Energy, Systems and Surprises
THE OUTER SOLAR SYSTEM IS A VERY DIFFERENT PLACE FROM WHERE WE LIVE... ON THE 3RD ROCKY PLANET FROM THE SUN.
OUT HERE JUPITER-LARGE ENOUGH TO HOLD THIRTEEN HUNDRED EARTH'S-IS RULER.
NEXT PLANET OUT, SATURN WITH ITS MAGNIFICENT RINGS...
BEYOND SATURN, URANUS AND SEA-BLUE NEPTUNE...
chapter head: FLYING BY THE GAS GIANTS
IN THIS VIDEO, WHAT WE DISCOVERED IN OUR FIRST FLY-BYS OF THE GAS GIANT PLANETS...
chapter head: THE JUPITER SYSTEM
...THE ENERGETIC PROCESSES WHICH BRING THE ICE MOONS OF THE JUPITER SYSTEM TO LIFE...
chapter head: DISCOVERY MACHINES
...AND WHAT WE CAN LOOK FORWARD TO WHEN WE REPEAT THE PROCESS OF DISCOVERY AT SATURN!
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TITLES
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TORRENCE JOHNSON IS PROJECT SCIENTIST FOR THE GALILEO MISSION TO JUPITER AND ITS MOONS, AND HAS ALSO WORKED ON THE VOYAGER MISSION TO THE GIANT PLANETS.
OUT HERE, THE PLANETS AREN'T JUST BIGGER, THEY'RE MADE OF DIFFERENT STUFF-GASES AND ICE, NOT ROCK AND IRON.
name title:
TORRENCE JOHNSON
Project Scientist, Galileo, JPL, NASA / Caltech
Until you got beyond the asteroid belt the temperatures weren't low enough to allow the condensation of the more volatile materials. Once you got to the point where you could condense water, wow, you get another big admixture of mass immediately.
So a typical body that condenses just after you get to the point where you can have, uh, frozen water is a body that's about twice as massive as one you've got just inside the water line.
In addition to that you've got all this extra gas and dust floating around. And the larger planets started, when they started forming, they grabbed even more of this, and they've got enough gravity that they can grab onto all this material out there, including the gases hydrogen and helium. And so you get these massive gassy bodies with icy worlds around them
chapter head: FLYING BY THE GIANT PLANETS
JUPITER AND ITS MOONS WERE AMONG THE OBJECTS SEEN BY THE ITALIAN ASTRONOMER, GALILEO GALILEI, SOON AFTER HE TURNED ONE OF THE FIRST TELESCOPES TO THE HEAVENS IN 1609.
WE GOT OUR FIRST >CLOSE UPS< OF JUPITER AND SATURN WHEN THE "PIONEER" SPACECRAFT SPED BY IN THE 1970'S.
AT THE END OF THE DECADE, THE TWO "VOYAGER" SPACECRAFT FOLLOWED, AND RETURNED SPECTACULAR IMAGES.
JUPITER, SECOND LARGEST OBJECT IN OUR SOLAR SYSTEM AFTER THE SUN, HAS NO SOLID SURFACE.
MADE LARGELY OF THE GASES HYDROGEN AND HELIUM, WE THINK IT HAS A >ROCKY CORE< SURROUNDED BY >LIQUID, METALLIC HYDROGEN.<
THE VOYAGERS SHOWED US CLOUDS IN DETAILED TURBULENT MOTION, INCLUDING TIMELAPSE MOVIES OF THE "GREAT RED SPOT," WHICH HAD FIRST BEEN SEEN MORE THAN 300 YEARS BEFORE...
TORRENCE JOHNSON:
The Great Red Spot is a massive storm system in the Jupiter atmosphere. And it probably has a structure very similar to a hurricane in general, which is that it probably has a rising column of atmosphere in the center of it with sort of a spreading out layer on top of that.
LOOKING BACK ON THE DARK SIDE OF THE PLANET, WE SAW LIGHTNING FLASH DEEP DOWN IN THE CLOUDS.
