From Superstition to Science
WE'VE TRIED TO FIGURE OUT THE NATURE OF METEORITES FROM CHANCE ENCOUNTERS.
WE'VE MARVELED FROM AFAR AS COMETS EXTENDED THEIR GASSY TAILS...
BUT NOW WE'VE ORBITED AN ASTEROID CLOSE-UP...
AND SOON WE'LL BRING BACK COMET DUST TO EARTH.
chapter head: ASTEROIDS AND THE BIRTH OF THE SOLAR SYSTEM
IN THIS VIDEO, ASTEROIDS AND WHAT THEY TELL US ABOUT THE BIRTH OF OUR SOLAR SYSTEM...
chapter head: COMETS IN CLOSE UP
COMETS, AND THEIR TRANSFORMATION FROM OBJECTS OF FEAR TO OBJECTS WE CAN REACH OUT AND TOUCH!
chapter head COSMIC COLLISIONS
AND COSMIC COLLISIONS AS THE MAKERS AND DESTROYERS OF WORLDS...
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TITLES
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titles pop on one at a time:
ASTEROIDS
COMETS
METEORS
METEORITES
narrator:
ASTEROIDS... COMETS... METEORS... METEORITES... LET'S DEFINE OUR TERMS!
name title:
ANDY CHENG
Project Scientist, NEAR
Johns Hokins Univ / APL, NASA
CHENG:
Asteroids are primitive objects, many of them left behind from the formation of the solar system.
The planets condensed out of a ball of gas and dust... some of them never survived the process.
They grew up to almost the size of planets, and they were crashed into at high speed by another forming object and broken into pieces again.
OTHERS FORMED INTO BIGGER OBJECTS, AND GREW LARGE ENOUGH FOR SOME PLANETARY PROCESSES TO BEGIN, WITH INTERNAL HEATING SEPARATING THEIR MATERIALS INTO DISTINCT AND DIFFERENTIATED LAYERS.
SOME OF THESE THEN SMASHED INTO OTHERS AND BROKE APART ONCE MORE INTO SMALLER CHUNKS.
title: COMET
COMETS ALSO CONTAIN DUST, BUT THEY'RE CHARACTERIZED BY LARGER CONCENTRATIONS OF WATER ICE AND FROZEN GASES.
name title:
CLAUDIA ALEXANDER
US Project Scientist, ROSETTA Comet Mission
JPL, NASA / Caltech
CLAUDIA ALEXANDER:
When we see it going around the Sun, a comet will put out a big tail, in fact it puts out two tails...
WHEN COMETS PASS CLOSE TO THE SUN, THE GASES BEGIN TO HEAT UP AND STREAM BACK BEHIND THE NUCLEUS, OR HEAD, OF THE COMET AND FORM A TAIL.
CLAUDIA:
One of the tails is made out of water, and one of the tails is made out of dust. And it goes around the Sun, the tail gets longer and longer, and then as it goes away from the Sun, the tail diminishes until there's no tail at all.
title: METEOR
A METEOR IS WHAT WE CALL AN OBJECT FROM SPACE PASSING THROUGH EARTH'S ATMOSPHERE... BURNING UP FROM FRICTION AS IT GOES.
title: METEORITE
AND A METEORITE, LIKE THESE BEING GATHERED IN ANTARCTICA, IS WHAT WE CALL A CHUNK OF ONE OF THESE OBJECTS WHEN IT FALLS TO EARTH.
MILLIONS OF METEORS BURN UP IN EARTH'S ATMOSPHERE EACH DAY... HUNDREDS OF TONS OF MATTER IN ALL, BUT ONLY A FEW SURVIVE TO HIT THE SURFACE.
chapter head: ASTEROIDS AND THE BIRTH OF THE SOLAR SYSTEM
DOWN HERE ON EARTH, ASTEROIDS ARE JUST POINTS OF LIGHT.
title: Asteroid Toutatis (Radar image)
EVEN WITH POWERFUL RADARS, ALL YOU GET ARE TUMBLING SHAPES, LOOKING MORE LIKE LARGE POTATOES THAN A MINOR PLANET.
name title:
GASPRA
IDA
THE FIRST CLOSE-UP IMAGES OF ASTEROIDS WERE CAPTURED IN 1991 AND 1993 WHEN THE GALILEO SPACECRAFT FLEW PAST GASPRA AND IDA ON ITS WAY TO JUPITER.
name title
DACTYL
GALILEO EVEN FOUND THAT IDA HAD ITS OWN TINY MOON, DACTYL, IN ORBIT ROUND IT...
name title:
NEAR
NEAR EARTH ASTEROID RENDEZVOUS MISSION
narrator:
THIS IS THE NEAR SPACECRAFT... NEAR STANDS FOR THE NEAR EARTH ASTEROID RENDEZVOUS MISSION.
