order to slow down enough we uh just had spacecraft
spacecraft
jettison so messenger controls its speed
by stepping from one planet to the next
using their
itself even so messenger still
approaches Mercury moving so fast that
it is forced to fly past the planet
three times
pass until after nearly 7 years of flawless
flawless
orbit at last able to begin its mission
surface that first image ever acquired
from orbit around Mercury was amazing
when it finally came in it looked
perfect it looked exactly like we
expected it to
be for me that was the real moment when
I realized that we had successfully made
it into orbit and everything was
working this pioneering Voyage has led
to a completely new idea of how Mercury
Mercury is the most cratered planet in
system with many puzzling features that
past mercury has a very unusual orbit if
you were on the surf surface of the
planet you would actually have to go
around the Sun twice to get one full
Mercury solar
day also highly unusual is the planet's
disproportionately large core Mercury is
basically a big ball of metal surrounded
like a tiny bit of rock how do you end
up with a planet that has so much metal
inside and then almost none on its
surface that was a huge mystery and the
major question is is why why is it like
aren't a clue to understanding these strange
strange
features was found in Mercury's
chemistry so very soon after we got into
orbit we started to get chemical data
back from the surface and we immediately
surprises the tiny probe detects
volatile chemical elements in
concentrations that no one had thought
Sun these are elements that go into
rocks but that evaporate at relatively low
temperatures and immediately told us
that some of the older ideas of how
Mercury formed could not be
correct what messenger discovered about
Mercury could suggest a new twist in the
system just a few million years after its
its
formation the young Mercury is seething
slowly a crust
elements if it had been close to the
Sun these elements would have evaporated
before the rock
hardened so what could explain why
they're so abundant on Mercury
today the orbits of the planets and
their current locations have changed
over the history of the solar system so
where things are today doesn't mean
that's necessarily where they formed
they could have and probably did move
from different locations to where they
are now one possible thing is that
mercury didn't form where it is today it
form much closer to the other planets
maybe even outside of Venus or Earth or
in somewhere in between there if Mercury
had formed near Earth and remained at a
Sun its Destiny could have been very different
but it wasn't to
be so what turned it into the strange
today we don't know the full story what
we have right now are theories and as we
have new observations we are trying to
change everything to fit those observations
observations [Music]
[Music]
Messengers evidence of the volatiles on
Mercury surface and the unusual size of
Theory it's possible Mercury began life
as much as 160 million kilm further from
today in the region of space where the
forming a region with scores of
position in the chaos it's possible that
something large pushes Mercury off orbit
Mercury brushes against another planetary
embryo this glancing blow removing much
now little more than a metallic planetary
sun ending up in the peculiar elliptical
today before we sent the messenger
mission to Mercury I think we had a very
simplistic idea of what it was going to
be like and Mercury turns out to be a
more complex place with a more
interesting and complex history than we
had previously imagined but of course
all things have to come to an end and
once we were out of fuel we could no
longer burn our engines to keep from
launch after 4 years of observations
out and the spacecraft adds yet another
crater to this tiny
world where any prospects for life were
scorched away when it was thrown too
the sun's outer Corona Burns at a
scorching 1 million
de releasing a barrage of charged
second the solar [Music]
wind this Onslaught would strip away our
atmosphere but for the power power ful
force that protects
field solar wind is this stream of
charged particles that come streaming
out from the Sun and at Earth which has
a powerful magnetic field when those
charged particles begin to get close to
Earth they get diverted around Earth by
interactions with that magnetic field
that protection keeps solar wind and
other ionizing radiation off of the
surface so on Earth where we have this
really great magnetic field we are nice
safe and sound inside the shell of that
protected from all that radiation the
magnetic field of Earth effectively
forms a protective bubble around the Earth's
Earth's
atmosphere and when the sun dips below the
the
Horizon there are times when Earth's
protective force field is visible [Music]
[Music]
the Aurora is a stunning display of
Earth's magnetic field in [Music]
[Music]
action it's best seen at the poles but
across earth it's protecting our
planet this vital protective shield is
the way a magnetic field is generated
inside a planet is when you have
convective Motion in a fluid that is
capable of conducting
electricity and in the earth that
electrically conducting fluid is liquid
iron and the molten portion of the
earth's core is a place where these
motions take place and it can set up a
magnetic field [Music]
[Music]
just like Earth Mars once had a molten metallic
metallic
core generating a magnetic field around the
the [Music]
poles protecting its atmosphere and seas below
last in the oldest rocks on Mars you see
evidence of a once powerful magnetic
field you get to the younger rocks rocks
that are 3 billion 2 billion 1 billion