ASTRONOMERS ASSUMED THERE MUST BE THUNDERSTORMS AND WATER VAPOR IN TURBULENT UPWARD MOTION, JUST LIKE DOWN HERE ON EARTH.
AT ITS CORE, JUPITER IS 20,000 DEGREES KELVIN.
LIKE SATURN, IT GENERATES MORE HEAT FROM INTERNAL SOURCES THAN IT RECEIVES FROM THE SUN.
VOYAGER DISCOVERED VOLCANOES ON JUPITER'S MOON IO, MAKING IT ONE OF ONLY 4 VOLCANICALLY-ACTIVE BODIES IN THE SOLAR SYSTEM.
STAINED YELLOW AND RED WITH SULPHUR, IO WAS INEVITABLY COMPARED TO PIZZA!
BUT ALL 4 GALILEAN SATELLITES-IO, EUROPA, GANYMEDE AND CALLISTO-PROVIDED HINTS OF UNUSUAL PROCESSES AT WORK...
AND VOYAGER DISCOVERED THAT JUPITER, LIKE SATURN, ALSO HAS RINGS.
SATURN'S STORMS MAY BE SMALLER THAN JUPITER'S, AND ITS CORE TEMPERATURES COOLER, BUT ITS RINGS FAR SURPASS JUPITER'S IN SIZE AND SPLENDOR.
THEY'RE A QUARTER OF A MILLION KILOMETERS WIDE, BUT ONLY ONE AND A HALF KILOMETERS THICK. THEY'RE MADE OF WATER ICE AND ICE-COVERED ROCK, AND MAY BE THE REMAINS OF MOONS OR ASTEROIDS TORN TO PIECES BY SATURN'S GRAVITY.
VOYAGER FLEW BY SATURN'S LARGE MOON TITAN, WHOSE NITROGEN AND METHANE ATMOSPHERE IS TINGED REDDISH-BROWN BY ORGANIC COMPOUNDS/MOLECULES...
FOR VOYAGER THIS SMOG OBSCURED THE OCEANS SOME THINK MAY LIE BELOW.
VOYAGER 2 USED SATURN'S GRAVITY TO SLINGSHOT IT ON TO URANUS, A PLANET THAT'S MOSTLY WATER, AMMONIA AND METHANE.
TWICE EACH ORBIT, THIS PLANET'S POLE POINTS T'WARDS THE SUN, WHICH MAY BE THE RESULT OF SOME VAST COSMIC COLLISION IN THE PAST.
URANUS'S LARGE MOON MIRANDA IS NAMED AFTER ONE OF SHAKESPEARE'S CHARACTERS, BUT AS THIS SIMULATED FLY-BY, INDICATES, IT TOO SHOWS THE SCARS OF A VERY "NON-POETIC" PAST!
THEN ON TO NEPTUNE AND ANOTHER INDICATION THAT MANY PHENOMENA IN THE OUTER SOLAR SYSTEM ARE NOWHERE NEAR AS STABLE AS JUPITER'S GREAT RED SPOT, OR SATURN'S RINGS.
Name title:
HEIDI HAMMEL
Space Science Institute, Boulder, CO
One of the biggest surprises when the Voyager spacecraft flew past Neptune was a huge dark spot on the planet, and we called it the Great Dark Spot.
When we looked with the Hubble Space Telescope, that Great Dark Spot was gone. It had simply disappeared, it wasn't there any more, and that was a big surprise.
THEN, LIKE THE PIONEERS, THE VOYAGERS LEFT THE PLANETS OF OUR SOLAR SYSTEM BEHIND, AND EVEN TODAY ARE SPEEDING ONWARDS TOWARD THE STARS.
chapter head: THE JUPITER SYSTEM
THEY NAMED IT "GALILEO," AFTER THE DISCOVERER OF JUPITER'S MOONS.
LAUNCHED FROM THE SHUTTLE IN 1989, GALILEO ARRIVED AT JUPITER IN 1995.
IT MADE LOOPING TRAJECTORIES AROUND THE PLANET AND ITS MOONS, AND DOCUMENTED PREVIOUSLY UNKNOWN PROCESSES.