WE KNEW THE "NEAR" SPACECRAFT WAS SOON GOING TO GIVE US REVOLUTIONARY INSIGHTS WHEN IT PASSED WITHIN 1200 KILOMETERS OF ASTEROID 253 MATHILDE...
title: Asteroid EROS
THEN IT WAS ON TO ITS PRIMARY TARGET... EROS.
CHENG:
Eros was picked because it is one of the largest of the Near Earth asteroids. It was the first asteroid that was discovered to cross inside the orbit of Mars. Before that people thought all the asteroids sat calmly between the orbits of Mars and Jupiter.
EVERY DAY DURING THE PRIMARY MISSION, THE "NEAR" TEAM POSTED A PICTURE OF THE DAY ON THE INTERNET.
YOU CAN SEE OBJECTS AS SMALL AS 3 METERS ACROSS.
CHENG:
It just happens the image for August 1st 2000 is a particularly fascinating image, because it shows us peering over the end of the asteroid. And... in fact, the whole asteroid is 32 kilometers from end to end.
The asteroid is like a peanut, and so you're looking at the concave side. You're looking over one end of it, that's down here, right towards the middle, right at the bottom.
It happens that in the middle of the asteroid there is a big crater, the biggest crater on the asteroid. And fascinating things about this image... you can see the boulders that are just perched on the surface.
We wanted to study the asteroids because some of them are among the oldest objects in the solar system. They are remnants of the processes that assembled the planets. So in some sense what we are studying is clues to at least... what happened to Eros at the same time, basically, that the terrestrial planets were forming.
So it is, in that sense, a window back into the period when the solar system was being born.
chapter head: COMETS IN CLOSE UP
CLAUDIA ALEXANDER:
What is a comet?
A comet is sort of a ball of ice, basically, with some rock thrown in there, and besides that, we don't really know. That's one of the reasons why we'd like to go to a comet, visit it, drop a probe down in there and do some exploration, because we don't really know what it's made of.
ASTEROIDS AND COMETS ALL LIVE IN DIFFERENT REGIONS OF OUR SOLAR SYSTEM.
CLAUDIA:
When we look out into space and we're looking for what's out there, what kind of junk might be out there, what kind of stones and boulders and other kinds of planetary bodies are out there, we see asteroids and we see comets.
But mostly we see asteroids close to the Earth. In fact, we see asteroids between Mars and Jupiter. There's an enormous belt, called the "Asteroid Belt", where we see most of the asteroids.
It's almost as it a planet was trying to form there and it couldn't form for some reason, and so all the boulders that we think collapsed together to make a planet in the first place, they never got a chance to collapse together and create a planet right there between Mars and Jupiter.
And further out there's a thing called the "Kuiper belt", and the Kuiper belt is outside of the orbit of Pluto.
It's another belt of rocky, icy, boulders that are kind of like the asteroid belt but there's a lot more ice there.
SOME PEOPLE THINK THAT WHAT WE CALL THE PLANET PLUTO MAY IN FACT BE A LARGE MEMBER OF THE KUIPER BELT OBJECTS.
OTHERS THINK THAT NEPTUNE'S LARGE MOON, TRITON, WHICH ORBITS BACKWARDS ROUND ITS PLANET, MAY BE ANOTHER.
But even farther than the Kuiper belt is a thing called the "Ort Cloud." And the Ort cloud is a big sphere that surrounds the Sun, and that's where the comets come from.
It's a place that's very, very far away and we haven't even seen it with our own eyes yet.
AS MANY AS A TRILLION COMETS MAY SIT OUT THERE IN THE OORT CLOUD, 100,000 TIMES AS FAR AWAY FROM THE SUN AS IS THE EARTH.
BILLIONS MORE ORBIT THE SUN BEYOND THE ORBIT OF PLUTO.