years old no evidence of a magnetic
field whatsoever and there is no
today half a bill million years after it
out the bright auroras above its poles
away as the shield that protects the
good once it stops then what happens is
all the atmospheric components things
like hydrogen oxygen that make up water
they get stripped away because you don't
have the shield the magnetic Shield
anymore so the high energy particles
that come in from the Sun and from outer
space they begin to strip away the
water without its magnetic field to
protect it Mars's atmosphere and then
shield what happened deep beneath its
surface that stopped Mars from
Earth the answer lies at the beginning
of Mars's
4.6 billion years ago when the planets
were forming from the dust cloud
sun early differences between Mars and
Earth set the young planets on very different
paths Mars forms further from the Sun
where crucially there is less Rocky
planet Mars is different because it's
not just further out it's actually much
smaller if a planet gets to be too small
through Mars is just half the diameter of
of
quickly and so it lost the heat that
powered the Dynamo that generated its protective
shield Mars's small
millions of years
Moon perhaps 400 km
ice but this Moon is
doomed it's orbiting just too close to
resist the immense forces of Saturn's [Applause]
[Applause]
Gravity the Rings probably formed from
an object that got too close to Saturn
there's this invisible boundary around
Saturn called the RO limit and that's
the limit depending on what you're made
of where Saturn's gravity is strong
enough will actually pull you apart that
the gravity on the side closer to Saturn
is strong enough that compared to the
gravity on the other side that will L
literally rip you apart you don't have
together a leading theory suggests that
just beyond Saturn's
atmosphere an ice Moon approaches close
as Saturn's immense gravitational force
pulls it apart the moon begins to rupture
catastrophically a world ripped apart by
Saturn and thanks to the speeds this
material is traveling it's like likely
that in just a few days it spreads out
[Music]
giant Saturn's iconic
ring is now in [Music]
place but as Cassini turns its
instruments towards it it sees a single
the images we returned they were
phenomenal they were resolution factor
of maybe 20 times better than anything
we had had [Music]
before Cassini reveals how Saturn's
evolved this debris now forms a dis
wider than
Jupiter yet on average just 10 m
thick within moon-sized chunks of ice
voids turning one
many but it's as Cassini captures images
with the sun directly above the
equator that the most surprising feature
of the Rings
emerges we knew this was going to be a
time for us to investigate the third
dimension something that you don't get
to see when you just look at picture of
Saturn's rings and what we found was staggering
just right out of the gate we saw
vertical structures I just can't tell
you how surprised we were to see this
unanticipated I have just
imagined flying along in a
shuttlecraft across the ring right close
to the ring so to my perspective it
would be almost like it was an infinite
sheet of gleaming debris and I'm flying
along and flying along and flying along
and suddenly I come upon a wall of
High I mean is that cool or
what really i' I've said over and over
movie this once Tiny World of rock and
Ice that is has seen the most dramatic
Transformations is today the Solar
Jewel after more than a decade in orbit
Cassini has forever deepened our
understanding of
as the young Jupiter circles the sun it
clears a path through the gas cloud that
envelops the early solar
system but that process causes it to do something
alarming Jupiter begins to spiral inwards
plowing straight through the region of
belt when the young Jupiter moves
through the primordial asteroid belt
things get scattered around things get
gravitationally deflected and as a
consequence of all of this gravitational
interaction more than 99% of the
original mass that was there is
the asteroid belt has been disrupted
over time by the movement of the giant
planets and this has acted to throw
material from the asteroid belt out of
system these protoplanetary cores like
series were never able to graduate to
full-fledged planets because there was
just not enough material in the orbital neighborhood
neighborhood [Music]
when Jupiter passed through the
primordial asteroid belt it starved
growth and the dwarf planet was
condemned to live out its life as a cold
but siries isn't the only World in our
short Mars would suffer a similar fate
Jupiter after marauding through what
would become the asteroid belt
Jupiter enters the region of space where
forming continuing its Journey spiraling
its immense gravity scatters material in all
directions some is sent careering into the
Sun and some is thrown out into Interstellar
space it is because of the gravitational
clearing of this neighborhood by Jupiter
that Mars was unable to grow to more
than 10% of that of the Earth this is
and by clearing material out of the
inner solar
system the giant planet may also have
prevented the formation of the super
systems and if it had continued moving
formed but then just as it looks like
Jupiter will sweep everything
tracks because in the shadows of the
outer solar
forming the solar system second gas giant
everything as Jupiter moved inwards
Saturn moved inwards and caught up to
Jupiter's orbit when this happened the
two locked into a special configuration
known as a mean motion resonance this is
where the planets begin to interact
gravitationally in a very coherent
Manner and now locked as a unit the two
reversed their Mig migration course and
out
retreat leaving behind just enough
