the material on the left
550
00:31:44,230 --> 00:31:47,300
and left a really
sharp fault scarp.
551
00:31:47,300 --> 00:31:49,030
The fault scarp
you see behind me,
552
00:31:49,040 --> 00:31:53,270
and the ones we see on Mercury,
are formed by tectonic forces,
553
00:31:53,270 --> 00:31:55,210
and this just means
that there are forces
554
00:31:55,210 --> 00:31:56,840
inside of the planets,
555
00:31:56,840 --> 00:32:00,810
and those forces cause
breaks in the crust.
556
00:32:03,750 --> 00:32:06,950
On Earth, transfer
of heat from the mantle
557
00:32:06,950 --> 00:32:11,490
drives the movement
of continental plates.
558
00:32:11,490 --> 00:32:14,730
These plates move around
the surface of the planet,
559
00:32:14,730 --> 00:32:16,430
interacting with each other...
560
00:32:19,730 --> 00:32:23,830
Building mountains, rift
valleys, even continents.
561
00:32:26,710 --> 00:32:28,810
Do the fault scarps on Mercury
562
00:32:28,810 --> 00:32:32,540
mean it also has
plate tectonics?
563
00:32:32,550 --> 00:32:34,580
When you think about
the Earth's plate tectonics,
564
00:32:34,580 --> 00:32:36,650
there are multiple
plates of rock
565
00:32:36,650 --> 00:32:40,620
that are moving around
on a layer of liquid rock below.
566
00:32:40,620 --> 00:32:43,620
Mercury, however, has basically
just one big plate.
567
00:32:43,620 --> 00:32:46,660
There's a solid surface
that covers the entire planet.
568
00:32:49,130 --> 00:32:54,130
Mercury has a
different kind of tectonics.
569
00:32:54,130 --> 00:32:58,040
Over billions of years,
its liquid core cools,
570
00:33:00,070 --> 00:33:06,180
and as the interior cools, the
planet shrinks around 9 miles.
571
00:33:06,180 --> 00:33:08,550
When something cools,
it contracts.
572
00:33:08,550 --> 00:33:11,720
It actually becomes smaller.
573
00:33:11,720 --> 00:33:16,290
Because of this contraction,
the rock and the crust wrinkles,
574
00:33:16,290 --> 00:33:18,960
creating massive scarps.
575
00:33:18,960 --> 00:33:21,830
You can imagine, if you take
a balloon and cover it in mud
576
00:33:21,830 --> 00:33:23,330
and let the mud dry,
577
00:33:23,330 --> 00:33:25,300
and then you let a little bit
of air out of the balloon,
578
00:33:25,300 --> 00:33:26,530
what's going to happen?
579
00:33:26,530 --> 00:33:28,200
Well, that mud is going to
try to contract as well,
580
00:33:28,200 --> 00:33:31,940
but it can't, and so it'll crack
and snap like that,
581
00:33:31,940 --> 00:33:34,970
and you'll get these
thrust faults, these scarps.
582
00:33:36,880 --> 00:33:40,140
But for Mercury,
the story doesn't end there.
583
00:33:42,350 --> 00:33:45,180
We understand that the large
fault scarps on Mercury formed
584
00:33:45,180 --> 00:33:47,650
a long time ago
when the planet was cooling
585
00:33:47,650 --> 00:33:50,390
and the crust was
shrinking and buckling,
586
00:33:50,390 --> 00:33:53,460
but more recently, messenger
has come very close to Mercury
587
00:33:53,460 --> 00:33:57,130
and has found really
small fault scarps.
588
00:33:57,130 --> 00:33:59,600
Unlike the giant
mile-high scarps,
589
00:33:59,600 --> 00:34:04,130
these small ones are less
than 200 feet in length.
590
00:34:04,140 --> 00:34:05,770
What does this mean?
591
00:34:05,770 --> 00:34:09,210
These are small scarps,
and the thing is,
592
00:34:09,210 --> 00:34:10,940
if those were really old,
593
00:34:10,940 --> 00:34:12,680
impacts would have erased them,
594
00:34:12,680 --> 00:34:15,650
and so these should be
long gone off the surface.