SOME COMETS COME UNDER THE GRAVITATIONAL INFLUENCE OF JUPITER... AND RETURN TO THE INNER SOLAR SYSTEM MORE FREQUENTLY.
THE TAIL OF A COMET ALWAYS POINTS AWAY FROM THE SUN, DRIVEN BACKWARDS BY THE SMALL BUT CONSTANT PRESSURE OF THE SOLAR WIND.
EACH TIME A COMET PASSES THE SUN, IT BURNS OFF MORE OF ITS GASES.
SOME THEN BECOME DEAD ROCKS, RATHER LIKE ASTEROIDS.
SOME FALL DIRECTLY INTO THE SUN.
HERE THE SOHO SPACECRAFT SHOWS US 2 COMETS MAKING THEIR FINAL, FIERY PLUNGE!
HOW THEY COME TO TRAVEL DOWN INTO THE INNER SOLAR SYSTEM, OR CROSS EARTH'S ORBIT, IS THE RESULT OF GRAVITATIONAL INTERACTIONS WITH OUR GIANT PLANETS SUCH AS JUPITER, OR AN EVEN MORE LONG DISTANCE PASSING ENCOUNTER WITH A NEARBY STAR.
FOR CENTURIES, THE APPEARANCE OF A COMET IN THE SKIES WAS AN OMEN OF IMPORTANT EVENTS, OFTEN BAD LUCK FOR THOSE WHO SAW IT.
THIS COMET, LATER CALLED "HALLEY" AFTER THE MATHEMATICIAN WHO FIGURED OUT ITS 76 YEAR ORBIT, APPEARS IN THE BAYEUX TAPESTRY, COMMEMORATING THE NORMAN CONQUEST OF ENGLAND.
OF COURSE, WHILE IT MAY HAVE BEEN BAD LUCK FOR THE ENGLISH... ON THE OTHER HAND THE NORMANS SHOULD HAVE BEEN PRETTY HAPPY!
NEW TECHNOLOGIES HAVE NOW MADE IT POSSIBLE, FOR THE FIRST TIME, TO TRAVEL OUT TO RENDEZVOUS WITH A COMET.
NOW EN ROUTE TO COMET WILD-2 IS THE STARDUST MISSION.
BUILT BY LOCKHEED MARTIN, LAUNCHED IN 1999, AND OPERATED AT THE JET PROPULSION LABORATORY, STARDUST SHOULD GET TO ITS TARGET IN 2004.
THE HEART OF ITS INNOVATIVE DESIGN IS A KIND OF DOUBLE-SIDED PING-PONG PADDLE, LOOKING SOMETHING LIKE A WAFFLE IRON.
BOTH SIDES ARE COATED WITH AN AMAZING MATERIAL CALLED AEROGEL-A SOLID THAT'S MOSTLY AIR CAPTURED IN A SPONGE-LIKE GLASSY FORM.
IT'S IN THE GUINNESS BOOK OF RECORDS AS THE LIGHTEST SOLID. AND IT'S ON THE COMET BECAUSE IT PROVIDES SOME AMAZING CAPABILITIES.
EN ROUTE TO THE COMET, STARDUST HAS ALREADY BEGUN TO STICK ITS PADDLE OUT TO CAPTURE INTERSTELLAR DUST PARTICLES.
AT THE COMET, THE PADDLE WILL COLLECT MATERIAL FROM THE COMET'S TAIL.
THEN, THE SAMPLES WILL BE RETURNED TO EARTH IN AN AIR TIGHT, STERILE CAPSULE TO ENSURE WE'RE LOOKING AT PURE STAR- AND COMET DUST.
IT SHOULD BE WINTER ON THE PLAINS OF UTAH WHEN THE CAPSULE RETURNS.
THEN THE DUST TRAILS IN THE AEROGEL WILL LEAD RESEARCHERS TO PRISTINE COMET PARTICLES NEVER STUDIED IN THIS WAY BEFORE.
name title:
TOM DUXBURY
Project Manager, STARDUST
JPL, NASA / Caltech
This mission puts us on the verge of discovery. We will be the first mission to launch, to go out beyond the Earth-Moon system and capture particles from another planetary body and bring those back to Earth. It's just unbelievably exciting to be part of such a project.
chapter head COSMIC COLLISIONS
THE EXISTENCE OF THE ASTEROID BELT IS PROOF THAT COLLISIONS HAPPEN.