SIX MONTHS BEFORE GALILEO ARRIVED, THE FIRST PROBE EVER SENT BY HUMANS INTO THE ATMOSPHERE OF A GAS GIANT, SEPARATED... AND LATER, RIGHT ON SCHEDULE, PLUNGED DOWN INTO THE CLOUDS.
IT TURNED OUT TO BE A REGION MUCH DRIER THAN THE RESEARCHERS EXPECTED AFTER ALL THOSE MASSIVE THUNDERSTORMS SEEN BY VOYAGER.
TO TORRENCE JOHNSON THAT JUST MADE JUPITER ALL THE MORE INTERESTING!
TORRENCE JOHNSON:
What we have found...by comparing the probe data with the data from the instruments on the orbiter, is that Jupiter has tremendous variations in its humidity, much as the Earth does, of course, between things like the Sahara desert and tropical rainforests.
There are other areas on Jupiter that are much wetter and on average we now think that Jupiter has a lot of water, it just wasn't in the place where the probe went in.
So we now believe in fact that in an interesting respect, Jupiter's atmosphere actually is engaging in some of the same exchanges of energy that the Earth's atmosphere does through what's called "moist convection", that is, the evaporation of water and the condensation of water.
What's different at Jupiter is that the energy for all this is not mostly coming from the Sun evaporating the oceans as it does on the Earth but from Jupiter's internal energy source, which is a result of its early, very, very energetic history when it collapsed from a ball of gas and dust, became very, very hot, almost star-like in fact...
ALL THAT ENERGY, PLUS JUPITER'S VAST GRAVITATIONAL PUSHES AND PULLS MAKE THE MOONS COME TO LIFE IN SPECTACULAR WAYS.
IO HAS MORE THAN 300 VOLCANOES, SOME WITH LAVA FOUNTAINS SPOUTING MORE THAN A MILE ABOVE THE SURFACE.
ON EARTH THEY REACH A FEW HUNDRED METERS AT MOST.
TORRENCE JOHNSON:
What we've been able to do with the Galileo space craft is go back and basically be a volcano observatory, watching the surface of this strange moon change literally before our eyes.
SECOND MOON OUT FROM JUPITER, ICY EUROPA, WHICH WE ALREADY KNEW HAD SOME STRANGE CRACKED PATTERNS FROM THE VOYAGER IMAGES...
TORRENCE:
We got close with Galileo what we saw was many of these cracks or ridges running across the surface and there are huge areas on Europa's surface where the surface apparently has been melted and things very much like ice rafts or icebergs have broken off from the edges of other parts of the icy crust ...moved and rotated.
name title:
CLAUDIA ALEXANDER
GALILEO Science Team, JPL, NASA / Caltech
The pictures that they did get were, like, oh, well there's a lot fewer craters than we thought. This is a surprise, the surface must be younger than the three and a half billion years that we thought.
And then the next orbit they went by they took more pictures, and it's like, oh well, gee, it's a lot younger than we thought, maybe, maybe it's even one billion year old.
But the age dropped with every pass that we went by, the age of Europa began to get younger and younger, until the investigators were talking about maybe it's presently active, and maybe we should be targeting to try to catch one of these geysers suddenly open up and we could fly by and see the water coming out right presently.
TORRENCE:
Putting all that data together makes a very strong case for there being a liquid ocean some 100 kilometers or 60 miles deep underneath that ice crust on Europa. That's a very exciting prospect.
One of our big surprises with Ganymede came from the measurements from the magnetometer, which measures magnetic fields. We detected that Ganymede has its own magnetic field. It isn't just affecting the Jupiter field, but it has its own field, a sort of a bar magnet stuck inside it, deep inside...
CLAUDIA:
For it to have a magnetosphere it can't be frozen solid because what has to happen is that inside there has to be motions, turning over. Uh, we've never seen an icy moon with a magnetosphere; in fact, we've never seen any moon with a magnetosphere.