595
00:34:15,650 --> 00:34:17,620
So that means that
they're recent.
596
00:34:17,620 --> 00:34:18,620
They're new.
597
00:34:18,620 --> 00:34:20,250
Right now, Mercury
has the record
598
00:34:20,250 --> 00:34:23,250
of being the smallest official
planet in the solar system,
599
00:34:23,260 --> 00:34:26,620
but is it possible the smallest
planet is still shrinking?
600
00:34:28,630 --> 00:34:32,330
Throughout its life,
Mercury has been bombarded.
601
00:34:34,400 --> 00:34:39,800
Impacts have cratered
the large, old fault scarps.
602
00:34:39,810 --> 00:34:45,010
The small scarps should be
covered in impact scars as well,
603
00:34:45,010 --> 00:34:50,250
but they're pristine, which
means that they're young,
604
00:34:50,250 --> 00:34:55,420
and that means Mercury
is still shrinking.
605
00:34:55,420 --> 00:34:58,590
Mercury is actually
still tectonically active.
606
00:34:58,590 --> 00:34:59,990
So the Earth is no longer
607
00:34:59,990 --> 00:35:02,660
the only tectonically active
planet in the solar system.
608
00:35:02,660 --> 00:35:05,400
We've seen that Mercury
has a surprising history.
609
00:35:05,400 --> 00:35:08,600
The thing is, the planet
itself is still cooling,
610
00:35:08,600 --> 00:35:12,000
still contracting, even after
all of these billions
611
00:35:12,000 --> 00:35:14,910
of years after it formed.
That's amazing.
612
00:35:14,910 --> 00:35:17,070
At first, it may seem
that you could write this off
613
00:35:17,080 --> 00:35:20,240
as a dull, little, dead rock
close to the Sun,
614
00:35:20,250 --> 00:35:23,250
but Mercury has a story to tell.
615
00:35:23,250 --> 00:35:26,580
A story that continues
to this day
616
00:35:26,590 --> 00:35:29,650
despite everything the
planet has gone through.
617
00:35:32,020 --> 00:35:33,990
Mercury has had it pretty
rough. It's had a tough time
618
00:35:33,990 --> 00:35:36,590
over the history
of the solar system.
619
00:35:36,600 --> 00:35:38,760
It has been tossed
around by planets.
620
00:35:38,760 --> 00:35:42,100
It has been impacted by
gigantic asteroids and comets.
621
00:35:42,100 --> 00:35:43,270
It is shrinking.
622
00:35:43,270 --> 00:35:45,300
It's bombarded
by solar radiation.
623
00:35:45,300 --> 00:35:47,400
That would tick anybody off,
624
00:35:47,410 --> 00:35:49,970
and it's entirely possible
that in the future,
625
00:35:49,980 --> 00:35:52,310
Mercury will get its revenge.
626
00:35:54,480 --> 00:35:58,080
Mercury could have
a final trick up its sleeve,
627
00:35:58,080 --> 00:36:01,690
one that threatens
our very existence.
628
00:36:21,870 --> 00:36:25,270
Messenger completes
its final orbit of Mercury...
629
00:36:27,610 --> 00:36:31,640
and crashes into
the planet's surface,
630
00:36:31,650 --> 00:36:34,010
a fitting conclusion for a world
631
00:36:34,010 --> 00:36:36,510
with a history of impacts.
632
00:36:36,520 --> 00:36:38,980
At the end of
the messenger mission,
633
00:36:38,990 --> 00:36:43,250
our view of Mercury had
been substantially changed.
634
00:36:43,260 --> 00:36:45,920
We suddenly had a picture
of a complete world,
635
00:36:45,930 --> 00:36:48,860
a place that had hellishly
high temperatures
636
00:36:48,860 --> 00:36:51,130
and yet ices of water,
637
00:36:51,130 --> 00:36:53,230
an evolution that didn't match
638
00:36:53,230 --> 00:36:57,270
that of any of its
sibling planets.
639
00:36:57,270 --> 00:37:02,410
Could Mercury's future be just
as unpredictable as its past?
640
00:37:02,410 --> 00:37:06,440
Right now, the future
of Mercury looks bright...