AS WE LOOK OUT AT THE MOON... AND MERCURY... AND MARS, WE CAN ALSO SEE LARGE CRATERS DATING FROM THE EARLY DAYS OF THE SOLAR SYSTEM.
EVEN HERE ON EARTH THERE ARE CRATERS...
name title:
Meteor Crater
THIS IS METEOR CRATER IN ARIZONA...
name title:
Chicxulub Crater
AND THIS IS THE GIANT CRATER OFF THE COAST OF MEXICO THAT SOME THINK IS THE RESULT OF THE IMPACT WHICH LED TO THE EXTINCTION OF THE DINOSAURS.
BUT THE AGE OF COLLISIONS IS NOT DEAD.
title: SHOEMAKER-LEVY 9
IN 1994, CHUNKS OF A COMET NAMED SHOEMAKER-LEVY 9 AFTER ITS DISCOVERERS, SLAMMED INTO JUPITER.
ASTRONOMERS AT THE SPACE TELESCOPE SCIENCE INSTITUTE WERE THRILLED BY THE IMAGES. EACH CHUNK OF COMET LEFT A DARK SPLOTCH IN JUPITER'S CLOUDS.
YOU COULD EVEN SEE THE FIREBALL RISING HIGH OVER THE PLANET'S CLOUDS. IT WAS THE EQUIVALENT OF MANY NUCLEAR BOMB BLASTS.
BUT SOON JUPITER'S VAST STORM SYSTEM COVERED ALL TRACES OF THE IMPACT.
NOW WE KNOW THAT COMETS PASSING ACROSS OUR SKIES HAVE NOTHING TO DO WITH OUR FATE DOWN HERE ON EARTH, THOUGH THEY MAY WELL HAVE HAD SOMETHING TO DO WITH THE ORIGIN OF SOME OF THE WATER ON OUR PLANET... AND PERHAPS EVEN LIFE ITSELF.
CLAUDIA ALEXANDER:
In the very early days of the solar system, of course, there were more comets flying by, we think. The comets that were flying by were also helping to bring water to the planets. So without comets hitting the Earth and bringing all their water, we might not have had the same kind of oceans that we have today.
EROS IS A NEAR EARTH ASTEROID.
THAT MEANS AT SOME POINT IT JUST MIGHT IMPACT EARTH.
ANDY CHENG:
If we do discover an object, an asteroid that is heading for the Earth what you would want to do is deflect it, push it a little bit, so it does not hit the Earth.
IT TURNS OUT THAT KNOWING THE COMPOSITION AND HISTORY OF SUCH NEAR EARTH ASTEROIDS MAY BE KEY TO THE KIND OF PROTECTIVE MEASURES HUMANS MAY BE ABLE TO ADOPT IN THE FUTURE.
CHENG:
If we set off a bomb and we push it somewhere in the middle, let's say, and it breaks up into five large pieces, all of which still hit the Earth, that outcome would actually create more damage, probably, than just leaving the asteroid alone.
So what we have to understand is whether we are looking at a very loose jumble of rocks, that are not very well stuck together, as opposed to a single relatively consolidated object which we could push fairly hard and it would relatively easy to deflect.
ASTEROIDS AND COMETS MAY BE SOME OF THE SMALLEST OBJECTS IN OUR SOLAR SYSTEM, BUT AS WE UNDERSTAND THEM MORE WE MAY DISCOVER HOW OUR HOME PLANET BEGAN.
AND IF WE RECOGNIZE THAT COLLISIONS AND IMPACTS ARE AS MUCH A PART OF LIFE IN OUR SOLAR SYSTEM AS REGULAR ORBITS AND ROUTINE SEASONS, WE MAY TAKE PRECAUTIONS TO ENSURE OUR SPECIES AVOIDS THE FATE OF THE DINOSAURS.
IT MAY BE THAT WHAT WE DISCOVER ABOUT THE COMPOSITION OF COMETS AND SPACE ROCKS IS JUST WHAT WE NEED TO KNOW TO DIVERT THEM AWAY FROM EARTH.
IT'S HARD TO THINK OF SCIENTIFIC KNOWLEDGE THAT'S ANY MORE VALUABLE THAN THAT...