THE EXPLANATION FOR ALL THESE SURPRISING PHENOMENA SEEMS TO BE THAT OUR SOLAR SYSTEM HAS OTHER WAYS OF HEATING WORLDS, POWERING VOLCANOES, CREATING LIQUID WATER... AND, JUST MAYBE, ENABLING LIFE TO BEGIN THAN WITH SUNLIGHT ON THE SURFACE OF A PLANET.
TORRENCE JOHNSON:
These objects are being distorted by the tremendous gravitational forces of this big planet Jupiter that they're orbiting. And as they move around Jupiter they get a little closer to Jupiter at some point and they were a bit further away from Jupiter at other points in the orbit. And so their crusts and their interiors are continually being flexed and pushed in and out. That creates friction inside the body and that creates heat. And that's one of the things that's producing this immense amount of volcanic activity on Io.
When you go to Europa there's less of this pushing and pulling going on because Europa is a little further away from Jupiter than Io is. But that's still probably enough to heat up the icy crust and the interior rock below and probably is one of the major players in keeping a liquid layer ocean liquid on Europa.
AS WE'LL SEE, SENDING AN ORBITER TO EUROPA, AND FIGURING OUT HOW TO SEND A ROBOT DOWN INTO THAT ICY OCEAN IS ONE POSSIBLE FUTURE MISSION UNDER CONSIDERATION.
chapter head: DISCOVERY MACHINES
LONG BEFORE THAT THE RELATIVELY LARGE AND CAPABLE "CASSINI" SPACECRAFT, SEEN HERE UNDER CONSTRUCTION AT JPL, SHOULD ARRIVE AT SATURN.
CASSINI WILL GO INTO ORBIT AROUND THE SECOND-LARGEST PLANET IN OUR SOLAR SYSTEM, AND RETURN AN ARRAY OF IMAGES.
LIKE GALILEO, IT WILL CARRY A PROBE, NAMED AFTER CHRISTIAN HUYGENS, WHO FIRST SKETCHED THE TRUE SHAPE OF SATURN'S RINGS.
THE HUYGENS PROBE IS TARGETED AT TITAN-THE MOON WITH CLOUDS OF BROWN, ORGANIC SMOG...
TORRENCE:
The surface of Titan is a total mystery. We know that there are features on the surface, but we don't know what those features are. So I think almost no matter what we find, when we get pictures of Titan's surface, radar images of Titan's surface and data from the Huygens' descent probe as it goes down through the Titan atmosphere and looks at the surface, those are going to be tremendously fascinating pictures.
Will we find craters there, will we find no craters, lakes of hydrocarbons, no lakes of hydrocarbons? I think that's going to be one area where Cassini can't fail to surprise us.
PERHAPS THE GAS GIANTS AND THEIR ALIEN MOONS SEEM-WELL, "ALIEN," FAR AWAY, UNCONNECTED TO EARTH.
BUT UNDERSTANDING HOW THEY WORK, AND THEIR STRANGE WEATHER PATTERNS, JUST MAY PRODUCE SOME FUNDAMENTAL INSIGHTS INTO THE WAY OUR HOME PLANET BEHAVES.
name title:
HEIDI HAMMEL:
One thing that we all care about is the weather. And we care about the weather on the Earth the most. But what makes weather is gases and clouds. And the reason the weather on the Earth is hard to predict is because we have oceans and continents that interact with our atmosphere. That makes it very hard to predict the weather, as we all know.
But if you take a planet like Jupiter or Neptune, you don't have continents and you don't have oceans, all you have is gas, all you have is atmosphere. And therefore it's a lot easier to model the weather on those planets. But it's the same physical process. It's the same kind of thing happening whether it happens on the Earth or Neptune.
Therefore by studying weather on Neptune we learn about weather in general, and that helps us understand the weather on Earth better.
SEEING PLANETARY PROCESSES PLAYED OUT ON THE LARGE SCREEN OF THESE GIANT WORLDS, WE MAY RECOGNIZE SOME LAWS OF NATURE FOR THE FIRST TIME.