641
00:37:06,450 --> 00:37:10,650
Very, very bright.
642
00:37:10,650 --> 00:37:14,350
It's all thanks to
Mercury's massive neighbor.
643
00:37:14,350 --> 00:37:16,920
The Sun is a giant ball
of hydrogen and helium,
644
00:37:16,920 --> 00:37:20,020
and in the core, there's
a nuclear fusion reaction,
645
00:37:20,030 --> 00:37:23,630
but over time, the fuel that
the Sun runs on, hydrogen,
646
00:37:23,630 --> 00:37:25,100
will begin to die out.
647
00:37:25,100 --> 00:37:27,470
It will actually burn
through all of its fuel.
648
00:37:27,470 --> 00:37:31,040
When that happens,
in the final phases of its life,
649
00:37:31,040 --> 00:37:34,070
the Sun will bloat up
to become a red giant star,
650
00:37:34,070 --> 00:37:36,710
hundreds of times the size
that it currently is.
651
00:37:38,310 --> 00:37:43,210
As the Sun expands,
it will engulf Mercury.
652
00:37:43,220 --> 00:37:46,650
Being on the surface of Mercury
is bad enough right now.
653
00:37:46,650 --> 00:37:49,150
Now put it inside of a star.
654
00:37:52,960 --> 00:37:54,960
All of that heat
bombarding the planet
655
00:37:54,960 --> 00:37:57,500
will literally boil it away.
656
00:37:59,570 --> 00:38:02,670
But is there a chance
that Mercury could escape
657
00:38:02,670 --> 00:38:05,700
this roasting?
658
00:38:05,710 --> 00:38:07,610
There's not just
the evolution of the Sun
659
00:38:07,610 --> 00:38:09,170
that we have to take
into account.
660
00:38:09,180 --> 00:38:12,310
The planets themselves
and their orbits are evolving.
661
00:38:12,310 --> 00:38:14,880
They look stable,
but over long time periods,
662
00:38:14,880 --> 00:38:16,480
they can change drastically.
663
00:38:20,550 --> 00:38:23,890
The Sun exerts the
strongest gravitational pull
664
00:38:23,890 --> 00:38:27,330
of any object
in the solar system.
665
00:38:27,330 --> 00:38:31,160
It's why the planets orbit it,
666
00:38:31,160 --> 00:38:35,300
but planets can also
pull on each other.
667
00:38:35,300 --> 00:38:38,770
Mercury is tiny,
making it most vulnerable
668
00:38:38,770 --> 00:38:42,510
to these gravitational tugs.
669
00:38:42,510 --> 00:38:47,980
After the Sun, the next
biggest object is Jupiter.
670
00:38:47,980 --> 00:38:50,450
We can take computer
models and simulate
671
00:38:50,450 --> 00:38:52,750
Mercury's orbit
as it's affected by Jupiter
672
00:38:52,750 --> 00:38:54,720
to see what happens to Mercury,
673
00:38:54,720 --> 00:38:56,090
and depending
on initial conditions,
674
00:38:56,090 --> 00:38:57,860
a lot of different
things can happen.
675
00:38:57,860 --> 00:39:01,190
But in some percentage
of the models, what can happen
676
00:39:01,190 --> 00:39:04,600
is Mercury's orbit
changes so much
677
00:39:04,600 --> 00:39:06,460
that it actually swings out
678
00:39:06,470 --> 00:39:09,930
and can reach the orbit
of the Earth.
679
00:39:14,210 --> 00:39:18,680
Jupiter is often seen as the
bully of the solar system.
680
00:39:18,680 --> 00:39:21,950
Here, it's Mercury's bodyguard.
681
00:39:21,950 --> 00:39:24,380
Over time, its
gravitational influence
682
00:39:24,380 --> 00:39:29,520
stretches Mercury's orbit
out farther and farther,
683
00:39:29,520 --> 00:39:32,360
and the little world escapes
the Sun's clutches
684
00:39:32,360 --> 00:39:36,090
long before it expands
to a red giant.
685
00:39:38,160 --> 00:39:42,400
But this tale
has one final twist.