material from which the inner planets could
home Earth is in exactly the right
location to provide the environment for
life to develop so if Jupiter had moved
around even more who knows maybe life
never would have developed in the solar
It And as its voyage across the solar
system draws to a
close Jupiter helps to provide our
living world with its most precious [Music]
ingredient today 2/3 of our planet
surface is covered by
ocean more than one 1.3 billion cubic km of
of [Music]
[Music]
life one of the big questions about the
evolution of our solar system is how did
we get water here on this planet so we
think that the inner planets didn't
naturally form with a lot of water water
is primarily in the outer solar system
system but if you end up having Jupiter
and Saturn moving
outwards then that is able to suddenly
system locked in a gravitational dance with
with
Saturn Jupiter moves back through the asteroid
asteroid
belt and as it does so water Rich
material is flung inward
where it is incorporated into the
growing terrestrial
worlds so the movement of the giant
planets have actually played an
important role in the delivery of water
to the inner solar
system in a sense it is Jupiter's
outwards motion through the asteroid
belt that we have to thank for the
delivery of water to the surface of the
Earth the Earth would be quite a
different planet if not for Jupiter's
around 100 million years
ago an asteroid 10 kilm across is
belt dislodged from its orbit by
Jupiter it is now on a collision course
with Earth [Music]
when it
strikes the impact generates a fireball so
hot anything within a 1,000 km radius
the impact throws some 300 billion tons
atmosphere and during the nuclear winter that
that
follows 75% of species plant and animal
are wiped from the face of the
Earth in including the largest creatures
surface by driving the dinosaurs to Extinction Jupiter cleared the way for
Extinction Jupiter cleared the way for us to inherit the
earth and although it still occasionally flings asteroids our
for objects heading toward Earth from the far reaches of the solar
the far reaches of the solar system the giant planet's immense
system the giant planet's immense gravity acts as a
shield around 100 years ago a lump of rock and ice for km
rock and ice for km across is hurdling towards the inner
across is hurdling towards the inner solar
system but Jupiter stands in its way 5 4 3 2 1 we have ignition and liftoff of
3 2 1 we have ignition and liftoff of Atlanta and the Galileo spacecraft Bound
Atlanta and the Galileo spacecraft Bound for
Jupiter 70 years later a mission launches that will witness just how
launches that will witness just how effective a shield Jupiter can
be on board the space shuttle [Music]
[Music] Atlantis the Galileo
Orbiter 3 years after Galileo launches Comet Shoemaker le9 has been captured by
Comet Shoemaker le9 has been captured by Jupiter's
gravity and now locked in the giant planet's deadly
planet's deadly Embrace tidal forces begin to tear the
Embrace tidal forces begin to tear the comet
apart its journey into the inner solar system cut
system cut short what happens next presents the
short what happens next presents the Galileo scientists with a unique
opportunity and so everyone was observing it and they realized two
observing it and they realized two things one is that it had just passed
things one is that it had just passed very close to Jupiter and probably had
very close to Jupiter and probably had gotten pulled apart by Jupiter's tides
gotten pulled apart by Jupiter's tides and the other was that it was going to
and the other was that it was going to crash into Jupiter two years later the
crash into Jupiter two years later the discovery that a comet was about to hit
discovery that a comet was about to hit Jupiter was a huge surprise and very
Jupiter was a huge surprise and very exciting
after crossing the inner solar system Galileo is approaching the
Galileo is approaching the spot where it will witness the comet's
spot where it will witness the comet's final
final moments we knew Galo would be able to
moments we knew Galo would be able to see the flashes
see the flashes directly we knew that the impacts were
directly we knew that the impacts were going to occur on the night side and
going to occur on the night side and that Galo was going to be able to see
that Galo was going to be able to see him
on July 16th Galileo sees the first fragments of the
fragments of the Comet enter Jupiter's southern
hemisphere at 60 kmet per second the fragments really heated The Atmosphere
fragments really heated The Atmosphere Red Hot almost to the temperatures of
Red Hot almost to the temperatures of the sun and the pieces hit the planet
the sun and the pieces hit the planet one after the
one after the other pieces of comet Shoemaker Ley 9
other pieces of comet Shoemaker Ley 9 strike Jupiter over the course of 6
strike Jupiter over the course of 6 days they look like big flashes on
days they look like big flashes on Jupiter the pictures of the impact were
fantastic these tiny Points of Light captured from 240 million km
captured from 240 million km away are the only only time a comet
away are the only only time a comet strike has ever been
witnessed the most destructive impact releases energy equivalent to 6
impact releases energy equivalent to 6 million megatons of
million megatons of TNT leaving behind a giant Dark Cloud
TNT leaving behind a giant Dark Cloud 12,000 km across
by capturing objects in its orbit and incinerating them on impact Jupiter
incinerating them on impact Jupiter protects us from bodies that might
protects us from bodies that might otherwise collide with Earth
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