686
00:39:42,400 --> 00:39:46,700
It's easy to dismiss Mercury
in the pantheon of planets,
687
00:39:46,710 --> 00:39:50,210
but ignore it at your peril
because there may come a day
688
00:39:50,210 --> 00:39:55,680
when Mercury makes its presence
very well known indeed.
689
00:39:55,680 --> 00:39:58,680
I'd like to think that Mercury
does not bear the solar system
690
00:39:58,690 --> 00:40:01,120
any ill will for
all the hard time
691
00:40:01,120 --> 00:40:04,120
it's been given over
the last 4.5 billion years,
692
00:40:04,120 --> 00:40:08,460
but, you know, that's a long
time to build up a grudge.
693
00:40:08,460 --> 00:40:10,600
Mercury has had
such a difficult past.
694
00:40:10,600 --> 00:40:14,100
It's been beat on by the Sun,
collided with other planets.
695
00:40:14,100 --> 00:40:16,930
Now Mercury could come in and
start wreaking havoc with us,
696
00:40:16,940 --> 00:40:19,770
so maybe we can think of this
as sort of Mercury's revenge.
697
00:40:21,810 --> 00:40:23,510
Billions of years ago,
698
00:40:23,510 --> 00:40:25,480
Earth could well have collided
699
00:40:25,480 --> 00:40:30,250
with the young Mercury,
changing Mercury forever.
700
00:40:34,720 --> 00:40:39,160
And now, it comes face-to-face
with Earth once again...
701
00:40:43,000 --> 00:40:48,500
Smashing into our planet
in one, final impact,
702
00:40:48,500 --> 00:40:52,240
wiping out any trace
of the world we know and love.
703
00:40:54,040 --> 00:40:56,070
It would melt our entire crust.
704
00:40:56,080 --> 00:40:59,480
It would wipe out all life
on our planet.
705
00:41:03,920 --> 00:41:07,390
So how worried should
we be about this threat?
706
00:41:07,390 --> 00:41:10,020
The odds of this happening
aren't that high,
707
00:41:10,020 --> 00:41:11,960
and if it happens,
it's going to happen
708
00:41:11,960 --> 00:41:13,590
billions of years in the future.
709
00:41:13,590 --> 00:41:17,300
So I'm not terribly worried
about it on a personal scale,
710
00:41:17,300 --> 00:41:21,500
but as an astronomer and as
a scientist, that's fascinating.
711
00:41:25,870 --> 00:41:28,370
Mercury may continue
to surprise us,
712
00:41:28,370 --> 00:41:31,080
even to its dying day,
713
00:41:31,080 --> 00:41:38,020
a world born in fire that
might also go down in flames.
714
00:41:38,020 --> 00:41:40,020
But the fact that
it made it this far
715
00:41:40,020 --> 00:41:43,290
is nothing short of remarkable.
716
00:41:43,290 --> 00:41:45,890
Living in the toughest
neighborhood imaginable,
717
00:41:45,890 --> 00:41:50,160
Mercury has made it through
the history of the solar system,
718
00:41:50,160 --> 00:41:53,660
beaten, but not broken.
719
00:41:53,670 --> 00:41:56,800
Mercury is one of the solar
system's great survivors.
720
00:41:56,800 --> 00:41:58,770
Despite all of the things
that happened to it,
721
00:41:58,770 --> 00:42:01,270
it's still hanging in there.
722
00:42:01,270 --> 00:42:03,370
It's been subject to
the harshest environment
723
00:42:03,380 --> 00:42:06,910
in the solar system,
and it's still around.
724
00:42:06,910 --> 00:42:10,780
Mercury, you know, has been
attacked from all sides, right?
725
00:42:10,780 --> 00:42:12,680
It's been roasted by the Sun.
726
00:42:12,690 --> 00:42:16,890
It's been pummeled by impactors,
and yet it's still there,
727
00:42:16,890 --> 00:42:18,590
still being a great planet,
728
00:42:18,590 --> 00:42:22,230
this plucky, little survivor
who's still orbiting
729
00:42:22,230 --> 00:42:24,360
despite everything
it's gone through.
59413
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